Dunlop MC286 Rim (2011)

Anybody have information on MC286 Dunlop rims and where or what that number is from? I have a rim here that came off a late 1974 MkII that is equipped with the drum brake as would be expected. It is most definitely a WM2 - 19 rim but does not bear that stamp. Only the MC286 on one side and the usual Dunlop made in England on the other.
Thanks
Russ

rvich said:

Anybody have information on MC286 Dunlop rims and where or what that number is from? I have a rim here that came off a late 1974 MkII that is equipped with the drum brake as would be expected. It is most definitely a WM2 - 19 rim but does not bear that stamp. Only the MC286 on one side and the usual Dunlop made in England on the other.

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Dunlop MC286 is probably an original late 850 MkII rim although it's odd that it doesn't have the WM2-19 stamp.

A few other Dunlop rim "MB" & "MC" code numbers:

MB41 Commando drum rim front & rear

MC275 Commando disc, front, 1972-1975

MC284 Triumph disc, front
MC285 T160 Trident rear
MC286 Some 850 MkII/A Commando rear
MC287 Early 850 MkIII Commando rear
MC288 Late 850 MkIII Commando front
MC289 Late 850 MkIII Commando rear
MC296 '78 Triumph T140 rear.

Can anybody add any other MB/MC numbers to the list?

Can't add, but can verify the MB41 on a '69S production date.



Dave
69S

I would have thought that they would have stayed with the MB41 deignation for as long as they kept the rear drum. But this just goes to show you what I know!

'70 Roadster is MB41, or at least mine is.

rvich said:

I would have thought that they would have stayed with the MB41 deignation for as long as they kept the rear drum. But this just goes to show you what I know!

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Can you say what diameter are the spokes are, and are they straight wire or "butted" (two diameters)?
Also what diameter are the nipple holes in your MC286 rim?
Could someone also please supply the MB41 rim nipple hole size for comparison?


I cross-checked the rear wheel part numbers in the 850 Mk2/2A supplement with earlier rear wheel assemblies and there are a number of changes in the 2/2A supplement which include rim, spokes, nipples, hub, brake drum, axle, etc.

Cross-checking that information with the workshop manual specifications and by doing a bit of detective work, it appears the rear wheel spokes may have been changed from the previous butted 8/10 SWG to 9 SWG (or 8/9 SWG?) for the 850 Mk2 & 2A models.

The increase in spoke gauge may have required the rim change to one with larger holes for the 9 SWG (063207) instead of 10 SWG nipple size, however that is a guess-as an increase in spoke diameter does not always require a larger nipple diameter and the part number change could have been for a completely different reason (the rear rim is listed as 065730 in the 2/2A supplement)?

Unfortunately, using the Andover Norton part search, the majority of those different 850 2/2A part numbers come up as: "Part not found" and the AN rear wheel parts listed for 1974 appear to be the same as the earlier year models except for the spokes which seem to be listed under different part numbers to both rear wheel types.

I'll place my money on the nipple holes. The parts books seem to show a confusing mixture of 3/8 or 1/4 inch spoke nipples for the front and rear drum brake wheels.

I don't have the spokes, just the rims. I have an MC286 and an MC275 here and both have .310 holes for nipples. I don't have access to an MB41 until after I get home from this trip.

Russ

My MB41 holes measure 0.267".

Dave
69S

Mystery solved, then.

LOL! Solved? OK, I am a little slow.

I now realize that the information in the Walridge catalogue about spoke gauges is pretanent to my situation after all. I am glad I found out about this before just ordering up a set of "Commando" spokes from somebody else. It makes me wonder how many bikes are out there running around with undersized nipples in the rims.

Anyway, thanks for the help and slap up side the head. Looks like I will be building some wheels this winter after all!

Russ

PS-does it mean that hubs are drilled for either 9 or 10 gauge spokes as well? The difference is 0.14 vs 0.12 inches.

rvich said:

PS-does it mean that hubs are drilled for either 9 or 10 gauge spokes as well? The difference is 0.14 vs 0.12 inches.

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The Mk2/2A rear hub part number given in the supplement is also different, so there is the possibility that part number change was because of a change in spoke gauge from butted 8/10 SWG to 9 SWG but I suggest you measure the hub spoke holes because I'm only guessing?

8 SWG = 0.160"
9 SWG = 0.144"

http://home.clara.net/brianp/wire.html

Coming in a little late on this,
but it is recorded that the spokes were changed to a heavier type somewhere (early ?) in the life of the 850.
It was found that the extra torque was breaking spokes in the back wheel, so they changed to a heavier version of spoke.
This also involved bigger nipples and punched holes, so the part numbers all changed to reflect this.

The back rim for an early 850 Mk1 was still MB41.

But changing spoke gauge does not always mean a change of nipple OD, Triumph used 10/8 gauge butted spokes with nipples threaded 10 gauge but with a 0.300" OD on the rear wheel in the 60's, BSA used 10 gauge spokes going into 0.275" nipples on the crinkle rear for B25 and A65 with an option for off road of 9 gauge with 0.275". If you go to a wheelbuilding parts emporium that allows you to buy nipples with various OD's fitting 10/9 and 8 single and butted spokes. Useful for old alloy rims where the holes have gone oval, drill out to next nipple size and fit the larger nipples.

kommando said:

But changing spoke gauge does not always mean a change of nipple OD,

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True.

But I seem to recall some of the 850 problems was nipples pulling through the rim. (?)
So going with larger nipples and stronger spokes probably seemed like a good fix ....

kommando said:

But changing spoke gauge does not always mean a change of nipple OD,

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However, in this instance, I believe it might.

According to the parts books, the Commando front and rear drum wheel nipples are part 021693 (40).
Front disc wheel nipples are 062595 (20), and 063207 (20).
The 850 2/2A supplement lists the rear wheel nipples as 063207 (40)

According to certain online Norton parts sources those nipple sizes are:

021693, Drum wheel (40) 10G x 0.250"
063207, Disc front (20), Mk2/2A and Mk3 rear (40) = 9G x 0.300".
062595, Disc front, disc side (20) = 8G x 0.300".

(Standard Wire Gauge)
10G = 0.128"
9G = 0.144"
8G = 0.160"

L.A.B. said:

snipped

A few other Dunlop rim "MB" & "MC" code numbers:

snipped
MC287 Early 850 MkIII Commando rear
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MC289 Late 850 MkIII Commando rear
snipped

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Les, Can you provide any more info regarding the early and late Mk III rear rims? Change in spoke gauge or lacing? When did the change occur?

chaztuna said:

Les, Can you provide any more info regarding the early and late Mk III rear rims? Change in spoke gauge or lacing? When did the change occur?

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Unfortunately, I can't.
There was no change of spoke gauge (9 SWG) or lacing pattern as far as I'm aware. Both rims have the 3 x 1 dimple pattern and there's no serial number for the change that I know of.