Ok, i have a cracked swingarm...
this has happened numerous times and as you may well see it has been patched here before, it has a strip of angle iron underneath for support but still the cracks persist, the swinger is rusty inside and so i have decided that a DIY swinger is in order!
Now, while i was considering all of this, i had a look at Phragles sticky on suspension geometry 101 http://www.blasterforum.com/do-yourself-20/suspension-geometry-101-a-11155/#post560470
i currently run a +85mm swinger with a 400ex shock. I relocated the shock mount to the stock postion when i lengthened the arm.
I did the measurements and all following phragles steps...
Once i measured the enxteded and compressed shock lengths, i cut these tubes (took me a while to figure out what he was talking about!) my compressed length is 294.8mm while my extended length is 392.5mm. therefore if i subtract the one from the other i get 97.7mm which is the travel including 12.5mm for bumper compression
I then dislocated the front shocks to lie the bike as low as possible to get the bottom out height, then chocked it up with 3inch blocks as he suggested...
Then i set about measuring the distance between a point on the axle carrier and a point on the frame vertically above it. i used a set square and a spirit level to get this point:
note the permanent marker marks...
then i mesured the bottom out distance at 295mm
Then I put the front shocks back and lifted the back of the frame up with a block and tackle. Now how high?
well, Phragle suggested you choose either between 10 and 12 inches, so i chose 11inches as my target travel. and in order to work this out we need to subtract the bottom out figure measured between the axle carrier and the frame (295mm) from the maximun travel distance measure the same way, this then leaves an opening for you to choose the upper height. so achieve 11inches ( 280mm) of travel, my maximum expanded travel needed to be 575mm between axle carrier and frame. so: 575mm - 295mm = 280mm (11 in) travel!
No fine, now the next step is to use the steel tubes and a pencil and make arcs on a piece of paper and find the intersecting point.
But before I got that far, i decided to check my setup and compare my travel to this 11 inches i had targeted.
So I put the shock back and did it all again, turns out my setup has bottoming out at 265mm andf maximun travel at 522mm therefore: 522mm - 265mm = 257mm (10.11 in) !
so basically i would only be gaining 0.89in if i were to relocate my shock mount.
I dont think this is going to be worth the effort as making my mount lower means the bolt hole will be between the legs of the swinger and that will make it impossible to fit the bolt, unless i make a double bolt linkage system, which in my mind is not worth a small amount of travel.
here is my mount as it stands:
I think this is beacuse when i extended the swinger by 85mm i kept the shock mount in the stock distance away from the front. so things didnt move in proportion...you see the axle carrier moved back in relation to the frame but the mount point stayed the same, thus enhancing travel automatically. if I had not made a new mount at the stock distance and let it go back as i extended the arm my travel would have been ridiculously small.
interesting.
So i have decided to persue the new swinger but not follow a special adpted mount between the legs as it simply is not worth the trouble! The 400ex shock is not limiting me in my riding and travel is already more than ample, i was just curious to see what a gain could be made, turns out, not that much in my case....
Now, while i was considering all of this, i had a look at Phragles sticky on suspension geometry 101 http://www.blasterforum.com/do-yourself-20/suspension-geometry-101-a-11155/#post560470
i currently run a +85mm swinger with a 400ex shock. I relocated the shock mount to the stock postion when i lengthened the arm.
I did the measurements and all following phragles steps...
Once i measured the enxteded and compressed shock lengths, i cut these tubes (took me a while to figure out what he was talking about!) my compressed length is 294.8mm while my extended length is 392.5mm. therefore if i subtract the one from the other i get 97.7mm which is the travel including 12.5mm for bumper compression
I then dislocated the front shocks to lie the bike as low as possible to get the bottom out height, then chocked it up with 3inch blocks as he suggested...
Then i set about measuring the distance between a point on the axle carrier and a point on the frame vertically above it. i used a set square and a spirit level to get this point:
note the permanent marker marks...
then i mesured the bottom out distance at 295mm
Then I put the front shocks back and lifted the back of the frame up with a block and tackle. Now how high?
well, Phragle suggested you choose either between 10 and 12 inches, so i chose 11inches as my target travel. and in order to work this out we need to subtract the bottom out figure measured between the axle carrier and the frame (295mm) from the maximun travel distance measure the same way, this then leaves an opening for you to choose the upper height. so achieve 11inches ( 280mm) of travel, my maximum expanded travel needed to be 575mm between axle carrier and frame. so: 575mm - 295mm = 280mm (11 in) travel!
No fine, now the next step is to use the steel tubes and a pencil and make arcs on a piece of paper and find the intersecting point.
But before I got that far, i decided to check my setup and compare my travel to this 11 inches i had targeted.
So I put the shock back and did it all again, turns out my setup has bottoming out at 265mm andf maximun travel at 522mm therefore: 522mm - 265mm = 257mm (10.11 in) !
so basically i would only be gaining 0.89in if i were to relocate my shock mount.
I dont think this is going to be worth the effort as making my mount lower means the bolt hole will be between the legs of the swinger and that will make it impossible to fit the bolt, unless i make a double bolt linkage system, which in my mind is not worth a small amount of travel.
here is my mount as it stands:
I think this is beacuse when i extended the swinger by 85mm i kept the shock mount in the stock distance away from the front. so things didnt move in proportion...you see the axle carrier moved back in relation to the frame but the mount point stayed the same, thus enhancing travel automatically. if I had not made a new mount at the stock distance and let it go back as i extended the arm my travel would have been ridiculously small.
interesting.
So i have decided to persue the new swinger but not follow a special adpted mount between the legs as it simply is not worth the trouble! The 400ex shock is not limiting me in my riding and travel is already more than ample, i was just curious to see what a gain could be made, turns out, not that much in my case....
