triple clamp fork tube angular offset

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David Lahey
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triple clamp fork tube angular offset

Postby David Lahey » Thu Mar 31, 2011 8:29 pm

Here are some photos to illustrate the way some trials bikes have a slight angular offset between the steering axis and the fork tubes - posted to clarify this concept for a discusssion
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P3310023.JPG
TY250
P3310021.JPG
TY175
P3310020.JPG
KT250


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Greg Harding
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Re: triple clamp fork tube angular offset

Postby Greg Harding » Thu Mar 31, 2011 9:23 pm

Hi Everyone,

David, can`t help but wonder what you are up to here, perhaps some geometry changes for the TY Challenge? Something tells me you are getting in early to prepare a special for this years event!

Montesa 315`s have very little or no offset which I found a little different to stationary balance on. When you go from lock to lock on flat ground, the frame moves less at the front than other bikes of the same era.


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David Lahey
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Re: triple clamp fork tube angular offset

Postby David Lahey » Thu Mar 31, 2011 9:52 pm

Yes of course I'm bringing something special to the TY Challenge but no the steering clamp photos are not related to that. There has been a discussion going on Trials Central for some time now about why some bikes have an angular offset built into the clamps while some bikes don't, and one of the participants was having problems with the written communications, hence the explanatory photos.


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Re: triple clamp fork tube angular offset

Postby Geoff Lewis » Sat Apr 02, 2011 6:04 pm

Hi David, It is my belief that this offset is so that the manufacturer can get close to an ideal trail and rake figure and also keep the steering effort relativily low.For example my CZ has no angular offset but is fairly raked out, however it retains approx 70mm of trail. It does so because the overall offset from the stem to the forks is more than you would normally find in a British machine.The steering effort therefore is much higher than you would find in say a tiger cub. You need bloody strong shoulders some times! My Tiger Cub has bog standard frame geometry with a substantial "Angular Offset" in the headstem and steers poorly, but with no effort.My Vibsa has quite a steep rake but has less "Angular offset" but the forks are closer to the Headstem and this steers very well with little effort. My CZ however balances better than both which may be related to the steering.
Regards Geoff Lewis


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