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      05-12-2013, 08:46 PM   #23
CanAutM3
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Quote:
Originally Posted by RenoE92M3 View Post
I feel as though you all spend far too much time on the internet..........Wider tires will help performance.
Everything is a compromise. Wider tires will improve performance in some areas and will reduce performance in other areas.
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      05-13-2013, 08:14 AM   #24
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Quote:
Originally Posted by W/// View Post
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.
I would never say having new rubber on the car is unfortunate. I do like the 255/265 tire set-up idea. For my use of the car the stock set up is good but a little bit more bite up front would be great.
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      06-02-2013, 02:41 PM   #25
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OK, so I have done a little extrapolation based on pictures (see thread http://www.m3post.com/forums/showthread.php?t=848092) and some math to figure the difference between the 265 and 275.

Here are the results for thread block width in mm

265/35R19 (Total thread width 254mm)
47+32+32+32+47 = 191 (75%)
275/35R19 (Total thread width 259mm)
58+38+38+38+58 = 230 (89%)

So even if the 275 total contact patch width is only 5mm wider than the 265 contact patch, it offers 39mm more rubber contacting the road because of the narrower grooves. This is 20% more. This could justify the 2.9lb of extra weight (+12%).

Decisions, decisions...

Last edited by CanAutM3; 06-02-2013 at 07:43 PM.
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      06-02-2013, 03:37 PM   #26
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Quote:
Originally Posted by CanAutM3 View Post
OK, so I have done a little extrapolation based on pictures and some math to figure the difference between the 265 and 275.

Here are the results for thread block width in mm

265/35R19 (Total thread width 254mm)
47+32+32+32+47 = 191 (75%)
275/35R19 (Total thread width 259mm)
58+38+38+38+58 = 230 (89%)

So even if the 275 total contact patch width is only 5mm wider than the 265 contact patch, it offers 39mm more rubber contacting the road because of the narrower grooves. This is 20% more. This could justify the 2.9lb of extra weight (+12%).


Decisions, decisions...
Hmmm. Interesting...
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      06-04-2013, 07:47 AM   #27
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Quote:
Originally Posted by CanAutM3 View Post
OK, so I have done a little extrapolation based on pictures (see thread http://www.m3post.com/forums/showthread.php?t=848092) and some math to figure the difference between the 265 and 275.

Here are the results for thread block width in mm

265/35R19 (Total thread width 254mm)
47+32+32+32+47 = 191 (75%)
275/35R19 (Total thread width 259mm)
58+38+38+38+58 = 230 (89%)

So even if the 275 total contact patch width is only 5mm wider than the 265 contact patch, it offers 39mm more rubber contacting the road because of the narrower grooves. This is 20% more. This could justify the 2.9lb of extra weight (+12%).

Decisions, decisions...
Ok now we are talking. ~20% for 3 lbs is something I can deal with. Thanks for the heads up and let us know what you decide to go with.

I'm going to stick with 265 for one more round, as my front (245 ) are still new. Then I might go with 255/275 afterall.
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      06-10-2013, 11:03 PM   #28
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Quote:
Originally Posted by W/// View Post
Thanks for the heads up and let us know what you decide to go with.
Quote:
Originally Posted by mlhj83 View Post
Any updates on how you have found this combo on road and track?
I have decided to stick with the 255/275 setup based on the additional "rubber on the road" provided by the 275.

We had a wet track day this past Saturday and those PSS are really great in the wet. I was passing all types of 4WD cars
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      06-25-2013, 10:51 AM   #29
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Even though the 275s are not much wider, you need to look at the thread pattern, the 275s have smaller grooves and much more rubber touching the ground.

I'll see if I can dig up the pic and post it here also, it was in another thread.
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      06-25-2013, 11:03 AM   #30
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Quote:
Originally Posted by tdott View Post
Even though the 275s are not much wider, you need to look at the thread pattern, the 275s have smaller grooves and much more rubber touching the ground.

I'll see if I can dig up the pic and post it here also, it was in another thread.
I am the one that started the other thread

See post #25 in this thread.

Thanks anyway
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      06-25-2013, 11:06 AM   #31
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Yup that's the one!

Thanks for doing that it's useful info, it convinced me to go 275/255 on my next set.
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      06-25-2013, 06:42 PM   #32
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Some more food for thought:

1. The wheel widths have a significant impact on the width of the actual contact patch. A stretched tire will allow for maximum contact patch, however too stretched will upset the tires ability to properly handle lateral loads.

2. Too narrow a wheel obviously causing bowing resulting in a reduced contact patch.

3. Tire weight is more important with the front tires than the rear. The fronts are involved in steering and take the bigger initial hit over bumps, etc. Hence you will feel the extra rotaional mass more with the fronts than the rear. That's not to say the rear weight is not a factor at all, just not as much as the fronts.

4. 245/265 is really optimal on the 8.5/9.5 set-up that the M3 comes with. Honestly I am surprised they didn't move to a 255/275 set-up with the ZCP package. The extra 0.5" wheel width makes the 359 wheels perfectly suited to take 255/275. At stock offset, there is also no rubbing with 255 on the ZCP wheel.
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      06-26-2013, 09:32 AM   #33
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Quote:
Originally Posted by LarThaL View Post
1. The wheel widths have a significant impact on the width of the actual contact patch. A stretched tire will allow for maximum contact patch, however too stretched will upset the tires ability to properly handle lateral loads.

2. Too narrow a wheel obviously causing bowing resulting in a reduced contact patch.
Agreed. However the 220M wheel widths still are within the tire manufacturer's recommended rim widths for 255/275. Further, the slight 12/7mm increase in tire width does not alter the shape of the contact patch that much.

Quote:
Originally Posted by LarThaL View Post
3. Tire weight is more important with the front tires than the rear. The fronts are involved in steering and take the bigger initial hit over bumps, etc. Hence you will feel the extra rotaional mass more with the fronts than the rear. That's not to say the rear weight is not a factor at all, just not as much as the fronts.
I need to point out that greater tire weight has two distinct detrimental impacts on performance. First, increasing unsprung weight reduces the suspension responsiveness since there is more mass to move up and down to react to road imperfections; which has a negative impact on handling. Second, rotational inertia increases the energy required to accelerate or decelerate the rotation of the wheel; which has a negative impact on acceleration and braking.

I cannot really comment on the fact that unsprung weight has less impact in the rear, I am not enough of an expert in suspension design. However, increasing rotational inertia front or rear has the same detrimental impact on acceleration and braking.

Quote:
Originally Posted by LarThaL View Post
4. 245/265 is really optimal on the 8.5/9.5 set-up that the M3 comes with. Honestly I am surprised they didn't move to a 255/275 set-up with the ZCP package. The extra 0.5" wheel width makes the 359 wheels perfectly suited to take 255/275. At stock offset, there is also no rubbing with 255 on the ZCP wheel.
8.5/9.5 wheel widths fall pretty much in the middle of Michelin rim width recommendation for the 245/265. Although I actually prefer the 255/275 setup on my 220Ms for the additional grip it provides. It is a question of personal choice I guess. I cannot directly compare the two setups though, because when I moved to the 255/275 setup I also switched from PS2 to PSS. However I now feel the car is better balanced with more front end bite; it has better turn-in and slightly less understeer.

I agree that BMW could have gone with a 255/275 combo for the ZCP wheels. They may have decided to stay with the 245/265 for comercial/logistics reasons

Last edited by CanAutM3; 06-26-2013 at 09:37 AM.
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      06-26-2013, 10:05 AM   #34
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I almost did the 255/40-18 and 265/40-18 but decided I'd rather save the $50. If there was a 275/40-18 PSS I definitely would have done it, but alas
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