So it is worth the extra weight to get a bit more contact patch to go to 17x9 255/40 from 17x8 245/45? (and the worry they might rub).

Anyone here running 17x9 w 255/40?

Current set up. (No rubbing at all)
Wheels - 17x8 45offset - Enkei RPF1
Tire - 245/45/17 - ADVAN AD08R

Going to
Wheels - 17x9 40offset - Konig Hypergram (Only $188 each but 1.2lbs heavier than the Enkies)
Tire - 255/40/17 Toyo R888R

By my math the new set up will be in theory.... (This does not take into account the actual size difference of the brand of tire or the difference in tread width by mounting on wider rims).

Wheels (1" wider but offset going from 40 to 45)
+8mm inside
+18mm outside

Tires
+ 10mm wider
-5mm diameter (as 255/40 shorter than a 245/45)

And running Moton Club Sport suspension.

Or should I be "safe" and just go with 17x8.5 which would be only
+1mm inside
+11mm outside

Thoughts ?

 

I'm assuming this is for track use as opposed to autocross.

With a reasonable ride height (i.e. one that isn't so low as to be detrimental to suspension geometry), I haven't heard of anybody rubbing with 255/40-17 on 17x9 with reasonable offsets.

That said, 255/40 is probably not the ideal width on 17x9 for track use (it's fine for autocross because there's a different set of parameters involved). You might find better results with a 245 or even 235 tire.

 

Yes I don't do any auto X just track days. Why not wider at 255 ?

 

Going bigger past about 235 on this car isn't giving you particularly more usable grip while adding weight and the resulting negative effects. It's all downsides.
Also I would definitely avoid 255 if there's a chance you will be racing in rain.

 

I know you're running 17's but you might find it helpful.
I'm running a 255,35,18. DIREZZA ZII STAR SPEC. Wheel has offset of 38.
Don't do much racing in the rain but doesn't hydroplane on the highway doing 60-70.
With no rubbing accept for small spots on the plastic fender liner but you can't even hear it.
I wasn't able to tell a big differences in the weight per stocks but I'm sure it's there but the extra contact patch of grip vary use full but still allowing the car to slide out on you if you're going really fast.

 

My current Track setup are Gram light 57C6 17x9 ET38 nanestagger with 255/40/17 Nankang AR-1

 

What else have you tried?

 

So more info.

CAR - The car is track only (was built by prior owner for SCCA T3 spec so not street legal) so I obviously have to trailer it to events. The Moton Club Sports are not set super low. I don't race and don't do Auto X, just do open lapping days and HPDEs.

So I am thinking of going

WHEELS - 17x9 Enkie wheels (weigh under 16 lbs) so almost same weight as they 17x8 and oddly the 17x9s are cheaper than a 17x8.5. (I don't see how this is possible with 1" more of metal so maybe need to dig more on this. This is according to Good Win Racing Web site). I'll call them.

TIRES - Toyo R888R but what size?

235/45 (tread width 8.5" measured on a 17x8.5)
245/40 (tread width 8.8" on same rim)

both listed @ 24lbs each as I am guessing that the 245 is smaller in diameter. so why not get the 245/40 at the same weight?

Sounds like going wider 255/40 doesn't yield much, given the added weight (2lbs each more than the 245/40s)


So given all the above It feels like the 17x9 - 245/40 is the way to go? AGREE?





Here is my rig at Watkins Glen.

 

On my experience of R888R, I don't quite like it due to its soft side wall design ~
I think on some of testing I seen, not performed very well
Here are a video I find

 

The 17x9 wheel and tire deal is one of the most well documented subjects on here. Can’t believe you suckers fell for this like a catfish gobbling up a piece stinkbait.

 

Sorry I never post here and searhc didn't help me much. Do you happen to have a link to posts about the tire width topic ?

 

I have those wheels on my car and they are great, however you would be better off with 225 or 235 NT01 tire on 9" wheel. Discount tire direct has them on sale for ~$400 or $500 for a set.

Godwin also talks about effects of the wheel width:
Why not just 17x9 for 255/40 Tire? That's a 10 inch wide tire and maximized support of the sidewall results in much sharper turn-in response, more stable contact patch, more ultimate grip. On our typical west lot courses same 255/40 tire on 17x10 consistently more than a second advantage for same driver in same car over 255/40 on 17x9, and that advantage is closer to 2 full seconds per lap at tracks like Chuckwalla Valley Raceway and Streets of Willow Springs!

This thread goes into why:
https://www.rx8club.com/rx-8-racing-...estion-270121/

this was taken before car was lowered on coilovers:

 

if you're only doing open lap days and don't care about being competitive, why do you care about a few extra lbs or ultimate performance. i would run what ever setup that's most cost effective, if you're just out there to have fun.

i run hoosier 245/40/17 (measure close to 265mm) on rpf1 17x9 +35 (wheels are +45 but i run 10mm spacers) without rubbing issues. rear fenders are rolled but it's not necessary. i run this setup because we have limitation on section width for the rac class i run in.

also, not all tires measures the same, regardless what the stamp on the sidewall say.

 

You are right I don't really care so much about shaving off every extra 10th of a second. All I am trying to do it get the most grip per $$ and yes I do look at lap times, but just in my quest to get faster myself, not to "win" anything. That is why now I run an ADVAN AD08R (and will keep those as a wet set up) and will get Nitto NT01 or Toyo R888 and not Ho Hos.

Thanks to all for the help on this as I would have just assumed a 255/40 on a 9" would yield a larger contact patch and therefore offer more grip but sounds like that is not the case.

 

larger tires will handle heat better and last longer. but larger doesn't always equate to faster lap times.

i've not run any street tires on my rx8 but ive ran various 255 street tires on my Evo and they seem to fit best on 9.5" to 10" wheels, and have the best even wear on the tires. if you put wide tires on skinny wheels and pinch them, the outer edge of the tires will wear out quicker.

if you already have a dedicated set of rain tires, then maybe you should consider used racing scrub tires, like hoosier, BFG R1 or Toyo RR. you can find scrubs for cheap and probably better bang for buck than street tires. but if you're new to track and still learning the car, then stick with street tires.

 

I endurance race my RX8 and use the Falken 255's with success. They offer a decent amount of grip and are very wallet friendly. On avg about 4 sec slower than ho hos and a lot less expensive with no drop off in grip.

 

Wheels- 17x9 Enkei RPF1 is the winner. 17x9 (15.65 lbs) is actually LIGHTER than the 17x8 (16.05 lbs)

Tires - NItto NT01 - Still deciding but most likely a 235/40/17 @ 23.52 lbs - vs- 255/40 @ 26.62lbs (225/45 actually heavier @ 23.57 due to larger side wall)

I know weight is not everything, but really matters. And seems like the 235/40 have a wheel range of 8.0-9.5 so in the middle (higher end) of that range.

Here is there chart that shows all the dimensions (Including weight) for wheels and tires.

http://enkei.com/wp-content/uploads/.../RPF1-2019.pdf

https://www.nittotire.com/competitio...d-course-tire/

 

17x9 is basically the go to as discussed :-)
For a dedicated track car, why not try to fit 17x10?

I run 17x9. No rubbing issues.
Have been running 255/40/17 size tires and have run:
Direzza Z2 (a while back)
NT-01
Toyo RA-1
Toyo RR

NT-01 is a good choice to get started. Those tires are easy and fun to drive. Have loads of grip and last reasonably well for it. RA-1 are basically the same, but start with a little too much tread for the dry.

Next on my own list to try are the R888R, or more likely Yoko A052, since recent experience with RE-71r on a different car has me thinking those tires are actually softer than NT-01/RA-1.

I've considered 245/40/17, but I already bottom out in some turns with the 255 tires. I guess 235/45 would work. Or I could add more spacers on my bump stops to prevent this. Don't really want to go stiffer, and I'm not running super-low. My shock bodies are quite a bit shorter than oem though.

For rain, my experience has been that the softer the tires, the better off you are, up until you aqua plane, which what tread is for.
On a damp track with no significant puddles, slick RA-1, NT-01 or RR are all good*
With starting tread, NT-01 can displace a little water. RA-1 are pretty good full tread unless you get really heavy rain, at which point any reasonably quick tire is going to struggle and you're better off just waiting a bit for conditions to improve.

*Edit: I should add a slight caveat that if these tires are stone cold, they won't work all that well. You do need a little heat. So, in very cold conditions (which I haven't really experienced), or if you are not comfortable pushing in the wet (to build up some heat), then your experience may vary.