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· Circuit Owner
5,961 Posts
Discussion Starter · #1 ·
I was wondering - as somebody who has never raced in an endurance race - in endurance racing do soft tyres "go off" over time?

I'm talking 4 hours plus racing with driver swaps here.

I see the debate raging over silicone vs urethane vs rubber and over shore ratings (A scale) of 30 vs 40.

Obviously you could pit and change tyres if your super softs start to degrade or pick up too much debris, but does that lose you more time than pootling round on harder tyres?

I've got some Shore (A scale) 50 urethane that I will be using to make replacement tyres for my old Scalextric Minis, Escorts and Datsuns (longevity of tyre being the aim) but I am wondering whether I should make a few tyres for my proper racers and try a bit of endurance racing with harder tyres.

Has anybody tried this hard a tyre before? If so; how did it work out?

· Circuit Owner
5,961 Posts
Discussion Starter · #7 ·
QUOTE (300SLR @ 25 Sep 2011, 08:13) <{POST_SNAPBACK}>First question is what everybody else in the race is using. There are comparability issues with some sorts of tyre, you don't want to be scatting around with no grip because your tyres don't work in the track conditions produced by the other teams' tyres.

Assuming you can change wheels/ tyres, there's a compromise between with how much you gain by a tyre change and how much time is lost changing.

Generally softer tyres should give more grip, but wear out more quickly. How much difference that makes to lap time depends on the car, track conditions and maybe driving style.
Another variable is how sensitive the car is to ground clearance. With some cars tyres around the optimum size are important. With others there is little or no penalty in starting with more ground clearance. Starting with extra ground clearance means the car will run longer before the tyres are worn out. If the car is quicker with smaller tyres it can be worth starting smaller and changing more often.

How long does a tyre change take? Depends how you do it.
First tip - if you are planning to change tyres practice before the race and make sure the spares actually fit. There's a lot of laps to be gained by making learning how to do it quickly before the race.
With sidewinders and low angle anglewinders, it's quicker to change the complete axle / gear / wheel assembly. Simply undo the grub screw on the non-gear side, slide out the axle complete with gear and gear side wheel / tyre. Then slide in the replacement axle with the gear and gear side wheel / tyre already fitted - fit the new wheel/ tyre on the other side. The experts do that sort of tyre change in under 10 seconds.
With in-lines and larger angle anglewinders it is normal to change both wheels on the existing axle. It's important not to mess up the gear mesh. With anglewinders and in-lines where the motor shaft locates in a groove in the crown gear this shouldn't be a problem. If the crown gear isn't located, its worth adding spacers between the bearings so that gear mesh doesn't depend on accurate wheel position.

I should have asked my question more clearly - or at least stated the circumstances....

We will be running a single make endurance race with identical vehicles and the tyres must be urethanes. So the only variables allowed are how well you prep your vehicle (no special parts allowed) and what type of urethane you use.

This removes the effects caused by somebody running silicones. The track has not been used in competition yet and has only run standard rubber and urethanes and no oiled tyres.

I think getting a definitive answer is out of reach - it seems there are too many variables. I guess I will have to buy some shore 30 urethane and make some tyres form 30 and 50 and run my own pre-endurance race to check out lap times and tyre degredation.

Research - great excuse for more track time!
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