Guys I am assembling the rear hub of my project during the 3 odd years this has been apart the Bearing thrust washers (15-7047) appear to have disappeared the OD & ID of these are simple enough to determine but not the thickness can any one confirm the thickness of this so I can manufacture a couple.

Cheers
Ron FTLDU

email (option): Grumpy.moran@gmail.com

From what parts list do you have that number? I can only find 15-7045 for what I think you need. Are you looking for the size of the two washers that sit behind the bearings in the hub? If so I can take measurements for you.

Henk

email (option): ahum@quicknet.nl

Henk
Yes it is those two spacers if you could get me the dimensions I would be best pleased. The part number 15-7047 came from the dragonfly listing my parts list does not have this part Identified.

Cheers.

Ron

email (option): Grumpy.moran@gmail.com

15-7047, Hub bearing sleeve thrust washer/collar/spacer/inner ring for seal (1) 38-49,(0.790” x 1.181” x 0.144” thick, fits on 15-7046 against shoulder before bearing cone, hardened steel).
15-7045, Bearing thrust plate/spacer (2) 38-49, (I.470” x 1.846” x 0.155"-0.160”, fits inside bare hub before bearing outer cups, mild steel).
NOTE:
The 0.155"-0.160" thickness of 15-7045 is only applicable if using original 26-6890 bearings, (20mm x 47mm x 14mm)which have an effective assembled height of approximately 0.556"-561", (my measurements of several examples, but 14mm = 0.551181102”)
Modern replacement taper roller bearing (complete) is sold under 30204, listed as 20mm x 47mm x 15.25mm, 30204 has an effective assembled height of 0.604", (my measurement of 2 examples, but 15.25mm = 0.6003937" and these were NTN bearings, not obscure suspect origin rubbish).
Individual cups and cones from 30204 must not be interchanged with original bearings.

When rear hub is correctly assembled with all original parts, the abutment face of 15-7046(Hub bearing sleeve/Hollow axle)is approximately 0.426" above hub face for sprocket/brake drum,(my measurement of 1 example).

When rear hub is incorrectly assembled with 30204 bearing and 0.155" thick 15-7045, the abutment face of 15-7046(Hub bearing sleeve/Hollow axle)is 0.576" above hub face for sprocket/brake drum,(my measurement of 1 example).
A few thou variation is of no great consequence, but both sides add up to approx 0.100" overall increase in width of 15-7046 Hub bearing sleeve/Hollow axle and 26-6861 Hub bearing locknut (outer nut)

Bearing cup spacers for 30204 bearings should be approximately 0.105"-0.110" thick.

HOWEVER, modern 6204 ballraces (20mm x 47mm x 14mm) can also be substituted in rear hub with no modifications, 6204 are available “open”, "shielded" or “sealed”. Virtually every modern motorcycle uses sealed ballraces for wheel bearings, those with sidecars on M series BSAs would be wise to check regularly. Due to interference fits, use sealed C3 high clearance 6204 2NSEC3 bearings, do not over tighten 15-7049 adjusting nut.

There are several errors in Draganfly illustrations.

First, do no harm.

email (option): n.gentner@bigpond.com

Quote:
"When rear hub is correctly assembled with all original parts, the abutment face of 15-7046(Hub bearing sleeve/Hollow axle)is approximately 0.426" above hub face for sprocket/brake drum,(my measurement of 1 example)."

I dug out another original intact rear wheel, 15-7046 is 0.438" above hub.

First, do no harm.

email (option): n.gentner@bigpond.com

Neale
Thanks for the info the conversion to ball bearings actually highlight the absence of these thrust washers although my preferred option would be 7204 2 RS bearings IE angular contact bearings which means you do not need to fit a spacer but I am having some difficulty sourcing the bearings in Adelaide

Cheers

Ron

email (option): Grumpy.moran@gmail.com

Hi Ron,

The washers I have are exactly 4 mm.

Henk

email (option): ahum@quicknet.nl

4mm = 0.157480315"
Pretty close to mid range between 0.155" - 0.160”.

When fitting ballraces to rear hub you do not need any additional spacers, simply refit the BSA cup spacers, then the 6204 bearings, then the BSA hollow axle and adjusting nuts

While angular contact bearings may in theory be "better", they are vastly more expensive and don't come sealed, I don't regard them as either an improvement, cost effective, or a step towards simplification of the rear hub.

email (option): n.gentner@bigpond.com

Neale
7204 bearings are available sealed just not in OZ I have located a supplier in the US of price ? I was quoted AuD 19.50 for 6204 2RS C3 bearings from my local supplier. Butt for 7204 2RS C3 USD 27.00 delivered to me from the US which equates to AUD 25.62 so it's worth it for the advantages or I think so

Cheers

Ron

email (option): Grumpy.moran@gmail.com

6204s are the same bearings I have just removed from the small conical front hub fitted to a B50MX..One of the last bikes BSA produced. Interestingly, for that particular application they are a C4 fit, not C3. That indicates a tighter fit into the hub and/or onto the wheel spindle..7204s provide a theoretical advantage over 6204s regarding their ability to bear axial loads...Whether that will make any difference in practical terms regarding the apparent performance or durability of the bearings remains to be seen..When I worked on the design side in Engineering I was always advised against developing a tendency to over specify components or tolerances without good reason..In other words is there a problem with the existing specification?..Ian

email (option): ian@wright52.plus.com

Henk
thank you and all other Forum members for supplying this information the help we receive from all members of this forum is breathtaking whilst those who start with a complete motorcycle assembly is somewhat easier for someone like myself who start with an incomplete motorcycle and various pieces in a series of Cardboard boxes it is the only thing that keeps you going especially when you are struggling with three motorcycle restorations each with their own idiosyncrasies and range in age from 1941 to 1984 but we will struggle on

Cheers

Ron FTLDU

email (option): Grumpy.moran@gmail.com

Hi Ian,
No there is nothing wrong with the original BSA specification, but some M20 owners have trouble locating original bearings and don't have access to machine shops to make special spacers to make the modern replacement bearings work properly.
Hence my suggestion of 6204 conversion which requires no modification to BSA parts.

I only just recently used my last set of NOS rear bearings and was also involved with helping Ron Pier with rim offset data, when the additional width of replacement taper rollers came to light, thus all the relevant information was at hand for answering Ron Moran's enquiry.

I agree C4 could also be used in M20, they were probably used to ensure no drag on B50MX. Bearings which are fitted so their rolling elements are slightly loose are always much preferred to slightly tight. I was recently involved with restoration of hubs from a mid 1980's Honda RS125 road racer. Surprisingly the original bearings were way too tight (and ruined)and the HRC factory parts book specified std clearance bearings, I was shocked.
We fitted C3s and it was much improved and ok, but I personally would have gone to C4, or eased the interference fit to reduce crush.

email (option): n.gentner@bigpond.com

Hi Neale..I think you may have misinterpreted my meaning regarding spec. changes. I was suggesting that going beyond 6204 bearings to 7204 spec. may not have any perceptible advantage....not suggesting that the bearings should not be changed from the standard type..I wasn't really proposing a change to C4 grade either..that was just an interesting point I noticed when stripping out the original bearings from the B50 hub..It's the first time I have seen C4s in a wheel.....Ian

email (option): ian@wright52.plus.com

Good Oh Ian no probs.

email (option): n.gentner@bigpond.com

Ian
I do not want to clog the forum with continuing discussion around this Issue But While I have chased down 7204 2 RS bearings At a reasonable price now that I have resolved the fitting of hub thrust washers by manufacturing 2 i have Decided to go with 6204 2 RS C3 Bearings principally because I was going through some bits for the FJ 1100 I am tastefully modernising and found a pair of front wheel bearings I purchased for the original wheel now redundant as I am using a later wheel these were 6204 of the right type but unlike Neale I believe a spacer needs to be fitted between the bearings to prevent excess axial load on the Bearings leading to premature failure. This type of spacer is used in all modern wheels (read japanese) with deep groove ball bearings that I have dealt with including the 2003 Yamaha wheels I am using in the FJ. But in ,making this sweeping statement I have little or no experience with late model British motorcycles

Cheers

Ron

email (option): Grumpy.moran@gmail.com

Hi Ron..In the original set up the bearing adjustment nut and locknut allow setting of the 'end float' of the taper roller bearings which, once set, have no end thrust on them. I guess if the adjustment nuts are retained they will perform the same task of preventing an end load on the ball bearings (in conjunction with the bearing sleeve)...I haven't looked at it in detail and am only recalling the set up from memory but I would imagine Neale has thought this one through..Perhaps he will clarify his reasoning when he sees this posting...Ian

email (option): ian@wright52.plus.com

I have no problem with anyone properly fitting an additional spacer between the inner races.
If anyone wishes to, they could also do this with the BSA taper rollers.

However, the additional spacer will have to be to a very precise length and with the known variations in BSA hub parts, undoubtedly different lengths for every rear hub.

The modern wheel set up does indeed have a spacer between inner races, but the design is entirely different i.e. when properly assembled, the push through axle crushes the 2 bearings against the spacer, without the spacer both bearings would be rapidly destroyed.

The design of the BSA hollow axle and locknuts allows for dimensional variations and if properly adjusted, the only difference in axial load capacity is the actual difference between a taper roller and a ballrace.

In my opinion, with the exception of sidecar machines, the perceived axial loads applied to motorcycle wheel bearings are greatly over rated.

Personally I would rather spend the spacer making time riding my bike, or cuddling my wife.
Which is omething I'm going to do right now, you guess which.

email (option): n.gentner@bigpond.com