19" tyre sizes for CSL reps

[mr wilks]

Here we go, just for reference!

Wheel is 9.5j 19"

The top picture is 265/35/19. They felt great and the ride was much more forgiving, however they looked a little 'balloony' for me and because I'm lowered on Eibach, they were too close to the arches for comfort. I'm sure they would be fine on standard springs, and possibly M springs.

The bottom pic is 265/30/19 which look great and don't rub, but the ride is pretty harsh.

Any reason why you didn't go 255 35 19 :?

 

[MrPT]

That looks pretty good to me, but I quite like the "GT racer" look. Coupe would carry them a little better too, I reckon, but the visual mismatch with the fronts might be weird.

 

[STUBOY2UK]

Any reason why you didn't go 255 35 19 :?

I'm not sure really, that would probably have been more sensible! There's not a huge amount of clearance even with the 265 30 19 running on Eibachs, so I think anything bigger would cause issues under heavy compression but a 255 35 19 would certainly have been better.

 

[Argenta]

I must say, after being used to my rear 265/35-19 I always think 265/30-19 look too small.
Also, they are much closer to original, correct diameter.

And also again, I have no trouble with a bit of tirewall...

 

[STUBOY2UK]

I must say, after being used to my rear 265/35-19 I always think 265/30-19 look too small.
Also, they are much closer to original, correct diameter.

Not sure what the ///M specs are, but in a non-M 265/30/19 is much closer to OEM spec than 265/35/19.

 

[Argenta]

May be true but not for the M.

 

[Philly_Sweden]

I must say, after being used to my rear 265/35-19 I always think 265/30-19 look too small.
Also, they are much closer to original, correct diameter.

Not sure what the ///M specs are, but in a non-M 265/30/19 is much closer to OEM spec than 265/35/19.

The correct M sizes are

235/35/19
265/30/19

 

[Argenta]

No Philly - we've been through this.

It's 225/45-18 front and 255/40-18 rear.
Diameter 660mm and 661mm.

The closest 19" alternative is:
235/35-19 front and 265/35-19 rear.

Diameter 647mm (-1.9% diff) and 668mm (1% diff).

To go 265/30-19 at the rear would mean a 642mm diameter (-3% diff).

 

[TomK]

The e46 m3 csl (the only S54 car that runs 235 & 265 widths) uses 235/35 & 265/30 19" from the factory. The 18" option for an e46M3 is the same as our cars 225/45 & 255/40.
If I was running 19s and wanted to increase width I would go with BMW's choice above. If I didn't want to increase the width I would go with the 19" spec for a normal e46 m3 which is 225/40 & 255/35. Worth noting though that a standard 19" m3 wheel is an 8j and the CSL wheel is 8.5j.

 

[Argenta]

This is a Z4 forum - not a M3 forum.

 

[TomK]

This is a Z4 forum - not a M3 forum.

Well yes, but given that a z4m nicks pretty much all it's running gear from an m3 I'd go along with what BMW did rather than a load of internet opinions about what might be the best tyre size

That said I run different 18" tyre sizes to oem, so I'll get back in my box

 

[Argenta]

Exactly, "pretty much"... The transmission and final gear is different, not even the S54 is identical to the M3.
I don't know why anybody would go against BMW original dimensions.

With smaller-than-std rear wheels the ride suffers, speedo/odometer misreads and looks suffer (matter of taste obviously but certainly to me). Also it doesn't help with the Z4M's notoriously low gearing which does make it a bit revvy on the highway.

 

[TomK]

Exactly, "pretty much"... The transmission and final gear is different, not even the S54 is identical to the M3.
I don't know why anybody would go against BMW original dimensions.

With smaller-than-std rear wheels the ride suffers, speedo/odometer misreads and looks suffer (matter of taste obviously but certainly to me). Also it doesn't help with the Z4M's notoriously low gearing which does make it a bit revvy on the highway.

Well I've never heard of the Z4M being referred to as low geared, it is geared in 6th for speeds that it is unable to pull. Off topic but I am very keen to shorten my final drive ratio, I have no need of gearing to 185mph or whatever it is.
If you're referring to me when saying can't understand why anyone would go against bmw's recommendations then I'd answer that I wanted to increase the width of the tyre slightly ala csl (I have the same power as one) and correspondingly bought wider rims to suit. One of the reasons I wanted to keep 18" as I agree a 265/30 19 is going to be a hard ride.
Thing is there is no bmw recommendation for our cars on 19" so regardless of whether the transmission or final drive are different I would be more concerned with suspension kinematics, and considering a csl is really not far from our cars in terms of weight that would be the direction I would choose when running a 19" on a csl wheel.
Also a 265/35 19 is a bit of a balloon no, and must weigh a fair bit more?
I guess there's no real correct answer here though

 

[Philly_Sweden]

I've never heard anyone running 265/35 before but it might work just fine. I still prefer running on OEM CSL tire spec and have always done before on 2 M3's and on my previous Z4M as well.

 

[TomK]

ignore.. brainfade edit post

 

[Argenta]

I never wrote Bmw has any "recommendations" regarding wheels?

I wrote "against Bmw original dimensions" - meaning OEM Bmw Z4M wheel size.

 

[TomK]

I never wrote Bmw has any "recommendations" regarding wheels?

I wrote "against Bmw original dimensions" - meaning OEM Bmw Z4M wheel size.

What I can't understand is, if you are so keen to keep oem bmw Z4M wheel size why you didn't go with 225/40 and 255/35 on your 19s which are the exact same diameter and width to oem 18s 225/45 & 255/40?

 

[Argenta]

Well, my mistake!
But I was looking for 235/265 tires I think because they match the wider rims best in width. Also, as above, the higher gearing and better comfort was further reasons.. Maybe next time!
I usually try to stay at least within 1% of original diameter (so 3% would be right out).

 

[TomK]

If I was running a fairly standard car on 19s that would be my choice personally...
Many M3 CS's came from the factory with the wider CSL 8.5" front (instead of the CS 8j front) and obviously the same 9.5j rears. These were delivered by BMW with 225/40 and 255/35 so you shouldn't have any worry there. (in terms of wheel width/vs tyre width)

 

[AlfaScozzesi]

If I was running a fairly standard car on 19s that would be my choice personally...
Many M3 CS's came from the factory with the wider CSL 8.5" front (instead of the CS 8j front) and obviously the same 9.5j rears. These were delivered by BMW with 225/40 and 255/35 so you shouldn't have any worry there. (in terms of wheel width/vs tyre width)

Think the CS wheels are only different on the fronts as you said 8J and 8.5J. The backs were 9.5J on both CS and CSL. Same part number as well.