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SL: Series 'D' Enclosures Black Prince Seat Height

tom wilson

Well Known and Active Website User
VOC Member
Hi I shall soon become a new owner of a Black Prince .... cannot wait. I only have a 29" inside leg and I would love to lower the seat height, I would have thought some Vincent owner out there has reduced the seat height .... I cannot be the only short legged owner! What would/will be the best way to lower it without affecting the handling ... shorter spring, softer spring, multi tension spring or can the spring mounting points be lowered etc. Does someone out there has the answer? No I do not want to wear platform boots or carry ladders etc.
 

hadronuk

Well Known and Active Website User
VOC Member
PLEASE NOTE
I wrote and posted the following comments earlier, but have since remembered that the calculations I did about coil binding were mainly for the B/C suspension units which use shorter springs but also have less suspension travel. So I am unsure if coil binding is much of an issue for D units.
In addition my foggy memory is confusing suspension travel at the wheel with travel at the suspension unit. Hopefully someone will measure it as suggested. AVO will have a record somewhere as well of course.
Oh the joys of getting old!



A small note of caution on preload adjustment.
It is possible to apply too much preload so that the spring becomes coil-bound before the bump stop is fully compressed. I think 4 turns is fine, but the maximum varies according to which spring and suspension unit you have.

The arithmetic is:

Length of the spring with the suspension fully extended and the chosen preload applied, minus the available suspension travel must give a number not less that the solid length of the spring.

This calculation will give a good safety margin because in practice the bump stop will never be compressed to zero thickness.
From an AVO compression test of the bump stop, my guess is that it is never going to be compressed thinner than about 8mm.
So if you want to go for the absolute maximum pre-load, reduce the suspension travel number by 8mm.
Some solid spring lengths:

!0 inch springs as usually fitted to full length units:
10 inch sprins solid.jpg

9 inch springs, as usually fitted to low seat height units:

9 inch springs solid.jpg

If you don't know what spring you have, calculate the number of turns and part turns multiplied by the measured wire thickness. It might be an idea to do this anyway because I found my measured numbers were a little different from the claimed numbers!

Regarding suspension travel, apologies but so far I have not found that in my notes.
Perhaps someone, preferably with a unit off the bike could measure it for us?
Please measure the length of the visible damper rod from the underside of the top mounting to the top of the damper body, ignoring the bump stop.
 
Last edited:

tom wilson

Well Known and Active Website User
VOC Member
Hi I shall soon become a new owner of a Black Prince .... cannot wait. I only have a 29" inside leg and I would love to lower the seat height, I would have thought some Vincent owner out there has reduced the seat height .... I cannot be the only short legged owner! What would/will be the best way to lower it without affecting the handling ... shorter spring, softer spring, multi tension spring or can the spring mounting points be lowered etc. Does someone out there has the answer? No I do not want to wear platform boots or carry ladders etc.
Hi all, at long my Prince has landed weeks late but well worth the wait. I have fitted the AVO shock absorber and it has lowered the seat height by some 30mm so well worth doing, I am also lowering the centre stand legs to suit. All being well it should be road worthy in 2 weeks max. Thank you all for your info,suggestions etc.
 

kerry

Well Known and Active Website User
VOC Member
Tom, when you lower the stand try and make it a fraction more lower on the left so that when putting it on the stand it can only fall toward you, A tiny bit makes a big difference, on mine I done this and fitted wider muffs and wider handlebars, and the avo of course. handling it is much easier now than when I got it. D's are also far nicer to ride in my opinion. I am sure you will be delighted. Kerry.
 

tom wilson

Well Known and Active Website User
VOC Member
Tom, when you lower the stand try and make it a fraction more lower on the left so that when putting it on the stand it can only fall toward you, A tiny bit makes a big difference, on mine I done this and fitted wider muffs and wider handlebars, and the avo of course. handling it is much easier now than when I got it. D's are also far nicer to ride in my opinion. I am sure you will be delighted. Kerry.
Hi Kerry thank you for the advice I will shorten the leg. Where did you get the extended muffs from and are they available? cheers Tom
 

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