How Crucial Are Radial Bearings in Rear Shock Mounts?
 

I'm working with Vorshlag Motorsports to select new springs for my MCS coilovers and they're recommending that I replace my Raceseng rear shock mounts with their rear shock mounts, because their mounts use a radial bearing that prevents binding and the Raceseng mounts use a solid bushing. This makes sense, but I exchanged e-mails with Jarrett Seng and he indicates that in reality the damper shaft experiences virtually no binding at the bushing, because the shaft motion is basically linear during articulation.

I don't get a sense that Vorshlag Motorsports is simply trying to sell me something I don't need - they're serious people and they're hard racers. I already own the Raceseng rear shock mounts and they're beautifully made, and they match my Raceseng front Cas/Cam plates. Replacing my Raceseng rear shock mounts isn't an inexpensive proposition, but if binding is a legitimate issue I'll do it. What do you guys think?

I don't think it's an issue. I run the raceseng stuff front/rear with my MCS.

If you've got money to burn, then sure.

If you don't find you're currently having issues, I wouldn't buy yet another upper mount.

Vorshlag has a rear top mount? It's not on their site. I'd be interested in seeing it, but it seems like I'll end up making my own.

There's no reason you can't place a radial bearing at the 'bottom' of the spring on the spring perch if you're really concerned about binding. And I'm surprised Vorshlag didn't offer it up as an alternative. It's less ideal because it will get dirty a bit quicker and require more maintenance vs. being built into the top hat, but might be a bit cheaper than eating the loss on selling used parts (although you'd have no trouble selling them).

I believe that's how Fortune Auto does it iirc (can't pull up their site right now for whatever reason), and I know Eibach sells standard sizes: (No 60mm I think)

https://www.summitracing.com/parts/eib-trb250

And the cheap option is just a plastic disc or two, that's how Bilstein's come and a few others:

http://www.streettunedmotorsports.co...202_744303.htm



Edit: If you're competing and care about hundredths of a second on your lap or run, it might be worth spending the money up front to make sure it's not an issue, if not you'll never notice. After all, the factory didn't bother to build that in and it would have cost a few bucks to do it in the rear like they did in the front.

According to the Raceseng site their rear top hats use a spherical bearing, NOT a solid mount.

As others have mentioned, you can add a radial bearing if you're concerned about spring bind and/or NVH.

I did not see their rear top hats for sale under the BRZ/FRS section, but what I did see in that section is Redline power steering fluid. Odd, since our power steering is electric and not hydraulic, therefore no fluid...

You're correct - my mistake. A more accurate description of the issue is that the Raceseng part has zero articulation, essentially making the the spherical top mount useless and behave like a solid bushing. Here's a photo of the Raceseng and Vorshlag Motorsports parts side by side:

The shock shaft is still free to move with the Raceseng mount, but it would require spring deflection for the movement to happen. Looking at the rear geometry, I'm not sure this is really an issue at all.

The Vorshlag mount looks like it increases the stack height of the assembly as well.

For the rear shocks I don't think this is a super critical issue, and the Raceseng top hats allow at least some movement even if the spring isn't properly isolated. The big concern is bending a shock shaft or wearing out seals prematurely. When you secure the top hat to the chassis it's almost perfectly lined up to where it needs to be on the control arm.

I'd say it's much more important for the fronts - it's really obvious there that the spring/shock does not want to line up perpendicular to the strut tower mount. It's also really obvious to me based on the collection of dirt on the spherical bearing (thanks AZ weather!) that it actually moves around a bit.

Option 3:

http://www.ft86club.com/forums/showthread.php?t=110426

http://media.frsport.com/Damperworks...FS01-03@2x.jpg

Is that the 'Top Hat Coaxial install kit (not pictured) MSRP - $150.00' finally pictured? Basically an upper spring perch?

Basically $450 MSRP is 1) the coaxial rear upper mount ($300) + 2) the coilover-specific conical spring upper seat w/ hardware/spacer that is specific for the coilover ($150)