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Spring rate too high?

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AndyK5

AndyK5

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Sounds like you’re too low. Lots of people have posted stock height measurements. Ground to fender I measured 27.75 with oem wheels and tires (32psi) in the rear.
Just measured mine. On stock wheels stock size tires at 25 psi (did not air up after the track day) 26.25 inch on the front 26.75 inch on the back. Puts me at exactly 1 inch drop all around. I think I'll adjust ride height back up once I put the 18 inch wheels/tires on.
 

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Just measured mine. On stock wheels stock size tires at 25 psi (did not air up after the track day) 26.25 inch on the front 26.75 inch on the back. Puts me at exactly 1 inch drop all around. I think I'll adjust ride height back up once I put the 18 inch wheels/tires on.
it will make a huge difference. Raise the rear at least .75” and front 0.5”. You can leave the front a bit lower, particularly if you have LCA with spacers to correct the roll center… but not the rear.
 
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AndyK5

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it will make a huge difference. Raise the rear at least .75” and front 0.5”. You can leave the front a bit lower, particularly if you have LCA with spacers to correct the roll center… but not the rear.
No LCA, just front endlinks and rear toe arm. I have 2 options. Set it to stock with stock wheels and tires and then put the 18's and 275 ECF's on which would lower ride height by .5.

Or put on the 18's + tires and then set ride height to stock -.5inch. In my mind the suspension geometry ends up being the same as stock and the car rides .5 lower due to smaller wheels.
 

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If you measure center to fender it doesn't matter the tire size. Also, the suspension geo doesn't change with tire diameter differences. Geo only changes when you actually lower/raise the car with the suspension components.

I'm currently at 13.75" front and 14.0" rear. OEM is 14.5" center to to fender all around.

I run about .50* total rear toe-in (about 2.2mm each side). I trail brake like a crazy person. Learned from many years of tracking AWD cars and getting them to actually turn. My Supra is very stable and predictable under trail braking. I do have aero though.

Measured mine when it was stock:

Screenshot 2023-08-17 at 1.48.49 PM.png
 
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If you measure center to fender it doesn't matter the tire size. Also, the suspension geo doesn't change with tire diameter differences. Geo only changes when you actually lower/raise the car with the suspension components.

I'm currently at 13.75" front and 14.0" rear. OEM is 14.5" center to to fender all around.

I run about .55 total rear toe-in. I trail brake like a crazy person. Learned from many years of tracking AWD cars and getting them to actually turn. My Supra is very stable and predictable under trail braking. I do have aero though.

Measured mine when it was stock:

Screenshot 2023-08-17 at 1.48.49 PM.webp
So speeds where I am getting trailbrake oversteer are 40-65mph. Would you say aero helps at those speeds?

edit: Here is my alignment

IMG_3753.jpeg
 

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So speeds where I am getting trailbrake oversteer are 40-65mph. Would you say aero helps at those speeds?
What about at higher speeds? Might want to bring down rebound in the rear and up the compression in the front.

Do you also get oversteer when turning in not under braking?

What tire pressures front/rear?
 
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AndyK5

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What about at higher speeds? Might want to bring down rebound in the rear and up the compression in the front.

Do you also get oversteer when turning in not under braking?

What tire pressures front/rear?

Alignment added to above post.

Higher speeds seems pretty stable, at least more stable than charging in at the turn in very hard and aggressively trail braking to rotate. I mean aggresive trail brake inducing oversteer is nothing new.. Suspension adjustments you recommended make sense to dial out oversteer. Just want to make sure I have the basics right before trying to correct them.


Under the limit (80-90%) there is no oversteer or understeer. Above that 95-110% limit there is still understeer which is what I try to beat with trail braking.


Tire pressures are 26 cold 32 hot front rear.
 

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Alignment added to above post.

Higher speeds seems pretty stable, at least more stable than charging in at the turn in very hard and aggressively trail braking to rotate. I mean aggresive trail brake inducing oversteer is nothing new.. Suspension adjustments you recommended make sense to dial out oversteer. Just want to make sure I have the basics right before trying to correct them.


Under the limit (80-90%) there is no oversteer or understeer. Above that 95-110% limit there is still understeer which is what I try to beat with trail braking.


Tire pressures are 26 cold 32 hot front rear.
Yea I would try dialing it out with what you have currently. Try the Comp/Rebound changes I suggested. I would just do it by 2 clicks at first to see how it feels.

I also run lower tire pressure in the rear by about 1-2psi
 

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Interesting thread. I brake as hard as anyone and trail brake aggressively. 2 board at VIR backstretch which is 160 down to 55 by apex of next turn. No
Wiggle, rock solid

I am on stock suspension w lowering springs. Very little to no wheel gap which I know the conventional wisdom is wrong.
 

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Interesting thread. I brake as hard as anyone and trail brake aggressively. 2 board at VIR backstretch which is 160 down to 55 by apex of next turn. No
Wiggle, rock solid

I am on stock suspension w lowering springs. Very little to no wheel gap which I know the conventional wisdom is wrong.
Whats your PB at VIR? Curious how far up the leaderboard stock suspension and power gets you:
https://lapmeta.com/en/track/variation/130
 

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garudathree

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Sounds doable, A90 platforms with aero, power mods and 200tw should be in the GT4 clubsport area, in the 1:55's
 

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Sounds doable, A90 platforms with aero, power mods and 200tw should be in the GT4 clubsport area, in the 1:55's
Low 2:xx is harder than you think
Need big slicks, power to get to 1:55. One of the best drivers I know has a Supra w 315 slicks, 800 turbo and all the aero, JRZ pro etc. he just went a 1:54 this fall. 1:48-1:50 is IMSA Times
1:55 is around 911 cup times. All w really good driver
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