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rim locks, let the discussion begin

Prosper Keating

Well Known and Active Website User
Non-VOC Member
Do you mean security bolts? These were fitted in the days when tyres were made of softer materials and were prone to moving on rims under fierce acceleration, taking the inner tubes with them and risking ripping out the valves, which is not good at any speed.

As well as rip-snorting roadsters, they were fitted to off-road motorbikes - scramblers, trial bikes etc - as riders tended to run with quite low pressures for extra grip in mud, clay and sand and the covers and inner tubes would move about on the rims. I had them on my 1950 TR5 when I briefly rode about on the standard knobblies but did not bother replacing them when I fitted old-style but modern road tyres as they are less prone to slipping on the rim.

However, I would replace them were I to campaign or green-lane the Trophy on semi-inflated knobblies. Vincent-HRDs had them because of their high power - for the period - but you would be alright if you left them off when using classic-style tyres made today because they are an awful pain in the arse to fit and, more to the point, to deal with when repairing a puncture at the roadside, as modern tyres are tougher to get on and off rims without a large rubber mallet and pinching a tube because of security bolts when you are tired and grumpy is all too easy.

In the old days, you could 'walk' tyres onto and off rims if wearing stout boots. In fact, I have managed it with modern tyres but it's a sweaty business. Regarding the positioning of security bolts, I'll be down in my garage later and will check the holes in some original Dunlop rims fitted to Vincent-HRDs for you but 'even distribution' of the three security bolts, in relation to the valve, is the starting point. I believe, AFAIR, that they had weights of different sizes for the bolts, to facilitate wheel-balancing.



Link: http://www.motos-anglaises.com/vincent/historique/1938-fin.htm)

This scan, illustrating former French Section President Dominique Malcor's article about the marque, is very low resolution but this side-on factory shot of prototypical Black Shadow JRO 102 normally gives a fairly clear view of the position of some of the safety bolts fitted to the rear wheel, just visible at around 7-o-clock and 10-o-clock. The third is obscured by the chainguard. I don't remember them being in place when we road-tested JRO 102 for one of the magazines.

Hope this makes sense...

PK
 
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vin998

Well Known and Active Website User
VOC Member
VOC Forum Moderator
I have a security bolt in the rear wheel, mainly because the wheel rim is a stainless one and even though the rim had serrations where the tyre mounted, they appeared to be quite smooth and was conerned with tire creep under acceleration. I didn't bother with the front.

Position of the security bolt in relation to the tube's valve is shown in Know thy beast. (sorry I don't have my copy with me).
Note : when a security bolt is used, two extra bolts are also used to mount lead weights so as to balance out the security bolt. this is also in Know thy beast.
 
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The VOC Spares Company Limited

Well Known and Active Website User
VOC Member
I have a security bolt in the rear wheel, mainly because the wheel rim is a stainless one and even though the rim had serrations where the tyre mounted, they appeared to be quite smooth and was conerned with tire creep under acceleration. I didn't bother with the front.

Position of the security bolt in relation to the tube's valve is shown in Know thy beast. (sorry I don't have my copy with me).
Note : when a security bolt is used, two extra bolts are also used to mount lead weights so as to balance out the security bolt. this is also in Know thy beast.

I had a sudden deflation on the rear of my B a couple of years ago, unknown to me the thread on the security bolt had stripped and the tyre crept ripping the tube at the valve. 19” chrome steel rim with Avon SM tyre.

From KTB the security bolt is 4 spokes anti-clockwise from the valve hole looking at the wheel from the left side of the bike, this should be a wide area between the spokes. The first balance bolt is 12 spokes on from security bolt and the second 12 from the first.
 

piggywig

Well Known and Active Website User
Non-VOC Member
security bolts

The annoyance of fitting the security bolt is preferable to the annoyance of losing the valve! Having suffered a ripped tyre on gravel desert roads hundreds of miles from a tyre shop, resulting in numerous punctures at regular intervals throughout the day, finally a quick fix (without the pesky bolt) produced an instant removal of the valve! I am now a true believer in the worth of these bolts. Modern tyres may reduce the chance of it happening, but a security bolt, especially with slippery chrome rims, will reduce the chances to nil. As always, the rider can choose between hoping it's o.k. and knowing it is.
Col.
 

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