Howard Coleman

iTrader: (6)

how do you think your FD would handle if i removed the front solid steering link rod-ends and the solid u-joint from the steering rack and replaced both joints with a big fat rubber bushing? answer: no road feel (just like power steering which you have already removed) and all over the place. undriveable. sort of like a ford LTD. but that is exactly what the stock rx7 runs in the rear. independent rear suspensioned cars require a steering (toe) link to maintain proper rear wheel direction. (solid axle cars do not as they are locked in by the axle/bearing.) as we all know the toe link is adj and it is here we address rear suspension toe alignment. so the toe links steer the rear wheels just like the front steering rack only with big fat rubber bushings. since the toe links carry no chassis weight (except a smidgeon in turns) there is no reason for them to be rubber. make no mistake about it when you get on the gas or brake your rear wheels are deflecting from the fronts. no wonder the toe link bushings wear out first. even if you jack up the rear and yank on your rear tires at 3 and 9 o'clock and detect no movement when you hammer the gas or brakes your wheel path changes resulting in non linear rear wheel steer and slower everything. if you are a savvy road racer you know that fast is softer in the rear for a rear drive car but soft (as in rubber bushed toe/steering links) when it changes wheel alignment is slow. so find yourself a set of toe links (w rubber rod--end covers) and drive a car for the first time with all 4 wheels pointed in the right direction.
howard coleman

cover8

where do you get the rod end covers?

DamonB

Only the inner toe link bushing has any rubber in it and there isn't much. I would also point out that you still have at least 16 rubber bushings in your suspension arms unless you have replaced them with something other than stock, and each of those 16 have several times the amount of rubber as the stock toe links do.

If the stockers are worn, it's a problem. If they are not worn I will bet you can't tell the difference between the stockers and solid aftermarket types.

DamonB

cover8, here is my original post on the subject.

aftermarket toe links

Chronos

I read that when you replace the original OEM rubber bushings with polyeurothane (spelling?) and the toe-links and trailing arms with the M2 units, the drivability and confort are seriously hindered. The car no longer "feels" stable since you're getting all that feedback now. It's most likely a very bumpy and twitchy ride.

I suppose the mods are almost a must-do mod for road racers and sorts but it does seriously compromise regular driving...I guess is just depends what you want. As for me, I'm definately not ready for such a mod that will decrease overall drivability so much.

All of my facts however are just re-hash from my memory...Anyone actually running the fore-mentioned units wish to add some input???

DamonB

The rubber is there for vibration and noise isolation. That's why when any toe link wears there is all sorts of noise in the rear end even before you can detect the wear by movement of the wheel.


That's true, but in the scheme of things practically a non-starter because the 16 other rubber suspension bushings are doing this as well. To eliminate it you would have to go the Jimlab bushing route but I wouldn't do that to a car that sees much street duty.

Above you say there is no load in the stock toe links. If there is no load in them why are the tires deflecting? It can't go both ways here.

Rubber in the suspension is used to isolate road and tire noise as well as vibration from the chassis and therefore the occupants. Replacing rubber with solid materials will of course be better for wheel control, but compared to stock the NVH will be much higher. Anyone who has ever driven a truly prepared solid bushed racecar can tell you that you wouldn't want to drive it on the street to the grocery store very often.

DamonB

With stock suspension bushings I notice no increase in harshness at all when using solid toe links. Aftermarket toe links wear very quickly compared to the stockers and so some of us are running dust covers to try and prolong their life. I notice no handling advantages with aftermarket toe links compared to stock.

The pros and cons as I see it are that the stockers last a long time and are quiet. Once it's time to replace them the stock bushings cost more than just buying a set of aftermarket toe links. Aftermarket toe links are cheaper to replace but wear out in roughly a third of the time it takes a stocker to. You pick your evil and live with it.

I have since gone full circle and am putting stock toe links back on my car. Even with the dust boots on a high quality aftermarket rod end I don't feel they will stay wear and noise free as long as a stock toe link will on a car that sees as much mileage as mine.

Chronos

Great info, however I'm positive that someone mentioned something about a huge change in highway driving after replacing some suspension component...allthough I can't remember if it was trailing arm, bushing, toe-link or what.

In regards to the toe-links wearing out very fast I assume you're referring to the M2 units? If that's the case then perhaps it might be a good idea to install them just for racing and when you're done put the stock units back on, that way you get all the performance you need at the time you need it and don't have to pay for replacement units. The only question is how hard is it and how long does it take to switch them???

Howard Coleman

iTrader: (6)

thanks for the constructive follow-on comments. i would like to make a few points:
1. the rear of the rx7 is essentially a double A-arm suspension with a half-shaft (drive shaft) and a toelink. the toelink is rubber bushed at both ends (really). with miniscule exception it is the toe link that controls steer. any deflection in the lower or upper bushings is almost meaningless if the toe link doesn't deflect... which the stock ones do.. the fact that there are other rubber bushings in the rear is not a controlling issue based on their location and function, it is the toe link that points the wheel.
2. in a steady state, either at rest or driving in a straight line it is the lower control arm bushings and the top of the shock that carries the cornerweight. (the upper control arm carries no vertical load.) these are the bushings that if you change their durometer you will realize a dramatic change in ride quality. i specifically stated, the toe link only transmits force in a corner or under braking or acceleration and it is at a major angle and is diluted. while replacing the lower longitudinal link (which is part of the lower A-arm) has a major effect on ride quality (it supports vehicle weight) the toe link does not. which is not to say the links don't do any work.... they do, under braking and acceleration. that's why they wear out. but they are very important as they are key when you drag launch (think 60 ft times) or come ripping into a corner and get on the brakes.

i know it is really important to have your wheels pointed in the right direction and rubber bushed toe links have no place on a sportscar...

that having been said i am not in favor of replacing any other (except swaybar) bushings on the car as i think they exact too high a price in ride comfort. as to whether you can feel solid toelinks ... i sure can and i am smiling.
howard coleman

cover8

I have the complete Jimlab bushings, K2RD toe links, coilovers, widefoot mounts (awesome btw!), suspensions tech urethane bushings, gab front strut, JICs, and 18" volk GTCs on p7000s.

Little bit more road noise, if roads are wavy, you cannot speak without your voice wavering, handling is superb...difficult to break the rear end loose. But the ride is not teeth chattering by any means. My coilovers are on 8clicks in the front and 4 clicks in the back.

But damn is my rear suspension noisy, are my toe links worn out already? I have not replaced the pillowballs on the rear. the front is very quiet.

Howard Coleman

iTrader: (6)

hey cover8,
looks like a nice suspension package... i am zeroing in on your upper shock mounts as to the noise... do you have the stock upper rubber mount w the 3 studs or the non oem pillowball. chances are it is the non oem pillowball if that is on the car. i have logged lots of miles on jimlabs complete bushing set and i do appreciate how it sharpens the car. i prefer the oem bushings as the solid bushings can be a little much around town. i run the rs*r coilovers w stock upper bushings. i also have the widefoot swaybar mount. i run 25 inch rideheight at the wheelwells, about 30 psi front and 28 rear cold. 18X8.5 front and 18x10 rear w toyos. shock full soft rear and 8 clicks upfront. BTW, i have a shock dyno and an electronic spring checker. one item most should consider is a laser toe gauge.deadly accurate and fast for $300. as to noise..... is it continuous or like a hammer-strike? Jim's bushings wear if not lubed and they may be your problem. properly rubber shielded rod-ends should last as long as your car if good quality rodends. you can buy just the rubber shields and install them on your non-shielded rodends. 'don't know where you get them maybe QA1 in Minn.
howard coleman

DamonB

I disagree. The rubber bushings in all the suspension arms also deflect. Even if the toe link is solid and cannot move, the rest of the suspension is still deflecting and therefore changing the orientation of the hub carrier in relation to the toe link. The wheel will still deflect.

I agree with that only when the car is in a smooth, steady state. Any cornering, braking or acceleration will cause deflection throughout the other bushings (mainly the large upper and lower a-arm bushings at the chassis) and change the tires' attitude to the road. The large a-arm bushings at the chassis will in effect let the suspension arms try to pry themselves from the car under braking. This deflection effects both front and rear wheel steering, with the front absorbing the most. This is the reason the lower front a-arms are so massive, they have to feed the braking loads into the chassis.


You mean the sprung weight of the car? If so that's true at the front but the rear suspension attaches the shock/spring to the upper control arm.


I feel that is true as well. That is the reason I notice no performance difference between the two types of toe links. In the scheme of things compared to the rest of the suspension their deflection hardly contributes IMO.

My findings as demonstrated by the aftermarket links are that they wear due to contamination and not the load. The links wear because even when they are not under any stress the up and down movement of the suspension still force them to move and so wear the joint. With an aftermarket toe link the ball is effectively clamped solidly to the car. The eye rotates around the ball every time the car hits a bump and so wears down, even though the car is not being run hard.

Yeah, my front sway bar mounts and bushings are completely solid and I have never, ever sensed any harshness or noise due to them.

Have you ever been on brand new stock toe links? Any bushing that is worn is of course inferior. In my car I can tell no difference between stockers and aftermarket. If the rest of my suspension had solid joints in them perhaps I could but it would be very slight.

DamonB

If you have never replaced the pillowballs they are a very likely culprit. As for your aftermarket toe links I have found they always get noisy before you can detect any issues at the wheel.

pomanferrari

iTrader: (1)

Howard, can you explain the above statements a little more? You like the JimLab bushing but prefer to run OEM bushing (you mean shock tower bushing or the control arms bushings?)?

Howard Coleman

iTrader: (6)

pomanferrari,
re jimlab bushings:
they are well engineered but still create the same old problems that accompany bushings of that nature. the stainless steel inner bushing wears on the carefully and tightly clearanced nylon (or whatever it is) and eventually you get slop and noise. the fix is to drill your suspension assemblies for zerk fittings and grease them.. i just can't bring myself to drilling my control arms and the grease runs out etc. they do work well and i wouldn't have a problem running them. the ideal setup IMO is higher durometer (stiffer) rubber bushing which i think is available somewhere. if i was on a budget i would just buy the lower control arm bushings and the solid toe links.
howard coleman

jimlab

You're probably referring to Ken Francis' write up of his trip home from KDR and how unstable his car felt until Steve Kan took a look at it recently and found that only some of the bushings had been installed, and one of the bolts was missing from the differntial mounts, not to mention that the car had never been aligned after the suspension work.

I've driven three cars with full sets of my bushings and they all felt 100% stable and I noticed no major increase in noise. I've got a friend who is pretty picky about his car and he's running just my differential bushings, the most likely to cause gear noise to enter the cabin, more than likely, and he has no complaints whatsoever.

Ehughes

Which of the bushings/links is most likely to cause the "knocking" noise most of us get? Let me add that I get a ton of "rear steer" with accel/decel. I am guessing the toe links.

Howard Coleman

iTrader: (6)

rear steer on accel/decel & knocking noise is normally the front bushing on the rear longitudinal link. have someone drive yr car in a parking lot and hit the brakes from 5 mph and accelerate. you will see the wheel move forwards and backwards. replace w solid bushing is a win win. much additional rear stability w no ride penalty.

howard coleman