F9: Darksiding

As usual an excellent scientific breakdown of fitting a car tyre to the rear wheel on a bike from Ryan

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Interesting article. I have followed the Darksiding story on USA forums for some time and, if I could, I would give it a go. Unfortunately it’s illegal to fit a car tyre on a motorcycle in UK, my friendly MOT tester pointed out the part of the regs which state it is an instantfail if presented for test, and I’m pretty sure it would invalidate insurance.

People who would rather save a few quid than save their lives do confuse me.

Worth watching to the conclusion (spontaneous what?) HANDLING = SHIT

On the UK MOT front (unlikely to change post Brexit) fitting a car tyre to a motorcycle is a Major fail, the relevant regulation being 5.2.3 (a) An unsuitable tyre fitted. Examples of unsuitable tyre include car tyres on solo motorcycles and tyres designed for front wheel use fitted to the rear wheel and visa versa.

I’ve never heard of any Dark Siders fitting a car tyre to their front wheel, I wonder why?

I didn’t have 11mins for this, however it makes sense not to… Motorcycle companies don’t use car tyres for a reason, and tyre companies make them for a reason…

Having said that I remember someone telling me that I shouldn’t have different brand tyres on my SM even though the Avon pxr front and rear (can’t remember rear) combo was superb

Its not different brands but different types of tyre construction. You can’t mix radials, cross ply or bias belted tyres across axels and you can’t mix radials with cross ply or bias belted between axels.

The difference being cross ply tyres have reinforcing belts criss cross from bead to bead across the tyre giving a firm sidewall. Radial tyres have reinforcing cords crossing each other from bead to bead across the tyre and around the tyre circumference giving a firm side wall. Bias belted tyres combine both construction methods with reinforcing belts criss crossing from bead to bead and around the tyre circumference.

Its illegal to mix soft and firm side walled tyres because it will have a diverse affect on the handling characteristics of the vehicle.

Many years ago a friend of mine turned up a bike and sidecar. He had car tyres on that!

Sorry should have said he was giving me advice as to what works best rather than legal/illegal

I was only trying to explain why he would say that and why good handling can be achieved by mixing brands so long as you don’t mix belt construction types. All because tyre construction is a mystery to most motorists whether they motor on two wheels, four wheels or more wheels.

I remember a TV programme back in the 70’s the presenter may have been Esther Rantzen not sure. They took the cameras to the streets to ask motorists about there tyres. The question was 'Are your tyres cross ply or radials? The most popular answer after ‘I don’t know’ was ‘remoulds’