Z1 Subframe Bushing Collars
 

Had these installed today. Took an hour without dropping the exhaust.

Mods to date: SPL front upper control arms, SPC rear control arms, Vibra-Technics urethane transmission mount, coupe wheels, ARK Grip exhaust.

Initial impression after 50 mostly freeway miles is that there is slightly more tire noise, no increase in vibration and a noticeable increase in harshness. Not significant, just noticeable. The rear suspension feels slightly stiffer, because it is.

Take a look at the Z1 Motorsports page for the collars and watch the attendant video. There's footage from underneath of the subframe before and after. It's almost shocking how much the subframe moves around with the stock bushings. That movement delays any force from reacting with the chassis because it first has to compress the bushings. That's both engine torque application and suspension movement.

I thought I was near to having to clean my throttle bodies due to slight throttle lag. No lag now! The rear suspension is more honest in reacting to road irregularities. The rear Hotchkis bar kicks a little more on single-wheel bumps. Botts dots come through loud and clear.

Except for Botts dots and heavy washboard sections of pavement, I don't think most people will discern a difference with the collars. Yet, if you know exactly how your car behaves, you will notice them.

I'll post an update after a couple of weeks of use.

thanks for posting the review. I had to google "botts dots":P . I'm curious about the installation. was it done on a lift? I wonder if it can be done on jack stands, was anything used/needed to support the weight of the sub frame? and did you need a new alignment after?

Interesting take on highway impressions. And certainly a valid concern about road feel and NVH. I'm looking forward to your thoughts on how it changes things up in the turns.

I wonder why you would hear more tire noise? :dunno:

Good to know there's no V in that NVH. God knows I don't need any more of that.

And you immediately notice a better throttle response? That's awesome.


You and me both. We don't have them in western NY.

My guy jacked up the rear at the diff and placed two jack stands forward of the rear wheels. That floor jack under the diff is needed to support the subframe as the rear bolts are loosened. Once the bolts were loose, he needed that jack to force the rear lower collars in, even with lube. The top collars were simple drop ins.

No alignment needed.

Track event next Friday. I'll post an update after that.

As for tire noise, the soft squishy bushings damped the high-frequency noise that should have been transferred by the wheel to the axle to the diff to the body. It's not a lot more noise, only a little. Slightly louder when whacking sharp transitions, too, like stepped pavement.

Yes to throttle response. It would be more noticeable, I think, if I had done the diff bushings, too. Mine hasn't ruptured yet, so not fixing what's not broken.

It's kind of wierd. I don't really notice more of anything besides noise, what I notice is the lack of things. Lack of that small throttle response lag, the lack of delay when going over road imperfections.

I describe it as the rear being more honest. Same thing as when I put urethane suspension bushings on my Sentra SE-R -- I became aware that the rubber bushings allowed the control arms to flex slightly rearward when hitting bumps and going over railroad tracks. With the urethane, the car motion was subtly different without that rearward flex.

Excellent review. Psyched for more, you old trailblazer.

That Vibra-Technics in your sig, that's a poly transmission mount, right? Figured if you're digging that mount, you're sure to like these collars. In fact, that's begs a fair question.

Where 1 is OEM, and 10 is unbearable, how would you rate the transmission mount? And then with that in mind, where would you rate these collars?

Awesome! those are exactly the details I was looking for...sounds very doable...I know Z1 says its an easy install on the website but they say that about everything...don't get me started on the brake MC bracket ...

So, tell me about the MC brace.:D

The Vibra-Technics is indeed the polymer trans mount.

Keep in mind that I am not that Princess who has problems with a pea.

So, I'd give the Vibra-Technics mount a 3.5 or so. My brother noticed it immediately after I installed it but I don't know if he still does. It was obvious to me at first but I barely notice it anymore. The guy who took off Hotchkis bars because it ruined the ride for him would not want this mount.

I rate the Z1 subframe bushing collars a 2 just from the slight increase in harshness.

As I asked the question, I was prepared to call my Z1 mount a 4, based on nothing in particular. So... cool. :biggthumpup:

And I am pleased that you corroborate my assessment. Gives me confidence in my rating ability.

Great review! I actually ordered these on Tuesday along with my Whiteline Dif bushing kit and figured I'd knock out 2 birds with 1 stone. While I appreciate the hwy feedback, my biggest interest is in cornering and off the line feedback.

Have you not pushed it from a stop light or anything else where you're redlining? Also what is your track day? 1/4? 1/8? road?

He removed the two rear nuts but left the fronts alone. Once the rears were bolted back up, he then moved to the front two nuts. Two bolts are enough to keep the subframe in position.

Track day is at Motorsports Ranch Houston, a 2.38 mile road course. I don't normally perform drag starts, I'm more of a roll-on guy, like when entering a freeway with a short entrance ramp. Still, light acceleration from a stop light while in traffic can show the improvement made by the collars in fore/aft movement.

for a split second I thought it was something dirty


lol ...suffice it to say, you need the hands the size of a toddler to work in that space and you better pray you don't drop anything...I gave it a shot before I moved in the fall..no go....I'll be taking another shot in the spring when i have time/am feeling masochistic