Picture of Worn Out Rear Monoballs

[VFR750]

Here are the old spherical bearings from my Elephant Racing Rear Trailing Arm Monoballs.

The left lasted 45,000 miles, the right just came out yesterday after 50,000 miles.

Seems the ball stays pretty tight in the outer race until the chrome plating is defeated. Then the wear rate increases exponentially. You can see how deep the grooves are. The one on the right was fine at 45,000 miles, and sometime this fall it started to fail. Maybe noticed it in November, definitely toast in December

This makes for very erratic handling. The loose monoball allows for a large change in rear toe angle. I found out a week ago when out for a drive in windy weather. I found myself suddenly veering in the lane when a gust would push the weight side to side and effectively steer the car from behind.


How do you know it's the culprit: With the car on the ground, grab the rear wheel and push in and pull out. You don't have to push very hard either. Any motion and/or clicking in the rear suspension means you have a problem. Assuming the wheel bearings are OK, it is time.

You need to take the trailing arm off, remove the c-clip, and press the bearing out.

COM-10T, ~$5.00 each. Press the new one in, Reuse the c-clip. Add the weather seals, as they are no longer available. Reinstall the trailing arm.

When they are new, the handling is super crisp. Worth it. Lasted 45,000-50,000 miles with ~70 track days since 2004.

[jpnovak]

great feedback. Thank you for posting this.

[betterair]

+1 Also appreciated. Thanks.
I'm surprised the failure would be affect the steering enough to move the car laterally.

[jjeffries]

VFR, not to sound anti-Chinese, but do you feel an equivalent "name-brand" bearing would have lasted longer? Better chrome finishing etc? Best, John (in Tolland)

[VFR750]

I am not sure if the bearing manufacturer mattered. But, I did order new one made by FK, which is a US. Same price as generic.

I think the service life is affected by rain, dirt and g-loading from track use with sticky tires. Eventually things wear out.

I found that my car, with refreshed suspension, mono balls and poly bronze bushings was very precise and immediate. Steering is crisp and you know what it is going to do.

This is the second time I experienced the feeling of unintended rear steer.

It was a sudden input, heighten by the underlying precision of the rest of the chassis. Not “dive across the road” looseness. More of a sudden added rotation that required an immediate steering correction.

[tperazzo]

Thank you for the heads up. You are very in tune with your car to notice this.

[kuehl]

Find a local machine shop that has a rockwell tester, check the hardness of the ball where the chrome wore off.

[VFR750]

I don’t think ball hardness really matter. Chrome plating is significantly harder and wear resistant than steel. If the ball had been too weak, the chrome would have failed very quickly because it is brittle and a softer sub-surface would have deformed quickly leading to local cracking.

And the breakdown of the Teflon liner will cause the load to pile up on the edge of the outer race and concentrate the contact stress on the chrome and steel.

My feeling is this is simply a wear item, it was time.

[kuehl]

I wonder what the thickness of the hard chrome is

[walt]

I think if the base hardness is insufficient the chrome plating will give way. Have seen this happen in other applications before.

[Bill Verburg]

There was no Teflon liner?

[KTL]

COM10T and the T = teflon liner. Over time the liner gets pounded out of the race and you're left with a gap. Then the hammering effect begins. It's also an issue with the front strut upper monoballs.

https://www.fkrodends.com/products/spherical-bearings/commercial-series/com/

[VFR750]

COM-14T front monoballs showing up today.

Yup. Time to replace them all.

The Teflon does slowly breakdown.

[VFR750]

Not impressed with FK bearings.

Hammer stamped the part numbers. Very deep. Why?

[Reiver]

Why buy anything Chinese when other options are available.... for quality and for other reasons.
They steal what we develop and invent with impunity...anyone been to SEMA and watched the Chinese 'vendors' taking pics of everything/anything 'new' with measuring devices etc....
I know it is hard to totally get out of their products but I try.

[jjeffries]

I'm only a few towns away, but haven't had the privilege of meeting VFR yet, but we have a mutual friend and I'm betting he knows his stuff when it comes to bearings.

Why? Because this is Connecticut and goshdarnit, this is bearing country! Or, more accurately, it used to be, with Torrington, Stanley, Pratt & Whitney, Sikorsky, Hamilton Standard, Chance Vought et al either making bearings or using them to build amazing machines.

VFR, do you know AB Athmus in Springfield? Fantastic old-skool bearing supply-house. I went there to buy my steering rack rebuild bearings; could have mail-ordered them but wanted to see the place in person.

Reiver, I hear you.

Best to all, John

[VFR750]

John

I am not familiar with AB. Didn’t know they existed. Thanks.

[KTL]

I think it’s EB Atmus.....

[jjeffries]

Yes, KTL is corrèct. In the south end of Springfield, 65 Main St., wicked cool place, nice people, like a trip back in time.

ebatmus.com