Because I found out the hard way that the taper for the MX5 bushing did not match the LCA BJ taper on my 2005 S1. Another S2 member had a race shop install them on his car; supposedly without issue. That’s how we arrived at that conclusion.

However, I’ll temper my words some by saying that while the taper didn’t match, it was possible to bolt them on. The BJ stud would only be contacting on the hole opening entrance edge on the bushing though and not against the tapered surface or anywhere else except between the nut on the other end of the stud. And then the BJ stud is also not fully inserted into the bushing either and the nut isn’t engaging all of the stud threads. When I discussed this with someone at the bushing supplier I was told they never had a complaint or had anybody tell them this before. So I suppose it’s possible that nobody ever noticed and they were installing them this way.

I see two problems if that was the case. One, all the stress would be that corner edge of the bushing around the stud at the one point. You’d be risking the stud shear fracturing there. Two, because the stud doesn’t insert fully into the upright that changes the suspension geometry position of the upright, which for some classes would not be a legal modification even though bushing changes are allowed for camber purposes.

I wouldn’t be surprised if that was the case actually because at the time they said it was the first and only batch on those bushings then. Which this is obviously a new batch. So maybe it was never actually correct. I can’t be sure without having the alternate parts in hand. It wasn’t an issue of it not being bored deep enough; a specific taper is a specific taper. When the stud contacted I could look in from the other side and see clearance around the stud everywhere except at the entrance hole edge. As best I can remember, the stud was about 1/4” or so from installing fully into the race MX5 bushing as compared to my OE S1 upright bushing. The depth was the same and the small threaded end hole was the same, but the big end hole was a smaller diameter. By all accounts, the wrong taper.

Also forgot that the S1 bushing diameter is also different. So you either have to also machine that down, or alternatively swap to S2 LCA, UCA, and uprights for a straight bolt on , or lighter NC MX5 suspension parts might also an option.

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Last night Matt (hufflepuff) and I (well mostly him :-), thanks Matt once more) transferred his fortune auto coilovers on my car. will take car on the alignment rack to see how much camber I have now up front now at ~ 13.5" ride height.

How much lower than 13.5" inches can I take the car down if I don't get more then -2/2.5 degrees of negative camber up front without sacrifice to track performance?

this is not daily driver.

Awesome to have another set of Fortunes in circulation for feedback. I assume Matt is moving to another set with different spring rates?

The ride height you can run is determined by a series of factors and is unique to each setup. Most of us run within 1/4" of 13.5", because it is a known-good value. Perhaps a few other folks will chime in with their setup information.

Like most suspension things, it's complicated and involves a lot of math. But here are some peripheral things to consider:

1. Tire diameter
2. Stroke range of the shocks
3. Bump travel (rear)
4. Auto parts locations

1. I currently run 13.5" on stock tires . My track tires are shorter, (255 40 17), which drops my car 0.4" when the track wheels are on. Because of the extra space in the wheel wells, I could lower the car more and benefit from more negative static camber. This also gives me a small torque boost at the cost of top speed in each gear. My next set of tires will probably be 235 45 17, which will take 0.2" of that away, however. Why? That size is cheaper, lighter, and has a stiffer sidewall on 9" rims, with no real world impact to contact patch width.

2. Shocks have a published stroke range in which they work best and should not bottom out. Going outside this range tends to compromise performance and wear the shocks out early.

3. The RX-8's rear has somewhat limited bump travel. You want to hit the bump stops as little as possible, obviously. This is controlled by spring rate, spring preload, ride height, and rake. You can probably go a little lower than I can due to your higher spring rates.

4. Fenders, fender liners, control arms, springs, etc. all start to get in the way as you go down and gain negative static camber. This is another limiting factor.

Then, there are things like roll centers and their relationships to center of mass, etc.

Finally, it is not worth going too low to gain a tiny amount of negative static camber. Dropping the car to increase -camber becomes self-limiting very quickly. This is why Team and I had offset bushings installed. They allowed me to raise the car and still achieve the camber I want.

How is that for a non-answer?

With offset delrin bushings on the UCA and the offset bushing on the LCA ball joint it looks like I can get to 4 deg fairly easily at that ride height even though I don't anticipate ever needing that much.

Been weighing out my tire options based on that same premise too.

Exactly the info I was looking for, thanks!

So you are on 13.1" ride height on track tires which are same size as mine if I red your post right?

I was unclear about something above. Smaller diameter tires do not affect the ride height from fender to center of hub. They do affect ride height as measured from at the pinch welds to the ground, which affects roll centers and center of mass.

My fender to hub height is around 13.5", varying based on corner balance.

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13.5" is a pretty good place to be. You can go a little lower (I was running 13.3 for a while), but you might end up riding the bump stops too much, or bottoming out in high camber turns.

If you have an S1 then hopefully you also have S2 uprights and LCAs coming too.

Yes, although I had planned to machine them down, I actually found some used knuckls, complete with hub and figured it would be worth it just have the spare hub+bearing.
I'm not sure about needing a new LCA (or upper control arm) with the new version of the bushing. I'll take a look and report back once I have all the pieces in my hands...

Ok, just making sure because sometimes people underestimate the ridiculous situations I somehow managed to muddle my way through :lol:

I am having a set made for my RX8 by a friend. I didn't measure the NC version when it arrived but it was obvious that the ball joint taper/diameter way off, it's smaller on the NC vs the RX8. Because of that we decided to try to make a RX8 specific version. Will probably have a set within the next week.

Ugh. Did you get the latest PN? I wonder why they have it listed as being compatible with the RX-8 (2009-2011) then?

Mine (0000-04-5407-NC) arrive tomorrow. I have an S1 arm sitting on the ground so should be able to check the fitment to that pretty quickly.
S2 knuckles+hubs arrive in the next few days...

It was the diameter of the ball joint taper that most concerned me. Also, I was flatly told by the Mazda Motorsports rep that these would NOT work with a RX8 S1.

Here's a gallery of a comparison I made.

https://imgur.com/a/qz8eDKB

He was referring to the 2004-2008 S1 only, just as I previously reported.

So I had a look at the bushings last night. You are correct. The inside hole is too small for the LCA ball joint taper on a 2004. I was really hoping this was an issue with the early PN not having had the correct taper cut, rather than due to a difference in the control arms between s1 and s2. Turns out that was wishful thinking on my part. Given the different PNs, I expect the upper arm will also have a different size taper as well, so if you want these without modification you're going to need s2 lower arms, upper arms and upright (knuckle).

Edit: someone reported that the S2 UCA stud is different than the S1 too

again for anyone who missed it, the bushing OD is also slightly smaller on the S1 too. So reaming out the tapered stud hole and machining the OD down slightly are two modifications required to make them fit on the S1 upright.


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so has anyone used godspeed upper CA camber kit?

https://cimg0.ibsrv.net/gimg/www.rx8...9486cfc572.jpg


https://godspeedproject.com/mazda-rx...-bearings.html

https://cimg5.ibsrv.net/gimg/www.rx8...d737cae36a.jpg

Heim joints can be harsh and noisy on the street. They’re also not legal or have a penalty for the competition classes where most people here are running. I suspect they’re heavier than the OE aluminum arm too. Some people built their own back in the day, but otherwise just hasn’t been a popular mod to date.

https://cimg4.ibsrv.net/gimg/www.rx8...e817ffe326.jpg

Prototype S1 RX8 offset knuckle bushings. Will be installing next week for testing.

Well somebody posted up in the DSP thread that Motorsports says they have one coming for the S1 upright

please don’t shoot the messenger, lol. Or maybe that’s it I suppose.

is that tapered to the S1 ball joint stud? Kind of looks non-tapered, but maybe just the angle of the photos.


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It is tapered for the s1 ball joint.

Re: Motorsports coming out with one, well... That's the marketplace at work!

Typical that I hold off for ~2 years, only when I finally decide to take on the cost/pain of modifying for the S1, two different companies announce bushings :-P

I got my s2 knuckles and the bushings appear to be a correct fit in those.
However, the ball joint stud on the "s2" lower arms I received also looks big for the bushing. I only got as far as unpacking the lower arms, and didn't have time to inspect further, so I need to double check these and compare to the s1 arms which are still on the car.

Somebody else posted up that the UCA stud is different too. Sounds like you need all three, but Motorsports is soon going to have S1 offset bushings available.

OK, well the upper control arm stud is clearly different between the s1 and s2.

How obvious should the difference be in the lower control arm stud? Holding my s1 arms next to what I am told are s2 arms the two look identical. They also seem to fit in the bushings in the same way... I tried measuring with calipers and as near as I can tell they are the same as well. Both arms also have a -3 revision number which makes me wonder though...

I also compared the hole in the bushing in s1 vs s2 knuckles and look the same as well. Tried measuring with calipers too and no real difference. The outer part of the bushing is smaller on the s2 knuckle though so it will fit the offset bushing.

The offset bushing looks a little taller than the bushings in the knuckle. So the ball joint stud does not extend as far from the back side. That's the only difference I can tell.