Tubular base shape

[Dead Man]

Howdy

Since getting into tubulars this last year (thanks to membership here for guidance on that endeavor), I've noticed something that I haven't read about - base shape. Some tubular tires have nice round, convex bases, some have angular bases.... likewise, some rims have one or the other, and the different shapes really don't seem to mesh well.

For instance - I got some C24s, which have a concave rim bed, not really thinking about the fact that the Vittorias I've been rolling have an angular base.. the angular Vittoria base fits into the angular rim bed of my EC90s really well. But the first time I mounted up the C24s, I had total failure. One side or the other lifted off the rim and didn't glue down at all, on both wheels. I googled and learned about the broom-handle technique.. this allowed me to salvage the glue-up that day, but I'm still not super comfortable with 'em like that. And what if I try a different tire with the EC90s, and it comes with a convex base? Do I find a long sharp corner to use as a "broom handle," to get those to glue up nice and tight?

So what's the deal with this? Am I just putting way too much stock into this as a "problem," or do you guys buy tubulars with shapes according to the particular rim bed shape you're gluing up?

[ultraman6970]

In my particular case I buy whatever i can find for the right price and take whatever its given to me... All my wheels have several depts in the rim being the flattest one the kinlin tb25... the other ones are pretty much the same.

I have noticed what you say about the shape of the base tape, but all has to do IMO with how much air you put to the tubular before gluing it.

I have put round and anglular (your words) tubbies in the kinlin rims that are the most flat ones I ever seen and never had a problem, so my best guess again, is that probably you are putting too much air to the tubular before gluing it.

Once the tubular is stretched you put glue to the rim and the tubular, put like 20 to 25 psi of air to the tubular... mount it... put 50 psi, try to get the tubular straight, inflate to 100 and do a few more corrections and let it dry a few hours like overnight (anals will wait like 3 days, everybody has different ideas about it)

One of the things I do at around 25 to 40 psi is to put my weight over the wheel and roll it back and forth, that will flat the tape area and will glue it better to the rim, maybe you need to do that.

No idea about the broom technique so cant give my opinion about it, never heard of that. What can help too is to use discartable gloves... for some reason the glue doesnt stick to the gloves home depot gloves I got (nitrile I believe)

You dont have to use a ton of glue either... you know.

Hope this helps.

[ultraman6970]

Is this the broom handle technique??? 1st time I see it... basically the same thing I do but w/o the broom. Wonder of the broom is folding too much your tubulars because is too thin... try w/o the broom.

http://cdn.mos.bikeradar.imdserve.com/images/bikes-and-gear/components/tubular-adhesive/1286818605795-vjnqeinsqn6w-700-80.jpg

[Dead Man]

Is this the broom handle technique??? 1st time I see it... basically the same thing I do but w/o the broom. Wonder of the broom is folding too much your tubulars because is too thin... try w/o the broom.

I don't usually use the broom - I had to do that to get the Vittorias to glue up to the C24s evenly.

I agree that I was using "too much" air pressure, though. With a good match it's no problem.. but with a poor base shape match, filling them up just lifted the base off the rim.

[ultraman6970]

If you want to find the right formula between rims and tubulars well... no comments... but I do believe you are over thinking this way too much, you put the glue.. you mount.. you roll.. more air... fix imperfections... roll a few more times... 80 psi so the tubular gets rounded and let it dry a few hours. Done.

Once the tubular gets 80 psi gets round, the v shape is gone because the tubular gets the shape of the innertube.

Just notice something... are you using wide rims or regular 21-23 mm rims?? 25 mm tubulars too??