Aaron Cake

iTrader: (1)

The rear suspension of my car ('86 NA chassis) is pulled apart right now and I'm trying to figure out this DTSS elimination. I would have rather not eliminated it, but both my toe control bushings are shot and Mazda does not sell them without including the whole hub. I'm simply not willing to pay $800+ each per hub for the cost of a $30 bushing.

The rear hub actually has three bushings; the toe control DTSS bushing, the pillow block (lower) and the rubber (upper). Seems to me that when DTSS eliminator bushings are installed, the function of those other two bushings becomes moot. So I'd like to avoid having to buy two $100 pillow ***** and two rubber bushings if there is an option.

I've literally spent 3 hours looking for information with little success.

So, here are my questions....

1. Mariah sells a DTSS eliminator Delrin bushing set here:
http://www.mariahmotorsports.com/suspension.htm

"Bushing Pkg, Rear Control Arm, 86-92 (Set)
Includes: Foward/Outer, Rearward/Upper at Triaxial Hub, and Toe Steer Eliminator Bushings "

It looks like this set contains all three hub bushings in Delrin form. Is this correct? If so, then that answers all my other questions...

2. Mazdatrix has what they call "rear swingarms and rear steer eliminator set" in Delrin here:
http://www.mazdatrix.com/rmounts.htm



From the picture it appears that the kit contains a bushings for the rear swing arm (I don't need these), a DTSS eliminator and then the upper bushing for the hub. Is this correct?

3. If the Mariah / Mazdatrix kit does not include all those bushings, is there anywhere I can get solid replacements for the upper and pillow ball bushings? Then I can just get DTSS eliminators from anywhere....

-Crash-

I am unsure of what the other kits contain but I know if you are looking at just buying the DTSS bushings MMR sells them for $40 (for two I believe)

Go to catalog then FC, 7th one down I believe.

http://www.mmr-direct.com/

Aaron Cake

iTrader: (1)

For the record, I called Mariah yesterday and asked. Jim was very helpful and said that part # 1595 (the description I quoted above) was a full replacement set for all the bushings on the toe control hub. So ordering that set includes 2 of the following: toe eliminator bushing, upper triaxial bushing, pillow ball (lower) bushing, all in Delrin. This eliminates the need to buy a new upper and pillow ball (and associated seals) from Mazda when rebuilding the suspension with toe eliminators.

He did suggest that there is a limited supply because it will take their machine shop a day or two to churn out my set before they send them. The price on the website when up ot $230, which I still consider quite reasonable. I ordered a set.

rx7racerca

iTrader: (1)

I just used a set of DTSS eliminators machined from delrin by someone locally here, and left the other hub bushings, redundant though they may be - mind you, my car even now only has ~125k kms on it, about 100k at the time, so my DTSS bushings were still in good shape.

Get a good alignment (0-1/16th" toe out front, about 1/8" toe in rear), and the car will still be agile, and you'll not miss DTSS anyway - except in a happy way if you track your car, and actually want the backend to be predictable at 10/10ths driving.

lov-2-rev

iTrader: (87)

I have done a complete delrin / urethane bushing swap on the rear for one of my FC's. However, I didn't bother replacing the pillow ball mounts. Once you put a "solid" mount in place of the DTSS bushings and the soft rubber triaxial bushings, there is no compliance for the pillow ball to pivot; Making it a third, solid mount on the hub. I also replaced the pillow ball grease seals while I was at it for another $30.

Not to insult you in any way, but you could have gotten the same end result for about half the price by purchasing a set of Racing Beat or Mazdatrix DTSS eliminators and sourcing a set of delrin triaxial bushings.

cone_crushr

iTrader: (18)

And exactly where is he supposed to "source" the Delrin tri-axial bushings from?

I suggest that the Mariah kit is a good solution, although I agree that there is no value in replacing the stock pillow ball unless it's worn (unlikely).

As an aside, I prefer using an aluminum DTSS replacement insert rather than Delrin since the inner sleeve will slide around otherwise. Its most noticeable when braking in reverse, but certainly occurs while driving hard at the track also. Uncontrolled deflection of the rear hub assy is bad for handling at the limit. For a street car, no big deal I suppose.

Aaron Cake

iTrader: (1)

My DTSS bushings were destroyed when I took apart the suspension, unfortunately. The bolt had seized into the bushing so it tore it apart upon removal.

Noted. I will bring those exact numbers to the alignment shop.

Maybe my original post was not clear?

The rear suspension of my car ('86 NA chassis) is pulled apart right now....

Seems to me that when DTSS eliminator bushings are installed, the function of those other two bushings becomes moot. So I'd like to avoid having to buy two $100 pillow ***** and two rubber bushings if there is an option.

So the issue is that I needed replacements of these two other bushings, but replacing them with stock parts that are unnecessarily expensive because their function has been eliminated seemed like a stupid option. Paying $250 for two pillow *****, a few more dollars for seals, then two $40 upper bushings seemed like a waste of money and parts, considering those bushings are now redundant. Hence, Delrin solid replacements...


I'm not sure I'll be doing much braking in reverse at high speeds.

LargeOrangeFont

iTrader: (7)

Just an FYI for others..If your lower pillow ***** are still good and you install DTSS eliminators you can just leave them in there and just replace the upper rubber bushing with delrin.

You can have that bushing custom made for about $100. I'll be getting that done when I replace my rear wheel bearings soon.


By the way Aaron, you will not miss the DTSS. The car is much better without it. The toe settings listed above will work great. That is about what I run.

lov-2-rev

iTrader: (87)

I found mine in the "for sale" section a while back for $35.
I also noticed that the front control arm bushings are very close in size to the triaxial bushings.....Slightly larger OD with a flange. A set of these could be purchased and milled down to the proper size. If there is a competent and reasonably priced machine shop in Aaron's area, I'm sure they could make a pair of them without much trouble.


That is my overall point; Doing it on the cheap.

*as long as your pillow ***** are intact*
Get a set of DTSS eliminator bushings - MMR-Direct = $40
Buy a set of FCA delrin bushings (see above) and machine to fit = $70-80ish(?)
Buy new pillow ball seals - Mazdatrix or Mazda = $30

Although the Mariah set is fairly priced at $230, the same end result could be achieved for less.

Aaron Cake

iTrader: (1)

I could have had the bushings machined, or borrowed time on a lathe and machined them myself, but I didn't want to be bothered. Sometimes it is nice to just place an order and have parts show up a week later.

Now, as I thought I was clear about previously, if someone is just eliminating the DTSS then dealing with the other bushings is unnecessary. However, since my suspension was totally disassembled (and my bushings were mangled) I need to replace the bushings. I did not want to waste money on the Mazda pillow ***** because they are redundant, as is the upper rubber bushing. Hence looking for an aftermarket solid option.

I don't get the confusion.

j9fd3s

iTrader: (3)

+1

the DTSS system ADDS toe in in the rear. toe in in the rear adds stability.

on a DTSS car, you can run zero toe, because the DTSS adds toe when it gets a load.

without DTSS a little static toe in is a good starting point.

i initially set my car up at zero toe, and if you turn in with some throttle it feels awesome, but if you turn in with no throttle it feels much less planted/stable than a stock car.

so you can season to taste, i added a little toe back in the rear, and i'm happy.

i didn't notice much difference in the front going from stock to zero toe, the steering response is razor sharp, but it didn't change the dynamics like the rear did.

rx7racerca

iTrader: (1)

Just further to my suggestions for front toe - zero may be best, depending on how the car is driven most. If you do a lot of street/highway driving, slight (1/16) toe out is not extreme by any measure, but may make the car a bit "darty" or prone to tramlining in truck ruts - hunting back and forth. If you do track days/lapping, as opposed to autocross, the toe out can also make the car feel slightly less stable on high speed straights - although I don't think it would be an issue, I run more toe out - 1/8 to 3/16" - and don't usually change it for track days (I do my own alignments). On the other hand, it definitely improves turn-in responsiveness, but at 1/8"+, the tramlining on truck ruts and dartiness in crosswinds are pretty noticeable - and tiring on longer drives. Not that well suited to drags, either.

Also - set caster to the max you can - if you're still using the stock-style eccentrically mounted upper strut mount, the position that puts the strut both furthest back and to the inside, maximizing negative camber and caster. You'll not likely get significant negative camber out of it (only got ~-.3* on mine without adding eccentric/crash bolts to the lower stut bolts), but maxing the caster enhances road feel, slightly increases steering effort, and gives more negative camber gain as the wheels are turned - this is a big part of the reason BMW's have traditionally enjoyed great steering feel and good handling.

full-cruise

iTrader: (5)

i just want totrack this, im dealing with the same issue

Jet-Lee

iTrader: (1)

What are the OE toe control bushings made of?

Does anyone have any specs on them? Like size, shape and component makeup?

I enjoy my DTSS and my current employer may be able to have some things sourced and machined and assembled for a small group-buy. So any and all details and specifications would really help.

EDIT-What I've gathered from pics I can find. A metal (stainless steel?) sleeve that is pressed into the hub, with a longer but narrower sleeve through the middle. Now, what is the flexible material between the two?

If someone has a bushing laying around and could take the following measurements (of each) for me, I'd greatly appreciate it! Using a micrometer would be ideal.

Outside Diameter
Inside Diameter
Thickness
Length

And best guess on the flexible material? I have access to neoprene of all various densities, and the capability to press-fit it all together.


Maybe we can finally have a company that can provide a replacement DTSS Toe Bushing?

jjcobm

iTrader: (18)

Thanks for the info Aaron, this would of came handy when I was rebuilding the rear subframe, but I decided since I put the DTSS eliminator, to just
run the original pillow ball lower and the upper bushing since they were ok and essentially they really would do nothing...

Rubber with an inner sleeve in the middle of the rubber and an outer sleeve around the rubber that contacts the spindle. As you turn, the rubber allows "play" which changes the toe of the wheels.

It will be very hard to get specs since most of the time these things rip apart taking them out, unless someone gets lucky or has new ones laying around

Highly doubtful as a lot of people do not like the feel of it and it will be much easier to manufacture a solid bushing rather than a O.E. DTSS like bushing that will have to be replaced if it starts to deteriorate, but would be nice to have options....

LargeOrangeFont

iTrader: (7)

I would never put the DTSS back in the car. After eliminating it and getting the car properly aligned (slight rear toe in), the car is more consistent and easier to handle at the limit.

nycgps

iTrader: (4)

I bought mine at RacingBeat.

When I was trying to remove the DTSS, I touch it, the middle part fell right off. but those rubber on the side seized so much that I almost wanna throw the whole **** away and get a new hub ... but then I was like **** outa here a new hub cost almost the same as the car **** that lol

Took me like a day something to remove both and reinstall ... god it was painful.

Jet-Lee

iTrader: (1)

Just my opinion, but it's an engineering feat for a reason. Learn to utilize it and you can handle the car quite effectively, even at the limit.

I've done my fair share of at-the-limit driving on back roads and on the track, and I have to say that I love the feel of the DTSS way more than without. Maybe I can't spit the backend out as easily, but I prefer to stick anyways.

LargeOrangeFont

iTrader: (7)

There is a reason cars don't have "rear steer" features anymore. It was a neat novelty that didn't really do much to help handling for the added cost and complexity.

Pretty much anyone that races these cars removes the DTSS. After removing mine I see why. I ran the car with the DTSS in for about 10 track events. Since I removed the DTSS it is much easier to to put the car where I want it in a corner, and it is much more responsive to steering inputs at the limit. Honestly removing the DTSS it was one of the best things I did to improve the feel of the car. My bushings weren't broken or rotted out either. They actually looked pretty good but I'm sure they were not as effective as they were 23 years ago.

j9fd3s

iTrader: (3)

foxed.ca if you look in the 86 training manual it has some nice pictures of the bushing, and actually a really good bunch of info about how the rear suspension works as a whole. like aaron alludes to, its not just the DTSS bushing that moves its all of them working together

the bushing is just a normal bushing but has different rates of deflection in different directions. its kinda like the front lower control arm bushing, but with one side cut out.

also keep in mind that the bushings are tuned to the tires, the enfini had different tires and bushings than everything else

Jet-Lee

iTrader: (1)

That's your opinion and your preference.

Not mine.

I DO know the difference, and choose to keep the DTSS if at all possible.

Like you just said, it was done away with due to marginal gain being outweighed by cost, reliability and complexity. We're driving 20+ year old sports cars, so obviously cost and reliability don't exactly matter to us at this point. It's really not that complex of a system, either.

We'll let the market decide, if I find it possible to manufacture a replacement. Right now there's really no affordable option but to delete it, so you can't say it's the best thing you can do cause it's the ONLY thing you can do.

j9fd3s, Thank you.

rx7racerca

iTrader: (1)

Right from the first track tests, DTSS was critiqued by even experienced testers and seasoned competition drivers as making the car difficult to control and to predict at the limit. DTSS and other passive and active rear-wheel steering systems have mostly gone the way of the dodo because they added complexity and expense, and while they improved the driver's sense of responsiveness in street driving at normal to moderately fast speeds, they contribute little in the way of actual improved grip - in the case of DTSS, they actually make it very difficult for an experienced driver to drive it on the track at the limit, in favour of keeping less skilled drivers out of trouble at lower loads and giving a slightly synthetic sense of agility.

There's a reason why people who track these cars do away with the DTSS - they simply handle better, and just as importantly, more predictably without. I removed my DTSS bushings when they had less than 100,000kms on them and were in good condition (still have them in a drawer out in my garage somewhere). I would never go back - before, on track if the back end got a little loose, it was all over, I'd be going for a 360 or ***-backward in the weeds. Now, I'll enter turn 1 at the local track at 180, and balance the car in what is essentially a slide on the knife-edge of traction with the throttle - other drivers come for rides and are amazed at the balance and what I can get away with.

As far as the design - the rubber between the inner and outer sleeves has a series of void shapes in it that control how the suspension deflects under various loads- which would likely be hard to replicate without also having the specs of the material itself. They have to be oriented correctly in the hub carrier to work properly - I made no note of it when I had mine pressed out, so I can't help there either.

Jet-Lee

iTrader: (1)

I just said that.

Here's a little bit of reading of other peoples opinions as well.

https://www.rx7club.com/showpost.php...1&postcount=11

https://www.rx7club.com/showthread.p...9&page=1&pp=15

So because a lot of "Racers" had a suspension tuned to what they liked and were used to, it's automatically the best thing since sliced bread? I mean really, what a novel idea, to tuned the suspension to what the racer is used to rather than get a racer that's used to a specific suspension. It was solid before, it's what they were used to, so when this came out then they simply eliminated it to get the feel they DESIRED.

Some of us have other desires, same as no one will convince me to go turbo if I don't want to.

If people want DTSS, why not support them? Are we inferior somehow?

rx7racerca

iTrader: (1)

No, it's not a matter of what's desired by a driver that won't adjust to DTSS, it's a matter of DTSS being unpredictable at the limit - more about which momentarily. It's also a matter of understanding what DTSS was designed to do - which was to keep average drivers safe on the street while giving the car a sense of extra agility, not to maximize grip on the track- which also has a great deal to do with the fact these cars have not generally been top competitors in various autocross and road racing classes they've been in since they were new, against cars with very similar specs like the Porsche 944. Against which the 7 came in 2nd in every single comparo I ever saw - usually with comments like "great at up to 9/10's driving, at which point the car becomes unpredictable, as if the chassis is trying to outguess the driver, and the rear develops a mind of it's own".

How DTSS goes about achieving it's goals for the street: it does this by allowing toe-out rear hub orientation under cornering loads less than ~.5G (the natural orientation of semi-trailing arm IRSs under compression generally), effectively dialing in oversteer that makes the car feel agile by making initial cornering response faster, as the rears swing wide and build slip angle faster than they would otherwise. This is the sort of behavior that made classics like the VW Beetle, Corvair, and older Porsche 911s both a lot of fun, and rather dangerous at the same time. Above .5G side loads, or under braking or sharp engine torque, the DTSS bushing compresses to allow deflection of the hub, giving much safer toe-in. Seemingly the best of both worlds - until the rear tires are at the limit of traction.

What's the problem at the limit of grip? At-the-limit behavior in these cars has, as I mentioned, been characterized right from the get-go (pre-launch media track events) by a limit that is both hard to find (and skilled, experienced drivers are typically the ones who notice this most), and often accompanied by snap-oversteer. Why should this be so, if the system is designed to deliver safe, predictable understeer under higher cornering loads? Let's look at what is actually happening at the contact patch and with the chassis overall in at-the-limit driving.

At the limit of grip, what is actually happening is the tire is slipping at it's maximum angle relative to the "intended" path while generating it's highest g-loading to the chassis through the suspension. At mid-corner, throttle is typically fairly neutral, and there's usually no braking, so the other conditions that also trigger DTSS toe-in aren't present. DTSS should give the maximum rear toe-in at this point, which in turn should deliver reliable, and predictable feedback to the driver and a stable back end - the opposite of what what any experienced driver who drives these cars in competition conditions reports. The problem is with the assumption that cornering loads at the limit are a static input - maybe on a billiard-table smooth, steady-state skidpad, but in reality, the driver in a high-speed corner is constantly correcting line with throttle and steering inputs, and the tire contact patch isn't constantly at it's maximum effective slip angle - it transitions from grip and a working slip angle to outright sliding and back constantly.

This in turn momentarily unloads that DTSS bushing, allowing the hub to "dial out" the toe-in it's intended to have, and move from safe, predictable understeer geometry at the rear towards oversteer - the worst possible thing to have happen. And hence the snap oversteer these cars (and most cars with semi-trailing arm rears) are known for - but other cars like older 911's it's at least a fairly predictable oversteer, where the FC has that random element that makes it spooky to drive at the limit. The driver can be doing all the right things, but the unintended rear geometry change will betray him and put him in the weeds. Most drivers who think they're fast but only have limited track experience, or who are just inherently stay at 9/10ths and don't push for the real limit don't discover this.

Much as I hugely respect Icemark, RX-7 electrical god, may he RIP, I've never seen anything that shows these cars are faster on-track with working DTSS than without - and my own experience and that of many other racers says the opposite. Same goes for Jackhild's post saying competition drivers like myself are thinking we know better than Mazda's admittedly clever engineers. But it again comes back to what were those engineer's objectives - which were foremost agile, but ultimately safe handling for the street (see Jack Yamaguchi's book on the RX-7, or his technical analysis in the Nov. 1985 Road and Track for more on this). However, what works in typical-to-spirited street driving made for a car that has been a perennial under-achiever on track - at least until people started eliminating DTSS (now, they're mostly just under-achievers because they're 25-year old tech running against newer cars with more power and much better suspension geometry).

It's also fair in any case to ask if the engineers achieved their goals, or as many reviews of the FC even back in the day suggested, they over-thought the plumbing - and hence why both the Miata and the FD moved toward simpler, more fundamentally "correct" suspensions rather than try to make a silk purse of a sow's ear (semi-trailing arm IRS).

kustomizingkid

iTrader: (2)

So Aaroncake, did you get these installed, and if you did what is your opinion on them, how does the car drive?