User 121020

Spherical bearings provide much higher stiffness than poly or rubber. I'm trying to reduce the unknown stiffnesses in my suspension system by eliminating sources of compliance. Ideally this will lead to a more predictable feel and a suspension system that is dominated by the coil spring rate and damper forces.

No idea about Koni damper body clearance. The bearing spacers will work with Konis as long as you select "Koni" from the drop down menu when the site asks for damper model. Konis and penskes use 12mm upper pin mounts.

As Dan_UK mentioned, there is no difference between the car model/year selections, according to GC.

With my rates and current damper/top hat setup, I could probably run a ride height below 12", if I flip the spacers to further convert droop travel into bump travel. Once you start talking about customized suspension, everyone's setup will yield difference clearances. I'm shooting for a ride height of 12.75" in the rear. There doesn't appear to be enough clearance to the hood to use these in the front.

legend4life

Thanks for the reply. No STR class rules restrict against the spherical billet mounts? Are these GC mounts comparable in quality/performance to the ones offered with ASTs and the like?

Have you added stiffer mounts/bushings to remove compliance throughout the rest of the suspension? How much of a difference do you feel from this, and does it destroy the streetability?

Why just 12.75" if your setup would allow lower? Do you know to size the spring length and bump stop to set safe maximum shock travel without risk of bottoming?

User 121020

You can use spherical bearing top mounts in stock classes, so they're legal in ST* classes. Yes, I'm in the process of swapping all of the OE rubber bushings with stiffer bushings. Most are being replaced with polyurethane and I'm using the Spoon hard-rubber compliance bushings in the rear location of the front lower control arms.

I have never seen a set of AST mounts in person, so I cannot comment on quality. I imagine the AST ones are nice. Performance wise, the GC change the vertical location of the spherical bearing. I don't think the ASTs achieve the same change.

Why would you need much lower than a 12.75" hub center-to-fender lip ride height? A ride height of <12.5" in the front would make the tires contact the fenders over just about any bump...and that's considering high spring rates and high roll stiffness rates. The rears can tuck quite far without hitting the fenders but the fronts will be hard into the fenders at that point, so the front dictates what rear ride height I run. I don't want to run a 12.75" front ride height and a 12" rear ride height. I plan to run 12.5" to 12.75" front and 12.75" rear ride heights.

Further details of my setup will not help you figure out what will work for you. You have to take your own measurements. My Penskes are not off-the-shelf units, so the lengths are not common. You also have to consider what anti-roll bars you're using, as they will increase/decrease damper travel during cornering due to roll.

legend4life

Thanks again for your help, new here and just asking questions in general and learning.

Are you planning on running the rear at 12.75 just to have some rake, since both ends would be fine at 12.5? What have you found is the benefit of rake, and how do you think it would compare to say running a lower rear at 12.5 with zero rake?

Also, how important is droop travel? Would it make sense to use the 1" spacer config to decrease chance further of bottoming out? Does losing too much droop become a concern? Or does it not fit anyway because of the clearance to the fuel filler in the trunk?

If I'm using the GC spherical mounts on the Koni 8242 threaded sleeve kit style coilover: https://plus.google.com/photos/11014...CMnptdS7rNjaHg
(installed pic was at 13"R, stock top mounts, 2.5"x8"x440, will be running stiffer/lower)

I would not want to trim the bottom portion right?

How would I determine how small of a bump stop to run, and what ride height is safe without bottoming out?

User 121020

I'm going to be experimenting with rake, this season. I expect I will settle on front and rear ride heights around 12.75" even, but I wanted to give myself a bit of room to adjust around that ride height. I previously ran 12.75" rear ride height, but was contacting my shortened (and stiff!) bump stops on bumpy lots and on streets. After almost losing the rear on the interstate crossing a big dip caused by an overpass driving back from an event, I decided it was time sacrifice some droop travel and increase the bump travel a bit.

Using the 1" height adjustment configuration would make my rebound adjuster rub the fuel filler bellow quite a bit and make rebound adjustments very difficult. Also, I don't want to sacrifice any more droop travel than I need to. Droop travel is a good thing, as it helps ensure your inside rear tire will remain in contact with the ground. Too little droop and you'll lift your inside rear tire.

I believe the GC top hats are made for 2.25" ID springs, so they may not work well with your 2.5" ID springs. You'd want to discuss that with Ground Control before buying. Also, you may need to trim the bottom boss a bit, depending on your clearance with the damper body. If the damper body fits inside the lower boss, they you shouldn't need to trim anything. If there isn't enough clearance (plus some margin), you'll need to trim or come up with a different solution. If I take mine off anytime soon, I'll try to remember to measure the ID of the lower boss.

Install one front and one rear damper without the springs. Use a jack to simulate your desired ride height and look at how much bump travel you have before contacting the bump stops. It's up to you to determine what and adequate amount of bump travel is. Remember to take into account the motion ratios of the suspension when thinking about damper travel vs wheel travel. 0.7 is a fair number to use for front and rear motion ratios.

//steve\\

^The GC tops are meant for 2.5" ID springs. I made 60mm ID springs work on my last setup but they fit very tight and I didn't like it much. I think 2.25" ID springs would be too tight.

I too also think that the bottom boss can easily and safely be trimmed a good 1/4" if not a tad more and still have enough material to make sure your spring stays centered.

User 121020

Thanks for the correction. Good to know. I wasn't concerned with the actual spring perch, so I didn't pay it much attention...other than removing most of it.

//steve\\

Your style coilover has the upper spring perch separate so I can see why you wanted/needed all of that material removed. For what I did it definitely needed to stay but you could definitely still trim it down some for extra clearance.

legend4life

What is the extra clearance from trimming it doing, is it increasing available shaft/bump travel?

//steve\\

I'm considering going with a set of these but would need to source a set of upper spring perches. They could be either 60mm or 2.5"

Anyone know where I could get 4 for a reasonable price?

I just picked up a set of ASTs but want to make these tops work vs just running the AST tops. Only piece I need is that upper spring perch.


***EDIT: I spoke to Vorshlag yesterday and was told that I could order the spring perches from AST no problem.