tubulars + valve extenders

kamil1891
kamil1891 Posts: 658
edited October 2012 in Workshop
I've recently bought some tubulars wheels for the track and tyres with that. The thing is that I've blindly bought these: http://www.evanscycles.com/products/col ... 09#reviews valve extenders and having checked how it actually works I don't like them. How you are meant to release the air for example if the tubulars are glued in ? I've also checked the topeak ones that have removable cores but I don't seem to find them anywhere for my 88mm rims. Anyone can help with that?

Another thing is, how well tubulars hold air ? Having pumped the tyres on the rims to 140psi next day it was only 50.. so even worse than latex tubes. Is that normal and would it mean that I have to carry a pump everytime I go to the velodrome ? :D

And finally, do I have to sand the rims before putting the first layer of cement ? I've been advised to use the parktools tutorial but they don't really explain whether that's necessary or not. I've got some sand paper but I don't want to damage the rims by doing something I don't really have to do.

Thanks in advance for advices :)

Comments

  • pinarellokid
    pinarellokid Posts: 1,208
    i spend a bit of time at the velodrome and i see loads of people with track pumps
    so i would personally say yes.
    just check the pressure pefore you set off..

    no big deal, and that way you know they are right..

    cant help with the glue, sanding question, but i would say if your covering them in glue, a little sanding isnt going to ruin them is it.. but it would help the glue to bond better being a rough surface
    Specialized S Works SL2 . Campagnolo Record 11spd. rolling on Campag Zonda wheels

    http://app.strava.com/athletes/881211
  • sungod
    sungod Posts: 17,533
    the extender length you need depends on how long the stems are on your tyres, they do vary, also vittoria have a different system

    you can get longer extenders, have a look on http://www.probikekit.com you'll find 100mm ones for instance

    tubs can lose a lot of pressure overnight, lightweight tubes lose more air, plan on pumping up for every ride - if there're others around i'd think you could borrow a pump easily enough

    on my road tub wheels...

    i use some very fine (000 or 0000 grade) wire wool on new carbon rims, then clean with acetone, alcohol, or additive-free petroleum spirits etc., for metal rims just clean with the solvent

    for glue, vittoria mastik one is good, one coat on base tape, two or three thin coats on rim, leave to dry a day between coats, don't get glue in the valve hole, put final coat on rim and quickly mount tyre before it dries, pump up a bit, align tyre, pump up to max, roll along for one complete revolution with your full weight on it, check alignment and deflate/align/inflate if necessary, then leave to dry for a day
    my bike - faster than god's and twice as shiny
  • kamil1891
    kamil1891 Posts: 658
    Thanks guys, great advice. I've just started applying first coat to the rims and tomorrow I should receive valve extenders with removable cores at the right size :)
  • andy_wrx
    andy_wrx Posts: 3,396
    Removable core extenders have to be the way -the other sort require you to leave the valve unscrewed inside the extenders, and if you want to let the air out you have to poke a bit of wire or similar down iside to open the valve.

    Some people suggest wrapping a bit of PTFE tape around the valve before screwing-on the extenders, but I've never bothered.

    Sungod's method of coats on tub and wheel is what I've always done, works fine but just means you have to wIt a couple of days for your wheels

    Bit late now, but did you try the tubs on the rims before starting to glue ?
    -sometimes tubs are very tight fit (esp Conti !), so easier to fit them dry, pump up to half pressure and leave overnight to stretch a bit, then they go on easier.
  • on-yer-bike
    on-yer-bike Posts: 2,974
    Contis are supposed to left for 3 days at 140 psi on a dry rim before using them.
    Pegoretti
    Colnago
    Cervelo
    Campagnolo
  • kamil1891
    kamil1891 Posts: 658
    Hi all and thanks a lot for the input.

    I left my tubes on the rims for about 5 days until I proceeded with gluing. Regarding the valves I've got the right ones and I wrapped the PFTE tape around the contact screwing points. Works fine.

    However, I've had bigger problems... when i tried to mount the first tube I think I did put too much glue and when the tyre stuck I couldn't move it to align it properly. I have to get it off and I cleaned the rim from the glue etc, but the tyre still has the glue on it. How do I mount that now? Do I scrap the glue somehow or what?

    Now the second wheel.. everything went fine, I've learned from the first one and I did put not as much glue and it seemed to be fine. However, there was about 2-3 cms with very little glue so I've moved it and applied some extra cement on the edges and it is stuck fine. Would it not develop any problems ? Moreover, right at the valve I've noticed that if I look at the rim when it's straight then on one side I can see about 1mm more of a sidewall, so it means that it's not 100% straight. Is it big issue? :)

    Edit: The wheels will be only used at the track, so I dont think there will be problems with overheating from excessive breaking etc.
  • sungod
    sungod Posts: 17,533
    no need to remove glue, to remount, just let the glue dry, then apply a fresh coat to the rim and mount the tyre (which will still have glue on the basetape unless it pulled off after the first try)

    if the glue did pull off of the basetape, i'd touch up just those parts and let it dry for a day before remounting

    when mounting the tyre, you need to apply enough pressure as you push the first bit on (where the valve is) then keep even tension as you move down until you can lift the wheel and pop the last few inches onto the rim, if you don't keep enough tension on for the first part, that can result in a 'hop' around the valve

    simply having the tyre a teeny bit off centre won't make much difference (mine certainly aren't perfect and they ride fine), also, basetape can be off centre, so it's better to use the centreline of the tyre to judge things

    the important thing is to be sure that the tyre is secure
    my bike - faster than god's and twice as shiny
  • kamil1891
    kamil1891 Posts: 658
    sungod wrote:
    when mounting the tyre, you need to apply enough pressure as you push the first bit on (where the valve is) then keep even tension as you move down until you can lift the wheel and pop the last few inches onto the rim, if you don't keep enough tension on for the first part, that can result in a 'hop' around the valve

    I see... so what should I do now then? Looks like I didnt apply enough pressure then and there is more basetape around the valve area than anywhere else. However, the tire seems to stick fine. I deflated it (few hours after mounting) to check for the good connection and the tyre seems to hold well at the edges... I don't want to find myself on the ground as the tyre rolls... I've been already down on Tuesday at the velo as my foot unclipped when sprinting 60km/h+...

    I will sort out the other wheel tomorrow then :)
  • sungod
    sungod Posts: 17,533
    as i said, the basetape is not always even on the tyre, so that alone isn't something to worry about

    also, the valve hole on some wheels has no chamfer, if the tyre has any raised area around the valve stem then there's a chance things to look slightly different there, and it's the area where the basetape overlaps a bit, so again this may cause a difference in appearance

    if the basetape was fully coated, and the rim was fully coated, then when squished together they will bond, minor imperfections in alignment will not affect this

    if you've checked the tyre is well glued by deflating and going around the rim firmly to look for any 'loose' bits, then i'd bet it is well glued, a fully inflated tyre on a glued rim has a lot of staying power
    my bike - faster than god's and twice as shiny
  • kamil1891
    kamil1891 Posts: 658
    Thanks a lot again sungod I really appreciate it. I would not worry much then. Time will tell whether it was glued properly or not, but nothing looks too strange so I left it as it is. The basetape is as close as I possibly could do on both sides and when I spin the wheel nobody at my house at least said that it's not running true :) However, when I glue the next one I will try to put more pressure at the valve hole as I think I could do better with the former one. Anyway, everyone has to start learning at some point and I try to do that as I know that LBS would charge me quite a bit for that job and I still wouldn't be so sure how they did it and whether is safer to ride :)