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nocturnal oblivion
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Discussion Starter · #1 ·
Hoping someone could explain the reason for flat bars & low stem height on 29ers. Given that the rear is 29, the bike should be proportionally the same height front and rear. So why the need to lower the front?
Anyways, now have my Intense 5.5 and...a full rigid Niner SIR. Maiden ride was beautiful, but I'm going to experiment with a shorter 90mm stem, move some spacers up top and maybe a wider bar? Currently 27" flat-bar with 120mm stem. I'm 5'10" on a medium. A 90 mm will give the same seat to bar length as on my Intense full sus.
But why a relatively lower front?
Thanks, and why didn't I try a 29er earlier?
 

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The BB and saddle heights are about the same 26 vs. 29, but the fork crown, and therefore, bottom of the head tube, is higher to clear the larger wheel. So, for the equivalent frame size, the 29er will typically have a shorter head tube, and (in smaller sizes, especially) may need an inverted stem and flat bar, to bring the grips back down.

I don't know why you didn't try 29 earlier, but maybe in the course of time you'll realize that both of your current bikes are seriously compromised, and move on up to a 29er fully. :thumbsup:
 

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Premium Member
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48,238 Posts
stumblemumble said:
Hoping someone could explain the reason for flat bars & low stem height on 29ers. Given that the rear is 29, the bike should be proportionally the same height front and rear. So why the need to lower the front?
Anyways, now have my Intense 5.5 and...a full rigid Niner SIR. Maiden ride was beautiful, but I'm going to experiment with a shorter 90mm stem, move some spacers up top and maybe a wider bar? Currently 27" flat-bar with 120mm stem. I'm 5'10" on a medium. A 90 mm will give the same seat to bar length as on my Intense full sus.
But why a relatively lower front?
Thanks, and why didn't I try a 29er earlier?
No, they are relatively the same. If you were comparing 26 and 29 bikes with similar travel the answer would be obvious.

Given forks with the same travel, a 29er will have a higher head tube, likely the top as well as the bottom. To the set the grips at the same height relative to the saddle the stem/bars need to have less rise.

In your case, the 5.5 and SIR9 may have the top of the HT at similar levels and you would use similar bars/stem.
 

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Derailleurless
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9,122 Posts
ftajiri said:
one question.. and about the angles of headset and seattube? how to choice the best? the attack angles of 26 are different of 29er...
This question should be asked as a new post because it's not on topic with the original poster's question, but if you search MTBR (or even Google) for "29er trail offset" you'll come up with a whole slew of responses explaining:
- How increasing wheel diameter affects trail
- How steepening the head tube angle can counter that increase
- How fork rake (offset) can counter that increase
- The pros and cons of each.
- How too much or too little trail can affect handling, and what ideal trail might be

Seat tube angle is again a whole nother topic, and for off-the-shelf frames relates mostly to where your saddle ends up in relation to the bottom bracket.

Get ready for some deep and possibly enlightening reading.
 
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