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Zipp 303 Clinchers - tires rolling off?
Last Post 08/15/2013 04:13 PM by Kevin Burnet. 13 Replies.
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GJanney

Posts:76

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08/09/2013 10:31 AM
This year, I purchased a set of Zipp 303 Firecrest Carbon Clinchers. So far, the wheels have been great. Last week, I took a 90-degree sharp right turn at a relatively high speed. As I rounded the corner, the rear wheel felt like the tire was going to roll off for a moment – it was a very unsettling feeling. I checked the tire and it seemed perfectly seated afterward. I rode it a couple days later and seemed to feel something similar, but not as pronounced. At this point, it could be psychological, but I wondered if anyone else has had similar experiences with these or any other carbon clincher wheelset. The tire is a Continental GP 4000 with fewer than 400 miles on it so my sense is that it should stay seated.
stinkyhelmet

Posts:83

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08/09/2013 10:35 AM
Sounds like the tire sidewalls were rolling over. This happens with either low air pressure or high side forces on the tire (like when turning aggressively) or both. How much air were you using?
GJanney

Posts:76

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08/09/2013 10:39 AM
I filled them to 110 PSI at the start of the ride. I am 200 lbs., and cornered pretty hard so maybe it is due to my weight and the aggressiveness of the turn. Maybe now I am simply psyching myself into thinking I'm still experiencing the problem, but I sure would hate to have the tire roll off if there is an actual problem. The tire looks fine, so I'm not quite sure what to look for to inspect for any issues. Thoughts?
Pin0Q0

Posts:229

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08/09/2013 11:10 AM
GJ try pumping then up to 130 psi. 110 is OK to roll around the country but not for high speed cornering especially with a centrifugal force of 200lbs. it will prevent better protection against tube pinch if you hit a small pot hole. Just stay away from painted road lines.
Oldfart

Posts:490

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08/09/2013 12:34 PM
Check the spoke tension. I bought a pair of Zipp 303 cross wheels a few years back. I heard creaking at one point when I used them on my road bike and noticed that if I held the brake on while leaning on the fence astride my bike and pushed on the pedals that the hub was rotating within all them loose spokes. Seriously low tension. Poorly built wheel.
Keith Richards

Posts:759

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08/09/2013 02:19 PM
I am with OF...I would check spoke tension.

Any tire at 110 should not feel squirrelly under cornering.
----- It is his word versus ours. We like our word. We like where we stand and we like our credibility."--Lance Armstrong.
zootracer

Posts:322

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08/10/2013 01:00 PM
Not Zipp carbon clinchers nor Conti GP4000's. Back in the day I used Vittoria Open Corsa's EVO with Mavic OP's . First ride I inflated them to 110 psi and they were really squirrely when descending on curvy roads. I inflated them to 130 and all was well. Unfortunately at 130 psi, it made my EVO's wear out fast. Best I could get was 1000 mi on a rear tire.

I weigh about the same as you and like the Michelin Lithion, fold up, 700x25's. Best training clincher for the buck. Can be found for around $30, if you scroll around. But maybe you don't want cheap training tires with a carbon rim...I'm a budget rider...

Master50

Posts:252

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08/10/2013 09:44 PM
I run my Vittoria 25 at 100 and the 23 at 105 much nicer ride than higher pressures but I am 170 lbs.
GJanney

Posts:76

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08/12/2013 05:08 PM
Okay, so the story continues....

In April I 'jumped' the chain over the cassette in-between the cassette and the wheel. Bent two spokes slightly, and had those replaced with spokes from Zipp. My LBS replaced the spokes and tensioned the wheel. Apparently I should have gone back in to have it checked and re-tensioned after a couple hundred miles. The guy re-tensioned it and said it was almost 30 nm under-tensioned.

Will take it back out tomorrow and give an update post ride. Hopefully now that the spokes are tight again, I shouldn't have the issue.
nightfend

Posts:48

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08/15/2013 12:39 PM
I would not recommend running more than 120psi with carbon clinchers. In fact, most manufacturers mention not to exceed this psi level.
Entheo

Posts:317

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08/15/2013 12:59 PM
there was a good discussion about PSI on the old forum a couple years ago. studies and consensus was that 110 was optimal; anything more than that didn't reduce rolling resistance, increased harshness of ride and possibility of pinch flats. i'd need some convincing that one could roll their tire at 110 psi.
Orange Crush

Posts:1251

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08/15/2013 01:02 PM
110 psi, how many bars is that? :-)

my road tires have a pretty narrow recommended min/max range (yes a min pressure is specified): 8-8.5 bars. I use the min of 8 bars.
Sweet Milk

Posts:93

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08/15/2013 02:38 PM
Optimal tire pressure depends, among other things, on rider weight. From Michelin's website:

"Michelin engineers have found that there's a certain amount of deflection in the tire profile that's optimal for balancing grip, efficiency, comfort and durability. That deflection is based on the tire's construction and the weight of the rider. Obviously, your style of riding can have an effect too, but the chart below should give you a reasonable guide of where to start when experimenting to find the proper tire pressure for you."

They recommend that riders above 180# inflate to the max pressure indicated on the sidewall (in my case 109 psi) - Obviously you should not exceed the design specs for your rims.

And yes, they do also specify a minimum pressure, among other things to avoid the unstable feeling due to excessive lateral flex.
Serotta94

Posts:25

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08/15/2013 04:13 PM
I bet you were almost folding the wheel. I'd belive that more than a tire collapsing at 110psi.
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