Rat Bike Rear Suspension Options

Discussion in 'Some Assembly Required' started by elgato gordo, Jan 21, 2012.

  1. elgato gordo

    elgato gordo KTMRFS

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    After reading several of the builds here that are going for an increase suspension the most challenging seems to be the rear. Without significant swingarm mods only a slight increase in rear travel is possible.

    I checked out what I have in the garage, KTM SX/EXC and both shocks are around 16 inches long, eye to eye. Since the most the street bikes seem to be around 12 inches long that's a big change in the frame geometry.

    Looking over specs for the KLR and the DR650/DR400 they provide fair amount of travel 9+ inches but I'm wondering what the length of the shock is. Does anyone have any of these in the garage they can measure?

    Also there are some fancy (expensive) after market shocks for KLR/DR on ebay that could provide the needed damping increase options for heavier bikes. One of the Ninja threads had a custom ohlin but not sure which one and don't remember the specs.

    Edit:
    DR650 455mm long with 128mm travel: from ( http://drriders.com/topic1777.html )
    #1
  2. elgato gordo

    elgato gordo KTMRFS

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    Here is some info from the SV guys. They don't like their shocks either.

    source:
    http://www.svrider.com/forum/showthread.php?t=45179

    YEAR MOTORCYCLE LENGTH SPRING*
    ===== ========= ===== =====
    00-03 GSXR750 325mm 400#*

    01-03 GSXR600 325.5mm 450# *corrected by TWF...thanks!*

    01-02 GSXR1000 329.5mm 430#*

    03-04 SV650 330mm 430# <== stock 2nd gen...05 should be the same

    99-03 GSXR1300(Busa) 330mm 700#*

    04 GSXR750 332.5mm 408#*

    04 GSXR600 332.5mm 425#*

    03-04 GSXR1000 332.5mm 480#*

    99-02 SV650 337mm 510# <<<====stock 1st gen

    04 ZX10R 338mm 540#*

    03-04 ZX6R(636) 340mm 540# *corrected by e lo...thanks!

    96-99 GSXR750 345mm 375#*

    97-00 GSXR600 375mm 375#

    05 GSX-R 1000 332.5mm 450# <<<===added by me...spring rate from racetech.com, length from ohlins.com
    _________________

    EDIT: Correction to above from GrahamB on: January 27, 2007, 05:28:18 AM*

    96-99 GSXR750 356mm*

    97-00 GSXR600 356mm*

    05 GSX-R 1000 325mm

    The 345mm GSXR750 shock is only for use with a kit linkage Ohlins made. I've no idea where the 375mm came from.
    Could we get these corrected before someone else buys a shock with the wrong expectations?

    Also, regarding the recommended spring rates, the Traxxion web site recommends 500lb/in (9kg/mm) for gen 2 & 650 for gen 1, 160lb rider.

    I happen to agree with that for the gen 2, no comment on gen 1.
    #2
  3. elgato gordo

    elgato gordo KTMRFS

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    From the Versys owners thread:
    http://advrider.com/forums/showthread.php?t=276645&highlight=woody's&page=221

    Elka Custom 3 WAY rear shock with adventure dampening rates 1/2" longer eye length and 2" more rear wheel travel and hydraulic preload adjustor and adjustable length for ride height:
    Stock shock is 300mm long, 52mm travel (248mm compressed)
    We have a 312.5mm long shock with 64mm travel with or without adjustable length
    Adjustable length
    Extended 312mm +/-5
    Travel 64mm
    Compressed 248mm +/-5
    6" long 900 kg rear spring
    25% compression reduction from street valve rates for adventure riding
    33% rebound reduction from street valve rates for adventure riding

    Elka custom shock: $1,400:eek1
    #3
  4. dentvet

    dentvet Long timer

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    The 2002 honda cbr600f4i shock is 305mm long with a 60mm stroke. 14.2 kg/mm spring rate = ~800#/in
    #4
  5. dentvet

    dentvet Long timer

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    [​IMG]

    The problem with the 650 motor is that its mass centralized? to make it more compact. If you look at the side of the motor, it looks like Igor. Weird.

    The clutch basket and thus the countershaft are humped up to the side of the crank pin. The height of the countersprocket makes the swingarm slope downward to the rear axle more than a more traditional layout. This makes it harder to gain travel by increasing the shock length.

    Also, the motor's face looks like Wall-E.:lol3
    #5
  6. SkiBumBrian

    SkiBumBrian DualSport Crazy !!

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    A stock KLR shock is 15 7/8" CL eye to eye... Cogent Dynamics makes their Moab shock for dual sports, Ricor also makes an aftermarket shock with IAS (Inertia active system) for most bikes. Both of these companies will build the spring and valving for your weight, bike, and riding style. I personally have the Ricor system front and rear on my KLR and it is not even the same bike. Well worth the fairly hefty pricetag...
    #6
  7. elgato gordo

    elgato gordo KTMRFS

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    The Elka shock was claiming +2 inches of travel so that puts the Versys at about 8 inches with 64mm of stroke. If you really get that much travel from 64mm if stroke.

    They did add a BRP chain guide on the lower swingarm to help but they may be getting some heavy wear on the top chain guide from the angle they are putting the chain at.

    Still 8 to 9 inches is not too bad for this kind of bike.
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  8. elgato gordo

    elgato gordo KTMRFS

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    SkiBumBrian

    At almost 16 inches looks like the the KLR shock is similar to the other dirt type shocks. Thanks for the info.
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  9. SkiBumBrian

    SkiBumBrian DualSport Crazy !!

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    No problem !
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  10. jdrocks

    jdrocks Gravel Runner

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    if by "rat" you're talking about the ninja/versys builds (since the OP is looking for one), you need to look at the geometry of the OEM swingarm with the stock shock mounts. this is obviously not a linked suspension, so a relatively small change in the length of the shock translates to a relatively large change at the rear axle. there's been quite a bit of discussion on the subject over the last 3 years, but i think the ratio is something like 1/2.0 or 1/2.5.

    consider that for every unit that the swingarm is forced down effectively raising the rear, the front suspension also needs to be raised the same amount. another limiting factor is the tire hitting the fender liner before you run out of travel, also much discussed. so if you have a 12" shock that bolts up, it doesn't automatically mean that a longer shock will work with the stock swingarm/shock mount/subframe configuration.
    #10
  11. elgato gordo

    elgato gordo KTMRFS

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    I was referring to sport mods in general but most popular seems to be the Ninja recently. Seems like the only options in the Ninja are to mod the swingarm to allow a longer shock and/or add some chain guide or tension devices like way back when we first started seeing long travel suspension.

    Someone posted a table of Ninja wheel travel compared to shock length awhile back. I thought I came up with about 1/2.75 as a ratio from that data. Either way the Elka shock rear wheel travel claims seem a bit overstated.

    On bike with link suspension there may be some more adjustment if you change some of the link dimensions. Problem with that is it could hang down below the frame and get caught on rocks and stuff. Also it hurts my head to predict changes in leverage and such.
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  12. dentvet

    dentvet Long timer

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    There are further options for the ninja such as grafting on a different swingarm and doing a custom shock mount and subframe. Sailah has done similar mods to his CBR and i wish he would keep working on that thing :ear


    The ninja shock swaps are just too easy so everybody has just stopped there. Around here, offroad is in the woods so the mass of the bike is as much a limiting factor as the rear suspension. In other words, the ninja isn't limited as much from a weak rear suspension as from being too heavy to weave and bob around trees. Out in the desert i could see the lack of rear travel slowing things down, though.

    I am skeptical of 8 inches travel on ELKA/versys setup, i think jdrocks pointed out that the versys/ninja subframes were pretty similar in layout. (My ninja has 6 inches)

    The SV bikes could be slightly easier in that you might be able to use the stock swingarm but it looks like you still need a custom subframe/shock mount to make room for a long shock. However, xr200 shock was 13.5 inches or 340mm, hmmm.......

    BTW, there's a ninja at salvage not far from here if you are still looking and are willing to ship it
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  13. elgato gordo

    elgato gordo KTMRFS

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    Dentvet

    I have a couple of prospects in the southwest that I only have to drive a few hours to pick up. Looked into shipping, at $500 it kind of blows my budget.

    Also went to Cogent website. They have a good selection (KLR, DR650, DL650) and sounds like a fair option for the price. Saw some of the WeeStrom guys talking about making a buy of several units to bring the cost down. May even be a chance for a "custom" one for the Ninja if enough people are interested.

    Do you have the post of the rear wheel travel versus shock length from one of the Ninja builds. Can't find it right now.
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  14. jdrocks

    jdrocks Gravel Runner

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    without a series of other modifications, this is where the tire hits first...

    [​IMG]

    next would be the battery box, and by that time you might as well start cutting up the subframe and extending the swingarm. the work can all be done, but you still have a heavy bike.

    the Elka can't get 8" travel on a stock Versys, and i doubt it would ever outperform the inexpensive R1 swap anyway.

    i'm satisfied with the DRZ/R1 setup, it runs real well for my purposes.
    #14
  15. dentvet

    dentvet Long timer

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    http://advrider.com/forums/showpost.php?p=15115681&postcount=18

    Are you calculating ratios off these numbers? I built my ninja as a poor man's bmw800. The bikes have similar rear suspension configuration but i haven't seen any analysis/comparison of the componentry.
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  16. elgato gordo

    elgato gordo KTMRFS

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    These are the only numbers I have seen posted as such. The ratio of wheel travel to shock length seems to be a good number to size up the rear suspension changes. I get about 2.75 to 1.

    Thanks for digging that one up.

    On a different note I won an auction for an '05 SV650 today so the adventure begins.:clap
    #16