[Ducati] front wheel bearings - c3 or not c3?

[Scott Cloninger]

Tom,

According to FAGs bearing catalog 6005.2RSR is rated for a dynamic load of 2280 pounds and a static load of 1320 pounds with a limiting speed of 9,500 rpm.  They list no 6005.2RSR.C3.  They do list a 6005.2ZR.C3 which carries the same loads but has a limiting speed of 15,000 rpm.  .2ZR designates metal shields on each side of the bearing and, as you stated in your original email, .C3 designates greater than normal bearing clearance.

Since both bearings have the same load carrying capacity, then rotational speed should be the deciding factor when considering which bearing is most suitable for this application.

The rolling radius of a 120/70-17 tire (which I think is what is used on the front of your ST2) is 299.9mm.  That yields a circumference of 942.2mm or 37.1".  At 150 mph you are traveling at 2.5 miles per minute or 13,200 feet per minute, which yields 158,400 inches per minute.  158,400 inches per minute divided by 37.1 inches per revolution = 4270 revolutions per minute...well within the rating for the standard 6005-2RSR bearing.  In fact, it gives you an approximately 2:1 margin of safety with respect to rotational speed assuming you don't exceed 150mph very often....I know I don't!  In my professional opinion, it should work.

To back this up a little, I can say that I've used standard 6005 bearings from the local bearing house in my bike for years to no adverse effect.  I check them every time I change tires (every 2000-3000 miles) and I haven't had to change them in over five years.  I suspect you're actually using a 6005.2RSR, though, which would designate a bearing with two seals (one on each side of the bearing).  I find no .2RSH designator in my catalogs.

Hope this helps.

Scott Cloninger, P.E. (That's Professional Engineer)
Chattanooga, TN

-----Original Message-----
From: Tom [mailto:st2_ at ticino.com]
Sent: Friday, August 04, 2006 2:19 AM
To: Ducati Owners Group
Subject: [Ducati] front wheel bearings - c3 or not c3?


I need to replace my front wheel bearings, and the number on them is 
6005-2RSH, but I thought that I read that they should be /C3 (larger than 
nominal clearance).



Anyone know for sure, and if they should be /C3, why?



Thanks,



Tom



P.S.  This is for the Marchesini on my ST2, but I think most Ducatis use the 
same (my SS does).






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