First Gear Grip

[E46-M3-SMG]

In my vanilla M3, the car is near the point of losing grip when in first gear at full throttle, i.e. at 5-10 mph and then (progressively) flooring the throttle. On anything but clean, dry, straight roads, the tires will let go. This is on Michelin PS2s.

While doing some numbers, I stumbled on the fact that a lightened car with the same power/torque would loss grip in a given gear before a standard car. This is due to the car having lower weight on the wheels but applying the same wheel torque. Or it could be envisioned as having the same tires trying to accelerate the car at a faster rate. I therefore assumed that one of the reasons BMW had chosen to change the speced tires to Michelin PSCs was to retain the first gear grip without having to change the diff.

I’m thinking of getting a CSL this year and would be considering changing the diff gears to 3.91.

So can anyone tell me if in practise a CSL will have full grip in first gear on a few different tyres? Specifically Michelin PS2, PSS and PSCs
Also for anyone who has changed to a 3.91 diff, will the car now kept first gear grip on Michelin PSCs, assuming anything less wouldn’t.

Sorry for the long, irrelevant and probably misplaced thread but you can blame shimmy’s “Start a Thread Week” for luring me away from my long standing lurker status.

Thanks

Colin