Rear wheel bearings

[2CoolWheels]

Hi Bruce or Jumper,
   Please give me the low down on the rear wheel bearing upgrade. What bearings should we be using? Can any machine shop enlarge the hub for the upgraded bearings? Thanks,
 Mike

[Jumper]

Mike..
The Mod that most are doing is to have your machine shop bore out the drive side hub, sleeve it with a stainless sleeve, then use double row of bearings (6205's) on the drive side. You might call Jamie and ask for clarification as I've been know to leave details out.
Jumper

[2CoolWheels]

Jumper,
   Thanks, that's what I wanted to know.....what bearings were best to use. I'll pick some up and talk to my local machine shop about making them work.
    Mike

[Donkey Hotey]

I hope that people are NOT using stainless steel for the insert. Stainless and aluminum do not like each other in the presence of ANY moisture.

http://en.wikipedia.org/wiki/Galvanic_corrosion

I'd use either a 4000 series steel (4130, 4340, etc) or 1000 series mild steel (1010, 1018, etc). It all sounds like engineering mumbo-jumbo but, the metals I mentioned are actually very common grades of steel that most machine shops and metal supply places are used to dealing with.

The potential when using stainless is that the aluminum will chemically turn to powder around the outside of the insert. After that, you're right back where you started, with a blown-out hole and things knocking around.

[2CoolWheels]

I'm not really sure how the 6205 is an improvement over the 5305 bearing that's already there. The 6205 has a slightly smaller outside diameter, I assume that's the reason for the sleeve (insert). The 5305 is supposedly a double row ball bearing, so is the installation of two single row 6205 bearings really advantageous? The two 6205 bearings (at 15mm wide each) is only slightly wider than the single 5305 (at 26mm wide). Or did someone already do an upgrade to my rear wheel? 

[Donkey Hotey]

All four wheel bearings (front and rear) in the parts list are identical. It sounds like yours has been updated in some way.

Thanks for the tips on the bearing sizes. Just one more thing to add to the list of stuff to do.

[AtlanticMarty]

Everyone it totally missing the point.  The stock 6205 wheel bearings are just fine.  Many years ago we sent a wheel and bearings w/additional data to Timkin and their engineers verified that.  We were told the bearing in question was rated for far more RPMs than our bike could produce and was an excellent choice for the application.

THE PROBLEM IS WITH THE CAST ALUMINUM HUBS!!!!!!!!!!!

Every time you take off hard or accelerate with gusto the drive belt pulls  on the driven pulley.  This energy is transmitted to the axle and the steel jacked bearing slams into the wall of the hub.   Over time the bearing begins to cut out or erode the hub.  The RH or drive side can get totally wallowed out.  This causes a wobble you cannot ignore.  Even gentle riders can have this happen, but more slowly.   Your weight, belt adjustment and carrying a passenger can speed up the process.

The time-tested solution is to bore the damaged hub past the cut and then press fit a steel sleeve that has been milled on the RH side to take two of the stock bearings.  This is just a precaution that gives more support to the axle.  We have been doing this for years and have yet to hear of a failure of any kind.  We do a lot of new wheels so that the problem never comes up for the owner.  It is considered an important upgrade as it can be a safety issue.

We have had about 5 bikes in the shop over time that had the large wheel bearing.  They were all eating the hub.  This means more material has to be removed (depending on the amount of damage) which may compromise the hub.  We don't like this option.  Always keep in mind when working with your wheels that they are the only ones we have.  There is no alternative that fits our bikes--so respect them.

P.S.  Check your spokes and nipples regularly.  You can get a spoke wrench at your local bicycle shop.  They do get loose and they can break or break the hub. 

[2CoolWheels]

Marty,
   Thanks for clarifying this for me. Now I understand the situation. The 5305 currently in my hub must have been an upgrade, right? I know when 741 was new, Bobby Baldwin did upgrades on it, this must have been one.
    Mike

[wytfut]

Thanx Marty....
    we all like to know what the details are...
    Interesting note... and I'm not saying what I am doing presently is solving anything, but I run my belt extra slack.... well so slack, that I have to adjust so that it won't jump cog.
    I maybe a gentle rider... who knew... but I've got close to 30k now... changed my last set of bearings at 20k... and the ones that were in the hub were from what I could tell fine.
    But then again, I may just be lucky?
    I know I'm gonna be paying extra attention now....
Brucester...

[2CoolWheels]

I received the 6205 bearings I ordered.....I'll use them on 901 when the time comes because I can't use them on 741, it's been modified. I'll have to replace the bearing with another 5305, since it's binding a bit. Thanks for all the input guys!

[blackheart]

I hate to open up a new can of worms but there was recently information made known to us which helps explain all of this between belt tension, engine crank balance factor, and this long standing wheel bearing issue.

First off the aluminum hubs are not the problem, millions of motorcycles have been built without steel sleeves.  They add to the issue but it is not the root cause.  Properly fit & loaded the 6205 applied as a wheel bearing will be just fine.

The loading is the problem.  Some time ago a fellow who had some ties to one of the engineers familiar with the engine balance factor explained EH chose to balance at 30% which results in increased longitudinal motion, i.e. fore to aft, of the power train in the chassis.  He explained the reason they did this was to decrease vertical vibration which the rider feels & instead increase the longitudinal vibration which isn't as easily felt by the rider.  Here in lies the problem.  The longitudinal vibration when combined with the proper belt tension put a severe shock loading into the bearing.  The bearing, being robust doesn't really fail, however, it results in loss of interference fit between the outer race & hub.  The aluminum frets away easily upon minute relative motion between the outer race and hub bore.  By sleeving in steel & doubling up on bearings we are increasing the surface area to take the spike energy from the belt load.  By loosening the belt, this hurts belt life but solves the bearing issue.  It also probably will help ensure long life out of the transmission output bearing.

Thus the root cause is too high of vibration in the fore to aft direction combined with design tension drive belts.

Ball bearings for mass application are specified with a class of fit.  This fit allows the designer to apply proper interference fit to the appropriate race of the bearing.  On a wheel bearing the primary load is determinant and constant with the load varying  (rotating) about the outer race.  Thus on a wheel bearing you interference fit the outer race since it rotates relative to the load.  With proper fit & loading, loss of fit won't occur with frequency to be considered a design fault.  Because off the shelf common ball bearings are supplied with a C3 fit, one is limited to the interference fit applied to the bearing based on design reduction of internal clearance.  The bearing designers account for this interference fit of either the inner, outer, or both races to arrive at the proper clearance after mounting.  One possible solution is to increase the interference fit of the outer race, but in order to do this you'd need to order a bearing with a looser fit, such as a C4 fit, this then will allow a tighter fit on the outer race.  Typically for high dynamic loading with a lot of shock bearings are fit tighter in their bores to stave off the process of corrosion fretting which is the beginning of the loss of interference fit between the outer race and bore (or inner race or both in other applications).  All this assumes the hub is sufficiently rigid to provide proper support if the interference fit is increased.  One would never want to increase the interference fit beyond that recommended by the bearing manufacturer.

To me the best solution would be the use of a tapered roller bearing to both sides.  This would allow maximum interference fit of the outer race while setting clearance with the custom ground spacer between the two cones.  But then you have a whole new problem with possible issues of the hub not being made for the required bore and seal issues.

Obviously if you've lost your fit, sleeving and running two 6205 bearings is the right thing to do as it is the lowest cost solution.  For those of us who have not yet lost the fit, by running the belt loose we may well extend the life of the bearing to not be a problem.

This whole issue is just another design development issue which EH would have resolved in due time had they continued  to survive.  Most likely had they not rubber mounted the engine it would never have surfaced.

[wytfut]

Rich... (blackheart)...
I'm sure anyone of us could pick a topic concerning our scoots and to someone it would be redundant and maybe even painful.
back in the day, engine oil discussions were off the charts (on the old dealer 38 site)... and it appeared here in the flat lands almost postal ....

Interesting you should bring this topic up again....   as I just suffered a failure on my rear bearings (actually belt side bearing). I had been back from the cannonball a couple of weeks, tooling around here and there, when I noticed a huge change in steering.... well huge to me. It was like driving a bike with a bias tread car tire.... nice and easy, and all of a sudden a huge feel in the grips..
Initially thought it was a tire pressure issue..... but got to pulling the rear wheel, and that bearing just fell out as soon as I got the cap off. Amazingly, it did knurl the hub the bit, but nothing drastic as some of the horror stories I've heard...  The bearing showed scoring on the race.... and spinning the bearing you could feel it slightly grind...   

Maybe its my age, but for some reason, it feels like sometimes us west of the mississippi don't get all the details or direct information near as quick as those close to Marty/Jamie. I know they get visitors there, just for leisurely time....    that exposes them to the lastest trend, but maybe not fully solved that Jamie is working on....    nothing wrong with it, but here, it leads me to misdirection. It has happened several embarrassing times to me...        As Jamie told me in our last conversation, Just call me...

Rich.... you have a wealth of knowledge about dynamics of bearings and weights... so much so... I got lost a few times in your data.... no biggie, I think I pretty much followed ....

With my hub knurled I immediately called jamie.... and had a lot of lengthy discussion. As I was trying to get a buddy to do this work for me, to save some pennies....    The jones price at this time is out of my budget. My buddy has huge talents, but doesn't trust own physical skills. Lucky for me at this time, I had a spare wheel... and just put new bearings in it....mount, dismount, bearings... all for around 70bux. Jamie/Martys solution, costs including shipping around 250.00... but it does work, and work well.

I want to point out that I run my belt very loose. Since I got 525, and the previous owner had also. My first set of bearings I replaced at 20k .... as that sounded reasonable, and they showed no problem. My second set (this set), only made it to 16k, for that one bearing to fail.  My nephew Devin is riding Blue, and its on the rack for this winters tinkering,... with 16k on its bearings. We will be replacing them, knowing how mine went.

Lastly Rich, your comment about belt life. I have Jeff Browns broken belt in my shop.... and I frequently look at it. Anyone who knows jeff, knows he is as mild of a rider as they come. To me his belt looks like an isolated expample. Do you think maybe its due to running it loose? As the belt is an inanimate object, would there be a way for shade tree guys to detect belt issues due to slack belt and wear?

Great to hear from you again....   
And I hope all of you have a very merry Xmas with your loved ones....

Bruce

[blackheart]

Bruce:

My main point was I'm sure EH did not engineer this themselves.  Behr or whomever supplied the wheel assembles.

HD did not advance to a 1" bore bearing until the early to mid 2000's then converting to the cheaper and more common metric bore of 25mm, i.e. 6205 bearing until 2008.  It's not the bearing.  A full dress HD CVO bike with the bigger engine surely loads the bearing more than the Super X, EXCEPT when you consider HD mounts the swingarm to the power train, NOT the frame.

I still think your issue is related to vibration and high dynamic loading into the bearing.

I'd like to look at these hubs sometime.  I'm about due to change my rear tire, so maybe I can then.  I'll bore & sleeve mine on a mill.  If I can make it work I still think a good tapered roller bearing is best, but it will be more pain since I need a sleeve to set endplay. 

Another note.  Don't buy no name bearings.  Look for SKF, Timken, NSK, etc.  NTN & Nachi are OK too.  I've noted those BCA bearings from O'Reilly auto many times are boxed up no name China bearings.  But, even the best bearing not loaded properly will fail.

On a fun note I got 307 out today.

[2CoolWheels]

Hi guys,
   Since originally posting this back in 2012, I did the necessary upgrade on 901. Then last year, I must have picked up something in my back wheel. I found that two spokes had been broken away from the hub due the flange of the hub being broken. I ended up having to purchase another rear wheel, but wouldn't you know it....no bearing upgrade had been done. So, I paid my local machinist $200 to do it all over again on the new wheel.
   Interesting that you mentioned the drive belt, Bruce. When I got 901 home from the trip I took with you, about a week later the belt simply snapped. It was never very tight, if fact, seemed too loose to me. The bike had less than 8000 miles on it at the time. I suspect it was simply a defect in manufacturing. It's a good thing it didn't break on the long ride from your place to California!!