Handlebar Clamp Bolt Old Bike

[dewi1]

I have an old maybe 1960s "The Evans" racer, 4 speed deraillaur if that helps to age it ..... anyway I can't get on with drops any more so I am converting it to straight bars. I have a problem with tightenting the bolt that holds the bars in the stem ... I have fudged it with a 12 mm spanner but it isn't tight enough and the bars have come loose. I thought I'd try to buy an imperial but it seems that 7/16 is a 11.1 mm and 15/32 is a 11.9 mm so I am not convinced either of these are right ... does anybody know what size spanner I need to save me from having to try "trial and error"?

Also I had trouble with these bars before (alloy ones) spinning a bit on a previous bike, should I be putting anything between them and the stem?

Many thanks
Taffy

[robgul]

Obvious immediate thought, as previous problem too, is that the bar tube is smaller than the stem was designed for and it's not pinching the bar tight enough.

Two options : get another quill stem (if you are changing from drops to straight bars you would probably appreciate a shorter reach stem for comfort?) - or wrap a thin shim around the bar to make it thicker in the stem (Coke can is the ideal material for the shim .... use Diet Coke, it's lighter )

Rob

[Brucey]

coke can shim is what you need.

Also; the spanner you need for this is probably a whitworth/BSF size.

If I remember which one I'll post the size.

cheers

[dewi1]

many thanks Brucey, yes help with spanner sizing would be good cheers

Will go and buy some coke .... I need to bodge it to get home from work!

[Brucey]

I think the size you need will be labelled 1/4"BSF/ 3/16" Whit. It should measure about 11.45mm AF.

Most likely it is attached to a fine threaded bolt that is non-standard too, probably a 5/16" thread with a fine pitch. These bolts can develop very great forces because of the fine pitch, and shouldn't need to be super-tight if clamped on a bar of the correct size.

At risk of sounding like a grumpy old man my belief is that there was a wider range of suitable (and available) fasteners that were prefectly matched to their intended application when BSF/Whitworth and UNF were the thread standards in use.

Now we end up with M7 bolts in places on bikes (which are the exact right bolt for the job BTW) but you can't actually buy new M7 bolts at all easily....

hth

cheers

[dewi1]

Thanks to all for help and advice. I think it was the lack of a shim that caused the issue, with the use of an adjustable I have managed to refit with a shim from a tin of tango and (touch wood) seems fine!

[Ugly]

British Standard Cycle Thread Chart

www.motalia.com/Html/Charts/cycle_chart.html

More information than you will ever need