Tuesday, 4 August 2020

Lessons learnt fitting bike tyres

I don't have to fit bike tyres very often so I am not an expert. Each time I do, I have to remember what I did last time. Sometimes years apart!

This time I was fitting some 29" Schwalbe Hans Dampf Supergravity tyres to a couple of different rims. Fitting them did not go to plan, so I have learnt a few things:

1. Tyre leavers are for getting tyres off not usually for putting on

I've fitted other makes of tyre and was able to force the tyre on the rim with just a bit of effort. The Schwalbe's, I've just fitted, were more difficult.
One side goes on reasonably easily, with a bit of effort, but despite positioning in the hollow, as best I could, I just could not get the other tyre bead over the lip. I resorted to tyre levers but they just scratched the rim and I felt like it was only going to work if I had three hands.

The solution I eventually worked out was that if I manoeuvred the rim to the corner of my bench and forced down on the tyre I was able to get it most of the way on. I then just needed to use a single plastic tyre lever, in the centre of the remaining short length, while pulling the tyre down with the other hand to hold it on the wheel. The single tyre lever in the middle was then enough to  flip it over the edge. Still tough but worked.

I have since managed to fit them without the tyre lever but I needed to be brave, and get it setup just right, to be able to put pressure using both hands to pull the whole tyre down so the bead popped over.

I bought the Supergravity variant of the Schwalbe, Hans Dampf, tyre because it has the toughest sidewalls. I guess that has a disadvantage when trying to fit them!

2. Put the tubeless tyre sealant in AFTER the tyre has been fitted
It was a lot harder struggling to get the Supergravity tyres on the rims whilst also trying to prevent all the sealant pouring out.
I gave up on that idea, emptied out the sealant before fitting the tyre.

Once fitted and inflated to pop the bead on, I used a large syringe to inject the sealant through the valve tube.
This also has the advantage that it is possible to check that the tyres hold pressure without the sealant masking poorly fitted tyres.
The tyre sealant, in my opinion, is for punctures.

3. It's better to replace rather than repair tubeless rim tape
Changing the tyre was the result of a 3" nail. It also punctured the rim tape through to a spoke nipple and nearly punched a hole in the inner trough. I thought it would be simple enough to patch a section of rim tape over the existing. After one ride the tyre had deflated!
Very disappointing. After the struggle to get the tyre on the wheel, I had to do it all again. This time I stripped off the old rim tape. It came off very easily, so I should have done that the first time.
This time, with a completely fresh install of rim tape, the tyre has stayed fully inflated.

4. The tubeless rim tape does not have to stick
I used Stans No Tires Tubeless Rim Tape on the first wheel I did. That stuck well. I did exactly the same from, the same roll, on another rim and it would not stick at all. I'm guessing it's something about the material used to coat the inside surface of the rim.

That said, it does not have to stick very well. I managed to keep it down just enough to get the run round the rim. I then fitted the tyres and inflated them. As the tape was a seal from bead to bead, I had no trouble inflating the tyres.
This only works if the rim tape is the correct width for the tyre a mm or two greater than the internal width of the rim, so the bead holds tightly on either edge.

The wheels are installed and tested and I am pleased with the results.
By writing those notes down, hopefully I will remember them for next time.


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