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      01-25-2021, 03:18 PM   #89
4play
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Quote:
Originally Posted by Lienrocs View Post
You could try running a little more pressure in the rear as well. They're big and heavy cars.

Completely different tire/suspension so I'm not sure how relevant it is but I was running around 32 pounds on A052's and the car didn't have the grip that it did with 38 pounds at all four corners.
I tried a range from 32-36psi on the rears without much success.

Fronts seemed pretty happy anywhere from 35-41psi.

It was tough to change pressures on the fly because we only had 30 min sessions and the track went from 41F/wet to 63F/dry across a few sessions. You couldn't stop in the hot pits, so any pressure changes in real time would have cost 1/2 the session.

And, as usual with a track day, two of the five 30 minute sessions were red flagged due to cars breaking.
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      01-25-2021, 03:30 PM   #90
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Quote:
Originally Posted by 4play View Post

Fronts are 275/35/19 AMG GT R Sport Cup 2s, was running ~35 psi hot.

Rears are 305/30/20 458 Speciale Sport Cup 2s, was running ~32 psi hot.
Just a thought...If the tires you are using are truly specc'd for two different cars, even though both are Cup 2's, one might might be a softer compound than the other. If your fronts are a bit softer than the rears, that will upset balance on corner entry.

There seems to be general consensus that the Star spec Cup 2's that are OEM for the GTS are a bit harder than off the shelf Cup 2's. It's not too out there to believe that the tire manufacturer tweaks the compounds for other model-specific tires.
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      01-25-2021, 03:51 PM   #91
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Quote:
Originally Posted by 4play View Post
I tried a range from 32-36psi on the rears without much success.

Fronts seemed pretty happy anywhere from 35-41psi.

It was tough to change pressures on the fly because we only had 30 min sessions and the track went from 41F/wet to 63F/dry across a few sessions. You couldn't stop in the hot pits, so any pressure changes in real time would have cost 1/2 the session.

And, as usual with a track day, two of the five 30 minute sessions were red flagged due to cars breaking.
Quote:
Originally Posted by Secret Chimp View Post
Just a thought...If the tires you are using are truly specc'd for two different cars, even though both are Cup 2's, one might might be a softer compound than the other. If your fronts are a bit softer than the rears, that will upset balance on corner entry.

There seems to be general consensus that the Star spec Cup 2's that are OEM for the GTS are a bit harder than off the shelf Cup 2's. It's not too out there to believe that the tire manufacturer tweaks the compounds for other model-specific tires.
It's true on the tires and Cup 2 vary substantially. Speciale spec should be ok, but keep in mind it was tuned to that car -- weight, dampers, etc. Accordingly, you might need to go outside of BMW recommended track damper specs to get the most out of that tire and it will never be a perfect fit.

I run Supercar 3R, but in "generic" sizing, so not tuned to the 1LE like Cup 2 K spec is to Speciale.

Suggest ride height is probably the main answer. then damper adjustments from there.

Mentioned my old E9X Fall Line track alignment. It wasn't livable on the street so we upped it probably similar to the difference between GTS street vs. track settings. It wasn't nearly as planted.

Apparently small differences can fundamentally transform handling on track.
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