Go Back   Horizons Unlimited - The HUBB > Technical, Bike forums > BMW Tech

BMW Tech BMW Tech Forum - For Questions specific and of interest to BMW riders only. Questions comparing which bike is best etc go in the "Which Bike" forum.
Contact Overland Solutions for all your custom modifications and setup for overland travel.

Calendar Contest Voting is now CLOSED. Results to be posted shortly.


7 Litre Camel Tank Lets You Explore More, Click to Find out More!

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 5 Jun 2008
Registered Users
Veteran HUBBer
 
Join Date: May 2006
Location: Melbourne
Posts: 167
question about bearing speed ratings

g'day.

i just bought a spare final drive bearing for my r11gs. i was able to obtain the right size, but without the 'C3' rating for rpm.

as i understand it, high-speed rated bearings have a little more space between race and balls, i assume to allow for heating at speed. can anyone add to this?

the bearing i bought is NTN, should be good. though not C3, it is rated to 6300rpm, and my maths tells me that at 120km/h, my rear wheel is turning at about 1000rpm. according to the following maths:

c (circumference) = 2 x pi x r,
where r = .33m,
c = 2.1m

right, why should C3 speed rating be required at all when there is such a wide margin (6300 - 1000 = 5300) between real-world rotation speed and the rated tolerance?

i have not yet fitted the bearing. can anyone suggest why i would not? any input welcome and appreciated.

cheers,
andy.
__________________
www.outforaspin.blogspot.com
Reply With Quote
  #2  
Old 5 Jun 2008
Registered Users
Veteran HUBBer
 
Join Date: Sep 2003
Location: Still homeless
Posts: 768
Not a bearing specialist myself, but didn't BMW changed the ball numbers inside the main FD bearing? First it was something like a 17 balls and later 19 (not sure if the numbers are correct, but the difference was 1-2 balls) because of better tolerance capability.

My mind says it's all a compromise between a high speed and huge load. For huge load more balls seem to be a better option, since there's more support area in the bearing to take that load, while it'll be limited for speed (more drag=heat and wear!). Less balls mean better speed tolerance, but probably also less load tolerance (less "support" area in between the bearing race and balls).

R11xxGS main bevel box bearing is C3 rated in stock - 'C3' means there should be increased radial clearance between the inner race and outer race, usually used for bearings that are going to run fast and hot.

So I can't see how speed can be a "problem" (R11xxGSes are rated to 200km/h speeds), I rather see the load (big bike, 2 up, lot of luggage) and potholes/harsh road conditions as a threat to the bearing longetivity.

Anyways, make sure you shim it correctly on puting it on (=correct preload) - wrong shimming will cause it broke down after just few hundred miles to few thousand, since it'll start to wear out one side of the race coz it's preloaded (by shims) wrong. If you preload it precisely right, then I've seen them lasting for 150,000+miles! So it can be kind of "lottery" between the precision of the work versus the real-life road conditions and your riding style. Some last 10K miles, others last even stunning (for the bike that has been riding offroad too, not just smooth tarmac like Goldwings etc do) 200+K miles I've heard in UKGSer forum.

Always, being a bit paranoid person muyself not to be involved into the "lottery" game - I carry a spare main bearing, main seal and few different sizes of shims with me on my travels. They're so called "GSers spare chain kit" - but they cost less than a good chain/sprocket kit, take much less room and weight less too. I bought mine from BMW since the same bearing from bearing shop was more expensive than from BMW.

Ride safe, Margus

Last edited by Margus; 5 Jun 2008 at 08:21.
Reply With Quote
  #3  
Old 5 Jun 2008
Contributing Member
Veteran HUBBer
 
Join Date: Jan 2006
Location: Sheffield
Posts: 1,038
Wheel bearings are bearings are bearings. Based on my (limited) experience the only bearings that need special construction are things like cam roller bearings, as these rotate at several times engine rpm.

Whenever I have to replace a bearing I just order the same bearing based on the number stamped on the side (- Simply Bearings Ltd), which is generic across all jap bearing manufacturers. The only non-generic bearing I have used was a ceramic bearing from a skateboard (used the wheel as a chain roller, works GREAT)
Reply With Quote
  #4  
Old 24 Jun 2008
Registered Users
HUBB regular
 
Join Date: May 2007
Location: Riyadh
Posts: 27
What are C3 bearings?

What are C3 bearings?

C3 bearings are bearings that have an additional internal radial clearance to cope with high speed environments where excess heat is generated.
They are not suited to environments where critical alignment is required from the onset e.g. Where blades and cutters are set up to each other.
Applications like motorcycle wheels or bicycle wheels do not require C3 rated bearings.
Unless the bearing you are replacing specifically says C3 on it then you should not replace it with a C3 bearing, C3 Bearings are loose to the feel from new and often people complain at the quality of the bearing being poor and having more movement than the one they are replacing.
This is the characteristic of a C3 bearing.
Reply With Quote
  #5  
Old 24 Jun 2008
Registered Users
Veteran HUBBer
 
Join Date: Oct 2006
Location: Northumberland
Posts: 173
Quote:
Originally Posted by henryuk View Post
only bearings that need special construction are things like cam roller bearings, as these rotate at several times engine rpm.
Cam's actually run at half the RPM speed of the engine.
__________________
Home of the UK Coast 2 Coast off-road Challenge
www.C2CChallenge.co.uk www.4X4Safari.co.uk
Reply With Quote
  #6  
Old 25 Jun 2008
Registered Users
New on the HUBB
 
Join Date: Jun 2008
Location: BC, Canada
Posts: 7
Just to weigh in on this "C3" issue ...
it is correct that C3 indicates a "larger than standard" internal clearance but this suggests a tolerance "range". There is more than 50% overlap in the internal clearance "probability" between a standard and a C3 ball bearing.
Heat expansion of the shaft (especially on an electric motor) would tend to suggest a C3 bearing. At the speeds you're talking about, I wouldn't worry about C3 or not ... but C3 is quickly becoming the default here in North America.
Reply With Quote
  #7  
Old 25 Jun 2008
Registered Users
Veteran HUBBer
 
Join Date: Feb 2006
Posts: 1,489
This is interesting because Later Triumphs (post 1981) went from a C3 main bearing to a C2. But I do not know what the constructional difference is in actuality.. Are the C2 bearings capable of carry a heavier load ?
Reply With Quote
  #8  
Old 26 Jun 2008
Registered Users
New on the HUBB
 
Join Date: Jun 2008
Location: BC, Canada
Posts: 7
Ironically, C2 has an even "tighter" than "standard" (or C0) internal clearance.
Two steps tighter than C3.
Definitely won't provide a higher load capacity but will give better radial and axial running accuracy.
The entire bearing will tend to heat and cool at the same rate so a tight internal clearance running in an oil bath is a pretty stable application.
Reply With Quote
  #9  
Old 26 Jun 2008
Registered Users
Veteran HUBBer
 
Join Date: Feb 2006
Posts: 1,489
It is the crankshaft main bearing on the 750 twins. prior to that and on the 650's they ran C3's the 650's revved much higher.
Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 Registered Users and/or Members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Land Rover Wheel Weight Load Ratings nickt Land Rover Overland Tech 18 1 Nov 2009 00:10
'02 mainshaft bearing neil.larsen KTM Tech 8 3 May 2005 18:44
04' GS Rod Bearing? NorCal BMW Tech 2 20 Jan 2005 19:06
640 main bearing failure...... city2surf KTM Tech 3 19 Oct 2004 15:56
cranckshaft loose in bearing peterkik Yamaha Tech 1 16 Oct 2002 01:33

 
 



HU DVD Spring Special!

Buy the Achievable Dream Collectors Set and get Road Heroes Part 1 FREE!

Achievable Dream - The Whole Enchilada!

Cooped up indoors in crap weather? Binge watch over 20 hours of inspiring, informative and entertaining stories and tips from 150 travellers! Check it out at the HU Store! Remember to order them both and use Coupon Code 'BoxSet+' on your order when you checkout.


What others say about HU...

"I just wanted to say thanks for doing this and sharing so much with the rest of us." Dave, USA

"Your website is a mecca of valuable information and the DVD series is informative, entertaining, and inspiring! The new look of the website is very impressive, updated and catchy. Thank you so very much!" Jennifer, Canada

"...Great site. Keep up the good work." Murray and Carmen, Australia

"We just finished a 7 month 22,000+ mile scouting trip from Alaska to the bottom of Chile and I can't tell you how many times we referred to your site for help. From how to adjust your valves, to where to stay in the back country of Peru. Horizons Unlimited was a key player in our success. Motorcycle enthusiasts from around the world are in debt to your services." Alaska Riders


contest pic

10th Annual HU Travellers Photo Contest is on now! This is an opportunity for YOU to show us your best photos and win prizes!

NEW! HU 2014 Adventure Travel T-shirts! are now available in several colors! Be the first kid on your block to have them! New lower prices on synths!

HU 2014 T-shirts now in!

Check out the new Gildan Performance cotton-feel t-shirt - 100% poly, feels like soft cotton!


What turns you on to motorcycle travel?


Global Rescue, WORLDwide evacuation services for EVERYONE

Global Rescue is the premier provider of medical, security and evacuation services worldwide and is the only company that will come to you, wherever you are, and evacuate you to your home hospital of choice. Additionally, Global Rescue places no restrictions on country of citizenship - all nationalities are eligible to sign-up!




New to Horizons Unlimited?

New to motorcycle travelling? New to the HU site? Confused? Too many options? It's really very simple - just 4 easy steps!

Horizons Unlimited was founded in 1997 by Grant and Susan Johnson following their journey around the world on a BMW R80 G/S motorcycle.

Susan and Grant Johnson Read more about Grant & Susan's story

Membership - help keep us going!

Horizons Unlimited is not a big multi-national company, just two people who love motorcycle travel and have grown what started as a hobby in 1997 into a full time job (usually 8-10 hours per day and 7 days a week) and a labour of love. To keep it going and a roof over our heads, we run events (22 this year!); we sell inspirational and informative DVDs; we have a few selected advertisers; and we make a small amount from memberships.

You don't have to be a Member to come to an HU meeting, access the website, the HUBB or to receive the e-zine. What you get for your membership contribution is our sincere gratitude, good karma and knowing that you're helping to keep the motorcycle travel dream alive. Contributing Members and Gold Members do get additional features on the HUBB. Here's a list of all the Member benefits on the HUBB.



Books & DVDs

amazon

All the best travel books and videos listed and often reviewed on HU's famous Books page. Check it out and get great travel books from all over the world.


Motorcycle Express for shipping and insurance!

Motorcycle Express

MC Air Shipping, (uncrated) USA / Canada / Europe and other areas. Be sure to say "Horizons Unlimited" to get your $25 discount on Shipping!
Insurance - see: For foreigners traveling in US and Canada and for Americans and Canadians traveling in other countries, then mail it to MC Express and get your HU $15 discount!






All times are GMT +1. The time now is 21:49.