Steering, Suspension, & Brakes

Thoughts on putting the lower shock mounts on the control arm bar as shown?

Rob, Thats the way I would do it. Make sure you are midpoint in travel at road height. I prefer 1' higher, would rather top out than bottom out.

Hey Rob,

No reason at all for that to be a bad idea.
A couple of things to think about though.
As you already have the shocks, shock travel is going to dictate where you mount them.
The further out on the arm that you mount them the better, generally.
As you go out on the arm the shock has to do less work and has an easier time controlling the wheel.
Also with a coil over the spring rate can go down as it has more mechanical advantage as it gets closer to the wheel.
Ride harshness will go up as you move out but you aren't building a Caddy are you? The tradeoff is more precise wheel control.
The problem is you may not have enough shock travel to allow adequate wheel travel as "you go out on the limb" as it were.
Another issue is, whats limiting your suspension travel? It looks like the job is handled by your shock.
Not a problem as long as the shock was built for that. Bump stops are mandatory whether internal or external.
I think Art mentioned this before, can your shocks be mounted inverted? It would reduce the unsprung weight significantly.
Your upper mount looks like its 90' off. The heim joint can probably handle the misalignment but it will wear quickly and may bind in this position.

Hope thats of some use.
Cheers
Fred

Thanks guys. I got the shocks with this mounting location in mind. I just started second guessing attaching them to that tube. Sounds like no issue with that.

They'll be right at the middle of their travel at ride height & have enough travel to not bottom out on compression before I hit the bump stops on the body. On extension, the shocks would bottom out before the control arms reach the bottom of their travel... not sure what I can do about that. There's nothing to stop the control arms from dropping till either the shocks bottom out or the 1/2 shafts bind up. How should that be handled?

With respect to how far out on the control arms, I have them as far out as they can go. Any more & the springs will hit the plate where the IRS bolts to the frame rails (the OEM rear shock mount points). I found some calculations on the web & ordered the springs based on the shock angle & effectiveness based on how far out from the pivot point they'll be mounted. I think the spring rate is close, but the good news is I can swap them out for cost of shipping if needed.

Now to Fred's observation that the upper mount is about 90* out from the lower. I'm not following how/why that's an issue. The upper & lower mounts are bearing style like the ones below. I've checked & they don't bind throughout the range of travel. Is an issue that the ends are 90* out or only if they bind?


As for mounting upside down, I'll have to check into that. They're QA1 adjustable units if anyone knows.

Check with the shock manufacturer. It needs to have an internal bump stop or the shock will get damaged when it tops out.
I think that the QA1's are equipped with one but don't quote me on that. I don't believe that they will accomodate inverted mounting though.
The main issue with spherical bearings is binding. If they are within their range of motion then no problem.
Remember that these things are carrying the weight of the car on them. So mounting is important.
My concern is wear. When they are used in a side to side application the bearing is exposed to a large window of opportunity for contamination ingress. When operated in a more radial environment the exposure is much less.
Probably not a big deal in your case. But it does limit your shock choices in the future.

Cheers
Fred

I've been working like a dog lately -- haven't had time to do the 4 welds for the lower mounts! But, I got 2 mins today & called QA1. The shocks I have (DS401) are hydraulic dampened vs. gas so no issue with mounting upside down. There's no internal bump stop so I'll need a way to stop suspension drop before the shocks bottom out -- and before the 1/2 shafts bind too for that matter. Is a simple rebound strap of some sort the way to go or is there a better answer?

Rob, Do what the 4X4 guys do and use a nylon limit strap. Available in different lengths. From upper frame to lower control arm,slightly shorter than full droop. [www.polyperformance.com]



Edited 1 time(s). Last edit at 06/30/2011 05:50PM by mgb260.

That's about what I had in my mind -- didn't know there was a commercial option available; thanks Jim. Will be easy to come up with a way to mount at the top. To mount to the LCA's I'd need to make & weld on some tabs; right now there's no place to attach them there.

The strap idea will work well, just not the prettiest solution.
Also remember you have a spinning shaft right there. Might be a little inconvenient if they catch.
What about a small finger and pad off the top mount bar to catch the upper control arm?

I like that idea even better; think that's what I'll do.

Rob, I don't know what the wall thickness is on your control arm, but you may want to consider one + gussets from mount to crossbar(s) ? Good Luck, roverman.