milkbaby

I'm getting the rear wheel skipping sometimes when cornering or turning hard, and it's a little disconcerting. I just realized it has only been on one specific bike with a specific wheelset, Cannondale CAAD9 with Easton EA90 TT hoops. The rear tire is an old Vittoria Zaffiro Pro Slick clincher that is not that squared off but is over 3 years old tho seems like plenty of rubber and no casing showing. This has happened even at speeds that don't seem excessive, maybe 20-25 mph corners and traffic circles, not happy about almost going down in front of cars in the traffic circle!!! This has always been in dry conditions on good pavement. I am running Conti GP4000 clinchers (both colored and the black S version) on other bikes with zero problems but on other wheelsets which are probably stiffer; seems like the stiffer wheels would be more likely to skip tho, right?

The wheel seems like it's sitting down tight in the rear dropouts, but not sure if I need to up the quick release clamping pressure more? I can smack the wheel hard on the top and it seems tight. Is it just old dried up tire rubber? Something else? Experts please chime in! THanks!

Creatre

Be more careful about your weight and balance, and grind a little bit harder gear. I find the weight distribution and cadence affects when my rear wheel moves around in crits.

merlinextraligh

Couple of things can cause this to happen. One, are you pedaling when it happens? Applying power when you're still cornering can definitely cause the rear wheel to skip. I've done this jumping out of corners in crits. You learn when you can and can't pedal.

Two, improper weighting of the bike. Standing hard on the outside pedal (i.e. putting enough of your weight on the outside pedal that you have little to none on the seat) will anchor the back wheel. If your weight isn't right the back wheel will skip on road irregularities.

Three, you could just be exceeding the slip angle of the tire, given the radius, speed, and road surface. However, that usually causes the rear wheel to slide out not skip.

Seattle Forrest

Where is your weight while you go through the corner? Try getting down a little bit lower.

carpediemracing 

Having experienced this myself here are a few thoughts. There are two basic causes for the rear wheel to skip - excessive tire pressure and too much weight forward. Since this is isolated on one bike it becomes interesting.

1. Too much pressure. If you run excessive pressure you'll reduce the tire's suppleness. I learned this the hard way when, psyched for a particularly important race, I really cranked the pressure. I couldn't even get around curves in the road without the rear wheel chattering.
2. Hardened tires. As tires age they lose flex agents, usually due to UV light breaking them down. This is why tires are (or used to be) molded with a UV resistant wax. If you squeeze the tire you may see white stuff in the cracks - that's the wax squeezing out. At any rate the tread becomes hardened with age. Depending on when the tire was made it could be quick or not quick. I had one set of tires that were so hard I could barely ride them 6 months after I got them. Other tires have lasted many years. If your tire feels hard/slick, like wood instead of like grippy rubber, you probably ought to replace your tire.
3. Narrow tires. Wider tires are more supple for a given age. If you run a 700x19 in the rear the tire will be much more "chattery" than a 700x23 or a 700x25. Depending on the age/condition of your current tires you may want to try a slightly wider rear tire.

So the above are tire related. Next is fit related, mainly having to do with weight distribution.

If your other bikes aren't as "racy" as the CAAD10 you may be putting a lot of weight forward on the CAAD10 compared to your other bikes, through a long and/or low stem. That's okay if that's the way you need to fit the bike, but the result is that you end up weighing down the front of the bike much more than the rear. This is great for cornering - in fact, when I am really blasting through a turn, I'm really weighing the front wheel. If the front wheel slides out I'm history but if the rear moves a bit it's fine.

If your fit is not radically different from your other bikes then it may be an attitude you have when you ride this particular bike - it's your race bike (or crit bike) so you corner more aggressively than normal, exposing weaknesses in weight distribution, tire condition, etc, that you normally don't see on your other bikes.

If your bike is a bit too aggressively fit then you might consider throttling that fit back just a touch. Get more weight over the rear wheel. Most riders can slide back on the saddle a touch more. If your saddle is too high or in too much of a forward/TT position you may not be able to slide back enough. You may want to experiment with a lower, further back position. This is compromising fit but if you have an extreme forward/TT type position on your road bike then it may be worth it to experiment.

I say the above but I personally have a very forward position on the bike. It's due to fit - I have very short quads and overall have very short legs (29" inseam, 5'7"). I ride a size S Giant equivalent frame in height but with a 56.5 cm top tube and a 12 cm stem with a full reach bar (so if I were to use a compact bar I'd want to run a 59.5 cm top tube with a 12 cm stem). My frame is about as long as a 55-57 cm frame and I'm still using a 12 cm stem. This puts a LOT of weight on the front wheel.

My first custom frame fit me great with a 3 cm longer top tube and 1.5 degree steeper seat tube (pushing me even more forward) but I had a rear wheel chattering problem. I didn't even have to pedal - if I went into a hard turn at speed the rear wheel would chatter. I had standard 40.5 cm chainstays. I asked the builder to build me a second frame, same fit, but with the shortest possible stays, 39 cm as it turned out. The 1.5 cm chainstay reduction really helped - the rear wheel has always stayed planted. I actually had the builder modify my first frame to shorten the stays (to about 39.3 cm, the shortest he could do that one). I have yet to ride that frame but I expect a similar result.

So if after you try everything you find that the rear still chatters it may be a problem due to how you fit on a bike. In this case, other than running an obscenely large rear tire, you may have to consider more radical solutions.

saratoga

Traffic circles are almost always off camber for stormwater drainage, meaning that the road slopes away from the turn. Those situations can be difficult to turn through smoothly at higher speeds and you will lose traction at a lower speed than you're used to.

I also agree with tire pressure and the tire becoming more brittle with age even if it looks perfectly fine.

chaadster

This is what I was going to say...aside from the part about crits, since I haven't done one!

milkbaby

Thanks for all the info! After reading the replies, I do think it is happening when I am pedalling through a traffic circle or out of a hard corner. I know that my weight distribution is probably too forwards as I feel like sometimes I get rear wheel slip during a hard jump at the start of a sprint. I'll keep all these things in mind!!! THANKS!!!

gregf83 

Slipping at the start of a sprint is more likely due to a technique issue rather than too much torque. The actual acceleration you undergo during a sprint is much less than what you get pulling away from a stoplight. The problem is you are still pushing down when the pedal gets to the bottom of the crank which causes your body to raise up. When you stop pushing the rear wheel unweights and slips.

Try some high cadence sprint drills in a low gear to smooth out your stroke.

pmt

I see this all the time. Guys inflate to the high number on the sidewall and think that it's faster to run that way, when it's actually inefficient and dangerous.

achoo

Hasn't been mentioned yet: is the wheel true, with no hops?

If the wheel isn't true and/or has a hop in it, that can cause skipping in turns.

milkbaby

Thanks, I will check that too though as far as I can recall, the last time I looked, the wheel was true without any flat spots/hops.

On the tire pressure ideas, I'm pretty sure I am running the lower end of what most people run. Rider plus bike weight is typically under 150 pounds and I run about 88-90 psi rear, 78-80 psi front on clinchers. Or is it too low and leading to a squirmy rear tire?