Our STI runs a 245/40-18 ST615K Plus and the fitment is pretty aggressive, the tire just clears the rolled fenders by about a 1/8″ or so in the rear.
In the front, the tire lightly makes contact with the wheel well liner on big bumps and when the wheel is turned at full lock. You literally could not go much bigger and not have serious contact issues. This is a very good fitment. If you are curious and have not been following this cars build series, the wheels are Advan TC III’s in 18×9.5 with a 45mm offset. This gives the tires a slight stretch.
Overall the car sits pretty nicely and is a good example of a GD STI. Our car still looks great after over 5 years of daily driving.
So far, our RT615K Pluses grip an order of magnitude better than the old 615’s with predictable at the limit traction with a smooth breakaway. We haven’t been able to get them to grease out although we haven’t got them to the track yet to where we could lean on them for long periods of time. From our drift experience, we think the grip will stay consistent and there will be no issues with chunking and blistering even at full tread depth.
One interesting thing to note is the 615K Pluses have a firmer ride than the 615’s which is odd because the only major change is supposedly the tread. It’s not a bad thing as the performance is much better all around. We would be curious to see how these tires would stack up in Street Class Time Attack competition. They might do decently but Falken does not market them to the track day crowd so they have not been very visible in the track day or competition scene.
The RT615K Plus is used by more than a few Optima Challange drivers with some success though which is a good indication that they should do well in Time Attack. At the very least the RT615K Plus will be a great HDPE/Track day tire that will stay consistently good until nearly at the point where the cords are showing. Stay tuned, we will run Project STI on the track soon and will update on how the tires are working.
Sources
Falken Tires
9 comments
I own this exact car and have been using your STi as inspiration in modifying my own.
I’m confused because in your previous article (https://motoiq.com/project-gd-subaru-sti-part-two-performance-suspension-wheels-and-tires/6), the wheel size is mentioned as 18×9.5 with a 45mm offset, tires are RT615 K, and fenders have not been rolled…
But in this article it says “Advan TC III’s in 18×9.5 with a 40mm offset” and the fenders have been rolled!?
You are right it’s 45mm, I made a mistake. I ended up running less negative camber in the rear and had to roll the fenders
typical with todays wanna be journalist/authors always publishing before proof reading. Everyone thinks they’re a journalist these days because they have a website.
And everyone who is slightly capable of writing thinks that they can be a literary critic too!
Mike any reason you went with 9.5″ wheels instead of 9.0″ to accomodate the 245 tires?
I liked the way it looked ! I also want to experiment with a slight strech on a modern tire. Old tires with more flexible sidewalls would sometimes respond well to a minor stretch. My feeling is that current tires do not.
Got it. On my Golf R I mounted 235 Michelin Cup 2 on Volk ZE40 8.5″ rims althoght 9″ rims were available but I didn’t want the extra width for extra rotational mass.
Anyway, thanks for clarifying that.
that’s probably perfect.
Where is the Falken track test follow up?