-RX8-

Ok. So I've decided to run a 255/40-17 and I've decided to run it on either a 17x9.5 or a 17x10.

Sect width of the tire in question is 10.4 on a 9" wheel. Should be ~10.6 on a 9.5" and ~10.8 on a 10"

Tread width I can't find for that tire. But comparing to other tires I'm going to say it's ~9.8

A 9.5" wheel measures edge to edge 10.5", so given the tire's specs it seems to be a perfect fit. But I've been doing a lot of reading on several forums and it seems that a 10" wheel would be a good choice also. There's lots of talk that a 255 on a 10" wheel will provide the most mechanical grip. A 10" wheel measures out to 11" edge to edge and with a sect width of ~10.8 and a tread width of ~9.8, and the fact that the increased sidewall stretch would reduce flex in the corners and improve turn-in and transitons make it seems like it works well.

So basically what I'm asking is for any input from people with experience with those tire/wheel sizes.

And also, if the benefits of going to a 10" wheel outweigh the added weight of that 10" wheel versus the 9.5" wheel.

Razz1

Don't go 10" wheel we do not have the torque or power.

If you are FI 10" is ok, buut the tires are expensive and heavy.

I like how the car in more nimble with a smaller width wheel.

tomsn16

What is your end use....AutoX , Track , Street ???

-RX8-

Wether I go 9.5 or 10 it's still going to be a 255 tire. I'm not building a drag car so it doesn't matter about the power.

Autox and street

TeamRX8

iTrader: (25)

There's a ton of data on that size and it comes down to your wheel offset, but I won't be a jerk and tell you to search

oops ....

-RX8-

It's ok team, i've learned to expect that from you.

I've searched. Not super very extensively. But well enough. It's hard filtering out all the bs just to get to a snippet of info

TeamRX8

iTrader: (25)

Well I ran 265/35-18 on 18 x 10.5 +43 without fender mods if that helps. Nobody else had done it before. There was nobody for me to ask or otherwise acquire the info from.

that's ok, while I may have expected the same from you too I was hoping for better. You can't expect to find all your diamonds on the surface or just have them placed in your hand. You might actually learn more than you realized by reading through a bunch of stuff.

Try the wheel/suspension area, specifically the "will it fit thread"

Spin9k

The way I decide is to refer to the tire specs. Of course there is the 'measured' wheel width recomendation. That's the balance for precision vs. comfort. Buy the stated narrow width for comfort, the wide width spec for best precision. For track take the middle or wider for more sidewall support..I use 9.5 for my 255s, but tires do differ. For autox I have no idea.

-RX8-

yea that does help. And I know what you're saying. I usually do read through everything but I'm short on time today and it's just one of those things that I've had on my mind today.

Thanks for the pointer though. I don't need to know the answer per say, just where to look would be fine. You gotta admit it's not easy looking for a specific thread when you don't know what the thread could even be called. I don't need to know the answer per say, just where to look would be fine. I'll check the will it fit thread

no hard feeling man

EricMeyer

Do you currently run (or plan to run) an upgraded suspension? If you just add a big huge 255 tire you're not tapping the potential of the bigger tire.

An RX8 with a 225 tire and a well tuned suspension will walk a stock suspension with a bigger tire on a road course. Handling is a system and the tire is one part of this system---a very important one. There will be a lot of grip available to you with a 255 tire and using as much of it as you can is your objective. I assume you already have increased your spring and bar rates but if you haven't, you might want to plan or budget on doing so. Handling is a SYSTEM which some people (maybe you, maybe not) don't understand. My assumption is you are road coursing this car because you have posted under the RACING portion of this forum.

A big tire will mask and hide your cars true handling characteristics. My experience with many drivers/students/other racers is this: If you put a big tire on your car as one of your first car mod efforts for the track you will find it harder to understand what your car is trying to tell you. For example, is my car understeering on entry and continuing through mid corner for longgg sloow corners when the car is experiencing a high rate of roll? This prevents the driver from applying throttle as he/she has to wait for the car before power can be added. This is slow(er). Is my car oversteering on exit because I have the wrong sway bar(s) or incorrect swaybar settings? Is the rear end of the car getting light under heavy braking and immediately going to loose with steering wheel input (which often can happen in an RX8 with increased front tire grip yet still uses the stock front springs).

The car handling learning experience is very rewarding and if your goal is to learn as much about driving and improving your skill set keep in mind that the big tire will hide or mask these learning opportunities.

Taking the approach of modifying a car and having lots of fun right out of the bat is fun (although not as fast in the long run). It all depends on what you want to accomplish, available time, budget....

Happy rotoring

TeamRX8

iTrader: (25)

now you see why it's better to search ...

-RX8-

Actually at the moment I'm driving a beater. I just came from an ap2 s2000 which got stolen a few months ago. I'll be buying a base 2009 rx-8 as it's replacement in a few months. And I completely agree with handling being a system. I actually think that the car in general as a whole is a system. Motor mods, tranny mods, handling mods; IMO it all ties together. With that said I plan all my mods ahead of time so that I get it all on paper and have time to think everything through instead of just diving in and buying random parts. My plan of attack is as follows:

1. Keep it stock throughout the life of the stock tires. At 5000 miles I'll rotate them and spec out an alignment based on the driving I've done with it so far.

2. Switch to 225/40-18 Dunlop direzza star specs when the stock tires are done
get hotchkis sway bars shortly after, and eibach multi-pro r1 (maybe) coilovers shortly after that.

3. After those tires wear I'll be switching to a 17x10 with the 255/40-17 Dunlop direzza star specs and adjustable endlinks so I can corner weigh it.

4. Brake upgrades; racing brake 4pots, 2-piece rotors all around, ss lines, castrol srf fluid, hawk hp+ pads

5. After that i start my weight reduction regime, I'll be looking for racing seats/harnesses and start looking at various weight reduction options.

6. Then motor/drivetrain mods as I see fit.

Thanks for the reply!

I still would like opinions on my origional questions.. Reason I started this thread was for opinions from people who have had these setups

Symbioticgenius

Yo Eric, that was amazing bro. I didn't realize any of that.

Would it be correct to assume then that it might be in fact better to upgrade suspension components as you learn the car before you upgrade the tires?

EricMeyer

I don't know about better. I just wouldn't put a big 255 R compound tire on the car and then go to the track. Small changes are best because you have the opportunity to learn what these changes do. Starting with a stock manual trans RX-8 I would tell a driver to just drive the thing. Then upgrade the bars. Drive it some more (probably need a new front left tire because the outside will be toasted). Get a more favorable alignment which has more negative camber. Drive it some more (tire life will be better) however you'll also be going faster as you have more grip and your skills are developing. Upgrade the springs next and do NOT slam the front end. The suspension geometry on these cars favors near normal or stock front ride height. A slammed nose will have understeer tendancies. So------you don't need to subscribe to the "slam the car to lower the cg to make it handle better" mindset. Drive the car some more and now you are pushing the entire car and the tires are most likely the constraint to going faster. You know have got the most out of your components, learned a lot from a car that offered you great auditory and kinestetic feedback and it's time for a set of tires (and why not wheels). Buy 4 of the same size in a 17 x 9 or 9.5. 225-245 rubber can be mounted on them. Add more grip and go have fun. Do NOT get a directional tire. The hot ticket is to be able to move your tires all around your car. This helps maximize tire life. Front left generally gets the big wear, right rear gets the least. Drive Saturday and rotate them Sat night or Sunday a.m. Party on Wayne. Owning and using a tire pyrometer correctly will help you get even better use of your tires. If this topic interests you then I'd do a lot of searching on the camber topic on this forum and read, read, read. Adding more negative camber for better open track performance is something you need not be afraid of.

Contact a race tire distributor (I'll suggest my good friend Phil Phillips of www.philstireservice.com Phil is awesome and offers a ton of value. From Phil I learned how to study tires and "flop" them on the rim to extend tire life. I often suggest to my students and friends that if you want to go up to an R compound tire try the Toyo RA1 or 888 at full tread depth (also called the rain tread depth). When you do this after you've "earned" a skill set you will be much faster than the person who slapped these same tires on right off the bat. That's my .02. Email with questions if you like.

EricMeyer

You don't need to upgrade the brakes so buy me a beer with all the money I just saved you. There is no reason to wait to upgrade your brake pads and fluid. You might as well do the stainless steel brake lines while your at it. Remove the giant frisbee dust shields and give them to the trash man. Both front and rear---dump em.

And I would try not to have such a detailed plan. Your ability to understand what your car is doing should take precedant over what YOU THINK your car is going to need in the future. Drive it and then assess accordingly. I've seen many people (not only RX8 drivers) get caught up in the "mod your car" trap. I guy called me today and asked me what he should do with his new $16,000 upgraded suspension he put on his Saleen Mustang. The poor guy had never been on a track. I told him to sell it to the first person who makes an offer, buy a stock Miata and take the savings and drive twice a month for the entire summer. He will still have money left over. So watch your mod plan my friend. Enjoy the journey and try not to rush things. It would be a reasonable amount of time to do something as simple as adding aftermarket swaybars only and drive them for one event a month for a summer. Add springs and shocks the following fall and drive that setup for the season. You have to (IMO) allow your driving skill set to catch up to your mods. The best examples are those great corvette fans that buy a new Z06. AWESOMELY capable car and it's so good it makes a shitty suck *** driver think he can leap over tall buildings. The CAR is fast, not the driver. This is same scenario for the new RX-8 open track driver that overly mods his car before his first DE weekend. Drive the damn stock car and enjoy it. The time will come (and you'll know it) when you need to make some upgrades---this is dictated by your driving skill and not your wallet. Did that help you?

-RX8-

You know your stuff man! Thanks for contributing

altiain

iTrader: (3)

FYI - you mentioned autocross and street as your intended targets. With that in mind, and based on the fact that you're going to be using 255 street tires, I would suggest limiting your wheel width to 9 inches. Here's why:

• 255s work just fine on a 9" wheel.
• 17x9 wheels are lighter than 17x9.5 or 17x10 wheels. Less weight is good. They're typically cheaper as well.
• 9" is the maximum allowed wheel width for the SCCA's STX class... which your car sounds like it will be a great fit for. It would suck to buy 9.5" wheels just to discover a month or a year from now that you really want to build the car for STX, only to have to go out and buy another set of wheels.

That's my $.02. Take it for what it's worth.

chiketkd

iTrader: (5)

I'd have to agree with all three of Iain's points.

From your long-term "planned upgrades", it definitely sounds like STX would be a good fit for your car. I'd also stick to a 9" wheel with the 255 tires.

-RX8-

I hadn't given autox classes much thought. I will definately put that into consideration.

Thank you

EricMeyer

High value-added post.

olddragger

iTrader: (3)

thats the ticket--so much depends on the drivers "style", the tracks they drive ( high speed, low brake courses, low speed high brake course etc etc.), is this a dedicated track animal or one thats see's one event a year.
No wiser words ever spoken--start out oem and figure out what you need to get where you want to go .Learn as you go along so that way you may not get stuck with a 4K system that is too rough for a DD.etc.
I have has just as much fun turning a 2+ minute lap at road atlanta as i have had turning a sub 1:50.
Learn Smooth.............. on all of it--- turning braking and throttle. Learn track management---then go with a faster set up if that is still what you want.
In oem form this car has more to offer than most beginning drivers can use.
OD