ACB10 questions

[Matt Seabrook]

And let's face it, how many purpose built racing cars (which aren't constrained by specific wheel / tyre size regs) do you see with the same tyre size all round ??  Not many.   Which implies there is a benefit to having larger tyres when they're needed.

They also have the benefit of tyre warmers... and bigger tyres take longer to warm up.

I talk from the vantage point of almost complete ignorance, but I'd have thought that getting your tyres hot asap would be pretty important when sprinting.

For what it's worth I've just fitted narrower tyres to my 130bhp 'Blade going from 205 to 185 all round. Wider tyres are also more likely to aquaplane IMHO.

And if you dont have enough power wider tyres will slow you up due to greater rolling resistance. May have been a good move then    

[Nick M]

Actually very few race series have the benefit of tyre warmers.  In cars, the only series I can think of which allows tyre warmers is F1.

And there's different types of heat generated by tyres - wheelspin generates a thin layer of heat in the surface of the tyre.  Lateral load creates a more even heat across the tyre (and you can use the variation in tyre temps to see how the tyres are working and if the suspension needs tweaking, but that's a whole different kettle of fish).

Soft compound tyres will also warm up quicker, partly because of surface heat due to friction but also because they will work the sidewalls harder more quickly, hence generating heat.

I doubt that the relatively short duration of sprint runs is anything like enough to get a list 1A tyre properly warm, let alone hot.  It took me several hard laps on a circuit before I would see much evidence of heat in my road tyres.  Slicks were another story - two or three laps and they were nicely up to temperature.

Aquaplaning is another discussion for another day but I don't disagree with your comment that narrower tyres are probably less likely to aquaplane, although tread pattern is a rather important factor in that.

[Blatman]

Aquaplaning is another discussion for another day but I don't disagree with your comment that narrower tyres are probably less likely to aquaplane, although tread pattern is a rather important factor in that

Maybe...

ISTR an article in Which Bike some years back, where the journo's were testing the ABS system on BMW motorbikes. The premise was a soaked piece of tarmac, a reasonably speedy approach, and grab a fistful of front brake to see if you'd fall off with the ABS, and what sorts of stopping distances were achievable compared to a non ABS'd bike. To show the system worked regardless of tyre condition, they fitted plenty of road tyres from new to fecked, as well as proper race wet, and a proper race slick. The surprising discovery of the day was that the stopping distance of the slick was *much* shorter than the road tyres, and was beaten only by the race wet. So I would suggest that compound is as important as tread pattern in maintaining grip, even in the wet... maybe...

[timd]

Wouldn't the more rounded profile of a bike tyre help a lot in this though - making the tread pattern less critical (for this simple example) than it would be on a car?

The squarer section slick car tyre must have more chance of riding up it's own bow-wave than a bike one..

Hmm. I know what I mean, don't think that's very well explained though!

[Nick M]

Hmm. I know what I mean, don't think that's very well explained though!

I understood what you were on about     And I'm inclined to agree because the shape of bike and car tyres is very different.

[Blatman]

Very true, but I would suggest that under braking, the tyre might be deforming enough to produce a contact patch that *might* equal a cars for the weight transfer/weight/kinetic energy equation... maybe. No argument on that though, I'm sure the tyre shape may well be helping.

[Matt Seabrook]