Caster after EPS install?

[Benchwarmer]

Hello,

I have a new to me MK3 Roadster that I am in the process of adding a 520 Speedworks EPS system to. My questions is as follows:


If I was supposed in to increase the caster to match the recommendation for a car with power steering?
If so, I would use control arms to make the adjustment?
The builder did purchase the adjustable upper and lower control arms when he build it.
The car has '94 spindles/knuckles and the EPS system from 520 Speedworks.


Any help would be greatly appreciated on the subject.

[Jeff Kleiner]

Yes, you want 7-8 degrees positive caster. Watch your thread engagement on the forward link of the upper arms; you might need a longer sleeve.

Jeff

[ProfessorB]

I bought a new-to-me Mrk II and it handled very poorly. Like a shopping cart.... VERY twitchy. Some guys on here told me "you just need to learn how to drive a Cobra" but that wasn't the case. The seller, who also owned a Porcshe and a Lamberghini also had the same complaint. Other guys on here suggested it was a lack of proper caster (the car does have power steering). I ordered some turn plates and checked my caster...it was only 4 degrees. I purchased adjustable upper control arms and set the caster at 8 degrees as recommended. As already mentioned, you DO have to make sure there is sufficient thread engagement. I ALSO went to a slower ratio power steering rack. The GT rack is quicker steering...the four cylinder rack has a slower ratio. The car was TRANSFORMED. While I do think increasing caster has a greater effect I do think the rack change helped a little....

[Benchwarmer]

I bought a new-to-me MRK II and it handled very poorly. Like a shopping cart.... VERY twitchy. Other guys on here suggested it was a lack of proper caster (the car does have power steering). I ordered some turn plates and checked my caster...it was only 4 degrees. I purchased adjustable upper control arms and set the caster at 8 degrees as recommended. As already mentioned, you DO have to make sure there is sufficient thread engagement. The car was TRANSFORMED. While I do think increasing caster has a greater effect I do think the rack change helped a little....

Yes sir. I completely understand about thread engagement and yes I would call the car twitchy as well. I pulled the rack off to install the rack centering bushings from Breeze Automotive and I found the driver's side tie rod only had 2.5 turns of threads on the driver's side. The rack also wasn't centered on the "turns" of the steering either. No cotter pins on the tie rods either. Ordered the correct tie rods and ready to adjust everything. Is there a layman's way of measuring caster? I do have access to a set of turn plates. Is that what I need?

[ProfessorB]

Yes sir. I completely understand about thread engagement and yes I would call the car twitchy as well. I pulled the rack off to install the rack centering bushings from Breeze Automotive and I found the driver's side tie rod only had 2.5 turns of threads on the driver's side. The rack also wasn't centered on the "turns" of the steering either. No cotter pins on the tie rods either. Ordered the correct tie rods and ready to adjust everything. Is there a layman's way of measuring caster? I do have access to a set of turn plates. Is that what I need?

.
I had never done it before, but was able to after warching some Youtube vids and with the help of people on here. I used both the turn plates AND a camber/caster gauge. The turn plates will tell you exactly how many degrees (left and right from straight ahead) you have turned the front wheels, and the caster gauge will give you a the reading. I believe complete directions on this procedure came with my caster gauge. That same gauge will also tell you your camber, which I set at .5 degrees negative. (Ever so slightly tilted "in" at the top)

[edwardb]

Just for clarification, it's not just a matter of adjusting the caster from whatever it is now to the 7-8 degrees for power steering. Almost for sure the other settings (camber and toe) will change when the caster is changed. So all three need to be checked and set to spec.

[Mike.Bray]

^^^what Paul said^^^

[ProfessorB]

Yes sir. I completely understand about thread engagement and yes I would call the car twitchy as well. I pulled the rack off to install the rack centering bushings from Breeze Automotive and I found the driver's side tie rod only had 2.5 turns of threads on the driver's side. The rack also wasn't centered on the "turns" of the steering either. No cotter pins on the tie rods either. Ordered the correct tie rods and ready to adjust everything. Is there a layman's way of measuring caster? I do have access to a set of turn plates. Is that what I need?
.
.
I went out to the shop last night and dug out my gauge. It's called "Fastrax Camber Caster Gauge". I bought it upon advice I received here, and it comes with an instruction sheet. Very happy with it.

[CraigS]

You don't have to have turn plates. They make the effort to go to 20deg easier but a plastic trash bag can help w/ that. I used to just do this.
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[ProfessorB]

You don't have to have turn plates. They make the effort to go to 20deg easier but a plastic trash bag can help w/ that. I used to just do this.
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Yes, and a couple of waxed floor tiles will also do the trick.

[Benchwarmer]

Just for clarification, it's not just a matter of adjusting the caster from whatever it is now to the 7-8 degrees for power steering. Almost for sure the other settings (camber and toe) will change when the caster is changed. So all three need to be checked and set to spec.

Yes sir!

[edwardb]

You don't have to have turn plates. They make the effort to go to 20deg easier but a plastic trash bag can help w/ that. I used to just do this.



Yes, and a couple of waxed floor tiles will also do the trick.

Don't disagree. There are various methods to allow the front wheels to turn when setting caster. I did the trash bag thing for a few years and it certainly works. The challenge I had was finding and accurately setting the turn degrees. 20 degrees each way is common. The Longacre digital caster/camber tool I use now is 15 degrees. I tried several ways to measure or visually see the angles while using the trash bags but it's not easy. The turn plates have an angle readout so you can set the angle accurately. My take is the trash back (or whatever) is fine for getting the alignment in a reasonable range and then have it finalized at a shop. If you want to do the alignment yourself without taking to a shop, then the proper tools including turn plates become more important. With turn plates and the already mentioned Longacre digital gauge (versus the commonly used and much cheaper FasTrax that some use) I do the finished alignments myself. The cost maybe makes sense if you're doing multiple alignments. Probably not so much for a single build.

[CraigS]

This is my upgrade. Similar to edwardB's but a bubble vs digital.
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Then I got rid of the bungee replacing it with this.
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Then I added these w/ mounting tape to make the angle more easily visible.
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Currently I have a setup for both sides but the point is that you don't need to start out w/ a full blown expensive set of tools. I did one side at a time for several years w/ my piece of plywood. The thing about caster, especially combined w/ camber, is that you will be measuring it and adjusting it anywhere from 3-6 times before you get what you want. So any small inaccuracy gets whittled down w/ each repeat. I get to where I think I have it, and then do at least one, and usually two, additional caster sweeps to confirm.

[rich grsc]

For $70-100, it's just not worth my time & effort. We have a performance shop here that is quick and very good, he does setup on track cars, so knows what works. Made a big difference on mine. Maybe just search around your area?

[Mike.Bray]

Don't disagree. There are various methods to allow the front wheels to turn when setting caster. I did the trash bag thing for a few years and it certainly works. The challenge I had was finding and accurately setting the turn degrees. 20 degrees each way is common. The Longacre digital caster/camber tool I use now is 15 degrees. I tried several ways to measure or visually see the angles while using the trash bags but it's not easy. The turn plates have an angle readout so you can set the angle accurately. My take is the trash back (or whatever) is fine for getting the alignment in a reasonable range and then have it finalized at a shop. If you want to do the alignment yourself without taking to a shop, then the proper tools including turn plates become more important. With turn plates and the already mentioned Longacre digital gauge (versus the commonly used and much cheaper FasTrax that some use) I do the finished alignments myself. The cost maybe makes sense if you're doing multiple alignments. Probably not so much for a single build.

Agree 100% with this.

I have all of the tools including the turn plates and did my alignment. Car drives great, tracks straight, and I'm very pleased with it. My alignment tools have kind of become the DFW community tools, so far they've been used on 5 Factory Five cars in the area. Now I just have to remember who has them.....

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