From what Tire Rack is telling me they haven't made 255/40/17s yet period. I may just get 245/40s not much difference in width. Height is short but I'm more set up for acceleration and response than top speed anyhow.

 

They have definitely made them....Like 4 evo's in Vegas are running them, Kaj has them, and a few other guys I think too.

 

^+1 There were numerous folks I raced with last season that I know for a fact had 255/40-17's.

FWIW I'd rather run a 255/40 Rival S vs a 245/40 Re71...

 

Perhaps that came out wrong. I didn't mean ever just since the whole back order thing started.

 

Oh, gotcha

 

285's came in this week

 

Ooooo TC105N's

 

they are too sexy

 

Love those wheels. I decided to screw myself and run ventus TDs while I wait for production to resume.

 

Couldn't wait for the 255/40/17's so stuck with 245/40/17. Should be here on Wednesday. Excited to finally autocross on some sticky tires.

 

285/30 is not too short for an X. You gain about 100 rpms in spool from the decreased diameter and lose about 2mph at around 60mph. So you get slightly better acceleration and slightly less top speed than a stock diameter tire (245/40 or 275/35).

I run 285/30's on a 10" wheel. They will fit fine on a 9.5".

I suggest bumping your rev limiter up to 8,000rpm to allow for higher revs due to shorter gearing.

 

Spool slows with shorter effective gearing. Think about 2nd gear vs 3rd gear, which spools faster. Same thing happens when changing gear ratio. Also, 24.9" tire to a 25.3" tire is a pretty small change in MPH difference, only 1mph at 60 by the numbers (not by guessing...).


Torque increase and speed decrease is 1.5%, or about 5ftlbs at 300ftlbs total. You'd probably gain a bit more accel also bringing the weight in (Reducing MOI) but I haven't bothered looking at those numbers.

 

You're right, spool might not have been the best term. The shorter tire does give slightly better acceleration and torque as you stated.

To be clear, the stock tire size is 25.7" (245/40), so the 285/30 is .8" shorter. That is about a 2mph difference at 60mph.

So if you have autox events where you already need to shift to 3rd, then the 285/30 might not be the best tire for you. If you never feel like you need to shift to 3rd, then this should work well. In fact, it might even benefit you more.

 

I guess I'm lucky I bought mine when I did. Dang.


How does everyone like them? I've only done one AX event, but it was in the rain. I've done one track day, but the course started completely wet, then was damp with mud, here and there.
I actually did ONE AX event in the dry, but the tires were green and I'm told they get much faster.
As of right now, I'm not seeing a reason not to go back to the R-S3.. but I keep being told to be patient because these tires will come alive.

 

Once you do a real track day, you won't like how the performance falls off after 1-2 laps once the tire gets hot..