Wow, looks like Rear Spherical Top Mounts are a good upgrade!

[FaRKle!]

ryan@PdVmotorsports.com inspired me to take a look at how much flex our rear top mounts have when I asked about the spherical top mounts he makes.

We've all seen videos of front tension strut/thrust arm movement during driving, and readily acknowledge that going to a monoball there improves response, feel, and handling, so I wanted to see if we have much play in the rear shock mounts such that putting a spherical mount there will help too. I was pretty surprised at the amount of flex I saw!

Originally Posted by Index

0:00 Intro
0:38 Why I wanted to do this
1:38 Test setup
2:30 Driving/top mount flex footage

[jmciver]

Interesting…. I can't help but wonder if this is another example of the typical trade-off between engineering/performance vs cost/comfort that pretty much all car manufactures deal with. I also wonder how this upgrade would help with an OEM+ type of suspension upgrade, like the MP HAS, which I have (or something similar) vs a full blown aftermarket setup, including a "true" coil over system…

That said, I did notice an immediate improvement (with no additional NVH) when I upgraded to monoballs in my thrust arms not too long ago…

Also, are these really compatible with the F8x? They are only advertised for the F3x AND the F8x and F3x have different rear shock mount part numbers - assuming due to different internal bushings? I would assume the geometry is the same for the F8x and F3x cars, but without looking at them side by side, it is difficult to tell with the pics of both available online.

[jfritz27]

Interesting.

The "worst" part of you posting this is that it is responsible for me going down the rabbit hole of all the videos from Fat Cat Motorsports about suspension theory, flat ride, etc. Interesting to note their perspective in the YT comments for Farkle's video... Maybe that degree of motion is desirable (depending on one's baseline setup, degree of adjustability, goals, etc)...

[Theruleslawyer]

I wonder if you really need a monoball or just something like a urethane bushing pressed in? It doesn't seem like there is a lot of rotation, just vertical on axis movement.

[to_riffic]

Originally Posted by jfritz27

Interesting.

The "worst" part of you posting this is that it is responsible for me going down the rabbit hole of all the videos from Fat Cat Motorsports about suspension theory, flat ride, etc. Interesting to note their perspective in the YT comments for Farkle's video... Maybe that degree of motion is desirable (depending on one's baseline setup, degree of adjustability, goals, etc)...

+1.

It's one thing to have a more direct feel, but at the sacrifice of compliance? I'm in more of agreement with FCM and though my car isn't a daily, I enjoy the duality of the track use and the daily use, so I know there will always be a compromise on the track so it's livable on the streets.

[FaRKle!]

Originally Posted by jmciver

Interesting…. I can't help but wonder if this is another example of the typical trade-off between engineering/performance vs cost/comfort that pretty much all car manufactures deal with. I also wonder how this upgrade would help with an OEM+ type of suspension upgrade, like the MP HAS, which I have (or something similar) vs a full blown aftermarket setup, including a "true" coil over system…

That said, I did notice an immediate improvement (with no additional NVH) when I upgraded to monoballs in my thrust arms not too long ago…

Also, are these really compatible with the F8x? They are only advertised for the F3x AND the F8x and F3x have different rear shock mount part numbers - assuming due to different internal bushings? I would assume the geometry is the same for the F8x and F3x cars, but without looking at them side by side, it is difficult to tell with the pics of both available online.

There's definitely some tradeoff here between responsiveness and NVH. The characteristics should carry over to aftermarket suspensions using the stock mounts too. The vehicle in the video is actually running Fat Cat Motorsports dampers paired with spring rates I specified.

F3x and F8x rear top mounts are similar, but not exactly the same. The only real difference is the size of the mounting hole for the damper (F8x is M14 thread and F3x is M10 thread).

Originally Posted by jfritz27

Interesting.

The "worst" part of you posting this is that it is responsible for me going down the rabbit hole of all the videos from Fat Cat Motorsports about suspension theory, flat ride, etc. Interesting to note their perspective in the YT comments for Farkle's video... Maybe that degree of motion is desirable (depending on one's baseline setup, degree of adjustability, goals, etc)...

I agree that allowing a small degree of displacement/play is probably a good thing, but it's really those larger movements that were surprising to me and I'd want to prevent that amount of extra flex from happening.

Also, most of us already have experience with this because we all have camber plates, and that's the same thing where we give up the flexible top mount for a solid spherical bearing.

Originally Posted by Theruleslawyer

I wonder if you really need a monoball or just something like a urethane bushing pressed in? It doesn't seem like there is a lot of rotation, just vertical on axis movement.

Yeah, you shouldn't have to worry about rotation since the piston/shaft can rotate within the damper body. Urethane would probably work to lessen the displacement, similar to how Millway Street camber plates use it to buffer the mounting plate/washer.

[eXstasy]

Originally Posted by FaRKle!

Also, most of us already have experience with this because we all have camber plates, and that's the same thing where we give up the flexible top mount for a solid spherical bearing.

Vorshlag camber plates in the front did not add too much noise or NVH, but in the rear I'm running MCS 1WNR with clevis mounts and they added a lot of chatter, though not quite clunking.

I expected some increase in NVH, but am unsure if its currently within expected range or if something is wrong with my mounts or install.

I'm 50/50 and would maybe have gone with coilovers that use the OEM rear mounts

[jfritz27]

Ill be installing my mcs suspension in a few months, so ive been preparing… I presume when torquing down the bolts on the clevis mounts that the suspension should be loaded some (just like the front top mounts)… maybe try that and see if it quiets down?

[M 4 FUN]

Originally Posted by jmciver

Interesting…. I can't help but wonder if this is another example of the typical trade-off between engineering/performance vs cost/comfort that pretty much all car manufactures deal with. I also wonder how this upgrade would help with an OEM+ type of suspension upgrade, like the MP HAS, which I have (or something similar) vs a full blown aftermarket setup, including a "true" coil over system…

That said, I did notice an immediate improvement (with no additional NVH) when I upgraded to monoballs in my thrust arms not too long ago…

Also, are these really compatible with the F8x? They are only advertised for the F3x AND the F8x and F3x have different rear shock mount part numbers - assuming due to different internal bushings? I would assume the geometry is the same for the F8x and F3x cars, but without looking at them side by side, it is difficult to tell with the pics of both available online.

I also have changed my thrust/caster bushings to excentric aluminium bushings and there is significantly more road noice. But the steering input and response is much better. More crashy over imperfections though. I also tried the excentric powerflex black series poly bushings but they were actually worse than the SPL alu bushings as they gave a weird resonance.

[M 4 FUN]

The question is if using a solid bearing mount is a good thing for every day use as the rear subframe is solidly mounted in the chassi. i think nvh will be increased quite much. maybe a compromise with a higher shore poly bushing could be something.

[hellokitty]

I remember doing this upgrade on my E9X. No additional NVH. It just makes the job of the rear strut easier since there is less flop and made the rear end feel more planted during road oscillations.

[FaRKle!]

You asked about NVH with spherical rear top mounts, and now we have an answer!