17" Vs 18" Wheels For Motorsport

[BOZ22N]

Hi all,

I am selecting some new wheels for my R33. I am looking to change my car back to a more factory spec to be eligible for more Tarmac rally events.

One of the things I am going to change is the wheel size. If I stick to the 2" high and 2" wide increase rule I can go to 18 x 8.5 but the question is do I need to?

I am current ally running stock R33 brembos and am happy to keep using them so I can get away with a 17" rim.

17" PROS

I have weighed both options with a AO50 245 tyre and the 17" is lighter by 1.4kg per corner.

The 17" tyre is $70.00 cheaper per corner

18" PROS

Rolling diameter is 26mm bigger which would help me stay with the current diff ratio.

Might be able to pick up cheap second hand tyres for track days etc.

better brake cooling.

Saying all the above you all might have some more info for me to help

[BOZ22N]

Lol massive fail.

I dropped my phone and it sent the post before I was finished.

Fat hands and iPhone do not work.

Anyway as I was saying if you have any advice for me that would be great .

Things I don't know are reliability, handling and geometry changes.

Thanks for reading both my posts lol.

[Dale FZ1]

Geometry changes? That's going to be dealt with in your suspension setup, not related to wheel diameter.

Price and availability of the sizes you want are probably the biggest deciding factors - if you can't readily get them, or they are ridiculously priced then you'd be looking elsewhere. Competing to win, vs entering to have a run are also far different things that means you might just have to deal with the price difference.

Assuming you're looking only at the Yoko A050, 245 section width. Are there different nominal aspect ratios, or tyre heights for a given rim diameter?

Big call to make any definitive statement about durability/reliability of the tyre based on its rim diameter, although a taller tyre is going to have more rubber to play with for a given distance travelled. I'd think the manufacturer would vary carcass construction and rubber compound for the different sizes and rated load capacity. There might be some merit in targeting specific tyre sizes because the sidewall height (or aspect ratio) is going to impact general stiffness/compliance levels and tyre response. Formula 1 vs other open wheel categories highlights this, in my mind at least.

Definitely a mind bender, there's probably going to be a bit of trial and error in finding what you prefer.

[BOZ22N]

Thanks Dale all good points.

I was more thinking car geometry ie cog and rc than suspension. I don't know if this is correct but if I was to use the 18 the car would sit about 13 mm higher with the same suspension settings. Obviously this can be changed but just trying to limit the variables and just evaluate the tyre and rim combo on their own merits.

Thanks again and you are rite it might come do to it is just more cost effective to run 17's.

[sav man]

18" tyres wear better than 17" tyres on a rally. The only geometry changes will be what ride height your car sits at, You need to make sure the suspension can use full compression without fouling on anything.

There is a few R33 GT-R's running round with 18"'s on, so doubt there will be any problems, it's just going to come down to $$

[BOZ22N]

Thanks Ben

[Neil]

Lol massive fail.

I dropped my phone and it sent the post before I was finished.

Fat hands and iPhone do not work.

Thanks for reading both my posts lol.

My advice would be to buy a real phone,,,not that shitty iphone crappy thing and these problems wouldn't happen.

Cheers

Neil.

[BOZ22N]

Haha thanks Neil

[evil_weevil]

my advice sell r33 and buy my mx5...wait...

[BOZ22N]

Lol you are a funny man

[AMR33]

there's probably going to be a bit of trial and error in finding what you prefer.

I think this is what it will come down to. I was debating the same thing a few months back and went with 17s. I don't think I'll go 18s.