I’m looking at buying a xc 29er hardtail frame, to use on 12hr solo races etc.

my question is what do many xc race bikes have short wheel bases, and use long stem.
I’m a fan of the short stem wide bar combo on my trail and AM bike. and wonder why would i not use the same set up for an xc bike?
I.e a 21″ lurcher is 640mm ETT, with a 35mm 50mm stem would that not put me in a good position?
getting a bit confused about it before i buy the frame and yes it is a online frame.

thanks in advance

Presumably to give a better position for climbing and pedalling. Less emphasis is placed on downhill handling characteristics.

replicating road position

ive worked ot that a 21″ lurcher with a 50mm stem will give me the same position as my road bike.
but keep thinking is this a bit odd.

ive worked ot that a 21″ lurcher with a 50mm stem will give me the same position as my road bike.

How have you managed to do that?

ive just measured from my road bike handle bar level across to the seat tube.
thats a 58cm frame. 5mm off

The road bike was brought and set up in a shop.

dirtyrider

Increasingly they don’t – well at least not that long. Over the past few years top tubes have grown a good 25-30mm and stems lost the same amount. Bars have also got a lot wider – again 3 years ago I was on 620mm bars, now 710-730 depending on bike. Depends on the brand though.

Yes check out race bikes from 15 years ago at World Cup level and it’s very much narrow bars, bar ends, long stem. Now stems are shorter and bars wider. Partly due to more technical tracks probably. Maybe a 29er geo thing too possibly?

Still not as short and wide as trail bikes though, but then you want the control that wider bars give and the quick steering you get from a short stem (works better with the slacker angles too). For XC racing you want a bit more stability that you get from less wide bars and a longer stem when you’re putting the power down.

It’s all compromises in the end but it’s worth playing around with different lengths and widths as you’ll probably find a sweet spot.

How much of it is racers riding what their sponsors latest bike is?
I mean, the quick guys would be fine on a shopping bike wouldn’t they??

640mm is quite a long top tube. Probably not long enough to be really lent over with a short stem but pretty good.

I would have thought that for racing it must eventually reach the point where if the bars are to wide aero is compromised.

Oh and my observation at a cyclo cross race. Racers learn to perform amazing feats of handing from compromised positions

Wide bars can get a bit too much in tight twisty forest trails and the stability and control the wider bar brings just doesn’t offset the disadvantage enough.

I also always felt like a slightly steeper head angle was better at tighter corners at pedally speeds (i.e. not full tilt downhill). Slack head angles always felt a bit like chasing a wheel barrow.

So is 50mm considered long these days? Ive got a 140mm stem somewhere, now thats long

To me a 640mm ETT on a XC bike seems massive unless of course you’re about eleventythree feet tall

640mm ETT on my 19.5″ Trek Superfly. Running it with with an 80mm stem and 720mm bars.
I’m 6ft 2 and it feels pretty spot on….

Seat angles

140mm ? I’ve got a 160mm stem in the garage somewhere ! From an ’89 Fisher.

The ETT on my XC bike (RM Element) is the same as my Blur LT. I run a 50mm on the Blur and about 70 on the XC bike with slightly narrower bars. It is more stretched out which is better for long pedals. Might go wider and a little shorter in future.

How much of it is racers riding what their sponsors latest bike is?

Not much. Regardless of the bike I’d expect any rider to chop and change contact points for the rider’s measurements and preference.

Where are these short top tube frames? I’d love to replicate the riding position I had 20 years ago with a carbon 29er, bar ends and everything. (Wife’s Specialized Fate is pretty near perfect, is it OK to ride a girls bike?).

I bought a hard tail xc bike and tried to replicate my enduro bike with short stem and wide bars.

My advice is dont, it ruined it, It took all the pace out of it and made it feel horrible.
I now have a slightly shorter stem with a wide bar.

@pirahna
I’m not sure if it’s ok to ride a gia bike, but I do it anyway. I love my 15″fate!

But what are the advantages to a long stem?
Is it better to go with a 19″ frame and long stem or go with the 21″ and have a 50+mm stem.

It would appear I have shortish legs at 6’2 and long arms. but dont fancy riding a bike with a stem at 100mm plus.

Surely long legs short body and arms, smaller bike and a long seat post

Short legs long body and arms bigger bike and less seat post

question is why have a smaller frame and longer stem? is there an advantage I’m not seeing.

the narrower bars being more comfortable are probably the answer, I wouldn’t want to do 12hrs or more on really wide bars (so the stem goes a little longer to reduce potential twitchiness) ?

A longer stem also helps to put your weight over the front wheel to aid climbing what with the slightly steeper head tube angles found on xc machines

EDIT: all said above.