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Call Mania - they might also have something.

i've been doing some reading about excessive wheel sizes and some people beleive that something as wide as 8\" can do more bad than good.

im sitting on the fence at the moment on the issue though... what do other people thing.

original reading from here..

http://www.miataturbo.net/forums/showthread.php?t=3513

sorry but you might have to register and login to read it

it was all about selling these to put on wider wheels

So many magazines have said that you should keep close to standard wheels on older cars - I tend to agree - unless you hve a BIG turbo, you'll lose lots of handling - probably for little more grip.

I like that sidewise thing though.

greggtr wrote:reason for the added width... I have too much power for the 215wide semi slicks...

Are you sure wider tyres will help? You'll get better cornering traction (though not necessarily better cornering) but possibly worse straight-line traction.

Wider tyres don't provide a larger tyre contact patch, they just change the shape.

greggtr wrote:The 215/45/17 has a diameter of 626mm while the 245/40/17 has 625mm (almost no difference) BUT 215 has 220mm contact patch while the 245 has 245mm thus 14%more contact area per tyre and less tyre flex as the profile is lower... the way I read it is the wider the better (within reason)

I won't doubt that you could use more width for more cornering grip., but two things I note above:

1) contact patch area is not directly proportional to tread width. As the width increases, the length of the contact patch decreases! (The area doesn't stay constant but it's a rough approximation)

2) The profile of two tyres with the same rolling diameter on the same sized rim would be identical! (215*0.45 = 97mm, 245*0.4 = 98mm...). So flex should be similar (assuming carcass construction is similar - a big assumption though).

You can get a 17x9 from GMAX but you will have to flare your rear guards. Another option is to go to a softer compound tyre for more grip which sadly will last less time. What semi's are you using? Also, if it's a circuit car, it sounds like it's time to get some slicks......

greggtr wrote:... have a look at drag racers, lambo, porsche, ferarri etc... all high horse power cars with 300mm+ rear tyres.

Lambo, porsche's, etc. have wide tyres partly for cosmetic reasons (would you buy a Ferrari with 5.5" wide wheels? ), but mainly because they don't just go in a straight line. Drag cars use wider tyres to limit tyre deformation under heavy acceleration (because the contact patch becomes shorter, as Matty pointed out).

As for your personal experience with wider, low profile tyres ... is it possible that they were simply better tyres? Wide, low profile tyres tend to be targetted toward a more performance oriented market so there may be other factors involved (like better rubber, etc.).

Also, don't mix the tyre profile with the width. You can get lower profile tyres without changing the width, and vice versa (by changing rims). A lower profile tyre may provide better performance due to less flex (as you said), but then a higher profile tyre with better sidewall contruction may do the same thing.

Aren't tyres fun?

I'm not saying "don't do it" (hey, it's your money), just don't expect to solve overpower traction problems by simply adding wider tyres.

i think my brain just melted

can Mr_Q dummy that up a bit more...

are you saying that basically the wieght of the car can only distort the rubber so much ie make a foot print of a certain area and changing the width will just cause this distortion to be speard over a wider area hence making that area be spread thinly??

or am i looking at things from a whole new far out way

ha

tyres are probably the most important part of getting a car to go well yet i know soo soo little

irwin83r wrote:are you saying that basically the wieght of the car can only distort the rubber so much ie make a foot print of a certain area and changing the width will just cause this distortion to be speard over a wider area hence making that area be spread thinly??

or am i looking at things from a whole new far out way

ha

you got it

StanTheMan wrote:

irwin83r wrote:are you saying that basically the wieght of the car can only distort the rubber so much ie make a foot print of a certain area and changing the width will just cause this distortion to be speard over a wider area hence making that area be spread thinly??

or am i looking at things from a whole new far out way

ha

you got it

sweet