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Spring lengths.

youngjohn

Well Known and Active Forum Website User
Non-VOC Member
Are there different length springs available for Vincents? The back of my Comet looks a bit 'gawky' and I think it could do with lowering a little. There looks to be more of the inner spring box chrome showing on my bike than on some bikes. Currently the distance between the eyes of the spring units is 10" with the bike standing up on level ground. In pictures, the front of some bikes seems lower too. Can Girdraulics be adjusted for height?
 

bmetcalf

Well Known and Active Forum Website User
VOC Member
You may have longer length Petteford springs on the back, standard length may you. Some people put short lengths of PVC pipe or broom handle on top of the front springs to raise the front. KTB may have some info on this.
 

Albervin

Well Known and Active Forum Website User
VOC Member
Check the gauge of your rear springs, they may be sidecar springs & so don't compress as easily as solo springs.
 

BigEd

Well Known and Active Forum Website User
VOC Member
VOC Forum Website Moderator
I removed my rear spring units on my Rapide this morning so here are a few measurements.
What I assume to be a standard spring, free length = 170mm.
A longer spring that I have and assume to be a Pettiford, free length = 195mm.
These are not new springs so may have settled a little.
The (assumed) standard spring coil bound length = 100mm.
Don't know what the (assumed) Pettiford is coil bound as my vice is only just big enough to take a standard spring and I am allergic to inadequately secured springs decompressing themselves and flying around my garage. :eek:

An uncompressed assembled unit with (assumed) standard spring unit is approximately 240mm over the SP4 hole centres.
An uncompressed assembled unit with (assumed) Pettiford spring unit is approximately 265mm over the SP4 hole centres.
Figures are approximate as the SP4's can be screwed in or out to alter the centres a little.

If you have a damper mounted between the spring boxes then this may be what limits the extremes of travel. I have an Armstrong damper at the back and measuring between the hole centre in the UFM and the hole centre in the RFM I got these approximate measurements:
Fully extended = 255mm. (Close to the 10 inches you say you have on your bike.)
Fully compressed = 195mm.

I think that rear springs are available in different gauges too. Standard gauge is 0.300" and there were some lighter 0.276" gauge ones made. There were also heavier 0.324" gauge springs made for sidecar use.

You may find you have different dimensions but these figures will give you something to compare too.

OK, back to the garage as I am supposed to be going out on the bike tonight.


Are there different length springs available for Vincents? The back of my Comet looks a bit 'gawky' and I think it could do with lowering a little. There looks to be more of the inner spring box chrome showing on my bike than on some bikes. Currently the distance between the eyes of the spring units is 10" with the bike standing up on level ground. In pictures, the front of some bikes seems lower too. Can Girdraulics be adjusted for height?
 
Last edited:

Ken Tidswell

Well Known and Active Forum Website User
VOC Member
Yuo don't say if the bike uses the standard seating arrangement or if it is fully sprung.. Longer rear springs makes the steering more 'nervous'
that is does it fall into corners as you turn the bars? Or do you have to deliberately steer it. If you are satisfied with the handling why bother? Otherwise you can buy new standard springs from
your local friendly dealer. The Comet spring weight as originally fitted were found to bottom, so twin gauge springs were fitted . My springs are 71/2 inches long
when fitted but have settled a bit .
 

youngjohn

Well Known and Active Forum Website User
Non-VOC Member
Many thanks for the spring length info, I think that it may also be to do with the maximum length of the damper. which is a standard Vincent. I'm wondering if there is a diagram or photo of the inside of the damper, maybe I could put a spacer or rubber stop inside to reduce its maximum length? The bike rides beautifully, it's purely an asthetic issue but it really bugs me.
 

davidd

Well Known and Active Forum Website User
VOC Member
Youngjohn,

I would run the bike as stock as possible. It sounds like you have no serious handling problems, so do not change it for looks. As a point of interest, front springs that are adjustable for ride height are available in the U.S. in several rates. I would not shim up the front springs unless you have a lot of experience with your Vincent. I would leave them stock until they disappoint you.

David
 

Bill Thomas

Well Known and Active Forum Website User
VOC Member
Hello John, Unless you weigh 18 stone, I would think those Petteford springs are a bit hard, I am 14 stone and I found some springs in my box that are thinner than all the others, I think they were for the comet, And it rides fine. Check that the eye bolts are not turned out too far.Put a photo on the Forum so that we can see it.Like Davidd says, try and keep it Stock, As they say in the USA ( Don't mess with it or it will bite you in the bottom !!). By jacking the back up you are tipping the forks down, You don't want to do that !. Have a think about fitting a hydraulic steering damper. All The Best Bill.
 

Albervin

Well Known and Active Forum Website User
VOC Member
I removed my rear spring units on my Rapide this morning so here are a few measurements.
What I assume to be a standard spring, free length = 170mm.
A longer spring that I have and assume to be a Pettiford, free length = 195mm.
These are not new springs so may have settled a little.
The standard spring coil bound length = 100mm.
Don't know what the Pettiford is coil bound as my vice is only just big enough to take a standard spring and I am allergic to inadequately secured springs decompressing themselves and flying around my garage. :eek:

An uncompressed assembled unit with standard spring unit is approximately 240mm over the SP4 hole centres.
An uncompressed assembled unit with Pettiford spring unit is approximately 265mm over the SP4 hole centres.
Figures are approximate as the SP4's can be screwed in or out to alter the centres a little.

If you have a damper mounted between the spring boxes then this may be what limits the extremes of travel. I have an Armstrong damper at the back and measuring between the hole centre in the UFM and the hole centre in the RFM I got these approximate measurements:
Fully extended = 255mm. (Close to the 10 inches you say you have on your bike.)
Fully compressed = 195mm.

I think that rear springs are available in different gauges too. Standard gauge is 0.300" and There were some lighter 0.276" gauge ones made. There were also be heavier 0.324" gauge springs made for sidecar use.

You may find you have different dimensions but these figures will give you something to compare too.

OK, back to the garage as I am supposed to be going out on the bike tonight.
I have discovered a wide variation in distance between centres of spring units & dampers. It is important you match both the extended & compressed lengths of
the combination you have otherwise there will be some serious banging of metal.
It is also important how you mount your springs/damper. For instance, you can have the bike on a "D" type stand or the original rear stand. This will make a huge
difference in how you fit your suspension. On a "D" type stand the suspension is fitted at the extreme of extension & this should be just less than the extreme extension of
the damper. Be aware that the SP4s should be screwed in at least 3 threads to hold the plot together.
When using the rear stand you can adjust the suspension by using a jack under the cases but you still need to be aware of where the compression & extension limits are.
Some dampers can be used with a bump stop rubber & others cannot. You can tell if you need one by the "clang" you hear !!!
 
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