There is a lot of information in MPH and other sources about sizing the rear springs for the extra load of a passenger. Eddie Stevens has a table of recommendations for this in Chapter 22 of his great book "Know Thy Beast".
It occurred to me that all of this suspension/passenger info is wrong, at least in regard to the standard geometry of the A,Band C models.
I have one C Rapide which has the long struts in place to make the seat into the fully suspended type. This bike has heavier than stock rear springs and it needs them, it all works quite well when loaded up. It also carries a full set of luggage on a rack that connects to the seat and the pillion footrest support plate, so that load is on the rear springs as well.
The other Rapide is very softly sprung, has the standard C rear suspension, so the rear of the seat bobs up and down when going down the road. I always assumed that with it's very soft springs it would bottom out easily with a passenger on board. Even with it's much stronger springs, the fully suspended bike will bottom out on a really sharp bump, like when hitting a bridge deck that is 4" above the main road surface, that sort of thing.
To my amazement when I did try out the soft sprung bike with a passenger on board, it seemed to handle the bumps just fine, no easy bottoming at least. I was totally comfortable, however my passenger ,who normally rides on the fully sprung bike, was not so happy. Apparently it was a pretty jarring ride
For me, it seemed pretty much the same as when I ride it solo. The reason for this is that virtually none of the weight of the passenger is transmitted to the rear suspension. Other than the small amount of weight placed on the passenger footrests, all passenger weight is transferred directly thru the seat stays to the rigid top member of the rear frame and from there to the rear axle and ground. The only suspension for the passenger is the same as it was on my rigid framed 1949 Matchless G80, just whatever the tire and seat can provide.
To get an idea of how rigid the back end is on a standard non D Vincent, have someone hold the bike while you shove down on the seat in the area where the passenger's weight is centered. I could not get the rear suspension on the supple standard bike to budge when doing this. I have since tried this on another standard C, same result..
There is an easy fix however, and it is the already well known solution of the long struts or the fully suspended type seat/luggage carrier.
If you aren't going with either of these fully suspended routes and insist on the stock seat stays, you might as well keep some fairly soft springs in the back end, just whatever you and the luggage need, since virtually none of the passenger's weight enters into the equation.
Glen
It occurred to me that all of this suspension/passenger info is wrong, at least in regard to the standard geometry of the A,Band C models.
I have one C Rapide which has the long struts in place to make the seat into the fully suspended type. This bike has heavier than stock rear springs and it needs them, it all works quite well when loaded up. It also carries a full set of luggage on a rack that connects to the seat and the pillion footrest support plate, so that load is on the rear springs as well.
The other Rapide is very softly sprung, has the standard C rear suspension, so the rear of the seat bobs up and down when going down the road. I always assumed that with it's very soft springs it would bottom out easily with a passenger on board. Even with it's much stronger springs, the fully suspended bike will bottom out on a really sharp bump, like when hitting a bridge deck that is 4" above the main road surface, that sort of thing.
To my amazement when I did try out the soft sprung bike with a passenger on board, it seemed to handle the bumps just fine, no easy bottoming at least. I was totally comfortable, however my passenger ,who normally rides on the fully sprung bike, was not so happy. Apparently it was a pretty jarring ride
For me, it seemed pretty much the same as when I ride it solo. The reason for this is that virtually none of the weight of the passenger is transmitted to the rear suspension. Other than the small amount of weight placed on the passenger footrests, all passenger weight is transferred directly thru the seat stays to the rigid top member of the rear frame and from there to the rear axle and ground. The only suspension for the passenger is the same as it was on my rigid framed 1949 Matchless G80, just whatever the tire and seat can provide.
To get an idea of how rigid the back end is on a standard non D Vincent, have someone hold the bike while you shove down on the seat in the area where the passenger's weight is centered. I could not get the rear suspension on the supple standard bike to budge when doing this. I have since tried this on another standard C, same result..
There is an easy fix however, and it is the already well known solution of the long struts or the fully suspended type seat/luggage carrier.
If you aren't going with either of these fully suspended routes and insist on the stock seat stays, you might as well keep some fairly soft springs in the back end, just whatever you and the luggage need, since virtually none of the passenger's weight enters into the equation.
Glen
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