Anyone Using Larger profile tyres ?

[buderim]

I have a 2004 Clk320 , I have F 8.5 225 40 18 R 9.5 255 35 18 , apart from the speedo reading being wrong would it do any harm to fit larger profile tires ? I was thinking of going up to 225 45 18 and 255 40 18 just to help the ride . According to wheel-size the tire is 26mm bigger diameter so it will make the car 13mm higher .

Has anyone here run a bigger sidewall ?

 

[Wolfie1]

I did when i had my calibra on top of throwing your speedo out i found the car didnt accelerate the same

 

[Bellow]

Have you considered smaller diameter wheels with higher profile tyres?

What is the 26mm increase in OD as a percentage of the original size? At a guess it is probably around 4-5% which may be acceptable re car's computers - but as alluded to, speedo will under-read (ditto odometer) and acceleration will be tardier.

Smaller rims with higher profile tyres is probably the best way to achieve this but obviously requires new/replacement wheels. It is larger wheels that are in demand though so maybe some scope there.

 

[Doodle]

I suspect the sizes you have in mind would not pass rego requirements. ISTR a figure of no more than +15mm dia being quoted.

 

[markjay]

If fitting larger-diameter wheels:

1. Top-end speed and economy while cruising will improve at the expense of acceleration.

2. The speedometer and odometer will under-read.

3. The tyres might foul the wheel arches or the dampers/struts during sharp turns or when the car is loaded.

4. You'll need to inform your insurer.

 

[m80]

The speedo likely reads over anyway, so the change would probably make it more accurate.

Are there any sizes detailed in the handbook that could make this change acceptable to you and not require insurance to be informed?

 

[Bellow]

The speedo likely reads over anyway, so the change would probably make it more accurate.

Are there any sizes detailed in the handbook that could make this change acceptable to you and not require insurance to be informed?

Whatever 'platform' the CLK is derived from surely has a 17'' wheel option - more likely as standard.

 

[markjay]

I think the OP's issue is that changing the tyre size to another permissible size will keep the overall diameter the same - or within tolerance - but it will also require (in the majority of cases) a change in rim size.

By opting for higher-profile tyres but keeping the width of the tyres and the internal diameter the same, the OP is hoping to be able to achieve a more comfortable ride without having to buy new rims.

This will work, but with the obvious side-effects that come with running a car on larger-diameter tyres.

 

[markjay]

If fitting larger-diameter wheels:

1. Top-end speed and economy while cruising will improve at the expense of acceleration.

2. The speedometer and odometer will under-read.

3. The tyres might foul the wheel arches or the dampers/struts during sharp turns or when the car is loaded.

4. You'll need to inform your insurer.

5. The ride height / road clearance will be greater.

6. The ride will be the softer and the handling less sporty, with more leaning into corners.

 

[Bellow]

6. The ride will be the softer and the handling less sporty, with more leaning into corners.

That isn't where the roll is generated and as the roll centres will be raised by a similar amount the roll angle will remain the same.
The slip angles will be greater though. Because of a more compliant sidewall and because of increased weight transference due to the slight raising of the car above ground level (raised roll centre heights).