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

[outnumbered]

I find the CSL more prone to traction issues than my old E46M3... But unless you are drag racing a lot, why does grip in 1st gear matter ?

[Mark CSL]

:whistle: The csl is lighter so yes it should spin but it also has less mass to move ( or i could just be talking pisssshh ):hahaha::hahaha:

Welcome :beer:

[Yanto_csl]

:whistle: The csl is lighter so yes it should spin but it also has less mass to move ( or i could just be talking pisssshh ):hahaha::hahaha:

Welcome :beer:

Depends on the driver mass though, eh Shim ?? :whistle:

[E46-M3-SMG]

I find the CSL more prone to traction issues than my old E46M3... But unless you are drag racing a lot, why does grip in 1st gear matter ?

In my head, unless you can at least sometimes use first at WOT, then it becomes a crawler gear and nothing more. Plus a CSL should take over 1G at peak torque in first gear, so I wouldn't want to give that up.

:whistle: The csl is lighter so yes it should spin but it also has less mass to move ( or i could just be talking pisssshh ):hahaha::hahaha:

Welcome :beer:

Thanks

That was may thinking as well but the numbers say different, cos the force your applying at the wheels doesn't change no matter how little mass your carrying.

[shimmy]

what size rear ps2 are you using?

[shane@mbtech]

Floor a csl from the lights with most tyres and they will light up.

Nature of the beast unfortunately.

They were not designed to get up to speed silly quick, but rather to stay going fast once at speed.

[E46-M3-SMG]

what size rear ps2 are you using?

Just the standard 255/35R19 and would be using standard sizes on the CSL.

Floor a csl from the lights with most tyres and they will light up.

Nature of the beast unfortunately.

They were not designed to get up to speed silly quick, but rather to stay going fast once at speed.

Na I wouldn't be worrying about off the line traction as thats just something you have to deal with.

But I wouldn't want to compromise in gear acceleration of first, by changing to a 3.91 diff, to gain some in second gear onwards.

Otherwise the 3.91 diff seems bang on the money.

[The Gorilla]

Hi,

I run a 3.91 rear Diff.

BMW 6 Speed boxes run low 1st gear 4.22 with
a std 3.64 CW/p..

So moving to the 3.91 CW/p there will be even greater traction
issues in 1st Gear for your driving style.

By fitting the 3.91 CW/p or even higher CW/p, its not
so much about acceleration but rev matching each
gear to the engine power band, and the rev drops
bewteen gears.

I would be looking more at your driving technique
than the tyres or the diff.

Regards,

The Gorilla.

[shimmy]

Hi,

I run a 3.91 rear Diff.

BMW 6 Speed boxes run low 1st gear 4.22 with
a std 3.64 CW/p..

So moving to the 3.91 CW/p there will be even greater traction
issues in 1st Gear for your driving style.

By fitting the 3.91 CW/p or even higher CW/p, its not
so much about acceleration but rev matching each
gear to the engine power band, and the rev drops
bewteen gears.

I would be looking more at your driving technique
than the tyres or the diff.

Regards,

The Gorilla.

I agree, stop wearing lead boots

I noticed ith thhe 4.10 diff the increased tendency to wheel spin so I stopped racing Corsas off the lights

[outnumbered]

I agree, stop wearing lead boots

I noticed ith thhe 4.10 diff the increased tendency to wheel spin so I stopped racing Corsas off the lights

That's odd, I thought you never had a 4.10 diff shim ?

[shimmy]

That's odd, I thought you never had a 4.10 diff shim ?

i did then i didnt apparently then i did again, (all obviously in my other car!) then i didnt!

[Trawler]

1st gear, there is hardly any traction in 2nd & even 3rd gear when giving it some in this weather.

[toplad]

1st gear, there is hardly any traction in 2nd & even 3rd gear when giving it some in this weather.

True, did a track day at silverstone on the 17th Dec, sleet and ice on some parts of the track, the wheels were spinning at 90 :smt044