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      04-22-2013, 01:37 PM   #1
CanAutM3
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Question Michelin PSS - 255/265 Front/Rear Combo

I've had my PSS in 255/275 sizes mounted on 220M wheels for two seasons now and I am very happy with the tires . The reason I went for these sizes is that the 265 was not available at the time.

Believe it or not, my fronts need replacing but my rears are good for a little longer. I have run a few track days with the tires, this explain the increased front wear compared to the rears.

Now it is time for me to get new tires. I am questioning going back to 255/275 instead of the stock sizes of 245/265. There are a few opinions in various threads, but not many are backed with data. Here's an extract of the relevent data I was able to collect from the Michelin and Tire Rack sites:

(Plus 255/275 size compared to OEM 245/265 size)

Section width: Front +0.47in (+4%); Rear +0.28in (+2.5%)
Thread width: Front: +0.3in (+3%); Rear +0.2in (+2%)
Weight: Front: +1.3lb (6%); Rear +2.9lb (+12%)

It is interesting to notice that for the rears, going from the 265 to the 275 does not increase to contact patch width by much (only 0.2in) but the weight is significantly increased (+2.9lb). The fronts do get more thread width (0.4in) for less weight increase (+1.3lb). IMO, tire weight is an important factor since it has impact on unsprung weight AND rotational inertia (especially since the tires are at the extreme edge of the rotating circumference).

This leaves me wondering about a 255/265 setup. I run a square 275 setup at the track that makes the car nice and neutral. A 255/265 combo would also be closer to a square setup to help get rid of the anoying M3 understeer.

Any thoughts?
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      04-23-2013, 08:59 AM   #2
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Interesting - I thought the gain in thread width would be closer to 10 mm = .4 inches.

I'm also now on 255/275 PSS on my 220Ms and am loving them - haven't gotten them to the track yet (will this summer), but have a weekend full of driving hill country back roads coming in a couple days.

The additional 3 lbs at the rear corners is not insignificant, but my rationale for going wider was that the car is not wanting for power, but could use some more grip on launch and in tight curves and corners.

What was BMW's reasoning for the 20 mm stagger from the factory? Obviously more meat in the rear allows for better acceleration, but the 245s in the front may be there only for safety's sake, to build in some understeer for less experienced drivers.

Interested in what others have to say, and your results if you go with the 255/265, OP.
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      04-23-2013, 09:05 AM   #3
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Not sure about the constant M3 bashing about being understeering. I was at the Nürburgring last weekend and when the car would lose grip it did so on the rear axle. OK, I was running with Euro-MDM on but also with DSC off I can't complain about understeer.

That being said, 255/265 should be fine in terms of circumfence.
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      04-23-2013, 09:12 AM   #4
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Quote:
Originally Posted by davesaddiction View Post
Interesting - I thought the gain in thread width would be closer to 10 mm = .4 inches.

I'm also now on 255/275 PSS on my 220Ms and am loving them - haven't gotten them to the track yet (will this summer), but have a weekend full of driving hill country back roads coming in a couple days.

The additional 3 lbs at the rear corners is not insignificant, but my rationale for going wider was that the car is not wanting for power, but could use some more grip on launch and in tight curves and corners.

What was BMW's reasoning for the 20 mm stagger from the factory? Obviously more meat in the rear allows for better acceleration, but the 245s in the front may be there only for safety's sake, to build in some understeer for less experienced drivers.

Interested in what others have to say, and your results if you go with the 255/265, OP.
Michelin quotes only a 7mm increase in overall width going from 265 to 275. What is even more telling is that Tire Rack quotes an increase of only 0.2in in thread width.

As a general rule, for a given inflation pressure, wider tires will improve lateral grip at the expense of longitudinal grip. So more meat in the rear does not necessarily yield better acceleration.

So if you want to get better launch traction out of wider tires, you need to run lower pressures.

As you, I believe the factory staggered setup from the factory is mostly there for safety reasons, to bring more understeer to the general balance of the car. IMO, in stock form, the M3 has plenty of rear grip compared to the front. My car is so much better balanced and controlable with my square track setup.

I am also very happy with my current 255/275 PSS setup. It is just that looking at the data, I am wondering if it would not be better going back to the stock 245/265 setup or even try the 255/265 combo. I mostly find that the extra width provided by the 275 is not worth the extra 3lb.

Last edited by CanAutM3; 04-23-2013 at 09:24 AM.
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      04-23-2013, 09:21 AM   #5
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Quote:
Originally Posted by ChrisDUS View Post
Not sure about the constant M3 bashing about being understeering. I was at the Nürburgring last weekend and when the car would lose grip it did so on the rear axle. OK, I was running with Euro-MDM on but also with DSC off I can't complain about understeer.

That being said, 255/265 should be fine in terms of circumfence.
If you give too much throttle with the steering wheel turned, the rear will break loose, no rocket science here. However, in steady state cornering, the front tires slip more than the rear, this is the definition of understeer.

Have you ever tried a square setup on the M3? It really changes the character of the car when pushed closer to the limit. Not something you would notice at 8/10 though.
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      04-23-2013, 09:24 AM   #6
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Quote:
Originally Posted by CanAutM3 View Post
As a general rule, for a given inflation pressure, wider tires will improve lateral grip at the expense of longitudinal grip. So more meat in the rear does not necessarily yield better acceleration.
Gotcha. The increased grip I'm feeling at launch is purely from the better compound of the PSS compared to the old PS2s (and Conti DSW winters), not the increased width.
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      04-23-2013, 09:33 AM   #7
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Quote:
Originally Posted by CanAutM3 View Post
If you give too much throttle with the steering wheel turned, the rear will break loose, no rocket science here. However, in steady state cornering, the front tires slip more than the rear, this is the definition of understeer.

Have you ever tried a square setup on the M3? It really changes the character of the car when pushed closer to the limit. Not something you would notice at 8/10 though.
This was not under high throttle application. Rather medium speed corner, maybe 140kph. The situation can be seen on the 3rd video here somewhere in the middle (miss-hit-miss corner, can look up the timestamp at home. At work, youtube is blocked): http://www.m3post.com/forums/showthread.php?t=831103

I have never tried a square setup M3 as it's not just plug and play, at least not in Germany. I ran a square setup on my previous E46 330i and it was fine. But this was understeering a lot in stock form (also square though).
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      04-23-2013, 11:46 AM   #8
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Quote:
Originally Posted by CanAutM3 View Post
Michelin quotes only a 7mm increase in overall width going from 265 to 275. What is even more telling is that Tire Rack quotes an increase of only 0.2in in thread width.

As a general rule, for a given inflation pressure, wider tires will improve lateral grip at the expense of longitudinal grip. So more meat in the rear does not necessarily yield better acceleration.

So if you want to get better launch traction out of wider tires, you need to run lower pressures.

As you, I believe the factory staggered setup from the factory is mostly there for safety reasons, to bring more understeer to the general balance of the car. IMO, in stock form, the M3 has plenty of rear grip compared to the front. My car is so much better balanced and controlable with my square track setup.

I am also very happy with my current 255/275 PSS setup. It is just that looking at the data, I am wondering if it would not be better going back to the stock 245/265 setup or even try the 255/265 combo. I mostly find that the extra width provided by the 275 is not worth the extra 3lb.
The width of the wheel the tire is mounted on will have an effect on the installed section and tread widths of the tire. On TireRack, they have the 265/40-18 and 275/35-18 PSS tires mounted on the same 9.5" wide wheel. For comparison, they also have a 265/45-18 mounted on an 11" wide wheel which results in a section width of 12.3" vs. 10.7" for the 265/40-18 mounted on a 9.5" wide wheel.
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      04-23-2013, 03:02 PM   #9
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Quote:
Originally Posted by M3SQRD View Post
The width of the wheel the tire is mounted on will have an effect on the installed section and tread widths of the tire. On TireRack, they have the 265/40-18 and 275/35-18 PSS tires mounted on the same 9.5" wide wheel. For comparison, they also have a 265/45-18 mounted on an 11" wide wheel which results in a section width of 12.3" vs. 10.7" for the 265/40-18 mounted on a 9.5" wide wheel.
Agreed about the impact of the wheel width. The impact of the 265 vs 275 is on a 19x9.5" wheel is directly applicable to my situation (the rear 220M are 9.5").

The width of the 245 vs 255 is not as evident to compare since the 245 is measured on a 8.5" wheel and the 255 on a 9" wheel.

I am very surprised, not to say a bit sceptical, about a 1.5" difference in width of a 265 tire due a 1.5" change in wheel width. That seems like a lot. Can you quote the reference?

Last edited by CanAutM3; 04-23-2013 at 03:20 PM.
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      04-23-2013, 04:33 PM   #10
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Quote:
Originally Posted by CanAutM3 View Post
Agreed about the impact of the wheel width. The impact of the 265 vs 275 is on a 19x9.5" wheel is directly applicable to my situation (the rear 220M are 9.5").

The width of the 245 vs 255 is not as evident to compare since the 245 is measured on a 8.5" wheel and the 255 on a 9" wheel.

I am very surprised, not to say a bit sceptical, about a 1.5" difference in width of a 265 tire due a 1.5" change in wheel width. That seems like a lot. Can you quote the reference?
265/275 on 220 - ok

I'm running 255 and 265 on 9.5" wide wheels. I was forced to run a 255 with my old Moton suspension setup because the 265 would rub against the F strut; however, I've switched to a JRZ setup and have clearance for a 265

The source for the 265 on an 11" wheel is TireRack. You probably know this but an 11" wheel is actually 12" wide. This is true of any wheel - 1" wider than the measured width. This is because of how the wheel width is measured.
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      04-30-2013, 04:15 PM   #11
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Are you running 255/35/19 or 255/30/19 on front? Have you thought about running the 30s to lower the car ? Based on my calculations that would lower the car .75 inch based on the diameter stats compared to the OEM 245/35/19.
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      04-30-2013, 07:45 PM   #12
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Quote:
Originally Posted by kartracer12 View Post
Are you running 255/35/19 or 255/30/19 on front? Have you thought about running the 30s to lower the car ? Based on my calculations that would lower the car .75 inch based on the diameter stats compared to the OEM 245/35/19.
No, I am using 255/35 to keep the diameter as close to stock as possible. The 255/35 is barely 1% bigger in diameter than the 245/35. The 255/30 is 2.8% smaller.

BTW, a 255/30 will lower the car by about 3/8" compared to a 245/35, not 3/4" (you need to consider the radius change and not the diameter change) .

Last edited by CanAutM3; 04-30-2013 at 08:08 PM.
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      04-30-2013, 08:18 PM   #13
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Any updates on how you have found this combo on road and track?
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      05-01-2013, 06:12 AM   #14
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Any updates on how you have found this combo on road and track?
Cannot provide feedback yet, I have not yet decided what option to go with...
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      05-01-2013, 06:46 AM   #15
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Really good discussion guys. I'm thinking about going 255/275, but 255/265 is also an interesting proposition, especially now that you mention the 2+ lbs increase. I had no idea it was that much.
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      05-01-2013, 10:13 PM   #16
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I asked this in another thread, but can you install a 265 square setup on the 220s? Would the front wheel support this size?
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      05-02-2013, 06:46 AM   #17
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Quote:
Originally Posted by M3amigos View Post
I asked this in another thread, but can you install a 265 square setup on the 220s? Would the front wheel support this size?
The front 220M wheels are 8.5" wide. Michelin recommends installing the 265/35R19 PSS on 9.0" to 10.5" wide rims. So I don't believe 265/35 in front is an option with the stock 220Ms.
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      05-02-2013, 06:52 AM   #18
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Quote:
Originally Posted by W/// View Post
Really good discussion guys. I'm thinking about going 255/275, but 255/265 is also an interesting proposition, especially now that you mention the 2+ lbs increase. I had no idea it was that much.
According to the michelin webside, it is actually closer to 3lbs . They quote the weight in kg to one decimal point. The difference is 1.3kg, which equates to 2.9lbs. On the tire rack website, the weights are quoted in lbs and rouded up the the nearest unit, so some precision is lost.
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      05-02-2013, 07:00 AM   #19
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Quote:
Originally Posted by CanAutM3 View Post
According to the michelin webside, it is actually closer to 3lbs . They quote the weight in kg to one decimal point. The difference is 1.3kg, which equates to 2.9lbs. On the tire rack website, the weights are quoted in lbs and rouded up the the nearest unit, so some precision is lost.
The more I think about it, the more I just don't think 2% thread width is worth adding 3 lbs to your weight! I'll really need to do my research. I feel like I can use slightly more traction now that I have test pipes and a stage 2 tune. But I wouldn't say the traction is horrible, and having 12mm spacers also took care of the aesthetics.

Definitely let us know what you end up doing. 255 in the front I will definitely do though.
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      05-02-2013, 08:36 AM   #20
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Quote:
Originally Posted by CanAutM3 View Post
The front 220M wheels are 8.5" wide. Michelin recommends installing the 265/35R19 PSS on 9.0" to 10.5" wide rims. So I don't believe 265/35 in front is an option with the stock 220Ms.
Oh ok, that clears things up...265s would be a stretch...
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      05-12-2013, 06:25 PM   #21
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I think I'm going to end up going 255/265 combo you guys. 12% increase in weight at the rear is just a little too much for me. 6% at the from + more contact patch at the front might work for me.

Unfortunately, I just changed the fronts like less than 2 months ago.
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      05-12-2013, 07:01 PM   #22
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I feel as though you all spend far too much time on the internet..........Wider tires will help performance.
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