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.

You have to measure the stud diameter where the taper ends/transitions to the full round/non-taper part ( the big end). I was pretty sure the bushing length was the same, but the diameters were different. Someone confirmed that in the DSP thread. It sounds to me like the stud is not fully inserting into the bushing, which is what I reported because of the diameter/taper difference. When you look in from the threaded end side is there a gap between that end of the stud and the bushing?

They weren’t the same on my S1 and it wasn’t the original arm. I swapped it out around 2009/2010 with another new S1 arm from Mazda. Which even Motorsports acknowledges the difference since they’re getting ready to release an S1 specific bushing.

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I'll be throwing these in my car Thursday so I can try some higher camber settings at Crow's this weekend.

https://cimg0.ibsrv.net/gimg/www.rx8...92d05e33fd.png

Aligned car the other day
 

After coilover installation and these ride heights here are the alignment specs that I was able to get out of the car.

Front L R
13 1/8" 13 3/8"
Rear L R
13 3/8" 13 7/8"

https://cimg1.ibsrv.net/gimg/www.rx8...a8d3492eb.jpeg


Front left wheel was at the maximum negative camber setting for the camber adjustment bolt, there was more camber on the table for the right front but I wanted to make everything equal.

OK, so yeah.

s2 (2009) knuckle bushing is 24.51mm tall and the taper hole is 16.52mm at the narrow end. 19.86mm at the wide end. 29.98mm outer diameter.
s1 (2004) knuckle bushing is the same, with a 26.93mm outer diameter.

Mazda mx5 offset bushing is 24.33 tall and the taper hole is 15.86 at the narrow end. 19.86 at the wide end. 30.00mm outer diameter.

So basically, the outer diameter of the mx5 bushing matches the s2 (2009) knuckle, but the taper hole is smaller at the narrow end, meaning the LCA ball joint taper will only make contact at the narrow part and not insert all the way.

I also have some LCAs off what I am told is a 2010 RX-8, and the taper on those is the same as the ones on my 2004 as far as I can tell. 17.12mm at the narrow end, 20.10mm at the wide end. Those measurements are approx 19.0mm apart. (I measured these as low down as I could get without removing the rubber boot).

It doesn’t really matter any more since they just recently released the S1 version, but thanks for following up.

OK, now for the crazy part. The taper on the mazda offset bushings seems to match the taper on my lower control arm studs much more closely than the taper on the bushings in the knuckles. The LCA studs come out to a taper of around 1.9in/ft. The offset bushings 1.98in/ft and the factory bushings around 1.64in/ft.

Using a different calculator and multiple measurements of the studs, I get 9.4 degrees for the offset busing, 7.8 degrees for the factory bushing, and a range of 8.91 to 9.85 for the stud (although seems closer to 9.85).

The stud also inserts to the same depth in both bushings. 18.6mm of thread protrudes out the other side.

So, either I'm going crazy or the oem size is different to the studs? Or the original s1 had a different taper (I replaced mine as the ball joint came apart).

now I am confused, so mx5 offset bushing is not going to fit S2?

Deleted an overly complex and rambling post of confusion. See my next post for some clarity :-)

It will. I just spoke to Mazda Motorsports and confirmed this. 0000-04-5407-NC is a direct fit for the s2.
To fit it to the s1, you need to machine down the outside diameter, or get some s2 knuckles and upper control arms to match those (or otherwise fix the upper control arm bushing taper)
The taper on both s1 and s2 LCAs is the same.

There was actually an issue with the earlier run of bushings that was the source of the confusion (those were cut with a 7-8 degree taper). TeamRX8 reamed his out to fix this, but the new ones I have (0000-04-5407-NC) are already cut to the correct 10 degree taper.

EDIT: Just to add, Mazda Motorsports are awesome. I should have called them earlier!

For anyone who wants the offset bushings now:

https://www.mazdamotorsports.com/201...fset-bushings/

Part No.: 0000-04-5407-NC – 2006-2015 MX-5 & 2009-2011 RX-8
Part No.: 0000-04-5407-R1 – 2004-2008 RX-8
Prices: $75.00

I was told that the set for the series 1 may be on backorder as they only did a small production run not knowing how much demand there would be. But anyone wanting a set should put an order in and they can have more made within a couple weeks (I would still suggest calling if you have a deadline for these).

Trust me, I called everyone possible back in 2017; lol, but I’m glad somebody finally straightened it out

It's possible this was not known at the time. I think they re-measured the stud to create the spec for the more recent revision.

Also, thank you for all the info posted in this thread. Before calling I went back to one of your earlier posts with the ball joint stud measurements and that helped a lot.

It seems like they’re being made by a different supplier now. A rep for the supplier then claimed they just duplicated the MX5 Cup car part, but otherwise didn’t seem aware of any problem. Like I stated before, imo people were likely just installing the part and bolting it up without any consideration on whether there was a fitment issue or not. I’m guilty of the same sometimes, like recently finding out that the RX8P engine mounts result in lowering the engine approx. 1/4” despite the website claiming they maintain the OE engine position. Which could cost someone a championship for certain racing classes. You need to double-check everything to your own satisfaction rather than blindly trust anyone else. That’s a lesson for RaceCar101.

I ordered a set of S1 and S2 bushings just to put on the shelf. At some point these could disappear just like most of the prior SpeedSource parts.

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Ordered 06/15, credit card just charged today, 06/30. Guess they are in and Mazdacomp works on Sundays? :dunno:

No, they would rather eat glass than be there one second more than actual business hours, lol. I’m still waiting on mine to ship that were ordered two weeks ahead of yours.

haven't seen you on the track this year at all, what have you been up to?

They still seem to be on backorder.

Hi to all again,
I finally got time to change my uca bushings with polyurethane offset ones. Before I continue, I must say the OEM bushing are very good quality. Although rubber the metal outer flanges give it that extra stiffness when needed. Felt kinda bad replacing them.
So my problem... Pressed in the polyurethane bushings, then the inner sleeve. Probably do to compressing the bushing it expanded, length wise. So now each bushing is about 2mm longer then the sleeve. The control arm wont even fit in the subframe bracket.
Im considering trimming off some polyurethane?
Is this a common practice?

I think most people just cram them in, but personally I shave down the "ears" of poly bushings until they move with little stiction when fully torqued down. To shave them I used a hand sander.

RE Vision, thats what I did. Shaved like 2mm so bracket contacts the sleeve first. Although when torqued to spec there still is some poly bushing rubbing the bracket. Dont think that will affect control arm movement.

Still awaiting a call-back from a MM rep I talked to yesterday. He was awaiting a call back from the supplier... I've been given two separate "2 weeks out", :/ It's close to 3 weeks from the last "2 weeks out".

MM has gotten a physical notation in their system now, where any service member can see an expectation of this month for fulfillment. He's still going to see if his manager can get any firmer detail. It's not exactly a promise, but getting these in for the Peru Tour does not look like an option.

Ha. Glad I'm not the only one. I was told "2 weeks out" over a month ago, and again told "2 weeks out" last week.

[sarcasm]Probably because they’re made in the USA and there’s likely some conservative western white heterosexual christian male privilege conspiracy issue going on ...[/sarcasm]

:rolleyes:
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Careful. There are plenty of people who would actually believe that, and it would make them happily outrageously outraged.