Tuesday, March 4, 2008

Use sealed bearings or not?

I used sealed bearings in my front hub...

I received a great "comment" from Paul B. (thanx Paul it's folks like you that help me and the readers think through things and learn more about our hobby):

"Sealed bearings in the hub? Why?The "open" bearings work great, (as you saw in your own disassembly) and are serviceable, which make them last forever. You have removed the ability to service your bearing. The sealed bearings will NEVER last so long. Grease degrades with time, usage, and heat. How will you renew the grease in your sealed bearings? Why change from a system that works great to a system that limits your options?" - Paul B.

Paul B. is correct that the stock bearing works just great and there is no need to upgrade it.
The reason I upgraded it is two fold:
1. My bearing dealer assured me that with the use of the Vespa that I would likely get40 years of use out of it. 2. There is less chance of grime getting in the bearing and therefore a lower maintenance.

My mentor Christopher Markley is a proponent for installing sealed bearings on the front hub and taking advantage of this "modern" (relatively speaking) technology.

It is my understanding that the later model Vespas came equipped with a sealed bearing in the front hub (but don't quote me -- I am far from an expert) so it is not unheard of in the Vespa world.

Just to play it safe, I checked in with Tom G. and Christopher M. and posed the question, "crap, did I make a bad choice going with a sealed bearing Tom?"

Tom G.'s response was:
"It's not a big deal. Consider the following. Assume your open bearing's grease degrades. I can't recall, but is there a grease nipple that will allow you to
pump replacement grease in (and old grease out?) there isn't on older models -- and if there was, where would the old grease go? Into your brake drum? The fact of the matter is that you'll know when your bearing is having a problem by telltale noises, clicks upon rotation, etc. At that point, you can just replace the bearing. And even if you're running sealed bearings, you can, of course, just pop off the seals, wash out the old grease, and regrease and reinstall (sans seal this time). but its not worth the cost and effort for this particular bearing. Just replace it."

Christopher M.'s response was:
"On the bearing, I'd go sealed. It will always be clean and greased. An unsealed bearing gets corruption in it and degrades the bearing over time. But as you say, why not just go original? It is doubtful that you'll put on the many tens of thousands of miles that would take to wear either out. I'm talking tens of thousands, ridden hard, Italian style, and neglected. You'll be babying this bike. So either will be fine."

(Christopher is correct about the bike being babied. She'll live a garaged or basement life and my wife rides very easy on bikes as opposed to me, who likes to pretend to be a sporty hot dog. Though, I'd like Lisa to be able to ride it often I am concerned that times that she has to leave the bike outside it could get stolen even if locked up or possibly damaged if it's outside all day long while Lisa is at work. So it will be babied and go places where she can keep an eye on it, like weekend coffees.)

So to answer Paul B.'s question, yes I did give up serviceability, but I believe that the bearing will last "long enough" for my wife's riding career (next 30-40 years) without needing to be cleaned or replaced.

The rear hub is a different story.

"The rear hub bearing was definitely unsealed, because there is a separate oil seal used. There is no reason not to use a bearing sealed on the outer side -- in fact, it is extra security against oil seepage. However, I would NOT use a bearing sealed on both sides -- the inside should be open to received lubricating oil from the gearbox," said Tom G.

Nonetheless all very good information for you readers. Food for thought.


Anonymous said...

I think the idea here is not that it will last "long enough". The question is, how will you replace the grease in your sealed bearing? Sealed bearings have been around for a long time, in fact, before your SS was made. Piaggio could have easily popped a sealed bearing in there. Why didn't they? Why did they go to the extra hassle of machining the hub for a oil seal and machining the hub for a end cap, and filling with grease when they could have just put sealed bearings in and moved on? It's my experience that companies don't do extra things if they don't have to since it costs them money, and therefore lost profits, to do so. A couple reasons I think. First, grease doesn't last forever. That's why there is a service interval with the original hub open bearings. Not to get the dirt out (they don't get dirty anyway, that's what the end cap and oil seal is for). The service interval is grease every 2,400 miles. Not every 30-40 years when you change the sealed bearings. Second, you still have to grease the speedometer drive, so you still have to put grease in the hub anyway, but, by using the sealed bearings, what you are in affect saying is "I'm going to put new grease in the hub to keep the axle and speedo. drive lubed, but I want to make sure I don't get any new grease in my axle bearings." Just because a bearing is sealed doesn't mean that the grease inside the bearing is some kind of super mega-grease that will last longer than mere mortal grease. It still has to be changed. Sealed bearings are used more in (a) hostile environments (acids, particulates, high pressure water, etc) and (b) in most peoples usage, low stress, intermittent use, like your vacuum, your power drill, and your hairdryer. Not a scooter axle whizzing along at 60 mph with all kinds of stresses and heat. It's easy to dismiss those Italian sscooter makers of yore, but those Piaggio engineers really knew their stuff. Second guessing them, for the most part, doesn't end well. Also, (I'm guessing here based on much British sportscar and Italian scooter experiences), European machines are designed to be able to be serviced by the owner with parts that last a LONG time if the services are done. It's the American "service" idea to use a part until it breaks then throw it out and get another one. The flaw with that is the thought that things fail in isolation. They don't. If the axle bearing fails, what else goes with it? Hub? Axle? In my opinion, this is in part why American mechanical stuff is usually so hugely over engineered; otherwise, you would have stuff failing all the time!
Well, my two lire.... :)
Paul B.

Scooter Couple said...

Well said and thanx Paul B.

When my bearing first shows signs of wear I will replace with a stock bearing.

And your logic sounds sound.