Questions on suspension parts
 

Wrapping up the suspension here shortly - just need a few more parts, and I have a few questions.

1. Is anyone familiar with the MMR spherical bearings? Do they retain the factory toe adjustment?

2. I'll be doing the DTSS deletes here shortly and I think I have a good idea of what needs to be done. I know I need a 32mm socket but is there anything else I should be aware of? How much of a pain in the ass is the install?

3. Along the lines with (2), but how much of a pain is it to remove/reinstall the rear control arms? Just thinking about installing the MMR spherical bearings.

4. Anything else I need to know when screwing around with things back there?

Simplest way is to remove entire rear suspension, rebuild, then reinstall.

I don't Know about the MMR bearings, but I don't see how they could remove the rear tow adjustment, the rubber bushings have the hole in the center.

I have not done a DTSS delete, as my cars DTSS is not worn out yet and works very well. Sorry I can't help with that one.

1. Don't know.
2. Take a look here. May not be what you'll do but has some information you can use. http://www.mazdatrix.com/faq/rrsteer.htm
I recommend removing the entire knuckle assembly so its easier to press in/out with a vise/press/threaded rod. You can also replace any other old (20yr old) suspension rubbers and clean the suspension while you're at it.
3. Dropping the subframe may make your life easier if you want to do this. It's heavy if you have the diff and arms still attached so be careful.
4. Safety first. Consult the FSM too.

The MMR spherical bearings replace the forward bushing on the rear control arms, which is the one that contains the factory toe adjustment, I believe. I was originally going to replace the bushing with one from the Energy Suspension kit but after doing some reading it is not recommended to replace that is you have adjustable camber links (MMR or AWR). This is where I first heard of the MMR bearings as most people recommend those or to stick with stock if you have the adjustable links. Here is MMR's website: http://www.mmr-direct.com/.

Regarding the other stuff I have a FSM and I'm familiar with Mazdatrix's walkthrough so I have a vague idea of what needs to be done. My biggest concerns right now are removing the 32mm nut as I don't have an impact wrench and pushing the axle in so I can remove the carrier/hub assembly.

Easiest way I've found to remove the rear subrame is this.

Jack up the car and remove the exhaust from the cat back
Remove the driveshaft
Remove the muffler heat shields
Reposition jacks underneath "Frame Rails"
Grab two creepers, three jacks and two friends.
Two jacks go at either end of the subframe, and one under the diff.
Lower all three together onto the 2 creepers and slide the whole assembly out.

Takes me all of 25 minutes.

When removing the axles, unscrew the nuts until they are at the end of the stud. Hit with ball pien hammer. Remove the nuts, push the studs out, the axle falls away ;)

MMR bearings do in fact retain factory toe adjustment. they supply a block off plate for the cam, but you can just reuse the OEM cambolt and adjuster plate thingy. i have them in my car.
the design is def better than mazdatrix/AWR (whoever) bearings, which require welding. MMR's use a retaining clip. just try not to get angry when your shit doesnt show up for 2 months lol

and while your subframe is out you might as well do its bushings. either mazdacomp or delrin. subframe bushings dont really add too much NVH, so i dont see a reason not to just do delrin.

dtss is easy. use a 2 jaw puller and find a socket thats the right size to press the bushing in/out. word of warning tho, be careful how you place the puller on the hiub. its all aluminum, so if the jaw is barely hanging on to an edge, it can break off. not really a big deal, just makes it harder to position the puller in a way that works.
or use a press i guess..

removing the axle nut is pretty easy. just have someone stand on the brake, and use a breaker bar with a pipe on it.

Alright well I went ahead and placed on order for the MMR bearings. I also have the Mazdacomp front differential mount, subframe mounts and differential stop washers on order. Hopefully everything won't take 2 months to arrive because I'd like to get all these things installed and get the car aligned before the NASA season starts out here.

So as I'm getting closer to ripping out the rear suspension I figured I'd bump this...

I've got just about everything for my rear end swap (4.30:1 ring and pinion and Miata T2 Torsen going in). I'm replacing all the differential mounts with the Mazda Competition ones and one question I had was whether it would be wise to replace the subframe mounts during the process? Usually I wouldn't question the matter but at $90/piece they are quite expensive for rubber mounts.

i'd do it just for the fact that its such a pain in the ass to get the subframe back out. you're putting all that other crap in there so why not.

That was my reasoning, but after spending $1k+ on rear differential and subframe crap, I was really not wanting to spend another $200.

How bad are the delrin subframe mounts? I've been hesitant to go with anything "solid" (hence all the competition mounts), but at $120/set they are significantly less expensive than the stock Mazda pieces (at least according to Mazdatrix). Would there be any downside to having those solid, while everything else is "stiff" rubber?

On another note, I'm still waiting for the spherical bearings from MMR. Got the PayPAL shipping notification last Friday and still nothing (shouldn't take a week to ship from TN to OH!).

if the diff mounts arent solid, i dont see any reason why solid subframe mounts would add more vibration. they're just a second level of vibration damping from the diff.
delrin is probably not gonna be noticable.

MMR can be slow sometimes- I heard of others complaining about them but they've always delivered in the end.

I also recommend biting the bullet and replacing as much as you can when everything is out. Granted, it does depend on your budget and personal judgment.

Good luck.

The rear diff mounts don't really affect much. I have them w/ the comp front diff mount, pinion snubber, and derlin trans/ motor mounts. Vibration is not bad, and this is on a daily driven car.

I'll check this thread in a month, you MIGHT have your MMR order by then.

I have all the competition mounts for the engine, transmission and differential.

As for vibrations, I'm not worried about the differential because it is isolated with a rubber mount from the subframe. However, with delrin subframe mounts all the suspension vibration will be transmitted straight from the control arm to the subframe (via spherical bearing) and then into the body (via delrin subframe bushings). I guess all this would do is make the vibrations from rough roads more intense in-cabin, correct?

Well, I got everything installed this past weekend. Aside from breaking the speedometer drive gear in the transmission (so currently no speedometer) everything went okay.

I'm disappointed how much drivetrain lashing I still get; even with the full set of Mazda Comp. engine, transmission and differential mounts and delrin subframe mounts. The only thing with the stock rubber back there is the vertical stabilizer bar. What I call "lashing" is the jerking/bouncing and noise associate with on/off/on throttle transitions. Because I lack the proper tools, I had a shop set the backlash and ring gear contact so I don't know why there is more noise going on unless they didn't do it correctly. I also did not install a pinion snubber as I didn't think it would be needed, but I'm guessing that was a mistake.

Is there something else going on here or is this just a fact of life with a FC?

Did you replace the "bushing" that are in the "ears" of the rear diff case?
The stock ones are "hollow" with just a few "spokes" (I think 4 per side?) that allows the rear diff to move a lot.
Did you replace this with one of the delrin units?


-Ted

Are you referring the "mounts" colored purple in the picture below (picture credited to Racing Beat)? If so, then yes, I replaced those with the "Competition" units along with what's colored red and yellow. I made sure the "voids" or gaps in the rubber material were facing forward/aft per the FSM. Only the subframe mounts (not colored) were replaced with delrin units.

http://www.racingbeat.com/images/items/diff-mounts.jpg

all my fc's have had a decent amount of lash. it could just be the transmission. put it in gear (car off), and twist the driveshaft by hand to see

The more I read, the more this comes up. Some people say adjusting the TPS helps, but I'm fairly certain mine reads within acceptable limits. I'm going to get the car in the air later today to check things out - specifically the driveshaft and halfshafts.

What has me shitting bricks right now is the metallic "thunk" I'm getting during these on/off throttle inputs. Experience tells me the differential backlash is off, but I was ASSURED by a transmission/differential shop it was okay. My only other theory is that this noise is always around and that it isn't until after installing semi-solid mounts that it becomes audible.

Who's telling you that adjusting the TPS (throttle position sensor) helps with drivetrain lash? Bad advice - adjusting the TPS has absolutely nothing to do with drivetrain lash.

Yes, those are the "weak points".
You can literally grab the rear diff and sometimes shake it with your hands and see the entire rear diff swaying under there.
Imagine the amount of torque backlashing through the drivetrain?
It's violent.

I've never seen "solid" aftermarket mounts to replace those "Differential Casing Mount" (PURPLE).
I've seen aluminum ones - TOO stiff.
I've seen stiffer replacement for the "Differential Stop Washer" (RED) underneath - i.e. URAS - that don't really do squat either.
If I could, I would try and play around with a SOLID polyurethane mount.
If I ever get off my lazy ass, I might even try and play around with a brand new set of mounts and injecting some of that "gray weatherstripping RTV" into the voids - it's a trick some racer use for those bushings with voids in them.

Those mounts are the cause of why the rear diff moves around so much. :(
The other extreme problem (mentioned with the aluminum mounts) is that if those mounts are too stiff, you risk damaging the rear diff casing itself.
Those mounts absorb a lot of the rear diff movement.
Once you start to restict that movement, something else gets stressed.
What happens is that the "ears" of the rear diff housing that those mounts are inserted in tend to crack off.
Remember, the rear diff housing is made out of cast aluminum...
To combat this problem, I've seen custom rear diff frame braces made to minimize the ears cracking.
And now we're back to square 1...

Also, if all of that isn't bad enough, the front diff mount is a stupid design.
That mount resticts movement via a shear force of the mount - WTF???
This is where a pinion snubber comes in and does help...but it can only do so much.
There is still a lot of movement up there.
So what can you do?
Most will tend to crank down (reinforce the front diff mount or solidly mount it) the front diff (pinion) to the rear subframe...
Again, now you risk breaking the rear subframe itself - I've seen this happen also.
And now we're, again, back to square 1...


-Ted

^^^ All good points. I've considered the RTV trick, but hesitated due to the concerns you've expressed. I've also heard of people inserting objects between the stop washers and mounts (like ground down hockey pucks) but that would lead to the same issue.

Everything that's "colored" in that picture has been replaced by the Mazda Competition mounts, which are supposedly 40% stiffer than stock. The only "solid" mounts I have are the subframe-to-body mounts, which are delrin.

I checked for free-play in the drivetrain on Friday. Aside from discovering the left-rear wheel bearing is going, there was a little moving in the driveshaft at the u-joints, but it really is not that bad considering the car, and driveshaft, is 22 years-old. I'm now almost certain the ring and pinion backlash is off. There is a good amount of free-play in the rear wheels before I feel resistance. Time to go have a word with the shop that set the backlash...

Aren't these mounts from MMR what you're referring to? http://www.mmr-direct.com/Pictures/R...ts/rx7diff.jpg

That's what I have for my rear diff. I am also considering the MMR spherical bearings, as you cannot use individual camber adjusters with the delrin control arm bushings. My question is how can a spherical bearing give enough play to force camber adjustment while Delrin cannot? I would've thought that the bearing would be under more stress and would fail if adjusted too far under constant driving.

Poly/delrin is no good in the rear control arm because its motion is not uniaxial. poly/delrin doesnt 'twist,' so you're only supposed to use it in arms that move in one direction. The rear control arm twists due to the camber curve, and a spherical bearing allows it to articulate freely.

poly/delrin is fine in the front control arm since the front/rear mounts are on the same axis, so theres no twisting motion.

I assume this is where you got it from?
http://www.mmr-direct.com/catalog1/RX7FC/index.htm

I hate it when vendors use "generic" pics for their pages. :(

The pic you posted was for an "rx7diff" part.

Yes, it does sound like their "Rear Differential Mounts" part is the part I'm talking about.

Their plastic is still too hard for this application.
It will tend to break the ears off the diff as I have mentioned earlier.

As a side note, the engine and transmission mounts they offer are crap.
I hate when vendors "get cheap" and offer these types of mounts that do not properly mimic (or do a better job than) stock mounts and bushings.
Just because of this inferior design, I would never use their products.


-Ted

Simply the fact the spherical bearings allow rotation/movement along more than one axis. As Josh said, the delrin mounts only allow movement in one direction. I have the spherical bearings installed and I am still able to get the desired toe settings.

Regarding "solid" mounts I'm a firm believer there needs to be play SOMEWHERE in the system. If everything is solid the vibrations get transferred right into the mounts and THEY WILL ultimately fail (low-cycle fatigue). As Ted said, you want some movement at the differential cover or you will break the mounting points. I only went with delrin subframe bushings was because the stock ones needed to be replaced and I could get both delrin bushings for less than the cost of one OEM bushing.

Might as well keep this thread going...

Anyone else here have the AWR camber links? I currently have mine adjusted all the way "tight" to maintain -1 degree of camber in the rear, which in itself isn't a problem. The issue is with them adjusted all the way up the bolt is hitting the underside of the car. There are two "holes" on the lower part of the link (the part that interfaces with the control arm) arranged vertically. Right now the bolt is going through the lowest hole, but I was wondering if this could be changed to be the upper hole to gain a little more adjustment.

Here's what I'm talking about:

http://store.awrracing.com/product_i...18918_zoom.jpg

Notice how the bushings are in the lower hole on the link on the right? It looks like they could be inserted into the upper hole to get a little more positive camber back. Just curious if anyone has tried this or if this is even the purpose of the other set of holes.

there are two holes so that they dont have to make 2 different parts (left+right). you're stuck using the bottom hole. the link wont fit in the control arm the other way, unless you cut it up.

as for the bolt sticking through the floor, let it happen lol. its just sheet metal. mine punched holes in the floor years ago.
if you actually care, you could just cut down the shank or buy a shorter one.

^^^ That's what I figured. I really don't care that the bolt is hitting the floor. What bothers me is that both of my rear coilovers are all the way up (~1/4" engagement remains) and to get -1 degree of camber in the rear the links are adjusted all the way together - there's no more room for adjustment.

When I get back from Mid-Ohio this weekend I'll get under there and take a look to see how much the control arm would have to be adjusted to use the upper holes. If it can be done with minimum cutting/impact to structural integrity of the arm I'm going to try it. This would give me so much more room for adjustment.

you can always get a center link to take out some more camber. afaik, the only thing stopping you from using the upper holes is some steel that could be cut out. doesnt really look structural...

I have the AWR unit but it's not installed. I bought it before I did the rear end swap so I didn't know I was going to go with delrin subframe mounts at the time. I didn't think the adjustable link would work if you had delrin subframe mounts. Kind of like how the individual camber links won't work if you have delrin bushings in the control arms.