AST Suspension

[Don Nguyen]

Can someone also measure their ride height from the rear jacking points to the ground? I technically have shortened rear shocks and shorter springs, however, my car is still sitting fairly high in the rear. I don't have the stock rear fenders anymore, so I can't base it off of those.

thanks.

-Don

[Don Nguyen]

Alright. I know I shouldn't be working on my car today, but I couldn't help it, given the fact that the car is already down and taken apart for other things.

When I originally received the suspension, the RSMs were stacked/assembled with these rear pieces on the bottom (boxed in red):

My picture:


However, in the AST installation pictures, it shows that they weren't used or installed on their RSMs. Did anyone else install it the way that I had them and that they originally came like, or did you install it the same way that Vorshlag did?

AST picture:


Now for my second question. I am wondering if it is possible to reverse the two pieces that are above and below the RSM, which physically slides into the center section of the RSM itself (boxed in green):



This is how it originally looks like, pictured by Vorshlag (which could actually have answered my first question, based on this picture):




My idea with reversing the two pieces boxed in green above, is that it would allow the car to have more suspension travel. I could have sworn I've seen people reverse (upside down) RSMs on other coilovers to gain more suspension travel this way, or maybe I am just crazy and making up things in my head.

I am no engineer, and I am sure that AST/Vorshlag assembled their RSMs in a specific manner, however, I just like thinking outloud and playing around with ideas.

-Don

[///M3Augy]

What's the highest spring rates people are running on the 4100s? I am running 700lb rear springs and 600lb front springs, and they feel relatively soft still, at times.

I am running 600/750 and it's great!

[ChosenGSR]

Don, if I remember correctly those two black pieces are not used.

[horched]

Use the small washers only. The larger ones are not needed. I'm not sure about reversing things -- I installed everything according to the directions included with the RSMs.

[John in Houston]

The washers are there in case you aren't using the Vorshlag / AST spherical rear shock mounts. If you are, then you use the machined bushing inserted into the bottom of the spherical bearing and then the shaft of the shock feeds up into that. The Vorshlag pictures are spot on for this installation.

As for flipping the RSM, I don't believe that the true 'lower' portion of the RSM is beveled enough to allow for full range of movement (even if there is little to no movement). You'd have to contact Terry / Brian to ask their opinion on that.

[clopez95m3]

Looks to me like you don't have the top nut used in this picture. I have mine assembled the same as this pic but I had no instructions so mine was kind of a guess. I'm glad I got it right.

Carlos.

[HafaAdaiM3]

Car is running super smooth right now, no issues. My 4200's are by far the best suspension I've run on the street. I've yet to take them on the track, waiting for my cage

[Fair]

The washers are there in case you aren't using the Vorshlag / AST spherical rear shock mounts. If you are, then you use the machined bushing inserted into the bottom of the spherical bearing and then the shaft of the shock feeds up into that. The Vorshlag pictures are spot on for this installation.

As for flipping the RSM, I don't believe that the true 'lower' portion of the RSM is beveled enough to allow for full range of movement (even if there is little to no movement).

John is spot on here...

Those big flat washers are for use with a rubber RSM, such as a stock replacement. The struts and shocks come with a number of extra parts that aren't used in every situation. We explain this in the AST installation videos located here.

As for flipping the RSMs or the spool pieces... no. Each one is machined for a specific orientation. There is a slightly tapered shoulder on the upper shock shaft that mates with the bottom spool. The top spool is made to go on a square shoulder, under the top nut. If I have extra time packing up a kit lately I have been pre-assembling and pre-tightening the spherical RSMs (if ordered) to the AST shocks, to avoid confusion and phone calls.

[BraveUlysses]

AST picture:

Hmmmmmmmmmmm...my 4100's never came with bumpstops for the rear shocks.

[maxxfish]

Yesterday I tried to lower the rear ride height on my E36 racecar. I'm running 4200's, converted to coilovers in the rear. Unfortunately, to get my car any lower than 6" between the rocker (at the rear jack point) and the floor, I'd end up with ZERO suspension travel. So I have to stick with a 6" ride height just to have about 1" of suspension travel not including the bumpstop.

This doesn't seem right. My car weighs 2704 with me in it, perfect 50/50 distribution front to rear, and corner-balanced within 1%.

Any suggestions?

[Don Nguyen]

What are your tire/wheel sizes?

My car sits around 5" or so, from the rear puck jack point to the ground. That is with 295/40/18 tires on the rear.

I am running standard shortened shocks and springs in the rear. I have about 2"-2.5" of suspension travel between the bottom of the RSM and the top of the bumpstop.

-Don

[Eric98Sedan]

Yesterday I tried to lower the rear ride height on my E36 racecar. I'm running 4200's, converted to coilovers in the rear. Unfortunately, to get my car any lower than 6" between the rocker (at the rear jack point) and the floor, I'd end up with ZERO suspension travel. So I have to stick with a 6" ride height just to have about 1" of suspension travel not including the bumpstop.

This doesn't seem right. My car weighs 2704 with me in it, perfect 50/50 distribution front to rear, and corner-balanced within 1%.

Any suggestions?

That doesn't seem right to me either. What is the distance from your center cap to the fender lip?

[hancheyb]

Yesterday I tried to lower the rear ride height on my E36 racecar. I'm running 4200's, converted to coilovers in the rear. Unfortunately, to get my car any lower than 6" between the rocker (at the rear jack point) and the floor, I'd end up with ZERO suspension travel. So I have to stick with a 6" ride height just to have about 1" of suspension travel not including the bumpstop.

This doesn't seem right. My car weighs 2704 with me in it, perfect 50/50 distribution front to rear, and corner-balanced within 1%.

Any suggestions?

Maxx,
This wasn't by chance done by RRT? If so, let's take this offline and discuss btwn the three of us. I know there was some questions about what springs were being used.

On another note, the first kits we sold did not come with rear bump stops. The expectation was that you would reuse your existing bump stops. No one has ever mentioned it to us as an issue and it was not very many kits. We have since updated all kits to include rear bump stops. We updated the package pricing too at the time.

Threads like this have helped us to refine the kits and make them better and better. For instance, adding rear spring seats and instructions. Even better, we added video instructions. Thanks for all the feedback!

Brian

[GotCone?]

Brian,

Saw your AST's in the newest issue of sportscar!!!

oh and btw... emailed you earlier this week.

[BraveUlysses]

On another note, the first kits we sold did not come with rear bump stops. The expectation was that you would reuse your existing bump stops. No one has ever mentioned it to us as an issue and it was not very many kits. We have since updated all kits to include rear bump stops. We updated the package pricing too at the time.

wanna mail me a set?

I never thought oem would have been an acceptable replacement due to differences in firmness and length of bumpstop.

[raoke]

Is it an issue if those washers arent used with non AST rsms? I'm using the UUC Meyle HD rsms.

[maxxfish]

Bumping...it seems as if both Don and I can't get the rear ride height low enough without bottoming out the shock travel. Any solutions?

[Fair]

Bumping...it seems as if both Don and I can't get the rear ride height low enough without bottoming out the shock travel. Any solutions?

Again, your set-up is very different than anything else we've seen (coilover rears with 60mm ID springs, I think is what you have?? We make the the 4200 and 4300 into coilovers with 2" ID springs + helpers). Please send us details of your set-up (rear ride height, spring rate and length) to sales@vorshlag.com and we'll see if we can help you get it sorted out.

Don's set-up is also extremely low by any standard (his is a wide bodied show car) - we made his rear shocks shorter than any E36 set-up, but its still not enough. There are, of course, limits to anything.


Custom eye to eye coilover AST 4300 shock made to work with E36 chassis at the rear - note custom upper shock mount, concentric Rebound adjuster, etc.


This is a more typical E30/36 rear AST4200 coilover set-up - using an AST rear coilover conversion perches/kit, 2" (50mm) ID rear springs, and a 2" ID helper.

With the spring moved to the shock in the rear the motion ratio changes dramatically, and optimal spring rates are considerably lower than if 60mm springs are in the OEM rear suspension location. We stock a number of 2" ID Hyperco springs and helpers for use in applications like this.



Cheers,

[Don Nguyen]

Is anyone running more than 750lb rear springs on the 4100s?

I have about 2" of shock travel, with 5.5" springs, and the collars adjusted 1/2" away from the very bottom.

[hancheyb]

Don,
Keep in mind you're the only E36 in the country running shorter E30 shocks on the rear. If you recall we made a special kit for you since you had a wide body kit and wanted to run lower. Not sure any responses from "the gang" are going to tell you much, as Terry said.

Also we can revalve the shocks to run whatever rates people want. I'm not sure anyone has asked for more than 800ish in the rear (from us anyway). We have 800s on our LS1 car in the stock location (for now).

Brian

[Don Nguyen]

Interesting.

Would my rears have to be revalved to run the 800lb rear springs, or would the fact that they are currently running 700lb rear springs mean that they should be able to handle it?

I've also heard that a 100lb increase in spring rate isn't going to be too noticeable?

Thanks for the reply.

-Don

[GotCone?]

I'm not sure anyone has asked for more than 800ish in the rear (from us anyway). We have 800s on our LS1 car in the stock location (for now).

Brian

I did.. but on an E30 and in the stock location for the spring. Running 950lb springs in the back currently on OTS 4100's.

[Don Nguyen]

Got Cone, what are you running in the front?

Is your car a full track car?

[GotCone?]

street/track car currently.

700lb rate up front w/ stock swaybar. No swaybar in rear. Car is 95% where I want it balance/handling wise. might end up going down 50-100lb in the rear at most rate wise. Waiting to get the new tires on there before I change anything up.

I'm quite pleased w/ the AST's. Amazed really as they ride quite nice at these rates. I came from Koni 8611's previously on a non-bmw chassis and w/ lower rates (and different geometry) it road much worse. But that car required a much different setup to work for it's intended use.

I'm an AST convert... won't likely buy anything else... ever.

Thanks - Jon