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  1. #1
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    Modernizing a Mach 4

    As you know, far too excellent to put to pasture...so I'm interested in adapting my (very early) Mach 4 to be a bit more trail oriented, with an eye on value. Current wheels are DT 240/4.2D w/2.25 Racing Ralph.

    This one.

    First steps (already taken) were low-hanging fruit...cockpit and drivetrain. 580x130 is now 710x100 (I have a crazy long torso) and 3x9 w/27t is now 1x9 w/36t. Bought only chainring and cassette. 24.5lbs at this point.

    Then, dropper. I had lowered my fixed post 1/2" and wasn't excited about spending this money just yet, despite nearly universal raves. But then ProsCloset had new OEM Reverbs in my size @ $99! It's in the mail, yet to arrive.

    Also, tires. Rims are just 18mm internal and tubed, so lightest folding 2.3 DHF/DHRs and a conversion kit are also inbound.

    Next? Time on the bike! Non-stop rain lately has local trails closed of course. I've got a few hours in on the new cockpit and I'm loving it already.

    Pondering the front end...no hurry. Current fork Magura MD100R, but apparently Pivot says 120mm is suggested for more trail/all-purpose? 120-130mm straight 9mm QR forks are rare (2018 Fox @ $650!), but if I go tapered then I almost certainly need a TA wheel too. And if buying all that, is a 27.5/26 hybrid too slack? Too ghetto? I'm really feeling 9mm and existing wheels...just too big a can to open w/tapered & TA. If I'd only kept that Reba U-Turn...

    71 HTA slackens as front end gets taller...how much extra ACL is needed for -1? Headset adapter (if used) adds effective ACL too. As would 27.5 conversion. How much is too much?

  2. #2
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    17mm= 1 degree. I would say 650b front wheel plus taller fork wouldn't slacken too much but it will raise the BB and slacken the seat tube too much. I would go with taller fork with axle, and stick with 26" front and rear. You need to be careful of how much extra leverage you put on the head tube via a taller front end be it in the form of a longer fork, or taller wheel. In the end it's all the same as far as stress on the head tube is concerned. Heavier frames it's nothing to worry about but on lighter XC/trail frames it's something that shouldn't be ignored. 20mm taller fork will be fine, but adding another 25mm to that with 650b wheel wouldn't be advised.

    I would also consider sending your rear shock to Avalanche for a tune. It's not expensive. Actually a really good deal for what you get. Ava trail tune coupled with a stiffer longer travel fork will dramatically change the feel of your bike.

  3. #3
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    Why not buying a used fork? You could also look around for a wider set of (used) wheels like Stan's or I9s for not a big chunk of money...

  4. #4
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    Yes, used fork for sure. 9mm QR, straight 1.125, 120mm travel...find me one please.

    I've managed a few rides with cockpit, tires & dropper at this point, and it's a completely different bike. No practice with the dropper makes for some awkward transitions and I'm still a bit lost without the seat to tell me where the bike is...but I've seen the light. Loving the squishy/burly tires.

    RP23 is all good...PUSHed after some blown seals, no need for an Avalanche.

  5. #5
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    Did those DT 240 hubs not have end caps you can change?

  6. #6
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    They do...but to what? Front is the earlier, non-OS version, so no TA conversion is possible.

  7. #7
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    Quote Originally Posted by dookie View Post
    They do...but to what? Front is the earlier, non-OS version, so no TA conversion is possible.
    That's what I was referring to, 15mm TA end caps. Bummer.

  8. #8
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    Some if the better SR Suntour forks like Epixons seem to be still available with straight steerer and qr. You might need to get a 27.5" fork instead of 26 but that might even be a good thing geometry wise.

  9. #9
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    I wouldn't put a 27.5 on the front, that would be a little ghetto and probably through off the steering. I love my 26, and that mach 4 looks awesome. I like the silver, but if you went to a black dropper, I bet you went to a black stem... I just got a brand new fit4 fox 120mm fork off of eaby with a 1 1/8th steerer but with a thru axle. It was really expensive.
    Ebay has a couple.
    https://www.ebay.com/itm/2018-Fox-Sh...MAAOSwbopZVDIl
    https://www.ebay.com/itm/RockShox-Re...kAAOSwyYFaPxDp
    https://www.ebay.com/itm/2018-Fox-FL...sAAOSwAHtZ-HfE
    Pink bike has a couple
    https://www.pinkbike.com/buysell/2292578/
    https://www.pinkbike.com/buysell/2247246/
    the canadians don't always want to ship to the states. I have done it a few times though, and it really isn't a big deal.
    Looking for a Medium Scott Scale frame, preferably a 2012 in 26.

  10. #10
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    As for wheels I would grab a used dtswiss 240 or 350 hub that took a through axle and some light bike carbon rims and go to town. that would be a sweet ride. You can get some KOM i-23 rims off of ebay for about 100$ a piece to save a bit of money and they are awesome rims. FWIW I think the DHF DHR tires are a little heavy and aggressive for that bike. Show us some picks when you get it build up. I love these old bikes.
    Looking for a Medium Scott Scale frame, preferably a 2012 in 26.

  11. #11
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    Sticking with the current wheels to pinch pennies, but a bit of good fortune in ebay...

    I discovered that the older 240 hubs ARE convertible to what DT calls 9mm thru-bolt, which is claimed to be noticeably stiffer than 9mm axle/QR and compatible with 9mm QR forks. $40 of caps & bolt are inbound.

    On the fork front, I have been very pleased with the Magura on there now, and I was able to get a NOS 2012 Durin 120 for $1.50/mm! No headset adapter needed and about 20mm of additional ACL. Also inbound.

    With maybe 10 rides on them now, I agree...the tires are a bit much. They add significant weight and I notice. The tubeless conversion is working well (I did need a compressor for original bead seat), but the rims are a bit narrow so I have to run a tad more pressure than I'd like. Maybe something a bit lighter next time, but I do love the bomber attitude and crazy grip! Recommend me a lightweight, high-volume knobby?
    Last edited by dookie; 02-28-2018 at 08:56 PM.

  12. #12
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    Honestly I would go back to tubes for your 18mm rims. Burping and casing roll will always be issues even at higher pressures unfortunately. Just because everyone runs tubeless doesn't mean it makes sense for every rim/tire combo. Those of us that burp flatted and rolled tires off skinny rims before tubeless ready rims and tires became the norm know this well. Wider rims help a ton when it comes to tubeless security, as does rim/tire bead design.

  13. #13
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    On my last frame, an Ibis Mojo SL, I ended up going from 140mm to 150mm for the fork, and a 27.5 front wheel. One thing that I learned is that just raising the front end like that shortens the reach. Actually it rode pretty well, and definitely handled descents better, it just felt shorter. It still climbed well, just had a tendency for the front to want to wander more.

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