I thought I had moved away from using tubs, but I had second thoughts about them after I decided to rebuild the wheels on SB5794 with some MAVIC GP4 rims. So using GP4 rims and having no choice, I’ve been dragged back into the process of prepping rims and tubs, and the smell of rim cement is floating around the workshop while I’m picking dried cement from my finger tips! The memories are flooding back…
I even treated myself to a new pot of Continental rim cement – although I think I got the size wrong and this new pot will probably last a little while. I’ve gone for Vittoria Rally tubs, as they are cheap and they are good – and I also have a couple of used Rally tubs I can carry as spares. The new tubs have been inflated and fitted dry to some old MAVIC MACH 2 CD 2 rims, to stretch them for a couple of days. They were good and tight but my thumbs did manage to pop them over the rims.
And this brings me back to the old process to prepping everything. I guess most riders and mechanics have their favourite methods of gluing and fitting their tubs.
While I’m stretching the new tubs on some old rims for a couple of days, I’ll apply a few thin coats of cement to the rims. A thin coat of cement that is allowed to dry and then followed by two more coats, each one allowed to dry before the next is applied. The best place to do this is with the bike in the work stand so both wheels are free to turn.
After a couple of days, the new tubs can be removed from the rims being used to stretch them; I inflate them just enough to pop them inside out, and the base tape can be coated in cement before leaving them to hang on the work stand to dry.
When everything is ready and with a fresh sticky coat of cement on the rims, the tubs can be fitted. Starting with fitting the valve, fitting it nice and straight, pull the tub down on each side of the rim with your hands until you have a few inches left to flip over the rim – lift the bottom of the rim up and push the last bit over.
While everything is still sticky, spin the wheel and correct any wobbles in the tub by lifting and re-seating. When everything looks good, inflate up to your psi and leave to stand and dry, just remember to clean up any cement that might have worked its way onto the rim braking surface.
There isn’t really anything else to do… other than ride them. The weekend is in a couple of days, the weather looks ok, perfect!