1WD vs. 2WD performance differences?

[roscoau]

Originally Posted by Ural Australia

BMW, IMZ, KMZ and others ALL went to tapered wheel bearings for a reason - they take the lateral stresses a sidecar imposes on the wheels. IMZ has gone to sealed wheel bearings for two reasons - they're cheaper and dumb-arse owners won't get greasy adjusting the tapered bearings. Forget over 50 years of practical experience - listen to idiots that don't ride sidecars for any great distance! What's next? Stainless steel spokes and alloy rims? You better bet!

You are entirely correct, but is there a history of decreased bearing life in the newer bikes?

Tapered rollers would seem the obvious choice, but perhaps the number of people stuffing the re-greasing and adjustment up offset the use of the less than ideal sealed bearings?

[roscoau]

Originally Posted by windmill

Bearing grease, like oil has a finite service life.

In this case SKF consider that to be for the life of the bearing. The point that matters is that once the seal has been removed the bearing cannot be considered a sealed bearing. The seal may go back in and look good, but the fit will never be the way it was from the factory.

Anyhow, it's your business what you do. I was just concerned that someone new to it was being told this as if it were fact.

http://www.engineeringtalk.com/news/skf/skf390.html

The sealed spherical roller bearings are protected against both particle and moisture contamination, enabling them to offer effective performance over long, virtually maintenance-free service live

http://www.alliedbearings.com/downloads/skfsealed.pdf

Sealed bearings do not need relubrication when the temperatures do not exceed 70 °C (158 °F) and speed are not more than 50 % of the speed rating listed in the product tables.

http://en.lily-bearing.com/Bearing_news/08051303.htm

The sealed spherical roller bearings are protected against both particle and moisture contamination, enabling them to offer effective performance over long, virtually maintenance free service lives.

And if your bearings are reaching 70C you have other problems...

[hoagy]

Originally Posted by windmill

I have 33000+ km on the sealed bearings, and they still look like new, no reason to change them out until needed.

nor would i, just good to know that is an option.

hoagy

[Ural Australia]

Originally Posted by roscoau

You are entirely correct, but is there a history of decreased bearing life in the newer bikes?

Tapered rollers would seem the obvious choice, but perhaps the number of people stuffing the re-greasing and adjustment up offset the use of the less than ideal sealed bearings?

The tapered roller bearings had an estimated life of well over 1,000,000 km if properly adjusted and over 250,000 km if over-adjusted. Under-adjustment could destroy a bearing in 50,000 km in the worst case scenario.

During testing of the sealed bearings the test riders could destroy the bearings in a few days. However, that being said, they were all sidecar motocross racers and they were testing on the Mel'nikov Hippodrome Motocross track and on a "road" circuit where they knew the local DPS (Highway Patrol) so the bearings would have been operating under extreme conditions that wouldn't be easily replicated.

There have been a number of reports of bearing problems on sidecar wheels at low mileages, but again the reports seem to indicate incorrect set-up by the delivering dealers.

My own experience with an XS11 outfit was that plain bearings required regular replacement in the rear wheel. I just made it part of the annual super-service.

Originally Posted by roscoau

And if your bearings are reaching 70C you have other problems...

If you run an infrared thermometer over your rear wheel after a long fast run with plenty of hard braking you might get a bit of a surprise! It gets pretty warm back there.

[Bueller]

Originally Posted by windmill

Bearing grease, like oil has a finite service life. In an ideal situation, the service life should exceed the service life of the motorcycle, But a wheel bearing in a brake drum is subject to heat, brake dust, immersion, and rapid heating, and cooling cycles. A sealed bearing not being serviceable, or maintenance free is well debated question. It is possible to damage a seal if very careless, or failing to completely clean the bearing before re greasing, or over greasing can cause problems. Like anything mechanical, if in doubt, replace. I know it is strictly anecdotal, On the many off road bikes I have owned, I have never had a sealed bearing I serviced fail, but I have had bearings fail that I neglected service.

Every modern car you drive and almost every modern motorcycle is running around on sealed bearings. There are no maintenance intervals to grease the bearings. They last hundreds of thousands of miles on average. Harley uses the same sealed bearings for their motorcycles that they use for their motorcycles with sidecars.

I'm not trying to tell you what to do, I just think it is an unnecessary step. If the bearing is routinely cooking the grease or getting infiltrated with dirt you have the wrong bearing in that application.

[windmill]

Originally Posted by Bueller

Every modern car you drive and almost every modern motorcycle is running around on sealed bearings. There are no maintenance intervals to grease the bearings. They last hundreds of thousands of miles on average. Harley uses the same sealed bearings for their motorcycles that they use for their motorcycles with sidecars.

I'm not trying to tell you what to do, I just think it is an unnecessary step. If the bearing is routinely cooking the grease or getting infiltrated with dirt you have the wrong bearing in that application.

I've never had a bearing fail on a street bike, the few times I have had problems were on dirt bikes. I Checked, and re greased the bearings on My Ural at 15000, and 30000, both times they looked perfect, it was just pm. I do a lot of riding in wet, snow, and mud, and steep downgrades on some local mountain logging roads can get the drum brakes hot enough to burn skin.

I always believed the same as You about sealed bearings. A member of a tractor club I belong to is a retired heavy equipment engineer, His company built and maintained oil field equipment. He convinced Me there is nothing injudicious about servicing sealed bearings. If it's ok for the Alaska oil fields, it's ok for me. It may be unnecessary, but I enjoy doing it, and I know they are good.

In a way I can agree it doesn't make sense to do it, for a bike, or car dealer, labor would cost more than the bearing. A wheel bearing for a Ural is about $25. At $90 an hour shop rates, I would opt for just replacing them if I was paying to have it done.