quick question about coaxial spring hats, and pillowball upper mounts

[91talontsifwd]

I have been doing alot of reading recently about a suspension set-up for my 1G AWD. I am going to be looking into making my own coilover set-up using bilstein and koni shocks, hypercoil springs, and upper pillowball mounts, and was sort of confused about the upper pillowball spherical bearing set-up, and how the coaxial hat set-up fits into the picture. I looked at the RRE upper camber plates and it states on the website about how it separates the spring forces from the shock forces. The way I'm picturing it, it seems as though this is not possible. When you have a spring sitting between the lower perch and the upper coaxial hat and the suspension goes into compression, how can you not have the forces going through the shock shaft onto the spherical bearing? I guess I'm just confused about how the RRE kit is different than other sets and how exactly the coilover upper mount is constructed.

 

[jtmcinder]

The point of coaxial hats is that they prevent side-forces inside the shock. If the spring presses up against the chassis, instead, then any time that the shock moves from being at a perfect tangent to the chassis, side-forces are generated inside the shock which causes both stiction and wear. Coaxial hats prevent this.

Camber plates and coaxial hats are the way to go with a 1G. Can't go wrong with RRE, either. If you can get inverted front Bilsteins, that sounds great.

 

[91talontsifwd]

Ok thanks...that makes sense. So the coaxial hat purpose is to move the upper spring perch off the mount to the chassis? And the RRE plates separate the forces by having the lower spherical bearing standoff double as the upper spring mount? Or by having the lower stand-off compatible with a coaxial upper hat butt up against that?

 

[jtmcinder]

Yes. I like to think of the coaxial hat and the spherical bearing as separate. The coaxial hat keep the force of the spring (and, therefore, the weight of the car) from becoming a side-force inside the shock. The bearing prevents the shaft from being bent when the shock is not a perfect tangent to the chassis. Yes, both problems really come down to the tangent part, but I still like to think of them separately. I do this partly because replacing the rubber shock bushing with a spherical not only eliminates bending of the shaft, but also prevents the shock's shaft from moving up and down, as well, do all suspension movement goes to the shock, allowing the shock to do it's job.

To answer your question: with a coaxial hat, the weight of the car no longer goes from the spring to the chassis. Instead, it all goes through the shock's shaft (or, more accurately, through a cylindrical stand-off from the hat to the spherical bearing).

 

[91talontsifwd]

Thank you very much, you answered my question perfectly... nut, upper standoff, spherical bearing, lower standoff, coaxial hat (with no space inbetween), spring, etc. Im also going to be doing roll center correction, bump steer, etc. Im really excited to undertake this project on the suspension world and Im still learning and this part was the only part that i couldnt picture since ive never worked with a coilover set-up before. Thanks again.

 

[jtmcinder]

Excellent call on the roll-center correction. It's hard to expressed how important this is. I've driven two lowered Evo Xs, one with the WhiteLine kit and one without. The body-roll and soggy mid-corner behavior of the car without the kit was very obvious.

 

[91talontsifwd]

Yeah, I'll be looking into more of the geometry involved once the point starts getting closer to fabrication. I'm going to be modeling the suspension one of these days before I start everything. Is this something you have done before? I have been looking around for software to make the process less painful, but its looking like I'm just going to have to do it the hard way with plumb bobs and a ton of math. I'm trying to picture how that whole process is going to work too. I should be able to do it on a level surface with the vehicle on jackstands correct? I was thinking that it would have to be at full weight and at ride height, but the geometry should be the same without having to do all that, correct? I'm thinking I should be able to do all the geometry corrections, fabrication, etc., and then set everything full weight, at ride height, then do the corner weights, unsprung weight, etc., and then select my spring rate and length. Is this a logical approach?