PDA

View Full Version : A problem maybe someone can give advice



Atak Kat
24-12-2017, 18:21
Today I was in a GT3race, Monza, Ferrari (yes, I know.....)
Anyway, no fuel consumption, no tire depletion.
I setup with 1L of fuel, hard tires, and I was making good times.
No issues at all, car was driving fine.

But then, after about 4 or 5 laps, the rear end started to get really loose on me. I was losing it in corners where in the earlier laps I had no issue.
Tire temps were fine (about 85, hards)
Brake temps also seemed fine.
TC was on, also checked it again after it started to happen

I could not understand what was happening that would cause my rears to lose grip half way through. Managed OK through to the end, but it was really annoying me.

Any idea what could have been causing that?

hkraft300
24-12-2017, 23:24
I’m getting this sometimes where the “grip threshold “ (lack of better term) becomes small. Feels like the rear tire surface is overheating and has very little tolerance for my lack of talent.

Although it feels like overheating and over inflated rear tires there’s no indication in telemetry, because it doesn’t show surface temperature.

I fixed it by down shifting early, driving +1 gear through corners and basically slowing my pace by 0.5 seconds just being smooth and putting less stress on the rear tires.

Atak Kat
25-12-2017, 04:43
I’m getting this sometimes where the “grip threshold “ (lack of better term) becomes small. Feels like the rear tire surface is overheating and has very little tolerance for my lack of talent.

Although it feels like overheating and over inflated rear tires there’s no indication in telemetry, because it doesn’t show surface temperature.

I fixed it by down shifting early, driving +1 gear through corners and basically slowing my pace by 0.5 seconds just being smooth and putting less stress on the rear tires.

Thanks. That's exactly how I had to deal with it. I thought it was really strange that it felt like a one-time change. It wasn't really something that gradually degraded over time. 4 or 5 laps were good and consistent, then all-of-a-sudden we have an issue and have to change driving style (OK fine.).... but it just changed, and that was it. Didn't get any worse or anything. Did another similar race later, and found the same thing happened (slightly different weather, etc, but same behaviour was seen)

But I find it kinda annoying that there is nothing (in HUD) to give any idea what is happening here. Tire wear is off. Fuel is off (no weight change). Weather is constant. So we rule out anything there. Brakes and tire temps and pressures look OK, but more importantly they are not really changing to anything significantly different than before. If Livetrack is correct, then we should be gaining grip (rubber) through the line/corners, not losing it as the race goes on?

hkraft300
25-12-2017, 09:36
It's annoying that there is no indication except feel for the surface layer rubber condition.

It's not tire wear, it's not LiveTrack, and the pressure/temperature is read from core layers of the tire which don't show rapid changes.

My hypothesis, given that we've both experienced this with tire wear off is that we were just pushing too hard for the tires to cope. If I manage the pace for a lap or 3 I can get pushing later.

Atak Kat
28-01-2018, 10:24
It's annoying that there is no indication except feel for the surface layer rubber condition.

It's not tire wear, it's not LiveTrack, and the pressure/temperature is read from core layers of the tire which don't show rapid changes.

My hypothesis, given that we've both experienced this with tire wear off is that we were just pushing too hard for the tires to cope. If I manage the pace for a lap or 3 I can get pushing later.

As time has gone on, I am convinced this was exactly the issue. I think it was mainly me that was pushing, likely braking way too hard in the corners, locking up more than I realized. This causing tire surfaces to cook, and therefore my issues. As time has going on, I'm getting better with the braking to avoid the lock-up and tire screeching, you really need to just listen for that and make minor adjustments to your braking accordingly. It's amazing really how fast you can get the cars stopped if you can find that right balance point.

But as said in other posts, I cannot understand then what the tire temps in the HUD are actually telling me. If it's core temps, then how can there be an inner/mid/outer reading?? Maybe I'm missing something. Or maybe there should be some colour indication on the three temp indicators? If they had a red/green background colour behind the numbers themselves, that might help people understand if those temps are an issue, or not.

In general I think this issue of the tire surface temps is something that can happen to a lot of people. Especially as you build your driving skills. Resulting in confusing car behaviour that is not really obvious why it is happening (even if it is likely correct). But since I've got control of my braking, I'm not having the same issues with sudden loss of traction after several laps (like I was before). My tire temp readings are often in the 90s, so even higher than I was running before, and as long as I don't lock-up, I can manage.

I'm convinced that I was cooking the tire surfaces far too quickly with my aggressive braking, and just not realizing it. Hoping that there is some way to show that in the HUD info in a future patch?

Matt York
28-01-2018, 11:38
To me, it sounds like tyre pressures. It does take them 5 to 6 laps to stabalize, and usually the laps leading up to that feel good, and then the tyres feel like they drop off in grip a tad once they're up to pressure (depending on what the pressure is). It makes sense as the lower pressures in the first few laps will give you more contact patch through the corners. Depending on what your cold pressures are in the setup, you could be getting hot pressures that are a little high, or differences between the 4 corners which could cause some balancing issues. The defaults are generally good, but depending on the track and the conditions, you could see your tyre pressures somewhere between 1.75 bar and 1.85 bar.

Ideally, if the race length is long enough or you are able to practice for the conditions you'll be racing in, you'll want to aim for the same hot tyre pressures on all 4 corners, and have a setup that is built around running at those hot pressures. If you're just doing short online sprint races that are 3-8 laps, I probably wouldn't bother fiddling with pressures away from the defaults.

hkraft300
28-01-2018, 12:23
It's happened to me 10+ laps into a race. For example someone pits in front of me and I get a clear track to push.

Again, there's no indication of it in telemetry that it's a tire temp or pressure issue, and the tire temps don't rise until 3 spins later.

Again, just a hypothesis. Maybe you're right, Mr York, that it's a pressure spike that doesn't quite register or it settles before we return to telemetry? Who knows.

Personally I like it. Punishment for abusing the tires.

Atak Kat
28-01-2018, 12:53
In my case I'm pretty sure it wasn't pressure related. I check it often and I'm able to keep it around 1.8. When the spins and grip issues were happening, I would check immediately the HUD and the pressures were fine, tire temps seemed OK as well (lets estimate low 90s). Everything green. Brake temps also green somewhere 300-350.

It really seems to be that I was roasting the outer tire tread. Maybe even flat spotting?? But it was not reflecting in any of the tire temp data in the HUD.
Now, when being more careful to avoid too much tire screech on braking, it rarely happens that I have the grip completely gone like before. And in many cases now, my tire temps are similar or even hotter (95+), and also pressures same or even slightly more. I don't think I've just become a better driver to catch it, because the issue that was happening before was like night and day for the grip loss (almost like the tires went instantly cold)

w0rthy
28-01-2018, 20:53
It's happened to me 10+ laps into a race. For example someone pits in front of me and I get a clear track to push.

Again, there's no indication of it in telemetry that it's a tire temp or pressure issue, and the tire temps don't rise until 3 spins later.

Again, just a hypothesis. Maybe you're right, Mr York, that it's a pressure spike that doesn't quite register or it settles before we return to telemetry? Who knows.

Personally I like it. Punishment for abusing the tires.

If the tire pressures and temps are are still within operational ranges, then the tires are not being abused.

hkraft300
28-01-2018, 22:58
If the tire pressures and temps are are still within operational ranges, then the tires are not being abused.

Telemetry (and udp) only shows tire core temperature.

You could well slide about (abuse) and overheat the tire surface layer without it registering in telemetry. It takes time for the heat to transfer to the core layer to show a rise in temperature in telemetry.

RomKnight
29-01-2018, 14:40
Also, the drop in grip that keeps more or stable until thread wears out - assuming proper driving/no abuse - is due to the tyres having their peak performance in the first 2/3 laps as IRL, which is why for qualifying teams run new sets of tyres and you see the best laps in the 1st / 2nd flying laps (all going well :))

Zaskarspants
29-01-2018, 14:49
One good skiddy off screws my tires for at least a lap. I sense a temporary ' mushiness ' and decrease in tyre ffb feedback. It seems likely that thrashing the tyre will screw up the contact layer on the surface and temporarily reduce grip.

I recall doing burnouts on my zzr1100 some years ago and having to be very careful with the tyre for a bit afterwards.

RomKnight
01-02-2018, 09:21
chemestry 101 - what happens when you superheat rubber? (tm)

:D