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      12-30-2015, 04:26 AM   #1
brad850csi
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Spent a lot of time researching wheel & tyre, sizes & offsets today

While I still don't have an M6 yet, I've decided that an M6 will be my next car. Now of course as I love modding I've already decided on a list of things I'd like to do and it seems that from the performance aspect the S63Tu engine is constantly evolving - most posts are on the M5 section of the forum.

Wheel size and tyre size should be easy to figure out, the cars dimensions aren't changing!

This post will talk about the rears, I'll do the same analysis of the fronts tomorrow. It's mostly rambling by me about how to get 335 wide tyres onto an M6 and the hunt for a suitable offset wheel! Anyway, into it:

The stock rear wheels are 20x10.5 19mm, which gives us a track of 1612mm, thus the hubs at the rear must be 1650mm from mounting face to mounting face.

A 295/30/20 tyre does not actually have a 295mm wide tread at the top of the tyre however, according to tirerack who measure their tyres individually, based on the page below, a PSS in 295/30/20 is only 292mm wide, plus or minus about 2mm (otherwise it would be showing 11.4 or 11.6 inches on their site

http://www.tirerack.com/tires/tirete...jsp?techid=201
http://www.tirerack.com/tires/tires....omCompare1=yes

With the stock 295/30/20 setup and no spacers, the outer corner of the tyres will be at 1612mm + 292mm = 1904mm, and the inner corner will be at 1320mm.

Plenty of people have run 305/30/20 tyres on their car on the stock 20x10.5" 19mm wheels, these tyres are 300mm wide, so their outer and inner corners will be at 1312mm and 1912mm.

If you run a spacer on stock 295/30/20 tyres, you end up with 1350mm and 1934mm.


I've also looked up 640i/650i, they have a hub to hub spacing of 1725mm, which is why people can fit stock M5 wheels which are 20x10.0 34mm with a 295mm tyre, and not the stock M6 wheels with their 20x10.5 and 19mm specification.

A 650i with this stock M5 setup is 1365mm and 1949mm, on this thread http://www.6post.com/forums/showthre...ghlight=vaio23

This is effectively the equivalent of running an M6 on 22.5mm spacers with stock wheels and tyres which is more than any M6 owner has done that I can find.


However that still only leaves 318.5mm to play with, well short of the 335/30/20 or 335/25/20 that I'd really like to get to, mainly because I want to run 20" wheels, 315/30/20 doesn't exist in normal tyres (semi slicks only) and 325/30/20 only comes in Dunlop Sport Maxx GT for the old AMG SL65 Black edition, I suspect that tyre size will go away given a few more years, equally the PSS in 305 probably is better than that GT in 325 anyway!

If we assume that 1949mm is the maximum based on the 650i that vaio23 owns, then a car with 325mm tyres must have an offset of around 17mm at the most aggressive I believe, based on a Pzero 325/25/21 having a 333mm tread width. Interestingly, the 335/30/20 Pzero has the same 333mm tread with and a PSS has only a 330mm tread width - so it appears that I really just need to worry about people with the 325/35/21 fitment. This would make the inner measurement around 1285mm or so, which curiously is right where an M5 is with it's stock setup - actually 1290mm for inner and 1874mm for outer, and I know a few people have run 305/30/20 on their stock wheels which is 1282mm and 1882mm - not relevant here but this is out of spec, 305/30/20 should be on 10.5" wheels at the narrowest, M5 wheels are of course 20x10"

http://f10.m5post.com/forums/showthr...30%2F20&page=3


So ultimately this is a question to ask if anyone is running:

295's on wheels with an offset that is lower than or similar to 4mm, higher than or similar to 23mm
305's on an offset that is lower than or similar to 8mm or higher than or similar to 19mm - or is anyone running 305's with spacers at all?
325's at all, what is your offset?
Has anyone ever fitted M5 rear wheels to an M6 with any size tyre at all and did it work? Maybe a follow up to this is how many people have access to both M5 stock wheels and an M6?

If I get a few more figures from a few more people it may just help us all learn how to get to 335mm wide rears.

Before anyone asks, I haven't found a wheel company that is sure 335's will fit, hence doing my own research on it.
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      12-30-2015, 05:08 AM   #2
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I have always found this site most useful in calculating wheel and tyres sizes compared to the original fitting http://www.rimsntires.com/specspro.jsp
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      12-30-2015, 05:35 PM   #3
brad850csi
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Thanks, I have used that one and I also like this one because it gives you a better idea of how the tyre might be stretched or not http://www.willtheyfit.com/

This one is good too because it suggests similar sizes http://www.wheel-size.com/calc/


From my earlier post I've managed to find someone, Tuner1, who is running a 28mm offset with 305/30/20 wheels which means his inner measurement is 1294mm.

This now takes me to 327.5mm that I have to play with, so nearly there!

Someone running a 325mm tyre or if anyone has tried a stock M5 rear wheel on an M6 would be great to hear from!
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      01-04-2016, 12:54 AM   #4
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Quote:
Originally Posted by brad850csi
Thanks, I have used that one and I also like this one because it gives you a better idea of how the tyre might be stretched or not http://www.willtheyfit.com/

This one is good too because it suggests similar sizes http://www.wheel-size.com/calc/


From my earlier post I've managed to find someone, Tuner1, who is running a 28mm offset with 305/30/20 wheels which means his inner measurement is 1294mm.

This now takes me to 327.5mm that I have to play with, so nearly there!

Someone running a 325mm tyre or if anyone has tried a stock M5 rear wheel on an M6 would be great to hear from!
I ran 325s on my M6. Can't do that on stocks though, you need aftermarket wheels with at least a 11.5 barrel (I had a 21x12). 325 is the widest you can go without some serious rubbing issues or having to mess with the camber settings or doing body panel modifications.
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      01-04-2016, 09:13 PM   #5
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DirtyM, I know that Joe at Trinity and M6Beast have both run R888's in 315/30/20, but not on stock wheels as far as I know.

http://www.6post.com/forums/showthread.php?t=1057576
http://www.6post.com/forums/showthread.php?t=1148142
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      01-04-2016, 10:22 PM   #6
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Quote:
Originally Posted by DirtyM View Post
So today I signed up for shift Sectors race in February. I have modded my car with Gintani down pipes and custom Tune. I am trying to figure out if i can run toyo R888 on my stock rims to avoid traction issues...Thing is a monster!

What are your guys thoughts?
Quote:
Originally Posted by brad850csi View Post
DirtyM, I know that Joe at Trinity and M6Beast have both run R888's in 315/30/20, but not on stock wheels as far as I know.

http://www.6post.com/forums/showthread.php?t=1057576
http://www.6post.com/forums/showthread.php?t=1148142
I believe R888 315/30/20 can be installed on 10.5" rims!

http://www.tirerack.com/tires/tires....160105042208:s
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      01-05-2016, 01:21 PM   #7
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Weirdly the two sizes for the R888 in 20" are perfect for M6's, and are probably a really good option for anyone wanting to go to the track or drag strip

They aren't really a daily drive tyre though! Even in the dry they are really spongey and squirrely. I last ran them on 17x9.5" in 255/40/17 so they had a slight stretch to them and even then they felt like you were just wandering all over the place until I arrived at the race track
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      01-05-2016, 07:17 PM   #8
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Quote:
Originally Posted by M6-Coupe View Post
I believe R888 315/30/20 can be installed on 10.5" rims!

http://www.tirerack.com/tires/tires....160105042208:s
Yah Ive seen several people running those tires, I wonder if I order it and the fitment is not right will they take it back or return it...

If not i want to find some racing rims and tires that i can slap on to track or drag...Bmw needs to come out with AWD option for these M cars soon!
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      01-05-2016, 07:18 PM   #9
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Quote:
Originally Posted by brad850csi View Post
Weirdly the two sizes for the R888 in 20" are perfect for M6's, and are probably a really good option for anyone wanting to go to the track or drag strip

They aren't really a daily drive tyre though! Even in the dry they are really spongey and squirrely. I last ran them on 17x9.5" in 255/40/17 so they had a slight stretch to them and even then they felt like you were just wandering all over the place until I arrived at the race track
Just wish BMW went with an 11 in rim in the back...How did the tires do in the wet? Was there even any traction?
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      01-05-2016, 08:07 PM   #10
brad850csi
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I didn't drive them in the wet but you won't find anyone at all saying that is a good idea at all!
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