Stem length

[lulubel]

I was just reading a thread about frame sizes and stem lengths, and someone said putting a shorter stem on a bike will make it steer "too quickly".

Can someone explain this to me.

I've got a small framed man's bike which is my trainer bike that has a long stem, and my main women's bike that has a much shorter stem (half the length of the other one, if that). Is there something different about men's bikes that means a short stem makes them difficult to steer?

 

[Deleted member 1258]

Having arms that are short for my leg length I've nearly always had bikes with short stems, normally between 80 and 90mm, and have found stem length makes no difference, my kilmeston came with a 110mm stem and I swopped it for 90mm stem and the bike is no different on the shorter stem, but there is a school of thought that recons short stems make a bike twitchy.

 

[xpc316e]

I think that the comment arises from this: if the stem were a couple of metres long, the handlebars would have to swing through quite a wide arc to make the front wheel turn a small amount. It's called the tiller effect - imagine how far your hand moves when holding the end of a boat's tiller to make the rudder turn a few degrees. Therefore, the logical extrapolation of this fact is that shorter stems 'quicken' the steering. They definitely reduce the tiller effect, but I am unsure whether they speed up the steering much. Once you're up to any reasonable speed steering isn't done by turning the bars much anyway.

 

[fossyant]

You ideally need to make both bikes as similar as possible.

The reasons for a longer stem (say on a normal bike vs a womens specific model) is down to body shape and size. PS I didn't say mans bike as they aren't marketed as that - the women specific ones actually take into account the different body size of women from men.

I can't really tell the difference in steering. Smallest on a road bike I've had was 100mm but I use 120-130mm these days.

 

[lulubel]

OK, thanks. So most people don't think it makes a noticeable difference, then.

I'll probably get around to putting a shorter stem on the trainer bike at some point because the reach is a bit long for me (probably when I need to buy something else to get free shipping on Wiggle!), but it isn't really bothering me. It doesn't get used very often, or for very long, and when I do use it I just tend to keep my hands on the flat part of the bars more since I don't need to reach the brakes.

 

[Rob3rt]

It makes a noticable difference if you go from very short say 60 or 80mm to 130-140mm. But small variations of 10-20mm not very noticable. A longer stem will put more weight over the front wheel by pushing you further forward over the front hub, shorter stems obviously shift the weight back.

Short stems typically feel quite twitchy, extremelly long stems feel a bit sluggish.

 

[Angelfishsolo]

It makes a noticable difference if you go from very short say 60 or 80mm to 130-140mm. But small variations of 10-20mm not very noticable. A longer stem will put more weight over the front wheel by pushing you further forward over the front hub, shorter stems obviously shift the weight back.

Short stems typically feel quite twitchy, extremelly long stems feel a bit sluggish.

What he said ^^^^^^^^^^^^^^^^^^^

 

[albion]

Going from an undersized 100 I went to 120mm.I certainly perceive it to be less twitchy, though of course I'm much less hunched up on what was to be a cheap 2nd bike.

 

[Cyclist33]

I went from a 100mm to a 90mm and also the angle of rise on the shorter stem was larger than on the longer stem. Overall in term of steering I can't tell the difference but it is much more comfortable. They say a cm can make all the difference and this certainly works for me.

On the downside, I noticed immediately that when chugging up certain (short) inclines, with the 90mm stem I had far less front control and the bike would "lift off" as I climbed. Didn't like that so much but overall the trade off was worth it.

Stu

 

[lulubel]

Interesting. I've just checked the stem length on the bike I ride on the roads. It's 75mm (marked on it, not my measuring).

I suppose, if I rode a bike with a longer stem, I'd probably find the steering sluggish by comparison

 

[Cubist]

It doesn't make much difference on a road bike, esp one with drops, as you are still levering in front of the stem, and steering movements are not all that precise.

On a MTB though you can notice quite a difference, especially if you are riding tight technical turns. I changed from a 110 to a 60mm stem and noticed the bike became quite twitchy on tight turns. Wider bars then went on to make the steering a bit more predictable. I tried the two stems back to back and ended up with the wider bars on an 80mm stem. What you also need to remember is that a shorter cockpit on the same frame will affect where your weight sits in relation to your hub, and that in itself will affect steering.

 

[GrasB]

With road bikes generally they're happy between 90mm & 130mm, go longer or shorter than that & you can have 'interesting' steering reactions depending on the exact geometry & fit of the bike. That said 70mm & 150mm should only cause problems with very aggressive or relaxed steering setups.