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PostPosted: Sun Jan 20, 2013 11:56 am 
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I work as a tour guide, so am on road bikes ad nauseam. To help rekindle my love for cycling, I'm getting back to my MTB routes and am looking to purchase a new 29er HT.

It has been about 5 seasons since I raced off-road, but I always preferred a smaller bike. I am 1.92m (6'4"), but I never seem that tall. I realize that last statement is weird, but I pedal with my heels down, so run a very low saddle, with a lot of setback too (as I must accommodate femurs and 'full-length' feet into my pedalling position - see 2nd photo). My only off-road bike for the last few years has been a Cannondale Bad Boy, in size L (20"), on which I run a 140mm stem at +5deg - as pictured below.

ImageImage

My position over the pedals and my reach to the bars both feel right on this bike, and mimic what I had been racing previously, but there is no denying the fact that I am stretching it a fair bit.

Looking at the spec of 'modern' bikes, it seems the stem lengths have gotten shorter - especially on 29ers. As an example, if I wanted to maintain my current position on a Specialized Stumpjumper HT, I would end up with the following two options:
Image
I would certainly prefer to avoid the use of a -17deg stem, and I'm concerned that the longer FC & wheelbase of the 21.5" frame would feel more sluggish and not allow me to flick the bike as I'm used to... these are the same sensations that I disliked previous larger 26" frames too. I suppose the flip-side of that is that I'm curious if running a 135mm (or most likely 140mm, as I'm aware that 135 doesn't really exist), would 'mess up' the intention of the geometry, if such a notion exists.

For context, I'll be riding/racing this bike on mostly fast, dry terrain, with some technical rocky bits.

So I guess my request is to have some feedback on stems & wheelbase from more experienced 29er riders, especially XC racers, and have some opinions on the two set-up options shown above.


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Posted: Sun Jan 20, 2013 11:56 am 


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PostPosted: Sun Jan 20, 2013 12:59 pm 
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Some may disagree with me but you are not comparing apples to apples. Your position on a 29er is going to be different than on a 26" wheeled bike. On my 29er I'm much more upright for proper balance. I would work with a shop or a fitter to get the correct set up.

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PostPosted: Sun Jan 20, 2013 6:01 pm 
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What relevance is a -17 stem here? Both Stumpy's have a shorter head tube than the BB so shouldn't need a -17 deg stem.

An overlong stem compensates for a too short top tube, so just get the right sized frame, your overlong stem's will slow the steering a lot, especially on a 29er and killing that flickability you want stone dead.

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PostPosted: Sun Jan 20, 2013 8:30 pm 
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"Modern" MTBs shouldn't have a stem more than 100mm.

Unless you're just riding two-track, that is. Wide bars and 80-90mm stems are the hot ticket, and for good reason.


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PostPosted: Sun Jan 20, 2013 9:04 pm 
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Rookie - check the stack measurements and you'll see why the the -17deg stem was needed if I'm to maintain the same position. HT length isn't reliable for comparison when the wheels/forks are different sizes.

Juanmoretime wrote:
Your position on a 29er is going to be different than on a 26" wheeled bike. On my 29er I'm much more upright for proper balance.

LeDuke wrote:
Wide bars and 80-90mm stems are the hot ticket, and for good reason.

Thanks guys, I understand that this is the way things have gone - more upright position and short stems/wide bars - but I guess I'm hoping one of you can explain what that 'good reason' is.

I can see the reasoning behind a wider bar for the bigger wheel, but I always understood that a longer front centre would add weight to the front end (or at least the feeling of weight when riding, such that manuals, etc seem harder) and that would make the bike feel more stable and even sluggish.

Is that wrong? If so, why and if not, then what other gain from a shorter stem is worthy enough to compensate for this concession?


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PostPosted: Mon Jan 21, 2013 12:47 am 
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LeDuke wrote:
"Modern" MTBs shouldn't have a stem more than 100mm.


Uh oh. I am 5'9" and ride a medium Scott scale. Got myself fitted at time of purchase and they swapped the 80mm or 90mm??? Stem for a 120.
Feels good to me. I don't think I would have wanted or needed a large frame.

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PostPosted: Mon Jan 21, 2013 5:06 am 
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To answer both of those statements:

A wider bar with a shorter stem will put you in the exact same position, but yield better control of the bike. Your body will be in the same angle as before, but with more leverage on the bars. Your hands are wider instead of further forward.

I was skeptical as well, until I tried a 700mm bar after riding with a WC pro. It's like cheating on the downhills. And, with the direction that many MTB races are headed, you'd better be quick on the uphills as well as the downs in order to be remotely competitive.

Hell, look at WC bikes, too. Those guys are pretty hesitant to change, but you'll see plenty of 640mm-700mm bars out there these days, and stems to match. The days of 520mm bars are over.


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PostPosted: Tue Jan 22, 2013 4:54 am 
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Thanks LeDuke,

I'm starting to understand the idea here, but I always thought the increased sweep of the wider bars was intended to account for the slightly reduced reach. Afterall, if I hold my fists straight out infront of me, perhaps 50cm apart, and then move them 10cm each, so 70cm total, they certainly have not moved 'back' by 20cm or more.

Did any of your WC friends bring their bars closer to their shoulders (either higher or shorter), when they switched to the 700mm size?


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PostPosted: Wed Jan 23, 2013 10:53 pm 
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The trend is to lengthen the wheelbase which gives more stability, that means longer top tubes and shorter stems.

A bigger frame won't affect your saddle position, it'll just have less seatpost showing, and allow a short stem.

Wide bars just give more leverage.


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PostPosted: Sun Feb 03, 2013 10:34 am 
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IMO most of the short stem 'thing' boils down to toe overlap. To help reduce the problem on 29ers with much larger volume tyres compared with XC bikes from say, 15 years ago, top tubes get much longer. This means plebs with upright riding positions use short stems so they aren't too stretched out.

I don't really agree with much of what LeDuke is saying. Sure you don't see too many pros with huge stems any more but lots still run 120mm-ish stems. They are comfortable riding with a long, low and narrow position. Negative angle stems are probably getting used more than ever too thanks to riders trying to get the front end nice and low on 29ers with tall head tubes and 100mm or even 120mm forks. Most pros still seem to run bars well under 700mm wide.


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PostPosted: Mon Feb 04, 2013 7:37 pm 
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Hallo,

probably it is wise to go to an experienced frame builder and speak to him to build a bike that has everything you need. Steel is an excellent material and if you are not to much looking for a scale it can help to realise a good price for a unique and excellent fitting bike.

A have done it this way and it helped me a lot.

Hope you will find your luck.

Kind Regards

Matthias


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PostPosted: Mon Feb 11, 2013 4:53 am 
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Bst advice I could give you, ride the bike then decide on the stem. When I built my 29 I was having a stem made as well. Before we made the stem I did a few rides and changed the stem a couple of times until I felt really god on the bike. Once it felt right we built the stem. I went down to a 100mm and 0 degree, original idea was 110mm and +5 degree. I still might get another stem made and go down to a -5 or 10 degree, even with short HT I feel a little high sometimes.


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PostPosted: Mon Feb 11, 2013 6:21 pm 
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Thanks for all the suggestions guys - it's becoming more and more apparent that the idea of just maintaining position and ordering a bike to be ready for when I get home may not be pratical. It seems that I'll need at least some time on the bikes, both large and hopefully XL, to decide which one is right for me, which sucks, as that isn't likely to happen until the 2014 season, and then I'd still have to order the bike I want and hope it's not sold out by that point. Which brings me back to this conversation...

While I appreciate that talking to an experienced builder and going custom is an option for some, it is not an interesting one for me. I spend a lot of time on uber-light, snappy-as-hell race bikes, and I don't want my new mtb to be anything less. Most of my riding is on fast, dry trails (rocky, dirty or otherwise), and this type of bike suits my use and ambitions.

I am talll, so have no concerns at all with toe overlap. I get that wide bars increase leverage and therefore ease of control, so that's fine too. But I also understand that a longer wheelbase makes a bike less agile and harder to manual, and that is a ride quality that I'm not interested in. I'm willing to sacrifice an amount of stability for increased agility - within reason.

So while the original question remains: "to have some feedback on stems & wheelbase from more experienced 29er riders, especially XC racers, and have some opinions on the two set-up options shown above", perhaps then it's easier to ask: "Given that I'm interested in a racy, agile frame, can anyone see a valid reason not to go with the 19.5" frame?"

Yes, I will still probably try to ride both, but it's just nice to have all the ideas first.


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PostPosted: Thu Feb 14, 2013 10:41 pm 
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js wrote:
"Given that I'm interested in a racy, agile frame, can anyone see a valid reason not to go with the 19.5" frame?"

Yes, I will still probably try to ride both, but it's just nice to have all the ideas first.



I don't have a 29er (yet :roll: ) ut am 6 ft 1 and ride 19 in frames. Assuming the manufactureres know what they are doing and fit components accordingly, judging by the amount of seatpost I have epxosed, I am ont the limit of 19 in frames. I did ride a 17 in frame for a good number of years and it was fine - it was a rigid frame and forks that I sold last year as old age caught uo with me and it was killing my lower back - too much leaning over.

.... so doing the equivalent sums, you should be just about ok on a 19.5 inch frame - you can make some adjustment in seat post offset and stem length.

.... but I'd still recommend you try the 19,5 and 21 inch frames.


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PostPosted: Sat Feb 16, 2013 2:24 am 
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Buddy !(;
Im 6.3 ft and most my length is my legs 93 cm inseam.roughly from center bb to top sadle is 84 centimeters
I looked at you cdale photo and by looking at it i cant imagine you loving climbing in granny gear !your seat looks like its right above your rear hub.

My last bike before i bought a superfly was an interlock frame 63/64 cm tt out o the top of my head.
When i picked up my superfly in 21 inch i rode it a few times and mounted a 120 stem on the headtube and left it there ever since.i also chanced the inline post to a setback post, so its fair to stay a stretched a bitt more both ways

Wether or not you want a 26r or 29r it seems that most of you wight is on the rear wheel were i strongly sugest you move that forward, but you dont want o run a 130+ stem.
When i bought my supafly i knew what t.t suited me and i ordered with out riding it, no one seems to have an kind of floorstock outside 17/19" bikes. I worked a shops for years and his would have been my zillioned frame/bike, in you case i would go try to test ride a bike ask a buddy who might have one or hire a bike if you can, i dare say you dont need custom, you just need the right size!(;
If you happend to be in w.a. Aus you should cone and ride mine.
I wouldnt wanne say the big wheels or bike is sluggish because i truly cant say it is, its not a bmx but people make it sound that 29er are ocean linners ! Wer this bike excels for me is climbing, because the chainstay's are longer i no longer pop wheelies going up hill in the smaller gears. My weight used to be centerd over the rear hub wich isnt anymore, frontwheel stays on the ground.

Keeps us posted and good luck


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Posted: Sat Feb 16, 2013 2:24 am 


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