Traction issues on e85, 45psi boost

[AJRMKV]

At your power level, spinning 4th isn’t really surprising. A 7275 at 45 psi on stock springs is asking a lot from the chassis, especially on the street. At this point it’s less about “not enough tire” and more about the rear suspension unloading when the torque comes in.


As far as ET Street SS vs ET Street R — yes, the R will help. The carcass is stiffer and it handles higher-gear torque better. You’ll likely see better consistency and a little more stability in 4th, but it’s not going to be a night-and-day fix by itself. It’s an improvement, not a cure.


The bigger issue is suspension. Stock springs at stock height just aren’t meant to manage this kind of power. The rear squats inconsistently and then unloads, which is why it’ll spin even with rolling anti-lag. A drag-oriented rear spring or coilover setup will do more for traction than swapping tires alone.


Boost control matters a lot here too. At 45 psi, feeding torque in gradually (boost by gear, ramping instead of slamming peak boost) usually works better than trying to rely on the tire to save it. Most fast Supras aren’t hitting full boost instantly in 3rd/4th.


On tire pressure, 20 psi warm on SS isn’t crazy, but it’s worth experimenting slightly lower (18–19 psi) and logging wheel speed vs boost instead of just setting it once.


Bottom line:
ET Street R = worthwhile upgrade
Suspension + boost management = where the real gains are


Your 4.8 60–130 looks traction-limited, not power-limited. Once the chassis is sorted, the car should pick up noticeably.


Hope that helps someone else chasing grip at this power level.

Thank you kind sir — This was very insightful — What suspension/tire setup would you recommend — which coilover setup is least likely to result in a Supra-tree Integration?

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