Leaf Spring Bushings... To Poly or not to Poly?

All,

I am now at the stage where I have removed my worn, degraded and extremely rusted rear leaf spring bushings, they had.. I think, a steel casing, then rubber (long gone) and a centre steel bolt sleeve casing..

Leafs are 2" wide.. I am unsure as the only thing left after pressing the rotted tube out was the steel casing rusted to the spring, and dried rubber, no other sleeves left. When heated to remove, burnt rubber was smelled... Out now and spring eyelet cleaned out...

I have been searching forums to see if I should replace them with similar steel or use the new polyurethane type that plugs in on each side... The steel casing one I have to press in...

any my thoughts as to the pros n cons of each?

Use the stock rubber ones. You may need a press to install them. Urethane are more for racing. They are hard, do not absorb shocks and vibration, and tend to squeak.

If the polyurethane bushings come in two halves, then you can do similar with normal rubber bushings from another application. That's how the shackle bushings are on my '77 Camaro . . . two halves with no center bushing sleeve. So, there might be more possibilities than you might suspect. In any event, I'd stay with rubber bushings of whatever type you might choose. Better impact harshness absorption, for example.

I know the polyurethane suspension bushings have become quite popular, especially where improved handling dynamics might be involved, but for a lower-speed vehicle that might never squeal the tires in a corner, I don't feel the alleged benefits of the polyurethane bushings (for your application) would be something I'd do OR consider. Even on a more modern vehicle, they are known to squeak (unless they might have the embedded moly particles, or come with grease zerts), from what my front end alignment associate advised "back when".

ONE thing to remember regarding spring/suspension rubber bushings . . . install them with "locating torque" where they pivot, then "full torque" when the vehicle is ON THE GROUND at normal ride height. Otherwise, if you fully tighten things down with the suspension items fully-extended, it'll stress the bushings too much when the vehicle is lowered to normal ride height. The center metal sleeve might minimize that need, but the edges of the rubber bushings are still contacting "something" that would cause the mentioned stresses.

If you want to use polyurethane in the rear suspension, the "isolators" between the leaf spring and their clamps to the axle would be one. Generally, there are places in the suspension system where you need the factory-engineered isolation, but other places where you might get away with something more solid. Taking away isolation in particular locations means any stresses will be transferred to places in the chassis/body that were not designed to handle such stresses.

To me, in a vintage vehicle where driving enjoyment is important, keeping the factory-designed rubber isolation in the suspension system CAN be important. Even if some different configurations might be needed, the key thing is that it's "rubber" than something more solid.

Just some thoughts,

NTX5467

My 1930 Dodge DC was one of the first vehicles to use those spring shackle bushes with rubber sleeved between steel tubes.

They work by having the centre tube gripped strongly in the chassis mounting and not able to rotate. The outer tube is a friction fit in the spring eye and rotates with the spring eye. The rotation is taken up in the rubber sleeve between the two steel sleeves. If the mounting bolt is worn, the inner tube has been rotating.

As NTX5467 says, assemble and put on the ground, then apply full torque to the centre bolt. This results in the centre tube being the normal position for clamping. There may be "shakeproof" washers or another system on the ends of the inner tube to ensure the grip between it and the chassis.

DO NOT use urethane. They rely on "crush" longitudinally to expand them sideways to grip whatever they are in. There is no way to get any crush on these bushes. they will just slog out the spring eyes and wear the bolts away and rattle after some wear has occurred. And the vehicle will hop around on the road, just as it is now with no rubber left in the bushes.

Mine has two sizes of bush. I managed to get some of the larger from the manufacturer Mackay Silentruba in Australia (I bought their entire stock). Otherwise, I would have had to have some made. The smaller bushes I made out of Daihatsu light truck bushes. I had to turn a few thou' off the outside sleeve and shorten them for a perfect fit.

I removed and installed mine with a long bolt and nut (lubricate the thread!), a bunch of big, thick washers, pieces of pipe as long as the springs are wide just slightly smaller in OD than the bush. A fine thread makes it easier than a coarse thread on your long bolt. Don't rely on the jack alone if you are working under the car.

I'll post this and look up their catalogue. Is it for a 1937 Pontiac Silverstreak?

Mackay Silentruba list a bush S26 (manuf. part No. 3690790) for rear spring front for all 1931-38 models of Pontiac.

I wrote to Mackay and they sent me the original dimensions of my bushes. You can probably get yours by measuring what you have, but may try the same thing. The note may have S26 on it as well....

S26 are 1-21/32 OD, 0.5 in bolt hole, 2" o/s sleeve length, 2-13/32 inside sleeve length.

Thanks,

I found the OEM,s along with some alternative MOOG parts etc... Pep Boys has them for 6-10$ where as here in Canada, 38$ each...

http://www.pepboys.com/search/?term=leaf+spring&omniEvars=leaf+spring&omniEvent=event1

http://www.pepboys.com/product/details/991652/01036

http://www.pepboys.com/product/details/1056462/01036

I didn't see the sizes on those bushes?

Mackay Silentruba list a bush S26 (manuf. part No. 3690790) for rear spring front for all 1931-38 models of Pontiac.

I wrote to Mackay and they sent me the original dimensions of my bushes. You can probably get yours by measuring what you have, but may try the same thing. The note may have S26 on it as well....

S26 are 1-21/32 OD, 0.5 in bolt hole, 2" o/s sleeve length, 2-13/32 inside sleeve length.

Thanks, Ill research your information.... appreciate all the feedback everyone!!