Tyre profile

Chinnorbiker

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Your Mercedes
SLK
SLK300; 2010:
We have lots of potholes and speed bumps near me so I was thinking of changing my rear tyres from 245/30 to 245/40.
Comments welcome, please.
 

Blobcat

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Grange Moor
Your Mercedes
R171 SLK280, Smart R451, Land Rover 110 County SW, 997 C2S, R1250 GSA TE 40th, CBR600FP
You'll likely get an ESP warning as the system will detect a speed imbalance between front and rear wheels as you've change the overall circumference.
 

JBell

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Your Mercedes
C350 CDi Estate (GAD Edition)
SLK300; 2010:
We have lots of potholes and speed bumps near me so I was thinking of changing my rear tyres from 245/30 to 245/40.
Comments welcome, please.

Are you sure those sizes are correct??

SLK has a 245/40 R17 or 245/35 R18 on the rear

I would drop the pressures by 2psi before changing tyres
 

LostKiwi

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Midlands / Charente-Maritime
Your Mercedes
'93 500SL-32, '01 W210 Estate E240 (RIP), 02 R230 SL500, 04 Smart Roadster Coupe, 11 R350CDi
SLK300; 2010:
We have lots of potholes and speed bumps near me so I was thinking of changing my rear tyres from 245/30 to 245/40.
Comments welcome, please.
I'm not sure they would even fit if using the same rims.
That's an increase in diameter of almost 2".

The effects would be:
1. Your car will sit an inch higher.
2. It will seriously mess with steering geometry and handling.
3. Your speedometer will read 8% lower so may under read (which is illegal).
4. Your ESP, ABS and Cruise will cease to work.
5. You will need to inform your insurance company and list it as a modification and if you don't it may (almost certainly will given 4) void your insurance.
 

Gazwould

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Your Mercedes
C250 CDI
Just use manufacturer recommended sizes.

Any tyre calculator websites are an illusion of what is real world .
 

rf065

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Grossbritannien
Your Mercedes
SLC300 - C250d Estate 4 Matic & Z900rs
Are you sure those sizes are correct??

SLK has a 245/40 R17 or 245/35 R18 on the rear
Curious, sounds like he may have the wrong sized tyres already on the car. Mine has 245/35 x 18 on the rear.
 

mioba

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Nottingham and Köln
Your Mercedes
W124/E200, W220/S320CDI, W205/C200, W251/R350CDI 4Matic
Assuming the OP did not have the car from
new, seems a previous owner has pimped it.

As a start I would be incined to contact your local MB dealer in person and friendy ask for the buidsheet of the car and explain why. I am sure they would help especially if you mention (albeit fictionally) you want to buy the correct alloys from them (assuming they are not the spec ones).

Second everything LK has mentioned above.
 

Chrishazle

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Your Mercedes
S204 2008 C220CDI Elegance Estate Auto, 2008 R171 Facelift SLK280
Don't even need to ask the dealer for the build sheet, there's enough links on here to VIN decoder sites on which you enter your VIN and it gives you the build sheet which you can download - for free!

My SLK has the 17" staggered setup where the fronts are 225/45 and the rears 245/40, standard would have been 16's (don't know tyre sizes), on the staggered 17" setup you can run 225/45 all round without problems, but with the power of my 280 I'd be concerned about loosing 20mm of tyre width on the rear.
 

Blobcat

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Your Mercedes
R171 SLK280, Smart R451, Land Rover 110 County SW, 997 C2S, R1250 GSA TE 40th, CBR600FP
My SLK has the 17" staggered setup where the fronts are 225/45 and the rears 245/40, standard would have been 16's (don't know tyre sizes), on the staggered 17" setup you can run 225/45 all round without problems, but with the power of my 280 I'd be concerned about loosing 20mm of tyre width on the rear.
16” standard is 205 55 front and 225 50 rear ;)

I run 205 55 all round on the winters :)
 


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