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Discussion Starter · #1 ·
I need these for the FRONT of my MK1.5, so I'm have having some made. See Techno Toy Tuning site for an example of what an RCA is.

These will be machined out of aluminum and be 7/8" thick, with the center locating "knob" in the middle 1/8" high (1.0" overall height). They will not be anodyzed, just raw aluminum. Price will be about $90 for a pair, less if more people are interested, since the machine shop charges much less per piece with larger order numbers. Longer bolts will also be included.

Speak up ASAP if you're interested. I'm taking the order to the shop tomorrow (Thursday) afternoon.

-Jim
 

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I'd try the general MKI forum instead of the suspension forum.. not as many people browse this..

I WOULD get some, but I'm spending all my money on my engine right now..

Brando
 

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I would be interested in a set of front AND rear ones, if that thickness was appropriate for ST springs. I don't think I would want to put them on the front but not the rear. What suspension are you putting them with ? What would the best thickness be for ST springs which lower the car about 1.2 inches ?

John
88 SC, 93T
 

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Discussion Starter · #7 ·
These are 7/8" thick, so it wouldn't put your LCA at the exact stock angle, but it would be a lot closer than nothing. The Japanese "JDM Speed Merchant" that sells these says to use them on the front for "roll balance" and to use front & rear for "absolute performance". See link:

http://www11.ocn.ne.jp/~jdpshop/mr2_3_6.htm
 

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I think useless is a bit strong. Considering that trying to reduce bumpsteer (as shown by brent) is alot of work and isnt cheap, just running a spacer is a cheap and easy way to help.
 

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Bill Strong said:
all I know is that we (Jim and I) are not using MK1 suspensions. We are using MK2 suspensions on our MK1s. This will fix our bump steer issues. which is REALLY bad on our setups
So would these be useful for MKII owners with lowered suspensions?

-Scott
 

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Discussion Starter · #14 ·
To address randedge's question, I must say I do not know. On the one hand Brent found that when he installed the JDM Speed Merchant RCAs (about 1" thick), he saw an increase in bump-steer, which he is trying to eliminate by lowering the mounting point of the steering rack (not a trivial task). On the other hand, these companies (e.g. Cusco, T3, JDM Speed Merchant) have been selling these for MR2s and other cars for years.
If anyone else has any concrete info in this area, please chime in!
 

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Discussion Starter · #15 ·
sab0276 said:
So would these be useful for MKII owners with lowered suspensions?

-Scott
In the link above they sell thicker versions of these for the MK2 as well (MK2 front and MK1 front ball joints are the same), but for the MK2 they say you also need to get a longer(?) steering tie rod end from a MK3 Supra (45460-19225) in order to be able to adjust toe setting properly.
 

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JimKing said:
To address randedge's question, I must say I do not know. On the one hand Brent found that when he installed the JDM Speed Merchant RCAs (about 1" thick), he saw an increase in bump-steer, which he is trying to eliminate by lowering the mounting point of the steering rack (not a trivial task). On the other hand, these companies (e.g. Cusco, T3, JDM Speed Merchant) have been selling these for MR2s and other cars for years.
If anyone else has any concrete info in this area, please chime in!
On a stock-armed MK2, these will create more bump steer. I haven't looked closely enough at the MK1 suspension. A good general rule of thumb is that you want the line between your LCA inboard pivot and ball joint to be parallel to your tie rod, or at least close. Normally you want to move/space your ball joint and outer tie rod the same amount at the same time to maintain this parallel. This is definitely a case where doing half the mod doesn't get you half the result, it can actually be a detriment.

Jim, I might've been interested in these if they were a little taller. But I'm not to the point where I know what height I need to correct my suspension geometry.
 

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Discussion Starter · #17 ·
I believe one of the main reasons for using an RCA on a lowered car is to keep the LCA below horizontal. I.e. the ball joint lower than the inboard pivot point. When this is true, you gain negative camber as the suspension compresses on that side. If you lower a car such that the LCA is now parallel to the ground, then when the suspension compresses, you *lose* negative camber.
On the MK2 I believe the stock ride height has the LCA in this desired orientation (ball joint lower than inboard pivot point). The steering tie rod, interesting enough is at a slight angle upward (from the steering rack to outer pivot point). But... the steering tie rod is about 2" longer than the LCA.

Hmm... I guess I wouldn't recommend getting these unless you check to see what the effect would be on your bump toe change. This is actually not that hard to do. With the car jacked up and wheel removed, I use a cheap 16" carpenter's laser level set against the brake rotor to shine a beam on some masking tape stuck on the wheel well. Use a jack under the ball joint to move the suspension up/down in measured increments, using the laser level to mark toe changes on the tape. Since you're not driving anywhere, you can just use stacks of washers taped together to simulate various thickness RCAs (along with some longer M10x1.25 bolts, of course).
 

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Discussion Starter · #18 ·
Owing to randedge's & Brent's concern about bumpsteer, I will only have a couple sets made... one for myself and one for Bill. The CNC has been programmed, and the parts will be made tomorrow.

-Jim
 

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We do not make RCA's for the MR2 (Techno Toy Tuning) Yet....

We will though and very soon.

Installing ONLY the blocks is NOT an effective fix for the problem on the MR2's 1st or 2nd gen.

On the AE86's because of the specific design, a block is all you need. On the AW11 and SW20 you need to specifically address the issue of the outer steering tie rods. Lowering the Control arm down, while leaving the steering tie rod in it's bound up condition will only increase the problem.

7/8" is probably not going to be enough on a car that is lowered 2-3 inches though. We'll attempt to make them in 1.5" thick or so, with tie rod spacers to match. This will return both the control arm and the steering rack to a more neutral angle and get it out of the "trouble zone" that causes such bad bump steer.

My wife just about wrecked the SW20 on a back road today, so it's time to step up the RND for me! rough back road, bumps, manual rack and 245's in front yanked the steering wheel right out of her hand. 2 counter steers later and she was back on the road.

It's been a serious problem I've know about for a long time. Now I'm finally in gear to fix it.

I need someone with some spare AW11 parts, so I can develop those at the same time. If anyone can help, drop me an e-mail.
 
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