Need Help on Tyres - PS4S vs PSC2

[IMI-003]

Dear all,

need your extensive knowledge on this. Currently car is a F80 ZCP with:

~ 12mm spacer Front and Rear
~ Eibach Pro Kit (Euro spec)
~ 666M

I want to know the tyre size in PS4S and PSC2 that will fit without any scrubbing issue.

Personal preference is to go with PSC2 but looking at the current setup with PSS, it seems like I don't have much room to play with (especially at the rear) if I stick to the 265/30 and 285/30 set up as the PSS is relatively stretched.


Many thanks in advance.


SC

[guess2098]

Any reason why you want to go for cup2?

[hwalk]

The PS4S is a bit wider than the PSS. If you stick to your current size it'll be fine with both tires.

The PSC-2 is a ultra high performance tire, which means more grip on dry streets but needs to be warmed up and offers less traction in wet conditions. I'd recommend those only if you use the M4 as fun car (track or advanced street use). In addition the PSC-2 is not nearly as durable as the PS4S.

BMW wheels are 9 and 10 with offset 29 front and 40 rear. You're right there's not much options, maybe 295 in the rear but i don't think tread width's noticable better as with 285.

[IMI-003]

Guess2098,

reason for Cup2 cuz I'm considering to do a few track days with it. plus, the PSS doesn't give me too much traction after the tune

ta,

SC

[IMI-003]

Hwalk,

thanks for the reply.

I will definitely prefer the CUP2 cuz I will be talking the car to the track. Coming from a JDM track toy background, I am used to running semi slicks on track, however, with the size of the 666m, I couldn't run the usual semis (A050, Z221) hence CUP2 is the best options as the trofeo R is way too expensive.

Back to the topic, what worries me is, looking at the current rear end with the Eibach installed, it seems like if the CUP2 is any wider in track width (even running the same 285/30/20) then I will be screwed.


By the way, you've mentioned M4 is your response, however, mine is a F80 M3, so will the CUP2 still be alright with my current settings?


many thanks in advance.

[CanAutM3]

I don’t believe there is a suitably sized PSC2 for the front CP 666M wheels. Closest fit would be a 245, which is a little narrow IMO.

[CanAutM3]

Originally Posted by IMI-003

Hwalk,

thanks for the reply.

I will definitely prefer the CUP2 cuz I will be talking the car to the track. Coming from a JDM track toy background, I am used to running semi slicks on track, however, with the size of the 666m, I couldn't run the usual semis (A050, Z221) hence CUP2 is the best options as the trofeo R is way too expensive.

Back to the topic, what worries me is, looking at the current rear end with the Eibach installed, it seems like if the CUP2 is any wider in track width (even running the same 285/30/20) then I will be screwed.


By the way, you've mentioned M4 is your response, however, mine is a F80 M3, so will the CUP2 still be alright with my current settings?


many thanks in advance.

There is a fair bit of room in the rear. I run very wide 305 NT01 in the rear on Eibach springs without coming close to rubbing. You’ll have to get rid of the spacers though.

[CanAutM3]

Originally Posted by hwalk

The PS4S is a bit wider than the PSS.

Sorry to say, but this is mostly not true. In fact, the PS4S in general terms have a slightly narrower tread than the PSS. It is also important to consider what manufacturer specs one is comparing, not all tires are created equal despite having the same "official" dimensions.

For instance, in the 285/30R20 size, the widest PSS has a 10" wide tread (the BMW M3/4 specific one is 9.9" wide) while the widest PS4S is 9.9" wide (same as the BMW spec PSS). The 295/30R19(*) PSS has 11.6" tread width while the widest 295/30R19 PS4S has a 11.1" tread width.

[whoop_ass]

Originally Posted by CanAutM3

I don’t believe there is a suitably sized PSC2 for the front CP 666M wheels. Closest fit would be a 245, which is a little narrow IMO.

Negative
cup 2 N0 245/25 runs wider or the same as 265/35 p4s if memory serves me correct
There is a thread on here with discussion to the cup2 on 20"

[CanAutM3]

Originally Posted by whoop_ass

Negative
cup 2 N0 245/25 runs wider or the same as 265/35 p4s if memory serves me correct
There is a thread on here with discussion to the cup2 on 20"

Indeed, the GT3 and GT4 front PSC2 have a 9.6" tread width. My point was more to the fact that these tires have a narrow 9.8" section width, 0.8" narrower than the stock 265. Further, those specific 245/35R20 PSC2 are designed to work on nose light Porsches, not nose heavy BMWs .

[Mandi90TT]

Is the car your daily driver (in addition to the track days)? If yes, then PS4S on the stock wheels, and get a dedicated set of track wheels and track tires (NT-01s work great for me).

If not a daily, then go with the PSC2.

For reference, I have 295/30/20's on the rear of my M4, 265/30/20's in the front. Both PS4S. Not 666 wheels, aftermarket wheels, but 295 fits just fine.

Track tires are 305/35/18 NT01's in the rear, 275/40/18s in the front. Use 10mm spacers in front to prevent rubbing.

[IMI-003]

Originally Posted by CanAutM3

There is a fair bit of room in the rear. I run very wide 305 NT01 in the rear on Eibach springs without coming close to rubbing. You’ll have to get rid of the spacers though.

Notice yours is a M4, would the M3 has less room? also, assuming the track width and the dimension of the tyre of the 305 NT01 is in the same proportion as the 285 PSC2, then with the 20mm difference between the tyres, I shouldn't need to drop by spacers? Obviously if the track width is not in the same proportion between the 2 tyres then my assumption is wrong.

[whoop_ass]

Originally Posted by CanAutM3

Indeed, the GT3 and GT4 front PSC2 have a 9.6" tread width. My point was more to the fact that these tires have a narrow 9.8" section width, 0.8" narrower than the stock 265. Further, those specific 245/35R20 PSC2 are designed to work on nose light Porsches, not nose heavy BMWs .

you have a valid point but using that size PSC2 proved to work well
had a bit of outer wear which is normal due to only running 1.5 deg camber on stock suspension with no camber plates.

I think with more camber they will work even better.

[CanAutM3]

Originally Posted by whoop_ass

you have a valid point but using that size PSC2 proved to work well
had a bit of outer wear which is normal due to only running 1.5 deg camber on stock suspension with no camber plates.

I think with more camber they will work even better.

Good to know it works out well

[CanAutM3]

Originally Posted by IMI-003

Notice yours is a M4, would the M3 has less room? also, assuming the track width and the dimension of the tyre of the 305 NT01 is in the same proportion as the 285 PSC2, then with the 20mm difference between the tyres, I shouldn't need to drop by spacers? Obviously if the track width is not in the same proportion between the 2 tyres then my assumption is wrong.

The M3 actually has a little more room in the rear.

I am not sure I fully follow you, since track width is measured at the tire centreline where it contacts the road, track width is unaltered by tire width. I run my 305 on 18x11ET40 wheels. So the 285 with 12mm spacers on stock wheels result in 32mm wider track than the 305 on my wheels.

I assume you are inquiring if a 305 fits, then a 285 with 12mm should also fit? The 285 is nominally 10mm farther from the fender, so with a 12mm spacer, it is 6mm closer to the fender than the 305 on my wheel.

Further, I am not a big proponent of significantly altering offsets (which spacers do) since it alters suspension tuning, particularly up front where it also affects the scrub radius and Ackerman angle.