I'm concerned that as we add width we're adding diameter/height, which wouldn't be good for us (The STI's probably could handle it though). The little bit of extra width a 255 would allow could very well be wasted on us (I've seen similar scenarios happen in STX, on the WRX and the RX8). Moving past 255's gets us into 18" wheel territory.. extra un-sprung and rotational weight, height... 35 series sidewalls, the whole works. We really should aim for 285's, (which won't fit EVO 8/9s, so 275s?), according to TireRack they'd be 0.9"-1.2" taller in diameter, btw,

 

how about a one differential allowance? i don't know that it could make up time, but it is something to look at as well. i keep harping on this and yes we do have 3 diffs, but being able to modify one (rear in our case) is also something to consider, no doubt the other 2wd cars are running OSGs or the like

 

you know there's no regulations on sidewall height, right??

 

Having been on the losing end of a protest before. I also don't think it's fair to bring it up after competition runs are over. If you think someone's car is illegal. Then you should bring it up before runs. And at the very least, after day one competition is complete.

Anyway, I questioned in my mind his motives for running such a setup. As the increased rear track width would add a lot of understeer. But I didn't talk to him personally about his setup. So maybe it is faster. But his times were certainly impressive.

 

He's talking about the performance differences, not regulations

 

Honestly, I think this should fall a bit lower on the list of suggestions. We're already in okay shape with the ability to restack the rear diff and play games with the fluid. Does an OSG or similar fancy differential actually make that much of a difference?

Also, I'm hesitant to add another $1K+ item to the list of must-haves for the class.

I think we stand a lot better chance of getting an incremental change (more tire) than making such a large rules change that incurs a lot of expense.

Although I've heard a lot of lofty claims about ACD reprogramming improving performance. Is that really as magical as some people make it out to be? I could get behind that rule change, but unfortunately I don't think it would help the STI guys out much so it's still not ideal. But then again, I'm not up to speed on the STI world any more.

 

Thanks for the input. The rear diffs do make a huge difference, as does the ACD reprogramming. I would venture 1s difference for the rear diff per 60s on an autox course if used to the full potential for our cars, maybe more than that for the 2wd cars, especially those that came with something like a viscous. I agree with you as far as adding parts to the list of must-haves. Just seemed to level the playing field as far as mods go, but maybe requesting wider tires is the way to do it.

 

and so why would there be a decrease in performance when you can just choose a smaller sidewall?

 

overall height/diameter increase (wheel/tire combo)

 

You don't have to increase overall OID if you increase the width of the tire. You just select lower profile and you are good to go! No OID change, no side wall height change, just wider!

 

here's the landing page for one popular street tire, check the specs tab/overall diameters
http://www.tirerack.com/tires/tires....28Version+2%29

 

C'mon man...OID for 245/40/17 is 24.7" and if you go to 255/40/17 or 255/35/18 you can get 25" OID, which at the end is 0.15" height increase. That is hard to be felt by anyone out there!
At the same time you could go to 285/30/18 from another company and get 24.8" OID.

 

255's is a non-starter for me imho; if they gave us the same tire restrictions as 2WD my real-world scenario would likely have me running 275/35/18 Hankooks (25.6" dia), 0.9" more diameter and 0.45" taller.

 

I hear you there! Let's hope tire manufacturer will be bringing more sizes, so it will be easier to choose the right size. Luckily, X doesn't have issue with that!

 

If I remember correctly the 255/40/17 tires are slightly smaller diameter as the stock 235/45/17 EVO8/9 (I'm not talking about the EVO X).

235 sidewall = 105.75 mm
255 sidewall = 102 mm
245/45 sidewall = 110.25 mm
245/40 sidewall = 98 mm

While it is bigger than 245/40/17 sidewall, it is smaller than the 245/45/17 sidewall. You get 10mm more per tire which will help lateral grip and the setup is still smaller than stock diameter. What little you may give up in acceleration you will more than make up for in grip, still a win in my book. Plus the speedo is going to be more accurate than any other combo.