Vittoria tubular CX question

Discuss light weight issues concerning road bikes & parts.
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ricorob
Posts: 50
Joined: Thu Feb 02, 2012 9:25 pm

by ricorob

Just started riding tubulars again after a 15+ year hideous. I used to ride conti spinter 250's, but I just mounted some CX's. I've noticed a couple of comments about the Vittoria's usually having a hump at the valve stem. Mine have this as well. Is this just a Vittoria issue because of thick base tape, or do many current day tubulars exhibit this issue? Kind of a bummer to not have a nice round tire.

kevhogaz
Posts: 222
Joined: Fri Aug 05, 2011 5:18 am
Location: Arizona

by kevhogaz

In the bazillion page tubular thread, several people mentioned this, with various brands of tires. The solution was either, enlarge the hole in the rim, cut away some of the base tape at the valve stem, or live with it if it's not noticeable when you're riding.

by Weenie


Guy
Posts: 362
Joined: Wed Dec 20, 2006 5:25 pm
Location: Pays De Galles

by Guy

It isn't noticeable once you mount the tyres.

kevhogaz
Posts: 222
Joined: Fri Aug 05, 2011 5:18 am
Location: Arizona

by kevhogaz

Guy wrote:It isn't noticeable once you mount the tyres.


I never noticed the "hump" on my Schwalbes, so I just left it alone.

ricorob
Posts: 50
Joined: Thu Feb 02, 2012 9:25 pm

by ricorob

I read the enlarging the valve stem hole solution, but I don't want to void my wheel warranty. I just mainly wanted to know if the hump is a common theme. You'd think when you spend this kind of cash on a tire it would be round. Of course, I can't say it's noticeable while on a ride.

kevhogaz
Posts: 222
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Location: Arizona

by kevhogaz

I've only mounted one set of tubulars, so I really can't say if it's normal or not. The set of Vittoria's waiting to be glued on my carbon wheels, don't show much of a hump at all.

5shot
Posts: 171
Joined: Sat Nov 13, 2010 7:46 pm

by 5shot

FWIW, Vittoria Corsa CX are the only road tubulars I use and I have never experienced this issue. I suppose it may depend on the rims you use and mounting technique. Or, it could be pure dumb luck.

kevhogaz
Posts: 222
Joined: Fri Aug 05, 2011 5:18 am
Location: Arizona

by kevhogaz

5shot wrote:FWIW, Vittoria Corsa CX are the only road tubulars I use and I have never experienced this issue. I suppose it may depend on the rims you use and mounting technique. Or, it could be pure dumb luck.


These are what I'm mounting on my carbon wheels. No noticeable hop, at all. The Schwalbe's I have mounted, have a very slight hump, but it's not noticeable when riding.

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tommasini
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by tommasini

I've mounted dozends of the older 290 tpi and now about a dozen of the 320's. Never had a buldge at the valve.

Just one thought - when mounting we all have to start by first inserting the valve stem. But from that point do we all pull hard to stretch the tire away from that starting point (and supporting the wheel accordingly) so the tire will have fairly even tension all the way around the rim? If you don't tug on it then the tire around the valve will have less tension on the casing there and a whole lot on the area 180 degrees from the stem. Might be a part of the issue.

thisisatest
Shop Owner
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Joined: Sat Jun 13, 2009 4:02 am
Location: NoVA/DC

by thisisatest

tommasini is correct. his explanation is the most likely scenario. ive reglued a "lumpy" vittoria (more common on those due to the extra stretch allowed in its casing IMO) that had just been mounted by my mechanic coworker and it would sit much flatter with the proper initial pull.

fdegrove
Tubbie Guru
Posts: 5851
Joined: Tue May 03, 2005 2:20 am
Location: Belgium

by fdegrove

Hi,

+1 and +1.

Around the valve stem there often is a physical overlap from the base tape being pulled over the stem to be glued down on the other end. It's a safety measure so the base tape won't come of.

Add to that the extra stitching required to close the tub's envelope around the stem and you'll end up with some more material around it causing the initial hop.

When you're ready to mount the tub push it down the valve hole firmly first then slowly work your way down to the opposing end. If the job's done right and the mounting is finished by a session of "weighted"* rolling of the wheel and highly inflated tub over the floor then no hop will occur. Not one worth mentioning anyway.

* Kind of heavily leaning over the wheel and pushing it against the floor full circle so all of the air that ended up trapped between the tub and rim is pushed out. It's just one way of doing this, there are other methods as well.

It's not exclusive to Vittoria tubs, they just get the blame more often that's all.

Ciao, ;)
Being a snob is an expensive hobby.

Bridgeman
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by Bridgeman

I've never experienced any hop, but I do hear glue clicking every revolution, and its origin seems to be at the stem area.

Guy
Posts: 362
Joined: Wed Dec 20, 2006 5:25 pm
Location: Pays De Galles

by Guy

Bridgeman wrote:I've never experienced any hop, but I do hear glue clicking every revolution, and its origin seems to be at the stem area.


Use a square of electrical tape, pierced by the valve, to stop the rattle.

5shot
Posts: 171
Joined: Sat Nov 13, 2010 7:46 pm

by 5shot

Bridgeman,

That's not "glue clicking" that you hear. It's the valve stem clicking against the rim. The cure, as noted by Guy, is to place a square of electrical tape over the valve stem and down on either side of the rim.

by Weenie


fdegrove
Tubbie Guru
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by fdegrove

Hi,

Or push a cm or so of heat shrink tubing of the corresponding inner diameter over the stem just past the core. The silicone type (not the polyolefin one) deadens the sound nicely and stays in place if you heat it up a bit.

I'm aware I must be the oddball to have that kind of stuff at home, audio hobby ya know... :wink:

Ciao, ;)
Being a snob is an expensive hobby.

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