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hm, when I think more about it looks like whiteline UCA bushings would add more static negative camber, however as suspension compress eccentric sleeve rotates and you actually loose some camber unless you set its resting position so it achieves max negative camber as UCA moves to the upper most position when suspension is compressed - essentially helping you with camber gain under compression rather then with static camber. maybe installing them to help with camber gain is more preferred for track use as suspension is mostly compressed when you need most negative camber - in corners?
On the other side eccentric bushings with regular sleeve would keep the negative camber gain permanent in resting and in compressed suspension position, but then there is an issue of keeping them in place like you mentioned.
does this make any sense to you guys?
Last edited by Nadrealista; 04-14-2017 at 02:48 PM.
That post is from October 2016 - I didn't see anything on their website for an rx8 or a Miata. Haven't driven with my new alignment settings yet, but if i need further neg camber, will look into this - though I'm also trying to figure out what sort of nasa classing the car falls into before I do anything additional =P
On the MM parts store page, click competiton parts link, change vehicle pull down menu to RX8 and then submit, it will pull up most of the RX8 comp parts and the bushings are listed there; about $86 as I recall
So cheaper than the speedsource and other company that duplicated the ss design, but not nearly as good IMO because they don't have the inner sleeve and also have to glued and pinned as a result. It will basically still work though. The earlier designs were't offset though. I had several sets modified to achieve the same thing with the offset in the sleeve though.
Hey guys, I have the whiteline eccentric UCA bushings. The metal sleeve is wider than the poly bushing, and when you torque the upper bolt it is locked in place (pinched by the frame pieces). the poly bushing rotates around the static inner sleeve. This is nice because then you can torque the upper bolt at full droop and it does not bind like the stock bushing.
Being able to torque it at full droop is not a good reason to make that choice. Just out of curiosity, what limits it from moving side-side as easily as it does about the axis?
The OE bushing has that characteristic, but it's accounted for in the overall suspension design and compressing the suspension to torque is no bfd. Poly moves around more than the OE bushing, especially in time, because the OE RX8 design is superior in minimizing defection even though it has softer rubber. Recommend in this order; new OE, sleeved Delrin, spherical. Poly should be avoided imo ... but 10+ years later it still gets ignored
If you cut or burn apart that same OE bushing you'll find that it actually has a lot of metal hidden inside to limit deflection. At least the non-sleeved delrin bushing is cheap enough that you can swap them out without a big hit. The general issue is that most people throw in poly etc and then just forget about ever doing anything more likely like they're a lifetime product. Not so ... same for spherical, most people let them get too sloppy due to the high replacement cost. Sleeved delrin have the longest service with good maintenance lubing if you can find or make them, but they only work in single axis rotation. Multi-axis rotation should stick with OE or spherical. Well that's my sermon for the day ...
I spent some time with Ryan at MER Friday afternoon, once it was too hot to be on the track, and he showed me how they are getting extra camber in RX-8s. Apparently, MMD sells an aluminum offset bushing for the lower control arm upright that introduces at least 1.5* of negative camber, similarly to the way offset ball joints work in NA and NB Miatas. Installation is not trivial, and he quoted me around $500 for the job. He had an RX-8 up in the air with them installed, so I was able to check it out. Should work, and should be solid. I doubt I will do it at this point in my RX-8 ownership, but I wish I had known about it 3 years ago.
I'll ask him for the part number, if anyone is interested.
OK. I didn't realize that thread was talking about the lower upright. I was thinking the LCA bushings, but looking at how the LCA bushings are oriented, offset bushings wouldn't work, so the upright is the only candidate.
If I found the right part number on MMD's web site, they do show to be NLA. BUT... Ryan produced a pair from his mailbox Friday afternoon and said he got them from MMD, so...
(Maybe I should run in there and buy them Saturday, when I am back at the track.)
OK. I didn't realize that thread was talking about the lower upright. I was thinking the LCA bushings, but looking at how the LCA bushings are oriented, offset bushings wouldn't work, so the upright is the only candidate.
If I found the right part number on MMD's web site, they do show to be NLA. BUT... Ryan produced a pair from his mailbox Friday afternoon and said he got them from MMD, so...
(Maybe I should run in there and buy them Saturday, when I am back at the track.)
I'll ask him what he knows about it.
I think there are a few people that would like them...so if you find out anything let us know
I've modified several sets of the SpeedSource front UCA delrin bushings to be offset and could probably get you a set made. The bushings Motorsport sells now aren't as desirable imo as previously discussed earlier in the thread.
I think there are a few people that would like them...so if you find out anything let us know
He emailed me the part number this afternoon. It is 0000-04-5407. That part comes up for the MX-5, but the diameter is the same, so it works for RX-8s.
ive also searched the web and i do own a state of the art 4 wheel alignment bench. However racecar suspension geometry is quite a different ballgame frome ordinary road going cars.
My measurments shows 11 degrees of build in KPI in the rx8 spindels. ｴhowever the stock suspension wich im only allowed to use in my racing class only allows for 7 degrees of caster, wich bassicly means that to not get negativ camber on turns, the camber should be well over 3 degrees and that is not good for braking. And at a stock height t7 degrees of caster and 3,5 degrees of camber isnt doable. That is why im planning on fabricating a set of bushing for the supper and lower controlarm wich will enable 10 degrees of caster and try running 1 degrees of static camber.
Has anyone else tried this on theese cars ?
Hadn't ever heard of anyone trying it. You'll need to verify that the spindle ball joints can handle that much angle through their full range of suspension motion. I'd think it also be pretty tricky to get all the bushings to be bind-free without them all being converted to spherical bearings.
I just made these yesterday . They ADD 2' OFF caster and no binding ore messed up Angles . I'm at 9,5 degrees now and aiming at the 11 mark. That should make the camber 0 at 30 degrees steering angles. If it works at the race this Sunday I'm making a set for the lower arm to
Well I thought you intended to more than just the fore-aft positioning to maximize the effect. I use 2.25" diameter springs (57.2mm OD) and don't think my coilovers would clear the upper arm with that much repositioning, but maybe my memory is off.
I use the same sixe springs i will have an alignment result tomorrow. However i do not know what spring rates i should use. Mine is bonestock Bilsteins right now but they are way to soft. do you have any recomendations? Im rallying my car however its a tarmac only rallycar.
so I am curious does this hold correct for our cars in track enviroment. he is making argument that static caster is more important than static camber. in another words you would try to go with max caster you can get instead of putting premium on max negative camber since it is the caster that gives you more dynimic camber under cornering and compressed suspension by giving more negative camber to the outside wheel and removing negative camber from the inside wheel?
does anyone know what is factory KPI/SAI spindle angle for RX8?
Camber Gain
On the outside tire, if you worked out your camber gain to be 1.5 degrees negative “in dive” … and assuming we have a modern low roll angle suspension with chassis/body roll angle of 1.5 degrees … those two just neutralized each other. The inside tire, of this car in the same corner, is compressed, but not as far, so it doesn’t have as much camber gain towards negative (reminder: camber gain towards negative is bad on the inside tire).
Let’s say we end up with 2/3 the compression travel on the inside tire & end up with 1.0 degrees negative camber gain (the bad direction for the inside tire) … so what does that do for us at this level of “onion peeling”?
Dynamically we have:
Outside Front Tire 0.0 degrees (OK)
Inside Front Tire +0.17 degrees (OK)
Not optimum yet, but we’re going the right direction & we’re not done yet.
The next layer of the onion is static camber.
You need SOME static camber … to help with initial steering turn-in responsiveness. Just don’t get greedy. In road racing or AutoX where you’re turning left & right, static camber is like camber gain. It helps the contact patch on the outside tire & hurts on the inside tire. For this example, let’s add 1.0 degrees of static camber.
Now with static camber added … with your car hard in the corner … suspension in dive, wheel turned 15 degrees for a tight corner …
Dynamically we have:
Outside Front Tire -1.0 degrees (Good)
Inside Front Tire -0.83 degrees (Bad)
Not optimum yet, but we’re we’re not done yet.
[b]Now, here is another part I love. You simply add caster until the contact patches of both tires are flat & happy. And from this point the math is easy.
Add 1.0 degree of caster and …
Outside Front Tire -2.0 degrees (Good)
Inside Front Tire +0.17 degrees (Good)
Add 1.25 degree of caster and …
Outside Front Tire -2.25 degrees (Very Good)
Inside Front Tire +0.42 degrees (Very Good)
Add 1.5 degree of caster and …
Outside Front Tire -2.5 degrees (Very Good)
Inside Front Tire +0.67 degrees (Very Good)
There are many factors that will define your optimum set-up, but this creates a baseline that is darn close.
**P.S. I like to end up “around” 1.5-3 degrees more dynamic camber on the outside tire, since the outside tire is loaded so much more. This varies with tire grip (think TW200 versus Slicks) and with sidewall height, design and rim width.
Last edited by Nadrealista; 08-31-2017 at 05:08 AM.
according to the service manual SAI for RX-8 is 11 degrees :-(, while max caster is around 7 degrees. far from optimal according to Ron's theory from my previos post which favors having 1-2 degree more caster than SAI for best dynamic camber gain.
in that scenario he suggested getting most static negative camber to make the outside front tire work.
D. If I can get the caster I want ... statically and/or with gain ... so the KPI/Caster Split favors the caster at least 1.0+ ... I can run less Camber, which is the goal. We're always going to run SOME static camber (negative) … say –0.5 at a MINIMUM … and we always want SOME Camber gain … but if we don’t end up with a KPI/Caster Split favoring the Caster by 1.0+ degrees … then we need to make the difference with Static Camber & Camber Gain.
This is NOT ideal, because Camber by itself helps the angle of the outer tire achieve optimum contact patch … and hurts the angle of the inner tire, preventing optimum contact patch. The more static camber & dynamic camber we have to run … to make the outer tire work best … the more it hurts the contact patch of the inner tire.
If we can get to the optimum angle with a KPI/Caster split favoring the caster by 1.0-3.0 degrees … either statically or in dive … we will run smaller amounts of static camber & camber gain. This is optimum. But if we don’t … we’ll run all the camber we need to … to make that outer tire WORK.
My memory is off because I looked at it the other day when I went by the shop and my adj. perch and spring are above the UCA. I've been running minimum caster since back in the Stock racing class days (around +3 deg as I recall) because that provides the maximum static camber. After converting the Speedsource delrin UCA bushings to be offset I can get over -3 deg up front now. I haven't really messed with trying more caster because the biggest issue for me when everything else is in tip top shape is rear end grip. About the only time I have front grip issues is if something else caused it like a blown shock, etc.
The kind of caster numbers and extreme positions your talking about here make me wonder about causing other issues like bump steer. Unless you map out the chassis in detail and mock it up with a serious suspension program it seems to me you don't really have any idea what the full result of these changes are going to be beyond the one small part of the puzzle you're focused on. Front grip isn't likely to be the issue in my own experience. Others may disagree though ... plus I never think of the inside front tire having enough, if any, weight force on the contact patch to matter. I have a few pictures where it's off the ground on my car. The camber angle is not really relevant then, lol
You can still get a lot of unique parts from Japan too if you know where to look, here is one example; they claim -4 deg camber and +8.5 deg caster with their front LCA spherical bearing kit
Yen price works out to $225 for lca camber bushing pair and $275 for the lca caster bushing pair. (3rd one down from the top)
Another USA source for rear arms/toe links with spherical bearings and inline adjusters. They also have camber/toe lock out plates & bolts to prevent cam-adjuster slippage because they aren't needed with the adjuster on the arm
04-14-2017, 02:43 PM
