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Thread: Chumba HX1-B

  1. #1
    The White Jeff W
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    Chumba HX1-B

    So I wanted to give this 650B thing a try. Ordered a Chumba HX1 frame and a box load of parts & here it is.

    This bike has an eccentric bottom bracket that I have set to the 6 o'clock position. Even with the 650b wheels & 120mm fork it has the same bottom bracket height as my 26" hardtail with a 100mm fork and 2.0 tires.

    The obligatory garage side shot

    Chumba HX1 650B

    Seatstay clearance (Pacenti Quasi 2.0)

    seatstay

    Chainstay - a little tight around the derailleur but still plenty of clearance. You could probably run a smaller 29er wheel/tire on this thing

    seatstay

    The build...

    Chumba HX1 frame - Large

    Fork - 2009 FOX Float RLC @ 120 15mm thru axle
    Wheels - Hope Pro II hubs - Velocity Blunt wheels
    Tires - Pacenti Quasimoto 2.0
    Brakes - Formula ORO K24
    Cranks - Truvativ Stylo 2.2
    Shifters - Sram X.9
    Derailleurs - Sram X.9
    Bars - Alpha X-roc carbon fiber
    Stem - Race Face
    Seatpost - Thomson Elite
    Seat - WTB Shadow
    Pedals - Wellgo magnesium flats on there now but will probably run my Shimano clipless

    Weight 26 lbs 6oz
    Last edited by jeffw-13; 12-01-2009 at 05:57 AM.

  2. #2
    mtbr member
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    I like the look of that alot.
    Nice build.
    J

  3. #3
    ride more
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    nice build, very pretty

  4. #4
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    Really really nice.Enjoy!

  5. #5
    www.derbyrims.com
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    Nice to see a clearly 650b ready design. Other manufacturors should take note that there's no loss making wheel space for 650b, especially for larger sizes.

    26 inch wheels have always looked too small for the larger sizes, at least without very large tires.

  6. #6
    The White Jeff W
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    So I got 'er out for a good shakedown ride today.

    It's been wet here so I swapped out the 2.0 Quasi up front in favor of a 2.35 Nevegal in anticipation of some sloppy conditions. That proved to be a good call. Wet leaves over mud. Set pressures at 30 psi & set up the Fox fork to their recommendations & off I went.

    Before hitting the trails I usually start my regular ride with a moderate climb up an old closed road that runs along the length of the park for a warm up. I definitely felt the taller gearing right away. I run a 34 tooth ring up front on my Yeti but went with a 36 on this bike. That combined with the taller tire makes a big difference in the effort required to get up the hills. I found myself on the small ring a lot more than usual today. I'm sure eventually I'll build up the leg strength to turn the taller gear & be able to reap the benefits. On the flats the extra speed was noticeable & getting up short moderate climbs on the middle ring was a breeze with the extra momentum.

    The bike handles great. Conditions weren't really favorable for high speed riding but when I was able to unleash it it railed the corners. A couple times I started to lose the front end but the Neve would dig in & save it a the last minute. On steep climbs the front felt slightly lifty, if that's a word. I'm going to pull a spacer from the stack before tomorrows ride & I think that should bring it in to the sweet spot.

    Someone asked about the stiffness of the frame. Yeah, it's stiff, but that's to be expected from an aluminum A.M. hardtail, no? I've ridden nothing but full suspension for the past year so it was noticeable for sure but not uncomfortable. 10 hours later my 42 year old back & ass are just fine. I actually like the stiffness. Makes it more responsive & predictable in the turns, which is what I was looking for in this bike.

    The Fox fork with the 15mm axle felt really good right off the bat. Definitely stiffer than the 140mm Revelation on my Yeti. I'm considering swapping out the lowers on my Rev to Maxle now. I set everything right in the middle & probably wont change anything more than a click or two when I'm done.

    Brakes are awesome. I run the same ones on My Yeti so no surprises there. Same with the Sram derailleurs. Flawless, as usual.

    Overall great first ride. It started a little tentative while I got the feel of the bike but once I got over the first logover & got a little air it was on Hopefully tomorrow conditions will be a little better & I can really let 'er rip & see what she's got.

    Forgot to mention, I love the loud bzzzzzz of the Hope rear hub. I no longer scare the **** out of hikers. They hear me coming long before I get there
    Last edited by jeffw-13; 11-29-2009 at 07:41 AM.

  7. #7
    The White Jeff W
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    So today I pull one headset spacer & head out for ride two. About 10 minutes in I was feeling a little stretched out, like I could maybe run a shorter stem. At the first break I pulled the tools out & moved the bar back a bit.

    -Money- whole new bike! Getting the weight bias a little more to the front definitely helped on the climbs. The front is planted going up & not wandering around like it was yesterday. It also helped cornering. This thing absolutely rails. It's everything I hoped it would be. Stiff frame, stiff fork, low center of gravity, flickable. The head angle with the 120mm fork feels perfect. Just steep enough for tight, fast cornering but slack enough to get down hills without feeling like you're about to go over the bars.

    I fa king love this bike.

    A couple random notes...

    The Quasimoto is not a mud tire.

    Continental needs to make a 650b Mountain King Supersonic

    Run a hi clamp front derailleur on this frame for more rear tire clearance (about 3/8" vs the low clamp I used.) Replacement on the way.

    Horses on narrow trails s-u-c-k.

    Horse poo on your water bottle & new bike also suck.

    A lady hiker said 'wow, you really look fit' as I was grinding up a long climb in the granny gear. She was fat. It was the first time I made it to the top of this hill without stopping. Go me

  8. #8
    Baby Bear is in the house
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    Quote Originally Posted by jeffw-13
    Chainstay - a little tight around the derailleur but still plenty of clearance. You could probably run a smaller 29er wheel/tire on this thing

    seatstay
    Tons of clearance on there
    I agree with derby. Why can't more manufacturers do their seat stay clearance like this? I mean, Surly has been doing it for quite a while with their FFF stays. The Brits seem to have got it a bit right. But of course, they're not designing with 650B in mind... but the seat stay mud clearance on their frames make them good candidates for 650B conversions (e.g., On One Inbred).

    Nice build!
    Better to have and not need it, than to need it and not have it.

  9. #9
    The White Jeff W
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    I doubt Chumba had 650B in mind when they designed this frame but I think the massive tire clearance typical of AM type frames makes them good candidates for 650B conversion.

    The thing that put this one to the top of my list was the eccentric bottom bracket. Like I said in my original post, with it moved to the 6 o'clock position the bottom bracket height is the same as my 26" wheeled hardtail.

  10. #10
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    Nice!

    Ok, I've got some questions:

    This isn't a 650B frame?! The clearance in the seat and chainstays looks great, and the tire doesn't look like it's going to hit the seat tube. Wonder what a 26" wheel would look like in it.

    How is the clearance in the Fox fork? Are you aware of the concern about rubbing the tire on the bottom of the steerer tube during a bottom out?

    Are you running 2x9? If so, what's your small ring?

    Really like the white frame/fork!

    I just finished building up a Soma B-Side 1x9 (see the recent post). Very pleased, after 3 rides. Like steel, like bigger wheels, like tubeless! It all adds up to a pretty darn comfy ride for a hard tail. My 44 y/o body needs it!

    From your pics, the Pacenti's don't look that appealing. I stuck with Nevegals because I really liked them on my FS. And I don't have to worry about anything wet out here in AZ.

    Glad you're enjoying your new ride.

  11. #11
    The White Jeff W
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    This isn't a 650B frame?! The clearance in the seat and chainstays looks great, and the tire doesn't look like it's going to hit the seat tube.
    It's not a 650B frame but is designed to clear big fat 26" tires. Plenty of tire clearance at the seat tube but it does get pretty close to the low clamp derailleur I have on it. I'll be changing it out to a high clamp which will give me about another 3/8" clearance.


    How is the clearance in the Fox fork? Are you aware of the concern about rubbing the tire on the bottom of the steerer tube during a bottom out?
    There's about a pencil's width of clearance with a 2.3 Nevegal mounted. (see the pic below) I am aware of the bottom out issue and intend to address it.

    Are you running 2x9? If so, what's your small ring?
    Yes, 2x9. The small ring is a 24 tooth.


  12. #12
    mtbr member
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    Quote Originally Posted by titus247
    Ok, I've got some questions:

    This isn't a 650B frame?! The clearance in the seat and chainstays looks great, and the tire doesn't look like it's going to hit the seat tube. Wonder what a 26" wheel would look like in it.

    How is the clearance in the Fox fork? Are you aware of the concern about rubbing the tire on the bottom of the steerer tube during a bottom out?

    Are you running 2x9? If so, what's your small ring?

    Really like the white frame/fork!

    I just finished building up a Soma B-Side 1x9 (see the recent post). Very pleased, after 3 rides. Like steel, like bigger wheels, like tubeless! It all adds up to a pretty darn comfy ride for a hard tail. My 44 y/o body needs it!

    From your pics, the Pacenti's don't look that appealing. I stuck with Nevegals because I really liked them on my FS. And I don't have to worry about anything wet out here in AZ.

    Glad you're enjoying your new ride.
    I wouldn't discount the Pacenti tires for AZ conditions. In fact, I'd wager that you might like them even better than the Kendas for your trail conditions. Just my two cents.

  13. #13
    The White Jeff W
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    Another little review now that I've got some quality miles on this thing.

    The only changes I've made from the original build was going to the high clamp rear derailleur for tire clearance and I changed the front gearing to 22-32. The area I ride has a lot of steep climbs and the tall rings up front were just a little too much for my old legs.

    I'm running Nevegals front & rear for winter/spring sloppy conditions. They give great traction for climbing and so far every time the bike has started to go out from under me in a turn I've been able to save it when the side lugs dig in.

    On the down side the bike sits a little taller with the fat knobbies & feels a little less nimble than it did with the shorter 2.0 Quasi's. I'm looking forward to when things dry out & I can put the smaller, lighter tires back on.

    I still love the bike & find myself reaching for it more ofter than the Yeti 575 sitting next to it in the garage. There's a park with 12 miles of single track about a 3 mile pavement ride from my front door and the Chumba is perfect for it. It's mostly fast, twisty non technical single track, lots of shortish but steep climbs and some longer hills to get the legs burning.

    The 575 gets the nod when I venture out to the more technical stuff in the area, if only to save my back & ass. I might take the Chumba out there some time & see how she handles the rougher stuff in the area. I'm also looking forward to racing this thing. It's a little heavy by race bike standards but it's fast & nimble & should do well.

    Anyways I finally remembered to throw the camera in the pack today & got a muddy non-garage side shot.


  14. #14
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    derby if you ever produce a 26" carbon rim, i will be ordering those up and mounting surly dirt wizard 2.75" on there - then driving down to chumba to see if it will fit this frame, that wheelset is what my next bike will be based on so i hope you do it!!!!

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