Will 265/35/20 with 305/30/20 produce more understeer?

Brians · 05-07-2017, 02:34 PM

I'm looking for more traction and trying to get the biggest stickiest footprint I can on the back. Thinking of Michelin Pilot Sport Cup 2s.

I believe the PS Cup 2s with the 305 rear size will fit and solve my hook-up (wheel spin) issues.

I'm worried about changing the ratio from 265/295 (front/rear) to 265/305 that the rear will grip better on a turn, thus producing more understeer.

Has anyone had experience with this?

carrera2RSL · 05-08-2017, 05:45 AM

The short answer is yes, but it will be as you near the limits of grip. Increasing the track at the front (spacers) would reduce this marginal effect

somer · 05-08-2017, 11:08 AM

265/35/20 SC2s (from GT3RS) are 0.3" wider than star spec PSS and similarly 305/30/20 (from GT3) are 0.5" wider than star spec 295/30 PSS. It's pretty unlikely you'll notice anymore understeer with a wider tire thats 0.2" wider on the rear.

The Ferrari 305/30/20 SC2 has basically the same tread width as the star spec PSS if that's a real issue for you.

Northern X5M · 05-08-2017, 11:51 AM

I have tracked my car many times and to produce uncomfortable levels of understeer you have to push the car pretty hard. Harder than I would care to on public roads. So I don't think the OP has anything to worry about. I have about 1000km on 275 4S/305 SC2 set up and I am friggin' loving it.

apexlocator · 05-08-2017, 12:10 PM

Quote:

Originally Posted by Northern X5M

I have tracked my car many times and to produce uncomfortable levels of understeer you have to push the car pretty hard. Harder than I would care to on public roads. So I don't think the OP has anything to worry about. I have about 1000km on 275 4S/305 SC2 set up and I am friggin' loving it.

How long do you think the SC2 take to warm up? I am STILL undecided on rear tire setup on OEM 343m, but I'm more interested in straight line performance.

Brians · 05-08-2017, 03:36 PM

Great feedback. I feel better about that size setup. Thanks all.

Another couple questions (particularly for you Northern X5M as you seem to have a similar setup to mine) -

1. how many miles can you expect to get out of a set of PSC2s? I don't track my car, so it would be strictly street driving.

2. assuming you are able to hook up and not spin the rear everytime you put your foot into it. Correct?

3. Thinking the new PS4's may also be a solution. What are your thoughts?

Northern X5M · 05-08-2017, 04:48 PM

Quote:

Originally Posted by Brians

Great feedback. I feel better about that size setup. Thanks all.

Another couple questions (particularly for you Northern X5M as you seem to have a similar setup to mine) -

1. how many miles can you expect to get out of a set of PSC2s? I don't track my car, so it would be strictly street driving.

2. assuming you are able to hook up and not spin the rear everytime you put your foot into it. Correct?

3. Thinking the new PS4's may also be a solution. What are your thoughts?

I am not sure about mileage. Depends on you your level of aggression. I am hoping for about 8-10K. I have noticed that the SC2 have chucked some rubber onto my inner fender so they are soft. I have not tested the SC2's from a dig but from a 40-60 hit the car kicks down HARD, squats a goes! I'm pushing 630-650 whp. I think the 4S are still not going to hold from a dig.

Northern X5M · 05-08-2017, 04:52 PM

Quote:

Originally Posted by apexlocator

How long do you think the SC2 take to warm up? I am STILL undecided on rear tire setup on OEM 343m, but I'm more interested in straight line performance.

I've been allowing about 10 minutes of normal driving before I get into it. My car does not have temp or pressure sensors. All I have are the idiot colors.

Brians · 05-08-2017, 06:07 PM

Quote:

Originally Posted by Northern X5M

I am not sure about mileage. Depends on you your level of aggression. I am hoping for about 8-10K. I have noticed that the SC2 have chucked some rubber onto my inner fender so they are soft. I have not tested the SC2's from a dig but from a 40-60 hit the car kicks down HARD, squats a goes! I'm pushing 630-650 whp. I think the 4S are still not going to hold from a dig.

I mostly drive melow, so if I can get 8-10k out of them, and hookup when I stomp on it, I'd be totally happy! Thanks for the feedback.

05-07-2017, 02:34 PM	#1
Brians Private First Class 14 Rep 151 Posts Drives: 2019 M5 Comp Frz Drk Grey Join Date: Dec 2010 Location: Las Vegas iTrader: (2)	Will 265/35/20 with 305/30/20 produce more understeer? I'm looking for more traction and trying to get the biggest stickiest footprint I can on the back. Thinking of Michelin Pilot Sport Cup 2s. I believe the PS Cup 2s with the 305 rear size will fit and solve my hook-up (wheel spin) issues. I'm worried about changing the ratio from 265/295 (front/rear) to 265/305 that the rear will grip better on a turn, thus producing more understeer. Has anyone had experience with this?
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05-08-2017, 05:45 AM	#2
carrera2RSL Lieutenant 183 Rep 579 Posts Drives: F10 M5 CP Join Date: Dec 2016 Location: UK iTrader: (0)	The short answer is yes, but it will be as you near the limits of grip. Increasing the track at the front (spacers) would reduce this marginal effect
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05-08-2017, 11:08 AM	#3
somer Major 960 Rep 1,051 Posts Drives: F10 M5 CP Join Date: Oct 2013 Location: FL iTrader: (0)	265/35/20 SC2s (from GT3RS) are 0.3" wider than star spec PSS and similarly 305/30/20 (from GT3) are 0.5" wider than star spec 295/30 PSS. It's pretty unlikely you'll notice anymore understeer with a wider tire thats 0.2" wider on the rear. The Ferrari 305/30/20 SC2 has basically the same tread width as the star spec PSS if that's a real issue for you.
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05-08-2017, 11:51 AM	#4
Northern X5M Captain 105 Rep 806 Posts Drives: 2014 Tanzanite Blue M5 Join Date: Oct 2010 Location: Edmonton, Alberta, Canada iTrader: (0)	I have tracked my car many times and to produce uncomfortable levels of understeer you have to push the car pretty hard. Harder than I would care to on public roads. So I don't think the OP has anything to worry about. I have about 1000km on 275 4S/305 SC2 set up and I am friggin' loving it. __________________ 2014 ///M5 CP Tanzanite Blue/Cohiba - 11.15 @ 128.8 & 1.84 60' (2150' DA) - BPM Tune - MSR Intake - SSP DCT - SS DPs & HFC Mid Pipes/X-Over - E Race Muffs - 19" MT DRs... On to a new home.
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05-08-2017, 03:36 PM	#6
Brians Private First Class 14 Rep 151 Posts Drives: 2019 M5 Comp Frz Drk Grey Join Date: Dec 2010 Location: Las Vegas iTrader: (2)	Great feedback. I feel better about that size setup. Thanks all. Another couple questions (particularly for you Northern X5M as you seem to have a similar setup to mine) - 1. how many miles can you expect to get out of a set of PSC2s? I don't track my car, so it would be strictly street driving. 2. assuming you are able to hook up and not spin the rear everytime you put your foot into it. Correct? 3. Thinking the new PS4's may also be a solution. What are your thoughts?
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