Suspension Alignment questions

[Seymour Snerd]

A few random questions arising from doing a rought alignment:

1. The two skinny locknuts on either side of the threads on the front upper ball joint (aka rod end). Anyone have a suggestion for a wrench to use on those? I measure them as about 32.5 mm which corresponds to no metric or English hex size I've ever seen (1-9/32"!). The only thing that springs to my mind is to get a cheap 33 mm open-end and cut off most of it.
2. Also, does anyone happen to know the thread pitch there, and of the tie rod ends? I ask just because there are not enough threads exposed for me to easily measure, and it would be nice to know how much each nut turn moves things.
3. Finally, there's this two-page document I have called "Gt40 Chassis Alignment Info" that calls for 1/8" toe-out at both ends for street use. a) Anyone know the source of that document? It says the author is "Mike" but no company is mentioned. b) Theory aside, has anyone actually tried those alignment settings? c) Also, why would you think they call for 16 PSI front, 18 psi rear? Trying to muffle the heim joint suspension? To help disguise the crazy toe settings? :idea:

 

[Seymour Snerd]

Anyone have a suggestion for a wrench to use on those? I measure them as about 32.5 mm which corresponds to no metric or English hex size I've ever seen (1-9/32"!).

A few minutes later: Good old ebay: there's a 1-5/16" crows-foot for $8!

 

[Jim Cowden]

Toe out on the rear would make it interesting.

I have found other peoples wheel align specs are worth s**t.

On my car toe out on the front sharpens the turn in to the apex as it is giving more toe out on turn.
Having said that I have parallel steer steering arms.

Toe settings depend on bump steer, ackerman, anti ackerman and can be used to compinsate for other issues.

I think you would be better of having a play.
Your tyre choice will change settings.

Jim

 

[Jack Houpe]

I found the painted marks that SPF provided to be very good start, I made many changes in my car and it didn't handle well at 135 MPH, took it to an expert with a drive on alignment machine, he set to specs that SPF recommended and the paint marks all lined back up again. I've had it to 165 and its solid as a rock. Most of my driving is on the street but I have done 3 open road races with it and at 110 mph in a corner it feels great. So my vote is leave the to the specs they recommend and set at the factory, at least on my car they did and all of my friends cars are marked.

 

[Randy V]

Toe out on the rear would make it interesting.

I have found other peoples wheel align specs are worth s**t.

Jim

Interesting is putting it mildly... On a car at is tail happy under power, you'd find yourself backwards quickly coming off of almost any corner..

Alignment specs are highly subjective and numerous factors all come into play. At best, you can use proven specs for a given combination as a baseline and then fine-tune for that particular car..

 

[Rick Muck- Mark IV]

Quite a few mid engined race cars use some "toe out" at the rear to improve turn-in. It does make high speed straight line stability tougher, but it is common.

 

[Cliff Beer]

Alan, some interesting questions.

On 1., you could always use a large ford wrench. If you can get on it squarely then a ford wrench works well and a lot of force can be applied (same as a ring spanner) due to same geometry as a pipe wrench.

On 3., I asked this same question a while back here and got some good recommendations for baseline setting for street driving. Essentially, I averaged out the recommended settings and ended up with basically this: 1/8 toe in front, 1/8 toe in rear, 1 degree negative camber rear, .5 degree negative camber front, 4-5 degrees caster front, zero caster rear.

I took the car to a very well respected race shop in Seattle here (Group 2 Motorsports) who are very experienced with alignment setting on high performance cars (and who also have the proper equipment) and they agreed the above would be good street alignment settings for a GT40 so that's what was done. The car (a CAV) drives beautifully with those settings. I haven't had it up to speed like Jack has so I can't comment on what it's like above about a 110mph, but below that it's very docile and has no bad habits. Of course, what works on one car may not work on another, and I imagine the SPF guys know pretty well what works on their cars....

 

[Seymour Snerd]

Quite a few mid engined race cars use some "toe out" at the rear to improve turn-in. It does make high speed straight line stability tougher, but it is common.

I wasn't quite so shocked about the rear since my old NSX had a similar spec. But at the front?

 

[Seymour Snerd]

I imagine the SPF guys know pretty well what works on their cars....

I suppose, although the SPF User manual specifies more conventional 1/8" toe-IN and higher pressures. So this gets to question 3A: who wrote that doc? Is it even from Superformance?

 

[Jim Craik]

Alan,

I'm not exactly sure what settings "Full Throttle" (who did my install) used but I have to say that they are perfect!

They spent a fair amount of time on set up and as you know, I am only using mine for the street, but that said, I got 30,000+ miles on my first set of Avons. The best part, they wore absolutly even, front, rear, inside of tire, outside of tire, all four wore exactly even! I could not believe it.

I imagine they used the SPF settings, but you might ask Dennis what specks they used or you can call Full Throttle in Reno (775) 852-0800 ask for Stephen.

 

[Jack Houpe]

Alan I believe the tire pressure is referring to Avon tire pressure, when I race I inflate them to 22 in front and 24 in the rear, at the end of the 59 miles doing never less than 100 MPH they are up 2 lbs in the front and 1 in the rear. If I remember right Dennis suggested 20 psi which made me a little nervous but he would know far better than I.

Jim what do you run yours at?

 

[Jim Craik]

Jack,

As I only drive mine on the street, I run a little higher pressure than you. I try and keep them at 25lb front 28lb rear.

 

[Jack Houpe]

Jack,

As I only drive mine on the street, I run a little higher pressure than you. I try and keep them at 25lb front 28lb rear.

Sounds good to me!

 

[Rich E.]

Roger Kraus Racing Ent., Inc.- Castro Valley, CA.

They've set up my 40 and RX7. Both were perfect.

 

[Seymour Snerd]

Alan I believe the tire pressure is referring to Avon tire pressure...

In the doc the 16/18 spec is for street. The track spec is 23/27. Neither alludes to any particular tire make or model. You would think SPF would be thinking of BFG T/As if they were going to spec a street pressure, right?

Just for reference, attached is the doc in question:

View attachment Gt40 Chassis Alignment Info.pdf


My questions about alignment per se are not about how to set up my car; I've already done that. They are:

1. Has any one actually tried 1/8" toe out at both ends?
2. As an intellectual/educational inquiry: Why do you suppose someone knowledgeable would call for 16/18 psi which compared to other street vehicles' specs are unusually low.

 

[Richard]

Hi Alan sorry I didn't drop by I ended up flying home a week ago. The document looks like the work of Mike Evangelo who worked for Dynamic Motorsport which was a Superformance dealer many moons ago. He was very good and worked out a lot of the bugs in the early cars. I did my own alignment (string theory, no that's not it but I did use string) and followed the factory specs. Car is stable at 130 but really haven't done any fast road work. I also make some of my own tools when I have to just let me know what you need. Sense my car is still in LA you'll have to take pictures with circles and arrows. Have you driven the car yet?

 

[Cliff Beer]

In the doc the 16/18 spec is for street. The track spec is 23/27. Neither alludes to any particular tire make or model. You would think SPF would be thinking of BFG T/As if they were going to spec a street pressure, right?

Just for reference, attached is the doc in question:

View attachment 62146


My questions about alignment per se are not about how to set up my car; I've already done that. They are:

1. Has any one actually tried 1/8" toe out at both ends?
2. As an intellectual/educational inquiry: Why do you suppose someone knowledgeable would call for 16/18 psi which compared to other street vehicles' specs are unusually low.

Alan, yes, I've tried 1/8th toe out at the front. Not by choice, that's what the car was running after installing new front uprights with an eye-ball alignment good enough to get it down to the race shop for a proper alignment.

The car drove like shite.

The race shop told me what the settings were before they got everything into alignment and the front was indeed toed out slightly. The car seemed to wander about a lot at the front, and was heavily affected by the particular undulations and bumps of the road ahead. It was not fun to drive, at all.

 

[Seymour Snerd]

Hi Alan sorry I didn't drop by I ended up flying home a week ago. The document looks like the work of Mike Evangelo who worked for Dynamic Motorsport which was a Superformance dealer many moons ago. He was very good and worked out a lot of the bugs in the early cars. I did my own alignment (string theory, no that's not it but I did use string) and followed the factory specs. Car is stable at 130 but really haven't done any fast road work. I also make some of my own tools when I have to just let me know what you need. Sense my car is still in LA you'll have to take pictures with circles and arrows. Have you driven the car yet?

Good, good. That makes sense. Yeah I drove 7 miles up and down Skyline with toe-in at 3/4" (I measured later) and it was all over the road. But everything works! (except my hearing for a while afterwards)....