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Tech letters for October 17, 2002
Edited by John Stevenson
Confounded by carbon fiber? Need to sound off about superlight stuff? Tech letters is the forum for your gear-related questions and opinions. We'll attempt to answer all questions that don't require a PhD in astrophysics or industrial espionage.
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Creaking Ksyrium SSC
Sloping top tubes
Top-pull for Cross
Rear clusters & climbing
Campag Hiddenset problems
Koobi PRS
Pedals
Road Tire Tech
Shimano XTR
Sizing
Squealing brakes
Upgrading an old bike
Creaking Ksyrium SSC
From François Courteau
Does any one have the solution for these front wheels creaking during climbs? The noise is constant and doesn't come from the crank since it continues when I coast while pushing on handlebars one side at the time. The wheels are one summer old and totals 1,500 km.
Sloping top tubes
From Manny Rubio
How aggressive should the slope be on compact frames? Does the slope matter? What are the advantages of a sloping frame compared to a standard one, if there are any?
The slope doesn't really matter. While I'm sure we'll hear from a few bike company marketing departments with esoteric justifications for sloping frames, I think this design is mostly a matter of fashion. It undeniably makes for a slightly lighter, slightly stiffer frame, but it requires a longer and therefore more flexible and heavier seatpost, so you're in 'swings and roundabouts' territory there.
As long as the pedals, handlebars and saddle are in the right place for the rider, it's not dramatically important how they're connected together.
Top-pull for Cross
From Mark Jenkins
I have a Bianchi Axis cyclo-cross frame that requires a top pull front derailleur. Several mechanics have suggested to me that that is a bad idea and have encouraged me to use a single chainring set-up for cyclocross rather than trying to make an FD designed for compact drive mountain applications function with the 48/38 cross gearing. The complete Axis comes with an LX top pull, I believe.
Can anyone give me advice on what the best equipment and set-up is for a cross frame requiring a top pull FD?
Mark Jenkins
Rear clusters & climbing
From Sean McNamee
I have a bike that runs a Centaur rear cluster 13/26. My riding includes a lot of hill work. Setting aside improvements through training, would I notice much improvement in climbing by changing to a 13/29? Front crank is a double 53/39.
Well, it'll give you a lower gear, but a factor of 10 percent or so. Climbing will therefore be easier if you use the lower gear to go slower, but you might find you're more efficient at a faster pedalling speed and therefore climb faster. Kinda hard to predict, but a worthwhile experiment.
Campag Hiddenset problems #1
From Craig
[Original letter] Check the steerer at the front where the stem goes.
I'll bet that, due to the considerable clamping pressure, the carbon steerer shows signs of expanding into the hole of the stem (at the front of the steerer clamp of the stem). This is only exacerbated if you further tighten the stem, causing the stem to "walk" up the steerer. The fix is to make a shim out of very thin metal sheet (brass or the like) about .25 mm thick, cut it a bit less than the height of the clamp and wide enough so it goes about halfway around the steerer, loosen the stem clamp right off and slip the shim down the front of the steerer between the stem clamp (so your shim goes from 9 o'clock to 3 o'clock viewed from sitting on the bike) to cover the hole in the stem clamp. Tighten it up and hopefully it will be the end of your problems. Oh, and I presume you know - no grease on the steerer.
Campag Hiddenset problems #2
From Bill Corliss
Carbon steerers are "slipperier" than steel or aluminum. I and others have had trouble keeping headsets tight with carbon steerer tubes because the stem continually slides slightly no matter how tight you make it. The problem is increased if you are not using a top cap with an aluminum insert to reinforce the steerer because the stem causes the carbon to compress and get smaller. How much of a problem this is depends on what fork. Some have steerers which are thicker and more resistant to compression than others.
Campag Hiddenset problems #3
From Scott Hill
The original letter doesn't mention what if any kind of spacers are being used. If they are carbon I recommend changing them to machined aluminum. Many of the carbon headset spacers I've seen aren't made completely square and move against the stem, headset, or each other causing the change in headset tightness.
Campag Hiddenset problems #4
From David Lewis
I had a similar problem with my Giant TCR with internal Cane Creek headset. The headset was working loose because, instead of a "star fangled nut" inside the carbon steerer, the Giant uses a tricky-dicky expander bolt so as not to score the carbon fibre internal surface. This was sliding slightly against the smooth internal carbon surface and working the headset loose with road vibration. Does your bike use a similar expander bolt inside the carbon steerer? If so, try wrapping a few turns of ordinary plumbing tape around the expanding doo-dad before re-inserting in the steerer and tightening the headset. This increases the size of the expander slightly so it grips better and now the headset has been solid for 3 months with no further adjustment necessary. Try it, it worked for me.
Plumbing tape also works a treat on creaking bottom brackets.
Campag Hiddenset problems #5
From Russ Williams
It is a design flaw and one main reason why the idea of internal hiddenset headsets should never have taken off in the first place. It is the reason that well respected manufacturers like Chris King and Colnago frown on the design. That design only offers aesthetic value and no real performance upgrade. It forces the bearings to be subjected to much higher stress from direct vibration of the frame and fork as opposed to that force being dissipated by the integration of the extended race of the headset cup inside the frame on a conventional unit. It offers cleaner looking lines, but no real advantageous weigh savings and only cleaner looks not cleaner aerodynamics. But don't take my word for it, look at the websites of Chris King and Colnago and see their explanations.
Koobi PRS #1
From Chuck Barthel
I talked to Koobi about this and they told me to send it back and they would send out a replacement saddle. They sent the saddle out the same day I called. Customer service at Koobi was great. I received suggestions on seat posts that are compatible with the saddle. New saddle was perfect in regards to the rail spacing issue. All in all, the saddle looks great, it rides great (takes the edge of the bumps on my hard tail and distributes the pressure to the sits bones instead of the soft tissue area), and dealing with Koobi has been a positive experience, with quick turn around for exchanging saddles.
I don't get this quality of customer service when I go to my local bike shop so I just wanted to let anyone, that may be considering a Koobi PRS saddle, know that they will get a great product and equally great service.
Excellent to hear a story of good customer service - props to the folks at Koobi for sorting Chuck out.
Koobi PRS #2
From Kyia Malenkovich
I have raced on the PRS saddle all season, on and off road. I use a Ritchey WCS seat-post. I had no problems with mounting the saddle to the post. Both of my bikes are Trek OCLV carbon and I find that the Personal Ride System actually works. I used the bumpers that came originally installed in the saddle (yellow), and actually feel a little give when riding off road and on the road. It makes those long hours in the saddle a little more enjoyable. My lower back loves it!
Kyia Malenkovich
Dogfish Women's Elite Team
Pedals #1
From Scott Peterson
I'm of a similar age and weight, and use Speedplay pedals (with the stainless axle, not Ti), and Carnac LeMond (aka Legend) shoes. It's a great combination, though I did need to do a little fiddling with the cleats to get them to fit the shoes properly.
Pedals #2
From Gabriele Giordano
Hallo from italy. I'm 40 years old and also own a Cannondale team replica 2003. I've bought the new TIME Impact Mag TI. They're absolutely fantastic.
Road Tire Tech #1
From Stacey Jenkins
I used to do this to prevent toe overlap on my small (52cm) Cannondale. I found that the 23 in back made for a bit more comfy ride, while the 20 up front kept me from making an ass of myself while attempting to trackstand at stoplights.
Road Tire tech #2
From William Lim
The advantage to a wider tire in the rear is really comfort. You might have noticed that your rear wheel wears out more quickly, that's because more of your weight is on the rear wheel and a slightly wider wheel will be a little more comfortable. The other major consideration is handling, wider tires will handle better. There are lots of factors to consider; road conditions, hilly or flat ride etc. A little trick that I do for climbing is to pump up my front tires higher than my rear. When I stand, I transfer more weight to the front tires. With more psi, it has less road resistance, then fast descents I get into a tuck and put more weight on the handlebars and the pedals again transferring weight to the front wheel and flying down the road. Be careful not to over inflate the front tire, this could compromise handling.
Road Tire Tech #3
From Aki Sato
On 20mm vs 23mm tires... The 20s have two disadvantages (for a given make/model):
1. They will not corner as well (this has to do with the smaller cross section, some tire engineer or physicist can explain why). I think a narrow rim (17mm or so) helps improve 20mm tire cornering, but most rims (20 mm wide) are designed for a 23mm tire.
2. They pinch flat easier.
The 20s have 1 or 2 advantages (other than the questionable aero one): 1. As mentioned, they are typically lighter than the larger 23mm tire, so they should accelerate quicker. 2. They might roll a little faster for a given make/model but this depends on the surface. Rougher surfaces negate any rolling advantage the 20mm tire has.
On the aero bit, my understanding is that the rim cross section has a lot to do with the aero efficiency of a tire. If the rim cross section is not matched to the tire, there is no aero benefit to the narrower tire.
Finally, using two different sized tires means you have stock two different spares. It's easier to stock up on spares if you only use one tire size.
Measurements by Continental indicate that rolling resistance increases as a tyre gets narrower. Rolling resistance arises because energy is lost in hysteresis when a tyre bends and unbends as it touches and leaves the ground. A narrow tyre has to flex further, and also has a less circular contact patch to support a given weight of bike and rider at a given pressure, which therefore has a longer perimeter. If the tyre isn't matched to the rim to give good aerodynamics, then the only advantage of a 20mm tyre is a tiny weight loss – and the ability to tell if it's heads or tails when you run over a coin...
Shimano XTR #1
From Karl Butler
This goes out to all who have complaints about the new XTR - get over it!
Back in the day (1998) when Shimano introduced the M951 Reverse pull rear derailleur, it was working with a shifter that was always designed for a standard rear derailleur. Shimano have their new system designed with rapid rise in mind the whole time. The easy way to get used to the new system is to put the optional thumb lever on your XTR - STI. Running with the new XTR rear derailleur, it will give the same feel as your current Rapid Fire levers. Lets face it, when on a mountain bike it makes sense for the rear derailleur to release spring tension when shifting "up" the cassette to a lower gear. The shift will be less stressful on your gear, not to mention fractionally quicker. On a mountain bike I think this is more important than getting to a higher gear (or "down" the cassette)
As for the 44t big chainring, bring it on I say. Who can honestly recall the last time they were in the 46-12 or 46-11 (if you're that way inclined) offroad, let alone spinning out that gear? If you spin out the gear on the road, the solution is simple: get a road bike. Most people who ride complete XTR kit have a road bike for doing road miles anyway; it just makes sense. There is no problem with the gears being slightly lower. If you are a big ring grinder, you'll appreciate the 44t big ring beacuse it means the jump between the gears will be smaller and easier for your knees and quads to cope with. If you're still insistent on mashing big gears, you should pre-order your wheelchair now because you'll just end up killing your knees.
As for those who say "what about if you crash?" regarding the new XTR shifters and their fear of breaking STI's: Do what everyone else does and get an insurance policy that will cover you while you're riding. That's what a lot of roadies do. If you can't handle the thought of crashing, sell your bike(s) now because unfortunately it's just as much a part of the sport as wearing a helmet - everyone does it.
All this isn't just talk either. I've had a ride on the new XTR stuff, it's all good. The only complaint I had was that the bike was still running an old M952 derailleur (2002 vintage with standard spring) which was how I learnt about the shifters. Get over your inhibitions, get into the new gear because it's well worth it.
Shimano XTR #2
From Brad Silverberg
Are the XT disc brake levers compatible with the new XTR disc brakes? If so, are the XT levers available separately? The new XTR crankset, disc brakes, and disc brake hubs sound great but ugh, I don't want to have to use the new shifters and Rapid Rise derailleur. Maybe Shimano will make a non integrated set of brake levers for the new XTR disc brakes.
Yes, the new brakes do work with the old XT levers, according to our sources at Shimano.
However, I wouldn't dismiss Rapid Rise without trying it.What many people are missing in criticising rapid Rise because it removes the ability to slam your way up the sprockets into a lower gear is that it can make very rapid, one-click-at-a-time shifts very easily. Rapid Rise takes out the human grunt factor from shifting into lower gears, instead letting the derailleur spring tension and sprocket shift gates and pick-up teeth do all the work. This makes for very smooth, quick and most of all, consistent shifting.
I think the problem with acceptance of Rapid Rise has been that many of us -- heck, including me as I said in our XTR review -- have our reflexes so well conditioned to the conventional way of shifting that they're practically hard-wired. I'm looking forward to the XT version of the new system so I can get some long-term saddle time on it -- the stuff on my current bike has far too much life left to justify a whole new XTR group for the sheer sake of it!
Shimano XTR #3
From Andy Mills
I must say that after first seeing the photos, I wasn't quite sure what was up at Shimano. I am an avid XTR fan, it works, works well and is completely dependable. It always has been. Every top pro in the world is on this stuff and I really wondered why Shimano would change the shifting action. However, after seeing it, and seeing how easily it works and how fluid the mechanism is - this stuff is going to rock. It concedes several grams to the old stuff, but only with the disc brakes. Any rider who is that picky needs to do nothing more than urinate before riding. The best part of the entire group is in the cranks. Going to a 44T chainring is a huge move that will really expand the gearing options. A 46T was ok in some places, but a 44 offers much more diversity to compensate for terrain. Thanks Shimano!
Shimano XTR #4
From James Reinhardt
Tom Pon wrote:
"When shifting the front chainring to a smaller ring on a tandem going uphill, you have to slightly ease your pedal pressure in order for the shift to occur. That is because the front derailleur spring is not strong enough to handle the shift under full pedal pressure so you end up losing momentum. "
This problem is not caused by the fact that the spring tension on the front derailleur is the "wrong way round", but by the fact that the front derailleur works on the tensioned side of the chain run, whereas the rear mech works on the untensioned side of the chain run.
And doubtless half a gazillion other people will write in to point this out...
Sizing #1
From William Lim
I agree that the important issue is that the pedals, saddle and handlebars are all in the right places. I would think a smaller size would add to the handling issue. The advantage to smaller frames is less weight and clearence of the top tube while rocking the bike during standing. Head and seat angles must also be considered, different sizes often have different angles. Racers sometimes like to have the smallest frame possible with the longish stem and seatpost, but this could result in a less stable bikes, this might be desirable for racing but not desirable for someone that is not the best bike handler. Smaller frames can often result in/or increasing wheel/shoe overlap.
Sizing #2
From Dave Palese
Michael, it sounds like your bike fits pretty well. Now I say that without seeing you on it. The most important thing when it comes to bike size is that you are comfortable and that you are safe. You have said you're comfortable so that is good.
The safety issue speaks to your ability to handle the machine at speed and in pressure situations. The most common safety issue with fit is reach, the bike being to long, either from top tube length or a stem that is too lon). When a bike is too long, you won't be able to steer the bike as effectively. Usually, bikes that are too short are just uncomfortable.
I wouldn't worry too much about what the pros are riding. They may be making sizing decisions for various other reasons. But as long you are comfortable and safe, you're all set. Have fun...
Sizing #3
From Alex Parker
Looking at the bikes the pros ride is not a reliable way for a recreational rider to size his bike. Euro pros almost always ride very small frames with long stems and seatposts. Why? Because they can - these guys are usually super-flexible (like palms flat on the floor flexible), and that tiny frame with long stem lets them assume a very low, aerodynamic position. For normal humans like you and me, who don't have exceptional flexibility (I'm assuming that your self-description as 'injured former runner' predicts average at best flexibility), a larger frame with proportionally shorter stem brings the height of the handlebar up closer to that of the saddle, making for a comfortable position.
By way of example, I'm 6'0" (183 cm) and ride a 56cm c-c Coppi KSC with a 110mm stem. If I was as flexible as Andrea Tafi, I could probably ride a 53cm bike with a 130 or 135 stem.
Sizing #4
From Manny Rubio
The important factor to me in sizing is the top tube length. It is difficult to get a compromise with top tube length, specially if you need something longer. An extended stem will affect handling and stability specially during out of the saddle riding.
As for seat tube, there are a number of good quality extended seat tubes. If the seat tube is long, then it will really boil down to aesthetics. You don't want to ride a bike with the seat tube missing, right?
Sizing #5
From Geoffrey A. Mar
Don't worry about it. The pros all ride a smaller frame because they are lighter and stiffer. The critical measurements, seat tube angle and top tube length, are the same. On a production frame, in order to get a long enough top tube and a shallow enough seat tube angle (to avoid a 14cm stem or not being able to knock the saddle back far enough on the rails to position yourself adequately in relation to the bottom bracket) you have no choice but to go with a frame having a longer seat tube. As an example, I am the same height and ride a 56 C-40. I should theoretically be on the 54, but the top tube would then be 1.4 cm shorter and the seat tube angle would be 74'18". There is no real downside to this, other than a slight loss of rigidity and a slightly heavier frameset (oh, and the seatpost being lower in the frame, resulting in a loss of pose value).
Sizing #6
From Brent Emery
The reason the Tour riders have such small bikes is the need to have the handlebars so much more below the level of their seats compared to what leisure and enthusiast riders feel comfortable with. Peleton bodies change over the years with the 30,000+ km/yr that pro cyclists willingly endure. We can only hope to sit so flexible and relaxed on our bikes without that many hours with the wind in our ears. So long as they get the length of top tube that works for their bodies (not ending up with too long or too tall of a stem), pro road cyclists prefer the smaller bike as it is stiffer, handles more nimbly and has better aerodynamics.
Assuming you're already clued into seat tube angle/top tube lengths, one measurement that doesn't get enough recognition for its importance in comparing one bike to another is the head tube height. Bikes of the same seat tube size may have different head tube heights (the top tube angle from horizontal will be level or sloping to the front or the back). This, along with the amount of (or lack of) headset spacers and the angle of stem can be combined to many variations on a given bike. For your needs, if you can "connect the dots", and your bike fits, your doing well.
If you are tempted to get more aero, do so... so long as your body (neck, back, arms, hands, hamstrings etc) don't revolt. Make small changes in position after your hard weeks of training or racing so the changes get broken in on your easy weeks. This way you lower the chance of an injury or having a lingering problem if it doesn't work out.
Squealing brakes #1
From Michael Sylvan
Whatever else you do, do not use Shimamo Ceramic Pads on your new rims. I love Shimano stuff, especially their drivetrains, but these brake pads are horrible. The quickest way to ruin your rims is with these pads.
The "fix" is to use Kool Stop Green Ceramic Pads, and to adjust them properly. They won't coat your rims with diamond hard crap that can't be removed like Shimano pads do (in my experience), they work wonderfully, and they usually don't squeak either. The financial risk is minimal in any event.
Squealing brakes #2
From Brendan Moylan
I have used Mavic 217 (and when they were discontinued, 517) ceramics since 1996. I have always used XT V brakes with the rims. I was always puzzled at the number of people who complained about the way XT Vs squealed, never having had this problem - until I replaced my circa 2000 brakes with a new set (XT Vs again) about six months ago at which point the front brake began squealing like a pig on heat. I adjusted the angle of the pads to the rim (i.e., toe in) and hey presto, no more pigs.
Must have been dumb luck that my previous brakes were all properly adjusted. I suspect this will work with your Avids as well. Also check that the bolt which holds the pads on (and the bolt which holds the brake on the boss) is tight. As to whether you use ceramic pads or non-ceramic pads: I have never found it makes a difference in terms of squealing (although they sound more abrasive) or braking power (I think the non-ceramic pads have a better "feel" than the ceramic specific pads). The non-ceramic pads may not last as long - hard for me to compare because I have used them so infrequently - but then I think they cost less than the ceramic pads.
Squealing brakes #3
From Rob Parniak
I had a similar problem once. I had old (non-UST) crossmax wheels with various V-brakes (XT, arch rival, and old LX) and lots of squeeling on the front brake. I tried everything from toeing in the brakes to scrubbing the rims to changing the pads. Nothing worked. Then I got a shimano carbon fibre brake booster for the front. Problem solved. My SID fork was flexing so much it caused the brakes to squeel and chatter. You didn't say what kind of fork you had, or if the problem is at both ends, but I would suggest trying a brake booster before you do anything drastic. I certainly would not get the wheels re-built with new rims as the above response suggested - the crossmax rim is the best part of those wheels. Those are very popular XC wheels and I don't hear all that many making any excessive squeeling noises - it is not the ceramic coating.
Squealing brakes #4
From Bill Corliss
You might try using some abrasive brake pads for a while. This will smooth the roughness off the rims and may cut down on the squealing. Kool Stop makes some, green I think that are designed to work on ceramic rims. Once the rims are smooth, I have had no problem going back to regular pads.
Squealing brakes #5
From Joe Fritsch
I've actually had less problems with ceramic rims than normal rims in terms of squealing.
You should be using ceramic pads. You can't expect the pads/brakes to work correctly if you are not using compatible parts. Ceramic pads are made for ceramic rims. I have Avid mag brakes (and avid ceramic pads).
For pad setting, I release the spring on one side which forces that pad against the rim. Then loosen the pad nut on that same side, center the pad where I want it to hit the rim, and tighten making sure the pad does not move. Then repeat on the other side. There is no toe but I have had no problems with out it.
Every now and then I will file my pads and then reset them as above. I have had some squealing for the first 5 to 10 mins of the first ride after the filing but it quickly goes away.
In my opinion ceramic walls are greatly superior to standard brake walls. I use to replace standard rims 3 to 4 times a year if I had a lot of rain races. Plus with ceramic, the brakes actually work during in the rain and mud!
The key to ceramic rims working properly is to use compatible ceramic pads.
Squealing brakes #6
From Jonathan E. Gordon
Take a careful look at your brake pads - see if the surface of the pads looks shiny, or has little bits of metal embedded in it. If so, use some light sandpaper and lightly sand off the shiny surface, and use a pick to remove any bits of metal or rock that may be embedded in the pad. Also make sure to clean your rims regularly to avoid buildup. I have dealt with squeaky brakes before, and this seemed to fix the problem most of the time.
Squealing brakes #7
From Wolter, Richard
In regards to the reader having problems with squeaky pads, do not use the ceramic-specific pads from Shimano as they as too hard and will eventually eat right through the ceramic coating on the rim. I suggest towing in the standard pads.
Squealing brakes #8
You definitely need pads designed for ceramic braking surfaces. I had that exact thing with my crossmax wheels when my XTR ceramic pads wore out and I got normal (non-ceramic) pads, not only did they wake the dead, but the wear rate on the normal pads was horrendous. Hope this helps.
Squealing brakes #9
From S Jones
Try using ceramic brake pads. The rubber compounds in the ceramic pads are different, and it will help eliminate the squeal. you may also need to toe-in the pads a little. You should not have to have the wheels rebuilt.
Upgrading an old bike #1
From Evan G. Reynolds
Chris, the CAAD3 you ride is by no means a bad frame, it is handmade after all. However, Cannondale have made HUGE improvements in the ride quality of their road frames over the last four tiers of frame evolution. The hourglass seatstays and advanced butting of CAADs 4 through 7 make the ride much more supple and therefore more enjoyable. So basically, if you have the money to buy a brand new Cannondale (the r600 which is CAAD 5 goes for about $1200) you will definitely be happy with the change.
Upgrading an old bike #2
From Russ Williams
Chris, there are many advantages to that particular Cannondale frame that set it apart from the rest of their line. As with all frames you have to weigh the pros and cons and decide for yourself, but some of the pros of that particular frame are this....
That CAAD 3 frame is one of the stiffest Cannondale has built. It has straight chain and seat stays. The difference between it and the CAAD 4 is that the CAAD 4 has the curved seat and chain stays that were designed to soften up the ride of that bike. The con is that there are better ways to soften the rear of a bike up and still have it feel stiff and that is the explanation behind the current trend for carbon fibre seat stays. It allows a bike to feel stiff without being overly harsh.
On the upside to that frame, Cannondale sold it as a Dura-Ace bike at one time and offered it to the pros of Saeco, so yes the frame is worth putting good parts on. And unlike Cannondale's CAAD 6 or 7 frames, you can use any standard bottom bracket and crankset with it. If you like stiff aluminium bikes, it's a perfect choice to upgrade to Ultegra or even Dura-Ace.
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