Brake Reaction Rod Help

[CTX-SLPR]

Howdy,



So the front suspension of my '64 Riviera uses a single lower control arm and a brake reaction rod. Since the front of this rod is anchored in a big rubber bushing that the modern replacements doesn't seem to holdup and the rubber is squishy, I'm thinking of replacing it with a spherical bearing. This is not without precedent, reading up on Trans-Am mustangs mention uni-ball conversions on their similar rods but this car is 4000lbs dry so the weight is higher. I'm leery of using a heim because it would move the pivot point rearwards and outwards. The rod is somewhere between 3/4 and 1in diameter and I would bolt it through the bearing.

Two questions:
1. Is moving the pivot point a worry? I'd have to measure the angle to know how much out of plane it would be from the control arm pivot. Seems to me it would cause negative caster gain which I doubt is a good thing.
2. How much load goes on that joint since spherical bearings are only 20% of radial strength in axial. Likewise for compression vs. tension since most of the shepherical bearing holders use snap rings on one side. Was thinking radial load >10x the vehicle weight would be sufficient.

Thanks,

[CTX-SLPR]

So I was doing some research and thinking on axial loading on spherical bearings and ball joints and noticed some stuff. First off, camber plates usually have spherical bearings loaded axially. Secondly, I can't come up with a reason the front bearing would ever be loaded in direction other than in tension other than the wheel getting hit from behind.

As such digging through the FK bearing catalog I found a set that would fit right over the top of the existing reaction rod threads, an AIN-8 1/2in bore bearing. I'm extrapolating a bit on the ~5600lb axial rating based on other ones with listed ratings. The reason I'm not looking for an oversized bearing with spacers/reducers is the hole in the frame is only so big and I'd prefer not to oversize it. I think I would probably get a custom holder machined up with a ridge that fit into the existing hole and threads on the otherside to retain it in the frame.


Stock Brake Reaction Rod

[TheJDMan]

You're using rubber bushings, have you tried Polyurethane bushings? I think a rod end is going to transmit a lot of road noise and vibration to the frame but I also think it will maintain the lower control arm position much more rigid which may or may not be a problem. Does Hotchkis sell a suspension kit for this car? If so that might be worth looking into.

[andrewb70]

ridetech has a specially designed bearing that they use in their Mustang kits. Have a look at their website, or give them a call. They may have something for you.

Andrew

[CTX-SLPR]

You're using rubber bushings, have you tried Polyurethane bushings? I think a rod end is going to transmit a lot of road noise and vibration to the frame but I also think it will maintain the lower control arm position much more rigid which may or may not be a problem. Does Hotchkis sell a suspension kit for this car? If so that might be worth looking into.

Poly's have a tendancy to snap the rod (both on the GM's and the Mustangs) because the rubber bushing is supposed to act like a spherical bearing, all of the motion is "bending" the bush, not rotational.

ridetech has a specially designed bearing that they use in their Mustang kits. Have a look at their website, or give them a call. They may have something for you.

Andrew

I've seen stuff for the 66-70 Chevy stuff but it was basically an adapter that bolted to the frame mount that picked up a radially loaded rod end ~2in back from the original pivot point along the axis of the rod. I think I've found what you are talking about:

http://www.ridetech.com/store/1967-1...arm-lower.html

Also shows up in the 65-70 Chevy Fullsized:
http://www.ridetech.com/store/1965-1...wer-front.html

Thanks for the info, now to convince them to let me have a pair to used with the stock rods or to make bolt on rods...

[CTX-SLPR]

Closing the loop somewhat on this. They won't sell the cool spherical bearings by themselves. I've not asked about their suppliers but asking a ridetech guy directly resulted in the following:

Unfortunately they will not let me separate them from the arms. Everything is made up as a kit. If I separate it then I will only have a partial kit. Sorry I couldn't help

[TheJDMan]

Might be worth contacting Bret directly about this. He is the owner of ridetech.

[CTX-SLPR]

I asked about who they get them from and got:

There isnt a supplier as we manufacture the parts and pieces of the pivot end. I wish that I had more to help you with on that.

I guess I'll just wait if Brett sees this. Today I'll ask the engineers at work about the load capacity of a spherical bearing in the axial direction.

[pitts64]

El Polocko on HAMB knows a lot about modifying these cars....

[alocker]

Global west sells the rods with bearings for the 65-70 platform that may work for your application.

[CTX-SLPR]

Global west sells the rods with bearings for the 65-70 platform that may work for your application.

The thing I don't like about the Global West approach with heims is that it pulls the axis of rotation off of the centerline of the bushing.

[krom]

If you are gong to use a spherical bearing, and are worried about the axial load/pull-out, you should add some safety washers:



they will keep the rod from coming out and loosing control, if the bearing where to fail.

[MrQuick]

Long before stuff was available we use to use screw in balljoints. The threads were 1/2" x 20 threads. So you can run a 1/2" thread coupler or tube adapter into a 5/8" tube and run a heim plate on the lower control arm. I can't remember the part number of the ball joint but it was threaded halfway down the shaft. (2")

Weld this sleeve into the frame section were the factory bushing sat. http://pitstopusa.com/i-19425222-how...-screw-in.html

[CTX-SLPR]

Long before stuff was available we use to use screw in balljoints. The threads were 1/2" x 20 threads. So you can run a 1/2" thread coupler or tube adapter into a 5/8" tube and run a heim plate on the lower control arm. I can't remember the part number of the ball joint but it was threaded halfway down the shaft. (2")

Weld this sleeve into the frame section were the factory bushing sat. http://pitstopusa.com/i-19425222-how...-screw-in.html

How well did that hold up? I've long thought about that and even asked Pro Forged about doing it and they wouldn't even give me the engineering specs to consider out of liability concerns. A ball joint is more likely to be able to fit the existing frame bracket and it certainly makes clearance easier in that area without a 9/16in threaded end sticking out in the same basic space that my intercooler tubing and lower radiator hose run. Thanks for the real world validation of that idea. I'm guessing running a top tier Howe joint is the best idea.

On my other line of though of using spherical bearings New Hampshire Ball Bearing is one of the few places I've seen listing axial loading limits on their spherical bearings. My math model for sizing these things is each bearing can take 1.5G of deceleration with the 4200lb car on the listed limit strength (which gives me a factor of 2 safety since limit load will deform the race). That's an axial limit strength of ~6300lbs. The 0.625in bore Beryllium-Copper units have the highest axial load rating I've seen for a direct application though they are metal on metal. I'd have to step up to a 0.75in bore unit for the sealed units to get the factor though it's close at 6130lbs for the 0.625in unit.

[CTX-SLPR]

If you are gong to use a spherical bearing, and are worried about the axial load/pull-out, you should add some safety washers:



they will keep the rod from coming out and loosing control, if the bearing where to fail.

Didn't even notice this till now. Thanks, I will absolutely be using something like that to keep the rod from pulling through in ultimate failure (thinking mainly accident type scenarios).

[CTX-SLPR]

Long before stuff was available we use to use screw in balljoints. The threads were 1/2" x 20 threads. So you can run a 1/2" thread coupler or tube adapter into a 5/8" tube and run a heim plate on the lower control arm. I can't remember the part number of the ball joint but it was threaded halfway down the shaft. (2")

Weld this sleeve into the frame section were the factory bushing sat. http://pitstopusa.com/i-19425222-how...-screw-in.html

How well did the ball joints hold up in this application? I'm guessing that they'll work OK since in stock application they are taking the weight of the car trying to pull them apart on the lower arms.

[bret]

Closing the loop somewhat on this. They won't sell the cool spherical bearings by themselves. I've not asked about their suppliers but asking a ridetech guy directly resulted in the following:

ill sell you whatever components you need. Email me directly. [email protected].

[bret]

Who is giving you this information from our shop?

[CTX-SLPR]

Brett,

I sent you an email.

Thanks for noticing my thread.