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If you could be a Honda trailing arm bushing...what brand would you be?

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If you could be a Honda trailing arm bushing...what brand would you be?

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Old 01-26-2010, 07:28 PM
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Default If you could be a Honda trailing arm bushing...what brand would you be?

You'd be a set of Brian Slames new offset PCI TA bearings, since if you were just one you'd be useless.

So if you have followed the threads relating to the understanding of the rear of those Honda chassis' resembling the DC2 Integra, you know that the rear end was engineered to steer itself in the direction of understeer "for your protection". A couple of those threads were these:

https://honda-tech.com/forums/showth...hlight=rr98itr

https://honda-tech.com/forums/road-racing-autocross-time-attack-19/how-rear-end-dc2-chassis-works-against-us-606414/

Using a spherical TA bearing floating laterally on a bushed shaft (like Brians original version) eliminates that component of dynamic toe in associated with the fore/aft compliance in the stock TA bushing - a good thing. But you're still stuck with the stock geometry and some remaining unhelpful toe in in bump and toe out in droop. About that, in that latest thread on the subject, in response to a question "why would the factory design it to toe out in droop?" I answered that it does that because we're running lowered and hence not at zero on the factory curve. Well, I was wrong about that. The stock geometry measures out, net, to pull the nose of the TA inward from full droop to full bump, and so consequently the reverse on the way back. This IS curious - but it's just the way it is, owing to either intent or compromise. But if you were on the brakes the aft compliance in the factory TA bushing would toe it in. Where you'd be in more trouble would be if you entered a turn hot and pitched the nose down (and rear up) with a throttle drop - a highly unlikely scenario in almost any street car situation. I know that when I've fooled around on a cool down lap or a warm up lap and done that very thing the rear swings out wildly, so I believe I'm more than speculating.

OK, so Brian has a new version of his TA bearing setup out now - it's got the bearing offset in the carrier, which effectively raises the nose of the TA and flattens out the toe link at a racing ride height, slowing down it's contribution of "in".

Just as an aside, maybe you've seen JDM versions of a spherical TA bearing where the bearing is fixed on the shaft and the toe link is dispensed with? Generally speaking, such a setup will, based on the change in the LCA lateral length component, have a very pronounced toe "out" in bump and droop too depending on the geometry and ride height (it's complicated and not germaine to this discussion to go further). That's why they call the toe link the "compensator". I don't think I'd even consider such a setup unless I were just autocrossing, or if I were running spring rates in the range of immobilization.

Back to the new PCI offset setup. Brian has done his usual great job of making life easier on the user, and given us some tuning range. The new shaft has the mounting flats machined offset. So you can install it with the shaft centerline higher than stock or lower than stock, either adding or subtracting from the offset in the bearing carrier.

The low offset position gives a toe curve that I measured thus:

Hub Center to Fender Lip xxxxxxxxx Single side toe on 12-inch center

11.5 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx .004 out
12.0 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx .002 out
12.5 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx .000 xxx (static ride ht)
13.0 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx .001 in
13.5 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx .002 in

For the high offset position:

Hub Center to Fender Lip xxxxxxxxx Single side toe on 12-inch center

11.5 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx .025 out
12.0 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx .014 out
12.5 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx .000 xxx (static ride ht)
13.0 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx .008 in
13.5 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx .020 in

In reality there's got to be some uncertainty about that third decimal place, but that's what my dial indicators gave me. So the low offset position gives the more zero-ey curve, and the high offset position gives you a faster curve - though not terribly fast, which is probably fine since we're toe-ing out.

So what do we get? On the brakes going straight not much, less toe in than stock. Start coming off the brakes and start turning in, the rear starts to come down - the outside more (toe-ing out toward the zero point?), then you're about off the brakes and the outside rear is carrying all the rear weight so it's got about double the static deflection less that associated with the the bar force (toe-ing out toward the 12.0 toe value?), then on the gas so some more weight from the front (toe-ing out toward the 11.5 toe value?)

Seems to me that you could start out on the low offset position and fool around with the rest of the car, and if you felt it necessary you could flip the shafts and get a little more help from the rear end. The droop figures look useful in terms of their effect on drop throttle behavior - promoting docility.

Regarding the installation - I had to grind about all of the vertical rib off the TA to get clearance in the high offset position, and had to grind a nice radius rearward of the highest point on the TA to get clearance at full bump. Not sure if you need to do any grinding for the low offset position - a small interference will "correct itself"... The outside plate seems to self clock the housing as you tighten it down.

Conclusion - Thank You Brian for saving me from having to develop and produce a set of these for myself. At the street price of these things a person would have to be "F...... Retarded" to do anything other than to call their favorite vendor and order up a set.

Scott, who likes honest parts that do what we need them to do...and who will be on the lookout for what's next from PCI...

Last edited by RR98ITR; 01-26-2010 at 08:09 PM.
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Old 01-26-2010, 07:55 PM
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Default Re: If you could be a Honda trailing arm bushing...what brand would you be?

Nice write-up
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Old 01-28-2010, 07:37 PM
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Default Re: If you could be a Honda trailing arm bushing...what brand would you be?

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Old 01-29-2010, 02:02 PM
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Default Re: If you could be a Honda trailing arm bushing...what brand would you be?

where can i find pictures of the new offset units?
-spenc....reading rules way too much this week
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Old 01-30-2010, 02:41 PM
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Default Re: If you could be a Honda trailing arm bushing...what brand would you be?

Here you go:
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Old 01-31-2010, 05:52 PM
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Default Re: If you could be a Honda trailing arm bushing...what brand would you be?

Considering that you have zero experience with said spherical RTAs and how they work, your conjecture is null and void. J/k.

I'm not an expert but it's my understanding that the RTA bushings mentioned by the OP allow less restriction for the RTA to move in and out as the RTA moves up and down. Which I would think is a good thing.
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Old 01-31-2010, 05:56 PM
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Default Re: If you could be a Honda trailing arm bushing...what brand would you be?

Originally Posted by court76wi View Post
Oh man, huge debate item. My weak 2 cents, and I'll probably get blasted for it. This is from AutoX experience in my CRX, and I've run both rubber and poly. And my experience might not be as extreme on longer wheelbase vehicles.

I would be a hard rubber OEM style bushing or similar (Mugen, etc.). Period, end of story. Some things are meant to be pliable. Most of all the front compliance bushing and the large, rear trailing arm bushing. Keep those rubber. Have a blast with everything else.

Why? Well first throw away all the high-tech calcs, suspension, and toe issues and focus on the feel of the car. (that was some nice info by the way) With rubber you have motion, rotation, and flex in all three axis. The more travel in the rear trailing arm bushing the better the feel of the car.

My experience with rubber. Oversteer or a loss of control in the rear is easy to predict and you can feel it well before it happens. And if it does happen you can play with it and use it, and correcting the condition is easy and possible.

My experience with poly. Oversteer in the rear is hard to predict and you generally have what most people refer to as "snap" oversteer. Recovery is very hard and nearly impossible if you don't react right away. Non-AutoX experience, I had to make a quick stop on the interstate once (quick, not fast, and in a straight line) in my CRX and I almost crapped myself. The back end of the car felt like it wanted to catapult itself over the front of the car. Poly was immediately gone after that. Some people will use poly for the rear trailing arm as a "hack" if their car doesn't rotate that well I wouldn't recommend that.

My experience with spherical. Don't have any, but it can only be worse than poly. It frees up some more movement than rubber or poly can provide and in some cases more than the original suspension was designed for (which can be bad), but it takes even more movement away. And I'd prefer my car not to feel like an unloaded dump-truck whenever I run over a pebble. Poly in every other place besides the two I mentioned above is worse enough in both my CRX and Integra. If you ever run on a rough track spherical bushings will probably be the end of you, if you can even keep the car on the road. The more rigid the suspension, the less control of the car you have over imperfections and other non-ideal situations.

If you want the ultimate go fast, the harder the bushing the better. If you prefer less of chance or wrapping your car around a tree or running it into a concrete wall then stick with rubber for the rear trailing arm...
Im just curious of the age and installation procedure of the poly RTA bushings you had. Were they lubed and clocked?
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Old 01-31-2010, 06:50 PM
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Default Re: If you could be a Honda trailing arm bushing...what brand would you be?

I personally went from stock rubber, to hard rubber, then to spherical RTA bushings and I prefer spherical. I have no first hand experience with poly RTA bushings; however, looking at their design it would seem they would restrict inward and outward movement as the RTA traveled up and down (not to mention any other direction the RTA needs to travel), which I believe is a bad thing. I guess my opinion of poly RTA bushings here would be "null and void" lol.

>>So if I were a trailing arm bushing I would definitely be spherical.
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Old 01-31-2010, 09:24 PM
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Default Re: If you could be a Honda trailing arm bushing...what brand would you be?

've got to say I've never heard more such certain statements about somethings from some one that has no experience with it.

In theory and application spherical bearings are the best.

Poly is horrible it causes binding. My cars twin, in most respects, went with poly against my advice of just leaving rubber in. After 5 or so weekends he said 'ok I'm not rusty anymore.. But damn this car is sketchy just not confience inspiring.'. After much debate he finally convenced me to drive his car. I drove it and immediatly felt what he was talking about.. He took my car out and said THIS is what the car should feel like!!!

We put it up on jack stands and YEP poly bushings where the only difference. He tosed them and put oe rubber back in, loved the feel and went faster.

Rubber is ok it allows some movement, does bind, but is to mushy.

Spherical bearings THE BEST. You get the movement WHERE you want it, with no binding, and NO movement where u don't want it.

The two areas where you say are the worst to put SB are actually the best.

The front compliance bushings allow a whole lot of slop and no real feed back in the steering wheel. Esp at turn in. Swaping these out to SB made a huge diffence. One of the downfalls of the EG/DC front suspension is that compliance bushing. The EF/DA have an easy fix with the radius rod SB. The eg/dc isn't so easy, but it can be done.

SB are an advantage, if they wherent then you wouldn't see class rules allowing/not allowing them. Look at 'real' race cars, ALMS, Grand-Am rolex, WC TC/GT pre 2010. They all have SB every were. And its not because they are bad..

Last edited by slammed_93_hatch; 01-31-2010 at 09:55 PM.
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Old 02-01-2010, 06:04 AM
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Default Re: If you could be a Honda trailing arm bushing...what brand would you be?

Bumpy roads/tracks should primarily be concerned with shocks, not TA bushings. If you're accounting for the TA to control some of those bumps, I think you're doing it wrong.
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Old 02-01-2010, 09:07 AM
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Default Re: If you could be a Honda trailing arm bushing...what brand would you be?

Originally Posted by Stinkycheezmonky View Post
Bumpy roads/tracks should primarily be concerned with shocks, not TA bushings. If you're accounting for the TA to control some of those bumps, I think you're doing it wrong.
Nah, I was referring to the suspension as a whole. All rubber, vs poly, vs spherical. I'll just pull out of the conversation...

Last edited by court76wi; 02-03-2010 at 02:46 PM.
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Old 02-22-2010, 02:12 PM
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Default Re: If you could be a Honda trailing arm bushing...what brand would you be?

Just wanted to post some pics of the install and related after-grindage:

Overview
Clearance at ride height at low offset
Bottom/back at ride height at low offset
Clearance at ride height at hi offset
Clearance at 2 inch bump at hi offset
Bottom/back at 2 inch bump at hi offset
TA with rib ground

Scott, who hasn't figured out how to fit captions in between pics...
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Old 02-22-2010, 02:55 PM
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Yo! That is some light-*** thin body shock in that first pic! Or is that a zero-coil, 100,000 lb spring???(Must lookup the tensile strength of steel again)
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Old 02-22-2010, 03:06 PM
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That's my prototype pull-rod setup...I'm still sorting out the basic physics (positive/negative sign...tension/compression...that kind of thing).

Scott, who has a friend who bump steered his car with a forklift, some chain, and his eyeballs...I'm more towards the Monk end of the scale...
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Old 02-22-2010, 03:20 PM
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Default Re: If you could be a Honda trailing arm bushing...what brand would you be?

RR98ITR, thanks for sharing pictures. So which setup do feel is more advantageous, low offset or high offset, for your purposes?

I've have the non-offset PCis on my car for over three years and was wondering if it would be worth it to change them out for the latest offset, version.
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Old 02-22-2010, 03:36 PM
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Default Re: If you could be a Honda trailing arm bushing...what brand would you be?

Originally Posted by 98SpecR View Post
RR98ITR, thanks for sharing pictures. So which setup do feel is more advantageous, low offset or high offset, for your purposes?

I've have the non-offset PCis on my car for over three years and was wondering if it would be worth it to change them out for the latest offset, version.
I can't say, I don't have any experience to share yet. I had the non-offset PCI bearings on my car for a couple of years too, and you know how it is when you see something that's theoretically and obviously better, and modest in cost - you just gotta do it. I'll start out with them in the low offset position with the more zero-ey toe curve and see what I see, and then regardless of what comes of that I'll try the high offset position just to see.

Scott, whose "purposes" currently consist mainly of someday getting the car off those darn jackstands...
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Old 02-22-2010, 04:20 PM
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Default Re: If you could be a Honda trailing arm bushing...what brand would you be?

Scott ... Your R is a bit dirtier then I expected. Esp considering it just sits around being measured.



I really like the PCI offser TA bushing. But, my new best friends are these parts for the front end. Combined with the PCI part, they have totally transformed my ITS GSR.



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Old 02-22-2010, 04:43 PM
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SPiFF, have you ever used the non-offset PCI RTA bearings?

Your compliance bearings definitely have my attention. Info?
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Old 02-22-2010, 06:30 PM
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Originally Posted by SPiFF View Post
Scott ... Your R is a bit dirtier then I expected. Esp considering it just sits around being measured.
A Masterful Burn I must say...

Scott, who did get the car dirty by driving it alot...but not so much lately...
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Old 02-22-2010, 08:21 PM
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Default Re: If you could be a Honda trailing arm bushing...what brand would you be?

In as well for info on the various front end bushings/bearings.

In terms of the RTA, I've been very happy with my Hardrace sphericals. Never thought I might need the offset thingies.
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Old 02-22-2010, 08:31 PM
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Default Re: If you could be a Honda trailing arm bushing...what brand would you be?

Scott, are you going to test the car with high offset as well? I'd love to hear what's your take on it. I've been trying to get rear toe out under bump on my rear tsx to help rotation. This enable me to run softer spring rate and get the tire and suspension work better and much more controlable on the bumpy track. Which I feared at first will upset the rear of the car under bumpy condition, but I don't even feel it.

Who makes the front compliance bushing there? Looks similar with what I made few years back when I ran the civic (ek) with eg subframe. Did a few design change, first with set screw holding it in place that only last a few weekend before it slides around. You definitely need to weld the housing to the sleeve.

This is one me and Brandon from Redzone performance made for ek subframe. All stainless construction.


I do think bearing is not necessary on this and a budget fix is an easy to make yet durable delrin.
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Old 02-23-2010, 07:59 AM
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Boy I love to hear things like that Andrie..."but I don't even feel it".

We all, ok just some of us, worry about some of this stuff and I'd bet sometimes we even convince ourselves of things we really just imagine. I guess that's why we need a theory on our side.

Nice goody pics too.

Scott, who tries not to want pretty parts when ugly parts will do...but lookout if they're better, lighter, or any other er...
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Old 02-23-2010, 10:38 AM
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Default Re: If you could be a Honda trailing arm bushing...what brand would you be?

I was one of the "ideamakers" behind the PCI ones. they work great. Make sure you have your toe link as long as possible ( like in the pic ) that way there is less angle created and thus less toe change
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Old 02-23-2010, 10:53 AM
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Default Re: If you could be a Honda trailing arm bushing...what brand would you be?

Scott,

during testing, you'll have to be honest with yourself. If you can't feel it, then you can't feel it. But it is not end of the story. There maybe miniscule improvements that you can see by averaging lap times throughout 20 min runs or more. Of course assuming those laps are good laps and not impeded in any way
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Old 02-23-2010, 12:28 PM
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Default Re: If you could be a Honda trailing arm bushing...what brand would you be?

Originally Posted by 98SpecR View Post
SPiFF, have you ever used the non-offset PCI RTA bearings?
I have not. I had Mugens on the car before the offset PCI stuff.

Originally Posted by 98SpecR View Post
Your compliance bearings definitely have my attention. Info?
They were prototyped on my ITS car by Chris Brinson. Chris is one of the original ECHC guys. Very nice CNC work to precise tolerance and IT/HC legal. He has the final parts made up for sale now. cbrinson---at---hondaprelude---dot---com is his email.

Originally Posted by Andrie Hartanto View Post
Who makes the front compliance bushing there? Looks similar with what I made few years back when I ran the civic (ek) with eg subframe. Did a few design change, first with set screw holding it in place that only last a few weekend before it slides around. You definitely need to weld the housing to the sleeve.
Nice parts. Not IT legal (and maybe not HC legal, but it has been a while since I looked at the rules). The sleeves are welded. The pics I have were of the first run hot out of the CNC machine.

Originally Posted by Andrie Hartanto View Post
I do think bearing is not necessary on this and a budget fix is an easy to make yet durable delrin.
These parts did a lot for my car. I had full delrin setup up front and the Mugen RTA. Changed to a full Brinson spherical kit up from and the PCI RTA. The difference was big. Most noticeable was in higher speed transition sections, like Road Atlanta turn 2-3 complex.
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