E46 M3 tyre sizes (data)

[MPETT]

For those of you out there wondering what effect fitting different tyre widths/profiles has on rolling circumference and if this will cause a problem with DSC and traction control systems.

I saw a set of Michelin SP2 on ebay that were not a standard size so I worked out the rolling circumference difference between the normal 19" tyre package and that of the CSL's standard tyre sizes, to see if the set on ebay would cause me any trouble.

In case you're interested or want to use my calcs for other comparisons.

Width / Profile = Side wall height

225/40 = 90
235/35 = 82.25
235/40 = 94
255/35 = 89.25
265/35 = 92.75
265/30 = 79.5


Ebay tyre package
225/40 = 90
+
265/35 = 92.75
= +5.5mm (overall difference in tyre wall thickness front/rear)

R19" * 2.56= 480.64mm

Front: 480.64mm + (2*90)= 660.64 *pie = 2075.46
Rear: 480.64mm + (2*92.75) = 666.14 *pie = 2092.74

= 17.28mm larger circumference on rear

CSL set up
235/35 = 82.25
+
265/30 = 79.5
= +5.5mm (overall difference in tyre wall thickness front/rear)

R19" * 2.56= 480.64mm

Front: 480.64mm + (2*82.25) = 645.14*pie = 2026.76
Rear: 480.64mm + (2*79.5) = 639.64*pie = 2009.48

= 17.27mm larger circumference on front


Standard setup
225/40 = 90
+
255/35 = 89.25

= +1.5mm (overall difference in tyre wall thickness front/rear)

R19" * 2.56= 480.64mm

Front: 480.64mm + (2*90)= 660.64 *pie = 2075.46
Rear: 480.64mm + (2*89.25) = 658.5 *pie = 2068.73

= 6.73mm larger circumference on rear

So in conclusion, the ebay package compared to the CSL tyres results in the difference in circumference between the front and rear of 0.01mm.


Tyre prices (20/10/2010)

Toyo PROXES T1-R 225/35 ZR19 88Y RF with rim protection ridge, BSW Fully Fitted £ 161.90 2 £ 323.80
Toyo PROXES T1-R 255/35 ZR19 96Y RF with rim protection ridge, BSW Fully Fitted £ 211.00 2 £ 422.00

Total amount 4 £ 745.80

Kumho ECSTA SPT KU31 225/40 R19 93Y XL with rim protection ridge, BSW Fully Fitted £ 142.20 2 £ 284.40
Kumho ECSTA SPT KU31 255/35 R19 96Y XL BSW Fully Fitted £ 153.00 2 £ 306.00 Total amount 4 £ 590.40


Michelin Pilot SPORT PS2 255/35 ZR19 96Y XL with rim protection ridge, RO1 BSW Fully Fitted £ 262.00 2 £ 524.00
Michelin Pilot SPORT PS2 225/40 R19 93Y XL with rim protection ridge BSW Fully Fitted £ 239.20 2 £ 478.40
Total amount 4 £ 1002.40

Ebay tyres £650 delivered (not bad at all! a £450 saving)

[shim]

MPETT said:

So in conclusion, the ebay package compared to the CSL tyres results in the difference in circumference between the front and rear of 0.01mm.


)

BUT thats not the whole story as with one the rear is bigger and the other the front is bigger so overall you are changing the ratio by a considerable amount as changing from CSL set up to ebay set up you are effectively increasing the front to rear circumferences by 35.55mm.

Edited by shim on Tuesday 2nd November 00:04

[TheEnd]

you can use this is you want to avoid some of the maths

http://www.miata.net/garage/tirecalc.html

[MPETT]

I've currently got the standard set up so the the end result is an increase in the rear tyre's rolling circumference of 24.01mm from my current set up. I'm concluding that seeing as other configurations allow for this variance, that I'll be OK with the ebay package. Fingers crossed!!

[MPETT]

TheEnd said:

you can use this is you want to avoid some of the maths

http://www.miata.net/garage/tirecalc.html

If only I'd seen this before I'd done all the maths!!

[MPETT]

The same chap has another set on eBay. The set i bought are pristine and from the sidewall u can work out their age. My set were 2.5 years old so well within the 5 year lifespan. Happy bidding;)