255 35 19 on the front ???

S

step_change

Active member
 Planet Earth
Hi all,
Would an M437 with this tyre work on my [stock] 35is ? Would it rub? If so how serious would that rubbing be? All used M437 seem to have these on the front....
Thanks
 
I'm assuming genuine 437M alloys?
Stock suspension? Will have to check my pictures but I think I got away with 235 fronts with MP4S lowered on eibach on 437M m with slight rub on full lock (rolling fenders resolved this)

If your running 255 on the front, what are you planning to run on the back?
 
step_change said:
Hi all,
Would an M437 with this tyre work on my [stock] 35is ? Would it rub? If so how serious would that rubbing be? All used M437 seem to have these on the front....
Thanks
Click to expand...
Any rubbing is serious...

When fitting wider tyres remember that OEM fit is a balance between wet and dry grip. As you increase the tyre contact area you reduce the amount downforce on the tread, especially important to 'push' the tread down through the water film, maintaining wet grip.

As an apprentice mechanic I remember watching a safety video on ths topic, about all I do remember though lol...
 
The whole car is stock - i.e. what the car was built with. Yes genuine M437 wheels.
All the M437 wheel sets that I see seem to see on the bay have 255 on the front and 275 on the rear - which implies they came off of a M4.

Trying to determine which size to buy.
 
... maybe I don't fully understand this.... Is the wheel rim the same regardless and I should just change the tyre on the front from that 255 to a 235/35/19?

Thanks for your help.,
 
mcbutler said:
When fitting wider tyres remember that OEM fit is a balance between wet and dry grip. As you increase the tyre contact area you reduce the amount downforce on the tread, especially important to 'push' the tread down through the water film, maintaining wet grip.
Click to expand...

That isn't quite how it works. The weight on each tire is constant, regardless of anything else. Its based on the weight of your car (so far I'm not disagreeing with you, obviously). The area of the contact patch is SOLEY based on the weight on the wheel and the pressure (pounds divided by pounds / square inch = square inches). This also means that the pressure on the ground is the same regardless of tire size. Newtons second third of motion: "For every action..." tells us that if the tire isn't accelerating upwards then the pressure inside is equal to the pressure outside.

Therefore, fitting a wider tire (assuming you keep inflation pressure the same) doesn't modify contact area, or pressure, it changes the geometry of the contact patch. It will make it wider and "shorter" front-to-back.

So that being said I don't know what the impact would be on wet performance. Its possible that by making the contact patch wider that you are increasing the volume of water that needs to be channeled out of the way when running in wet conditions, which I assume would still have the same end result of poorer wet performance, albeit for different reasons than you think.
 
I currently have those wheels and tyres on my car. I have stock adaptive suspension so should be identical in ride height to your car.

I had slight rub on the fronts but only when reversing and turning the wheel towards full lock. It was rubbing the centre of the wheel arch on the edge of the tyres so I used a heat gun to reshape it a little, only needed a few mm to clear the tyres.

I think 245/35 would be ideal if you have the choice.

The rears are absolutely fine, no rub at all. I really appreciate the extra grip from going wider. Performance in the wet is great but that's more to do with the PS4S being a good wet tyre than any changes in width.
 
I may buy a set of 437m with 275/35/19 rear and 255/35/19 front and change the front tires to 245 and flog the 255s and my existing set of 326’s.

Does that sound sensible chaps?
 
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