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PostPosted: Sun Jun 03, 2012 11:16 pm 
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Joined: Fri Feb 04, 2011 4:02 pm
Posts: 18
First time I've ever managed to break a major component on a ride. Kinda surprised it cracked and wondering if folks think it "should have".

Net is I was travelling somewhere between 15 and 17 mph. I was coming up on a ramp into a gas station (cut through on my way home). The ramp up into the driveway has a lip (I've gone over it a hundred times) that's at a reasonably dull angle and maybe 1/2 inch high. I bunny hopped over it, screwed up, and I believe the rear wheel landed on the lip. Doh!

I heard a snap, thought ut oh, applied slight braking, and something didn't sound right. These are 2010 Zipp 303s with Veloflex Extremes with 95 psi in them.

Only cracked on one side, in the brake track.

Pics attached.


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PostPosted: Sun Jun 03, 2012 11:34 pm 
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You can break any rim. You managed to break the toughest one out there. I can see bunny hopping directly onto an edge of concrete as a major problem. It is designed to bottom out hard objects while riding over them. I would expect that the point load weight of a rider after a jump into the air for a hop is too much to ask.


Last edited by Arky on Mon Jun 04, 2012 1:45 am, edited 1 time in total.

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Posted: Sun Jun 03, 2012 11:34 pm 


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PostPosted: Mon Jun 04, 2012 12:14 am 
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Joined: Thu Dec 29, 2011 11:22 pm
Posts: 261
might want a few more psi than that if you're planning on doing that sort of thing again.
if you bottomed out the tyre and the rim made contact with the curb it was bound to break


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PostPosted: Mon Jun 04, 2012 12:19 am 
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303s have a history of cracking, mostly in cross use though.


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PostPosted: Mon Jun 04, 2012 12:25 am 
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Location: On the bike
95psi is kinda low. How big of a guy are you?


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PostPosted: Mon Jun 04, 2012 1:19 am 
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There are people out there riding ( tubulars ) with 90-95 psi with zero issues ( that is under normal circumstances ). ( Myself included, 95F, 100R Veloflex Criterium, 63kg )
I can imagine, that bunny-hopping onto the edge of a concrete lip at an unfortunate angle, with big enough force might present a problem at those pressures, but let's not say " OP your numbers are low ", rather let's say " OP you got unfortunate with that stunt, next time better luck, and avoid such risky moves "

Good luck sorting this predicament out! :welcome:


Last edited by CarlTroy on Mon Jun 04, 2012 1:23 am, edited 1 time in total.

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PostPosted: Mon Jun 04, 2012 1:22 am 
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idk...... at 90-95 psi I'd be worried about the same thing happening if i hit the edge of a drain cover or pot hole at speed


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PostPosted: Mon Jun 04, 2012 1:34 am 
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CarlTroy wrote:
There are people out there riding ( tubulars ) with 90-95 psi with zero issues ( that is under normal circumstances ). ( Myself included, 95F, 100R Veloflex Criterium, 63kg )
I can imagine, that bunny-hopping onto the edge of a concrete lip at an unfortunate angle, with big enough force might present a problem at those pressures, but let's not say " OP your numbers are low ", rather let's say " OP you got unfortunate with that stunt, next time better luck, and avoid such risky moves "

Good luck sorting this predicament out! :welcome:


PSI per riders body size definitely has a role to play in this. If the rider is 50-55kg that is one scenario vs. being 90-95kg. Underinflated tires plus + mechanism on impact creates the perfect storm and leads to this kind of damage.


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PostPosted: Mon Jun 04, 2012 2:13 am 
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Lucky for you excelsports is having a sale on wheels.


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PostPosted: Mon Jun 04, 2012 2:20 am 
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Thank you for that Dr. Obvious :lol:
I gave the OP the benefit of the doubt! I would like to think that the OP knows his weight and uses the right pressures for his weight! Hence i would ditch the term " under inflated " for the time being and call this incident unfortunate. I know i wouldn't say, that my tyres are under inflated at 95,100psi, these are the right pressures for me at my weight. 90,95psi could be the right pressure for OP. We'll soon find out if this is true or not. This was what i was trying to be getting at.

Once again, when i say the right pressure, i always refer to normal, standard riding circumstances, definitely not x-games. I know i wouldn't bunny hop around sharp concrete ( regardless of the psi ) :thumbup:


Last edited by CarlTroy on Mon Jun 04, 2012 2:22 am, edited 1 time in total.

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PostPosted: Mon Jun 04, 2012 2:20 am 
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Joined: Tue Sep 20, 2011 8:15 pm
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Maybe don't ride carbon race wheels as your get coffee/run to store wheels?

Anyway... hub and spokes are still good, so you can have it relaced to a new rim... or just buy a whole new wheel and sell this one on Ebay because some stupid fool will still want it.


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PostPosted: Mon Jun 04, 2012 2:54 am 
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Oh well, looks like I'm the dummy. I weigh 69kg - min printed on the tires is 7bar = 101psi. So I was running the tires a bit too low.

Also went and had a look at the lip. While it's only about a cm high, it is reasonably sharp.

Guess that'll just be an expensive lesson for me.

ps - not a coffee run - never do those on the bike :)


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PostPosted: Mon Jun 04, 2012 3:27 am 
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Joined: Sat Jun 13, 2009 4:02 am
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Location: NoVA/DC
if youre the original owner (and in north america? dunno if that matters), zipp has an excellent crash replacement program. varies from dealer to dealer, but generally 4-500 to have them send it back to zipp, they put a new rim with new spokes on your hub, and turn it around pretty quick.


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PostPosted: Mon Jun 04, 2012 3:30 am 
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I don't think 95psi is low for a tubular. Or clincher. I weigh 185 pounds and run my clinchers at 100psi front and rear. Never had a pinch flat from hitting a pothole or anything else. Use 23, 25, and 28mm tires. I think Cycling News had a story on Paris Roubaix and listed the pressures the pros used. Boonen was around 60psi. 80psi was the highs. Lots in the 60s. They were running wide tires. But 28mm at 60 is probably equivalent to 23mm at 95psi. Zipp 303 wheels were probably used in P-R. They were hitting 1/2 inch high stones at speed.


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PostPosted: Mon Jun 04, 2012 4:26 am 
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"I don't think 95psi is low for a tubular."

Image

http://www.zipp.com/accessories/detail.php?ID=51



Image

http://www.vittoria.com/tech/recom-tyre-pressure/



Lots of opinions and thoughts on this and have been talked about on WW before. Here is a thread: viewtopic.php?f=14&t=67616


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Posted: Mon Jun 04, 2012 4:26 am 


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