Z1A Security bolt(s)

[MrDavo]

I have a security bolt / clamp for my Z1A back wheel, and a new rim is fitted to the rear hub, with no extra holes drilled yet.

I note from the parts book that they list TWO of these. A bit overkill like the 630 endless chain I guess Kawasaki were erring on the safe side of liability - Although I've had quite a few big bikes I never saw two fitted before.

Do you guys usually fit two, given that this is how it was designed? When I drill the holes do I space them 120 degrees apart from the valve hole?

[warren3200gt]

I think your asking about rim locks to stop the tyre slipping on the rim with the chance of ripping the valve out the tube? Both 650's and 900's have 2 rim lock holes plus one for the valve, so 3 in total, equally spaced at 120 deg apart.
Overkill I would say.

[Philippe]

Hi MrDavo

if you make two holes for the tyre grippers they should be 180 ° opposite to one another.
The exact location compared to the valve hole is between the fourth and fifth nipple hole counting from the valve hole counterclockwise. The other tyre gripper hole must be located at 180° opposite to that one.
I hope you bought the correct rim...
I'm not sure if you still need to mount these tyre grippers because the quality of the modern tyre compound is different to the one they used almost 50 years ago.
I'm sure others will be able to inform you correctly about it.
GrtZ
Philippe

[warren3200gt]

The other tyre gripper hole must be located at 180° opposite to that one.

Hi Philippe, why do you say must? Of the 4 bikes I have with original rims the grips are 120 deg apart and the other bike I have with after market cma race mags the grips are 120 deg apart.

[Philippe]

Hi Warren

I had a look at an original Takasago rim and that's the location I found. I think it's obvious that the two masses of the tyre grippers should be located 180° opposite to one another in order to avoid too much unbalance in the wheel...
It makes sense to me...doesn't it?
GrtZ
Philippe

[warren3200gt]

It does make sense Philippe, however the takagaso rims on my bikes have them 120 deg apart with added balancing weights.

[000zeds]

I agree with Phillipe about the need to mount these tyre grippers because the quality of the modern tyre compound is different to the one they used almost 50 years ago as I had rims with no tyre grippers and had no problems at all.

[ADRIAN H]

If your rim hasn’t got holes for the rim grips I would not drill them. As modern tyres are light years ahead, and are no longer needed.

[MrDavo]

Blimey this has set the cat amongst the pigeons! Thanks for all the response.

Back in the day even my Triumph T140V came with a security bolt in the back wheel. I raced a Triton with a 750cc Weslake engine for a season and fitted one to that, but that engine had so much torque you could have used the bike to pull out tree stumps. Unfortunately it spent most of its energy on trying to break the chassis instead, always in new and interesting ways.

I hadn’t realised that modern compounds (I’m using Bridgestone BT45s) made a difference to how well the tyre bead gripped the rim.

[warren3200gt]

No issue really, I wouldn't bother adding them on new rims. Modern tires are a whole world away from what we used back in the day.
What is interesting though is that out of curiosity I have double checked my bikes and stock of old rear rims and I have both types of positioning.
Attached, pics of 650's with 120deg spacings both stock and afterarket. It kinda makes sense on the after market because, 3 spokes, 3 holes equidistant between the spokes.
What Philippe says makes sense re balancing but it's not what I found on my 650 stock rim but it is what I found on a 650 spare rim. Usual 70's manufacturing I guess.

20210106_112121.jpg (473.98 KiB) Viewed 2092 times

[harri183]

Daft question but has the wrong holes been used as in the valve is where the tyre lock stop should be?

[warren3200gt]

No two holes are opposite each other, so it's not possible.

[000zeds]

Daft question but has the wrong holes been used as in the valve is where the tyre lock stop should be?

I thought the same myself

[zapo]

Warren, in your photo of the spoked wheel.....where is the inner tube valve stem?

[tlc]

My two penn’orth.
The CMA or whatever it is has to have 120 degree spacing as it’s a 3 spoke.
As I remember my old thou’ had the retainers 180 apart and the tyre valve was not too far from one of the retainers.
They were a right pain in the arse when changing tyres though and as many have said now we put 30 plus psi in the tyre they’re less likely to spin.
Gotta say, mine never spun.