CrispyRX7

iTrader: (139)

BTW Vert rims are 15"x6.5" not 15"x7.5" Regardless of the rim width fitting a 225/15/50 isn't a problem for these wheels.

This is what I use on my FC racecar. vert rims with Toyo RA1's. And they weigh next to nothing.
Crispy

SPiN Racing

Correct.. but I mentioned that... two different sizes of rim... and two different tire sizes. Also if I am not mistaken there may be a circumfrence difference also.
BUT... Yes a heavy tire will cause MOI issues as well.

Then again... I have some 18x10s here at the house for the 10 Annie.. and DAYUM they weigh a TON. I would have to get the dimentions off them.. but that is irrelevant.... they ARE cheap rims.. not high dollar forged etc... and the tires are I believe S02s.. BUT... they weigh something like 52lbs in the rear complete.
When I get out in the garage tonight (If I get a chance) I will measure them and enter the sizes.

As we both said.. there are MANY issues to worry about.
Profile, contact patch, looks (for some), total weight, rim design, tire design.. etc etc..

Soo again.. prioritise what you want and go from there..

M's

to limit the size of the brakes, hense the carbon ceramic brakes now a days.

Additionally the tire sidewall is a spring. You change your spring rate based on the pressure of the tire and the profile of the tire. There's no reason to go to bigger wheels, it will increase braking distance among other things. you want the wheight as close to the center as possible.

M104-AMG

iTrader: (8)

Don't forget to factor in that with larger wheels, the spinning torque of the wheel is greater is greater, thus your brakes have to work harder to stop the vehicle.

Stay with 17-inch wheels. You want to go faster, brake deeper, and get STICKY tires.

Hoosier has a good assortment of real race rubber in 17-inches.

:-) neil

SleepR1

17s

Carl Byck

I cannot believe that with all the "experts" on here(some really are), that nobody asked what size wheels you currently own. If the 17s are 9.5 or wider, stay with them, and run 275-40-17s, if they are narrower, you will want wider wheels regardless of whether you end up with 17s, or 18s. If you look at what the top AX competitors are using in ASP, or SM2, I think you will see alot more 285-30-18s than 275-40-17s. Quite a few street prepared national champions rolled on the 285. That said, are you in it to win a particular class, or just go fast? will you just AX, or will you be doing some HPDEs? I think the 18 with the 285-30-18 is the best option assuming you are replacing your wheels, but as I said, if the 17s you have are 9.5 or 10" then stick with those for now. If you go 18s, there are also quite a few slicks that can be purchased as take-offs for ~75.00 each, these are alot of fun both AX, and at HPDEs. Fritz has some 18x10/18x9.5CCWs for like 1500.00 in the for sale section, buy those, and run the 9.5s in the back, and the 10s in the front(flame away, I am ready) with the 285s. I'm just an Old School FC guy running 16x12s with 13" slicks . Carl

Silkworm

No, you're a wannabe old school FC guy who WANTS to run 16x12s.

Until you drag that thing out to the track, that is

Blew the motor last month, so if you're heading up for the race this weekend, good luck.

PaulC

Carl Byck

You are correct, I am on jackstands, not asphalt

Silkworm

How much to go? You going to make it out in January?

Carl Byck

I am installing the Fuel cell, surge tank,and balance of the fuel system next week(replacing a system that was running out of fuel@~400hp). A project like this is never done, but it coulsd see the track anytime after that. my plan however is to keep on fortifying every system in the car for another couple months. I am trying to build a very high output car(in road racing circles) that will not break...(very often)

ALPSTA

iTrader: (3)

I'm curious with all the mumbo jumbo been talked here, how come cars like m3 csl or 911s come with 19inch wheels (mind you these cars are more performance and track focused than what rx7 used to be)? Do technology improve at such a pace that 19inchers are the 17inchers of the nineties?

Another thing to think about is (even though irrelevant/sorry for the hijack) when aftermarket coilovers are so popular, how come cars like sti, evo8, m3 csl, 911 etc. are manufactured without them? I'm sure it's not because of cost cutting reasons.

SleepR1

One word "style". There was a time when brake calipers and rotors required bigger diameter wheels. I've peeked @ M3s with 19s, and there's plenty of space between the wheel and brake caliper. The factory tunes the suspension system to work for public road driving; compromises must be made for road cars. Enthusiasts tailor their suspensions for their needs, and the ability to adjust ride height, spring rate, compression/rebound are plusses--especially if the enthusiast is a serious road racer/autocrosser.

Carl Byck

As an aside, I test fitted a 16" rim on my Supra TT the other day. The 13" brakes easily clear. You just need to account for caliper heighth. I only mention this since so many hard core RX7 race cars ride on 15" tires (EP). Carl

the_glass_man

iTrader: (2)

So 18X10 42mm offset all four corners with 285/30/18's or 17X9.5 42mm offset at all four corners with 275/40/17's?

maxpesce

EP cars (fb's & miatas at least) are limited by the rules to 15x10 maximum rim size - fb's also have to run stock oem brake calipers & oem style rotors.

Lurch

Wow, I'm a noob, and I'm resurrecting an old thread, and I'm referring to a topic about 3/4 of a page ago, but please don't flame:

To go back to what was being said about the importance of inertia, I saw a demonstration of it in my physics course last year. The professor had two approx. 1 kg cylinders (same mass), one solid, and one that was hollow (like a pipe). They were both placed at the top of a 25 degree ramp, about 3 feet long. The cylinders were both ~4 in. in diameter. When released simultaneously the solid one was at the bottom while the hollow one was about halfway down. BIG difference. And remember, this is on a very small scale. Just some food for thought. You may now return to your regularly scheduled discussion, that you stopped 2 weeks ago....

SPiN Racing

Actually that is INCORRECT.

15x7 is the MAX wheel width of EP class. The RX-2 through the RX-7s also within this restriction of 15x7. We CAN run as small as 13X7 as well... but most if not all run 15X7... unless in one of the slower classes like HP etc on a Rabbit or some other car where they use 13x7 for gearing correction issues.

Here is the link to the page with the GCR for 2005. Click production category after the PDF opens (11+MB) and you will see it in the spec line for the wheels on each car.
http://www.scca.com/Club/index.asp?reference=gcr

Carl Byck

The perception that EP cars can run 10" wheels comes from the cantilevered slicks they run....

SPiN Racing

Possible... but they are 9.5" slicks... /shrug
Wheels.. (What he referred to) are only 7.

/shrug

If it was drag racing.. in whatever class takes a 10" slick.. then I would buy it easier...