[martinot]

I've had these wheels since brand new (2012 model) and just started using them more frequently. I am experiencing some rear wheel flex while powering up the climbs or sprinting. I am not a super powerful guy but still can press on the pedals and it's puzzling why the damn wheel flexes like that. The frame is super stiff (no wheel flex while using other wheels). Brake pads rubbing with the clearance of approx 1.5 mm. I cannot believe this is normal. I am wondering if anyone else has had similar experiences; I'll check with the dealer tomorrow.
The wheels are very nice on flats and rollers but any kind of climbing and a finish line sprint is a not super coolio now

 

[r1lee]

Are you sure it's not the litespeed? That was my concern when I first bought the bike, but since its winter here I've had no chance to take it out. I talked to another forum member before you responded to me last time, he got rid of the c1r because the bike would flex when he put down the power on sprints. Aside from that, overall the bike was fantastic.

I ride the 303 fc clinchers and no problem with flex. Was 195lbs now slightly above 170.

 

[martinot]

Are you sure it's not the litespeed? That was my concern when I first bought the bike, but since its winter here I've had no chance to take it out. I talked to another forum member before you responded to me last time, he got rid of the c1r because the bike would flex when he put down the power on sprints. Aside from that, overall the bike was fantastic.

I ride the 303 fc clinchers and no problem with flex. Was 195lbs now slightly above 170.

I am fairly sure it's not. With Reynolds DV46UL-C I have no flex issues on the same frame. I might install the ZIPPs on my Jamis Xenith SL and see what happens there. Will keep posted. (if it indeed is the C1R frame it will be returned and a BH G6 will be on order as the aero definitely does the trick)

 

[carlislegeorge]

All indicators point to wider rim width as the root cause....

 

[LouisVuitton]

It's not the zipp hoop that's flexing, it's your hub/axle that's flexing. The zipp hoops are extremely stiff

 

[ergott]

Check for play in the hub and make sure the bearings are good.

 

[jaffar]

i have had the same rim rub with Zipps as well, but not with dura ace wheels that have a lower spoke count. i have ridden the stock 18/24 spoke zipps and also a pair of 24/28 zipps and the higher spoke count made a huge difference in lateral stiffness. however Zipp claims that their stock wheels are very stiff and say that the frame is what's actually flexing.

 

[aclinjury]

check for freeplay at the hub by wiggling the wheel side-to-side with your hand. If there's freeplay, just tighten the bearing preload a tad.

 

[martinot]

Thx guys. By laterally pressing on the wheel (in the brake caliper area) it definitely flexes and indeed the play seems to be in the hub\spokes rather than the rim itself. The hub might be it - I will adjust the preload later today and re-check. The frame width is definitely fine - the rubbing occurs only against the brake pads and increasing the clearance is just not a solution - the main is not the rubbing but the stiffness of the system - I hate to be racing/riding on noodles Will post the results of adjusting preload later - hopefully satisfactory

 

[nhluhr]

It's not the zipp hoop that's flexing, it's your hub/axle that's flexing. The zipp hoops are extremely stiff

The rim itself might be extremely stiff but when paired with only 20 spokes, they aren't going to be super stiff as a wheel, given the zipp rim's tension limit of 100kgf. The 303 FC is stiffer than the 404 FC despite the 303 having a shallower profile. The extra 4 spokes make a big difference.

If you want a really stiff 404, you should get it custom-built by wheelbuilder.com with one of their exclusive 24h drilled 404 rims.

 

[ergott]

Tension does not equal stiffness.

Wheel Stiffness Test

 

[martinot]

OK, So I fiddled a little with hub preload and is seamed to be properly set and after the check and re-adjustment the wheel still flexed easily while applying even minimal lateral force. I took it to the dealer and they rechecked the hubs and spoke tension and after making some corrections the wheel is definitely not flexing as much. As a matter of fact at today's race (no serious hill climbs but power sprint) I have not noticed any flex (during the spring the excitement was so huge that I would not have noticed it anyway :blush2. Will retest during next training hill climb. The tech at the dealer mentioned standard "we did a little bit of everything".
Nice wheel stiffness test data - looks like most wheels flex at least 1mm. I think this is about where I am now (using very non scientific test method)
Thx all