Showing posts with label Chuck's Tech Opinion. Show all posts
Showing posts with label Chuck's Tech Opinion. Show all posts

Thursday, 1 April 2021

Chuck's Tech Opinion: How to decide what to keep and what to change on a Raleigh Twenty, and Pedals!

As you work on a Twenty, you start to get a feel of the engineering. I find it useful to categorise: some parts are really well thought out and function well, others are merely adequate for their job and there's another category of redundant, useless, or poorly designed stuff. Then layered over that, some parts have elegance, possibly even beauty, while others are downright ugly. Add yet a further layer, namely weight, and a recipe emerges as to how to go about deciding what to keep and what to change. 

Take the pedals. In the photo below (starting top left and going anti-clockwise): originals off a BSA 20, modern MTB style polymer flatties (BBB brand) and a generic polymer trap-type pedal:


Both the modern pedals have reflectors, today a legal requirement for safety, whereas the R20 pedals do not. Now, this R20 pedal has a certain elegance, it's true, but it's also narrow. Uncomfortable over a length of time, especially in soft soled shoes, as your feet curl over it. The weights add another factor:

Pedal type g per pair
R20 651
MTB Flatties 336
Polymer Cage      286

I think it's remarkable that the old R20 pedals weigh so much, nearly 1.5lb! I discarded the polymer cage, for two reasons: the bearings on one were notchy and I didn't like the style for this bike. I thought it would be funky to have the MTB flatties. Apart from the beautiful wide platform they provide, the reflectors for safety and the weight saving (a stonking 315g), they are also shorter (12.1 cm v 11.0 cm from crank to pedal tip) and thinner, both of which reduce the chance of a pedal touching the road in a corner. So, my choice is made to switch to the MTB Flatties. 

That all sounds great, but then I tried fitting the MTB Flatties and to my surprise while the diameters were comparable (9/16"), the threading was different! I wondered whether the cranks had some old English threading, but that seems like an odd explanation, because I've managed to get modern pedals on a R20 before and know that others have too. More likely, perhaps the threading tooling that Raleigh used was slightly different to modern standard. It could be just some R20s that were like this. I tried a few pedals and I found that most of them were too tight, but one or two modern pedals went in ok, but only on one crank. Whatever the reason, after playing about a bit with modern pedals, I now feel that for this project, I will stick with the original pedals. They are a basic, but serviceable design. The end cap prises off carefully with a thin screwdriver. Underneath, two spring clips and a washer to remove:


There are no BBs just a plain bearing. The axle at the top simply slides into what looks like a tapered sleeve in the pedal, then the washer with flats is added and the two spring clips to hold it all down. This one was gummed up and a quick clean and regrease worked wonders. They spin super smoothly now. At least they are hardly worn and have plenty of service to give. They'll clean up ok and add to the retro look. 

Now consider the light bracket:


What an ugly lump that is, and given modern lights, it's redundant too. It serves a purpose in the headset, that is to increase stack height by a few mm in order to prevent the top lock nut from bottoming out. But that function can be easily achieved with a small standard spacer. How much does this monstrosity weigh? 77g! That's about the weight of SEVEN AAA batteries! Wowsers. Guess where that's going? Yes, in the recycling bin. NB, you have to remove the front brake caliper to get the stem out in order to lift this off the headset (see my post a few days ago on that wire loop thingy that restricts the movement of the stem vertically).

Note that by just by changing pedals and ditching the light bracket, you could save nearly 400g. Astonishing. 

You can repeat this thought process for every other item on the R20, using the factors I suggested at the top of this post (I'm not considering maintenance items, such as brake pads, tyres, BBs, chain and cables):

Sturmey Archer hubs (both the front one and the rear epicyclic AW gear unit): 
Elegant, well thought out, very functional, design kudos, unique, a bit heavy, but worth it! Pretty when clean and polished! I would keep these in nearly every case, unless there was a radically different vision for a particular build. 

Chainset: 
They are not all the same. Some patterns are indeed beautiful, others look more functional, but they have some eye appeal, I like the stamped "Nottingham Knight". They function well if you can deal with cotter pins and can live with the heavy chromed steel.

Bottom bracket:
It's perfectly functional, and isn't heavy, so in my view, this comes down to condition, and how important it is for you to change the chainset/eliminate cotter pins. The axle is a solid thing, and very rarely needs replacement. So, a good service with new BBs is usually all that's needed if you stick with cottered cranks. However, if you want to open up the world of square taper chainsets, then I believe that the simplest and best option is to find a square taper axle that fits and retain the same bottom bracket cups and 1/4" BBs. If that's not possible, then face the shell to 73mm or even 68mm (the width of my BSA 20 shell is 77mm as best as I could measure it), and rethread to standard 24 tpi. Some say that you should fill the threads with with a suitable molten metal before re-threading, but I've also read that many people have had success just rethreading directly, but slightly deeper than the original threads. Clearly a specialist's job. Failing any of those, then a problem solver may be a new threadless (friction fitting) unit. 

Saddle:
Really ugly, uncomfortable for me, and enormously heavy! It's gotta go. 

Seatpost:
Ugly, too short for many people, and very heavy, especially being steel with the steel clamp. Easy swap out to a modern one 28.6 usually. It's gotta go. 

Chrome steel Handlebars and Stem
Function ok, and have a certain elegance. However, they are really rather heavy and often this is were customisation and your personal vision take over. A quill stem, with alloy riser bars, or bullhorns, etc. 

Hand grips:
Yeuk! Hard ugly plastic and short. The only positive thing I can say about them is that they are hard wearing. But, I really think they have to go in just about any project (save for a restoration to original spec). 

Chrome steel rims:
Work ok, but do not brake as well as alloys, especially in the wet. Look nice when clean and polished up. Heavy! My front wheel without nuts, rim tapes, or tyres weighs 940g. With rim tapes, tyres and nuts it weighs 1547g. Go or stay? It's really one of preference and also considering the condition of the steel rims that you have, the hassle of doing a rim swap, or finding/building another wheel that fits and also brakes that work with them. On the other hand, if you're not accelerating and braking a lot then, a heavy wheel provides a nice flywheel effect for steady riding - which is what I tend to do on a Twenty. 

Nylon bushing top part of the headset: 
Functions just about adequately, especially if you get a chance to clean it and lube the surface that touches the steerer, and adjust the headset properly. Once the light bracket is off, there's not much in the weight. So this one is a matter of preference again. This photo is of my current project, rust cleaned off and polished. I've kept the Nylon bushing, but ditched the light bracket (hence the black spacer):


Another approach is to remove the Nylon bushing and install the top half of a 1" threadless headset. When I do that again in the future, I'll be sure to take enough photos and post them on this blog. 

Frame: 
It wouldn't be a Twenty without one! It's a classic, has got to stay.

Forks:
They are designed to fit the cone flanges of the Raleigh Sturmey Archer front hub and they work well enough. A bit heavy. I think this one is mainly down to whether you keep that front hub or not. Also whether you want to do something funky, like BMX forks for 451 or 406 wheels or suspension forks. In which case, you can also change the whole headset. 

Paintwork:
What condition is it in, and do you like it? Will it clean up nicely (after a wash, T-Cut and car polish)? Simple as that. 

Clamps and Locking levers on steerer and seat tube:
These function adequately if well-maintained and positioned properly (evenly over their respective tubing slots). They add a bit of weight, but also provide easy quick adjustment. Also, if you are fitting a quill stem, the front clamp becomes unnecessary and can go (or stay!). So it's really up to you. 

Brake caliper units:
Can function adequately if you take the time to set them up well, and they polish up ok too. Remove rust with WD40 and 0000 steel wool, chrome polish, lubricate and fix and adjust them properly. Use fresh cables. In many instances, I've changed only the inner wires, as the outer cables were fine. If the ends of the outer cables are kinked, you can snip off 5-10mm cleanly and that will improve the performance quite a bit. Modern alloy units would be an improvement and weigh less, but I think this one is really a matter of preference.  Here's a front caliper, with rust cleaned off one arm, but not yet the other one:



Brake levers:
In my view they function adequately, and being steel are better than plastic levers! But there are lighter and better modern alternatives. So, it's a matter of preference for your particular build I think. 

Mudguards (Fenders):
Functional, but do not have the break-off arms for safety as modern ones do and are relatively heavy. Must mount them properly and securely, or those beefy mounting arms could foul a wheel and cause a bad accident. I'm powder coating mine on this build.  

Chainguard:
Serves a function (keeping your trouser leg clean!) and has a certain appearance. Don't weigh a great deal, but grams are grams. It's up to you! I'm powder coating mine on this build.  

As I've said before, the Raleigh Twenty is like a blank canvas to a bike builder! The Raleigh bronze green BSA 20 that I'm working on at the moment is going to retain most of its original components, but with modern contact points (pedals, saddle/seatpost and hand grips). The next one may be a light weight with funky bars and alloy rims, but I haven't clearly figured out my direction on that one at this time.  

Go with your heart and desire, enjoy the process, and all will be ok. Be creative, be artistic! 

Wednesday, 31 March 2021

Chuck's Tech Opinion: Shimano Uniglide cassettes, replacing cogs/sprockets

Just before Shimano came up with the Hyperglide (HG) cassette system that we know and love today, it introduced the Uniglide (UG) arrangement. It was an 1980s effort to provide not only a cassette system, but also teeth features to improve shifting (especially for the indexing 'click' that is pretty much standard now). I happen to have such a cassette in 6 speed - they were produced in 5, 6, 7 and 8 speed. Generally, UG cassettes are rare these days, while screw-on freewheel types remain relatively abundant. This post is about cleaning and re-jigging my Uniglide cassette, currently 13-14-15-17-19-21T, and my thoughts about it. I want to dismantle, clean and swap out one of the cogs to allow me to put in a bigger 24T. Photo before I started work:

Yes, it's dirty, and the grime is stuck hard! If you've never seen a Uniglide cassette before, then it could be confusing. It has neither Hyperglide's splined lockring nor the spline socket that screw-on freewheel types have. It does have a freehub body, much like the modern Hyperglide, but all the splines are the same width. Instead of the HG lockring, the topmost cog is screwed down on to the upper part of the freehub body, which is partially threaded, to hold everything together. The 24T cog that I want to add is the black one in the photo. To dismantle, you use 2 chain whips to hold the wider cog, while unscrewing the topmost cog (13T):


Thankfully it unscrewed fairly easily. Turned over, you can see the cutouts for weight reduction and the three small bolts that hold the unit together. The top locking cog (13T) has an inbuilt spacer and is threaded on its inside. 


View from the other side, there is a thin washer under the top locking cog (13T), and you can see the bolts engaged in the three small threaded holes in cog 14T:


The bolts need to come out. The bolts have a smooth shaft and are threaded at their tip. They screw only into the matching threaded holes in the 14T cog: 


Taking off the 14T cog, there are identical plastic spacers between the remaining cogs:


I cleaned up the parts and started to refit. In this photo you can see the threading on the upper part of the freehub body. Apparently, it's possible to change that body for a HG one, but why bother when this seems little worn and is functioning beautifully. Also, I think the threading on Dura Ace is different - presumably an attempt to keep it "exclusive" and apart from the mass market! I've placed the new 24T on first, then a plastic spacer:


Looking at the splines on 19T, note the absence of the wider notch and narrower notch. Also note the three holes for the bolts - these are present in everything, spacers, washer and cogs. I'm not going to use the bolts as their main purpose is to hold the cassette together for easy fitting. 


In the photo above, you can see two teeth features designed to improve shifting. Firstly, two opposing teeth on the 17T cog are shorter. These provide avenues for the chain to dismount as you shift. Secondly, you can just see the twist of all teeth. These features are the precursor of Hyperglide teeth shaping. Place cog, spacer, cog spacer, etc... until you reach the penultimate one, then the thin washer goes on:


Now you can clearly see the threading on the freehub body to take the last locking cog 13T. Put that last one on carefully by hand, to ensure threads are not crossed! Then tighten it with a chain whip, but it's not really necessary to strain yourself doing that, because the process of pedalling will tighten it. In fact, when I put it into top gear while riding, I felt the slight slip as it tightened into position. Here's a pic of the removed bolts and 14T cog, which I'll be putting away carefully in my bits box. Only some cogs had the shorter opposing teeth pairs:


The finished cassette. Not so dirty now! Can you spot the shorter teeth in the picture below? Hint: there are none in the top locking cog (13T). Notice that the 24T cog has them, which means it's not really intended to be a last cog - contrast with 21T (see photo above) which is stamped 'Low' and doesn't have the shorter teeth. I don't think it really matters, and presumably, having the shorter teeth on the biggest cog will help switching from 24T to 21T.  


Now a photo of the bike in which this wheel goes, my Dawes Impulse (see previous posts): 


And a closeup of the cleaned cassette newly configured to: 13-15-17-19-21-24T, with the vintage super-cool Shimano 105 mech:


One thing you need to check for is that the chain is long enough to handle cross-chained big-big. Even if you're not supposed to use that gear, it is wise to ensure that the chain is long enough for it to be engaged otherwise you can break things. To my relief, it was long enough.  

CHUCK'S TECH OPINION ON UNIGLIDE

I thoroughly enjoyed working on my Uniglide cassette, because the quality of manufacture is superb, and everything disassembles and fits well. It was easy to remove the bolts (using quality pliers). This is better than those annoying rivets in modern cassettes, but I can understand that rivets would be much cheaper than those three bolts when it comes to mass production. 

Test riding was magic! It shifted positively, flawlessly, and the indexing was spot on. Definitely the crispest shifting bike with down tube levers that I've ever owned and I'm comparing here to both screw-on freewheels and even more modern 9 speed Hyperglide hubs. (Perhaps that's because the tolerances, both cog-spacing and lever-indexing, for 6 speed are more forgiving compared to the narrower 9 speed?). 

Another great advantage is that the uniform spline widths allow you to invert each cog. Useful to maximise working life, as worn cogs may be simply turned around. While I like this and it resonates with today's re-use, up-cycle culture, it is not the ideal situation for the capitalist mass-producer who wants sales (think Apple iPhones and OS upgrades that render one's device slow). I think that is part of the reason why we have modern riveted cassettes and non-reversible cogs today.  Also, I suspect that with different width spacers, you may use the same freehub body to build up a 5, 7 or 8 speed cassette, but I haven't tried it and would have to research the standards for that (i.e. spacer widths, cog thicknesses and overall hub body height).  

In its time in the 1980s, Uniglide was top-end and a step-forward in smoothness of shifting and ease of indexation. I can appreciate why. Uniglide hubs are ultra-rare nowadays, so the information in this post is really for bike nuts, the sake of history, or those who accidentally come across one. Feel lucky if you do though because from what I've seen, a new old stock Uniglide cassette can sell for £60-£100!

Friday, 27 July 2018

Chuck's Tech Opinion: Bicycle pumps, pressure gauges: Can you trust their measurement?

Can you believe in the pressure measurement of your pump or tyre pressure gauge? Here are a couple of handy gauges: Schwalbe digital gauge on the left and an analogue AccuGage on the right:


Digital Schwalbe: 35g
Analogue AccuGage: 86g
Many pumps, both big and small, have gauges these days. L to R in the photo below: Lezyne Floor Drive (steel), Topeak Joe Blow Sport and Topeak Turbo Morph G: 

So, with these pumps and gauges, I decided to gather some data to see what I could find out. Using a large volume presta valve MTB tyre (Maxxis Ardent), a Challenge Grifo cyclocross tyre, and a Continental Ultra Sport road tyre, I set various pressures using the Joe Blow Sport. I chose that one simply because it was new and the gauge nice and clear: 

The protocol was to set a pressure with this pump, and then with the other pumps and gauges to check what reading they gave. So the Joe Blow acted as the reference value. Of course, we don't know which of these gauges gives the best absolute measurement. 

Absolute means closest to the actual correct standard unit measurement. Contrast with precision, which is about how repeatable a measurement is. 

Here is a close up of the gauge on the small Morph: 

I didn't expect the small dial to allow precision in measurement. And finally, the Lezyne dial, which has a crack in it: 
The clear issue here is what looks like a zero error. With no tyre attached to the pump, it reads about 20psi. (I could not find a way to zero its gauge). I did my best to minimise air escape while switching between gauges. 

OK, with that description, here are the results in a graph (units on each axis are psi):

The x=y line is the Joe Blow "reference" value. You can see that the AccuGage ('+') and the Schwalbe digital ('solid dots') followed that line very well up to about 50psi. For higher pressures, the Schwalbe still followed that line well, but the AccuGage fell a bit below it (~5psi at 80psi). Remember, we've just randomly selected the Joe Blow to act as the reference. The Morph ('open circles') seems to be reading generally 5psi higher than Joe Blow reference and the two stand alone gauges. Most obviously, the Lezyne ('x') reads consistently ~20psi higher than the Joe Blow, AccuGage and Scwhalbe. 

The other thing that came out during this test is that ease of use is a big deal. The Lezyne and the Joe Blow are the easiest pumps to use. The Morph is rather awkward in comparison, and reading the dial is not easy. Both of the stand alone gauges require a bit of practice to use efficiently. With the knurled nut of the Presta valve slightly open, you push the gauge down over the valve and the instrument measures and holds the reading. Out of the two, the AccuGage was much nicer to use because it was easier to slide over the knurled nut of the valve. This seems to be down to its external shape and the size of the opening. The needle stays where it is until you press the very convenient air release button. No batteries, no switching on or off. The Schwalbe has a smaller hole, so tends to contact the knurled nut on a Presta valve more and allow air to escape. Also, the oval shape doesn't give the hands as much purchase on the tool. Perfectly functional, but compared to the AccuGage it was a little irritating during use. On the other hand, the digital gauge is lighter and fits better in a jersey pocket.

It seems reasonable to conclude that because three gauges were pretty consistent with each other (Joe Blow, AccuGage analogue and Schwalbe digital) that these are the closest to measuring the absolute pressure value. That conclusion is consistent with the Lezyne simply suffering a +20psi zero error.

I will continue to use the Lezyne, despite what appears to be its lack of absolute accuracy. All I need to remember is that it reads 20psi high consistently across the usual tyre pressure ranges. This is purely a systematic error. The Morph gauge reads about 5psi high, but its dial has poor resolution anyway. Its utility is in its portability and the fact that for its small size, it can pump up pretty hard. For off road and remote use (e.g. with a pocket pump), the stand alone gauges would get the nod. I'd use the Schwalbe when I need to be able to differentiate between 1 or 2 psi (cyclocross) or if I need to carry a gauge in my pocket. That said, the ease of use of the AccuGage is a big attractor. 

Yes, you can trust your pressure gauge measurement, BUT only if you really understand what it's telling you!

Friday, 4 July 2014

Giant Defy Mudguards or "Fenders", Review

Giant's hugely popular Defy range of road bikes have mudguard eyelets front and rear. However, clearance under the brake calipers is tight. Giant produce mudguards (finders in English(US)) for the Defy, Avail, Rapid and Dash frames. However, I've heard people, even shop mechanics, say that these don't fit on a Large Defy frame. This post is about my attempt to fit them and I'll give my opinion at the end.  
Those are stainless steel braces that go round the brake caliper area. They are 700c x 35mm. My Large size Defy 4 has 700x25mm tyres. The frame does not have a chainstay bridge, but it does have a hole in the seat tube (behind the bottle mount area) to mount a mudguard. However, the slot in the forward portion of the rear mudguard (at right in the photo above) does not reach this hole. So, the first thing is to test fit it in position, mark the position for a new hole and drill it like this:
Then I put some electrical tape over the slot (no need to allow the muck through!):
That's the only modification required. The whole gubbins then attaches as normal, which is totally straightforward. I decided to use a rubber washer on the inside (made of inner tube) to prevent cracking the plastic as I tightened the bolt and to help with vibration:
From the other side, here is the rubber bung (grommet) that the bolt goes through before tightening into the seat tube hole:
Very sensible design. Here is the rear mudguard all fitted. It's very easy to line up and keep off the tyre:

The front guard posed no issues at all. Here's the bike with the mudguards fitted. I think the "fenders" look quite neat:
All in all, they look and feel like good quality items and there seems to be nothing on them that rusts. They are very low profile and coverage is better than SKS Raceblades. The Giant mudguards seem more sturdy than Crud Road Racer Mark 2's, maintain clearance from the tyres very nicely, and they don't have any brushy things, as on the Crud's, to contact the rims. However, they have traditional wire mounting rods, unlike the Cruds or SKS which have break off parts for safety. They provide a great solution to turn your road bike into a commuter or winter bike. It is possible that they would fit other road bikes too, but you'd need some kind of mod to attach the rear one to the seat tube. Time will tell how long they last, but so far so good. Oh, and in my view, it's not right to say that they don't fit on a Large Defy frame. Sure, one needs to drill a hole in them, but that's easy. Overall, I rate them very highly: 4 Stars out of 5 (would be higher if the arms were the break off type).

Thursday, 23 January 2014

Chuck's Tech Opinion: List of parts to build a bike - record all bicycle components

Total geek-out posting today, but I hope you find it useful! When I build a bike, in my opinion it's best practice to keep a full list of all the parts used. I've found that it becomes an incredibly useful reference guide for later on. It's also quite satisfying to do while you go about actually building the bike.

How to do that?

Well, this is what I use. Here's my list of components that are needed for building a bike (note that some of them may not be required for a particular type of machine):

FRAME & MAIN BEARINGS
Frame
Forks
Headset
Cable hanger for front brake,steerer-mounted or fork mounted up-hanger
Bottom Bracket
Protective sleeve for lining BB frame shell
Chainstay protector

STEERING
Stem
Shim for stem
Spacers
Star nut or expanding bolt for carbon steerer
Stem top cap and bolt
Handlebars
Gel cushioning for bars
Handlebar tape or hand grips and finishing tape
Handlebar end plugs
TT extensions, clips and all bolts

SITTING
Seatpost
Saddle clamp
Seatpost frame clamp or bolt
Seatpost shim
Saddle

DRIVETRAIN & GEARS
Front mech
Front mech mounting bracket
Rear mech
Rear mech hanger
Chain catcher or dog fang
Chainset
Chain
Chain connecting link
Pedals
Cassette or freewheel
Rear hub spacers
Gear shifters
Gear cables inner
Gear cables outer sleeves
Inline cable barrel adjusters
Downtube cable barrel adjusters / stops
Bottom bracket mounted cable guide and bolt, washer(s)

BRAKES
Brake levers
Brake cables inner
Brake cables outer sleeve
Front brake mechanism
Front brake shoes and pads
Rear brake mechanism
Rear brake shoes and pads
Barrel adjusters
Rear brake cable hanger, seat tube clamp mounted

CABLE RELATED
Cable end caps, crimp on
End ferrules for cable outer sleeve
Cable grommets (anti-scratch)
Tape for fixing outer sleeves to bars, etc

WHEELS
Wheels
Rim tape
Inner tubes
Valve extenders (for deep rims)
Tyres
QR skewers or axle & track nuts or anti-theft bolted skewers

ACCESSORIES
Bottle cages and bolts
Computer, sensors and mountings
Light fittings
Mudguards
Luggage mountings

So what I do is list these in a spreadsheet, e.g. on Google Drive so as to be able to access it from anywhere. Then I note details next to each, such as cost, supplier, brand and model/type, frame number, and anything notable, etc. As I said, total geek-out, but well worth it when three years later, you're trying to remember the specs of something or where you bought a part from. The spreadsheet can also be used calculate how much the bike cost to put it together, and more importantly, whether resources are being spent wisely on important stuff, or not!

Wednesday, 19 September 2012

Tyre Fitting: Tread Direction for off road MTB and cyclocross

Which way round should tyres be mounted for off road use and cyclocross racing? I'm fully aware that some manufacturers have rotation arrows on sidewalls and information on websites and in brochures. However, manufacturer's instructions are inconsistent on the subject, as I'll demonstrate below. And then I'll give my views on the answer!

WHAT DO MANUFACTURERS SAY ABOUT ROTATION DIRECTION?

Off road tyres often have a directional tread. Here is a photo of Michelin Mud2.

The knobs form roughly a V shaped chevron or arrow pointing upwards in the photo above. They are marked on their sidewalls with rotation arrows reading "front" and "rear." Michelin's website says:

"Why a particular direction for fitting?
The direction in which a tyre is fitted will enable the user to optimize the performance of the tyres in terms of braking and traction.
In general, the front tyre is more involved in braking while the rear tyre gives maximum traction.
The rolling direction is marked directly on the tyre by an arrow.
The tyres are also marked “Front” and “Rear”."

Is Chuck satisfied with that? No way! In contrast, this is what the Clement tyres website says:

"Q: Which direction should I install the PDX cyclocross tires?
A: We prefer to install the PDX (and most tires) so the arrow-shaped knobs in the center of the tire face forward when viewed from the top. This is true for both front and rear tires. Some riders may install them differently to get different traction characteristics and that’s perfectly OK!"

The arrows on the side of the Vittoria XG Pro (below) are marked "speed" and "traction".


 The Vittoria website says: 

"Is there a mounting direction for my tire?
Mounting direction is shown by a little arrow engraved onto tire sidewall. In the case it is not visible for any reason, do follow the tread pattern design: if it design an arrow, that has to run forward, otherwiese if the tread pattern itself is specular the tire can be mounted either way."

The Vittoria XG Pro have a similar tread pattern to the Challenge Grifos below:

This is what the Challenge website has to say about it:

"The GRIFO is a very special tread pattern which can be used in both directions!
If you point the arrow < < < of the tread forward the tire is faster having low rolling resistance. 
If you turn the tire around with the arrow pointing backwards > > > the tire has much more grip. In this case it is not as fast because there is an increase in rolling resistance. 
It really depends on the type of course you have. So you can actually find your perfect setup according to the course and your style if riding.
The front tire in most cases is kept with the arrow forward, but in a few occasions can also perform better the other way.. 
The rear tire is usually more suitable to switch directions.
 
Have fun trying !"

MANUFACTURERS ARE INCONSISTENT!

So, summing up the above, Challenge and Michelin seem to be saying that this is usually better (viewed from above):

<<<<<< front <<<<<<< ==========BB========>>>>>>>>  rear  >>>>>>>

Whereas Clement and Vittoria seem to be saying that this is usually better (again, viewed from above):

<<<<<< front <<<<<<< ==========BB========<<<<<<<  rear  <<<<<<<

Faced with this, the thorny issue here is about the orientation of the rear tyre tread. I say there's no issue with the front tyre, because every elite MTB or cyclocross bike I've seen has had the front tyre oriented so that looking from above, the chevron/arrow in the tread points forwards and this has always been consistent with the manufacturers recommendations that I've seen.

WHICH WAY IS BETTER?

As to the rear tyre, I've looked at hundreds of photos of elite riders' MTB and Cyclocross bikes on t'net. This includes a number of ex world champions and national champions (eg Stybar, Wyman, Field, Nys). I found the following:

Out of nearly two dozen bikes of elite riders, only one had the rear tyre oriented so that the chevron/arrow points backwards when viewed from the above. The one exception was Tim Johnson's MTB bike (he's more known for CX) on which he had the rear tyre (a Schwalbe Rocket Ron) the other way, with arrow pointing back when viewed from above. The vast majority of bikes had the Vs pointing forwards on both tyres when viewed from above. This included some fitted with Michelin Mud2s, which as I explained  have arrows on them indicating that the rear and front should point in opposite directions. In other words, the riders do not follow the manufacturer's arrows!

I would rate the empirical evidence and practices of world and national CX and MTB champions very highly - presumably they've done enough qualitative testing and timing to form a considered view. 

I run Michelin Mud2 on my CX bike and I've tried them in both configurations. To me the one with the V on each tyre pointing forwards (as viewed from above) works best. Why should this be? Well it could be a placebo effect - that I'm gaining some positive vibes by simply doing what the pros do! 

On the other hand, perhaps there is another reason. Going downhill across a slope, making an off-camber turn, is one of the more risky manoeuvres in cyclocross. The bike can wash out sideways very quickly on a greasy surface. Let's examine that situation a bit more. One is rarely driving the rear wheel hard and may even be braking a bit, front and rear. The diagram below shows the angle of the chevrons as they contact the ground. The green arrows indicate the direction of the slope. In each example A and B, the tyre is rolling from right to left. In other words, not straight downhill, but slightly across the slope. The red oval shows the contact patch schematically. I've put it on the uphill side, because that is the part of the tyre that contacts the ground in this situation. You could imagine the grey chevrons as tyre prints in the mud. Think of the arms of each chevron on the tyre as little skis! In example A, the tyre is mounted with the Vs pointing backwards as the bike is viewed from above. You can see that the uphill arm of the chevron - in the contact patch - is almost parallel with the slope. It is likely to slip easily just like a ski pointing downhill. In example B, the tyre is mounted in the conventional way for a front wheel - that is, Vs pointing forward when looking at the bike from above. In the contact patch, the arms of the uphill edge of the chevron are roughly perpendicular to the slope. The skis are cross-slope in like a skier digging in edges on a side slope. If you're not convinced about the ski analogy, remember that the rider may be braking. There seems to be a clear advantage of B over A, at least going downhill.

Uphill, you can use the same diagram as above but imagine the tyre rolling from left to right. A has tyres mounted with the Vs pointing forward as seen from above. However, uphill, you will be travelling slower and probably not braking. B seems better than A. I guess that's what makes a good tyre tread design - functioning well in both directions. Remember, the diagram above is very simplified - for one thing, it does not show the edge tread, or the diamonds filling out the chevron in the middle as in the Grifo and Vittoria XG Pro, both of which are bound to affect performance. 
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CONCLUSION

So, having tyres fitted like Vittoria and Clement seem to prefer (Vs pointing forwards front and rear when viewed from above) appears more sure-footed for off-camber downhill tracks and cross-slope descents. It seems to be the more popular approach for pro riders. It's also supposed to be the faster orientation according to the tyre manufacturers. However, reversing the rear tyre could be worth a try e.g. where there are significant stretches of slippery off-camber uphill on the course.

Monday, 14 May 2012

Quick Release lever alignment

Michael Barry, the Team Sky professional rider, recently wrote about his favourite cycling innovation, the humble quick release lever (article here). The other day, I looked idly at bikes in a public rack. I noticed that people position the closed lever in many different orientations. Which way should QR levers point? A good subject for a "Chuck's Tech Opinion," I mused.
Sounds like a trivial matter? No way, I say! A good friend of mine had a minor crash on his beautiful all carbon bike. The front fork was gouged by the QR lever - a very expensive mishap. The lever had been locked in front of the fork blade, pointing up. I've also heard stories about a person who pulled a bike out of the rack, and only when riding discovered that the QR lever had been snagged open!

When you examine pro bikes, it's very interesting, as it seems that rear lever alignment is team, or should I say team mechanic, dependent. So, for example, TT bikes from Radioshack/Leopard Trek (including Cancellara), Vacansoleil (including Larsson), Saxo Bank (including Boaro), Astana (including Brajikovic) have the QR lever on the rear wheel pointing backwards, as in the photo above. The others have the QR lever positioned under the chainstay pointing forwards (e.g. Team Sky), or back and up, or in the crook between chainstay and seatstay like this:
"In the crook" also appears to be the way most pro cyclocross riders orient the rear wheel QR lever. I guess that is because the risk of snagging the lever (e.g. by a passing bush!) is lower in this position (it's tucked into the stays, which protect it a little). Another thing the pros have to worry about (but I don't!) is ease of access for wheel changes.

When it comes to the front QR lever, it's much simpler. Among the pros, as far as I can tell, it is always pointing backwards. Either under the fork, or backwards and upwards. The other pro thing is that the lever on the front wheel tends to be on the left side of the bike (on the rear wheel it HAS to be on the left side).

So, fwiw, here's my opinion. On the rear wheel of CX bikes and commuters that are often parked in racks with other bikes - where there is a risk of snagging the lever - I will orient it tucked into the crook of the seatstay and chainstay. Whereas for TT, I may have it pointing backwards. It really depends on the frame structure around the dropouts and the shape and configuration of the QR lever. I am not that keen on pointing it forwards and down under the chainstay - but I would do that if there is no other way (it depends on the configuration of the lever and type of frame - sometimes it won't go into the crook without fouling the frame, for example). On the front wheel, it's always pointing back, either under the fork or backwards and upwards behind the fork blade. Usually this is achieved with the skewers oriented so that each QR lever is on the left side of the bike.

And yes, I agree with Mr Barry that the quick release is a great bicycle innovation.

Saturday, 31 March 2012

Is Shimergo a waste of time?

Shimergo means using Campagnolo Ergo shifter levers with a Shimano drivetrain. Check out this beautiful Bianchi renovation (from the interesting "Pistarice" blogsite):
I used to think that messing about, mixing and matching combinations of components from one manufacturer with those from another, was pointless. Each brand is designed to function with its own compatible parts. So obviously, it would be less than optimal to use bits that were never designed to work another brand, right? But no, both theory and practical experience indicate otherwise.

The most common combination seems to be 10 speed Campagnolo Ergo levers with either 8 speed Shimano drive, or 9 speed Shimano provided the rear derailleur clamp washer is rotated a bit (what Shimergo practitioners call "hubbub" - photo here). 11 speed Campagnolo shifters also work with Shimano 9 speed systems. However, since 10 speed Campagnolo levers (e.g. Veloce 10) are significantly cheaper than Shimano STI levers (whereas Campagnolo 11 speed ones are comparably priced), Shimergo is useful solution for:
  • upgrading Shimano geared bikes with down tube shifters - e.g. touring bikes, or old road bikes
  • converting MTB drive trains for road use
  • a cheaper and I'd say "sexier" option for replacing defective 8 or 9 speed Shimano STI shifters
  • in some cases, improving braking performance, because the Campagnolo brake levers are likely to be an upgrade over the original brake levers 
So, for certain bikes, Shimergo is certainly not a waste of time. What we need however, is some list of the known combinations of types and models that function well together (I mean with more product detail than the combination tables in Chris Juden's CTC article). And let's not stop with Shimergo. What about Sramano, which I have heard can work too? If any reader has first hand knowledge of a combination of mixed brand gear train parts and shifters that work well, please do add a little comment here with product and model details. If I can gather enough data, I'll make a table of it and share that interoperability info with everyone!

Tuesday, 27 March 2012

Bike frame material: Is steel better than aluminium, carbon, etc?

Which is the best: steel, titanium, aluminium alloy or carbon? For that matter, what about bamboo and wood?!
Such questions have vexed bike designers for many decades. This post is not about the relative merits of each of these materials for bike frames, as there is plenty of information about that already (one of my favourite resources is here). Rather, I give my views on fitness for purpose and ride quality. I used to believe people who said that aluminium gives a harsh ride, until I bought a good alloy road bike, alloy front forks and thoroughly tested them in cyclocross. In my view, in practice, neither were harsh. I used to believe people who said the type of steel tubing really matters, and those who said 531C is the best, until I realised that it is not that simple. In the 1990s 7 steel bikes, identical except for the tubing, were built and blind tested (see this fascinating article). After much riding and reflection, the reviewer commented that the differences between the steel alloy bikes were very subtle - really rather minor. 

There are many ways to create a bike that works well and suits its intended purpose. Factors such as weight, shape, stiffness, tyres and saddle have a huge impact to how a bike works and feels. Ride quality is determined by so much more than frame material. I think there is a good way to look at this. First of all, think of all the things that make a bike efficient. What makes it go further, faster for less work input by you, the engine?! Then list the things that make your life on the bike more comfortable. After doing that, note that some of the comfort enhancing aspects serve to reduce efficiency, but even so, the increase in comfort may be worth it. So here's what I mean:

EFFICIENCY FACTORS
1. Bearings smooth. To put it another way, a jammed wheel would give atrocious "ride quality"!
2. Stiffness. Frame doesn't flex around when you push the cranks, descend at speed or turn
3. Wheels don't wobble, hop, or flop
3. Tyres have low rolling resistance 
4. A decent engine: rider has appropriate fitness and technique (my grandma ain't as efficient as Bradley Wiggins!)
5. Shape and size
6. Fitting is good, proper muscles engaged
7. Clipless pedals
8. Light weight
9. Aerodynamic
10. Components function efficiently 

Some of which work against the following:

COMFORT FACTORS
a. Tyre size and pressure - fatter, softer are more comfy
b. Saddle type
c. Suspension, whether through flexy frame or actual springs/dampers (which also add weight)
d. No nasty resonant effects - from high frequency teeth rattling vibrations, to scary front wheel shimmies
e. Relaxed seating position and rider view point
f. Contact points feel nice, allow subtle body shifts and position adjustments while riding
g. Components are convenient and comfortable to use

I hope you can see where the frame material fits into this. Basically, it contributes to 2, 8, a bit of 9, c and d. But any of the other factors could ruin the rider's experience of what is otherwise a great frame. Thus, all of the materials listed at the start of this article may be used to make a lovely bike frame that functions very well  - but only under particular conditions. Heavier tubing will make a stiffer bike. Both the load lugging touring cyclist and the road racer want a light, stiff bike but suitable frames are not the same in each case. Carbon fibre is great until it gets whacked or even scratched, when a small defect could make it dangerous through risk of catastrophic failure. Bamboo is natural carbon fibre! Modern super-steel alloys like Reynolds 953 undoubtedly make light, comfortable, strong, stiff, corrosion resistant frames, but so can carbon fibre composite, titanium and aluminium alloys. To underline my point, last season, Zdenek Stybar and Ian Field (world and national cyclocross champions) both used aluminium alloy bikes, while many of their world class competitors opted for carbon frames, but I don't know of any champion racers who used a steel frame. 

Ideally, your choice should be a personal one, based on real evidence and your preferences after test riding. After all, you will be riding the bike, not the person who gave their opinion on the frame material!