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Any old-style DHi closet weight-weenies here? Save 300g

Discussion in 'Downhill & Freeride' started by - seb, Mar 31, 2008.

  1. - seb

    - seb Turbo Monkey

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    Right, cut to the chase, this is regarding the DHi's custom MRP:

    origianl weight: 570g

    1) without bottom roller: 480g
    I lost my bottom roller on a ride 2-3 years ago, and was lazy in replacing it. In fact I never replaced it, and in those 2-3 years I've NEVER dropped a chain. I put this down to a combination of running my chain as tight as I can, having a small block on the back (11-26), the DHi's limited chain growth, and having a chainring smaller than the chaindevices max capacity (40t on a 40-44 world cup guide).

    Only recently got around to removing the mount for the roller too. Result? About 90g saved (those rollers are heavy!)

    2) slalom carbon instead of alu WC: 360g
    I'm doing the megavalanche this summer, and decided I want a smaller chainring for that. Then I thought about how often I get to crank at 40/11 and it's hardly ever, so figured I may as well make a permanent switch. The world cup guide can only go down to 40t without a lot of rubbing, and I wanted to run a 36t. Bought a (carbon) slalom outer, and a alu. C-plate inner.

    Result? 120g saved

    3) system1 & trimming: 274g
    Someone bought to my attention the idea of converting the bike to system 1. I.e. two rotating plates. With that there'd be (obviously) no need for the C-plate, which in turn means there's no need for the backplate, almost. Unfortunately the backplate controls the position of the top roller, and can't be eliminated due to the eccentric's movement. However... you CAN trim a lot off of it. Bought a second carbon plate for the inner, and got busy with a hacksaw and dremel. The bottom two corners were completely redundant, but I got a bit keen and removed some of the top section as well. It's THICK aluminium, and does very little, so in my opinion definitely well overbuilt for the job.

    Result? Another 86g saved, and now 300g total saved compared to the original guide. Plus it looks a feck-load sexier! (Though I forgot to take a pic of it on the bike :p) :D

    PS: yes, I know, my hacksawing and dremmeling sucks, I got bored! (And I broke the dremel).

    Disclaimer: I am having to run longer chainring bolts (which I only have in steel at the moment) and some hacked-up-from-an-old-chainring spacers, so that has added 20g.
     

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  2. Dartman

    Dartman Old Bastard Mike

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    Isn't that a bit like trimming the toenails off an elephant?
     
  3. - seb

    - seb Turbo Monkey

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    A bit, but if the elephant is your absolute favourite animal, and you couldn't bear to ride (oo-er) any other jungle creature, and you've already trimmed all of his ear hair and fitted him with titanium ligaments and mag/ti stirrups and a ti saddle suspended on a Thomson ElephantRide(TM) Masterpiece, then you may as well trim his toenails as well! :)
     
  4. Dartman

    Dartman Old Bastard Mike

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    hehehe...well said.

    Actually I had a DHi for a time. It was a fast bike that pedaled well.

    You're right though it could go on a diet.
     
  5. ire

    ire Turbo Monkey

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    are we going to see pics of the actual bike?
     
  6. - seb

    - seb Turbo Monkey

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    OK, here ya go:



    It's pretty light (sub 36 (without mud :p)) so I'll probably do a separate thread about that soon with some better photos. That one just quickly snapped in my kitchen/living room.
     
  7. Mlody

    Mlody Monkey

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    sweet bike!
    Mine weights in at 42.5 so it's quite heavy... but I'm lightening it up.
    I just bought new front wheel (Mavic EN521, DT Revos and Tioga Suzue DH) so it should be about 0.6lb lighter.
     

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  8. William42

    William42 fork ways

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    my bike weighs about 46 without mud, just think what a little time, money, and passion can do to your bike.

    annorexia, here i come! cheap mans way of losing weight
     
  9. Gary

    Gary "S" is for "neo-luddite"

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    Seb - why not take the roller off, replace it with a bolt (Ti if you have to:) ) leave 1mm clearance above the plates and it'll do the same job. you might need to rotate the boomerang forward a little so that on compression the chain doesn't pull on the bolt.

    I ran my (homemade) MRP type 1 like that for years - never dropped a chain ever - I did run a lower roller tho.
     
  10. jvnixon

    jvnixon Turbo Monkey

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    As gary said... you could probably get away with a custom setup instead of that top roller if you're not dropping the chain as is... I'd want the roller on teh bottom personally but if it works for you then no reason to change it I suppose..

     
  11. - seb

    - seb Turbo Monkey

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    Yeah, works for me without, so see no reason to add one. Will go for a bolt mod soon, just not got around to it yet. I can't "rotate the boomerang" though because it's got a crazy linkage to the frame. Ideally I would get rid of the boomerang entirely and just have a bolt attached to the frame, but again, can't do that because of the eccentric.
     
  12. Rick205

    Rick205 Monkey

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    I did the bolt mod a few weeks ago to my MRP, just left the bolt that used to hold the roller in place, will sort a smaller one out soon that looks slightly 'nicer' - works great.

    Nice looking DHI seb, i remember following your 222 back in the day (i had a 222 aswell but mine was about 8lbs heavier!) and see your getting back into the weight thing - im just knocking the lbs off my lapierre, wheels next, i reccon im going to try schwalble (sp?) tires next, im only light so an 850g tire will knock almost a kilo off rotatioal weight - worth a try.

    Rick
     
  13. FreeRide-Junkie

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    Nice to see people still like the DHIs. It's what I might end up on for a while this coming season.
     
  14. ire

    ire Turbo Monkey

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    Sick DHI, and damn light. Makes me wish I still had mine
     
  15. - seb

    - seb Turbo Monkey

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    I never thought I would be happy to "add" weight to my bike, but when my Ultimate Sports hanging scale was about 100g off (outside of their claimed 0.5% accuracy) I was perturbed.

    Looking hard at my bike and trying to figure out what (if anything) I'd forgotton to weigh, I realised that my chain device weight seemed a bit low. Sure enough I'd forgotten to weigh the steel sandwich plates that the MRP backplate sits in.

    Annoying, but at least now everything tallies.

    So, all of the weights in the original post, +106g.

    I'm contemplating ditching the whole thing and runnign just the dual plates with no rollers at all. I think the plates are deep enough, my chaingrowth minimal enough, my cassette range small enough, and my chain tight enough, that it might work.

    On the other hand it might not, but 294g (everything bar the two rotating plates) is a lot of crap for one top roller. Worth trying I reckon. MIGHT be ok :)


    edit: I'm sure no-one cares, I just don't like inaccurate weights being posted, so thought I should correct it. In retrospect I should have just edited the first post, doh.