The LC4 Skidplate Thread (and skidplates in general)

Discussion in 'Thumpers' started by PackMule, Aug 28, 2006.

  1. PackMule

    PackMule love what you do Super Moderator

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    As a new recruit to the LC4 world ('96 620 RXC, btw), the only immediate hard-parts addition that I wanted to make to my bike was an aluminum skidplate. The bike came with the KTM poly-resin unit -- which the PO had fitted to ward off rocks kicked back from the front wheel.

    With the rocky conditions here in New England, and the trail duty the mighty LC4 will see, I assumed a metal unit would be necessary in order to garner any actual impact protection (vs. kick-backs). :kurt


    PM'ing with one of the frequent LC4 contributors, he bluntly asked why I thought the poly-resin unit inadequate. Although he didn't have any direct or anecdotal evidence one way or the other, he pointed out that "sometimes composites are tougher than metals."


    After thinking about it, I realized that I didn't have much, other than Dogma, to support my line of thinking. Just about every "real" dirtbike I've seen has a metal skidplate, the only "plastic" types I'm familiar with being the ones found stock on a KLR (which explode on contact). But I guess that doesn't necessarily mean diddly. So, does a KTM "Poly-resin" skidplate provide useful impact protection? :dunno


    A quick search, just to show what the options are and the parts we're talking about:

    Here's a link to the KTM schematic at MunnRacing. Part #15 is the poly-resin plate, #19 the aluminium piece.
    [​IMG]

    KTM Poly-resin ($65 At KTMCyclehutt and MunnRacing)
    [​IMG]


    KTM aluminum ($115 At KTMCyclehutt and MunnRacing)
    [​IMG]


    Moose Aluminum ($75 at powersportsnetwork.com)
    [​IMG]

    Aluminum from Utahsportcycle ($77)
    The LC4 specific plate
    [​IMG]

    General features (not KTM specific)
    [​IMG]

    I spoke with Mike at Utahsportcycle on the phone and asked whether this plate uses the stock mounting bolts, or their tabs. He went out back and checked -- it uses the tabs. Looking at the KTM schematic, it seems like you could simply drill it to accept the "half moon" KTM adapters (part #22, which I've already got from the poly skidplate), although I'm not sure whether the front comes up to where it could reach the forward mouting point. Not that there's anything necessarily wrong with the USS mounting tabs in the first place.


    There are also carbon-fiber skidplates out there, though I didn't see one specifically listed for the LC4.




    I guess my questions could be distilled down as follows:


    • Do the KTM Poly-Resin skidplates provide useful impact protection, or are they designed to deflect kicked-up rocks, only?

    • Do Carbon Fiber skidplates provide useful impact protection, or are they designed to deflect kicked-up rocks, only?

    • If one does choose an aluminum unit, what are the considerations other than price to take into account? Does the $115 KTM unit provide "better" protection than the others?

    • What other options are there besides the ones I've listed?


    If you've had positive (or negative) real-world experience with any of the various skidplate types, please add your comments (and pics!). :ear


    As of right now, I think I'm leaning toward the UtahSportCycle plate, but I'll wait a bit and see what shakes out of this thread before ordering. :lurk


    Thanks, all
    #1
  2. djchan

    djchan Long timer

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    I've been advised by other riders that the protection offered by the plastic is as good as that offered by (my) aluminum model. I don't know first hand. I DO know the metal makes your engine noise noticeably louder as it deflects back to the rider instead of hitting the dirt. I'm in NE as well (Maine) and have some pretty dreadful looking rock nicks in my plate.

    Dean
    #2
  3. creeper

    creeper Still alive...

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    You've pretty much covered all the potential materials for a skid plate.

    In my experience:

    Poly resin is quite stout stuff, a touch heavy, and will take some horrendous hits... and will crack when they go, but I've never seen it.
    Quieter than alloy. Cheaper than everything.

    Carbon fiber is very light and if made correctly, will take some horrendous hits... and de-laminate when they go, which I've seen... a cheapy plate.
    Quieter than alloy... more money than alloy.

    Aluminum is light, stout and will take some horrendous hits.... and distort and/or fracture when the go, which I've seen.
    Reflect noise unless you use a deadening material.

    Hyde racing makes a Teflon/mystery spooge skid plate... but I don't think they have one for the LC4 yet.

    I kinda like the poly resin plates, and if I didn't already have the OEM alloy job, I'd get a resin one.
    Loaded has a CF plate... he seems happy with it, but he's a known fibber.

    The KTM alloy plate (and PR plate) fit the best as they use the alloy block mounts... rock solid stuff.
    I wouldn't buy a clamp mount plate for nothin'... cheesy, lazy engineering IMHO.

    A bit of alternate thought (see, I got no bias)... trials bikes all come with heat treated alloy skid plates. Trials riders "use" their skid plates more than any other kind of rider... to the point where a pro will replace them a few times a season when the usual, dragging them over rocks all day has taken it's toll.

    [​IMG]

    They don't run carbon... to fragile in this application. They don't run PR... to heavy for a trials bike.

    [​IMG]

    C
    #3
  4. nfranco

    nfranco over macho grande?

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    Anybody tried rhino lining their alloy skid plate(at non contact points) to help with noise or am I over thinking this?
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  5. Airhead

    Airhead More human than human

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    Come on...I've ridden with you, and I know there are no rocks (or water) on the trails you ride...:lol3

    I have the alu one, and it's taken some pretty brutal hits. Has a few dents and deep scratches in it, but nothing I can't live with. The composite plates just don't inspire the same kind of confidence in me...I'm sure they will deflect rocks that are kicked up by the front wheel just fine, but what about when you high center at 30mph on a rock that is firmly embedded in the ground and hidden in tall grass (not that I've ever done that...:augie)...what then, huh?
    #5
  6. Airhead

    Airhead More human than human

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    BTW...

    :confused
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  7. creeper

    creeper Still alive...

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    A shot of Takahisa Fujinami, "rotating" his HRC Montesa (skidplate) on a rock... I believe at the Portugal world trials round in '05.
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  8. Hipster

    Hipster Long timer

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    I have the KTM poly on my bike and its held up well over the years. The only real draw back I see in the poly skid plate is if you ride in cold weather (below freezing) it could crack if it took a big hit. Otherwise its lighter and quitier then Aluminum.
    #8
  9. Loadedagain

    Loadedagain making chips

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    creeper is a wanker. as usual the wanker is correct. i do have a carbon skidplate that is very well made (thanks matey peeps btw.).

    when it came time to run the alcan 5000 i removed it and installed the oem ktm plate on my 2002 640. i do trust the carbon piece, but the properties of carbon fibre don't make it too useful after one good hard hit. aluminium on the other hand can sustain many hits without weakening.

    loaded opinion? run carbon for bling. run aluminium if you want to run hard without changing out your skid plate.
    #9
  10. KTM BIGGER

    KTM BIGGER n00b

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    Well, i can tell you this much. I have the aluminium original skid plate and it looks nice and does the job well. It has prevented major damage to my engine and frame on numerous occasions.
    The only down fall with this unit is that the noise level from the engine are much greater due to them getting reflected straight back at you.

    Other than that the original piece is a good piece of kit.

    You bike should have come out with this originally if you purchased it new.
    #10
  11. creeper

    creeper Still alive...

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    :cry


    :clap
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  12. 2whlrcr

    2whlrcr gooligan

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    Good thing aluminum is corrosion resistant too.

    [​IMG]
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  13. meat popsicle

    meat popsicle Ignostic

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    Great input so far eh! :nod

    HERE is a thread on the other CF skidplate for the LC4. No rotating on rocks; with the 640a I hope that never happens.

    I would think that for the ADV folk, a skidplate must shield the case from rocks spit up by the front wheel "indefinately", but protection from the one in a million hit should be "adequate". Meaning it should adequately disburse the impact and resist penetration :evil, at least once. If you are used to high-centering on pointy rocks repeatedly then perhaps you need more than adequate protection.

    The KTM Rallye skidplate, as found on the mid model 660s, appears to be just a thin layer of CF.
    [​IMG]

    The KTM Baja skidplate also appears to be just a thin layer of CF.
    [​IMG]

    The later model Dakar bikes had some kind of underlayer I believe, but it might just have been the mandatory water storage unit. Anyways, it could be that the racing bikes don't bother with a tougher skidplate because they can replace them at will, but they must be adequate eh?

    With my limited understanding of materials and their inherent strengths and weaknesses, I think that either a mixture of CF and Kevlar, or CF overlain with Kevlar, would be an ideal compliment of strengths. The Kevlar would resist abrasion and penetration, while the CF would provide structural rigidity. Perhaps the Kevlar would help the CF resist cracking? It does seem like an ideal marriage...

    Es muy dos centavos. :jose

    ADD: Regarding the original question of the thread. It seems the KTM poly-resin skidplate has enough merit to give her a try. No one seems to think it would not provide adequate protection in a bad situation. :ear
    #13
  14. Loadedagain

    Loadedagain making chips

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    you know i still love you.
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  15. creeper

    creeper Still alive...

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    :feelgood
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  16. KenR

    KenR Long timer

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    Keep in mind that the thin CF skidplates shown on the factory race bikes are just that - part of a factory bike that gets copious amounts of money, time and attention paid to it. They likely get one event out of each plate then it gets chucked for a new one.
    #16
  17. Loadedagain

    Loadedagain making chips

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    the fist part of yer first sentence pretty well covers the rest. :nod

    carbon and kevlar are fibres. in 99% of commercially available motorcycle parts the fibre present is totally irrelivent. the matrix that holds these fibres together is the part that matters. your skid plate can be carbon, kevlar, e-glass, or pixie dust and it don't matter a fuck. you hit a rock and the cocksuker will give. once the matrix breaks (usually polyester or some cheapass epoxy like "sun cure" or "west systems") the show is over. all impact strength is gone... and believe me it doesn't take much.

    oems (and i assume ktm is one) usually use "pre pregs" with resins embedded in the fibre. these are not cheap and usually require kiln firing in order to cure. their strength is usually much more than the stuff you're getting for "mere mortal dollars".

    if you wanna me... i'll do a composite tech/how to... for now that's it.
    #17
  18. meat popsicle

    meat popsicle Ignostic

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    I was hoping for a blurb (thanks for biting); if you want to do a how-to I would be glad to read it. I know you just got back from the Alcan, and you are probably busy with your steed (anything more on her?), so I won't hold my breath. I am particularly interested in which are the good resins for the various methods. The rest below is just clarification :augie

    Since here we are in public, let me walk further out onto the aforementioned limb... so what I think Loaded was saying is if the resin is crap then the fiber is meaningless. I did not mention that in my post; its great having these folks around who do this for a living eh! That makes sense since the resin is part and parcel of the matrix.

    And sure the big mfgs use kilo-ton presses to set their CF parts and mere mortals use vacuum bagging - are the results of the methods different enough that the cheaper stuff is worthless? The answer to that one question is worth the painstaking editing that went into this post. :lol3
    #18
  19. bmwktmbill

    bmwktmbill Traveler

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    If you are interested my '02 skid plate(OEM 640 Adventure) will be for sale shortly.
    I am awaiting a delivery from Europe.
    Bill in Tomahawk, WI
    #19
  20. PackMule

    PackMule love what you do Super Moderator

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    :ear :evil
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