Rod End wear/replacement

[Rick Kirchner]

I was wondering what others have found with regards to the best rod ends to use in highly stressed applications.

In my 94 Van Diemen, I've found that the pushrod joints wear fastest, and for some reason, the ones at the top quicker than the bottom. The next highest stressed seem to be the rear leg of the lower front A-arm, and the front leg of the lower rear A-arm, and the big joint on the outboard end of the front upper a-arms.

In the past, I've used the Aurora XAMT series, but I'm beginning to question the logic of that choice. I'm only getting about 12 weekends out of them and the tracks are pretty smooth out here.

it seems to me that the teflon liner, being the softest part of the assembly, would wear quickest under constant pressure, since teflon cold flows and the pushrods in particular have 100-200 pounds of force on each joint just sitting still. Wouldn't a metal-on metal joint be better in this application?

I've been considering using NHB or Heim joints in highly stressed locations, but at nearly 3x the cost of the Auroras, if I don't get at least twice the life it's a bad investment - even taking into account the hassle factor of taking stuff apart and then having to re-jig the car.

Has anybody found a long-life solution? I've noticed FK and QA-1 are offering Teflon/kevlar liners. Anyone have any comparative data or experience? The stock Rose joints, while ugly, seem to hold up pretty good, but none of our usual suppliers carry them, other than Primus. Given the same materials used by each manufacturer, the loads they can handle should be about the same, but this is a wear issue, a bit harder to quantify.

[Steve Demeter]

Rick,
The metal to metal joints inherently have some play in them that the teflon ones do not.

The all metal has to be designed with clearance or they will bind /gald mmediately, whereas the teflon being self lubricating can be desogned with essentially no clearance between the ball and body.

And slop in rod ends is a recipe for nothing good.

[kea]

I like the Aurora PRM series, with their mil-spec liner and stainless steel race.
Keith

[Chas Shaffer]

Rick,
I'm curious if you've found the Aurora XAMT's to last as long as the Rose rod ends. I was just having this conversation with Keith Averill last week. I've used the Aurora PRM and PRXM ends but was looking at the XAMT's as a cheaper alternative. 12 weekends sounds like a lot of life to me. I've used the NHBB ARHT as well and so far the PRXM's seem to last the longest but at 2 times the cost of the XAMT's I'm not sure which to use.

If anyone else has used the XAMT's I'd be curious to hear your thoughts.

[Rick Kirchner]

Chas - I'm not nearly as fast as you and our tracks are a lot smoother out here. I'd think that you would get much less than 12 weekends.

To give you an idea of the cost delta, an XAM-6T was ~$23.00, while the ATRH-6ECR was about $76.00. It hurts to swallow that bill if the wear characteristics don't support the "higher quality" part.

On the old supervee I could get away with buying junk, because the smallest rod end on the car was a 3/8 - there were even a couple of 3/4", and it didn't have to deal with the forces the FC develops. The smaller parts seem to really show the wear.

As far as the rose joints go, a few weekends back I found some sloppy joints and found myself digging into the pile of stuff that had been taken off before - the old rose stuff was in better shape and still have less slop than the newer XAM stuff.

Glad I started this thread!

[Scott Hutchison]

Rick,

I tried to find a source for Rose joints about a month ago, with no success. I believe Primus has gone to Aurora also now.

I ended up going with Aurora XAM-6Ts. Felt there really wasn't any cost effective alternative.

[jattus]

What to order to replace the rod end in the photo below?
http://www.hrpworld.com/index.cfm?fo...ction=category
http://www.hrpworld.com/index.cfm?fo...action=product
http://www.hrpworld.com/index.cfm?fo...action=product
http://www.hrpworld.com/index.cfm?fo...action=product

[Mark H]

Justin, Im sure you will be told to use the $$ ones but I have used less than the XAM/XAB ones on the last link.

How is the new car? When are yall gonna race?

[S Lathrop]

The "M" series Aurora bearings are set loose from the factory. The "A" have a different setting and are much tighter.

Using the Aurora XAM vs the XMM or the A vs the M may solve your ware problem.

I am very reluctant to use anything but a M series rodend when it is not absolutely necessary. Those high strength rod ends do a lot more damage to chassis and suspension components in a crash.

Sloppy rod ends on the push rods are not necessairly a bad thing. The joints never see osculating loads. We used A series rod ends on the lower a-arms and M series every where else. This has worked very well for the last 20 years.

[jattus]

XAM it is.. If it doesn't work, I have a link and a credit card
Getting ready for the test day for the CMP National - Looks like the 1st race is in March at The Rock; bummer I was looking forward to Road Atlanta then VIR.

[Scott Hutchison]

Steve,

I'm confused.

I just put some Aurora RXAM6T rod ends on my lower front control arms. Are those what you call an A series or an M series? There is both an A and an M in the number.

I don't think I've ever even heard of an XMM rod end. What specific applications are you using the XMMs on?

Thanks.

[Rick Kirchner]

Yeah - I had a lengthy discussion with the Aurora racing sales/tech guy last week and he didn't mention a MM series. When I get some time I'll synopsise our discussion in another post.

[S Lathrop]

M is simply mild steel body. The A is Alloy steel body. X is step size -- shanks larger than the bearing bore. R is a special finish on an alloy body, crome or nickel.

The second M in MM is right hand thread. Left Hand is MB.

XAM is an alloy steel step sized. XM is a mild steel body.

I use a lot of MM6TY rod ends. That is a 3/8 mild steel body, right hand thread, teflon lined(T) and solid shank(Y).

[kea]

The reason the Aurora guy didn't mention the MM series, is because very few use it in a racing application (except Steve). Maybe Formula SAE, but they have a short life. Most cars made today have suspension components, that will fold upon an easy contact, thus the worry of chassis damage from rod-ends that are "too strong" is lessened
The reason we first started using the Aurora PRM/PRXM series, was as a direct replacement (material wise) of the NMB ART/ARHT series when it started to appear on cars, the added bonus was the longer life.
Keith

[S Lathrop]

Keith:

Why not use A and XA series bearings? They cost less. And if a bearing costs 3 to 4 times as much but only lasts twice as long, what do you save? I just buy bearings, I don't sell them.

Most of the rod ends used on club cars are under stressed. But the wholesale use of $50 to $100 rodends when much cheeper will do is a waste of money.

I started using Aurora bearings when I first did the Z16. I have used them ever since. Most of my customers do not have money to waste. I did say that you have to use the appropriate rodend for the application. But of all the rodends on a Citation FC, there are only 6 locations that require anything stronger that a M series Aurora.

In general, I use A series (alloy steel body) in those applications where there is any significant shear loading or high tension loadings. On a Citation that is 6 out of 40 rod ends.

On my new Citation Zetec FC and for the F1000, I will only need 2 A (alloy steel) rod ends. All the other high stress applications I have gone to staked bearings.

[Steve Demeter]

Steve,
What are those 6 locations?

Just want to make sure, I think I know.

Steve Demeter

[S Lathrop]

Inboard end of the front lower a-arm and the outboard front upper a-arm. The front lower inboard a-arm rod end sees a shear load and the push rod loads under sever bumps require that the rear leg has an alloy joint.

On cars where there is a rodend used as the rear upper outer ball joint, that should be a alloy bearing. On the Z16, Z10, and 84 Citation, there should be an alloy joint used as the front lower outer ball joint. The Z10 needs alloy rod ends on the rear lower a-arm, all joints.

[racer27]

Steve,
What are those 6 locations?

Just want to make sure, I think I know.

Steve Demeter

That's a good question, by Steve D. I have a bad habit about being lazy about identifying rod ends and bearings (Even fittings). I don't even try to bother. I just take the suspect unit off, put it in a box, send it off to a Racing Supplier. Normally a week later I get a replacement back. I never thought to consider that the unit could be replaced with something cheaper or better or that it has already been replaced by previous owner with something different then what was installed by the mfg. I normally end up with he exact same part or a direct replacement (if not avail, we go with the higher quality replacement),

Having a parts list would be nice, but with the generational nature of these cars, I'm not sure it is piratical.

[kea]

The higher strength alloy rod-ends, tend to also have a lower breakaway torque over other choices. In some cases, the wear rate is more than twice.
In the old days, rod-ends used (along with their bolts) were bigger, thus the use of less expensive, but larger parts, that lasted because of their overall size.
Another thought on wear. Much of the rod-end and spherical bearing wear is done while the car is bouncing along in the trailer on it's way to the races.
Keith

[S Lathrop]

Keith:

For the Aurora bearings I am familiar with, the alloy steel housings have higher break away torque. That is because they assemble the races tighter. I think that the races are basically the same when they are PTFE lined regardless of the housing material.

[Rick Kirchner]

In a nutshell, what the aurora guy told me was that in highly loaded applications, there is some wear of the race as well as the teflon liner. The analogy he used was putting carpet (the teflon) down over a floor that's half concrete and half wood (the race). Pound on the carpet with a hammer (the ball). The carpet looks like crap everywhere, but when you roll it back the wood is beat up and the concrete isn't. So, even though the majority of wear is in the teflon, in highly loaded locations, the tougher the race, the better. He agrees that in locations where you don't see high loads you might as well use the most cost-effective solution.

With Aurora and NMB, the higher quality parts use the Mil-spec teflon. There are four different grades of teflon used by both manufacturers, and the mil-spec stuff is definately better. It doesn't come on the XAM series however, only on the PRM and up.

He did say that for our applications, for the most part, the strength of the rod end, even low quality ones, was far more than adequate.

He also indicated, that they suspect some suppliers (none of ones that advertise on Apexspeed) have been substituting other guys parts for theirs, so pay attention - Aurora stamps the part number into the race/body interface.

I got to look at some brand new NHBB stuff over at Art Smith's and the breakaway torque was the highest I've ever seen - couldn't be done bare-handed, you would have needed a lever through the ball to get it to move.

Between the shock wear and rod end wear when trailering I'm beginning to think about using one of those inflatable stabilizers.

[S Lathrop]

Rick:

Thanks for the info about teflon. I did not know that. I still hate to pay a bunch for fancy teflon.

I have the luxury of being able to change a design so that cheep stuff works.

[Rick Kirchner]

There's a lot of fantastic engineering data buried in both the NHBB and Aurora web sites. The NHBB guys have a lot of details on teflon and torque.

[kea]

I got to look at some brand new NHBB stuff over at Art Smith's and the breakaway torque was the highest I've ever seen - couldn't be done bare-handed, you would have needed a lever through the ball to get it to move.

This is why I like the low breakaway torque of the PRM/PRXM series from Aurora.
Keith

[Rick Kirchner]

Steve - you mentioned earlier that a little slop on the pushrod ends is not a bad thing. I guess that since the pushrods don't really contribute to alignment except for ride height, and they are always loaded except in the transition to droop, then a couple thou or "thunka thunka" is no big deal.

Question is - how much is too much - what is your standard?