You want to stick around the +50mm offset for scrub radius and the way the suspension is designed.


You want to center the wheel into the wheel well and stay around the stock scrub radius. If you can satisfy all these requirements you will get the best handling as per design of the car.


You only have so much room to go inward, an 11" +50mm will not fit because it will contact the suspension. so you have some options, you either get suspension that has a smaller diameter, run a less wide wheel, or push the wheel outward with a lower offset. Since lower offsets don't ride as well (they tend to pull the car left and right with road irregularities and put different loads on the wheel bearings and suspension, etc, etc I recommend sticking close to the stock offset.


so the tested fitments that are known to work are 18x9.5 +45mm and I think you can go to a 18x11 +45mm but won't get the full lock to lock movement as the wheel does contact the suspension a little at full lock. so a good compromise is probably a 18x10 +50mm if you can find it, or just run a 18x9.5 +45 with a 245/40/18 tire which is what I settled on. this requires no fender modifications and also gets you full turning without rubbing and another huge positive is the 245/40/18 tires are a lot cheaper than anything wider. its the best value to width in the 18" size along with a very close tire OD to stock.


I went all out with my FD rx7 and went with a +43mm 18x11.5" and rolled the fenders and have small coilover springs and run a stretched 285/30/18 tire. It does have more grip when heated up and takes a little more heat to warm them up. This car is also a lot faster in terms of WHP. I am running the larger 99 spec brakes and ohlins DFV on that car with softer rate springs 8/6.


comparing the two, I would opt for the easier fitment of 18x9.5 +45 and if you want more grip step up to a higher grip tire unless you want to go all out with fender rolling and custom wheels.

 

IOOkatme

Yes I was thinking about that

If a +50 mm (about 2 in) offset on a stock 18 X 8 wheel delivers a backspace of 6 in, being the center of a 18 X 8 wheel the 4 in mark, ( hence moving the mounting point of the wheel 2 in out wards from center point, delivering 6 in behind hub - 6 in backspace and 2 inches on front of hub ) then, in that case, a 18 X 10 in wheel for ie. would have its center pointat the 5 in mark

So on this 18 X 10 wheel on this example, having a + 50mm offset (about 2 in away from center point of wheel to the outside of vehicle-hub ) would deliver the mounting point with 7 in backspacing, 7 inches of wheel behind the hub , and 3 inches before the hub, outside side of wheel

That would give us 7 inches of backspacing versus 6 inches the stock wheel has

Not good

So if I want to keep the stock 6 inches of backspacing in an 18 X 10 wheel , I would need less than +50 mm offset

If 50 mm is about 2 inches and 2 inches offset leaves 7 inches of backspacing on the 10 in wide wheel, then half that amount of offset (50mm X 1/2 = 1 in or 25mm) would leave me with a desired backspace number of 6 inches, and 4 inches of wheel up front, towards the outside of vehicle, before hub

Would that be correct ? 18X 10 +25mm 6 in backspace .

Anything higher than 25mm offset on a 10 inch wheel would add to stock backspacing

A 9.5 inch wheel with +50 offset would have more than 6 inches of backspacing

For instance a 12 inch wide wheel would need zero (0) offset to have 6 inches backspacing Anything more than zero would send more than 6 inches inside the wheel well

 

I run 255/40/17 on 17x9 as autox and track set up

17s are lighter and tires cost much lower

 

My car is running on Koni double adjustable. And its adjusted to F 5" R 4.75". (Negative Rake).
Car drives great. But I wish I can get more front camber. Tire wear and temperatures show that I could benefit from it.

 

a wider wheel with the same offset of stock will get closer to the suspension. yes.


You do have some room to move towards the suspension. so rather than racking your brain over where the exact location is from the hub of the suspension, I would go with proven solutions.


we know a 18x10 +45 or +50 fits. so no math needed but on a 18x10 +50 you are getting really close to the suspension. You will also need to run a tire that isn't overly large as if the tire sticks way out you can contact the suspension on full lock turning, and even if you do its not the end of the world.


I know someone here has run a 18x11 +45mm and he does get a little contact at full wheel lock.


But I suggest going with a 18x10.5 +47mm PF01, storeoutperformance is the place that sells this special offset if you want max performance. you may have a little rubbing at full wheel lock when turning but that is ok and you will probably need to roll the fenders. Run a sticky 265/275 35 18 tire and the car should really stick. I got my 18x9.5 +45 for a really good deal so I am running them, I also got my RS-3 tires in 245/40/18 for a little over $100 each so it was affordable. You can find some enkei rpf1 18x9.5 +45mm for a little over $1K new, those I think look pretty good as well and are light and strong and needs no fender modification perfect to run those with a 245/40/18. The decision is up to you.


Keep in mind that driver ability is worth so much that this isn't going to overcome how much the driver matters. it adds some more grip and will be faster overall though.

 

Thanks guys

Will settle for 10 in wheels From what I read 9.5 to 10 is a good no issues size

18 X 10 +50 to + 47

I like and want as much tire & wheel as possible inside fender well

As much positive offset as posible Hate wimpy wheels with low offset that protrude the fender openings but have no substance

Function is also super important hence no 19 or over diameters

For outocross will use my stock wheels or would like finding 17 X 10 That is my next quest 17 X 10 with an offset that works with competition rubber For that matter 45-40 aspect ratio

 

a 17x10 with 255/40/17 is a good size, it will have a smaller diameter tire than stock but it would work well on that wheel width. We run that width a lot on rx7's.

I recently went through all this with my rx8...deciding on wheels that is. I went with 18x9.5 cause they are easy to find used. if you look at tires 245/40/18 tires are much cheaper on average than wider tires in 18's.

Another tire I would like to try is the federal FZ-201. looks like a fun tire to run, too bad all the sizes have smaller than the stock OD.

 

I hear ypu

Check this out A 255-45-18 is only slightly larger in diameter, unnoticeable when conpared to the 255-40 size

With a 17X 10 wheel A better size for autocross More stiff sidewall is better than a low sidewall




Not bad at all



Only slightly larger but wider as well

 

The Federeal Tire that proved to be a great choice for track and AutoX is the
Federal 595 RS-R and the new version RS-RR.

Better price and very fast.
The 255-40-17 are about 150.

 

17x10 is a great track wheel size IMHO.
What other mods do you have for autox?
17x10 will put you on a modified or prepared class.
If you are not interested in scca classing, it makes no difference.

We used to drive on STX, so 9" and 200TWR was the limit.

 

Hi

Been away for a while

Yes definitely that size sounds good fun autocross

So far my car is stock except for suspension which is Ohlins and Racing Beat sway bars

Definitely got to go to Willow Springs and start getting into some driving time

This suspension is great, and inviting, got to watch out !

Want no tickets ! But I am cool, do no stupid things on the road

����

 

Ohlins DFV is my preferred choice. Fantastic suspension after you set it up.
I have a little stiffer sway bars than those. Just a personal preference

In use the 9" wheels because I already got them from the AutoX STX set up, but If i can choose again, I will get 9.5 or 10" for the track.
However, I had not being able to use the full tire width on track yet, based on temperatures and wear. I need more camber. I should correct that before next event and test.

I imagine that you might not have the same issues because of your choice of sway bars and springs rates.

 

Bert88si

What sway bar brand you use ?

I may get a larger front bar eventually for autocross

 

I upgraded to Hotchkis F, and Mazda speed rear. First.

Now we have Progress front and rear. Both on full stiff.

It might be a little too much on the rear at full stiff now.
​​​

 

Progress Technology: Anti-roll bars, sport springs, coil-overs, camber kits and more since 1995!

 

Yes. That's the brand.

we installed the front because it was the biggest we could find. And made a huge improvement for autox.

Then we needed more rear bar for the track, so chose the same brand, since those are the biggest bars we found.

The car is way more planted.

 

Nice

Will get one as well

����

 

Comparing Racing Beat versus Progress Technologies Front Sway Bars


Both are hollow bars

Both are same overall diameter with 32 mm

The difference is within "Wall" thickness

Racing Beat's is 4.762 mm thick at the wall

Progress Tech's is 6.35 mm thick at wall

 

Good searching skills.

Sway bars selection, like any other aspect of the car set up is a matter of driver preference.

 

Hi.

My Ohlins suspension works great.

But a few weeks back I began to notice a clunking noise in the front that is getting more prevalent, upon going over speed bumps, rough terrain, and at low speeds.

That meaning highway driving is silent. Checked it out at a friends shop lifting the car up.

Everything looks solid, sway bars, suspension mounting points, nothing lose. Guys at shop tell me it seems internal, inside struts.

Called Ohlins. Jake told me to check mounting hat, make sure it is tight. Check sway bar all around.

It all seems tight.

From installation all seemed good. After about 2 months of driving it came apparent. It did not sound from the start.

Nothing will fall off, so I will keep monitoring the situation.

Ohlins tells me I can always send them the parts for assessment.

Will see.

Anyone had any experiences like this before ?

About rear suspension, would like to add camber adjustment, to prevent premature tire wear.

Any input in that regard ?

Thanks.

 

perhaps you need to add a little preload to the springs and its just the springs coming unseated from the perch?

 

I had a clunking noise coming from the front suspension. Turned out it was the top mounting nut for one of the front struts. It came off and the Koni proceeded to destroy itself by bashing the adjuster into the frame. That how I wound up with Ohlins.

Point being: Have you actually put a wrench on the nuts/bolts and made sure they are torqued to spec?

 

Checked everything and it seems ok

At a loss with this issue

 

I wish all the moderators who respond and/or read this thread would recognize that there's a dedicated suspension forum area and this 8 month long thread isn't posted there ... sigh ...

 

Hi

Will sort this out this week.

Talking to Jake from Ohlins.

About the rear camber on a lowered RX8. Anyone knows about this product ?

Megan Racing Control Arms and Camber Kits for 2005 Mazda RX8