turbofan

iTrader: (1)

Yeah, get a job and then talk to me.

jmann

Ed Talk to Eddie at AR there in Portland and get some of the ones I linked. He can explain it better maybe then I did. The idea behind the urethane or delrin bushings are not only to harden up the suspension but to remove the increased spring rate that stock bushings cause. The rubber on stock bushings is molded to the inner and outer sleeves and the inner bushing has teeth on their ends that the big washers clamp onto and when the inner sleeve is moved with up and down motion in the arm they twist the rubber which increases spring rates.
Some want the spring rate to be more true to the rate of the springs and the suspension arms to be free moving. With the urathane and delrin setups the inner sleeve is lubed so it rotates inside the bshg.Unfortunately either system works only as long as the lube is kept in working order. Some have tried zerk fittings and other means with iffy success. The best setup is heim joints and there are some people working on making arms that way.
But as for getting more neg. camber the bshgs from MR well work just fine. Call Eddie.

aidandj

iTrader: (5)

The group buy was set up by Greddygalant, an employee at AR, and who talks to Eddie about all that stuff. The sperical bushing thread that was around lately has a lot of good info in it too.

jmann

I know Martin very well.

turbofan

iTrader: (1)

Indeed you do I don't know the setup I'll finalize on. But I'm going to go ahead and begin installing poly bushings in the rest of the car over the next few weeks while my car is at the body shop, then full subframe swap.

ANYWAY... RC1's, anyone?

Seefo

iTrader: (5)

Either you are missing words or you are wrong on a lot of this stuff. I think you mean to say is poly bushing's "spring rate" is higher than a rubber bushing's. If that is the case, then please make sure you clarify, because right now, you are implying that rubber bushings increase the "spring rate" of the car over a solid bushing. This is just not true, a solid bushing has a "spring rate" also, its just extremely high in comparison. This means the deflection in the bushing is reduced, allowing those forces it to go through your shock+spring, vs. being absorbed in the rubber bushing.

I think maybe what you meant to say is rubber bushings have increased displacement, when compared to urethane/solid bushings.

turbofan

iTrader: (1)

Sorry Joe, John is right.

The rubber bushings bind and make it so the control arms take effort to move. Take your shocks off and try to move your control arms with the stock bushing. You'll notice that they take a lot of effort still to move them up and down and they spring back into place when you let go.

With a lubricated poly bushing, the bushing does not affect the movement of the control arms, allowing more precise control of spring rates. This is what john is saying.

aidandj

iTrader: (5)

Yet it has been proven and discussed that the lubrication necessary for poly bushings to stay like that is not an easy thing to accomplish. Bundy talked about the grease never lasting, or burning up. Delrin supposedly doesn't need grease, but it also wears really fast.

This thread talks about all this stuff in depth: https://www.miataturbo.net/race-prep...ushings-81552/

and

https://www.miataturbo.net/race-prep...cussion-82072/

aidandj

iTrader: (5)

Couple good quotes from there:

jmann

Thanks Ed
Lubrication is an issue on poly or delrin bushings as I stated. Bob drives his car on the road alot in weather. We have talked about this. The statement was made above that there was no offset bushings for the lower arm and I was just saying that there is and they have worked fine for me to gain neg. camber up front. I have stock bushings everywhere else so if they bind up a little with time I don't care, they well be just like the stock rubber ones.
Until someone comes out with the heim joint ones which well truely work freely I don't want to spend the time nor the money for something that in time isn't much better then stock.

turbofan

iTrader: (1)

^yup.

Poly obviously has drawbacks, but you'll notice that in the end of that thread Bob has found a lubrication solution that allows the bushings to be lubed once per autoX season. That sounds pretty fantastic and totally acceptable to me.

So copper permatex it is.

Seefo

iTrader: (5)

I understand that stock bushings "bind" since they are physically bonded to the metal sleeve(s), but if you think about the displacement at the wheel vs. the force applied, its going to be more displacement with a rubber bushing vs. a solid bushing. The force applied will compress the spring/shock and deflect the bushing slightly. That bushing deflection won't happen with a solid bushing (or really be a lot less).

Am I wrong there? If not, that means the overall stiffness of your suspension system is higher with solid bushings vs. rubber. Sorry if that's not what john was referring to in the beginning, I probably misunderstood.

anyways, sorry about the thread jack.

hornetball

iTrader: (4)

You're confused about this.

Poly/delrin/heim joints aren't "solid." They're designed to pivot, and the less friction they have the better. When they do have friction, the effect isn't to return to a "center" position like a spring, rather they just resist movement like a shock -- a really bad shock with inconsistent and unpredictable resistance.

OEM rubber bushings pivot rather awkwardly due to being soft and want to return to the position they were in when the suspension bolts were tightened. Anyone who has ever made the mistake of tightening the bolts on an unloaded suspension with OEM rubber bushings knows this. The effect of rubber bushings is often described as "adding spring rate" although the effect is too inconsistent to be useful.

jmann

lets try this again. Unlike the oem bshg that the inner tube is molded into the rubber bshg and it has teeth on the ends that the washers on each end tightens against as you tighten the bshg bolt, so as the arms move up or down it twist the bushing which in turn twist the rubber as it is molded together. The poly has the same inner sleeve with teeth on each end that the same washers tighten up against, but the inner sleeve is not molded to the bushing. Instead it is lubricated on the outside of the sleeve where it rides in the poly bushing and when the arms move the inner sleeve rotates inside the poly bushing if kept lubed properly.

turbofan

iTrader: (1)

Joe I see what you're saying -- that's not at all what we are talking about. yes there's going to be much less deflection with Poly bushings, and even less deflection in delrin bushings. But deflection has nothing to do with spring rates, it's simply how firmly the control arms are being held in place during braking (and, in the rear, acceleration) events. It will be affected by spring rates, but it won't really affect the spring rates.

Mobius

iTrader: (2)

Durometer != tendency to inhibit rotation

jmann

One more time. The after market bshgs are different in two different ways. The polys are harder so there is less cushioning as far as absorbing bump which in turn makes for a harsher ride, this has absolutely nothing to do with what the other purpose of the poly bshg is and that is freeness of the arms to move up and down as the inner tube is lubed and floating free inside the bshg. The bshg bolt and the washers tighten down on the teeth on the ends of the inner sleeve not the rubber or poly bshg as many seem to think is the case, so with the inner sleeve on the poly being free to rotate as it is not molded to the bshg like the rubber one is it is free to rotate as long as it is lubed.
Two different things here. Kinda like a harder bump stop on a shock verses a softer one has nothing to do with the rate of shock travel, that is controlled by the dampner setting.

NiklasFalk

iTrader: (1)

Split to a OEM rubber explanation thread..?
For a poorly maintained setup bonded rubber is hard to beat, the bushings give some torsion spring rate, but close to no binding/stiction. I.e. predictable movement for applied force.
A poorly lubes poly bushing can require some force to get moving, something you don't want, since the force/movement isn't linear (or smooth curve).
I've been shot down before for suggesting bronze bushing sleeves between the Poly/delrin and the center sleeve. But it would remove the binding issue and reduce the wear of the bushing material.

hornetball

iTrader: (4)

Many? Only 1, and now 0. /end (please!)

aidandj

iTrader: (5)

Curly doin work.