How can pressurizing a tire when its not on a rim damage it? makes no sense to me, the tube is totally ocntained by the casing.

Road Fan

Tubulars can turn inside out, with the basetape where the tread is and tread where the basetape is. This can damage the basetape. At least that is my understanding.

Yes, tubulars WILL turn inside out, because the tread constrains the carcass where it is attached, and the basetape will therefore elongate, but has anyone got an example of damaging the base tape? The stuff is a pretty loosely woven linen twill, in cotton tires. It has give.

I've pumped them up exactly this way many times to test for airtightness with no problems that my dumb eyes can see. I'd like to hear about an example, so I can learn something.

Road Fan

Road Fan, this is exactly what I do, too. I don't pump to 110psi, but 60 or so has never bothered any of the dozens I've done.

What tubular's use removable valve cores? This is what you need to install the tufo sealant, right? Or are you guys using a syringe to inject it into a puncture after a flat?

This seems like good stuff. I want to be able to run it, so I want to make sure I have all my ducks in a row.

I know the Tufo's do :)

When the tire is on a rim (clincher or tubular), the inside diameter stays the same as you inflate it and the outside diameter increases. The casing of the tire is cloth and the bias of the threads are oriented to allow this kind of stretching.

When the tire is not on the rim, the outside diameter (the base tape) stays the same and the inside diameter decreases as you inflate it; this is the opposite of what the casing was designed to do and it can be damaged if you inflate it too much. You might not notice but some of the cords could be torn and you'd have a problem later on. Inflating enough to just make a good gluing surface isn't going to be a problem of course.

The base tape damage wasn't my comment, but I have seen the edges of the tape pucker up after inflation off-rim. Makes for some fun experiments with old tires.

i just made a little order yesterday. i got some vittoria evo corsa tri tires. hoping that wasn't a mistake judging by their 190 gram weight verses the 270 gram weight of the corsa cx that they didn't have in all black...hence the reason i got the tri's. i have high expectations of the ride quality. 290tpi casing and a latex tube plus a punture belt in the tread. i've been scrubbing my tires if i ride through trash so i think i can make them last. i think they were under $50 a tire, same as the corsa cx's from the same place.

tubs
 

What is the proper way to fold a pre-glued tubular that one is going to carry along for a spare tucked under the saddle?

Enjoy my photo sequence.

LINK

Forward to all your friends.

http://lh4.google.com/DiabloScottsBi...ding%20003.jpg

Nice shot of a properly folded spar Scott.

Also keep the spare in a bag so the protruded "ends" of the sidewall remained protected from the elements and from that ever so stylish Alfredo Binda laminated toe clip stap used to secure the spare beneath your saddle.
Oh yes and keep the cap on the stem to as pictured to prevent chaffing.
Cannondale used to make a wonderful "tire sock" for those spares.

thanks so much for the informative photo sequence. I don't think it would have been easily explained in a soley text format. well done!!

Thank you for the sequence. I have saved the link :)

First, I did say it elongates. You seem to be saying it's not designed to, but I think we don't know that.

I also find it hard to see pucker as damage.

You hypothesize that carcass threads may be damaged, but is there any evidence of that? Any blowouts under the tape? Any hanging threads?

At least not in my experience.

Road Fan

This thread is for tubular tips and advice so I won't engage in any more hypothesizing.

But I do contend that pressurizing a tire OFF a rim will be more damaging than pressurizing a tire ON a rim. And I do have some anecdotal evidence - I once did an experiment where I pressed up a tire off rim to see how high I could get it and it exploded (casing failure) at 120 psi. I had had that same tire pressed up to well above 120 psi on a rim without explosive results.

Anyone attempting to replicate this experiment is advised to wear hearing protection.

why didn't t you say so before? I'll BET it was loud! Was the breach near the seam under the tape?

Road Fan

I don't remember exactly - what I remember was the stitching from my patches held up fine!

Enough late night typing for me!

I think we really can't know if the carcass stresses are identical or not, because we can't really see the cross-sectional shape. The carcass is self-supported while inflated off the bike, so it pretty much must be circular since the only forces are internal pressure which is uniform in all directions, and carcass tension, which is again uniform due to continuity. We can't see how the shape might change after tire mounting. There is certainly stretch required to get the tire on teh rim, but we don't know if there is stretch remaining after the tire is aligned and pressurized, 'cuz we can't see it. But I agree that the rim/cement combination is adding a force to the tire, otherwise the glue wouldn't hold the tire.

Personally I don't think we can know the answer to this question - happens a lot in engineering! Now with a shape-measuring machine ... but I don't have the spare $50k lying around!

If you have to be conservative about your tires, maybe it's best not to apply full stress to an unsupported tire, but if I was the manager of a tubular design team, I'd at least investigate providing full reliability in the full-inflation unsupported case as in the full-inflation mounted case.:)

Road Fan

Road Fan

So.. let's say that I've got my spare tire pre-stretched, and I'm ready to glue it and fold it up so it can sit on the bench as the 3rd string quarterback (Goo Sealant is 2nd string).

Do I apply the glue, let it harden overnight, then fold?

Do I apply glue, let it harden to a 'tacky' feeling, then fold?

Or do I apply glue, then immediately fold?

Probably a silly question, but I'm a total tubular newb, BTW

I think the technical term is now "tubular newbular."

On pregluing and folding, I'm a tubular newbular not a folding oldie. I generally carry spare tires with old glue, rather than a pre-glued tire, though it should be a better mount with a pre-glued.

Road Fan

did I actually just coin that term? I've never heard or read it before, but I have been known to pull things out of the ether.

Apply a thin, even coat over all the basetape of your pre-stretched spare.
Then allow it to dry to a tacky state, which only takes 45mins- 1 hr and fold as shown by Scott.
Do keep the stem cap on to prevent the metal end from rubbing against the sidewall and NEVER just tie it under the saddle w/o covering it. (I know it looks cool but you need to protect the sidewall casing from abrasion by the strap.)

Good luck and please post on how you like the ride of tubulars!:)

Yes you did, but I liked it!

Road Fan

Thanks for the advice! My wheelset won't be coming for another month so it'll be a while. Gives me some time to pre-stretch'em..

Totally Tubular Tuestion: sorry if this is answered elsewhere, it was not immediately easy to find and I think I've heard different answers on this.

I am removing a good tubular from the rim, to replace nipples and spokes. When I put the tubular back on, do I need to apply more glue, or is the base of glue already on rim and tire sufficient?

i wouldn't advise re-installing the tyre without any fresh glue, however,....unless the old glue is dried out, a light freshen-up application on rim & tyre is usually all that's necessary

Bump, finally getting around to gluing my first set of tubulars, this weekend! I have an old set of GP4 rims, well loved and used, the rear I just pulled the old tubular off of as I didn't trust it's condition, and I have a new set of Vittorias here.

Now for the question: how dry is too dry to let old glue remain in the rim without stripping it down? The rear wheel hasn't had a tire on it in a while, but the glue is still tacky to the touch. Enough to make the carpet or a towel stick to it if left for any length of time. Front wheel is much the same, had to use a reasonable amount of force to pull the old tire off. Should just a light coat of new glue on the rim be sufficient?

Yes, light coat is good.

Tacky is still usable. Dry & crispy - no.

Cool. I'll hopefully have a road worthy set by the end of the weekend. Get a few miles on them next week in the evenings on my after-work rides.