What tire on 18in rims?
 

I'm going to 18x8.5 in the front and 18x9.5 in the rear. What is the proper tire size to match up with the stock tire diameter and the regular width for the front and the rear?

Would you go taller or wider than that? Why? How would that affect performance? I still want to have the option of dropping the car an inch or so in the future.

I would reccommend 235/40 and 275/35. These will be the closest unless you run a 225/40 and 285/30, but this would creat mad understeer.

The greater the deviation between the front and rear widths, rear being the greater number, the greater the understeering characteristics.

Hence, max runs his CCW 10" all around with 285/30 front and rear, for the track. That's a great setup because that tire will be almost dead on with the O.E. 225/50/16. I'm talking like a tenth of an inch. It is dead on. I wanna go for a ride!!!!

But for the street, I love the staggered look and that's what everyone does. I'm not sure what the threshold is for the FD as far as front to rear tire size relationship. The 8.5 and 9.5 might be a great setup without any rubbing problems, ask MAXCOOPER. He's been around the block and from meeting him is a very humble person and glad too help.

LATERS, Rishie

Rishie,

So can you source any brand-name wheels that can accept 285/30-18 on all corners for the FD? I am apprehensive to go w/ CCW since they look like my street wheels already.

Thanks Rishie, you're too kind. ;)

I think the sizes Rishie quoted sound good. If it was my car, I would get 235/40-18 and 275/35-18. That is still a little larger diameter than stock (which can lead to rubbing in front), but it is not a big change and seems like your best choice. It is great to have wide tires, but I don't think I would want more a F/R difference than that, unless you have mega power and don't care about handling.

There is a cool little calculator applet here:
http://208.29.168.220/garage/tirecalc.html

Also, consult the Spec sheets of the tires you are considering on the Tire Rack. They show the diameter and recommended rim widths for each size. The diameters and rim width recommendations vary slightly between different tires, and this should be considered the authoritative source of info for a particular tire.

-Max

HEDGE,

I can research into what other wheels are offered in the same offset as MAX's CCW's, providing he would be ever so kind to somehow find out what offset they produced for him.

Then I can match up the offsets and get other customs produced, or see what else I can find that is mass produced, relatively speaking of course.

I can get you custom made WORK wheels as well, but it is limited to certain unassembled styles that are available in the local wherehouse.

But yes, there are potentially a lot of options providing the offset isn't some crazy weird shit.

Thanks, Rishie

The backspacing is exactly 7.5". That works with 18"s, but apparently you need 7.375" of backspacing for 17" in the rear. This assumes you have 2.5" coil-overs installed. I don't think 10" wheels will fit in front with stock-sized springs.

I think that translates to an offset of 46-50mm, considering that the real width of the rim is 11-1/8" to 11-1/4". I looked for a while and could not find anything other than custom wheels for this offset. CCWs were by far the best value.

-Max

Does going larger in diameter in stock make much of a difference? Would the speedometer and odometer be off? I like the sound of the setup you proposed rishie but I don't want negative consequences such as recalibrating the speedometer.

Max: Thx again for the info! Very much appreciated. BTW, was it difficult to fab the RX6 pipe connecting to the M2 SMIC? I'm prolly getting the same kit but will need the pipe for a CWR SMIC.


Rishie: So, are there anything from Racing Hart, Desmond, or Volk that will work w/ the above? Based on Max's measurements, I gather that he calculated the offset as follows:

((11.125/2) - (7.5)) * 25.4 = 49.2125mm offset

((11.250/2) - (7.5)) * 25.4 = 47.625mm offset


Thx..

duckyjp: Larger diameter tires increase the chance of rubbing in front and increase the inertia of the wheel/tire assembly which slows acceleration. However, other than 285/30-18s I think you have no choice but to go a little larger than stock, and the sizes that Rishie recommended are quite reasonable. Pretty much everyone who gets "bigger" tires also has to get a slightly larger diameter tire. Also, that tire size calculator applet that I posted the link for will tell you the speedometer error at the bottom. A few percent is not that big of a deal -- 1% = 1 MPH at 100 MPH.

HedgeHog: I cut some length off my original IC pipe, which was pretty easy. I am actually going to try to reconfigure it this weekend so that I have one less 90 degree bend. If my reconfiguration works, you'll probably be able to fab your pipe by simply cutting the pipe you got with the IC originally.

Your calcs for offset look good, too. It is probably a 48 or 49mm offset. Remember, though, that that only works in back with 18" wheels. For 17" you need 7.375" backspacing, or perhaps you can get some aftermarket trailing links as it is the trailing link that will contact the wheel first.

I'm going with 245/35/18s Pirelli P Zero Dir on the front (which works out to VERY close to stock diameter, and 285/30/18s P Zero Assim on the rear - for my street wheels.

Pirelli has those front sizes in thier P Zeros, both Assemitricals and teh Directionals.

245/35/18s are also available from Toyo, in thier T1 line.

If you like Michelin Pilots, they have them available in 235/35/18s (as do the Pirelli PZero Assim).

For those on a budget, Falken has 245/35/18 and 265/35/18s, which sizes well for front and rear. I had them on my Civic (the brand/model, not size hehe), and they are good for the price.

None of the sizes mentioned by the others will effect the speedo reading in any significant way, so no worries.

Oh, and if you really want insane, Pirelli has 255/30/18s that you can use on the front, but only with 9"-10" width wheels. Talk about rubber bands, hehe.

A common combination I've seen used is 245/35/18 and 275/35/18. Any comments? Shiv (of SCC glory) used this with Hoosiers on 18" Forgelines. The front matches perfectly with the stock size on Toyo T1-S's, and the rear plus sized a bit.