Please explain long stems??

[Iwan Kemp]

some thinking on the whole stem thing. A shorter stem will make the steering a bit more direct, which is good on bmx, DH and riding over obstacles where things go ugly fast. However, when you are traveling at 40km/hr in a peleton a bit of flow and predictability may be required, no one wants a jittery bike. So it makes sense that long stems will be more prevelant on bikes that go fast in straight lines (with totally insufficient braking systems) and short stems on bikes that navigate over rocks and tight turns. Mtb XC may be the twilight zone in this thesis, where you have the go fast in straight lines interspersed with rocky sections.

 

The second thing is that a longer stem pulls the centre of gravity (CoG) forward on the bike, which may be great (or even irrelevant on a road bike) but can have interesting effects on a Mtb bike. (May improve climbing and cornering and mess up decending).

 

Despite these musings the best is to decide for yourself. May cyclists have a collection of stems and start the season with short stems and as their flexibility improves lengthen the stem and drop the handle bars. I read in Lopez's book on Mtb skills that you need to shorten the stem as you raise the handle bars. This may also explain why cyclists with very aero positions have long stems.

Spot on for road bikes. The way to "combat" the shorter stem would be wider bars but that wouldn't make sense AT ALL on a road bike. So for a road bike it makes perfect sense.

 

I read in Lopez's book on Mtb skills that you need to shorten the stem as you raise the handle bars. This may also explain why cyclists with very aero positions have long stems.

As a general guideline, yes but not as a rule or law. There are lots of contributing factors. Your ass will always be the same distance from the BB assuming you've a proper fitment done and saddle height is where it should be. And obviously excluding extremes like a DH bike. Right, so that stays the same. But the front end of a MTB can be just about anything. Stem stack height, Heat tube length stem rise or fall, handlebar rise, stem length and handlebar sweep can all alter the effective "height". I've heard guys say I always run a 15mm sacer under the stem for correct height. Great if you're always riding the same bike. Take Giant as an example. Their heat tubes used to be seriously long. Same with Turner. To have your bars at the same effective height you need to consider these things.

 

And not a lot of guys who set ups do this.

[DubbelBuys]

Pleasure!

 

 

Can't remeber the exact measurement, but I didn't notice any difference.

 

 

Spot on!

 

Let me add this on "flickability". First you need to be doing dirt, or BMX or FR to really need a flick-able bike. For most of us a bike's that's stable at speed is of much better use and you get that with a longer wheelbase. Not too long though as at some point it will start having a negative effect. From experience: When I bought a Mbuzi I went with a Med to get a nimbler more flick-able bike. What a HUGE mistake. To get the bike to handle like I wanted to I was running a 50mm stem. I was chopping my ass off trying to pedal that thing to the top of anywhere. It was just too cramped and uncomfortable. Going with a longer stem wasn't an option at all as that would sacrifice too much of everything else. The fact that I was riding a smaller more "flick-able" frame also went out the window cause I couldn't get comfortable. So...I sold it. And, like I've said I am now riding a Large frame. And to add more confusion, if however I went with one of the other two on my shortlist, Yeti SB-66 or Whyte 146 I would've gone for a Medium. You see, most manufacturers have learned this and are in process of "up-sizing" their trail and AM bikes. So their Med TT length is comparable to an Ibis' Large.

 

So I won't go around saying I ride a Large bike, I say I ride a 600mm - 615mm TT.

 

I also realised that hard tails tend to have slightly longer top tubes compared to dual sus when compared medium with medium.. (or at least mine does)

 

My medium shova frame is officially for sale then.

 

Will ad soon.

 

J

[Iwan Kemp]

Ok, I just had an Ergo fit with Jeroen Swart, who prescribed a stem length of 95. after a couple of rides I knew this was wrong for my style of riding and quickly replaced the 95 with 60 (740mm bars) - what a differrence! my riding is faster, more fluid, plus I can now transfer my weight around the bike easier to compensate for the short stem when climbing and sit over the back wheel when descending or riding roots etc

 

now I'm not criticising Jeroen as he is definitely a very smart oke, who knows what he's doing and who can defs ride a bit (check his stats on Strava!), however, I think one has to sometimes think beyond the formulas and just feel the ride.

 

here are my Ergofit parameters:

 

 

Frame Sizing :

Effective top tube length : 58.5

Parameters :

Seat height : 74.3

Saddle setback : 6.2

Reach A : 68.6

Reach B : 49.02

Drop : 3.1

Crank length : 175

Stem length : 95

 

Based on what does he calculate saddle setback?

[ramsew]

Based on what does he calculate saddle setback?

i'm assuming these stats:

 

 

Stature : 172.2

Left leg length : 96

Right leg length : 96.4

Left Arm length : 78

Right Arm length : 77.4

Sit and Reach(S+R) : -5

Straight leg raising(SLR) : 76

Shoe size : 43

 

but i'm not entirely sure

Edited January 2, 2013 by ramsew

[Iwan Kemp]

Hmmm. I could be right, but as far as I have it you have to factor in seat tube angle. Saddle setback is there to get you in the correct position over your crank arm, more precisely your pedals spindle, so as not to injure you knees or put unnecessary strain on it and your lower back. You don't adjust saddle for and aft for "reach".

 

So with a slacker seat tube angle you will sit further away from the effective diagonal line drawn vertical to the ground straight through your BB. For and aft is meant to get you back into your ideal position.

Edited January 2, 2013 by The Crow

[patches]

Tell Bradley Wiggins his bike handles like a "drunk Donkey"

 

even Harley Davidsons (the original 2 wheeled drunk donkeys) can go fast in a straight line!

[Tumbleweed]

even Harley Davidsons (the original 2 wheeled drunk donkeys) can go fast in a straight line!

 

Those descents at 95-100km odd at hardly straight…

[patches]

Those descents at 95-100km odd at hardly straight…

 

they're also not on a glacier (like the 90kph decents at Megavalanche), and they're also not exactly switchbacks.

[Tumbleweed]

they're also not on a glacier (like the 90kph decents at Megavalanche), and they're also not exactly switchbacks.

 

The glaciers are not exactly switchbacks either…and you rarely see a roadie putting his foot out to corner…

[nolipoli]

Hmmm. I could be right, but as far as I have it you have to factor in seat tube angle. Saddle setback is there to get you in the correct position over your crank arm, more precisely your pedals spindle, so as not to injure you knees or put unnecessary strain on it and your lower back. You don't adjust saddle for and aft for "reach".

 

So with a slacker seat tube angle you will sit further away from the effective diagonal line drawn vertical to the ground straight through your BB. For and aft is meant to get you back into your ideal position.

 

Just remember that you can't look at this aspect in isolation. A XC bike has a steeper seat tube angle BUT you also tend to ride in a more aggressive äero" position. An AM bike puts your torso more upright, but has a slacker seat tube angle. Getting the correct setup means taking into consideration the angle created between thigh and torso.

 

People that don't fully understand setup will only look at that method of dropping a vertical line from the knee. This may work on a XC bike, but not on an AM bike.

[Iwan Kemp]

even Harley Davidsons (the original 2 wheeled drunk donkeys) can go fast in a straight line!

 

 

My favoutire Ayrton Senna quote was when he was asked how he managed to win a race in his dog of a McLaren (think 92, 93, 94 McLaren!) when the Williams was so much faster and uber dominating.

 

"Anyone can drive fast in a straight line."

[Iwan Kemp]

Just remember that you can't look at this aspect in isolation. A XC bike has a steeper seat tube angle BUT you also tend to ride in a more aggressive äero" position. An AM bike puts your torso more upright, but has a slacker seat tube angle. Getting the correct setup means taking into consideration the angle created between thigh and torso.

 

People that don't fully understand setup will only look at that method of dropping a vertical line from the knee. This may work on a XC bike, but not on an AM bike.

 

True. That's why I said way back that you need a guy who has ridden these type of bikes and have studied what makes them go like they are suppose to. No use going to a guys who's mastered a computer program and basics in human anatomy.

[nolipoli]

For sure.

 

I guess the next step for these computer programs would be to include the bike geometry in the information that gets fed in. This would help to customise the fit to the type of bike (and riding?)

 

I am kind of surpised that it hasn't been done already.

[Iwan Kemp]

Yeah. Does get quite complicated quickly. I've always said that any computer program will only get you there 80%. The rest is down to the human mind and eye to interpret.

[ramsew]

Yeah. Does get quite complicated quickly. I've always said that any computer program will only get you there 80%. The rest is down to the human mind and eye to interpret.

im on a new bike, its gonna take me a few months to get it right of that I'm sure!

[nolipoli]

The thing is that every rider should understand how his own body works on a bike, and should understand the bike too. Otherwise how can you interpret that ache that comes up after 30kms on the trail, but is completely absent in the shop.

 

There is a reason why all the most succesful motor racers (car and bike) are technically savvy. This allows them to give proper feedback to the engineers in pitlane.