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  1. #1
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    XC bike in the chunk (x-post from Surly)

    I have been enjoying my Karate Monkey for a long time now, but it is letting me down on some of the gnarlier trails I have been riding lately. I rode some of the rowdier parts of Austin's Greenbelt (such as
    , Cheese Grater, etc) the other night and had my monkey butt handed to me. I managed to stay upright but had lots of white-knuckled "ohsh!tgonnadie" moments. I want to ride more of that kind of stuff but the bike feels very, very unstable in the chunk. The front end drifts a lot on steep climbs and sometimes the rear tire loses grip at the worst possible time. The fork dives frighteningly hard during descents even after I stiffened it up a lot by adding oil to the air chamber at Manitou's recommendation (used to be much worse, several bad endoes).

    I am 5'9" and 155# + riding gear.
    16" 2013 KM
    80mm Manitou Tower Pro fork
    28" flat bars angled slightly up (this is as wide as I can stand them) 100mm stem with a few spacers
    32/1x9 drivertrain with Monkey Nuts to lengthen the back end a bit ( can run the axle "slammed" but it tends to loop out too easily on steep stuff)
    2.25 Maxxis Ikons on a Crest front, Arch EX rear at 25 psi

    What can I change to make this handle better in the chunk? A longer fork is probably not in the budget, but if I am going to spend that kind of money, I will start looking at new bikes rather than trying to make this one do something that it is not made to do. Realistically, an aggressive FS bike with a dropper post would be ideal for this terrain, but a $4K+ bike is not happening any time soon.

    Shorter stem? Lower saddle? Fatter tires? Raise bars? I can experiment but I need some ideas. I have a 2.4 Ardent that will go back on my front wheel for my next ride. Other than that, I would need to find a shorter stem.
    Last edited by mack_turtle; 06-21-2014 at 09:24 PM.

  2. #2
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    Απ: XC bike in the chunk (x-post from Surly)

    You allready said that you don'want wider bars, but the truth is they are a lot of help in the situation you describe. The increased leverage helps you resist bouncing left and right on rocks etc. Rise may help,but if your bars arw morw tahn a couple cem's higher than your saddle you may compromise front wheel traction.
    A slightly shorter stem can make downhills more controllable, try a couple of cm's shorter for starters.
    Low tire pressure is another key way to reduce bumping and increase control, but at 25 psi you are already on the right track.
    Saddle down for descents always helps too, a dropper is ideal if you can afford one and don't mind the hassle of maintenance.
    Most important regardless of bike and comoonents is to stay loose and flexible.Your arms and legs are the most capable suspension you'll ever find.

  3. #3
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    How about a 120mm fork, still Tower Pro, but 15mm and a wide rim wheelset. LB 30mm inside or Wide Lightnings. I'm using them.
    Here's a bike with them.
    Pivot Les: Final Review (The Trail Perspective)

  4. #4
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    a longer fork really would make a pretty huge difference handling more challenging terrain. It will shift your weight balance and it will improve the stability of the bike due to the longer wheelbase and the slacker HT.

    The other changes will help, also, but not nearly as large with one change.

  5. #5
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    Damn, I just bought this fork a year ago after months of pinching pennies. I think 120 sounds extreme for the geo of the Karate Monkey, but if i can score a 100mm fork, that might be worthwhile. A fork with a non-tapered steerer and one that does not require buying a new wheel to accommodate a thru axle is getting difficult. If i have to make changes much more drastic than that, i might be looking at a new bike.

  6. #6
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    The geometry of the KM is based on a 468mm fork. A 120mm Marvel is 530 and sagged 25% is about 500mm. That will slacken out the front about 2-2.5 degrees. This is a good thing if you are looking for descending stability. The added offset will help shorten the trail which should bring the steering back to a more neutral feel. Really, 69-70 degree head angle isn't too steep in my opinion even on a 29er. I generally like the slightly more stable steering even for XC duty. If i could, i would've got a 120 fork instead of my 100 just for that.

    If that doesn't sound good to you, a new bike is probably in your future and you can keep the KM as the light trail bike. Maybe even SS it.

  7. #7
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    A 50mm stem and 780mm+ bars with a dropper post will make the most dramatic difference short of a new fork. It will be a like a new bike set up that way, and will be much better in the chunk.

  8. #8
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    the more I think about this, the more I am starting to think this is an issue of steering stability. "long" stem + not super-wide bars + short fork = twitchy front end? I think I will start with a shorter stem and maybe some slightly wider bars. mine started at 720 and they felt ridiculous. I felt like this poor fellow, but maybe the smaller stem will help-

    XC bike in the chunk (x-post from Surly)-super-wide-bar.jpg

    how short a stem would be appropriate for a start? I have a 100mm now and I could go 80, 70, or even 60 mm. On-One has some killer prices so I want to start there: On-One stem $40. I could go a little wider on the bars but I will start with the stem and see how that goes. a longer fork will come later when I convince the wife that I need to spend that money. what's the winter forecast looking like in Hell for the next few years?

  9. #9
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    Go straight to a 60mm

  10. #10
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    I am running 28" (710mm) bars w/ 100mm stem on my Nimble9. In my case, head angle makes all the diff., so a slightly longer fork might help you, but it might screw up your low speed handling and make wandering on climbs worse. My N9 does not wander at all, due to steering geo.

    If I am trying to go fast in chunk, it feels to me that light wheels (like Crests) are too light. Sure, if the wheel is too heavy it feels like it bogs you down, so there is a happy medium. My old wheels were 1650g. When they finally wore out I bumped up to 1700g wheels and they feel more stable, without bogging things down. Maybe borrow a heavier and wider (but still good quality) wheel for the front to see how it feels. Add a chunkier tire to increase the effect.

    -F
    It's never easier - you just go faster.

  11. #11
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    The longer fork will make the front end wander more on the steep climbs. As for the front end dive... I think that is due to where you CG is when you riding. I think you may have too much weight up front. I am similar weight and run my 100mm fork soft. The front end dives, but never so much as to be a concern. I just basically let it drop and keep my weight centered. So as the terrain gets steeper I get farther back, but really only stay level and balanced. I am letting the bike move under me, but staying low. On the climbs I will sit on the tip of the saddle for max rear grip and front grip. Sometimes I will short stand where I my butt is 1" off the saddle, but I move my weight forward or back to get just the right balance.
    Joe
    2003 KHS Alite 4000 26" Hardtail - XC, All mountain, blah blah blah.. I just ride.

  12. #12
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    Quote Originally Posted by mack_turtle View Post
    I have been enjoying my Karate Monkey for a long time now, but it is letting me down on some of the gnarlier trails I have been riding lately. I rode some of the rowdier parts of Austin's Greenbelt (such as
    , Cheese Grater, etc) the other night and had my monkey butt handed to me. I managed to stay upright but had lots of white-knuckled "ohsh!tgonnadie" moments. I want to ride more of that kind of stuff but the bike feels very, very unstable in the chunk. The front end drifts a lot on steep climbs and sometimes the rear tire loses grip at the worst possible time. The fork dives frighteningly hard during descents even after I stiffened it up a lot by adding oil to the air chamber at Manitou's recommendation (used to be much worse, several bad endoes).

    I am 5'9" and 155# + riding gear.
    16" 2013 KM
    80mm Manitou Tower Pro fork
    28" flat bars angled slightly up (this is as wide as I can stand them) 100mm stem with a few spacers
    32/1x9 drivertrain with Monkey Nuts to lengthen the back end a bit ( can run the axle "slammed" but it tends to loop out too easily on steep stuff)
    2.25 Maxxis Ikons on a Crest front, Arch EX rear at 25 psi

    What can I change to make this handle better in the chunk? A longer fork is probably not in the budget, but if I am going to spend that kind of money, I will start looking at new bikes rather than trying to make this one do something that it is not made to do. Realistically, an aggressive FS bike with a dropper post would be ideal for this terrain, but a $4K+ bike is not happening any time soon.

    Shorter stem? Lower saddle? Fatter tires? Raise bars? I can experiment but I need some ideas. I have a 2.4 Ardent that will go back on my front wheel for my next ride. Other than that, I would need to find a shorter stem.
    ikons are doable in the greenbelt, but you need to be a pretty good rider. If you are not getting good traction, something like a hans dampf in front with the ardent in back would make you feel a lot more secure. I weigh 175 and run at 20 psi front and rear so your pressure is probably too high for your weight. Going over cheese grater, the lower pressure will help a lot.

    Probably not possible but a 120mm fork would help a lot. It would slacken the head tube angle making descending a lot better.

    A wandering front end is most likely bad technique. Get the nose of your saddle in your butt crack.

  13. #13
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    Quote Originally Posted by Fleas View Post
    I am running 28" (710mm) bars w/ 100mm stem on my Nimble9. In my case, head angle makes all the diff., so a slightly longer fork might help you, but it might screw up your low speed handling and make wandering on climbs worse. My N9 does not wander at all, due to steering geo.
    After another (mellower) ride, I have concluded that that is my main complaint that does not have an easy solution. Fatter tires, lower pressure, loosen up, work on technique, etc- easy.

    However, what kills me is the wandering (edit: make that over-steering, as "wandering" is not my problem at all) front end at low speeds. I would love to be able to cherry-pick my way through the maze of rocks but the front end over-steers so easily that I can't get the tire to to right where I want it, sending me into the rock I am trying to avoid rather than around it. The affect is amplified at speed, hence my terror of downhill sections that i so frequently walk, or just huck and hope I stay upright. I guess you could say my steering is "twitchy." 71d head angle, 80 mm fork, 28" low bars, 100 mm stem- that could end up feeling twitchy right?

    A new fork is not in the budget right now, but a stem and/bars could happen. I was thinking 60 mm stem and bars in 740 mm or so that could be cut down at little.

    The other question is handlebar height. The frame is pretty short in the TT, so I am a little worried about the short stem making it feel too short, but that may be negated by the wider bars. What affect would higher or lower bars have on that?
    Last edited by mack_turtle; 06-23-2014 at 03:08 PM.

  14. #14
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    Wandering at low speed climbing and then oversteering are two completely opposite effects.

    Wandering is caused by slack angles and not enough weight on the front. Twicty steering is caused by steep head angles and too much weight up front. I can't see how you can have both probelms at the same time unless is 90% technique related.

    I run a 100 mm fork on bike that was probably best suited for 80 mm. What this does it brings up the front end making it wander on climbs. To counter this have lowered the front bars as much as possible the keep the front end down. I am using a 100mm stem with 660 mm bars. (I had 120mm step with 585 bars) The wider bars reduce the impact of rocks knocking the front wheel off target both on climbs and descents. However it requires MORE steering input around turns. This not a bad thing, but does take some feel. The shorter the stem the less weight on the front and the faster the steering. This is why people don't run wide bars with old 130mm stems. The shorter stem counters some of slower steering of the wide bars. With my change the (shorter stem and wider bars) I was able to keep a very similar reach.
    Joe
    2003 KHS Alite 4000 26" Hardtail - XC, All mountain, blah blah blah.. I just ride.

  15. #15
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    Quote Originally Posted by JoePAz View Post
    Wandering at low speed climbing and then oversteering are two completely opposite effects.
    I guess I thought wandering and over-steering were the same thing. I have "twitchy" steering, so I guess that would fit into the over-steering category. thanks for clarifying the parlance of our times.

    I will probably be making a purchase soon:

    first, I already have an unused Ardent 2.4, so that is going back on my front wheel. I have a 2.2 Conti X-King that is more aggressive than the Ikons, so that will go on my rear wheel. I can get a 2.4 Chunky Monkey as well, but I am not sure if that should be a priority.

    second- cockpit! I did some experiments with doing push-ups over a yard stick (nerd alert!) and I can see how getting them from 28" to 30" might help a lot, so I might as well go to a 760 mm El Guapo bar and see how that goes. (they come in 810 mm too, but I will never use something that wide.)

    for my proportions and frame size, is it possible to go too short on the stem? for XC use on a short-ish frame, would 50 mm excessively short? 60 mm stems are out of stock but they have 50 and 70 mm On-One stems.
    Last edited by mack_turtle; 06-23-2014 at 08:33 PM.

  16. #16
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    The X-king and Ikon are similar tires. I just moved from an X-king 2.4 to an Ikon 2.2 in the rear. I was looking for longer life and similar grip.

    I am starting to think alot of this is technique. Again twichy steering and wandering steering a opposite effects. Twicthy means it response too fast and that means you need less weight on front with slacker angles, wider bars. However wandering corrections need MORE weight on the front and steeper angles. Wandering on climbs and twitch descents to me means poor body position on both.

    Think of it this way. Downhill bikes don't climb well since the front end is so raked out (slack) that when climbing you can't keep weight on it and that allows it to wander around. However that same slack angle really helps control the bike on steep and fast stuff. XC race bikes are very steep and have low bars. This keeps weight on front tire when climbing giving the rider control of the front wheel up steep climbs and good power. However on the downhills and turns the steeper angles make the bike faster to respond. Perfect for flat turns, but it can be a handful on steep descents. A bike that has both problems is either set-up very poorly or the rider is not using the proper technique.
    Joe
    2003 KHS Alite 4000 26" Hardtail - XC, All mountain, blah blah blah.. I just ride.

  17. #17
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    So I have "twitchy" handling up front that tends to hinder my ability to hold the line I want at any speed. I need to work on technique and just ride more.

    However, I felt good with a 660 mm bar and a 100 mm stem at one time. Then i went to a 700-710 mm bar and it feels twitchy. So i can compliment my growing skills worh something that better suits my riding style. Shorter stem, wider bar, or both. I can get an excessively wide bar and cut it down but I cannot lengthen a too-short stem. With my previous 100/660 combo, would 50/760 work well, even after i cut down the bar, or should i go for a 70 mm stem? I know this is highly subjective but i don't want to buy four stems until i find the right one.

  18. #18
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    If all felt good with a 660 bar 100 stem then maybe the problem is that the 710 bar right now is not match to the right stem. I used a 585 bar and 120 stem and my handling was good. I moved to a 660 /100 combo and very carefully adjusted my bar location to compensate. I make sure the drop from my set to the bars was the same as with the 585/120 combo, but my reach was shorter. That is required since when you move your arms farther apart you can't reach as far.

    Also my 585 bar was a flat bar, but my 660 is a riser. However by flipping the stem (neg rise now) and playing around with the spacers on steer tube I got the same height. Doing this keep the same front end characteristics going up and down when straight because my body position really did not change at all. What was different is that the wider bars were less likely to be tossed off line both up and down hill. The reason for that is leverage. Wider bars mean less force on the hands to when front wheel hits a rock and gets re-directed. So thus it gives feeling that it is easier to keep the bike point straight. The only downside I had with wider bars was I needed to re-calibrate how much arm movement it took to make a turn. Wider bars require my hands to move farther in space to turn the bike. This effect was very noticeable at first, but I was able to adapt in a couple rides. Right now I have no to plans to go any wider on my bars, but I did I would also use a short stem. I would guess somewhere around 70- 80 mm for 720 bars.
    Joe
    2003 KHS Alite 4000 26" Hardtail - XC, All mountain, blah blah blah.. I just ride.

  19. #19
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    here's the geometry (over)thought experiment I am considering: the 710/100 bar & stem that I have now feels twitchy.

    1. is this because the length of the stem creates an angle such that I don't have enough control over the steering?
    a) if the bar width stays the same, what affect should shortening the stem have on steering?
    b)if the stem length stays the same, what affect should widening the handlebar have on steering?

    2. or does this setup throw off my CoG such that a little body English has too great an affect on steering?
    a) so a wider bar would put more weight over the front of the bike, having what affect on steering?
    b)a shorter stem would put my CoG further back, which would have the affect of...

    short version- thinking about going to a 760mm bar. my stem choices seem to be 50mm or 70mm. or keep the 100mm. which stem? or I could keep the 710 bars and just go shorter on the stem. I think. My head a'splode!

  20. #20
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    Wider bars with a long stem puts more weight on the front of the bike by moving you CG forward slightly. This more forward CG makes the front end more effective and makes you more likely to endo or at least gives you that feeling. Really there is nothing anyone can do verbally to describe the solution to the issue you have. I still don't really know what "twichy" means either. Are you talking climbing, descending, smooth flat turns? "twichy" is ok but where? The talk about the effect of stem and bars only make sense when you put it in context of what parts of the trail you are talking about. Every bike set-up is a compromise to get the right mix of handling traits all around.
    Joe
    2003 KHS Alite 4000 26" Hardtail - XC, All mountain, blah blah blah.. I just ride.

  21. #21
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    For comparison, I used to ride a Niner MCR9 with the Niner steel fork. It had quick steering and I was running 660mm bars with 90mm stem. It had similar characteristics as yours, where it felt stable in everything but chunky downhills. It became a little unsettling as I gained confidence (<< I realize that that is oxymoronic) and pushed the limits.

    I tried a shorter stem (did not like), wider bars (760mm), heavier wheel (I keep heavy duty spares), bigger tire (2.4) but in the end the geometry was what it was. After the MCR broke and I had it repaired, I bought a Canfield Nimble9.

    If you can get a fork with LESS offset, it might help slow your steering with no other changes. If you had 20mm more travel, it probably wouldn't hurt. I realize this is not a cheap option, but consider what you might spend on bars and stems.

    -F
    It's never easier - you just go faster.

  22. #22
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    I am going to try the short stem/ wide bar/ giant tire solution for now. I was thinking about doing that anyways, but it might fall short of ideal.

    I have an 80 mm fork because I previously purchased a Vassago Jabberwocky and Vassago insists that an 80 mm fork is the only way to ride a Jabber and that the bike will explode and you will die if you ride anything longer. so I bought the 80 mm fork and later realized how much I hated the Jabber and went back to a KM. now I am effectively stuck with an 80 mm fork. the bike is certainly rideable like this but I will start looking for a way to get a longer fork. I don't have a lot of spare money for bike parts for various reasons so I tend to make short-term, inexpensive purchases, so a new fork will be a long way off.

  23. #23
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    made a little purchase from Planet X:
    El Guapo Ancho risers, 760mm
    On-One cnc stem, 60mm
    One-One Chunky Monkey tire, 29x2.4
    (already had a 2.4 Ardent so that went back on my bike)





    big bars, short stem, balloon tires feels awesome. it definitely feels like more of a pig with the added weight but I don't mind.

  24. #24
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    IMO I think you went the right way. My geared bike has a 55mm stem, 760mm bars and Chunky Monkeys and although my longer than spec fork slacks out the geometry it climbs just fine as long I pay attention to body position. I had my old 98 Kona Explosif which is now a rigid single-speed with a 50mm stem and 760mm bars out a while back. It felt great. Pretty stable in the chunk and climbed as well as it did with a longer stem and narrower bars.
    I got some bad ideas in my head.

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