NEW SUSPENSION IDEA is FINALLY FINISHED

[VETTEPRO]

The front suspension mod is FINALLY done. It took a few tries to get it just right but It came out pretty good. Skip to Post# 29 if you've read all this and are interested in just the front.

Below is the original post from when I first came up with the idea:

I had a rear axle vibration problem and when putting it back together, I started looking at the shock mounts on the rear. I didn't see any reason you couldn't make an extension so the mount is lower, which would move the control arm up.
I cut up an old supercharger bracket and started to make a set that moves the mount down by 1.25", as a starting point. I haven't done the math yet but because of the leverage ratio between the control arm pivot point, the shock mounting point and the outer side of the hub, I'd guess that you would be able to drop the truck over 1 1/2" without losing ANY travel on the shock. That would solve a lot of problems.
It's 5/8"' aluminum plate. I'm going to weld a locating ring on the backside to fit in the locating hole in the control arm. There is a flat machined into the bottom of the control arm, so I'll machine a step in the bracket that will butt up against it and stop it from rotating.
I think I'll need to put a counterbore in the bracket to sink the upper bolt so it won't hit the shock body.
Then the bottom hole also gets a slight counterbore to locate the shock and then gets threaded.
I ordered all the bolts and taps I need to finish it.
The picture is a rough cut 1" piece. I'm going to make a nice 1 1/4" piece on the mill. That will be just about right with the stock bumpstops.
The front is a different story. The bottom shock mount appears to be cast iron of some sort. It's kind of shaped like a big"Y". The bottom hole could be slotted and dropped "a little" but not enough to make much difference. I'm going to get new lower mounts, machine a steel extension of some sort and weld it back on with Nickle rod. Then I can redrill the hole higher up and drop the shock lower over the control arm. It looks like I can go about 3/4" before the front axle will touch the shock bracket at the bottom of the shock. I'm pretty confident that I can clearance that part of the bracket and gain some more room. If I could move the mounting point an inch, I think that would give me at least 1 1/4" of drop without losing ANY shock travel at all. You could drop it that far using the stock spring and have stock ride quality. With something like a Dinan spring, you'd have 2" of drop and lose minimal shock travel.
The front will be a challenge and won't get done in the next couple of days. I just ordered two new strut mounts to experiment with and some Dinan springs. I'll see how low I can get it with stock springs and then again with the Dinans.
UPDATE: The front is almost done. It drops 2" with stock springs. The Dinan springs will be too low. I have pictures in post #23.

[BadCompany]

Hell yeah. Keep me/us updated. I love seeing stuff like this come to life.

[VETTEPRO]

So a 1" movement of the rear shock mount nets you 1 1/2" drop with no loss of shock travel. I was going to do 1 1/4" but that gives me almost two full inches of travel so now I have to start thinking about the tire rubbing before the shock bottoms, so I went with 1" to start.
I ordered the wrong bolts so I can't actually test it until tomorrow but the pieces are done and fit well. I'm going to let the air out of the bags and cycle the suspension with a post jack to see if I can go further without rubbing.
Keep in mind that I am no machinist and these are not nice CNC machined pieces. I made these with a band saw, 12" disc sander, hole saws and an old Bridgeport. I just like making new stuff that actually works. I'm surprised something like this isn't just available to buy.

[pachieh]

This is really interesting and could be a much easier way to lower the car (before doing coil overs) to mitigate some of the ride quality concerns with just springs.

Like you said, rear is probably easy. Front will be interesting.

Any concerns about stress on the upper mounts since you are changing the angles from the bottom some?

[VETTEPRO]

Originally Posted by pachieh

This is really interesting and could be a much easier way to lower the car (before doing coil overs) to mitigate some of the ride quality concerns with just springs.

Like you said, rear is probably easy. Front will be interesting.

Any concerns about stress on the upper mounts since you are changing the angles from the bottom some?

Not at all. Pulling the shock out to this angle only takes a few ounces of effort. The rubber in the shock eye itself moves easily.
If you look at lowering kits for Chevy trucks, for instance, they include a lower shock mount relocation bracket to give you back the travel you've lost. This is no different. It just seemed like a no brainer to me.
I have a good idea of what I need to do in the front as well. I'm just waiting on the new pieces from BMW. I'm going to drill and tap my plate so I can run a bolt through it and cut it off at about 1/2". If I use a 5/8 bolt, I can turn down the part that sticks out so it is almost a press fit in the factory shock mount. I'll spot weld the other end of my of bolt where is cut off flush with the plate. I'll have a non threaded stub sticking out that will fit tightly into the existing bolt hole in the cast iron shock mount. That will take the load, rather than just the weld. The weld (unless I can figure a way to just bolt it in place) will be mostly for alignment.

[andrewmr]

Can't say that I know 100 percent how the rear suspension are in our cars but I thought the rear was a separate shock and spring. Pretty sure it's that way in mine.

If that is indeed the case, how would lowering the bottom shock mount lower the car?

[VETTEPRO]

The F85-F86 has adjustable air bags. If you let it down too much, the shock bottoms all the time. It's really not comfortable at all.

[andrewmr]

Originally Posted by VETTEPRO

The F85-F86 has adjustable air bags. If you let it down too much, the shock bottoms all the time. It's really not comfortable at all.

WOW, that would seem like it would damage the shock. I would have thought there would be rubber bumpers that kept the shock from bottoming out.


Anyway, thanks for the info.

[VETTEPRO]

So I finished the rear today and it works just like I expected it would. I'm at 29 1/2" and there is no bottoming at all. I figure I have pretty close to full shock travel available.
I drove it at this level immediately before I put the extensions in place. They made a huge difference.
I drove it around my shop neighborhood and hit some decent low speed bumps. No bottoming or tire rub so far. I have 20MM spacers and I still have no tire rub.
I guess I need to bounce over some railroad tracks to verify everything.
I'm happy with the results and want to get to the front now. I have the H&R VTF springs up front and the shocks bottom a lot.
I just got Dinans so I'll put them on and work on the front suspension drop. Now this mod will actually lower the vehicle, as the shock and spring assembly actually supports the weight of the vehicle.

[pachieh]

I wonder if the Dinan bump stops would be necessary in this.

[1badttx5m]

This is awesome, I have a few ideas but I’m curious as to what you will do with the fronts. It will be awesome to have stock ride quality while being able to be lowered that much!

[VETTEPRO]

Originally Posted by 1badttx5m

This is awesome, I have a few ideas but I’m curious as to what you will do with the fronts. It will be awesome to have stock ride quality while being able to be lowered that much!

The front would not be such a problem if it weren't for axle clearance at the bottom of the shock. When you have the suspension hanging, the axle contacts the base of the cast iron piece that the shock sits in.
I worked out the front geometry today and it's even better than the rear.
If I can clearance that and move the shock mount by 1 inch, you'd gain 1 7/8" of wheel travel without losing any shock travel at all.
I bought some 1/2" steel plate today and will have 5/8" bolts and a tap tomorrow. I "might" have a working bolt on piece tomorrow.
It would be easier to do 1 1/4" becuse having two large bolts that close together causes interference issues. Unfortunately I don't think I can gain enough axle clearance to go 1 1/4".
I may make an 1 1/4" extension for the rear just to see if I can get away with that much travel. I don't know where limit is as far as tire rub goes.

[YvesD]

Loving this project 😁👍

[F85MTuNED]

Is there any benefits to using these extensions with the KW's?

[VETTEPRO]

Originally Posted by F85MTuNED

Is there any benefits to using these extensions with the KW's?

I would say yes. Travel is travel, no matter what shock you use. Contrary to what people say on this Forum, the KW does not have more travel, nor is it shorter to start with, than the stock shock, at least not appreciably. I think both the valving and spring rates are very progressive and that's why you can get away with being lower. The shock rapidly stiffens up as it gets close to it's end of travel.
There is no substitute for additional travel though.
I measured my KWs against the stockers and they are virtually the same. You certainly do not gain any meaningful amount of travel. They do have shorter bump stops, but that's easy to do to the stockers.
Speaking of bump stops, here's a little trick I've learned over the years. If you are going to shorten them, don't cut them straight off. Cut them, then sand them so they have a rounded profile. That way if you hit the stop, it's progressive. You'll notice how the stock ones are thin at the end and get thicker. That makes them softer feeling when you hit them.
We live down at the beach and there is a set of railroad tracks almost at the end of Ventura road. I've lived here 22 years and have never seen a train, but the tracks remain for some reason. With my KWs, set at the same height I have now, they would bottom if I hit the tracks at 40 or over. Yesterday I hit them at 42, in comfort mode. The front definitely bottomed and I "think" the rear did too. It wasn't real harsh though. That shows me that If I really whack something, the shock will bottom before the tire hits anything, which is obviously what you want. Remember, I have 20MM spacers and I'm still not rubbing.
I went back around and hit them again in sport mode and only the front bottomed.
1 1/4" ones may actually be better for the rear. Now that I know I'm not quite at the limit yet, I'll make a set and see.
I also went through the Home Depot parking lot and went over all the speed bumps with the same results. The front bottomed where the rear didn't.

[VETTEPRO]

Here's an update on the experiment. I had to go to the welding supply store yesterday. I loaded two large Argon tanks in the back that weighed 375# total. Then I went to Harbor freight and picked up a couple of extra tool carts and some extra crap. That added about 40# additional.
So I had over 400# right over the axle and it still rode fine. I found a very tiny Donington Gray rub mark on both tires right at the edge of the tread. I never felt or heard it, but it was there. I think just changing from 20MM spacers to 15MM would probably take care of it.

[WERND]

Or take some camber out if it was the outside shoulder

[VETTEPRO]

Originally Posted by WERND

Or take some camber out if it was the outside shoulder

That would definitely work, but I already have about as much negative camber as I would want. I have a couple of sets of spacers and lug bolts.

[WERND]

Originally Posted by VETTEPRO

That would definitely work, but I already have about as much negative camber as I would want. I have a couple of sets of spacers and lug bolts.

No, take camber OUT

[VETTEPRO]

Negative camber means the tires are tilted inwards at the TOP. Adding more negative camber would move the tire away from the fender lip. I don't want to have any more negative than I already have. Besides tire wear, it just starts to look stupid.
Reducing negative camber would move the tire out, which would be the opposite of what needs to be done.

[pachieh]

Any updates?

[VETTEPRO]

Originally Posted by pachieh

Any updates?

I just got the front shock "forks" (or whatever you'd want to call them) on Thursday. My shop is actually very busy throughout this COVID 19 stuff so I haven't done much. I wanted to try the shock mod with the Dinan springs first, but I'm afraid it will be too low. I may do it with stock springs first.
Unlike the rear mod, this will actually drop the front end, rather than just add travel. If I make a 1" extension, it will actually lower the vehicle by 1.8". That, in theory, is about 29.45" (ground to fender) with stock springs and stock travel. With the Dinan springs that would make it 28.825", which I think will be too low. Obviously these are hypothetical measurements but should be fairly close.