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Circuit Owner
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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?
 

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Gary Skipp
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Hi there Mr Mod

My sum total of 1/32 endurance racing has been done with the Slot.it P4 on Ninco track - but it may answer some questions. What I'm writing is from 12 and 24 hour races (several of).

The tyre will change in 'feel' over the duration. Ultimate grip you get from a fresh pair in the first hour will drop off, but after that it'll stay about the same. It'll just feels different. You'll take over the car from somebody and be like "what the hell is this" for about 20 laps, but after that your laptimes will settle down and you'll be doing what you did before. You just have to adjust.

They physically wear out. From races I've started with a brand new set, you can get 10 + hours out of them before they wear through (inline motor car). I did a 12 hour on one set of tyres, and it had small holes in at the end. But still, one set. We won.

Factors that affect the wear rate will be the abrasiveness of the track, your final drive gear ratio, motor RPM and general hooliganism. If you run a sidewinder car, expect the gear to foul the track before the tyre gives out. 4-6 hours maybe in the same circumstances.

Pitting vs. changing tyres - stay on the track. Put the times in & don't come off. Maybe now with the super-soft tyres this might be different, but given the choice I'd always drive around it so I can put the laps in. As a rule of thumb, the stopwatch never lies. If your times are okay then it isn't worth stopping. It's hardly ever worth stopping. For tyres or anything else.

Finally, you mention debris - it is always worth cleaning your tyres if you're loosing seconds after a crash into the dusty bits. If you are organized it takes literally one second to clean them. It saves many. If you've been lapping on the track without coming off, and your tyres fell like they need cleaning, they don't. This is just in your head.
Clean if you've been off the circuit, that's about it.

Silicon tyres don't wear out. The do need cleaning a lot to perform well. But again, takes a second. Urethane, can't help. Sorry!
 

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Too many variables. Are you taking club racing or just having some fun at home? Its a very rare situation that a club will allow silicones with rubber onto the same track. The two are not compatible. I use shore 40 and 25 urethane tyres. Amazingly the 25 wears at the same rate or better than the 40 on the tracks I race on. They slide about less so they dont wear any faster than the 40s. The softer 25s can be worth up to 0.5s on some tracks. I race on a fairly abrasive surface and I get about 4 hours out of a set of tyres. You can get pit stops down to a fine art. Two rims changed in less than 15 seconds. About two laps lost. Do the maths, assume 0.1 seconds slower over 4 hours using harder compounds is equal to 2400 laps (based on 6 second laps) over 4 hours. At 0.1 seconds thats equal to 240 seconds advantage. If it takes longer than 4 minutes to change your tyres then there is no advantage.

cheers
rick1776
 

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Premium Member
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We ran 6 hours with shore A30 and they just got better with time, they. Been trued before racing.
 

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Ray
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What type of wheels are you running plastic or alloy, are you able to glue tyres on, are you able to do wheels changes during the race!

We run a couple of 6 hour enduros each year at our club and usually require four compulsory pit stop for wheel changes. This is either a change of wheels from side to side or changing to another set of tyres. This emulates real racing and adds team work and tactics into the mix.

We have recently run an NSR Porsche 997 enduro where the each team had one set of air system rims and one set of non air system rims (huge difference in lap times with the air systems being far superior).

We usually run NSR tyres and run on a ferro painted timber track, you do see some tyre gaining and some marbles starting to appear towards the end of the race which mimics real racing.

Hope this help

Ray
 

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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.
 

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Circuit Owner
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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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Nobby Berkshire
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That's a bit like saying how long is a piece of string, but the answer is pretty simple...

...do a 100 lap race with your fave tyres and monitor your laps, any noticeable wear and tear, pick-up of track dust and debris, and tipouts. Then multiply by 10 or 100 or whatever. If you are not happy with performance then get softer ot harder tyres accordingly.
 
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