Tubular Tire Mounting Question

[m_sasso]

What I am working with: new Fast Foward F9T wheels and new Continental Sonderklasse II tires.

I mounted these tires once and rode them for a short time on our wooden track however I am getting a raised, un-round elevated bump at the valve stems on both the front and rear tires. Looking at the edge of tubular tape relative to the rim edge at the valve stem area the spacing is consistent with the rest of the tire. The mating surface of the tire tubular tape is with out a doubt seated on the rim.

Maybe I am being to critical/particular however as I am riding I can clearly feel the irregularity in the roundness of the tires. Also putting the wheels on my truing stand and looking at them they without a doubt have a raised bump at the valve stem area.

I have a reasonable amount of experience mounting and using tubulars however have never experienced this issue. I have removed the tires from the wheels and I am considering doing some additional chamfering around the valve stem hole, anything else I should be considering before trying to remount the tires towards getting a more consistent round tire mounting and tire rolling surface?

Thanks!

[denapista]

The trick to getting rid of that issues, is to apply all of your weight on the wheel with the valve area of the wheel against the floor. Immediately after applying glue or tape, I roll the the entire wheel pushing heavily with force. I especially focus on the valve area. I usually pump the wheel up to 100psi and do this with all of my force to seat the tire into the tubular rim cavity.. It helps.

[fogrider]

Can't really say without photos...

[BdaGhisallo]

Compare the size of the hole in the rim bed of the valve hole and the diameter of the bulge around the tire valve made by the bunching of the base tape and you'll see the problem.

Tubs have always had that little bulge in the base tape around the valve and rim makers rarely make the valve hole large enough for that bulge to be completely seated within the rim cavity, leading the the tire bulging up and creating the hump you see.

When I used to use alloy rims I would use a dremel and grind out the rim bed valve hole so my tubs would seat better. Now with carbon rims I am less likely to do that on every wheel because I can't be bothered. You won't really notice it that much when riding, unless you ride rollers a lot.

[oldpotatoe]

The trick to getting rid of that issues, is to apply all of your weight on the wheel with the valve area of the wheel against the floor. Immediately after applying glue or tape, I roll the the entire wheel pushing heavily with force. I especially focus on the valve area. I usually pump the wheel up to 100psi and do this with all of my force to seat the tire into the tubular rim cavity.. It helps.

What he said ensuring the valve hole in the rim is allowing the entire valve through. I have also used a broomstick 'roller' right there at the valve, during gluing, to make sure it's all the way down. BUT, with any tube, the rubber base of the valve, that actually sticks to the tube, is thicker..some manufacturers are better with this than others.

[m_sasso]

The trick to getting rid of that issues, is to apply all of your weight on the wheel with the valve area of the wheel against the floor. Immediately after applying glue or tape, I roll the the entire wheel pushing heavily with force. I especially focus on the valve area. I usually pump the wheel up to 100psi and do this with all of my force to seat the tire into the tubular rim cavity.. It helps.

What he said ensuring the valve hole in the rim is allowing the entire valve through. I have also used a broomstick 'roller' right there at the valve, during gluing, to make sure it's all the way down. BUT, with any tube, the rubber base of the valve, that actually sticks to the tube, is thicker..some manufacturers are better with this than others.

Thanks much, appreciate the responses.

I think I mentioned I am not new to tubulars, I did plenty of rolling with my hands on the axel and most of my weigh on my hands immediately after mounting.

Also did use the broomstick roller trick immediately after mounting, I did not want these tires coming off on the track.

A couple of quick pictures of the rear wheel before removing the tire, if you would like to see something in particular let me know. The front tire has been removed from the wheel, however the base tape alignment was much more consistent on the front. On the rear Continental was a bit sloppy with the overlap of the tape when building the tire.

Peter wrote "with any tube, the rubber base of the valve, that actually sticks to the tube, is thicker..some manufacturers are better with this than others."

Yes, I am beginning to believe this is a good part of the problem. I have another set of wheels I mounted up recently, 5 spoke Miche Super Type SPX5's wheels with the same tires, Continental Sonderklasse II tires only from an older batch of tires, no bump.


Compare the size of the hole in the rim bed of the valve hole and the diameter of the bulge around the tire valve made by the bunching of the base tape and you'll see the problem.

Tubs have always had that little bulge in the base tape around the valve and rim makers rarely make the valve hole large enough for that bulge to be completely seated within the rim cavity, leading the the tire bulging up and creating the hump you see.

Yes, did pretty much zero prep on the wheels besides cleaning and roughing up the rim bed before mounting these tires, I am now thinking, I need to get out the countersink bit and do a bit of work around the valve hole.

[Look585]

Being a trackie, you might have some toe straps lying around?

I wrap a toestrap around either side of the valve stem and tension such that the act of inflating the tire compresses the valve area into the rim. This ensures a good glue bond at the valve stem and usually eliminates the "lump".

Sometimes, this results in a temporary "negative lump" (depression) in the tire at the valve stem that will eventually work itself out.

[m_sasso]

A couple more images trying to show how big of a bump I have, really is not that big, however I can feel it, mainly because it is prominent only at the valve stem.

[m_sasso]

Being a trackie, you might have some toe straps lying around?

I wrap a toestrap around either side of the valve stem and tension such that the act of inflating the tire compresses the valve area into the rim. This ensures a good glue bond at the valve stem and usually eliminates the "lump".

Sometimes, this results in a temporary "negative lump" (depression) in the tire at the valve stem that will eventually work itself out.

You are a smart cookie, thanks much, I like this tactic/procedure, never heard this trick before, going to give it a try with the remount.

[bikinchris]

I remember seeing someone place the wheel under a utility table, then put hand weightx on top.

[Jere]

Tiedown strap

Ive been using these for 20 years remember 19 mm tires.
Place strap we’re you crank it down over the valve stem with 120 psi in the tire.

https://www.toolots.com/ratchet-tie-down-strap-2-x-30-3-333-lbs-with-flat-hook-end.html

Jere B

[m_sasso]

Thanks for all the solution ideas, going to do a bit of valve hole bevelling and toe strap on either side of the valve stem with inflation a go.