tyre widths on 8.5/9.5 20" rims - CLS

[mid]

I need some new tyres!

my car is a 2006 W219 CLS and is fitted with replica AMG 20" wheels.
currently i have 265/30's on the back and 255/30's on the front. both appear to be the recomended sizes for the rim widths (8.5 front and 9.5 rear) but the tyres look very stretched - particularly on the back.

i'm looking at some 275/30 for the back which still appear to be in spec for the 9.5 rims, but would 265/30's go on the front 8.5Js? most places seem to recomend 255 as max but as before this looks 'stretched' to me and the 'rim protectors' are no where near the rim!

anyone got any expereince with this set up? internet searches show 265's on 8,5Js but usually on smaller diameter wheels with more sidewall.

 

[daveenty]

I have 285/30 on my 9.5" rims at the rear, albeit 19" and 255/35 on the 9Js at the front.I think a 265 may be pushing it a little on an 8.5, though if you have a friendly tyre fitter it may be worth trying one for fit?

The 285s are an excellent fit and the rim protector is where it should be, i.e. protecting the rim, as you can hopefully see here: -

 

[C43AMG]

On my CL they are 8.5 255/35/ZR20XL Front 9.5 275/35/ZR20XL Rear

 

[renault12ts]

I always thought that with different width tyres the profile ratios should also be different to maintain the same rolling radius?

 

[whitenemesis]

Should be 285/30 rear and 255/35 fronts

The rim protectors on the Pirelli tyres was almost non-existent but with the Michelins there was a really useful protuberance. What tyres are you using?

 

[mid]

this is where i get confused as every rim/tyre chart i can find suggest 275 is max for 9.5J but a lot of people suggesting 285 is ok - and looking at my current 265 set the rims should easily accomodate 285.

the fonts with 255/30 are currently less stretched than the rear but still think they could do with being a bit wider hence the question about 265's

currently running michelin pilots on the rear and some achillies rubbish on the front... dont really want to spend big money but happy to go upto around £160 a corner

id like a matching set all round (just my ocd really)

khumo Ecsta SPT KU31 seem to be my best bet at the moment with 275/30 rear but they dont do a 255/30 for the front.... they do a 255/35 though

 

[whitenemesis]

As pointed out above the fronts should be /35 and the rears /30 aspect ratio to maintain the correct rolling circumference

255/35 front and 285/30 rear is the OEM size for the AMG wheels

 

[renault12ts]

OP do a little research into aspect ratios so that you understand why they can't be the same front and rear when the rear tyres are wider than the fronts.

 

[KennyN]

On my stock CLS

8.5 x 18 = 245 40 18
9.5 x 18 = 275 35 18

Moving up to shortly to 19`s which should keep the rolling dia within spec for the speedo etc.

8.5 x 19 = 245 35 19
9.5 x 18 = 275 30 19

Based on the above logic and on 20" then i would imagine the profile should be reduced even further to 30 F + 25 R

Kenny

 

[mid]

just been going by whats on already on there at the minute that i know fits and doesnt rub etc...

using an online tyre size calculator
275/30/20 rears are 26.5 overall diameter,
255/35/20 fronts are 27".
255/30/20 are 26"
so 1/2" difference either way- depends if bigger rears or bigger fronts is better?

original wheels were 17's with:
245/45/17 all round which is 25.7"
i guess this is why the original owner went for the 255/30 as this is as close as possible(26").
current set up suggests my speedo is under reading by about 2.3% (assuming it reads off the driven wheels?)

 

[Dougster CLS]

On my stock CLS

8.5 x 18 = 245 40 18
9.5 x 18 = 275 35 18

Moving up to shortly to 19`s which should keep the rolling dia within spec for the speedo etc.

8.5 x 19 = 245 35 19
9.5 x 18 = 275 30 19

Based on the above logic and on 20" then i would imagine the profile should be reduced even further to 30 F + 25 R

Kenny

What he said