My Lack of Shock Knowledge is Shocking!

[NoControl]

My huge glut of work (since February) has now finally shown signs of ending. This will give me some time now for some of my builds. Thanks, God!

I'm dreaming up a design for a fork that will utilize a couple small motorcycle shocks. I've briefly looked on ebay and saw a bzillion different styles and lengths. I'm sure that I can find something that will lend itself into my design, but first I wanted to see what you guys think. Has anyone done this, and what did you use for a shock? I was thinking that a pair of rear shocks that would be stock OEM for like a 1972 Honda SL70 might have just enough dampening, yet not be hard as a rock. What do you folks think?

 

[rickpaulos]

90% of bicycle "shock forks" and frame shocks are not shock absorbers. Most forks have coil springs springs inside the blades with plastic sleeves that have some friction.The next step up in shock fork design is elastomers: rubbery blocks inside that often disintegrate over time and can run $100 to rebuild. Decent bicycle shock forks with air compression or valved oil dampening are rather pricey. Like $600 to $2000. The biggest maker Rock Shox kept changing designs and migrating technology down the product line. Comparing them is tough because you never know what is inside. Then they got bought out and the new owners dumped all info and they don't offer support to legacy products. There are dimensions to consider: steerer diameter, steerer length, threaded or threadless headset, wheel size, brake mounts, overall travel.

Most cheap bicycle frame shocks are coil over with a plastic or dried out rubber sleeve on the inside that doesn't really absorb shock so much as just add friction. Decent frame shocks like Fox start at $250. They come in many lengths. A good one is adjustable with proper air pressure. There is a special pump that doesn't let air out when you disconnect so you can get exact pressure settings.

So yeah, looking at lightweight motorcycle parts makes some sense. Shocks that are real shocks for <$100/pr. Very cheap compared to comparable bicycle technology. Look for spring weight, dampening, physical measurements, colors, etc.. Buy a pair and build your fork to work with them. You would want light rated spring weight for the front end. There are countless springer/shock fork desigs you can emulate. Some forks only use 1 shock. I'd try to keep the shocks small to keep the weight down. Excess sprung weight isn't good for any vehicle. Much depends on what you want, looks or functionality. I suggest reading up on head angles, rake and trail so the final product is actually rideable.

 

[Bigcam59]

you might consider an earles style front suspension...

 

[NoControl]

you might consider an earles style front suspension...

This is more or less what I am going to design and build.

 

[Indyjps]

Well thats just cool. Hadnt seen these before. I have some springer fork designs dancing around in my head and this just sidetracked me.