Needle bearings for front suspension

[Walt Fricke]

I replaced urethane aftermarket bearings for my 2.7 1977 front lower control arms 20 or so years ago with needle bearings from Shine Racing (which specialized in VW and 914 stuff). They worked great (car was dual purpose track/street at the time, now track only). I am concerned that one or more of these has failed (Shine said they ought to be inspected and greased periodically, which I didn't do), and may be the cause of strange track tire wear. Shine appears no longer to be in business, or at least is not a supplier of these.

They consisted of a radial Torrington needle thrust bearing, and some kind of caged axial bearing. I can't recall if inner, outer, or both sleeves were needed. Does anyone have dimensions (even better, part numbers from some bearing manufacturer) so I could purchase replacements?

If one or more are broken, I suppose I can measure myself, but before the car goes to a shop to figure out the front end issue I'd like to have replacements on hand. The shop isn't going to want the car taking up space while waiting if that can be avoided.

Walt

[Bend911]

This is all I see in the parts manual. I also checked Pelican and the only option I see is purchasing the control arm with the bushings as a single unit. I'm sure someone has a part number for bearings/bushings.

For what it's worth I'm upgrading my complete suspension ('75 911S) with Elephant Racing and they sell the parts individually.

[HarryD]

Hi Walt. If it was me, I would be talking with Jeff at Rothsport about your issue and his suggestions on how to proceed.

[TimT]

I have a set, new, never installed.


Ill try and find a pic

[Walt Fricke]

Thanks, Tim
These are not stock Porsche parts. They are aftermarket adaptations.
Back in the day guys ran Delrin bushings in place of the stock rubber stuff. Then Urethane. Then along came poly/bronze. But needle bearings have the least friction of any.

[TimT]

I should have been clearer. I have a set (of needle bearings) that have never been installed..

[Quicksilver]

The problem with roller bearings is they aren't a good choice for a small repeating range of motion. Working a roller back and forth over a small range is counter to the intended design purpose of a roller bearing. They are intended to roll continuously so the roller's face will randomly interface with the races. Repeating the points of contact between the rollers and race will massively increase the rate of wear.
The needle bearings used on the G50 release fork suffers from the same design error. The preferred solution is the same: Bushings.

[Jeff Higgins]

I hate to say it Walt, but if it were me, I would be looking at some other form of bushing or bearing as a replacement. As long as you are in there and spending some money anyway, this might be a good time to switch to something more suitable.

This is a misapplication of needle bearings if I ever did see one. Needle bearings can work well in applications wherein a shaft is spinning inside of them, and the needles can spin (about their own individual axis) as well. That way a different side of the needle gets loaded as the shaft spins. Even better is where the needles are free to rotate about the axis of the shaft as well, so no one group of needles stays on the loaded side of the shaft.

These are commonly used on spinning shafts, wherein one end is supported by a solid bearing and one end by a needle bearing. The needle bearing provides for some degree of "self centering", so the two bearings don't have to be as precisely coaxial as they would if both were plain. They also "splash lubricate" rather well, eliminating the need to provide the pressurized lubrication required of plain bearings.

In an application such as a pivoting suspension arm, the same poor needles are stuck doing all of the work all of the time. They don't revolve on their own axis, "spreading the load" around their own circumferance, nor do they rotate about the axis of the shaft "sharing the load" with the other needles. I wouldn't be surprised if, when you take them apart, you find the upper needles with significantly more wear than the lower needles.

I'm sure these worked great for awhile, providing a good, solid, slop free fit. This is really not what needle bearings are meant for, however. Might be a good opportunity to update.

[Locker537]

Elephant also sells spherical bushings. As does Rebel Racing.

[Walt Fricke]

The same argument has been used against needle bearing rocker shafts on engines. I think some high end builds (not our 911s) use needles there? But maybe dragsters, where you get a near rebuild between passes?

Next week maybe I'll see how they look. When I had the struts off two years ago, both A arms moved frictionlessly up and down as before.

My highly modified originally 1968 track car has been modified to use spherical bearings for the A arms (banana, too). Those are great.

[Dpmulvan]

Originally Posted by Walt Fricke

The same argument has been used against needle bearing rocker shafts on engines. I think some high end builds (not our 911s) use needles there? But maybe dragsters, where you get a near rebuild between passes?

Next week maybe I'll see how they look. When I had the struts off two years ago, both A arms moved frictionlessly up and down as before.

My highly modified originally 1968 track car has been modified to use spherical bearings for the A arms (banana, too). Those are great.

Dragsters use bushings here’s a set of jesels used in nitro et.

[Walt Fricke]

Thanks, Locker.
It had been a couple of years since I looked at Elephant's catalog. His inventiveness never sleeps, does it. These spherical bearings look very good.

[Jeff Higgins]

I remember a number of motorcycles in the '70's that had needle bearings on the rocker shaft pivots. BMW airheads, Harleys, and probably others. While spending (wasting?) too much of my formative years hanging out in shops that worked on these kinds of things, a mechanic gave me a set of "super trick" rocker arms for my Sportster. These dispensed with the needle bearings, replacing them with bushings. That was the "trick". Many, many years later I had a set of heads built up by Dan Baisely in Portland, a legend in Harley performance circles. His homemade trick roller tipped rockers are bushed as well.

I do remember a few of the high performance rocker arms for American V-8's being sold with needle bearings in the '70's. They were pretty quickly abandoned, though. The extremely high spring rates required in their valve springs, so as to close their big heavy valves at high rpm's wreaked havoc on the needles. They soon went back to plain bushings.

I'll be interested to see how they look when you take it apart. Just a thought - I bet you could simply rotate them 180 degrees and get another 20 years out of them.

[Walt Fricke]

We'll see.

One thing I hadn't paid a lot of attention to was axial alignment. Elephant's poly-bronzes have the fairly thin poly layer in part to allow some self-alignment, as I recall the pitch. I've got them in my rear suspension - needles weren't available for that from Shine by the time the poly-bronze showed up. Needles aren't going to do any of this aligning, though they clearly worked for quite a while in their application (track only eventually), and longer than the urethane bushings which distorted enough to allow thick torsion bars to rub on the housing some.

[Locker537]

Originally Posted by Walt Fricke

Thanks, Locker.
It had been a couple of years since I looked at Elephant's catalog. His inventiveness never sleeps, does it. These spherical bearings look very good.

I installed them on my track car last season. The install was straightforward. The arms rotate freely. No more squeaky bushings and no more rubbing torsion bars.

The one detail that I did not see mentioned anywhere is to ensure you push the control arm towards the rear the car to ensure the bushings are fully seated. It's a little tricky. I noticed some fore/aft play before I did this.

I probably need to snug up the passenger side as it makes a little clunk over some slow speed bumps.

[Flieger]

Main thing is that rolling contact bearings have high contact stresses so for high loads (especially impact loading) they end up being bigger and heavier than a bushing. However, if they are operated within their design parameters they do have the minimum friction like you said. The problem with bushings is they develop slop over time, and they have more friction. Mountain bikes use relatively small full-complement ball bearings (higher load capacity but a bit more friction for a given size) and they work pretty well. Mostly it's the elements that wear them out. For the lightly-loaded front of a 911 I could see a similar solution working, and it sounds like the needles have held up pretty well over the years.

That said, I agree that going with a bushing is probably the way to go.

What I am more interested in is if someone has made any rolling contact bearings for the 911 strut (more complicated since it both plunges and rotates), since the bending stress in the strut is one of the main drawbacks compared to a dual A-arm.

[Locker537]

Originally Posted by Flieger

Main thing is that rolling contact bearings have high contact stresses so for high loads (especially impact loading) they end up being bigger and heavier than a bushing. However, if they are operated within their design parameters they do have the minimum friction like you said. The problem with bushings is they develop slop over time, and they have more friction. Mountain bikes use relatively small full-complement ball bearings (higher load capacity but a bit more friction for a given size) and they work pretty well. Mostly it's the elements that wear them out. For the lightly-loaded front of a 911 I could see a similar solution working, and it sounds like the needles have held up pretty well over the years.

That said, I agree that going with a bushing is probably the way to go.

What I am more interested in is if someone has made any rolling contact bearings for the 911 strut (more complicated since it both plunges and rotates), since the bending stress in the strut is one of the main drawbacks compared to a dual A-arm.

I think the challenge with using a conventional ball bearing in this application would be alignment. The spherical bushing alleviates this.

[Flieger]

Originally Posted by Locker537

I think the challenge with using a conventional ball bearing in this application would be alignment. The spherical bushing alleviates this.

Yes in theory, however I have plain bearings (Rebel Racing) on my car which don't allow any misalignment in theory but they work. You use spherical washers under the housings so they can align to each other.

The mountainbike bearings I'm talking about are double row so in theory they shouldn't allow any misalignment but they are angular contact bearings arranged in such a way that they have a small amount of angular play which helps them work better in real life. I found that out the hard way trying to use one bearing to save weight in an application then finding that it had way too much play.

So, I don't think the rolling contact bearings in this application would be any different than the normal Rebel Racing ones.

[Locker537]

Originally Posted by Flieger

Yes in theory, however I have plain bearings (Rebel Racing) on my car which don't allow any misalignment in theory but they work. You use spherical washers under the housings so they can align to each other.

The mountainbike bearings I'm talking about are double row so in theory they shouldn't allow any misalignment but they are angular contact bearings arranged in such a way that they have a small amount of angular play which helps them work better in real life. I found that out the hard way trying to use one bearing to save weight in an application then finding that it had way too much play.

So, I don't think the rolling contact bearings in this application would be any different than the normal Rebel Racing ones.

Ah, yes, I forgot about those spherical washers that can be used to help with alignment.

[Walt Fricke]

Spherical washers = one concave, one convex, like Porsche used on the 917s, or maybe the 935s, for the case through bolts?

The front housings?