Rear Shock Mount Question

PhiloMcGiffin · May 21, 2010

I'm fitting new shocks to my '74 850 Commando... I measured the ID of my upper shock mount... I got 0.75 inches... I was told by "someone very knowledgeable about British Bikes" that all standard Norton top shock mounts were 7/8" not 3/4". What say you my knowledgeable friends? 3/4 or 7/8?

Thanks for the help.

grandpaul · May 21, 2010

If you stored your bike in a cold shed all winter, maybe they shrank?

PhiloMcGiffin · May 21, 2010

You know mine was frozen in the icy ground... that's probably what happened? Why don't I think of these things :roll:

Diablouph · May 21, 2010

I assume that you mean inside dimension, not inside diameter. I measured my 73 850 and got ¾” exact. But, then my garage is warm.

The bolt that holds the shock and attaches the seat is 3/8"

L.A.B. · May 21, 2010

PhiloMcGiffin said:
I'm fitting new shocks to my '74 850 Commando... I measured the ID of my upper shock mount... I got 0.75 inches... I was told by "someone very knowledgeable about British Bikes" that all standard Norton top shock mounts were 7/8" not 3/4". What say you my knowledgeable friends? 3/4 or 7/8?

If by "OD" you meant overall dimension and not outside diameter, then they need to be of sufficient width to fit snugly between each top monting), but it's not just the top mounts. http://britmoto.com/manuals/Manuals/850_man.pdf -pdf page 97.

If shocks with narrower width sleeves are used then they will probably require additional spacers.

grandpaul · May 21, 2010

ID = INSIDE diameter.

L.A.B. · May 22, 2010

grandpaul said:
ID = INSIDE diameter.

Yes ID not OD, (my typo) presumably it was still overall length which was meant.

PhiloMcGiffin · May 22, 2010

I'm trying to confirm that the inside dimension is 3/4" so that I can order the correct top shock eye spacer. I've measured mine; it is 3/4... I'm trying to confirm if that is standard or if mine is odd... the bike is now in the shop; so temperature should no longer be a factor

Thanks for your help.

Diablouph · May 22, 2010

As stated above, I have measured my 73, 850 at exactly 3/4" between the mounting plates. That is an INSIDE MEASUREMENT.

That temperature crack was GrandPaul's way of being a........... well, you know, he's a Texan.

Scooter62 · May 23, 2010

After checking my MK III frame I measured slightly less than 3/4" with some variation from side to side. In discussing this with Norman of NJB Shocks there is apparently a fair amount of variation on this dimension from frame to frame. I would assume though that 3/4" is normal.

Scooter

L.A.B. · May 23, 2010

PhiloMcGiffin said:
I'm trying to confirm that the inside dimension is 3/4" so that I can order the correct top shock eye spacer. I've measured mine; it is 3/4... I'm trying to confirm if that is standard or if mine is odd... the bike is now in the shop; so temperature should no longer be a factor

Sorry for the delay in answering this (as I've been away from home for a few days). The distance between the mounting plates on my 850 MkIII and therefore the shock mounting sleeve length, is 3/4".

One possible reason there are certain variations in the dimension between mountings could be that shocks with narrower spacers had most likely been fitted to that particular frame sometime in the past, which could have resulted in the mounting plates being bent inwards as the mounting bolts were tightened? So I would suggest checking the measurement near where the plates are welded to the frame tube, and not in the area near the shock mounting bolt holes.

Rear Shock Mount Question

PhiloMcGiffin

grandpaul

PhiloMcGiffin

Diablouph

L.A.B.

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grandpaul

L.A.B.

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PhiloMcGiffin

Diablouph

Scooter62

L.A.B.

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