Roller spring perches...

basically it lets the front end react to bumps etc in the road without binding. since the bushings in the perches are vulcanized to the shaft it binds horribly.

what tommy said. stock rubber bushings bind badly, partly because the factory designed them that way. even poly bushings bind somewhat. roller bearings allow for virtually free movement through out the suspension travel.

If your car has "bump steer" meaning it hits a bump and turns on it's own accord, your car may or may not have "bump steer" which is a change in toe in setting as the car rises or shrinks through wheel travel.

If you car darts on bumpy surfaces your car likely doesn't have enough caster.

The binding of the perch does not directly bind the suspension. The binding of the suspension is caused by the huge side loads transfered to the shock and causing the shock to bind. Many stock suspensions use coil springs that sit directly on the lower control arm. There is no perch to keep the lower and upper ends of the springs parallel and causes only a slight spring rate change but no bind.

bumpsteer is where the suspension geometry and the steering geometry is off a bit, and the lower control arm and the tie rod link move in different arcs. even with the stock suspension, bumpsteer isnt really a problem until you get to the last half of suspension travel. you need to change the angle at which the tie rod link sit compared to the lower control arm. there are bumpsteer correction kits on the market for the mustang. that said however, i wouldnt worry about bumpsteer unless and until you go racing with the car, unless the bumpsteer is severe, and then you have a serious problem.

rbohm said:

i wouldnt worry about bumpsteer unless and until you go racing with the car, unless the bumpsteer is severe, and then you have a serious problem.

Click to expand...

Believe it or not it is usually not that much of a problem at the track as the surface is usually fairly smooth without bumps (unless you visit Sebring). In addition when the early model is set up "loose" (rear wants to come around) you tend to do a lot of steering with the rear of the car.

Street driving is somewhat different and the bumpsteer comes into play.

HistoricMustang
www.historicmustang.com

65fastbackresto,

It sounds like you may have a couple of things going on.

First the roller spring perches are a great upgrade, but I don't think they are going to solve your problem.

If your strut rod bushings are cracked, I would replace them or better yet upgrade to one of the adjustable strut rods (Street or Track, Global West, TCP). The strut rods may be contributing to your problem, but I would expect strut rod issues to show up more under braking and turning, not tracking straight down the highway.

My guess is your alignment shop looked up the original alignment specifications. The stock alignment specifications were good for the bias ply tires of the day. Today’s new radial tires will accentuate the poor manners of the stock suspension's geometry.

The original stock alignment setting for '64 - '66 Mustangs are:
Caster: -0.5*
Camber: -0.5*
Toe-In: 9/32"

The Performance alignment settings are:
Caster: +1.5° to +2.5°
Camber: 0 to -.5°
Toe: 1/8"

The biggest difference being in the Caster setting. A positive Caster setting will help the car to track straighter and return to center more quickly after a corner. The easiest way to describe it would be to think of a bicycle and angle of the front wheel fork. If the fork that connects the handle bars to the front wheel were to be straight up and down (0 degrees Caster) you would constantly need to steer to keep the bike going in a straight line. Now if the front fork were installed at an angle (think chopper - Positive Caster), you could take your hands off of the handle bars and the bike would continue to track in a straight line.

So even if you have not done the "Shelby drop" modification, you will still benefit from an increase in Positive Caster in a street driven car. I would suggest at least 2 full degrees positive caster.

The other possible issue could be a bumpsteer issue, but this does not generally show up unless the front suspension is lowered and low profile tires are used. What are your front end components and tire sizes?

Post a little more information and I'm sure we can point you in the right direction.

Tim

The roller spring perch improves handling by allowing the base of the spring to remain level compared to the top of the spring throughout the articulation of the suspension. The stock perch is too stiff and so when you go over a bump, it essentially stays in the same orientation regardless of the angle of the upper arm. This means that the outside of the spring becomes much shorter than the inside when the upper arm moves up and down. This leads to variable spring rate (and not in a good, predictable way). The spring wants to become "c" or backwards "c"-shaped and causes the shock to bind (shocks work best up and down, without any sideways force on them), wearing it out prematurely, too.

When I changed out my old perches to roller perches, my old perches remained at an angle. I could only rotate them in a vise with considerable force. The suspension reaction is much better now, and the car handles much better than with the old perches.

As far as bump steer (which is caused by the lower control arm and the tie rod moving in different arcs, which pulls the toe in or out as the suspension moves up or down), the roller perches won't help any as you would still have the two arcs. You can get a bump steer kit from Pro-motorsports or Baer which will help, but you really need to measure the bump steer (or have a suspension shop do so) before throwing money at the problem. You may have other issues (like the strut rod bushings mentioned already) or other binding going on. All vintage Mustangs have some bump steer with the stock suspension, although the kits can minimize it some. Really stiff springs (like HistoricMustang uses) prevent the suspension from moving much and thus minimize bump steer. Like he says, this is fine on a smooth track but may not be so enjoyable on a rougher street environment.

Any time you take a compontent with a bushing that can bind in suspension travel and change it to a roller component, you free up that part to react in a more predictable, smooth way. You may find that you need a higher spring rate, though, as all the binding sites were helping to slow movement down! Opentracker stuff is excellent and he's a great guy/company to deal with, too! Ask him questions and he'll suggest the right things to you, even if it means you won't spend as much money with him.

Daniel

I do know my strut rod end rubber bushings look cracked, could that contribute to the problem?[/QUOTE]



This is where I'd start first. I tried to track down my "Bumpsteer" problems for over a year. When I hit an imperferction in the road the car would dart unpredictably. Following "trucker tracks" on the highway made me hold the steering wheel tighter than riding a roller coaster.

The tell tale sign for me was that my car would steer back and forth as I applied the gas or hit the brakes.

If those bushings are bad it causes the susp to move back and forth essentialy turning the tires for you.

If you can see cracks in them you need to change them anyways. Besides it's a cheap fix.

65fastbackresto,

You can't go wrong ordering parts from OpenTracker. John is very well respect in the Mustang community and I have never heard anything negative about him or his parts. I run some of his parts, also, including the roller spring perches.

Also, 2bav8 is very knowledgeable on performance suspension setups.

If you've got the money to swap out the entire front end at once, then go for it. Otherwise, I would start with new adjustable strut rods and the alignment suggested above. My guess is your shop used the original alignment settings, which will make your car wonder at high way speeds. Especially with your tires.

Tim

65fastbackresto,

Looks like you have received a lot of good info. Here's a site that tells you how to make your own roller spring perches as well as other cool stuff. It's a little challenging but rewarding as well. He also sells completed perches.

http://home.bresnan.net/~dazed/DazeCars

gtmegrad

65fastbackresto said:

I know they somehow pivot or something, but exactly how do they help the handling of the car?

I have a fair amount of bumpsteer, I have to work the wheel a little driving down the road, I had it aligned, you would think they would have said something if something was wrong with the front end.

I do know my strut rod end rubber bushings look cracked, could that contribute to the problem?

Click to expand...

Take a look at my Mustang handling page:

http://home.bresnan.net/~dazed/bump

this will make understanding "bump steer" a lot easier, and weither or not you actuly have bump steer issues it has good solid info on improving the handling of your car.

daze i actually took my own advice and ordered a kit from you hahaha.

Tom