The short spring have been made in a selection that can be mixed and matched for almost any rider or situation:
David
Comet suspension
- Thread starter redbloke1956
- Start date
The short spring have been made in a selection that can be mixed and matched for almost any rider or situation:
David
Ron,
I think that you are correct about the difference in the spindle locations, that is, they are different, but it does not matter much as the geometry is good on the Bramptons. I am a little lost on the taper roller conversion. I did not think that it altered the geometry.
Jim Young had a damaged steering head he fixed a few years ago. He machined the bearing pockets and installed new pockets to match the taper rollers. I can post the photos if you like. He might be a good source of information.
David
In addition to David's list above I also had some 102 lbs/in springs made as several twin owner had found that a combination of one 75 and one 130 rated springs was about right. I still have several of these left over from the last batch I had made if anyone want to try them. In addition I still have four 130 lbs/in left over from that same batch. Norman (Stumpy) Lord wanted a pair of these for his very fully equipped twin so I had six made in case anyone else would like to try them. Contact me if you would like to try a set. They are £15 per spring so will not break the bank and the ease with which these shorter springs can be fitted or removed is a joy compared with the standard springs.
David,
Thanks for the reply. I mentioned the difference in rear spindle distance since it is relatively large, especially compared to the links. I see the G's links are about 4" long, while the B's are 3 3/8". The front spindle distance on G's is 9.05" I will be home to measure the B's front spindle distance later today, but it must be that the longer rear spindle distance on Bramptons, combined with shorter links (and whatever the front link distance turns out to be), accounts for at least some of the good geometry of the Bramptons. Just looking at pictures, the G's links seem to have a greater angle between them than the B's. I think the spreadsheet shows the G's angle at 13.3 degrees. I think this means that getting the G's rear lower link below the front with standard springs means a lot more fork movement than the B's . Isn't this part of what the new FF2 does by increasing the distance between the rear spindles? I can see that spring rates have a part in this too, as you proved with your springs, and I guess they optimize the G's link position, but the geometry of the forks can only be changed by changing the FF2 or drilling a new hole for the front spindle. (I went through all 30 pages of the thread, and I guess most of this is obvious based on previous conversations, but I don't think I saw it exactly put this way)
I spoke to Jim a while ago about taper rollers, and based on the amount of work involved to change the bearing pockets I will be using the Patzke conversion as it came, as it is pretty well thought out and seems to have had great success on both G's and B's, but I did want to point out in relation to this discussion that on G's, (and B's) it adds about 1/8 inch to the rear spindle distance, which will marginally change the angle between the links, though not as much as the new FF2 must.
Ron
Thanks for the reply. I mentioned the difference in rear spindle distance since it is relatively large, especially compared to the links. I see the G's links are about 4" long, while the B's are 3 3/8". The front spindle distance on G's is 9.05" I will be home to measure the B's front spindle distance later today, but it must be that the longer rear spindle distance on Bramptons, combined with shorter links (and whatever the front link distance turns out to be), accounts for at least some of the good geometry of the Bramptons. Just looking at pictures, the G's links seem to have a greater angle between them than the B's. I think the spreadsheet shows the G's angle at 13.3 degrees. I think this means that getting the G's rear lower link below the front with standard springs means a lot more fork movement than the B's . Isn't this part of what the new FF2 does by increasing the distance between the rear spindles? I can see that spring rates have a part in this too, as you proved with your springs, and I guess they optimize the G's link position, but the geometry of the forks can only be changed by changing the FF2 or drilling a new hole for the front spindle. (I went through all 30 pages of the thread, and I guess most of this is obvious based on previous conversations, but I don't think I saw it exactly put this way)
I spoke to Jim a while ago about taper rollers, and based on the amount of work involved to change the bearing pockets I will be using the Patzke conversion as it came, as it is pretty well thought out and seems to have had great success on both G's and B's, but I did want to point out in relation to this discussion that on G's, (and B's) it adds about 1/8 inch to the rear spindle distance, which will marginally change the angle between the links, though not as much as the new FF2 must.
Ron
Hello Ron, One of our top men told me just to use a taper roller on the bottom, On a C, He felt it only needed it there with the weight on it, I had to take a Nat's off the stem and put a bit of shim metal round the outside of the Cup, Cheers Bill.
Ron,
Yes, the lowering of the lower link hole on the FF2 changes the geometry (as do repositioning the front lower link holes up) so that the lower link is less inclined to pivot around the front fork spindle during braking. This pivoting due to weight transfer under braking is what causes the fork to go to full extension while braking. The springs do not change the geometry, but cause the fork to be biased toward full compression. This effectively allows the lower link to sag slightly and with no spring preload (the same as the Brampton) the fork does not want to pivot around the lower front spindle.
My major concern with the taper roller conversion is that taper rollers rely on the steering stem for proper alignment. Some of the steering stems I have are not even round, never mind the rust. It seems like a lot to ask of locktite, but I have heard no complaints.
David
Yes, the lowering of the lower link hole on the FF2 changes the geometry (as do repositioning the front lower link holes up) so that the lower link is less inclined to pivot around the front fork spindle during braking. This pivoting due to weight transfer under braking is what causes the fork to go to full extension while braking. The springs do not change the geometry, but cause the fork to be biased toward full compression. This effectively allows the lower link to sag slightly and with no spring preload (the same as the Brampton) the fork does not want to pivot around the lower front spindle.
My major concern with the taper roller conversion is that taper rollers rely on the steering stem for proper alignment. Some of the steering stems I have are not even round, never mind the rust. It seems like a lot to ask of locktite, but I have heard no complaints.
David
I think from what we have seen also is the fact that under braking the wheel base is trying to shorten not lengthen.....this would be a major contributor to the forks going to full extension..... Obviously the braking force on the front wheel verses the weight of the rest of the bike plus rider, is far higher than the suspension can overcome, which , when changing the position of the lower link drastically changes this so the wheelbase CAN shorten under braking and let the forks compress as they should. If it makes a Girdraulic equipped bike behave more like Bramptons then we have a win, win situation all round....Greg.
FORK SPRINGS !!, Who needs them !, Howard, Tell Richard his front springs have fell OFF, Cheers Bill.
Hi there Bill, who's bike is this one...? I thought I was seeing double for a second....
.....Cheers.....Greg.
.....Cheers.....Greg.
Hello Greg, I don't think we are allowed to say names, He was a hard rider back in the day ! Didn't see much of him, I think he worked in Africa for a long time, When he did come back, He said I rode like an old Woman, Not that I bear a Grudge !! Funny I have had that photo for some time, And never saw it had no springs, All I saw was how high his footrests were, I get Cramp looking at it !!. He is a friend of our Howards, I would have thought he would have told us about Richard's Forks, Hurry up with that build, Can't wait to see it, Cheers Bill.