Misc: Everything Else Prototype of new AVO coilover for Series ‘D’ Vincents

[Gary Gittleson]

David,
I won't say I am unhappy with the Thornton; quite the contrary. As far as the damping goes, I'm no expert but I do take corners at a fair tilt from time to time. There are a few corners around here with some nasty dips and these shocks handle them very well. There's also a particular road with a long stretch of "washboard" surface. Neither end leaves the ground at any point, no matter the speed.

Overall, the most annoying thing with this bike is the seat height/downward slant. I do plan to visit an upholsterer to see what could be done to create a dip in the seat to give my butt a better perch, thus to mitigate the forward-slide effect. Maybe that would do it.

Thanks
Gary

 

[hadronuk]

Gary,

Initial feedback on the D AVO coilover road testing is that it is very comfortable and I see no reason why it cannot closely rival the Thornton in this respect. The Thornton/WP units are undoubtedly high quality, but the AVO may even perform a little better if the Thornton is not a good match for a particular riders needs.

Some comparisons of the AVO and WP D series coilovers:

Springing.
Looking at the photo of a WP unit, it appears that one spring can be adjusted, thereby changing the point at which the spring rate increases. Very clever.
However, the AVO unit will be available with a wide choice of spring rates and a widely adjustable preload so that it can be tailored by the customer to their personal requirements.

Damping.
Although we have not tested a WP D series coilover, we did dyno test a Thornton rear shock for B/C bikes. The characteristics were generally much like the AVO and Koni rear units, but with one difference. At high rebound velocities the Thornton became very stiff. It may be that in practice these test rebound velocities are never reached so are irrelevant, or the unit we tested was not representative. But I can’t see that excessive rebound stiffness is a good thing, as it can result in "ratcheting down" over rough roads.
It would be very interesting if David could provide more information about what Joe Stimola thought differentiated it from all others? Speculating, if he did more extensive testing representative of racing use, problems such as fade due to frothing could show up with some dampers.
One last point on damping.
All Vincent AVO units have damping that can be quickly adjusted on the bike to suit personal taste, a facility that no one else now offers.

Ride height.
I’m very optimistic that we will be able to offer a lower seat height unit with very little or no loss of comfort or load capacity. The arithmetic looks very promising, but more road testing will be needed to confirm.

Rob.

 

[davidd]

Gary,

On my Series D, I made another seat pan so I could do two things: first, get the seat upholstered with a thinner layer of foam (actually two layers) and second, narrow the seat up front. I was pleased with the results. I had noticed that the D seat on the open D was designed for the enclosed D. As a result, the seat's width extended beyond the narrower open D frame. When I made the seat pan I narrowed the seat to fit the width of the frame exactly so it did not wide my stance when standing still. This way, I could get both feet on the ground instead of one.

I had Sargents do the upholstery. They used their foam that would not bottom out over time for the first layer and added a softer layer on top.

David

 

[davidd]

Rob,

I think I mentioned before that I do have a bias in favor of the Works Performance products. I will also say that the performance of the Works dampers for the street is the same as the as the full racing dampers. They can be changed, but they are all the same tuning from Works. The tuning differs for front and rear and obviously, the D. The racers that have ridden the Works Performance Vincents have all commented on the excellent damping. These are off the shelf Woks dampers with no special tuning.

I do not get the same sense with the AVO dampers. Maybe it is still a little early for those kinds of reviews. I know Godet selected Works Performance for the new Flash and that has gotten a good review from Cam Donald, who is a very good racer.

All things considered, AVO does have the advantage in Vincent dampers because Works is no longer in business. I do think that AVO make a better damper due to your work and input and I meant no slight in expressing my long held belief that the Works dampers are top notch.

David

 

[Gary Gittleson]

David,
Your seat has a beautiful profile. I hate to undo the beautiful work the Leighton folks did but may have to do something. Maybe it can be modified without losing the overall appearance. If I get it done, I'll post a reply with a picture. It'll be a winter project. Now's the time to ride.

Gary

 

[John Cone]

There was a guy from Cambridge at the Fenman bike show last month had for sale a genuine Series "D" rear shock, was tempted to buy and have it restored but my Spax shock is just fine.

 

[hadronuk]

There was a guy from Cambridge at the Fenman bike show last month had for sale a genuine Series "D" rear shock, was tempted to buy and have it restored but my Spax shock is just fine.

Happy to be corrected, but I don't think the original Armstrong units can be restored. Crimped construction as I recall.

 

[hadronuk]

Production version of D Series rear coilover:

Testing of two prototypes of the AVO coilover for D series bikes has been completed very satisfactorily and AVO are now taking orders for the first batch produced.
Delivery could be around or just after Christmas.
The price is the same as the B/C series coilovers, £200 +p&p +VAT.
The units are a straightforward swap for the standard unit.
There are two versions, a standard version and a low seat height version.

PC1589 is the standard version.
Ride height and load carrying capacity are very close to the original, but a solo rider could set a minimal spring preload in order get a slightly lower seat height when astride the bike.
It is fitted with a 350 lb/inch spring, part number A10350.
Other spring rates are available to special order.

PC1590 is the low seat version.
The lower seat height is achieved by a ¾” reduction in the extended length of the damper that lowers the seat by about 1.125”. The closed length remains as standard.
You might reasonably think “Less travel? Must be less comfortable!”
To which I reply “Not if you set it up right!”
In stark contrast to B/C bikes, the D series design has greatly increased suspension travel. In fact it is quite good even by modern standards. Consequently, an average weight solo rider seldom uses much more than the top part of the suspension movement.
The low seat height version with the same rate spring is equally comfortable, but a larger part of the available suspension travel is used. When the low seat height version is two-up, bottoming out can be minimized by increasing the spring preload and possibly increasing the damping. This keeps the suspension travel in the centre of its range. Depending on many variables, some riders may find a single preload setting is OK for both solo and two up. Others may find it preferable to always change the settings according to load.

The low seat version is offered with a choice of springs to best match the intended use:

300lb/inch Part No A9300. Suitable for an average weight rider who usually rides solo and wants the most comfortable ride.
350lb/inch Part No A9350. Suitable for two up and solo riding. May bottom out a bit when two up.
400lb/inch Part No A9400. For predominately two-up use.

Both testers very helpfully opted for the reduced seat height option, so this option has been tested both solo and two up.

A note about centre stands. A bike fitted with the shorter coilover PC1590 will inevitably be a bit harder to lift onto the stand. Both testers report this is not a big issue, in fact one hadn’t really noticed until I asked about it!

 

[hadronuk]

A few notes about testing.

Peter Holmes did two-up and solo testing of the first (full length) prototype and with different rate springs.
AVO then revised it and converted it into the low seat height version.
Many thanks to Peter for his patience through several iterations and for his valuable feedback on two up use.

A second prototype was produced for an additional check on fit and also to test the low seat version with the lightest spring. This testing was done by Randolph Sarah. Many thanks to Randolph for his enthusiasm and feedback. He has provided this very nice photo:

I think it looks better with the lower seat height?


Couple of other things.
AVO have agreed to give the Coventry section a factory tour.
AVO are in Brackmills, Northampton, and the tour is likely to be on a Wednesday afternoon early next year. If anyone wants to join us, please PM me and I will try to get back to you when a date is fixed. The visit will also be listed on the Covoc 2019 calendar when published, but please PM me anyway so I have an idea of numbers.

AVO advertise on alternate months in MPH, so their address and phone number can be found there.

 

[Gary Gittleson]

It does indeed look better with the lowered seat height. For me, it would be practical as well. The seat itself is also nicely done. I like it better than my more traditional "D" seat. And what sort of levitation holds this bike up on just two wheels?