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  1. #1
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    Flex on the Rear of my WFO

    I got a new 2012 WFO a month ago, and have been loving it for everything, especially with the addition of a Pushed RC3 on back. It rides the chunk, it rides the smooth, it rides it all with so little effort. And I am just amazed by how well it pedals for a 140mm rear bike. I definitely believe in the CVA suspension, and will be rocking this bike on a 74 mile 14,000 feet elevation race later this summer.

    But there is one area that I am not that excited about the bike, but not sure if it is the frame's fault. I live in Park City, and the trails here are really flowy, with lots of big banked switchbacks and lots of quick left to right bermed turns. I can really attack these and feel pretty confident on this bike, but there seems to be a decent amount of flex in the rear. I thought at first it was the tire pressure, as I live to ride my tubeless 2.4 Ardents kind of low (22-24 psi), but I aired them up to around 29, and I get the same feeling when I quickly change from loading the rear from the left back to the right and vice-versa. I have the 142x12mm thru axle rear, which I thought would be plenty stiff, as I weigh about 210 with gear, and I have Stans Flow rims on I9 enduro hubs. I don't remember having this feeling when I rode my Rip9 135x12mm rear with Flows on CK hubs, but maybe I wasn't riding as hard.

    So could this actually be the rims flexing, or is it something with the frame? I would love to try some carbon rims to see if the feeling goes away, because it is kind of unnerving feeling that when bombing down something in the 20-30 MPH range.

    Thanks for any info - BS

  2. #2
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    G'day!

    I had a similar problem on my first WFO. I am pretty sure that it was the wheel flexing, at least in one direction. With the narrow rear hub (135 or 142 mm, same thing) the spoke bracing angle on the drive side was < 4 degrees! I went to the 150mm rear and the problem went away.

    More recently I built a T29, again with the 135mm rear (why oh why do I repeat known mistakes?). Same problem, plus I was stretching the spokes every ride. I don't know of any wide hub options, well, maybe a Rohloff, but that will have to wait. I solved this one by running the wheel dishless, with an offset centerline. The hub is still too narrow, but at least the bracing angles are balanced, and the wheel is reasonably stiff. Unfortunately I have to run a narrower tire back there in this configuration. A rim with an offset spoke bed would help.

    Another option is a SS rear hub with a cut down cassette. I already run out of gears, so I don't know if I would like that.

    gerG
    ...uphill uphill uphill DOWNHILL! uphill uphill uphill uphill DOWNHILL! uphill ...

  3. #3
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    g3rG,

    Thanks for the knowledge. I will have to make sure that I feel it both directions now, as maybe it was always the same left to right or right to left that made it feel strange. I was sad to see that my 142 hub was just a 135 with some spacers. Come on I9 step up on that.

    But you are saying it is more of the spokes flexing, because there isn't enough lateral support from the hub because the spokes are getting pretty close to vertical. This is what I was afraid of, and I asked the Niner customer service guy his advice between the 135/142 rear vs the 150. And he basically said that only if you are riding extensive DH will I ever notice the benefits of the 150. Well damn, here I am riding smooth flow singletrack and am noticing it. I couldn't image what it would be like if I was really ripping something hard with any type of lateral perturbation thrown into it.

    And I like your solution, but I ride alot of climbs that are long and sometimes steep, and I still love my high gears for bombing down stuff, so I can't loose anything. But I do have a Rohloff, but I swore I would never ride that again. I had 5 good years and probably 10,000 miles on it, and at the time I thought it was the greatest thing ever. But I have been enlightened, unless it was going to be a DH only bike.

    Thanks again - BS

  4. #4
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    BullSCit, how many spokes and what lacing are you running on your rear flow?
    I'm running 36 3 cross on flows with Brontrager fr3s with the 142x12 and haven't noticed any flex in the back like you are talking about (which totally could be riding style/terrain but figured I would try to help).

  5. #5
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    I do tend to get a bit rowdy in the turns. If I get everything right, the bike is leaned way over, I am above the bike, and I sort of jump on it at the apex to gain some grip. If I get it wrong I am laying on the ground in a dust cloud wondering why everything hurts even through body armor. Anyway with the flex in the WFO I was actually rubbing treads on the seatstays in the turns. It made a frightening noise. That was with Kodiak tires.

    BS, why did you give up on the Rohloff?

    gerG
    ...uphill uphill uphill DOWNHILL! uphill uphill uphill uphill DOWNHILL! uphill ...

  6. #6
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    I cannot stand bike flex and really notice it.

    Not had a single problem with my WFO 150. The first gen RIP was awful for rear end flop, one of the worst ever. Scrub that, undeniably the worst ever.

    No issues with the current frame though, hence why I like it so much =-)

    Running 36 spoke 4x with massive spoke tension (off the park tools scale).
    Why would I care about 150g of bike weight, I just ate 400g of cookies while reading this?

  7. #7
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    I think the fact that you have banked turns will really bring any flex to the surface. I have a 150mm rear on my WFO with I9s and Stans Flows. They tend to be ok most of the time. I do notice when I switch back and forth between my all mountain 26" bikes, I notice the 29er is not as stiff. Throw in a nice banked turn that will load the wheels and suspension, is where I really notice the flex. I'm 230+ geared up.

    -Sp

    Quote Originally Posted by BullSCit View Post
    I got a new 2012 WFO a month ago, and have been loving it for everything, especially with the addition of a Pushed RC3 on back. It rides the chunk, it rides the smooth, it rides it all with so little effort. And I am just amazed by how well it pedals for a 140mm rear bike. I definitely believe in the CVA suspension, and will be rocking this bike on a 74 mile 14,000 feet elevation race later this summer.

    But there is one area that I am not that excited about the bike, but not sure if it is the frame's fault. I live in Park City, and the trails here are really flowy, with lots of big banked switchbacks and lots of quick left to right bermed turns. I can really attack these and feel pretty confident on this bike, but there seems to be a decent amount of flex in the rear. I thought at first it was the tire pressure, as I live to ride my tubeless 2.4 Ardents kind of low (22-24 psi), but I aired them up to around 29, and I get the same feeling when I quickly change from loading the rear from the left back to the right and vice-versa. I have the 142x12mm thru axle rear, which I thought would be plenty stiff, as I weigh about 210 with gear, and I have Stans Flow rims on I9 enduro hubs. I don't remember having this feeling when I rode my Rip9 135x12mm rear with Flows on CK hubs, but maybe I wasn't riding as hard.

    So could this actually be the rims flexing, or is it something with the frame? I would love to try some carbon rims to see if the feeling goes away, because it is kind of unnerving feeling that when bombing down something in the 20-30 MPH range.

    Thanks for any info - BS

  8. #8
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    We the people ...

    Yep, unfortunatley it's likely a 150mm rear end issue - as in you need one to fully 'solve' this issue.

    I ummed and ahhed for a while before order my WFO about whether to go a 150mm rear end (which meant the extra $$$ of a new wheelset) and am glad I did.

    That said, there's some options avaialable to you - as already noted you can go an SS rear wheel with 6 gears (I've been running this set up or a few years on my hardtails now) or up your spoke count/rim stifness.

    I'm currently in the market for a AM 29er hard tail (i.e. a Kone Honzo or similar) and the one thing that's is bugging me is that I want a full rear cassette and a stiff rear wheel.

    When will the manufacturers realize we need more 150mm hardtails...

  9. #9
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    36h Hadley single speed hub on flows is pretty stiff and works with 6 gears.

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