Looking to get some inexpensive tires for track days on my OEM rims. I am thinking about going with the Falken RT615's but they do not come in the sizes I want. What size RT615's are you guys running on your 18x8.0 and 8.5 wheels? I am looking on http://www.vulcantire.com and they do not have 275/40/18 for the rears - they only have 275/35/18. Should I go with 265-35-18 on the front and 275-35 on the rear? 255-40-18 on the front is out of the question since it is taller than the 275-35. Is 265 too wide for an 8" wheel?

VDC/TCS is not an issue since these tires will only be on the car to and from the track.

 

I ran the 245/265 RT-615's on the track wheels. I wouldn't go with the widest tire possible as you will have to much squirm. Check the website and this is probably the max you want to go on these wheels.

 

Hmmm... 245-40-18 in front would be nearly half an inch taller than the 265-35-18 in back. I might just go with the Kuhmo MX. Same price, more sizing options.

 

245/40 front and 255/40 rear works great.

 

VDC is always an issue on track days.....just remove the Yaw sensor to fix it.

 

You might want to check out going square all around. It will help the push issues with offset tires and will allow tire rotation at an event for better wear and heat management.

 

He can't . . . he has stock rims with staggered sizes -- 8" in front & 8.5" in rear. He can still go with a square setup if he wishes but will not be able to rotate the tires (unless he wants to dismount them to rotate which will be cost prohibitive).

OP - I'm also in the same situation wanting to use my stock '06 rims for a new set of tires. I've looked at the RT-615s and am strongly considering a 245/40 F & 275/35 R setup. According to the Falken tire chart, they're the same diameter at 25.6" tall.

http://www.falkentire.com/rt615_sizes.html

 

whoops, missed that.

 

I hear you on RT615 size choices, why can't we have more choices,...agh!

The 265/35-18 and 275/35-18 setup would be the best. However, the 265/35 would be extreamly difficult to get onto a 8" wide rim because of the very short sidewall height. We have seen 285/35-18 installed on a 8" rim, though it was advised that you had better be VERY nice to your tire guy cause he wasn't going to be happy when he was done.

The 265/35 - 275/35 setup would yield tread widths front and rear that are 10" wide and give you a .2" rear height bias.

255/40-18 at all four would next with a 9.4" thread width front and rear, no height stagger of course, but the .2" you have above isn't much anyhow.

I am currently running the RT615 and have run the MX, KD and RE-01R. I do not recommend the MX.

 

Thanks for all the help guys. I think I am going to go with 245-40-18 front and 255-40-18 RT615's in the rear so it gets along nicely with VDC. Also these are quite a bit cheaper than the wider sizes and they run wide anyways.

 

What sizes are you running? Also, are these mounted on stock rims? How does the RT-615 compare to the RE-01R?

 

245/40-18 and 255/40-18, though I will be switching back to 255/40 fronts. I am not on oem rims. I have very limited clearance in the front fenders vs what Z and G coupe owners have, or else I would run more thread width overall.

On the RT-615 vs RE-01R question, here's what I had to say in a recent thread that asked the same question.

 

^^-- +1. they need to start offering wider sizes for 17/18 inch wheels :/

 

That tire set up is just fine. I ran a 265/35/18 up front on a 9.5" and 295/30/18 on the rear 10.5" and it stuck well. I have driven Z's with the 245/40/18 on 8" and 265/35/18 on 8.5" and they handled just fine. As a matter of fact, they 245/265 set up allows the car to spin up a bit quicker and forced a more smooth turn in, which actually brought times down. The car didn't bind up as much either. Bigger is not always better.

 

I'd run the 265s at all 4 corners. I like the feel of of them in 275s at all 4 corners, but if they had larger sizes, I'd be all over it.

 

275 all around would be what I would do, the stagger rim size really isn't a big deal.

if anyhting do 265/35f and 275/35r

 

Widest is not always better. I have run the RT-615's for as long as I have had my car and on different rims. I have found that with that tire, the Z likes is best with a 255/40/18 front and a 275/35/18 rear. I have run bigger and can tell you the squirm and sacrifice in spin up was not worth what the cost and I saw no real turn speed benefit.

By the way, the tire is amazing for the price and I HIGHLY recommend it.

 

RT615's run wide, so 265's on an 8 inch wheel is out of the question as my car sees track duty and I don't want any squirm. 255 would be the widest I would run on the front stock rims. And they are a heck of a lot cheaper in that size.

btw, got my 245/40 and 255/40 on last week and they look PERFECT.

 

I just got my (4) 18x8.5 track wheels with 255/40 RT615's all around. Seems like I the side wall is a bit too straight so I might go 265/40's next.

These are on (4) 18x8.5 Rays Track Wheels