Max Bump Travel RSM and Camber Plate Options?

[thegenius46m]

Hey all. Looking to maximize bump travel on my new suspension which is an custom valved fat cat motorsports fcm elite stage 3 coilover system that uses h&r front coils and bilstein rear shock bodies that are a little longer than my old mcs coils. I currently have ground control street camber plates and rsms and am looking to try and move to something that gives me the maximum travel possible while not being obnoxious on the street.

It looks like Vorshlag camber plates will give me me almost an inch extra of bump travel up front over the gc setup so this seems like a no brainer there because I can move back to a 7” spring (from 6”) for increased travel while retaining my current ride ride height of 13” in the front.

Now the rear is the big concern. It seems clear that I need an RSM with the most clearance possible from the top of the shock body to the tower to add more bump travel and am trying to figure out options.

The vorshlag spherical rsm is one that comes to mind, but does anyone know approximately how many mm more of travel I can gain from changing rsms from the current setup? If I can really get an additional 8-10mm then I’m gold but it doesn’t look like the design really allows that. All the product information states “increased bump travel” but how much?!

https://vorshlag-store.com/products/vorshlag-rear-shock-mounts-bmw-e30-36-46?variant=15148884167

Pic to current setup at ride height with suspension loaded.



Any input appreciated. Thanks!


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[Tbonem3]

The vorshlags, in the race version for 60mm like you and I have, have the shortest stack height, yes. GC and TMS are good too, but not quite as much.

For rear, the only RSM that I know to raise droop is the GC "tall" but those only come with poly bushes and you likely want spherical.

If you still have trouble fitting a 7" front spring, at your rate, look into TCK vvs springs as they're 6.25" and provide a little more travel or look at Eibach and H&R's metric coils - they come in 160mm or 170mm 6.3 - 6.7" You'll just then need to know what metric spring rate you'd want i.e., 8kg = 448lbs

[thegenius46m]

The vorshlags, in the race version for 60mm like you and I have, have the shortest stack height, yes. GC and TMS are good too, but not quite as much.

For rear, the only RSM that I know to raise droop is the GC "tall" but those only come with poly bushes and you likely want spherical.

If you still have trouble fitting a 7" front spring, at your rate, look into TCK vvs springs as they're 6.25" and provide a little more travel or look at Eibach and H&R's metric coils - they come in 160mm or 170mm 6.3 - 6.7" You'll just then need to know what metric spring rate you'd want i.e., 8kg = 448lbs

Honestly at this point I just want max travel within reason so that I'm not limiting the capabilities of the car because I'm getting into the bumpstops way too early for it to do what it needs to. Looked into the gc tall last night but I dont want to loose droop travel. I just want the bump stop to get as close to the shock tower as physically possible so that under a big compression hit the tire sucks all the way into the wheel well and stops right before it would rub the body as long as the sideskirts don't hit the ground. Pretty much same thing with the front. I want max travel before the bump stops have to come into full play to stop the body from contacting the ground or the tire rubbing the liner hard. I'm basically having to compensate now for longer shock bodies on both axles.

I realized moving to a 6" spring up front although it got me the ride height I wanted due to the H&R body being 1" higher, I technically lost travel. So I'm thinking if I move to a Vorshlag camber plate up front, I should be able to move back to a 7" spring and get the travel back while getting the ride height back to the same height I am at now, but without the geometry tradeoff. The Vorshlag plate apparently will sit 1" higher up over my GC plate but they also have a single row bearing option that will get you an extra 6mm of travel if needed. At that point I probably will need to modify the bumpstop so it does its job accordigly.

For the RSM, I'm going to take some measurements tonight and see if I can really gain anything measurable over the current rear setup by going to spherical. Vorshlag told me over the phone you actually can use the shorter spherical insert on the bottom side for extra travel so I need to compare that measurement to what I have and see if there is enough clearance left to be worth buying.

[Tbonem3]

For the rsms, I even went so far as to use thinner washers to gain a little more travel as the washers supplied by GC (american, not metric) were a good 3/16" thick.

[cobra]

You don't have much to gain from reducing stack height beyond a certain point, since the tire will hit the fender before reaching metal-to-metal depending on tire size and offset. Judging by your current setup you might even need to add a thin packer to prevent interference on bottom out.

For reference at a 13.75" ride height in rear, you have about 3-1/4" of usable travel and 3-3/4" before the tire hits things. The stock shock only has about 1" before it hits the bump rubber and the springs are super progressive so it doesn't really get close to using that.

In front the story is similar. The tire crashes into the fender liner at 11.5" ride height. So if you're already running at 13" height you only have 1.5" of travel. Doesn't matter if you reduce stack height because you'll need to add packers or bump rubber back to prevent it from crashing.

[Tbonem3]

His spring rates are quite high. He doesn't use much travel.

[cobra]

I don't see a mention of spring rates. OP what spring rates and lengths are you using now in front and rear?

[Obioban]

What is your ride height?

I'm on the H&R shock bodies with my FCM setup, as well, with TMS hybrid plates and GC RSMs, and wouldn't want any shorter of a stack height... as it would force me to be too low to be in the good suspension geometry, while still having optimal droop travel (40% of total travel).

I feel like the more functional solution may be to raise you ride height.

[thegenius46m]

What is your ride height?

I'm on the H&R shock bodies with my FCM setup, as well, with TMS hybrid plates and GC RSMs, and wouldn't want any shorter of a stack height... as it would force me to be too low to be in the good suspension geometry, while still having optimal droop travel (40% of total travel).

I feel like the more functional solution may be to raise you ride height.

Still testing as the car has been down for other reasons, but I raised the front to 13" the other day and did a canyon run (may have been 12.5" front before) and it made a noticeable improvement. I think the rear height is 12 3/4" iirc. After comparing measurements with Vorshlag, it appears I can gain an extra 8mm of rear travel by moving to spherical rsms if needed but I am also going to try cutting down the rear bump stop a little more as I'm at 33mm atm and the car is a tad loose with no packers currently. I can always add rear packers to make that back up but this is promising.

[thegenius46m]

You don't have much to gain from reducing stack height beyond a certain point, since the tire will hit the fender before reaching metal-to-metal depending on tire size and offset. Judging by your current setup you might even need to add a thin packer to prevent interference on bottom out.

For reference at a 13.75" ride height in rear, you have about 3-1/4" of usable travel and 3-3/4" before the tire hits things. The stock shock only has about 1" before it hits the bump rubber and the springs are super progressive so it doesn't really get close to using that.

In front the story is similar. The tire crashes into the fender liner at 11.5" ride height. So if you're already running at 13" height you only have 1.5" of travel. Doesn't matter if you reduce stack height because you'll need to add packers or bump rubber back to prevent it from crashing.

I think that depends on whether your fenders are rolled and liners are cut. My car prior would just barely hit the torque plate on a violent impact before hitting the liner. I never hit fender but I am rolled and outer liner contact area has been cut. I cheated with compression forces on my old dampers to not bottom out but that's not ideal. A bumpstop would have been better had I known at the time. Blame mcs for that.

[Obioban]

Still testing as the car has been down for other reasons, but I raised the front to 13" the other day and did a canyon run (may have been 12.5" front before) and it made a noticeable improvement. I think the rear height is 12 3/4" iirc. After comparing measurements with Vorshlag, it appears I can gain an extra 8mm of rear travel by moving to spherical rsms if needed but I am also going to try cutting down the rear bump stop a little more as I'm at 33mm atm and the car is a tad loose with no packers currently. I can always add rear packers to make that back up but this is promising.

13” still too low to be in good geometry…