Kevin Doe

iTrader: (1)

In the quest for more front camber, I needed to do something custom. I asked around and everyone uses some $777.46 upper arms imported from Japan. They use heim joints and as such you can adjust the length of the arm. Only problem with that solution is that they're insanely expensive and hard to get. So, I designed an entire upper arm, made engineering drawings to have parts made, but never pulled the trigger. I just let the idea simmer for a while. There are only two ways to gain more camber, shorten the upper arm, or lengthen the lower arm. There are pros and cons with each method, which I won't really get into.

I had a few options.

1. Make custom front upper arms.
2. Make custom front lower arms. Since the shock and sway bar mount to this, it would be very difficult, and certainly not the easiest option.
3. Modify the lower cam bolt slots. I could remove the cam bolt retainer "U" and move it outboard a little bit, and slot the mounting holes more. Seems easy enough.
4. Make eccentric lower bushings. (not an eccentric pin, I don't like those)
5. Make eccentric upper bushings. (not an eccentric pin, I don't like those)

I ended up going with option 5 for a variety of reasons, but here are the main considerations. In most race classes, you are allowed to modify any suspension components, but not the mounting points. If I modified the sub-frame cam bolt area, that would constitute modifying the mounting points. The reason I don't like eccentric center pins is because they can be a pain during alignments, and they can move during hard cornering with sticky tires. By offsetting the busing, this can't happen.

So, with these bushings the hole for the pin is offset by 0.125". This will effectively shorten the control arm by that amount. You will still have the same adjust-ability as stock, the range will just be offset by ~0.7 degrees more negative. I also took the opportunity to offset the upper control arm rearward by 0.125" as well. This will offset the stock caster range by ~0.7 degrees as well.

Here is the first prototype run. These are made of black Delrin. I will be test fitting in the next week or so, and aligning soon after. Once I get these on my car and aligned, I will remove my coilover spring and check for clearance between the shock/control arm. These are made to press into the control arm, and when you do you'll have to be mindful to install them in the correction orientation. The center hole should be closer to the ball joint end of the control arm. The thick flanged bushings will go in the front locations, and the thin flanged bushings will go in the rear locations. I also plan on drilling a small hole through the control arm and into the Delrin. Then I'll install a small screw (something like M4 or smaller), just enough to ensure that the bushing can't re-clock itself. I think the friction from the press fit should be enough, but I may do this anyhow. These also include a lubrication groove, for use with a grease zerk fitting installation (which I already have done to mine, since I used Delrin bushings previously).

If all goes well, I'm going to have a run of these made up and offer them up as an alternative to the expensive upper arms.

Now for some pics:

Kevin Doe

iTrader: (1)

I forgot to subscribe to this thread, so I'm making another post to do so.

jkstill

iTrader: (11)

I would definitely be interested in set of those.
Much less $$ than replacing the arms.

gracer7-rx7

iTrader: (16)

Nice job as always Kevin.

Superpro used to offer a similar option for the rear, upper arm

A few of the more serious autox guys on the forum (AMRX7 and Strelniaks) have gone the route of the custom upper arm.

to_slow

iTrader: (3)

Here is another option for a more hard core autox/racer

Kevin Doe

iTrader: (1)

I'm well aware that those custom arms are available, although they are very expensive. Plus they both net the same result, but my method is at a significantly lower cost.

to_slow

iTrader: (3)

Very true... cost wise, your option is better.

gnx7

iTrader: (10)

We are having a set of custom lower front A-arms made in the next few weeks as Mazda is essentially running out of front replacements. The tie rod/ball joint is not replaceable on the factory arms.... Most above 100K miles are pretty worn out.

This is an interesting option for the uppers.

What is your current front neg camber? What are you looking to run with these?

Bill at LPI Racing seems to be fine with the current allowed camber running stock A-arms. He will be testing the new custom lowers we are developing.

I'm no mechanical engineer so just wondering why you need more camber.
Are your tires temps not even?

Kevin Doe

iTrader: (1)

My previous max front camber was ~2.5-2.6 degrees depending on where I had the ride height. I'm hoping these bushings will help me gain 0.7 degrees, and get me to -3.2. I really would be happy with 3, so we'll see. I installed the bushings over the weekend and will be aligning it this week. I'll let you and everyone else know what it all came out to.

More camber for even wear and more grip.

Kevin Doe

iTrader: (1)

Version 1 of my offset/offset front UCA bushings installed. Version two in the works this week, I had to make some minor changes before these bad boys are ready for production.


Small M5 bolt holding it from reclocking, or moving.


The tweaks for version 2 include:
- 0.002" larger center bore. The center bore shrunk too much when pressed in.
- 2 degree tapers on each end to limit bushing friction on the body mounts.
- 0.030" more thickness on the flanges, while keeping the same overall part height.
- Alignment mark for ease of installation.
- 1/32" - 1/16" more camber offset. Not sure yet, need to take more measurements today.

FYI - I aligned my car yesterday and was able to get a max of -3.1 degrees of camber at a ride height of 25" (with 285/30/18 A6). I'd like to have more adjustably range for suspension test/tune purposes, so I'll likely go with a setup that has a max of 3.4 degrees or so.

yzf-r1

iTrader: (1)

I believe they also sell them for the front, in the "Alignment" kit

RXtacy

iTrader: (7)

yes they have them for both the front and the rear. As yzf said you can get them in the alignment kit or individually. These are the part numbers for the eccentric bushings.

Front of car
SPF2821Kx1 – Front Upper control arm (4)
SPF2822Kx1 – Lower control arm Front (2)
SPF2823Kx1 – Lower control arm Rear (2)

Rear of car
SPF2679Kx1 – Upper control arm (4)

Link to their catalog.
http://203.31.191.243/fulcrumCat/

Kevin Doe

iTrader: (1)

I'd be a bit afraid that eccentric pin would slip and change alignment in high G corners (which is why I didn't go with an eccentric pin). I had no idea these were available though.

Kevin Doe

iTrader: (1)

Here is version 2 installed. They now features 3/16" offset. I was able to get -3.25 degrees of camber at a ride height of 25" with these. Not sure on caster yet, I'll post up when I get more info on that. My home/track alignment setup can't measure caster (yet).

mefarri

iTrader: (2)

Kevin,

You really think the eccentric pin could move if torqued properly?

Kevin Doe

iTrader: (1)

I suppose it could. Plus they're a pain in the *** when aligning the car, and if you remove the arm and put it back on, its alignment time. For me, I can remove and install the upper arm and retain the same alignment time after time. Plus its one less thing to worry about.

KJK

iTrader: (1)

This is exactly the sort of thread I have been searching for, and my question pertains greatly to the topic at hand.

I have been planning to run as close to 9 degrees of caster as I can in combination with a minimum of -3 degrees of camber. (Any caster number sub 8.25 would be unacceptable). I know the ideal numbers are around 6/7, but the higher figures better suit my needs.

I've found a Super Now - Super Caster pillow ball bearing set (Can't post links yet, but they're on rhdjapan.com). However, even with a good alignment, I am almost positive that they aren't going to do much by themselves.

How should I go about achieving this degree of caster? I am open to all options, the more the better. I would like to stay under $1,500 if possible, but I am really open to anything.

jkstill

iTrader: (11)

Still planning a group buy?

Cuz I want a set.

Kevin Doe

iTrader: (1)

I dunno, post a thread about it. These bushings will not get you 9 degrees, or even close to it.




Not really. I'll post up my technical drawings for all to copy if anyone wants. I decided I'm not interested in dealing with potential liability of suspension parts. For what its worth, it takes about $15 in delrin, and $60 in machine shop time to make a set of these.

jkstill

iTrader: (11)

Works for me.

habu2

What are your needs that you require so much caster? Are you trying to make your car steer itself on long straight interstates?

KJK

iTrader: (1)

Sliding. I used to have a miata with minimal caster and it was great fun to drive, but when you went to flick it sideways you'd be walking the wheel to countersteer, which isn't very fun or ideal. You want to be able to initiate the slide and have the wheel spin through your hands (Like my old E30). Caster is how you get this, and the more the better (to a certain degree, I mean you gotta be able to steer the thing!).

Anymore advice on how I would get to around 9 degrees of caster? I'm afraid that if I start a new thread it won't be taken seriously because my objective is so abnormal.

mopar97

iTrader: (7)

i know exactly what you mean, same here with my FD when i go out and drift it i want that damn wheel to snap back like my s13/s14's used to do. You want to only worry about corrective steering not counter steering.

jkstill

iTrader: (11)

Kevin, can you share the drawings?

I would like to get a set of these made.

AMRX7

I have some bushings like these for the lower control arms and they worked fine for years. As mentioned I had upper a-arms fabbed since I wanted them adjustable. One thing to bear in mind when doing the uppers is wheel clearance. The Japanese arms shown would likely have issues with large backspace wheels on the rear side of the arm.

-Andy M.