GR Yaris GR Yaris at racetrack

Rallyboy said:
Hey man, sounds like a fun day!

I hear you about the PS4S tires. I had the same experience where they felt great after 3/4 of the out lap, but before finishing the first hot lap they were... too hot! I also tested the Michelin PS5 and found them similar, but slightly better - 2 laps. Nankang AR1's also overheated but I got maybe 3 or 4 laps before they were cooked. I also ran higher pressures in the PS5's to see if that helped, I think it did. I hear Mercedes guys running the PS4S at 43psi on track. I went out 36psi cold and ended up in low 40's hot. If you are having trouble getting heat in maybe drop the pressure. What were you running?

Interesting you had a fast corner moment on the rear. I had a professional driver do a few sessions in my car and she found the same problem. In the wet the rear was unstable mid-corner on fast turns. It was less pronounced in the dry sessions but definitely loose under brakes. She said it felt like the car had too much rear brake and also that it was quite light, so not much weight to get the nose to dive under brakes and help initiate the rotation.

Next I will get adjustable rear camber arms and see if a little more neg camber helps. My stock rear is -1.5deg on one side and -2deg on the other.
Front is -3deg and toe is -1.6mm F and +1mm R - which worked great, understeer gone!
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Cheers nice to get similar input on the issue. The way it went was bit sudden as in previous session I felt the car was quite tossable in those fast corners, and now it suddently broke into slide. Could be that I had more speed, track was more slippery (damp conditions), or input was different. All in all, should get more seat time to understand why it goes when it goes..

would prefer getting a setup where the rear was really stable and use then stronger inputs to get car turning vs. having to knife edge with the limit -> much easier to iterate those limits with stable car. Those rear camber bits sounds like a good idea.
 
Short video of last session. Easy laps. Place where the code brown was gotten can be seen on 2:50 - not the exact lap but maybe similar symptoms.

 
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Spirited said:
I thought positive toe = toe out. So, reading the relevant bit of your post above as "front toe in & rear toe out" leaves me scratcing my head.

I probably got something wrong. Could you please clarify, for my understanding?

Thanks
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Yes basically the rear was close enough as stock, toe in was spot on (albeit 0.7 on one side and 0.3 the other) and just did camber bolts on the front and set that toe out (stock F was toe in)
 
Michael Knight said:
Here’s another vid where high speed lift (?) results in slide
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I had similar issues into T1 at Phillip Island. I ended up doing it deliberately to help rotate the car - if you're already controlling a slide, you can't "lose it" so to speak... at least not suddenly without warning. A bit sketchy on a 200kph entry, but that's all part of the fun! I'm not sure how to fix this rear grip issue but I did notice my lap times at Broadford dropped away 1/10th each session as the fuel load dropped, then when I filled the tank I was back to PB's. My point is I think more weight in the back might help. Good excuse to get a half-cage. And save money not buying a lithium battery.
 
Michael Knight said:
Here’s another vid where high speed lift (?) results in slide
Click to expand...

Looking at the revs & speedo, I'm struggling to spot a lift-off at the critical point where it all started going wrong.

However, there may be a slight crest on the surface of the track at a point when the steering probably wasn't dead straight. With that speed, that may have made the rear even lighter, thus starting to lose grip.

Lift-off oversteer seems to be very much a thing for the GRY, though; even in Sport mode.
 
Spirited said:
Looking at the revs & speedo, I'm struggling to spot a lift-off at the critical point where it all started going wrong.

However, there may be a slight crest on the surface of the track at a point when the steering probably wasn't dead straight. With that speed, that may have made the rear even lighter, thus starting to lose grip.

Lift-off oversteer seems to be very much a thing for the GRY, though; even in Sport mode.
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Yes if you read the video comments they state that theres a bump that causes issues if car is not as it should. Maybe 1+1 results the issue.
 
That's a classic place for many crashes, mid corner crest at high speed. Braking must be done before crest, over crest some slight throttle and straighten out steering ever so slightly momentarily is the secret sauce.

For flat high speed corners, again try to be on throttle through the bend after slowing on the straight. If slight slowing down is nevertheless required already in the bend, instead of lifting its better to dab the brakes lightly with left foot braking, this keeps the diffs 'locked' (not litterally but wheels speeds remain interlinked better) both slowing down and coming off the brakes (throttle remains in all the time).
 
Michael Knight said:
Yes if you read the video comments they state that theres a bump that causes issues if car is not as it should. Maybe 1+1 results the issue.
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Tthe bump was removed years ago, the bump was a joint between two different asphalt pavements ...I've been told. But it's still a dangerous spot, be sure to give throttle and absolutely do not lift off.
 
DrSetup said:
Been to Alastaro a few times but not with my Yaris. Will try to go there in September with some friends if it goes by plan.🏁
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did you made it there? Would be cool to get a reference lap from fast GR. my season best was 1:31.98 with which I'm happy as with regular tires and suspension. Sub 1:30 should go easily with semis.
 
Michael Knight said:
did you made it there? Would be cool to get a reference lap from fast GR. my season best was 1:31.98 with which I'm happy as with regular tires and suspension. Sub 1:30 should go easily with semis.
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Didn't go there yet. Maybe in October but depends on the weather and how much I habe at work.👍🏻
 
Anyone tried Federal 595RS-R with their GR?
Noticed this is plain cheap tyre so would be good option for budget track.

255/40/17 Seems to be 260mm wide - wonder if they would fit under GR on 9J wheels (ProTracks)

edit. found one review
Seems to be quite bit slower than Nankang AR-1..
 
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ProTrack is providing GR with Nankang Ar-1 in 255/40/17 so that combo should fit at least..
 
Just checked - manual stating car gives warning if oil temp exceeds 140’C

16564428-6A1E-43CB-88CF-EA7E9B3E78B9.webp
 
GottGry said:
Tthe bump was removed years ago, the bump was a joint between two different asphalt pavements ...I've been told. But it's still a dangerous spot, be sure to give throttle and absolutely do not lift off.
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Some people claim that this sector is nowadays even more dangerous than before.
 
vevesse said:
Some people claim that this sector is nowadays even more dangerous than before.
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What makes it more dangerous without the bump? higher speeds, faster cars, over confident drivers, higher expectations of a low laptime
 
GottGry said:
What makes it more dangerous without the bump? higher speeds, faster cars, over confident drivers, higher expectations of a low laptime
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A mixture of the named topics. The observed crashes appear to be more severe than before.
 
Rallyboy said:
I had similar issues into T1 at Phillip Island. I ended up doing it deliberately to help rotate the car - if you're already controlling a slide, you can't "lose it" so to speak... at least not suddenly without warning. A bit sketchy on a 200kph entry, but that's all part of the fun! I'm not sure how to fix this rear grip issue but I did notice my lap times at Broadford dropped away 1/10th each session as the fuel load dropped, then when I filled the tank I was back to PB's. My point is I think more weight in the back might help. Good excuse to get a half-cage. And save money not buying a lithium battery.
Click to expand...

I had the same thing before corner weighting the car and installing the wing, the wing (MT-Carbon) has absolutely made the back end more stable now, on the exact same corner it now has a slight 4 wheel slide as I'm able to lift before turn in and feed power through the corner. It's no faster overall but it's consistent and alot more controlled.
 
Coilover spesific talks in this thread.

GR Yaris - Coilovers

Summary data table available coil overs for GR Yaris into one table. Spring rates, piston sizes, adjustability on setup and height. If you have a set and more detail please update on the thread so I can fill the table. Set BC BR BC ER Bigem Bilstein B16 PSS10 BOS H&R Monotube H&R Clubsport...
www.gr-zoo.com www.gr-zoo.com
 
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