Tyre size 255/40 on a 3.0?

I

Imaginationcreations

Member
Has any body run a 255/40/18 on the 3.0 108's its looking like tyre time and i like the look of a big tyre just wondered if any one had any experience?

cheers

chris
 
Are these not the standard size tyres on the //M wheel? If so, I'm running them on mine no issues, but my offset is further out than the 108's.
 
Will be fine. It's only a small jump over the standard 35 profile tyres. As said, the Z4M has 45/40 profiles iirc.
 
Imaginationcreations said:
Am I rite in thinking though the 108 s are 8.5's and z4m's are 9's though?
Click to expand...

The 40 refers to the % profile of the width of the tyre not the wheel, so the wheel width has no effect on diameter.
The M was designed to use a different profile the non M wasn't and has an effect on gearing, ultimately by fitting larger diameter wheels is that you make the car slower
 
sars said:
Imaginationcreations said:
Am I rite in thinking though the 108 s are 8.5's and z4m's are 9's though?
Click to expand...

The 40 refers to the % profile of the width of the tyre not the wheel, so the wheel width has no effect on diameter.
The M was designed to use a different profile the non M wasn't and has an effect on gearing, ultimately by fitting larger diameter wheels is that you make the car slower
Click to expand...


had to have a bit of a think about that last statement :lol: as speed is an ambiguous term there.

acceleration will be less, speed at a given rpm will increase just it would require more power to achieve it due to inertia/resistance etc. given the power is the constant then yes it will be slower at the top end ..... or have i missed something?
 
RJS-Z4 said:
Are these not the standard size tyres on the //M wheel? If so, I'm running them on mine no issues, but my offset is further out than the 108's.
Click to expand...

Possibly, I thought the thread was for a 3.0? May have issues with insurance (unless notified) in the case of an off as they are not the standard fitment sizes.
 
domsz4 said:
sars said:
Imaginationcreations said:
Am I rite in thinking though the 108 s are 8.5's and z4m's are 9's though?
Click to expand...

The 40 refers to the % profile of the width of the tyre not the wheel, so the wheel width has no effect on diameter.
The M was designed to use a different profile the non M wasn't and has an effect on gearing, ultimately by fitting larger diameter wheels is that you make the car slower
Click to expand...


had to have a bit of a think about that last statement :lol: as speed is an ambiguous term there.

acceleration will be less, speed at a given rpm will increase just it would require more power to achieve it due to inertia/resistance etc. given the power is the constant then yes it will be slower at the top end ..... or have i missed something?
Click to expand...

Acceleration will be lower, top speed is a different matter as it's restricted to 155 mph, unrestricted, the restriction becomes the amount of power available. High gearing means that the engine will rev lower for the same speed but may not be in the right range for maximum power and will stall at a certain speed before max revs is reached. Conversely lower gearing means higher revs for the same speed but more power, restriction then becomes max revs.

You can see this conundrum in Formula 1, cars bouncing of the limiter or maxed out on power until slipstreaming
 
boristhebold said:
RJS-Z4 said:
Are these not the standard size tyres on the //M wheel? If so, I'm running them on mine no issues, but my offset is further out than the 108's.
Click to expand...

Possibly, I thought the thread was for a 3.0? May have issues with insurance (unless notified) in the case of an off as they are not the standard fitment sizes.
Click to expand...

I meant it as in I have that tyre size fitting on a set of \\M wheels on my 3.0...
 
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