Aussie 1982 CB750 DOHC - First Build
- Thread starter 750mors
- Start date
i modified and built mx bikes rear suspension back in the day when suspesion travel increased 1" a year until it reached 12" that is the beginning of my experience
do you realize what i mean about the chain issue ?
most bikes run the rear wheel thru travel that includes the tightest point ie straight line swinger pivot c/s and rear axle
this means the chain slack VARIATION is minimized(the swingarm angle isnt done this way to strictly create the least chain slack issues it just so happens that is one of the benefits of it )
all modern bikes have the c/s much closer to the swinger pivot this less-ons chain slack variations
you have the worst of all worlds great distance swinger pivot to c/s and huge angle the chain will never even reach full tight unless you have designed in so much wheel travel as to make the machine a joke on the street
you might get away with what you are doing but you will need spring loaded chain slider or roller to take up the slack at full droop
have you even hooked up a chain to observe ?
as far as swingarm angle the other actually MAIN issue is how ir responds under power to the forces of chain pull on the suspension
your setup it totally fucked in the bottom line yoy need to educate yourself on all this stuff
what you got is what we used to call ... ^&**())-rigged
do you realize what i mean about the chain issue ?
most bikes run the rear wheel thru travel that includes the tightest point ie straight line swinger pivot c/s and rear axle
this means the chain slack VARIATION is minimized(the swingarm angle isnt done this way to strictly create the least chain slack issues it just so happens that is one of the benefits of it )
all modern bikes have the c/s much closer to the swinger pivot this less-ons chain slack variations
you have the worst of all worlds great distance swinger pivot to c/s and huge angle the chain will never even reach full tight unless you have designed in so much wheel travel as to make the machine a joke on the street
you might get away with what you are doing but you will need spring loaded chain slider or roller to take up the slack at full droop
have you even hooked up a chain to observe ?
as far as swingarm angle the other actually MAIN issue is how ir responds under power to the forces of chain pull on the suspension
your setup it totally fucked in the bottom line yoy need to educate yourself on all this stuff
what you got is what we used to call ... ^&**())-rigged
and finally the swinger angle is not measured to the ground, but the angle away from all 3 axis being in centerline c/s-swinger-pivot axle,which with your front end, dropped crazily as it is ,creates EVEN more swingarm angle than meets the eye at casual glance..you have created a monster that is so outside of being correct you couldn't really have done worse if you tried on purpose
750mors
Been Around the Block
Thanks for the feedback, I do understand most of what you're saying and what I don't understand I'll educate myself on.
The shock that is in there now is the longest of the options so there is room to bring the rear down and level the swingarm out. I know it's not your perfect way to build a bike but regardless I'm enjoying the education of the trial and error.
I will definitely take your feedback onboard though.
Cheers.
The shock that is in there now is the longest of the options so there is room to bring the rear down and level the swingarm out. I know it's not your perfect way to build a bike but regardless I'm enjoying the education of the trial and error.
I will definitely take your feedback onboard though.
Cheers.
you will be looking,idealy at about 5"-6"at the vey max actual rear wheel travel measured in a straight line at the axle 7-8 inches of rear wheel travel and it will be wallowy ,out of control for high speed pavement use750mors said:
you need to set up a static point to work from this is the crucial centerline axis i mention
and coincedentilly but of import it is also the tightest point of chain tension
your wheel trave more or less need s to split that, half on each side of the centerline
to do that and have a bike that goes around corners without dragging hard parts on the floor yer gonna very likely have t raise the front a few inches....good luck carry on
Swinagrms used to be basically level for decades until manufacturers found that drooping them slightly improved certain riding characteristics. Sportbikes are usually in the 8-10 degrees of droop range. Here's the rub - literally - with too much droop the chain line cuts through the swingarm pivot at all normal settings and that's not good. With more droop, teh sprockets need to get larger and/or the front sprocket needs to be raised.
At that points things are already complicated because what's also important is the relationship of the front and rear sprockets AND the swingarm pivot. Think of it this way - draw a simple wheel, swingarm and front sprocket with a chain on. Now raise the swingarm pivot slightly and see how it changes the forces at the rear end. At certain angles that will tend to give anti squat and rotates the bike forwards to reduce the wheelie effect under acceleration. With a big angle the font will rise from acceleration and now the rear will also rise from too much droop.
At the front end, increasing the swingarm pivot height reduces rake and trail and therefore stability.
Check out http://pinkpossum.com/GT750/phattrakka/part4a.htm for more info.
At that points things are already complicated because what's also important is the relationship of the front and rear sprockets AND the swingarm pivot. Think of it this way - draw a simple wheel, swingarm and front sprocket with a chain on. Now raise the swingarm pivot slightly and see how it changes the forces at the rear end. At certain angles that will tend to give anti squat and rotates the bike forwards to reduce the wheelie effect under acceleration. With a big angle the font will rise from acceleration and now the rear will also rise from too much droop.
At the front end, increasing the swingarm pivot height reduces rake and trail and therefore stability.
Check out http://pinkpossum.com/GT750/phattrakka/part4a.htm for more info.
Great link Teazer, that helped me too. Thanks.
750mors
Been Around the Block
Thanks guys, I must admit I get a shock looking at it sometimes and remembering how I used to dream of having a project like this.
A long ways to go, but the new job will see me home more so perfect opportunity.
Evil-seed, I'll get a pic of where the mount is at soon. It's a basic mount made with 8mm? plate. I had my mate run 3 passes of weld on it and then NDT'd it (X-ray) as we just so happened to have a unit sitting at my old work.
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A long ways to go, but the new job will see me home more so perfect opportunity.
Evil-seed, I'll get a pic of where the mount is at soon. It's a basic mount made with 8mm? plate. I had my mate run 3 passes of weld on it and then NDT'd it (X-ray) as we just so happened to have a unit sitting at my old work.
Sent from my iPad using Tapatalk
