T/c Kit For S12 From Experimental Engineering

[Mr.510]

I was ripping some parts off of a wrecked VG S12 today and noticed the tension/compression rod bushings and washers looked very similar to the ones on the 510 and Z cars. A quick call to my brother the Nissan parts guy confirmed that they are, in fact, the same parts as is the steel sleeve inside the bushings. I pulled off the passenger's side mount complete with original T/C rod and bushings and brought it home.

T/C Kit: I have produced a UHMW / aluminum ball & socket assembly to replace the forward rubber bushing in 510s & Zs for at least 15 years. The 'T/C Kit' as it's known is usually the first handling modification done to any of these cars. It's a cheap, easy way to make a major difference in the handling of the car, especially under heavy braking. What it does is eliminate ALL fore-aft movement of the front wheel under braking and cornering loads. This is done by replacing the forward rubber bushing with a mechanical joint. The rear rubber bushing does not need to be replaced unless it is cracked and at risk of falling out. This is because all the rear bushing does is apply pre-load to the T/C Kit's ball & socket to keep it from rattling. The rear bushing is NEVER compressed further except while braking in reverse, and it handles that just fine.

Rubber bushings: With stock rubber bushings when you step on the brakes the forward bushing compresses and the wheel moves rearward. In a panic stop on sticky tires the front wheels can move rearward 3/4 of an inch as each tension-compression rod sees between 1000 and 1200 pounds of force. As the wheels move rearward castor is lost making the car more "darty" and less apt to go straight. The toe also changes significantly so the front tires are no longer pointing the same direction. There is about 500 pounds maximum rearward load on the front T/C bushing while cornering. Again, this moves the wheel rearward reducing the castor and messing up the toe. None of this is good!

Polyurethane: Many people replace all of their stock bushings with polyurethane. Poly bushings are considered a good upgrade as they deflect less but are not as harsh as spherical bearings or other metal-on-metal joints. The car feels 'tighter' and the wheels stay pointing in their proper directions much better with poly than with rubber. Poly bushings still deflect under load, but not nearly as much as rubber due to their higher density. Poly bushings are great in all rotary applications like upper and lower control arms, sway bar pivot bushings, etc. They also work well where they are only loaded in compression and there is very little binding movement. An example of this is sway bar end link bushings. Poly bushings work great here. Tension-Compression rod bushings are NOT a good place for poly bushings and here's why: They increase the loading of the T/C rod itself as it pivots. The stiffer the T/C bushings the worse the binding making the T/C rods flex. The more they flex, the sooner they break.

T/C Rod Breakage: When a T/C rod breaks at speed the front wheel stuffs into the firewall, locks up, and jambs the steering! I once broke a T/C rod on corner entry at serious speed in my 510 and am lucky to be alive. I'd been canyon racing for hours on some twisty mountainside shit with epic drop-offs on one side and boulders on the other. I flicked the car into a left-hander at about 70 in 3rd gear with a serious dose of left-foot-brake and the hammer down. There was a loud 'POP' and it felt like someone hit the steering column with a sledge hammer. My instant thought was broken crankshaft as it was so violent. The RF tire immediately locked against the firewall and the steering wheel would not move. I let up on the brake but the wheel stayed locked and I could not steer. I snapped the throttle shut and thankfully the car pivoted on the locked front tire and turned ninety degrees sideways, passenger's side leading. At this point I was 'along for the ride' so I instinctively pushed in the clutch and drug the brake a bit. I left the tarmac at about 40mph sideways traveling in an arc about double that of the corner. I could not see anything the direction I was going and presumed it to be a drop off. I took my hands off the steering wheel, snicked it into neutral, and pulled my feet back against the front of the seat. One thing you learn growing up in a racing family is to never 'brace for impact'! Pull your extremities in, exhale, and wait for the hurt. It was eerily quiet now. After what seemed like five minutes of near silence except for the rough idle of my L18 my ears exploded with the sound of gravel shoveled into the right side fender wells. The car pivoted hard around the RF tire as it dug in and I spun 270 degrees coming to rest in a cloud of fury. Bap, bap, bap, bap my trusty SSS motor was alive, at least the crank wasn't broken as I'd initially thought four seconds/five minutes ago. I had come to rest in the loose crushed rock driveway of a gravel pit. I could see that there were enough rocks on the hood to fill a gallon bucket. There were rocks on the roof too, but I didn't know that yet. This particular switchback was the only one on the whole road that had any runoff at all and I could not see that as I entered. Good thing I'd stopped to piss about ten minutes before or I'd have needed a change of clothes and a tow truck. As it turned out there was very little damage: One T/C rod and associated hardware, one sway bar end link, one tire, the finish on both right side wheels, and a dozen nasty rock chips in the side of the car. I was beyond lucky. If this had happened on entry to *any* other corner on this road the result could have easily been fatal.

Fitment: It turns out that my existing T/C Kit is a perfect fit for the S12. It drops right in and works perfectly.

Binding load test: I had always wondered how much easier the tension-compression rod moved with a T/C Kit installed but had never bothered to do a 'scientific' comparison. In a 510 or Z this would involve some form of testing under the car as the mounts are welded in. This S12 chassis mount presented an easy opportunity. I set up a quicky comparison with the S12 T/C assembly clamped to my work bench. Here are some pics of what I found:

This is the assembly, as pulled from the car, clamped to the bench:


This shows the hammered stock bushings, with the gauge that's supplied in my T/C Kit as a reference for how far the bushings are compressed. Note that in stock form there is a steel sleeve between the two big washers so the bushings cannot be overly compressed:

 
I zip tied a tape measure to a piece of flatbar so it could hang off the bench for comparative measurements. Here the stock tension-compression rod assembly is sitting static with nothing touching it and I "zeroed" the tape:


Next I hung the nearest heavy thing I could find lying around, a VG30 starter, from the end hole of the T/C rod with a piece of bailing wire:


The tape measure shows 7/8" (22.2mm) of movement.


Next I removed the stock nut, forward washers, forward rubber bushing, and steel sleeve from the T/C rod. Then on went the UHMW ball with the flat side against the chassis mount and the centering step in the hole. It is not a tight fit tight as play is required so it can self-align. Then the aluminum cup, washer, and supplied nut went on.


The standard hex nut is used to set the pre-load using the supplied gauge as a guide. When the gauge just slips over the big washer at the rear and the aluminum socket housing at the front the stock locking nut is screwed on and jambed against the first nut so it cannot come loose:


I slid the tape measure back out and it's still "zeroed":


Adding the weight it's obvious this thing pivots MUCH easier than even stock rubber bushings!


2-15/16" (74.6mm) of movement. Wow, I had no idea a T/C Kit freed up the suspension *that* much!


More for next time: I wish I had some poly bushings on hand to test against what I did here. Since my broken T/C rod experience I have never run poly T/C bushings and threw away any that I had. I've ordered new rubber T/C bushings from Nissan and will get some of the various Poly bushings that are on the market and do a more scientific binding test as well as an axial loading test using my press so we can see how much each lets the wheel move under a given load.

Price and availability: My T/C Kits are $28 and include all the parts to do one car plus detailed instructions and the pre-load gauge. We have them in stock. For ordering it's best to contact my friend Carter that handles all the sales directly at: sales@vg30.com

[inxss12]

Thanks Mr. 510.
That was my first upgrade on my dime, now I will have to do the same on the S12.

[Wolf Dilworth]

Dave

I will be calling Carter in the morning for a couple of sets of these.  Just posted pics on my thread of your headers.

Peace, Wolf

[demonic s12]

Dave

I will be calling Carter in the morning for a couple of sets of these.  Just posted pics on my thread of your headers.

Peace, Wolf

call me a noob, but what benefit would these have? what would i expect to feel differently?

i have a pair of tension rod brackets sitting loaded with urethane, so im wondering if i should consider these.

[Wolf Dilworth]

call me a noob, but what benefit would these have? what would i expect to feel differently?

i have a pair of tension rod brackets sitting loaded with urethane, so im wondering if i should consider these.

They move much freer than Urethane. there is no loss of caster under braking loads, due to rubber/urethane bushing flex. Urethane has been known/blamed for premature failure of TC rods since the rod can bend under large loads. Too many cycles back and forth (up/down)... and snap.

However, there will be more road noise transmitted with the ball cups. But I like to listen to my machine, so...

{forgot to add}
what would i expect to feel differently?  No tow changes under hard braking, more solid feel in corners.



Peace, Wolf

[Xano]

this makes me happy, i cant believe i didnt notice this post yet.

All 3 of my S12's have had shot bushings and the metal cup is usually pretty rusted the hell out on em too.  i may get some of these when i come across money...

[Mr.510]

Cool, thanks guys! I can't believe that over the course of 15+ years I never checked to see if they'd fit S12s and Z31s! To answer an above question the thing you'll notice the most after installing a T/C kit is that the car will go straight under heavy braking. I can dynamite the brakes in my dime at 100mph and the car will stay in a lane without me touching the steering wheel. Without a T/C kit you can't even let go of the wheel at 100 unless you want to meet Jesus.

[David B]

wait is this fur sale

[Maxpow]

Price and availability: My T/C Kits are $28 and include all the parts to do one car plus detailed instructions and the pre-load gauge. We have them in stock. For ordering it's best to contact my friend Carter that handles all the sales directly at: sales@vg30.com

.

wait is this fur sale

.

[SlickS12]

Favorited  waiting for money i can spend on ol dusty then maybe these will be next.  

btw, Im planning on running a front suspension made up of 12,13,and 14 stuff, could I use just stock 13 t/c rods along with this on the 14 brackets?

[Jay]

Favorited  waiting for money i can spend on ol dusty then maybe these will be next.  

btw, Im planning on running a front suspension made up of 12,13,and 14 stuff, could I use just stock 13 t/c rods along with this on the 14 brackets?

No, S13 T/C Rods look like this.


Modded factory on the left, Cusco in the center, And factory S13 on the right

[sam31183]

I bought these today at the Canby Oregon Datsun meet...I am really curious to see what kind of a difference these are going to make on the car!

[Mr.510]

I bought these today at the Canby Oregon Datsun meet...I am really curious to see what kind of a difference these are going to make on the car!

I wasn't able to go to Canby as I severely sprained my ankle a month? ago and still can't stand or walk very much. Thankfully Carter & Brenda went. Please post your impressions of what effect the T/C Kit has on your car and it's handling!

[sam31183]

I will be sure to! I think I saw your post on ratsun actually about not being able to walk now that i think about it...i just registered over there...datsun guys are soo cool lol. (i didnt mean the cool part sarcastically btw, i just felt like laughing)

[Arro]

Can you provide the measurements on that silver c-plate? the inside measurement I mean.

[Mr.510]

You mean the gauge used to set the pre-load when you install the kit, right? If so it's 2-1/4". If you need one PM me an address and I'll mail it to you.  

Can you provide the measurements on that silver c-plate? the inside measurement I mean.

[sam31183]

my white bushing cup wont slide down to the bottom of the tension rod...did you guys test this on just mk2 s12 tc rods? I am not sure if the inner diameter is bigger...i will take a pic in a couple of minutes to show how far down i can push it....

[sam31183]

the lip it is catching on is where the threads on the tc rod end...it wont slide down so the lip can fit inside the chassis cup.



I thought I would try to tighten down the metal cup over it to see if i could force it onto the non threaded part to get it to sit inside the cup...but it tweaked the white plastic bushing some.







like i said...i am not sure if the tc rods are bigger on mk2 or mk1...but it wouldnt make any sense for that to happen...when you guys test fitted this onto an s12 did the plastic bushing just slide down the tc rod???


update, i emailed off the experimental engineerings website email info@vg30.com and i got a quick response back from carter...on a sunday no less. the larger part on the tc rod end is actually a metal sleeve that you need to pull off with a set of like vice grips...i missed that part in the instructions though...so i go back out there and bam, bushings are now installed! These guys are for real though with answering my dumb tech question on a sunday no less! As soon as i get to go toss this thing around some I will let you know how well these bushings do their thing.

[Mr.510]

I'm glad Carter was able to help you figure it out. Over the years several people have missed the 'remove the sleeve' step in the instructions and asked WTF? so you're not alone. Per your question to Carter the toe shouldn't change much, if at all when you install the T/C Kit. If the stock bushings are really hammered it will change a teeny bit, like 1/32". Enjoy!

[xxstreetbikesxx]

im buyin it as soon as i finish my turbo..

My bushings are totally shot and crumbling