The best way to mount 8″ trailer tyres is to take them to a tyre fitter. This method is how I did it and I’m noting it for future reference. However a lot of swearing is involved.

First look at the wheels and tyres. The ones I did years ago went on fairly easily. These laughed at me – no way were they going on.

First step is to lubricate the rim and tyre beads with water and washing up liquid. Then jam the rim into the tyre as far as possible. Note: these tyres are distorted from storage; do this on the dished side not the convex side.

First stage of swearing – the tyre will fall out of the rim as often as it can. Clamps and rope can help, although these will get in the way and fail regularly.

I own a few clamps from Aldi. These are not great but are reversible so can push outwards. This is the key to getting the tyre on.

If you get this just right you can stretch the bead over the rim without overly stressing anything. Get it slightly wrong and the clamp falls off, followed by the tyre falling off the rim, so you start again.

Eventually you get over half of the bead on the rim. Things are then easier as the tyre will generally stay in place. You can then continue to use the clamp to stretch the bead and maybe a length of wood to push the bead down past the clamp over the rim.

The other bead is easier as you can kneel on it to push it down. Plus it is held in place by the first bead so it went on much easier.

However, I’ve realised that one of the rubber dojits that hold the valve is perished so one of the tyres probably needs to come off again. ******* ******.

Update 2021-06-02:

I replaced the valve easily by cutting off the old one and pulling the new one through from the inside. Plenty of room to do this without taking the tyre off 🙂

I managed to pump up the tyres using the electric inflator supplied with my car and a big ratchet strap (6 tonnes). Had to tighten the strap around the rim in a few different places to get the seal but the tyre popped into place without any problems.

I was tempted by the ‘lighter fluid and explosion’ method demonstrated on YouTube but (a) I didn’t want to damage myself and (b) I couldn’t see how I would know that the tyre wouldn’t be damaged. These tyres are small, spin fast and I’ve just replaced them as the old ones were damaged so potentially damaging the new ones didn’t seem the right thing to do.