usctrojanGT3

Since I have 335/30/18 shaved RA1s from Trakcar, I was wondering if I can pair them up with the 275/35/18 RA1s up front? The front wheels on my car are 9 inches wide. I think that RA1s run a bit narrow (versus NT01s which run a bit wide). Anyone here ever run 275 wide tires up front?

tcsracing1

265 up front will work.

275 would require offset wheels and fenders I believe. ABS becomes an issue too...

ShakeNBake

I can fit BFG R1 265/18 on the front, but only because of the reduced diameter. They rub a tiny bit at lock, and on the strut spring. I'm running -3.5degrees of camber. The 265 R1 is the same section width as the 255 R6, but the tire has a squared off face/sidewall compared to the much more rounded R6. I could not see going any wider without a real cup fender.

Steve W

275 RA1s on 9s will fit no problem. I have that setup with 305 rears on one of my wheel set for years. The tires actually measures about a 270 when mounted on 9s. The setup is fantastic.

There are tricks that can be done on the front to get tire clearance. You need at least 2.2-2.5* negative camber on the front for these tires, so you rotate the strut tops which give you further inboard clearance. Some SCCA Pro Solo, guys are fitting 275 wide A6s on the fronts, which are another cm wider than the 275 RA1s. Strut tops are rotated and brought inward as much as possible, while using the control arm shims to set the camber range. You can then do a slight massage pull on the fender arch to pull out the fender another 7mm or so, giving you just enough clearance to clear the spring coils and fender lip by a mm or two.

usctrojanGT3

No issues with ABS and/or nannies?

Steve W

I run them with the 305/35/18s so that maintains the 0.5 to 0.75" front rear diameter differential the car was designed with. Same thing with the A6s. At the track or an autocross, no one I know including myself runs with TC on. I think once you shut them that down, it's not a problem, or so I hear when front and rear diameters are the same.

usctrojanGT3

Is it me or do the RA1 run a bit narrower than other tires that are the same width? I had the 305/35/18 NT01s next to the 335/30/18 RA1s and the RA1s didn't look like an inch wider.

usctrojanGT3

Do you run the regular ones or the "S" series of BFG R1s?

ShakeNBake

Regular. I've been meaning to try the S. I suspect that the S model will be more prone to heat cycling out, but willing to try. The sizes/specs seem to be identical.

usctrojanGT3

How do the BFG R1s compare to Hoosier R6s? How many heat cycles are they good for? After how many do they cord?

Nick Wong

I have 265 width on the front. RS fenders and lip extensions, Champion wheels/offsets. The tires come close to rubbing both on the inboard (Ohlins Cup shocks/springs) and come close to the fender at the top. I wouldn't run anything bigger without the Cup fenders but that is big difference in price and fitment (OE fit vs race car fit). With Cup fenders I think you could run a 295 up front, but at the expense of scrub radius, which ultimately makes it a net zero gain in performance, unless you go with longer control arms and move the upright out- again, race car parts, not ideal for a street car.

ShakeNBake

- They are at least 1-2 seconds off pace of R6s at COTA
- Less slip angle before they really get mad
- Seem to last 5-10 more heat cycles
- much more gradual heat-cycle grip rolloff.
- Worse in the cold and wet than R6s.
- R6s seem to grip out of the gate, R1s need to come up to temp.
- The rubber seems to be more durable, I have yet to cord a rear before they heat cycle out. With an R6, it depends how frisky I felt that weekend.
- R1s are also much heavier than R6s, on the order of 2-4lbs per tire.
- And like R6s, R1s will rotate on the rim
- My net is that they are not quite as fast or fun, but cheaper and a better value due to greater life (I would not race on them, but a good DE tire if you need the sizes)