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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Rear suspension springs
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<blockquote data-quote="timetraveller" data-source="post: 147907" data-attributes="member: 456"><p>It's all a bit more complicated than you would wish. The standard Vincent rear springs, which I guess is what the part numbers refer to, are not suitable for shortening and if you used Comet springs on a twin you would almost certainly bottom out frequently. For years people have fitted longer springs, originally developed by Ken Pettiford. These are known as 'Pettiford springs'. You can very quickly tell by just looking as to which springs you have. If about one and a half inches of inner protrude out at the bottom of each spring box you probably have standard springs. If you have two and a half inches of spring then probably the Pettiford. This is with the bike on its wheels, not on a centre stand. If you have the longer springs then you can change them for the shorter original springs. Some adjustment can be obtained by slackening the lock nuts on the top and bottom eyebolts and screwing the eyebolts in as far as they will go. If that doesn't do it then the next thing is to reduce the thickness of the front part of the rubber pad within the seat. You might be able to gain and inch there but you will need some skill to make the seat look reasonable again.</p><p></p><p>Let us have details of the length of the spring boxes and possibly a photo and we might be able to help more.</p></blockquote><p></p>
[QUOTE="timetraveller, post: 147907, member: 456"] It's all a bit more complicated than you would wish. The standard Vincent rear springs, which I guess is what the part numbers refer to, are not suitable for shortening and if you used Comet springs on a twin you would almost certainly bottom out frequently. For years people have fitted longer springs, originally developed by Ken Pettiford. These are known as 'Pettiford springs'. You can very quickly tell by just looking as to which springs you have. If about one and a half inches of inner protrude out at the bottom of each spring box you probably have standard springs. If you have two and a half inches of spring then probably the Pettiford. This is with the bike on its wheels, not on a centre stand. If you have the longer springs then you can change them for the shorter original springs. Some adjustment can be obtained by slackening the lock nuts on the top and bottom eyebolts and screwing the eyebolts in as far as they will go. If that doesn't do it then the next thing is to reduce the thickness of the front part of the rubber pad within the seat. You might be able to gain and inch there but you will need some skill to make the seat look reasonable again. Let us have details of the length of the spring boxes and possibly a photo and we might be able to help more. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Rear suspension springs
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