Suspension experts, need advice on pickup point relocation (Page 1/2)
SCCA FIERO OCT 18, 01:30 PM
So I have a custom made cradle in my 88, so it will be rather simple to move the lateral link mounts. Right now the links are pointing the wrong way, the mount on the cradle is lower than at the hub. The only problem I have in raising the points on the cradle is one of them can't go high enough without hitting the transaxle. So what I was thinking is moving the forward ones forward to miss the transaxle and move the rear ones back the same amount. If I did that, the links would not be parallel - would that be an issue? I'll post a pic in a bit from my phone (on work computer).
SCCA FIERO OCT 18, 01:40 PM

You can see the issue I'm trying to deal with in this pic. The bottom of my rear tire is getting sucked in as the suspension compresses and that's not good.
Below are some pics of my cradle.

[This message has been edited by SCCA FIERO (edited 10-18-2021).]

zkhennings OCT 18, 01:59 PM
I think the issue you may run into is that the lateral links control toe, and the trailing link controls displacement front to rear of the knuckle. If you put too much angle on the lateral link, you will loose toe control and begin to fight the trailing link which may cause binding. You also may get some weird toe changes as the wheel moving forwards from acceleration forces will cause toe out from the newly angled front lateral link.

Have you seen Gurus lateral link relocation kits? They drop the lateral links on the knuckle side of things. Maybe a little extra unsprung weight but avoids having to raise the inner pivots. Just have to have a large enough rim to fit it.

[This message has been edited by zkhennings (edited 10-18-2021).]

SCCA FIERO OCT 18, 02:10 PM
I did think about Guru's kit, but it just won't work for me because I want to run the 15" wheels and I don't want the extra weight. The small wheels and tires are pretty light and give me a good gear ratio for autox.

I can lift the points higher than they are right now, then I could lift the car a bit to get a better geometry. I'd just rather keep the car as low as possible.
zkhennings OCT 18, 05:04 PM
So you could do your original idea but combine the lateral links together by fabricating an A arm, and forgo the trailing link. Without the wacky ball joint and toe link setup from the pre-88s you will still have a good handling car.

I am not sure what would happen if you moved both inner pivots forwards if there is a sweet spot where you could clear everything and have them stay parallel.

You could alternatively shorten both lateral links the minimum amount necessary to clear everything and then raise the inner pivots, You will get some more scrub but I think that is unavoidable when improving camber gain with a strut setup. And it is definitely better than having the lateral links no longer be lateral.

[This message has been edited by zkhennings (edited 10-18-2021).]

cvxjet OCT 18, 07:21 PM
A few things to consider;
1) How much higher do you want to go?

2) You might want to create a rigid "H" arm like ZK was talking about; The parallel-o-gram set-up is not as necessary for your racing vehicle.

3) IF you are using all solid bushings (Including the trailing arm) then there will be very little deflection from acceleration and braking forces if you spread the inner mounting points.

4) You may be able to put SPACERS on where the arms mount to the Spindle, keeping the basic geometry intact.

5) If you do have a bit of deflection, then;
A) During deceleration it would cause the rear wheels to angle inward- This would be good considering the outer wheel would have most affect...Less DTO.

B) During accel, it would angle the rear wheels outward...Meaning the car would be more reactive to steering input while IN a turn....But you would have to straighten the wheel a bit more when accelerating out of a turn.

(Now I filled my house with smoke coming out of my ears!)
fieroguru OCT 18, 08:14 PM
If you stay with the 3 link setup, the lateral links must remain parallel. If they don't, you will get large amounts of toe change on compression and rebound. There already is some due to the different lengths, but it will be much, much worse with the links non-parallel.

You could move them to an angle and ditch the trailing link - effectively making a lower - arm that pivots about the long lateral link bolt at the knuckle (look at 240-280Z rear suspension) . You need to be careful with the design of the lower a-arm to avoid putting a bind on the long lateral link bolt as the suspension is cycled up and down the strut. That connection is cantilevered with singe shear and small diameter, so binding will lead to breaking. The current lateral link tabs on the cradle will also likely need to be upsized as they will then see all the impact loads that are currently carried by the the trailing link.
SCCA FIERO OCT 18, 08:29 PM
Here’s a better visual of what I have. My pickup points on the cradle are the same distance - the front adjustable link is the same length as the solid link.

I was wrong about the link hitting the transaxle, it will actually hit the axle and it only needs to move forward a little bit to clear.

[This message has been edited by SCCA FIERO (edited 10-18-2021).]

Robert Reif OCT 18, 08:45 PM
Is it possible to raise the cradle in the car so the lateral links and driveshafts are back to stock angles? I know that would raise the center of gravity but the geometry would be stock.
fieroguru OCT 18, 09:34 PM
Is there room in the 15" wheel to shift the front link forward about 1.5"? Looks like that would put the link on the other side of the front tab on the cradle. Doing that on the knuckle would probably require some type of outer brace on the end of the bolt.

This the old cradle that gusshotrod built back in the day?