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  1. #1
    bike rider
    Reputation: Lelandjt's Avatar
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    Feb 2008

    Timing Chain Ground Clearance

    I'm trying to figure out how to get the bottom brackets lower for better handling without further compromising ground clearance. I'm switching from 34 to 32t timing rings but that's as small as I can go. I've seen people make skid plates for the bottom tube but it's the chain that I'm worried about. I want to be able to ride over rocks and ledges without worrying that all the weight of the bike is going to rest on chain. Has anyone run the lower part of the chain up over two rolls so it's even with the bottom tube and a skid plate goes below both of them?
    Keep the Country country.

  2. #2
    PMK is offline
    mtbr member
    Reputation: PMK's Avatar
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    Oct 2004
    I designed a tandem with single bike clearance. Inquired about having one custom built but did not bother. The majority of the design was on clearance and also minimal flex lengthwise.

    As for a conventional tandem setup and raising the chain, with some ingenuity rollers could be rigged up.

    FWIW, we have folded more chainrings than had chain concerns. We have many times gone over all sorts of features dragging the chain with no issues. Possibly the worse that has happened is a derailment if the tandem slides.

    I have made a carbon glide plate which is great for protecting the frame. I would like to build a spine style protector to protect both chainrings and give the chain some protection. Not difficult and easy to attach, but will require drilling the downtube and bottom tube.

    Unless you ride a lot of rocks, I would not worry about the chain, be more concerned you will bend a crank arm spider.

    Reps! We don't need no stickin' reps!

  3. #3
    bike rider
    Reputation: Lelandjt's Avatar
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    Feb 2008
    Well yeah, the idea is to be able to ride trails with rocks and have no concerns, like on my taco equipped single bikes. I decided rollers would be too heavy so now I'm thinking steel 22t timing rings on triple cranks with BMX chain. Plasti skid plate attached to bottom tube that extends under the chain.
    Keep the Country country.

  4. #4
    mtbr member
    Reputation: TandemBear's Avatar
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    Aug 2013
    I always seem to slam my front timing chainring. That's where I'd put a bash guard, UNDER the chainring to protect it and the spider. But not too low, because you're just reducing your clearance over obstacles THAT MUCH MORE!

  5. #5
    mtbr member
    Reputation: reamer41's Avatar
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    Mar 2007

    Timing Chain Ground Clearance

    I've used 24t rings on a right side timing set up. Worked great. I used stainless rings and an 8spd chain.

    SC Tallboy LTc
    Ventana ECDM 26
    ventana el Ciclon
    Litespeed Classic
    Seven Ti Axion Tandem
    1989 Stumpjumper

  6. #6
    mtbr member
    Reputation: DHMASTER's Avatar
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    Oct 2010
    This set-up has worked quite well. Steel 24 tooth timing rings, a trials bash ring for the front and a full length skid-plate.
    Attached Thumbnails Attached Thumbnails Timing Chain Ground Clearance-drive-train-sm.jpg  

    DW-DHR,VPX,SLX,SX,Stump Jumper ht.,Specialist, Bicycle Fabrications DH Tandem,Gravity Bike,Bamboo 29rs,Profile Uni,Renovo R4.

  7. #7
    mtbr member
    Reputation: switchbacktrog's Avatar
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    May 2013
    We use 32 tooth rings with an On-One bash ring. The skid plate is a piece of 70mm rain guttering reduced in width by about 30% then covered in carbon fibre effect self adhesive plastic.

    The underside of the keel-tube is covered with clear heli-tape, with the plastic skid plate stuck to that with thin double-sided tape that's normally used for sticking plastic trims to car doors.

    The chain is a one piece KMC X1 singlespeed.........KMC CHAINS Tandem Crossover Chain Nickel Plated 160 Link KMC X1 - 40.00 - Components - Chains & Spares - JD Tandems

    Timing Chain Ground Clearance-15849302948_d16d37b720_z.jpg

    Timing Chain Ground Clearance-16010961406_794918c6e4_z.jpg

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