Shock Absorbers - assorted info

Discussion in 'Spare Parts, Tools & Product Developement' started by DougC, Oct 9, 2009.

  1. DougC

    DougC Guest

    If you have a frame that uses suspension (or are building a frame that will) this is some info that may save you some time. I've been looking and asking around for a couple weeks now and this is what I managed to find out.

    If you want the suspension to work as well as possible, it is necessary to obtain a shock absorber that has rebound dampening. This is the "hydraulic" portion of hydraulic shocks. Without this dampening you risk the pogo effect, that can reduce your braking and steering abilities to very-close-to-nothing at the worst possible times. Many of the better MTB shocks now have adjustable dampening rates, but the adjustability isn't so critical for on-road use as the dampening being there at all.

    The main (US-sold) MTB shock companies all offer rebound dampening on all their shocks. The main names to look for are-
    Fox Racing
    Rock Shox
    Manitou
    Marzocchi
    DT Swiss
    ...the last two seem to be the more-expensive, the prices overall ranging from ~$150 to over $500 each.

    You really have to search for new shocks under $100. There's lots of "barely used" ones in eBay, but you never know what that means, and even more important--replacement parts may not be available. One place I found that does have a few NOS (new, old-stock) is Chain Reaction Cycles.

    If you're building a motorized bike, then it will probably mostly get used on pavement--which is an advantage from the durability standpoint just because the shock seals won't be exposed to so much mud and dirt as they would get on a normal MTB. Most better MTB shocks can be rebuilt with new seals but the seal kits need to be still available, or the parts need to be simple enough that you can improvise other parts or make new ones yourself.

    MTB shock absorbers tend to come in only a few lengths and are usually measured by the length between both mounting eyelets. The lengths are getting longer over time and shorter shocks are getting discontinued, so if you're scratch-building suspension it might be wise to plan ahead for this to allow your suspension to mount a longer shock in the years ahead.
    For quality MTB shock absorbers,
    165mm used to be common, but is now on the decline.
    190mm and 200mm are common, 220mm is becoming common.
    Some of the upper-end shocks are now available in 240mm and longer.

    Some older shocks do not have eyelets on both ends; one end of these was made to fit into either a special frame-integral fitting, or a yoke (into the center of a "U"-shaped suspension piece) that only fit on a limited number of bicycles. These may be sold cheap (because of their limited application) but mounting them in anything other than the intended bicycle can involve a lot more problems.

    There are other Orient-based OEM companies that are "generic", who only sell wholesale quantities to bicycle manufacturers. Sometimes quantities of these wind up on eBay when somebody buys up a parts supply and sells them off individually. Not all of these items are junk, in particular the Yasusu shocks look pretty decent,,, but you need to be careful about what you're buying, and I never turned up any easy source of replacement parts for any of these.
    Some companies you will see on eBay are-
    DNM
    Yen Yue
    Yasusu

    A lot of department-store bicycles also come with shock absorbers. These are not wise to plan on using for two reasons: first is that they usually don't have any sort of dampening other than internal friction, which decreases as they wear out. Second is that they usually are in older/shorter lengths.

    One website I found that sells some "low-end" shocks is http://bikebuyers.com
    If you search there for suspension, they currently show three coil-over shocks available (-they do not state the manufacturer-):
    350-lb spring for $30
    750-lb spring for $33
    1000lb spring for $36

    The prices are great, but none of these mention any sort of dampening mechanism.
    Another problem is the lengths: the 350lb one is only 5" long (125mm) and the other two are 6" long (150mm). Recall from above that I mentioned that the shortest length you can get good shocks in now is 165mm. None of the name-brand companies makes good (dampened) 150mm shocks anymore, they stopped making them during the mid-1990's. They're all gone now.

    -------

    I also considered using minibike or go-kart shock absorbers. These are available various places online and the prices are not bad (~$40-$50 per shock, for ones with hydraulic dampening) but the problem is that the overall lengths are relatively long, usually at least twelve inches / 300mm--fully 50% longer than common MTB shocks.
    ~
     
    Last edited by a moderator: Oct 9, 2009

  2. Warner

    Warner Member

    I am thinking of converting my old Trek mountain bike over to suspension forks. At the same time, I want to convert to a front disc brake setup and threadless headset so I can get some higher rise handlebars. It seems like doing all of these things at the same time is the only way to do it. But you bring up good points about the length of the forks.....as the geometry of the frame for non-suspension bikes is generally different than one designed for longer suspension forks. I just think my bike would be much more comfortable and safer (with the disc brakes) with these mods. I don't know how much all of it would cost......but it's probably not cheap I suppose....

    Warner
     
  3. cpuaid

    cpuaid Member

    Great info, Doug! Had to get rid of my early 90's Diamondback MTB because it was cost prohibitive finding replacement shocks for the thing. Hopefully this will help out others when buying a used bike with blown front shocks. When the shocks costs more than the bike, that good deal you came across isn't so good after all.
     
  4. retromike3

    retromike3 Member

    shock up front

    The problem I had with replacing a rigid front fork suspension one is the increase in bottom bracket height. If your B.B. is too high than the bike will "dive" into the turns making no hands ride an impossibility. I had to switch back to a rigid fork just for that reason.

    Finding a threaded 1 1/8th fork and headset is not an easy job nowadays.

    Next time I am going to design a motorbike bike from scratch with 1 1/8th head tube with suspension figured in and rear dropout with a long horizontal take up room with a detailer hanger.:D

    Mike Frye
     
  5. DougC

    DougC Guest

    I may end up seeing if I cannot figure out a way to use the minibike shocks.
    The more-compact MTB shocks would be nicer all around, but they cost roughly 10X what the minibike shocks do....
    (another advantage is to be able to design for one shock length; minibike shocks have been the same 12 inches legnth for at least forty years)
    ~
     
    Last edited by a moderator: Oct 25, 2009
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