The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Frame => Topic started by: MikeN on 22.03. 2009 20:18
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If you have read the problems that I was experiencing with my Pearson 2LS front brake and you ever have a similar thing happen to your bike.Heres a bit of advice.
Sort it out quickly.
Having sorted the brake, a fault has now occured with my front forks. I found that my forks wouldnt rebound when they bottomed out over a bump or hard braking. I have just pulled my forks down and discovered that the violent brake locking That I was experiencing has bent my right hand fork leg!
It can only be this because I havent hit anything.
Oh well ,my nice hard chrome fork tube will be under the fly-press tomorrow.
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Can it really be straightened enough using a press?
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Yes, the forces have to end up somewhere, that is to the forks\frame, which can get pushed past the limit. A friend got disc brakes conversion done to his 57' 2000kg american car, brakes were immensely improved, yes, to the point of on first heavy brake test the bolts securing the front calipers where cut right off ! strangely enough no accident or serious damage. New improved bolts fitted, but I suggested that next time with similar brake power applied it could be the frame\front suspension\steering parts and more beeing cut off, recommending him to be -very- carefull.
These vintage things are simply not constructed to withstand the immense force a very good brake system will inflict upon parts, needs including some strengthening on many areas of the frame\suspension etc., Mike, you seem to have discovered all this, good luck with the repairs.
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Wll I managed to straighten the fork tube quite easily .It wasnt far out.Clocked it between centres on the lathe and used alloy vee blocks with a brass anvil on the press to protect it .
Now Ive discovered that its also bent the slider as the lower fork bush goes tight half way down and you can see the distortion when you put a straight edge alongside.Never heard of that happening on a bike before.
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2 hours later and Ive turned a close fitting alloy mandrel to force down the slider to assist straightening .A bit of work with the press and some soft pads. A bit more work with a solid lap and then a hone and the fork leg is re-assembled and ready to fit tonight.
I Thought I may have had to manufacture some oversize fork bushes but I think Ive got away with it .
Good job my boss is off work today.
MN
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Sounds like you're a handy person to know.
Cheers,
Iain