TOPIC:

I have a plan to change the rear structure of my frame and want some input on my ideas.

1. I want to relocate the shock mounts from location A to location B. I have noticed that the area where the studs are located now (A) is hollow. I plan on drilling a hole through the frame at point B for the new stud. Will this reduce the integrity of my frame? How about after being welded? What about threaded vs. welded?

2. The dash line is where I would like to cut the rear completely off. There is a 1 inch to 1.5 inch tubular brace between the frame before the cut for strength. I looked at the geometry of the frame and noticed the only strength I need is basically for the seat pan. All loads seem to be transferred through the swing arm into the frame at its lowest point.

The purpose for this radical change is to smooth the shock line and clean the rear of the bike without changing to a mono-shock style swingarm. Then I can use a newer style plastic tail design and just see the beauty of the fat tyre sticking out of the back

What are my concerns? Advice? please excuse the hasty diagram I made.

Thanks for all your help in advance.

Post edited by: NightRider, at: 2005/12/17 18:39

Post edited by: NightRider, at: 2005/12/17 18:42

you would be putting the shock absorber in a bind,picture the swingarm pivoting without the shocks it goes through a certain arc as it travels up and down your shocks would either bind or try to bend. you would have to make lower mounts similar to the old mono shock system on yamaha yz dirtbikes 70s-80s but with two shocks . also tube b would bend under the suspension load unless it was heavily gusseted!hope this helps,happy wrenching!

Post edited by: wireguy, at: 2005/12/17 19:28

instead of reloctaing the shock top, maybe relocate the shock bottom, with something like this:

www.jcwhitney.com/autoparts/Product/show...?Ntt=lowering%20kits

I thought of the arc of travel, and compared my measurements with the ZRX1100. I thought I would be within exceptable tolerances...Like the bike in the pic below. I still planned on reinforcement. Things that make you go Hmmm.

Perhaps my diagram was over exaggerated. I plan on using the same geometry as the 1100. If I relocate the bottom mount I will place more stress than what I expect in my original ideas. The swingarm would then effectively push the shock forward reducing its desired rate of dampening. I was mainly concerned with frame stress and posted to see if any 'yall had tried this before. If you look at the ZRX1100 you'll see a greater angle than what I plan to use,in this picture it seems like the shock would be stressed...
If my calculations are correct my mods should raise the rear, a desired result, and have little to no cavitation of my suspension. Like in the picture, directing the force directly under my butt.
Thanks for the input...


Post edited by: NightRider, at: 2005/12/17 21:25

Post edited by: NightRider, at: 2005/12/17 21:29

Post edited by: NightRider, at: 2005/12/17 21:33

that looks a lot better, your origional drawing had the shocks at about a 45-60 * angle which wouldnt work very good keeping them in the same general area as the origional frame gusset should work ok.if it were me i would weld some heavy gauge sleeves with threads inside through the existing frame gusset to mount your shocks in the location where you want them and have a machinist make you some studs like the front foot peg brackets use i would als weld sleeves in place of the origional top mounts so you have a bit of adjustability incase your shocks dont work right!any decent welding shop shoul be able to perform this work.hope this helps,happy wrenching!

I personally am dead set against drilling holes in frame tubes. Weld a bracket/gusset/shock mount similiar to stock upper shock mount. Weld only on the radius of the tube so as not to create stress risers. Get the best welder you know of to do the job as well. All your shock loads are going into "A" position. Not to mention lateral loads when cornering. Moving upper shock mount will effect shock binding/stiction and travel. May not notice it when straight up and down but heeled over in a corner it may be noticeable.

RomSpaceKnight:what do you think of the idea of welding the sleeves in the the stock shock gussets?i think that is probably the strongest/safest point to put the shock mounts without seriously changing the geometry of suspension it would also be somewhat adjustable. i dont like the idea of doing the shock mounts anywhere else from a strengh/safety standpoint!

Wireguy, I was wondering about those lowering kits in Duncan's post. Do they go on swingarm or do they locate at top shock mount. Can't quite picture what your idea is about heavy gauge sleeves.

those lowering brackets go on the swingarm to push the bottem of the shock back to lower it,i thought they quit making them years ago,i didnt like them 20 years ago and my opinion has not changed!my idea was to make a sleeve like the front foot peg bracket mounting studs screw into one in the sock location and one a little further forward but still in the stock shock mount gusset.that you could screw a stud like the footpeg mount into but you could use it in either sleeve so it wouldbe adjustable!does that make sense?