Thursday 12 August 2010

gluing cross tubs


Original post:

It's that time again. Gluing time. Tub devotees are either re-gluing old tubs or gluing up fresh ones. Helping friend and tub newcomer Stef the other night with his quartet of new Rhinos on handbuilt old school rims was a joy - passing on a skill that many baulk at for its mess and difficulty.

Well, we only got a little glue on ourselves and none on the sidewalls, so it was a pretty neat job really. I did the first and Stef got stuck in (sic) on the second and third. I sent him home, ready to fly solo on the last.

So to all of you thinking about it, or fretting about it, read on. I posted the following back in August 2008 but it is still relevant now. I have updated a few of points from then but the basis is still, and will continue to be the same.

Opinions on gluing cross tubs are as numerous as conspiracy theories for 9/11. I have had a few requests on how to do it, so thought it might be a timely point in the seasons preparation to put some thoughts down.

There is no hard and fast method that one has to use, though most of the accepted methods overlap in many areas. In the end it's best to use what works for you - if you have confidence in what you have done, it will save time on the course and avoid skin-threatening moments.

For a great insight from a Euro pro racer, Greg Raine, scroll down for post entitled Sticky Fingers

Stu Thornes' ( Belgian method – this is slightly more controversial as some people suggest that no Euro/Belgian mechanics are doing this. Either way it is fast and the tires seem to stay on very well (from personal experience)

My method is set out below and is adapted from Simon Burney’s book as well as advocated by Richard Niewhus who owns and makes Dugast:

1. Lightly sand new carbon rims/lightly sand and clean old rims

2. Put new tub on old tub rim , inflate and leave for a few days to stretch. DO NOT inflate above 50 psi or it may explode. I have heard horror stories about people using 90 psi and wondering why their new Dugasts went pop – they are not designed to run much over 50 psi! While stretching, apply Aquaseal or SeamGrip to proof and protect the sidewalls. DO NOT miss this out - yout tubs will rot and look tatty very quickly. It may not work so well on non Dugast and FMB eg Grifo with a different material for the sidewall to the tub.

3. 1 thinnish layer of glue on rim (Vittoria or Continental) – leave overnight

4. 1 more thinnish layer of glue – leave overnight. Ideally do 1 more layer as well to be sure – leave at least 8 hours to dry as always. That's 3 layers.

5. Put 1 layer of glue on base tape allowing it to soak in as much as poss. When dry after an hour or so put back on old rim to keep stretched. Leave 8 hours again to cure.

6. When you have done all this (phew) then you are ready to assemble – put a final layer on base tape (no more than 2 as it stiffens the tape too much) followed by a final layer (thickish) on rim. Be generous and concentrate on the edges. You glue the base layer first and let it tack up while you glue the rim, as it creates less mess handling the tub and is easier to center the tub on a wet glued rim. Leave no more than 5 mins max and put tire on rim.

Careful – check the tread direction on the back wheel BEFORE you put it on as you do not want to take off again. Place valve in valve hole, and pull either side of tire outwards before settling on rim. Dont put the bare sticky rim down on your floor or carpet - aside from any grief you might get about this, you can get dirt or fluff that will compromise the bond. Check valve is not twisted to side.

Continue to pull tire on rim trying not to get glue all over you and all over side wall. If it has been stretched enough and taken off rim at last minute then this should not be too much of a struggle. I use feet without shoes to hook toes over bottom of rim whilst pulling tire on at the opposite side. Centre tub gently and bit by bit, so base tape is evenly visible around the rim on both sides.

7.Now inflate to 40 psi or so and roll tire with weight across floor to help push tire onto rim. You can also roll the deflated tub gently along the length of a broom or mop handle. Take care not to squish the tire off centre. The edges are where the tire sticks, not so much the centre so always glue the edges well and pay them attention. Leave at least 24 hours before riding.

Done. It is not as bad as it sounds once you have done it a couple of times and got well organized. Time and patience are the key and I have not rolled tires that have been glued on with multiple layers over several days and with love and attention.

Reward yourself with a Duvel, Vedett, Chimay or similar Belgian brew. Always more fun with a Euro cross race playing on DVD in the background.

Note: I won't be taking responsibility if your lovingly glued tubs come off at any point. Check them yourself before riding each time.

1 comment:

Thom Kneeland said...

I always like to let the second coat of glue on the tire dry up a bit and put it on the stretching rim while I put the last layer on the rim. I leave it on and inflated until I'm absolutely ready to put the tire on the wheel. A quick deflate and then I remove it from the stretching rim and it immediately goes onto the glued rim. I find by doing that it is super easy to go onto the wheel since the base tape doesn't have the ability to shrink back up as it dries.