FF: Forks Modified Steering Stem

[hadronuk]

No, I don't think so. Remember that Chris has still to optimise the damper and he still has a lot of adjustment left.

A note to Chris and other testers using the AVO front damper. At the "max" setting the rebound damping force is about twice the damping force at "min", but bump stiffness is hardly altered. So increased stiffness may not be immediately obvious, but topping out should be reduced. This damper behaviour is partly because dampers with a single adjustment do generally tend to alter rebound more than bump, but is also because the AVO for the front is at the very lower end of its settings range and this was a necessary compromise.
I'm sure AVO would be happy to supply (or re-valve) a front damper to be the same as the rear dampers. In fact this is the setting I first tested for the front. With the standard forks I thought it was quite a bit too stiff, but with your altered geometry and reduced friction it might work well. Compared to the front, the rear damper has a higher minimum setting, but usefully for you the adjustment range is wider than the front and does significantly alter the bump as well as the rebound.

 

[greg brillus]

To be clear on Chris's comments, it is obvious at this point that replacing the bushes with sealed bearings has now allowed the front forks to move a lot easier than with the original bushes. I must admit that I have not experienced this because thus far all my conversions have had the bearing up grade. I've created a "Monster".............Well I can see exactly what David is describing, but we are now finding out the pro's and con's of these changes. Looking at Chris's bike it has more spring pre load than I currently have, while his front shock absorber is probably on the soft setting side. Extra adjustment on the re-bound should help, though I feel that perhaps the springs themselves may still need looking at. Because of these changes is it not unreasonable to expect that a "One spring suits all" situation may not be a good enough approach, and that several different spring rates may be needed. When the suspension is set up with stiffer springs the bike is more capable of handling a broader weight range of riders, whereas now we have made the forks not only safe, more compliant, and a softer ride, it is now that final part that is harder to tune, because instead of the forks being stiff and almost dangerous, they are now light as a feather and a lot more "Active". By comparison, the current springs in my Rapide started off as 40 Lb spring rate and were 3 inches longer than an original spring. These were way too long, so I cut off 3 inches on each one, By my rough calculations I would say the same springs are now closer to 50 Lb's rate and I think they took about 1 1/2 inches of preload to install, similar springs on Neal's Comet which we also shortened, had about less than an inch of pre load. After riding Neal's Comet I felt that if that was the same on my Twin I would be very happy. The same setup is now on MartynG's Comet and I sent him the 30 LB springs, so it will be interesting to hear his feedback. We are getting closer, but like I said.......I think we still need to play springs a little more. The interest has grown big time on this subject which has proven to me that there are plenty of active riders who are keen enough to commit to a change, and that is great.

 

[Chris Launders]

I'm sorry if I gave the impression that the forks were topping out and diving violently, this was not the case but doing it quicker than I would like, but at no time did they bottom out. I have the same travel as with the bushes but the forks are reacting much quicker that's all, this can be controlled by damper adjustment.

 

[Martyn Goodwin]

To be clear on Chris's comments, it is obvious at this point that replacing the bushes with sealed bearings has now allowed the front forks to move a lot easier than with the original bushes. I must admit that I have not experienced this because thus far all my conversions have had the bearing up grade. I've created a "Monster".............Well I can see exactly what David is describing, but we are now finding out the pro's and con's of these changes. Looking at Chris's bike it has more spring pre load than I currently have, while his front shock absorber is probably on the soft setting side. Extra adjustment on the re-bound should help, though I feel that perhaps the springs themselves may still need looking at. Because of these changes is it not unreasonable to expect that a "One spring suits all" situation may not be a good enough approach, and that several different spring rates may be needed. When the suspension is set up with stiffer springs the bike is more capable of handling a broader weight range of riders, whereas now we have made the forks not only safe, more compliant, and a softer ride, it is now that final part that is harder to tune, because instead of the forks being stiff and almost dangerous, they are now light as a feather and a lot more "Active". By comparison, the current springs in my Rapide started off as 40 Lb spring rate and were 3 inches longer than an original spring. These were way too long, so I cut off 3 inches on each one, By my rough calculations I would say the same springs are now closer to 50 Lb's rate and I think they took about 1 1/2 inches of preload to install, similar springs on Neal's Comet which we also shortened, had about less than an inch of pre load. After riding Neal's Comet I felt that if that was the same on my Twin I would be very happy. The same setup is now on MartynG's Comet and I sent him the 30 LB springs, so it will be interesting to hear his feedback. We are getting closer, but like I said.......I think we still need to play springs a little more. The interest has grown big time on this subject which has proven to me that there are plenty of active riders who are keen enough to commit to a change, and that is great.

I have just finished the reassembly and am looking for a volunteer to test ride it as due to my back surgery l am not able to just yet. Any takers?

 

[b'knighted]

Sure, Martin, anything to help.
Just send it over to the UK.
Cheers

 

[Chris Launders]

I'll do it, just need expenses for two (wouldn't be allowed on my own)

 

[Martyn Goodwin]

To be clear on Chris's comments, ((SNIP)). The same setup is now on MartynG's Comet and I sent him the 30 LB springs, so it will be interesting to hear his feedback. We are getting closer, but like I said.......I think we still need to play springs a little more. The interest has grown big time on this subject which has proven to me that there are plenty of active riders who are keen enough to commit to a change, and that is great.

Quick status. Not yet road tested - but some static information. With the 30 Lb springs supplied via Greg the initial sag with no load at all on the bike is almost zero - its essentially topped out. With me sitting on the bike the sag measured in terms of front shock absporber travel (its a Thornton unit) is a wisker under 3/4". Before I fitted the spring boxes I measured the total available front travel (again in terms of front shocker movement) at 2 3/4". If I put the bike on its centre stand (a tred-down) , sit right forward onto the tank and then start slowely bouncing up and down then there is a good 1 1/4" to 1 3/4" of suspension travel - without the front brake applied AND with also with the front brake applied.

I have a volunteer test rider lined up for this Sunday.

 

[Martyn Goodwin]

I'll do it, just need expenses for two (wouldn't be allowed on my own)

Sorry - no pillion pegs on the bike. Bugger!

 

[timetraveller]

For those who might want to know, here are the measurements on the damper, the spring boxes and the vertical movement of the wheel with the standard set up and the JE modification.
Standard Damper 70 mm Spring box 68 Wheel 108 Ratio SB/W = 0.63 Ratio D/SB = 1.03 Ratio D/W = 0.65
JE Mod 63 mm 74 70 = 1.06 = 0.85 = 0.90

If anyone else would like to check these values it would be useful as they were obtained while the normal bearings were in place which give quite a lot of resistance to movement and hence quite a jerky motion when moved by hand.

 

[davidd]

I believe that Greg mentioned the stainless dust caps in this post. I just wanted to support the idea that you have to check these caps for over all height (and thickness, possibly) to get a good fit.

Four dust caps, four heights.

David