Chuck78
Been Around the Block
alright, I am building a Rickman cr900 out of a crashed and repaired former race bike. some people will say that the bikes are better for long tracks, as they are slower steering for a racer. At 28 degrees rake, I can see why.
so I have been on a quest to design into this build a revised ride height and suspension geometry to get a more modern steepened rake, and then a good trail number by running a lower-profile 110/80-18 front tire, & slightly taller 150/70-18 rear.
this will be with very high quality suspension and Brake components, in a Reynolds 531 hand-built 1970s Rickman frame, the cream of the crop for a 1970's Vintage High Performance frame for a Japanese 4
cylinder.
I am getting some custom Billet triples made to my specifications, and I am trying to figure out the offset needed to get the proper trail, but first, I need to figure out what rake I am going to arrive at. the swing arm have two different shock mounts on it, the rear laying the shocks down more and giving a stiffer ride. The forward mounts will give a softer ride with more leverage against the springs, and raise up the rear 8mm or 5/16. I got a set of Fox Factory Shox in 14.5" length, which will put me potentially around 25 degrees rake, but with a fairly tall seat height. This will also be about the maximum the swing arm angle recommended by Dave Moss I believe it was, from a suspension setup tutorial video I watched.the original Rickman Forks are as short as possible for this frame, which was built around a very short fork. My front ride height is going to be about the same as stock aside from a shorter tire to drop it down a bit and lessen the amount of offset needed in the triples.
The Fox Factory Shox have extended lower eye mounts, and I could drop up to 9/16 inch off of the ride height just from some shorter lower eye mounts from RC Manufacturing. this is what I need to look into possibly.
my big question here is, what is the final rake that I should shoot for without going over? Some people told me to try and get it down to the 24 degree range as most modern sport bikes run. My GS 750 going from 27 to 26 degrees felt pretty fantastic in the twisties. If I could get even better than that, that would be superb. I have been told around 95 mm of trail is a pretty ideal figure for a quick turning yet still stable bike. The Rake is less of a factor in the overall feel, but still plays a big part.
my concern is, some people say go for as steep as you can get, now another fellow just told me that he thought the bike would be too twitchy since is an old flexible frame. Maybe he is under estimating the rickmans?
25 or even 25.5 degrees would be most excellent out of this, and approximately 95 mm trail. I will have to do some calculations to figure out what the rate would be if I dropped 9/16 inch off of the lower shock mounts.
so I have been on a quest to design into this build a revised ride height and suspension geometry to get a more modern steepened rake, and then a good trail number by running a lower-profile 110/80-18 front tire, & slightly taller 150/70-18 rear.
this will be with very high quality suspension and Brake components, in a Reynolds 531 hand-built 1970s Rickman frame, the cream of the crop for a 1970's Vintage High Performance frame for a Japanese 4
cylinder.
I am getting some custom Billet triples made to my specifications, and I am trying to figure out the offset needed to get the proper trail, but first, I need to figure out what rake I am going to arrive at. the swing arm have two different shock mounts on it, the rear laying the shocks down more and giving a stiffer ride. The forward mounts will give a softer ride with more leverage against the springs, and raise up the rear 8mm or 5/16. I got a set of Fox Factory Shox in 14.5" length, which will put me potentially around 25 degrees rake, but with a fairly tall seat height. This will also be about the maximum the swing arm angle recommended by Dave Moss I believe it was, from a suspension setup tutorial video I watched.the original Rickman Forks are as short as possible for this frame, which was built around a very short fork. My front ride height is going to be about the same as stock aside from a shorter tire to drop it down a bit and lessen the amount of offset needed in the triples.
The Fox Factory Shox have extended lower eye mounts, and I could drop up to 9/16 inch off of the ride height just from some shorter lower eye mounts from RC Manufacturing. this is what I need to look into possibly.
my big question here is, what is the final rake that I should shoot for without going over? Some people told me to try and get it down to the 24 degree range as most modern sport bikes run. My GS 750 going from 27 to 26 degrees felt pretty fantastic in the twisties. If I could get even better than that, that would be superb. I have been told around 95 mm of trail is a pretty ideal figure for a quick turning yet still stable bike. The Rake is less of a factor in the overall feel, but still plays a big part.
my concern is, some people say go for as steep as you can get, now another fellow just told me that he thought the bike would be too twitchy since is an old flexible frame. Maybe he is under estimating the rickmans?
25 or even 25.5 degrees would be most excellent out of this, and approximately 95 mm trail. I will have to do some calculations to figure out what the rate would be if I dropped 9/16 inch off of the lower shock mounts.