Britbike forum

Classic British SparesKlempf British PartsBaxter CycleBritBike Sponsor SteadfastCyclesThe Bonneville ShopLowbrow CustomsGirling Classic MotorcycleLucas Classic MotorcycleHepolite PistonsIndustrial tec supply Classic Bike Parts Cheshire

Upgrade Your membership! Premium Membership Gold Membership Vendor Membership

New Sponsor post
July 4th Sale at The Bonneville Shop
by The Bonneville Shop - 07/01/22 6:26 pm
New FAQ post
Member Spotlight
Les P
Les P
.
Posts: 618
Joined: August 2014
ShoutChat
Comment Guidelines: Do post respectful and insightful comments. Don't flame, hate, spam.
Top Posters(30 Days)
quinten 65
kevin 60
DavidP 58
Top Likes Received (30 Days)
Lannis 23
MikeG 20
Newest Members
MartyH, Steve Sewell UK, BrokenLeg, Jeff Keller, Steveland
12,212 Registered Users
Who's Online Now
8 members (henryanthony, Magnetoman, Lannis, htown70, reverb, Doug P, The Momes of Wrath, steelheadchaser), 7 guests, and 21 robots.
Key: Admin, Global Mod, Mod
Forum Statistics
Forums35
Topics76,552
Posts776,412
Members12,212
Most Online204
Jul 10th, 2022
Previous Thread
Next Thread
Print Thread
Joined: Sep 2004
Posts: 1,972
Likes: 291
gunner Offline OP
Britbike forum member
OP Offline
Britbike forum member
Joined: Sep 2004
Posts: 1,972
Likes: 291
I'm in the process of refurbishing the QD brake hub on my A65 and have noticed an issue with the wheel bearing.

The QD brake hub I'm using is of unknown origin and is UN-finned with a detachable 10 bolt sprocket. The bearing that was in there was an RLS7 (7/8 inch, 2 inch, 9/16 inch). This bearing felt notchy and so I decided to change it for a new one.

When I fitted a new RLS7 shielded bearing, the same notchy feeling was present so I assume there is a problem with the bearing clearance.

The new bearing was a tight fit and needed some persuasion using a big hammer and large socket on the outer bearing housing. After fitting and noting the notchy feeling I removed the bearing and found the notchy feeling disappeared.

It seems to me that either the RLS7 bearing is wrong or I need a C3 clearance to cope with the tight fit.

I note that the BSA part no 65-5883 is often correlated with an alternative bearing LJ 7/8, so perhaps this is the right bearing to use? Alternately should I use an RLS7 with a C3 clearance?

All info welcome.

Last edited by gunner; 10/22/14 3:53 pm.

1968 A65 Firebird
1967 B44 Shooting Star
1972 Norton Commando
BSA on eBay
Joined: Jun 2002
Posts: 929
Likes: 26
Sponsor
Offline
Sponsor
Joined: Jun 2002
Posts: 929
Likes: 26
I use C3 bearings in the wheels.
RLS7.2RS or LS9 or LJ7.8ZZ I believe are all the same size (someone correct me if I'm wrong). Just get them with C3 clearance.


Peter



check out: www.bsaunitsingles.com
3000 BSA part numbers with inventory in stock just for the unit singles!
Joined: Dec 2004
Posts: 11,654
Likes: 260
Britbike forum member
Offline
Britbike forum member
Joined: Dec 2004
Posts: 11,654
Likes: 260
The BSA data leaves the clearance off, I use C3 too when using seals and had no issues. The numbers are all equivalent and pre ISO so varied by brand, metric ones are all ISO and all have the same number regardless of maker.

Joined: Sep 2004
Posts: 1,972
Likes: 291
gunner Offline OP
Britbike forum member
OP Offline
Britbike forum member
Joined: Sep 2004
Posts: 1,972
Likes: 291
Thanks guys, when I look at bearing suppliers websites, very few stock the C3 version of RLS7 or LJ7/8 and those that do charge around £20 which is over 3 times the price of the standard version.

Anyone know where I can get a reasonably priced RLS7 or LJ7/8 C3 bearing for a reasonable price?


1968 A65 Firebird
1967 B44 Shooting Star
1972 Norton Commando
Joined: Dec 2004
Posts: 11,654
Likes: 260
Britbike forum member
Offline
Britbike forum member
Joined: Dec 2004
Posts: 11,654
Likes: 260
Try looking for one with seals, to compensate for the drag of the seals they default to C3.

Joined: Sep 2004
Posts: 1,972
Likes: 291
gunner Offline OP
Britbike forum member
OP Offline
Britbike forum member
Joined: Sep 2004
Posts: 1,972
Likes: 291
Managed to buy an LJ7/8 with C3 clearance and rubber seals for £12 one on-line, see http://www.qualitybearingsonline.com/



1968 A65 Firebird
1967 B44 Shooting Star
1972 Norton Commando
Joined: Mar 2011
Posts: 270
Likes: 22
L
Britbike forum member
Offline
Britbike forum member
L
Joined: Mar 2011
Posts: 270
Likes: 22
c3 is a high temperature rated bearing.
in a high temp application you use a C3 rated bearing

using C3 in a std environment, like wheels, is not correct

succes, A

Joined: Mar 2005
Posts: 10,838
Likes: 243
J
Britbike forum member
Offline
Britbike forum member
J
Joined: Mar 2005
Posts: 10,838
Likes: 243
Quote
using C3 in a std environment, like wheels, is not correct


May I disagree...

The British use almost universally use C3 condition for wheel bearings.

The requirements for various pre-fit clearance conditions, CN, C2, C3, C4, C5, etc, are more a factor of the fit in the housing and shaft. The more the press fit in the housing and shaft the more pre-fit internal clearance required for it to get back to the correct running clearance.

Joined: Oct 2013
Posts: 76
A
Britbike forum member
Offline
Britbike forum member
A
Joined: Oct 2013
Posts: 76
I work with bearings all the time. I see no reason to use a c3. What make of bearing are you using ?
I had a similar problem on my lightning, at first I was using cheap spurious make bearings. These were found to be a very tight fit and were notchy when fitted. I found the radius on the outer corners and inner bores were too small. This meant they did not seat into the shoulders of the spindle or hub.
I then bought some ntn shielded bearings which fitted much easier, on measuring they were a few 10ths smaller on diameter and bores with bigger rads. Hey presto the spindle felt perfect and pressed up square against faces.
I have only fitted c3 bearings in high temp applications. By using c3 bearings it's giving more play, exaggerated by the diameter of the wheel.

Last edited by allthingsbrit; 10/25/14 3:01 pm.
Joined: Mar 2005
Posts: 10,838
Likes: 243
J
Britbike forum member
Offline
Britbike forum member
J
Joined: Mar 2005
Posts: 10,838
Likes: 243
From what little I have been able to learn about the History the practice rating bearings by their pre-fit internal clearance seemed rooted in British manufacturing in an era where engine weight was a major consideration. It goes back to the "one" "two", "three", "four" spot system used to grade a bearing's pre-fit internal clearance. With gasoline rationed and expensive British engineers needed to deliver a product that would give good fuel mileage, but still provide acceptable performance. Light aluminum castings took precedence over the cast iron routinely used in America.

To do this they often captured bearings in castings using nothing more than an interference fit. Often both with the inner and outer races were secured in place with nothing more than the clamping force of the interference fit in the engine. In a Vincent drive side bearing a interference fit on the high side of .0025 inches was used. In America, engineering took a different path with readily available and cheap gasoline heavy castings, often of iron, it was possible to use all sorts of clever clamping plates instead of press fits to hold the bearings in place.

Some where along the line (I believe in the 1950's, but I could be corrected) the "spot" system of grading bearings for their pre-fit internal clearance was replaced with the "C" markings with C2 being less than normal, CN being normal, C3 being more than normal, C4 being more than C3, etc. Even then this grading system didn't show up in American bearing manufacturers catalogs. So what is the difference in a wheel bearing between a CN and a C3? Typically about 0.0003 inch (.00762mm).

Why we need to understand this is the bearings clearance will close up from 70% to 90% of the interference fit the bearing has in the housing and/or on a shaft. For example if the bearing has a 0.00075 inch interference fit in a housing like our brake hub, the pre-fit internal clearance would close up at least 0.000525 inches. A typical wheel bearing with an internal i.d. in a CN condition would have a typical pre-fit internal clearance of 0.0005 to 0.0008 inch clearance (considering we are using the typical bearing house offering of an ABEC class 1 or 3 bearing.) The means if the inner race also was a light press fit the balls could end up with no clearance.

But there is another factor. To this point we are considering radial bearing clearances only subjected to a radial load. Wheel bearings are also subjected to some amount of axial loads. It is a common engineering practice to allow for a little more running clearance where the radial bearing is subjected to an axial load. It has been found to increase the life of the bearing by doing this. Our wheel axles, especially the front, are not as stiff as one would wish.

One of the problems with the "C" system which leads to confusion is the word "normal". Because what is normal for one application is not for another. What you are really interested is the bearing's installed running clearance for your application. While one can take measurements of housings and shafts to determine how much a bearing will close up, often the only way to get it right is by actually mounting the bearing and taking measurements. In our case the factory already did this for us. As I said above most British motorcycle wheel bearings are specified in a C3 condition.

From Timken Bearing Maintenance manual:
"RADIAL BALL BEARINGS
In the manufacture of ball bearings, it is standard practice to assemble rings and balls with a specified internal clearance. This characteristic is necessary to absorb the effect of press fitting the bearing rings at mounting.

Internal clearances sometimes are used to compensate for thermal expansion of bearings, shafts and housings or to provide a
contact angle in the bearing after mounting. Internal clearance can be measured either by gaging radially or axially.

Radial measurement is accepted as the more significant characteristic because it is more directly related to shaft and housing fits. It also is the method prescribed by the American Bearing Manufacturers Association (ABMA)"

Joined: Sep 2004
Posts: 1,972
Likes: 291
gunner Offline OP
Britbike forum member
OP Offline
Britbike forum member
Joined: Sep 2004
Posts: 1,972
Likes: 291
Thanks for the comments guys, today I fitted the C3 RLS7 and it now turns freely with no notchy feeling, so all has worked out OK.

I did note that the bearing was a particularly tight fit in to the QD brake hub and this may have contributed to the bearing closing up the internal clearance, hence the notchy feeling.

Previously, I tried a variety of bearings, SKF, Hoffman and some unbranded versions. All resulted in the same problem, so I dont think its a bearing issue.

I'm now wondering how tight the bearing actually needs to be in the hub? I needed to use a big socket over the outer edge of the bearing and a large hammer to make it fit. This seems a bit excessive to me and I wonder whether shaving a tiny amount of metal from the hub bearing housing would have made fitting easier and allowed use of a normal clearance bearing?



1968 A65 Firebird
1967 B44 Shooting Star
1972 Norton Commando
Joined: Oct 2013
Posts: 76
A
Britbike forum member
Offline
Britbike forum member
A
Joined: Oct 2013
Posts: 76
It should not need to be that tight, using a 3/4 lb hammer and a drift or socket, it should tap in quite easily as long as you keep it square.
Do you know only to hit the outer race when fitting into the hub ? If you hit the inner race you are likely to Brunel the ball races.
It may be someone has over tightened the spokes on your wheel and distorted the housing slightly. No problem in polishing the housing slightly. I have ntn bearings in exactly the same hub and they are standard not c3. They feel perfect. Cannot quite remember but isn't one side clamped in by a nut anyway . The nut itself is clamping the bearing on the outer race so you can polish that side without any worry of going to far.

Joined: Oct 2013
Posts: 76
A
Britbike forum member
Offline
Britbike forum member
A
Joined: Oct 2013
Posts: 76
Following taken from a bearing supplier:

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.


Joined: Mar 2005
Posts: 10,838
Likes: 243
J
Britbike forum member
Offline
Britbike forum member
J
Joined: Mar 2005
Posts: 10,838
Likes: 243
Here's a quote from a bearing MANUFACTURER:

From Timken Bearing Maintenance manual:
"RADIAL BALL BEARINGS
In the manufacture of ball bearings, it is standard practice to assemble rings and balls with a specified internal clearance. This characteristic is necessary to absorb the effect of press fitting the bearing rings at mounting."

The people who made these motorcycles weren't stupid. Far from it!!! In the World we live in we can routinely reproduce a production run of tens of thousands with the ability to adjust for tool wear, etc. over that production run and hold dimensions to less than 0.0001." That ability did not exist in the days these motorcycles were made. Your bearing supplier is reflecting a World that did not exist when these motorcycles were being made. This was especially true for a non-critical part like a wheel hub. And while they were able to hold some critical dimensions pretty close, wheel bearing housings was not one they paid that much attention to. With a variation of a .0005 inch, or more, when measuring a bunch of wheel hubs it was in reality closer to .001". Remember in those days the closer you get to a perfect dimension over a production run the more expensive the part becomes. And remember these motorcycles were made to price!!!!!!!! For many critical parts it became a process of selective fitting, or as the Germans did it a hand full of shims. American engineering approached it differently and specified tolerances and engineering designs that allowed interchangeability.

So it comes to engineering, and specifying a bearing's pre-fit internal clearance, that will give satisfactory service life in real world conditions that existed in the day. Remember the bearing will close up 70 to 90% of any interference fit it encounters during assembly. So if the bearing finds it has a .0005 inch interference fit the pre-fit internal clearance will close up between 0.00035 to 0.00045 inch. For class of bearings commonly used in these applications the bearing could actually end up with no clearance.

My suggestion to you if you want to use a CN bearing is to measure the bearing and the hub before deciding if this is a wise move. And remember the people who designed these bikes were not stupid - but a lot more knowledgeable than many engineers today as to what is required when you live in a thousandths world and not the tenths of thousands world we live in today. If you want to apply modern engineering thought you must bring your machine tolerances to suit. Good luck with that...

Joined: Oct 2013
Posts: 76
A
Britbike forum member
Offline
Britbike forum member
A
Joined: Oct 2013
Posts: 76
Well we all have different opinions. I have worked on very old and modern machine tools. Most deep groove radial ball bearings were never designed to have a huge interference fit. If it's that tight the housing or shaft is normally out of tolerance.
As far as older bearings the spot system was used to simply show the accuracy of the bearing or concentricity. They just measured them and the better quality ones were marked as higher accuracy although they were made in the same batch.
The internal clearance would be higher on a lower accuracy bearing.
I have used c3 bearings in higher temperature applications where the internal clearance disappears at high temp due to expansion. I would go with the bearing supplier notes as there will be lots of wobble on the od of the wheel. As for trying to calculate the reduced clearance by the fit into the shaft or housing it simply wouldn't be possible/financially viable to grind the components to this accuracy.

Joined: Dec 2004
Posts: 11,654
Likes: 260
Britbike forum member
Offline
Britbike forum member
Joined: Dec 2004
Posts: 11,654
Likes: 260
Quote
As far as older bearings the spot system was used to simply show the accuracy of the bearing or concentricity. They just measured them and the better quality ones were marked as higher accuracy although they were made in the same batch.


The dot system was the pre ISO std version of CN, C3 etc, it is the same meaning eg internal clearance. Due to the limitations of the machinery of the day they would have tested the clearance of the finished bearing and applied the number of dots or circles to suit or used selective assembly from measured outer/inner rings and balls to ensure they met the required mix of clearances. It does not indicate quality/accuracy just internal clearance.

Today's bearing manufacturing machinery works to much tighter tolerances, even though the bands of clearances overlap the manufacturers are achieving such accuracy the overlap is not touched.

Joined: Mar 2005
Posts: 10,838
Likes: 243
J
Britbike forum member
Offline
Britbike forum member
J
Joined: Mar 2005
Posts: 10,838
Likes: 243
Quote
I have worked on very old and modern machine tools.

I agree with this!!!
Quote
Most deep groove radial ball bearings were never designed to have a huge interference fit. If it's that tight the housing or shaft is normally out of tolerance.

I don't know how to break the news to you but nearly ALL British bikes of the day used bearings where the housing was at least .0015" interference with some as much as .004".
Quote
As far as older bearings the spot system was used to simply show the accuracy of the bearing or concentricity. They just measured them and the better quality ones were marked as higher accuracy although they were made in the same batch.
The internal clearance would be higher on a lower accuracy bearing.

I think you need to get up to speed on what the old "spots" system was used for. It was all about pre-fit internal clearance as is its off-spring the "C" noting system it morphed into.

Quote
I have used c3 bearings in higher temperature applications where the internal clearance disappears at high temp due to expansion.

Fair enough So have I, but this is not applicable to the discussion.

Quote
I would go with the bearing supplier notes as there will be lots of wobble on the od of the wheel.

There is NO detectable movement at the rim when C3 bearings are fitted to a British hub! Nearly every wheel bearing I have replaced in a British wheel has been in a C3 condition. I have been doing this as a profession since 1959 and have seen an awful lot of wheel bearings.

Quote
As for trying to calculate the reduced clearance by the fit into the shaft or housing it simply wouldn't be possible/financially viable to grind the components to this accuracy.

This is done every day in modern production. While in the day it would have had to be done with a selective fit. That I agree would be costly as I mentioned before.

Last edited by John Healy; 10/28/14 3:01 pm.
Joined: Oct 2013
Posts: 76
A
Britbike forum member
Offline
Britbike forum member
A
Joined: Oct 2013
Posts: 76
I don't think 0.004 is a huge interference fit, it's dependent on the diameter of the bearing.
Also many bearings in aluminium cases were done so to allow for the expansion.
Many gearbox/ engine bearings are a interference fit but they are not c3!
You must agree that with the spot system the smaller the clearance the greater the accuracy.
What we need is someone with an original hub and bearings to tell us what is in there. Hasn't someone already said bsa don't specify it.

Joined: Dec 2004
Posts: 11,654
Likes: 260
Britbike forum member
Offline
Britbike forum member
Joined: Dec 2004
Posts: 11,654
Likes: 260
Quote
You must agree that with the spot system the smaller the clearance the greater the accuracy.


You are confusing Accuracy Classes with Clearances.

Joined: Mar 2005
Posts: 10,838
Likes: 243
J
Britbike forum member
Offline
Britbike forum member
J
Joined: Mar 2005
Posts: 10,838
Likes: 243
Quote
I don't think 0.004 is a huge interference fit, it's dependent on the diameter of the bearing.

It sure is especially when calculating the amount of crush to figure into specifying pre-fit internal clearance. The inner race could collapse as much as .003".

Quote
Also many bearings in aluminum cases were done so to allow for the expansion.

Yes, it was the engineering popular in England when these bikes were being made. It was done because of the lack of materials (they had exported a lot of it to the continent a few years earlier) and the need to produce a vehicle that would give you high fuel mileage. But it had its problems!!

Quote
Many gearbox/ engine bearings are a interference fit but they are not c3!

Boy, a lot of the ball bearings used in engine and gearbox bearings are C3.

Quote
You must agree that with the spot system the smaller the clearance the greater the accuracy.

No I don't agree!! I have collected many old bearing books over the years and I would like to refer to the SKF bearing reference book dated 1959. Here is one of the first references I have found where they start referencing the "C" rating for bearing pre-fit internal clearance.

They also recognized the adoption of the ISO R15 standard by the British in 1958, but with inch bearings there is no mention of accuracy! At this time in America bearing catalogs were make reference to the ABEC class 1,3,5,7 and 9 groups describing the precision of bearings. ABEC 1 would not be a precision bearing while ABEC 3 to 9 would be. With ABEC 3 being he most commonly specified for our kind of applications. But one must remember this system is for the physical outward dimensions: bore, o.d. thickness and does not refer to all of critical factors such as smoothness of the rolling tracks, precision of the balls, etc.. There is no such system described in the 1959 SKF catalog.

Quote
What we need is someone with an original hub and bearings to tell us what is in there. Hasn't someone already said bsa don't specify it.


None of the manufacturers specify by their part number what the specification is. I just happens that I have a list prepared by Triumph's export parts manager, Jack Shortland, for all of the bearings used in Triumphs and their specifications. I have published this in Vintage Bike.

This didn't start as a discussion about what was specified by BSA or what was normal. It started because it was assumed that the bearing was CN, but for what should be obvious reasons to anyone who has worked on these bikes for any time, that when it was offered it didn't turn like you would want your wheel bearing to do. A C3 bearing was offered and the bearing turned freely. Remember the machinery these bikes were made on had just spent most of their life, and it was a long life for most, winning a war (and some of the kit had a hand in two big shows). This was especially true for BSA, although Triumph's lot of machine tools were pretty worn by the time they made these motorcycles.


Moderated by  Allan G, Jon W. Whitley 

Link Copied to Clipboard
British Cycle SupplyMorries PlaceKlempf British PartsBSA Unit SinglesPodtronicVintage MagazineBritBike SponsorBritish Tools & FastenersBritBike Sponsor






© 1996-2022 britbike.com
Powered by UBB.threads™ PHP Forum Software 7.7.5