MR2 SpyderChat banner

1 - 20 of 34 Posts

·
Registered
Joined
·
8 Posts
Discussion Starter #1
What is everyone doing for RCA and bumpsteer correction? I am surprised that there is absolutely no aftermarket support/products for RCA and bumpsteer correction. I am also surprised that few people have talked about this. I am sure with RCA and bumpsteer correction tie rods, it will make the car much more enjoyable for our lowered cars, especially for daily driving. There are also a lot of performance gains from them.
 

·
Registered
Joined
·
162 Posts
I think most here just deal with it by adjusting toe accordingly and using polyurethane bushing to reduce slop. I just read a couple of suspension books a few weeks ago, but I've forgotten already, what geometry needs to change to eliminate rear bumpsteer?
 

·
Registered
Joined
·
84 Posts
I believe I'm using an S13 bump steer kit. Researched miata and other forums for awhile to find the correct thread pitch. It's a direct bolt on with no mods. 1/32" bump steer from full droop to full compression after adjusting.

Do not lower your car if you don't understand roll center geometry vs cg. There's a reason people need 12k front springs and -5° camber after lowering.

Take measurements of your suspension geometry, figure out how much suspension travel before lca's are horizontal. If you do lower then look for moonface super lap lbj's.

A good comparison are the e36's and e46's we race against. Their stock suspension geometry is terrible. They need significant mods front and rear to even be decent. Otherwise e36/e46 need to be raised from factory ride height for proper geometry.
 

·
Registered
Joined
·
8 Posts
Discussion Starter #5
I believe I'm using an S13 bump steer kit. Researched miata and other forums for awhile to find the correct thread pitch. It's a direct bolt on with no mods. 1/32" bump steer from full droop to full compression after adjusting.
does the s13 tie rod bumpsteer kits really work? I’ve been looking at tf-works tie rod bumpsteer kit.

If you do lower then look for moonface super lap lbj's.
I believe it’d be hard to find moon face lowerball joints due to it be discontinued? Does it correct enough roll center? I just want to lower the car a bit. I’m hoping it’d be enough. I’ve been looking at hardrace lower ball joints to correct roll center too. Any thoughts on these?
 

·
Registered
Joined
·
84 Posts
My numbers are measured bump from full droop to full compression at the front and rear of the rotor, not a guess. It's on my car as a direct bolt-on. I didn't weld it. So, it likely does work as a direct bolt-on as stated.

I have not researched the Hardrace lbj's. You need to measure to determine your rc. It's not difficult. I run 245-15 square setup without any tracking or bump issues.

I typically buy parts from JP companies and websites. As for any non-OEM bj for any car, you have to be careful of ones made in China for two reasons. Often times they use low cost cheap metals to save money.

The second issue is they make the bj an interference fit. Companies selling these parts say this is fine and they will "break in". BJ's are designed with a specific breakaway torque which is very low. There should not be any metal-to-metal contact internally. If you cannot move it with two fingers it's already destroyed. The end result will be a seized bj (which poorly manufactured ones technically are already) while driving which breaks at the location where the bj is not supported by the lca. I have seen this many times before.
 

·
Registered
Joined
·
84 Posts
Yes. I run 15x8 square setup with 245's. Going to pick up 15x9's soon.

I haven't modified the lower part because I'm still tuning suspension and haven't decided if I want to try the Hardrace lbj's. If I do, I wanted to make sure I still have bump steer adjustability.
 

·
Registered
Joined
·
84 Posts
At this point I'm just going to have a friend CNC drop spindles later. I'm not going to run RCA by extending joints. It will break the way I use it. Bumpsteer really not an issue imo.
 

·
Registered
Joined
·
84 Posts
Bump steer on these cars is an issue. It's not an opinion.

I road race, sprint and enduros.

Have seen cheap rc bj's seize and snap on BMW's from big name companies. Cheap metallurgy causes many parts to fail. If you can afford it a drop spindle is a better option.
 

·
Registered
Joined
·
84 Posts
I mean, that's nice, but I am not finding an issue on my car at this time. Lots of hours on it so far with aero, 9's & 10's & AR-1's at many different west coast tracks. I have swapped out the stock inner rods for SC430's and adapted Battle Version parts for the outers, but have not done any bumpsteer correction.

I will revisit when I K swap and see what needs to happen, if anything.
 

·
Registered
Joined
·
84 Posts
That's one big difference. You run different inners and outers. I depowered the rack and set up with the stock tie rods.

Kswap won't affect suspension geometry, but you will have to cut/notch the right rear brace to fit around the Honda pan. Pretty easy.

We run NASA, so same tracks - Laguna, Thill, Sonoma, Llihrednuht, BW, and UMC
 

·
Registered
Joined
·
84 Posts
Yeah I wasn't saying that geometry would be affected, just that with the power add I will be pushing the car harder and using more of the suspension. The depowered rack likely amplifies whatever bumpsteer issues, but I don't plan on doing that at this moment.

While stock power has been a snooze thus far, it's actually surprising how fast it is at the local tracks.

When I get the drop spindles made I may look into having a run done. We can engineer whatever bumpsteer into them as well.
 

·
Registered
Joined
·
84 Posts
If you don't mind, keep me updated on the drop spindle testing. I have ride height set for ~1.75" of compression with camber gain. I'd like to go lower, but strut.

I switched to BC ER shocks from the BR? singles. From testing it was obvious immediately they need to be revalved for much more rebound, less bump, and lower viscosity oil.

If you kswap, I'd highly suggest a frank. Though the k20 pulls great (especially with my custom intake), the torque will make a big difference.
 

·
Registered
Joined
·
84 Posts
I have BC singles with different oil. Work great.

Going RBB-3 or 4 K24A2, with that don't need the K20 head. Might build it a little, might not. Dunno.
 

·
Registered
Joined
·
84 Posts
Which shock oil and viscosity did you go with?

From the limited info I got talking with BC they use a 12W but wouldn't mention brand. Comparing charts of shock oil, that would generally be around 40 cst @ 40°C, but I think theirs may be higher.
 

·
Registered
Joined
·
159 Posts
S13 bump steer kit bolted on direct swap.
i'm quite happy to know that you managed to get an s13 kit to fit up.

i was looking at the outer tierods for s13 and noticed that the taper angles were a bit different, but by what you've said, the taper angles aren't so different as to cause steering issues?

bit of a threadjack:
I've been itching to widen the front trackwidth so i can eliminate scrub on my fronts (which is why i was looking into S13 outer tierods)
Do you happen to have any info on how far the steering rack will continue to travel without damage if the inner tie rods aren't screwed in? I have some inner rack spacers with some amount of additional travel built in to try to gain a tiny bit of lock but i don't want to bottom out the rack before the spacers themselves bottom out on the ends of the rack housing. i'm hoping i won't need to add additional bump stops onto the rack spacers
 

·
Registered
Joined
·
84 Posts
@refirendum

It was one of the first mods I did and don't remember. My focus at that time while the kswap was in process was to properly convert the rack by removing the piston. I didn't even focus on suspension geometry until later once I worked all the kswap wiring bugs out.

@tony_r

The Penske 3W is 13.7cst @40°C. I was figuring below 20cst would be good because the car weighs <1950 with <900 over the front axle.

Most shocks seem to be valved for 3000-3500lb cars.
 
1 - 20 of 34 Posts
Top