Cito

The answer is "yes" and "no." You must use the same diameter and width with offset being within 1/4" as specified by the factory for the model you have. So, most RX8's can run 18's.

If you have an R3, you must use the 19" wheels unless there is some option for 18's that I am not aware of.

Otherwise, AFAIK, all other manual RX8's run 18x8 with 50mm offset.

chiketkd

iTrader: (5)

The '09 RX-8 R3 only came with 19x8" rims, so unfortunately that's the only rim size Saini can use. All other RX-8 models use the 18x8" rims.

edj

Don't forget the tires!

I recommend the Kumho Ecsta SPT tires in the 245/45R19 size.

Should just right for the gravel pit in Houston!

Jason Saini

Registered for the first test/tune, March 1st! Should have the experimental Tri Point swaybar, Racing Beat exhaust, and a set of 'short' Motons just to start getting a feel for valving. Also should have 5mm wheel spacers, and will be on Hoosier 235/35/19's.

Looking forward to it!

chiketkd

iTrader: (5)

Jason, be sure to post some pics of the car in action!

mwood

Looks like Jason is taking BS RX8 prep to an entirely new level...I'll be interested to see how it goes, for sure.

You BS guys are going to have a hell of a class this year. Not only someone with Jason's cred jumping in, but also a bunch of the top guys from past years are back and I know of another team, out here in the Bay Area, that is going to be very, very fast.

chiketkd

iTrader: (5)

Hey Jason,

Any idea what whp a bone stock '05-'06 Mustang GT makes on that dynojet?

I'm taking my '06 RX-8 to a dynojet in Richmond this coming weekend. My car has fresh plugs, plug wires and coils as well as fresh synthetic gear oil in the trans and rear diff. I also use a green panel air filter and the version 2 Mazdaspeed catback (dual mufflers). I won't have the time to install my race exhaust beforehand...

-Chike

Jason Saini

A Stock Mustang GT ran 267 on our Dyno, for comparison.

Just got the Motons and swaybar on last night... car feels racy now! The dimensions of the Bilsteins are exactly the same in every way to the early shocks, in case anyone cares. Also, good news in the rear - and I wish I would have thought of this a while ago:

The overall length of the rear shock is within 3/4" so it's just the body length that's the issue. I'm having a delrin spacer made that will be taped to the body and effectively lengthen the body. That way, Club-Sports will be usable for stock-class, and they are pretty cots-effective at $3400/set retail.

I'll post pics soon, and give everyone a report after this Sunday's test/tune.

ULLLOSE

iTrader: (1)

I don't seem to come up with the same numbers as you based on the tech drawing for the Club Sport. Based on a 2005 OE sport shock the Moton is 1.36" shorter overall front, and 1.57" overall shorter rear. The compressed length is also shorter on the Moton, at .604" front and 1.353". These measurements are mounting point to mounting point.

Based on being allowed +/- 1" on shocks I don't see how these can work, they are over 1" shorter extended, as well as being shorter when compressed.

Are you including the adjuster length rather than just the mounting points?

Is this drawing wrong? It is very possible that the drawing does not match a production piece.

M 521 002 00 Mazda RX-8 - Miata.pdf

chiketkd

iTrader: (5)

Perfect. Thanks Jason. I'll post up my dyno results this weekend.

Looking forward to the pics!

P.S. Btw Jason, do you know if there's any truth to the rumor that the R3's got stiffer springs? Any idea what the rates are?

Jason Saini

I'll go do some more measuring... much of this was just laying shocks next to each other and measuring the difference. The 'mounting point' could be modified pretty easily on the top by putting a .36" spacer on the front, and a .57" spacer on the rear. Coupled with the body-spacer I already mentioned, this would bring the shocks into compliance. I see the compressed length as completely irrelevant since it would hit the bump stop way before the shock. Obviously this gets into a letter of the rule versus intent... if usable suspension travel doesn't change, I see no reason to disallow.

I'll get the measuring tape, metal ruler and calipers out in a little bit and do some serious measuring this afternoon.

Ostensibly, though, the R3 Bilsteins are no different dimensionally than any other RX8 shock, so my measurements will apply to everyone.

I think the springs are the same, or VERY close - they have different color paint dots than standard springs but the diameter of the wire looked very similar... I will get the caliper out and verify. The car 'feels' stiffer than any other RX8 I've driven, but that could have been the Bilsteins.

ULLLOSE

iTrader: (1)

Can you maintain the OE travel with the spacer? By my measurements the potential travel is already less than OE, so the bump stops will have to be cut down. Then you add the "body spacer" to make the length right. Then the trick becomes convincing a PC that the spacer is part of the "body" and not a bump stop - I think I would make it out of aluminum and epoxy it to the shock, just to be safe. Or a real trick method would be a spacer that threaded onto the body.

Jason Saini

True, I already talked with Moton and they can make a 'taller' shock cap which would alleviate any concern that it's a bump-stop or part of the shock body. I would think that if an aluminum spacer were epoxied, it would stand up to a PC.

As for travel, you are misunderstanding me - I'm not arguing that the 'potential' travel wouldn't be different, just that the wheel-travel wouldn't be different. I think the rear is a slam dunk, with both spacers on it... .36" on both body and shaft, would effectively 'lengthen' the shock by that much making it totally legal.

The front is a little trickier, ironically, as it's compressed length couldn't be changed. However, I need to get measuring to see if it can be brought into compliance.

FWIW, I've seen (and personally run) spacers on a shock body to bring that length into compliance before and never had a complaint/problem come up.

Anyway, would be nice if I could make another shock option viable for Stock Class RX8's, and it would be nice for me too since I already have a set of these to use.

ULLLOSE

iTrader: (1)

No, I get you... Being allowed to shorten/replace the shock mounted stops typically makes its easy to keep bump travel legal. But with everything being shorter already, I wonder how small of a stop you will need to use, and if it will still be effective. I suppose you will get into spring bind before you have to worry about to short of a bump stop with a short shock body.

Cant wait to see some pics. Are you just going to fit the OE perchs on them?

Jason Saini

Yep, we had some steel collars made a while ago that allow the stock perch to ride on the Moton threads. I've got some pics of the install. I didn't cut the bumps stops yet, I want to see how it reacts like this. Sometimes a bump-stop isn't a bad thing, if you can control it! Just excited to get some initial testing underway. The 235/35/19 A6's look quite a bit wider than a 235 too!

You can also see the Tri Point front swaybar in the front pic... trick piece, just for testing purposes now but we will have something available eventually.

chiketkd

iTrader: (5)

In terms of section width, I think Harvey has said the 235/35/19 A6 is somewhere between a 245 & 255 A6.

Edit: Here's the post from Harvey on page 2 of this thread:

chiketkd

iTrader: (5)

Well, I took my car to the dynojet today knowing that it wasn't 100% as I have a vacuum line leak (on my airbox) that I wasn't able to fix beforehand. The replacement part should arrive this week.

My car made 164.4hp and 129.8wtq. Peak power was reached at a lowly 7,200rpms and the curve became flat afterwards. The afr's varied between 11.9-13.5 in "open loop".

The dyno shop had a bone stock '05 6MT on their dyno previously, and that car made 179hp and 127tq.

I'll be fixing the vacuum leak this week and time permitting will re-dyno the car this spring.

P.S. A stock '05-'06 Mustang GT makes 250-260whp on this dyno.

Jason Saini

Oh, that was fun today! Car was awesome, made changes throughout the day, happy with how it was working and with the result. I did a 36.6, and that was about 2nd fastest raw time, although it was only a test/tune. I did a 36.7 in an STU car, and a 35.6 in a CSP car, so on index the RX8 was best. Both the STU car and CSP car weren't 100% in either prep or state of tune - but neither is our car yet!

What a great day, I look forward to this season and getting to some more autocrosses! Houston Tour is probably next. Will have the Motons compliant and figured out by then, and actually have an exhaust, lighter wheels and brake pads by then!

As a data point our car was 3082 with a FULL tank of fuel, about 15-20lb of personal belongings, the tool kit and jack (5-10lb) and the stock exhaust. With the light exhaust, all the crap out of it, and a quarter tank of gas I estimate it will weigh around 2960ish... not sure where that stacks up, I'm sure not the lightest - but boy does it look good!

Pics tomorrow!

chiketkd

iTrader: (5)

Jason,

This is a thread with B-stock weights from 2007: https://www.rx8club.com/rx-8-racing-25/2007-scca-nationals-b-stock-weights-133564/

The '04-'05 models are lightest, the '06+ tend to be about 15-20lbs heavier (due to a larger starter and battery). In 2008, my car weighed 2830lbs on the in-ground scales at HPT with a 1/4 tank of gas, OZ Ultraleggeras and 245 V710's.

P.S. Got the parts in this weekend and replaced the broken vacuum line and fitting on my car. She should be 100% right now, but unfortunately 5-8" of snow is on the ground and I won't be able to drive her until Wednesday at the earliest.

Jason Saini

I'll have to reweigh the car then... I know it will be heavier (trans is about 25-30lb more, etc.) but I didn't think it would be 100lb more! They must have used heavy foam in the subframe, lol.

Excited about how the car worked with the tri-point bar and Motons... it was very stiff, barely body-rolling, AWESOME in slaloms. Car was very neutral everywhere but on corner exit, and there it was reasonable in balance if not slightly pushy. I'm very happy with how it went at a first crack! I think the car will be very competitive, and with no offense meant to the current Koni-Yellow and drilled bar setup (which works quite well, despite the body roll,) this setup is more fun to drive. Having driven Ken Baker's car in '07 (thanks again, Ken!) this is way more fun! It just feels more like a race car.

chiketkd

iTrader: (5)

Jason,

Weigh the car on the portable Longacre scales the scca staff takes around with them to NT's and Pro Solos. These portable scales read a little high as my car weighed 2860 on them.

I'll be weighing my car on them again at the Dixie NT this month. I'll post up my weight in this thread.

P.S. That moton & tri-point bar combo sounds awesome. You talked about a 'slight' corner-exit push. How much camber were you able to get upfront with your '09? I'm at -1.8 with my 2006.

shinronin

hey guys, if i can tempt anyone into the moton club sports for BS i have a set f/s for $2800. they were used for 1 season of STU. jason can sort you out with the spacers and perches.

shipdriver

The R3 is not a model but an option package. I see nothing in the rules (please point it out if I'm wrong, I'm not the highest expert) that says the wheels must be the same as the specific option package. The rules only seem the recognize the "RX-8" not the RX-8 GT, Sport, 40th AE, R3, etc.. I can't see why 18x8 wheels can't be fitted to an R3.

ULLLOSE

iTrader: (1)

The R3 comes from Mazda with 19s, that is the only way to get it.
Sec 13 Except for modifications authorized below, Stock Category cars must
be run as specified by the factory with only standard equipment as
defined by these Rules. This requirement refers not just to
individual parts, but to combinations thereof which would have
been ordered together on a specific car. Any other modifications or
equipment will place the car in Street Touring, Street Prepared,
Street Modified, Prepared or Modified Categories as appropriate.
Configurations involving damaged parts (e.g., blown fuses) are not
typically authorized by the manufacturer and hence are not allowed.



Standard wheels for an R3 are 19".
13.4 WHEELS
Any type wheel may be used provided it complies with the following:
it is the same width and diameter as standard, and as installed
(including wheel spacers if applicable) it does not have an offset
more than +/- 0.25 inch from a standard wheel for the car. The
resultant change in track dimensions is allowed.

shipdriver

My question is whether the RX-8 comes with 19" wheels as standard. Of course, the R3 does, but it is an option. It seems that the rules come down to semantics because they don't really account for cars which have multiple wheel sizes from the factory. If they did, it would probably be too cumbersome anyways. Obviously at the local level, no one will (well maybe someone will) protest against wheels on a RX-8 that come on an RX-8. At the national level, do they actually differentiate trim packages and factory wheel options (good lord, Porsches must really complicate that one) to determine this?