Competed in the 60 Lap ATC GP yesterday. Did much testing to ensure tyres would last. Did 21 laps before blowout on R3 front and 28 on R4 before losing the back and having to plant the accelerator (XFR) to get it back - this blew my fronts too.

Thing is, I never had a problem with the rear tyres during testing.

I'd planned a stop at lap 20 and one at 40 on R3s. I had good pace and when I pitted the first time I was up to 6th of 23! Came out in 8th. 17 laps into the second stint and the rear right blew sending me into a wall - fortunately right by the pit entry. I dropped to 12th.

This screwed me completely because I would either have to switch to R4 fronts to do the extra 3 laps, or pit again later. I figured I'd lose more time on the R4s so planned to pit on lap 55 (only 18 laps more) and then run a light fuel load and r2s for the last 5 laps. Unfortunately on lap 49 the rear left blew! Only 12 laps into the 3rd stint. Unfortunately it was in T1 so I had to do the whole lap on a rim. By the time I came out of the pits I was 15th. Gutted. Finished 13th in the end.

Wierd - I managed to do 28 laps on these rears with no probs but in the 2nd and 3rd stints they only lasted 17 and 12 laps repectively. I didn't drive any harder so wonder why they last less time in the 2nd two stints.

Any ideas on this would be greatly appreciated.

Does the arse end squirrel around a bit? Lateral motion (In real life) will cause a good deal a wear and tear to the tyres. If the car is moving sideways alot during the race (If you have a four wheel drift setup or an oversteery one) then the rears will generate alot of heat causing them to break down. Softening the rear suspension and increasing the the PSI might be two quick fixes . . . other than that . . . . dunno.

Did you observe something strange in F9-view? Like flat spots or excessive heat?

Vain

Sometimes flat spots on the rear tyres are caused by the inside back tyre not having much downward pressure applied to it when braking and cornering at the same time. The inside rear wheel lifts almost off the ground but the tiny bit that is still touching the the ground locks up and thats how you get your flat spot. Every lap it flat spots on the same place until in blows.

it could be the setup, i have 2 aston nat sets that both give the same times, but one can screw a set of tires in 3 laps, and the other one was going for 20 laps, tires on left were staying at 100 centigrade, and the rights were virtually stone cold, and yes this was on the XFR!

Well in a race there is alot more going on in your head and you may not be driving the same as you were in practise (even if you think you were :tilt i.e. your driving doesn't have too change too dramatically for tyre wear to increase significantly and this is very noticable in FWD cars, I've seen quite a few seasoned drives struggle with tyre wear in longer races in FWD cars . So your not alone In real life this very issue is what sets the top drivers apart from the rest of the pack, it's not just fast lap times that win races but fast effecient laps that do

In my experience I always drive harder and heat the tyres more in a race then when testing, just because there is so much more going on and you are thinking about an awful lot more things that when testing alone.
I tend to find you do a lot more little lockups, more small losses of traction etc. even though you dont really notice it.
If your R3's lasted 21 before a blow out in testing then banking on doing 20 laps stints in race conditions was a pretty risky strategy.

Believe me, I drove hard in the 23 lap test and even overheated the fronts but no problem. In the race I lapped consistently within 1/2 a second each lap. They lasted 20 laps fine in the first stint, when you would expect me to be pushing harder while everyone is close. Second stint only 17 and third only 12. I assure you all I did not push any harder or change my setup. The tyres showed no unusual signs in F9. In addition, a fellow racer had the exact same experience. We tested together and neither of us had probs with rears. We used different setups for the race but suffered the exact same problem.

Only thing that was a bit wierd is during the second stint the car seemed to get very oversteery but after the pit stop handling appeared to return to normal as it was in the first stint. Final stint handling was normal and yet tyres only lasted 12 laps!!

I was thinking maybe rear body damage may have been the cause if some rubbing was happening but I would have thought this would have shown up in F9. I didn't have any significant contact with anything until after the first tyre blow.

The mystery continues. Clearly not many of us run these long races so maybe that's why no-one has experienced this problem. If it were a 20 lapper the problem would not have appeared.

colcob - it wasn't the rears that went after 21 laps - that was the front. I never had a rear blow in testing even after 28 laps! I don't know how much longer they would have lasted. yet stint three they only lasted 12! This is why I'm confused.

The fronts lasted the 20 laps in each stint as I planned. I did several tests and R3 fronts always went in the 21st lap which was why I was happy to take the risk. And I was spot on - R4s are 2 seconds a lap slower and the R3 fronts lasted the 20 laps in every stint. It was the rears that I had a problem with even tho they lasted 28 laps in testing.

So, what exactly were the rear tyres showing? All cool and plenty of rubber left? Or was the rubber getting thin, although in my experience that's pretty hard in a FWD? Maybe the sidewalls were getting too hot (low tyre pressure) and they gave up?

67% fuel at the start of each stint so fuel was exactly the same for all 3 stints so it can't be that

Kev - I know what you are referring to but this effect is far more subtle then the effect I experienced in stint 2. Also, it only seemed to happen on right handers. It was the rear right that blew in the 2nd stint. If the two things were related you would expect the rear left to blow.

Did it definitely change the rear tyres at each pit stop?

If so it does sound quite strange. Would be nice to see a replay if someone has it? Only that will give us the full situation and hopefully an explanation.

Does indeed sound odd, I dont suppose LFS models punctures at all?.

Dan,

That's what I was wondering. Maybe there is some debris moddeling in the game where people can drag crap onto the track that can cause punctures. I had one or two instances where I put a couple of wheels on the grass myself.

I was pretty sure all tyres were changed at the stops but I will check on the replay tonight. Sure I looked during the stop itself. I always have F9 switched on.

Yes I do have the replay but 23 racers over 60 laps of a 1m:50s circuit makes for a damn big mpr file! Not sure where I could post it. It may be available on the ATC team website.

You're pointing me towards something... Is it possible that slight damage (minimal) caused slight changes to the wheel's geometry (toe, etc.)?
I did notice that when driving off the track the FFB sometimes changes permanently until you restart the race during my preparations for the Westhill-60-lapper. This might be due to minimal damage (not visible in F10) and may also have caued your tyre wear. I don't exactly recall wether the weird-FFB-feeling went away after a pitstop or not.
Can you review the tyre-values (camber, toe) in a replay?

Vain

I had a similar problem on lap 39 (planning to stop on L40/42), although i'd set the 'change tyres if wear >' to 70% on the first stop, my rears didn't get changed. I assumed , that they would last at least until the next stop, but near the end of the next stint they blew . after reviewing the replay, (a long, long, long proccess) it seems the first one went under braking, and the second blew after i lost the back end, the tyres were thin on the inside edges and stone cold.

My theory is, as the weight drops off the rear end, as fuel is used. The rear brakes tend to lock up a bit more, and the wear gets exponentioally higher as they thin out and cool down, combine these two factors and you get a slightly unpredicatable wear rate. add in the fact that we were racing, and I'm pretty sure that's the reason.

My solution, More front brake bias and more rear tyre pressure. and maybee keep a better watch out for flatspots early on while they're a little more obvious.

And i'm pretty sure the tyre wear check in the pits takes an average reading rather than the lowest point. Might be one to watch out for in future.

BTW good effort gentlefoot, a tough race for most of us.


URL of replay to follow.....

Hmm, its interesting, I tend to think that the theory of slightly locking the unloaded inside rear under trail braking is the best one.
I wasnt suggesting that you weren't pushing hard in your testing, just that in my experience, I just dont drive as tidily in a race as I do in testing, even if I'm lapping quickly during testing. There might just be an accumulation of micro-errors that you dont notice while racing hard that add up to a flat spotted rear.
It would be worth posting the MPR if you have some webspace big enough for it.

I found the more practice I had the smoother I became and needed less and less lock so I'd be surprised if I drove in such a way as to cause more tyre wear.

I had mine set to change if 60% worn so I will check tonight if the rears were indeed changed.

I've also noticed that toe can be knocked out in a collision but I ususally notice such things.

Afro - great race wasn't it. I was very surprised to see you still behind me after 30 odd laps. You were quick on those R4s man. I switched to R3s front!

I didn't talk about collisions. I talked about driving over a curb, or going over some gravel for 20 meters. That has caused permanent changes in the FFB for me several times.

Vain

Sorry Vain - I didn't read your post carefully enough. FFB changes? What wheel do you use? I've never had this happen to me. I use the Logitech MOMO.

Upload the reply to yousendit or something like that.

Dan,

I also use a Logitech MOMO (Racing).

Vain

Dan - I'll have a look and see how big it is tonight - the replay that is lol.

Vain - you got me worried now

I've had few instances where I have crashed or driven over rough terrain with my car, causing the chassis itself to bend. No damage shown in F10 but I felt something had changed in the car through ffb and it got fixed when I did a pit stop without changing tyres or adding fuel. Quite far fetched, but I assume it can happen.

In theory this works this way: You drive off the track over a curb, you get a very short peak-load that shows in the F10 view as an orange flash, one tyre has a very small change of geometry and when the tyre was one of the front tyres the steering-forces cange due to this minimal change in toe, camber, or whatever.
At least that is what I figured. Might also have been a bug in LFS's FFB-code.

Vain