Tire question RT615k+
 

New to HPDE days and autocross. Three track days in and another this Sunday. Autocross novice school in March. My intent had been to leave stock for the first season to see what was really needed. Brake pads and fluid have been upgraded CSG C1 pad and Motul 660. Huge improvement.

Now I feel like I want a bit more grip. Seems like the Falken RT615k+ is a good step before hitting to 200TW tires.

Narrowest tire they have for 18” wheels is 225. Fallen days it’ll work on a 7.5” wheel.

It’s only a .39” but any issues with this particular tire or running it on a stock wheel?

That will work just fine. There are probably better tires you could use in the range that the RT615K+ sits in but they are also the variations of the 200TW tire too.

Regardless, a 225 wide tire will fit on a 7.5" wheel just fine.

I ran a 225 on the stock 17" with no issues. While there are faster tires, the RT615k+ is my favorite tire for learning to lap, since it is grippy and fast enough to keep up with traffic, while having good wear characteristics and predictable behavior for learning the limit. They also have nice street driving characteristics, and since they are inexpensive, I use them as daily driver tires now.

The GT Radial SX2 is even better for learning and wear rate, but isn't as fast. But it might not come in a convenient 18" size.

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Do it, I can't find a better tire in that size/price bracket on Tirerack.

GT Radial is probably the best alternative.

If you're dailying them I'd consider Conti ECS or Michelin PS4S, more expensive but better all around tires then anything else and should stand up to a few days of abuse, might be quicker then the GT Radials, maybe not quicker then the old Falkens though. Both of those come in a 215/40/18 which would be a better fit for 18x7's.

You'll love the difference. I've had a few sets of RT615k+ and love them. Yes, there are faster tires. But if you think about it, you're saving almost a track day entry fee with the slightly less grippy tires. The seat time is worth more than the extra ultimate grip. Plus they last a lot longer than most of the other grippier tires.

Try the RS4 or RT615K as a stepping stone.

The 225 will be okay on a 7.5" wheel.

I was shopping the Falken at Tirerack in 225/45/17 and had the urge to check Costco. If you are a member, Costco is having a $150 off special on Michelins that brings the Pilot Super Sport 4S down to the same price as the Falken at Tirerack. I am likely to get them before my first track day on March 4.

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You used to be able to get the same deal on re71r, hopefully the upcoming potenza sport is good, might be a decent street/track beater as well.

Thank you all for the answers. Ordering the RT615k+. Hope to have it on just after novice autocross school in March.

Last “mod” until next fall. Now I’ll try to wear them out.

Just chiming in a 225/45/17 (or equivalent 225 width 18" tire) RT615k+ is going to be a good stepping stone. Not a full "top tier" 200TW like the RT660, so you can graduate to that once you learn a good line and all that.

Should be a solid tire. If your inclined GT radial had the replacement of the SX2s in the form of an RS tire. Only in 18s sizes. I am kinda curious how much more grip these have over the old sx2s

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Just a note reviving an old thread with a bit of info for others in the future...

I found out (the hard way) that not all GT Radial SX2s are created equal. The UTQG ratings vary by tire size, with some being rated 200 and others rated 260. I was a bit disappointed with the level of grip I was getting relative to my old PS4S tires and found little difference in lap time; I thought I was moving from a 300 tire to a 200 tire but in reality it was a move from 300 to 260.

Positives: they do wear well and are inexpensive, they are easy/predictable
Negatives: they are not a fast tire, they are heavy, and for at least the set I had there were some quality concerns... they did not seem to be balanced well and needed to be rotated on my wheels (rays te37s - a high quality wheel) to be balanced with reasonable weights. (First attempt would have required 7.5 ounces! Rotated 180 degrees required under 3).

It is an interesting time to buy tires; many popular choices are not currently available. (I wanted to get RS4s but they were/are sold out in my size, so I decided to try out the SX2s )