Stem Length vs Stability

my opnion is that slightly lighter steering will be noticed, but it won't be enough to adversely effect handling. It's not as if the bike will suddenly have speed wobbles.

snails_pace said:

I am trying to find a road bike for my wife. In the process of fitting her one of the LBS adjusted the stem length to 80mm.

My question is will this negatively affect the bikes handling? I have always had 120mm stems on my bikes and hadn't thought about it before. I have a friend that rides and has a shorter stem (90) and believes that he lost some stability when he went down from a 110.

Should I be concerned or is it no big deal. The bike seems to fit fine otherwise.

Thanks!🙂

I have heard that stem length is really determined by arm length, to get the proper fit on the bike. You're friends loss of stability may be the result of not being stretched out enough.

531Aussie said:

my opnion is that slightly lighter steering will be noticed, but it won't be enough to adversely effect handling. It's not as if the bike will suddenly have speed wobbles.

I ride an 80mm stem with no problems. The leverage is on the handle bars at 20+ cm from the axis of the steering tube, not really the stem for steering. You just have to get used to the quicker steering moment. It is perception not reality...unless you happen to be steering with 20 cm barwidth or less.

I switched from 12 to 10 cm on a bike and there is a difference. With the shorter stem steering is quicker, but after a ride or two you don't notice it anymore.

It will quicken up the steering a bit, but some people are more sensitive to it than others. 80mm seems awfully short though. What kind of frame is it going on?

artmichalek said:

It will quicken up the steering a bit, but some people are more sensitive to it than others. 80mm seems awfully short though. What kind of frame is it going on?

Stability is good on the short stem it is the quickness change that people going from longer to shorter stems that people react to which is a muscle memory and perception issue not one of stability. What ever one is used to.
Know you are asking the originator however, I will give my reason for the short stem: legs longer in proportion to the body than the upper torso so 80mm it is. All my bikes have 80mm stems. Women as a rule have longer legs in proportion to their upper bodies and you see that in many of the lady specific bikes.

I would not put a lady on a shorter stem than 90mm. If the original was 110-120mm, then, clearly, the frame is a size too big.

How tall is she? There are XS road bikes from 40cm up to 51cm with smaller wheels. My GF just bought a Felt F100 47cm 650c and she is 4'10", no changes to the seatpost or stem or bars. However, we will see how she goes with the 165mm cranks, 155 may suit her better. 😎

Thanks for the input. THe bike it is going on is a Bianchi Eros (sice 53). The bike is for my wife and she is 5'7" and her legs are a bit long compared to her torso.

My initial thought was that the bike may be too large, but the 51 was obviously too small. Perhaps we should try other brands. So far she prefers the Bianchi to Giant and Trek but that is all at the same (and prefered LBS).

Here locally about the only other choice is Specialized and maybe Lemond.

Thanks again for the input.

Deanster04 said:

Stability is good on the short stem it is the quickness change that people going from longer to shorter stems that people react to which is a muscle memory and perception issue not one of stability. What ever one is used to.
Know you are asking the originator however, I will give my reason for the short stem: legs longer in proportion to the body than the upper torso so 80mm it is. All my bikes have 80mm stems. Women as a rule have longer legs in proportion to their upper bodies and you see that in many of the lady specific bikes.

I understand you perfectly as I have exactly the same "problem".
In order to use a 120 or 130 mm stem I should use a frame with a seat tube at least 4 cm too short.
I find it very difficult to achieve a good position when you have very long legs and short torso. Me, at least, I still haven't found the perfect solution so far.

snails_pace said:

Thanks for the input. THe bike it is going on is a Bianchi Eros (sice 53). The bike is for my wife and she is 5'7" and her legs are a bit long compared to her torso.

My initial thought was that the bike may be too large, but the 51 was obviously too small. Perhaps we should try other brands. So far she prefers the Bianchi to Giant and Trek but that is all at the same (and prefered LBS).

Here locally about the only other choice is Specialized and maybe Lemond.

Thanks again for the input.

By the way, what is a "standard" value for legs length vs. height? I always thought that I have long legs and short torso but I have never seen any statistics. I am 184 cm and my inseam is 91 cm.

snails_pace said:

Thanks for the input. THe bike it is going on is a Bianchi Eros (sice 53). The bike is for my wife and she is 5'7" and her legs are a bit long compared to her torso.

My initial thought was that the bike may be too large, but the 51 was obviously too small. Perhaps we should try other brands. So far she prefers the Bianchi to Giant and Trek but that is all at the same (and prefered LBS).

Here locally about the only other choice is Specialized and maybe Lemond.

Thanks again for the input.

I suggest downloading the geometry of the Felt Road Bikes, have a look at their 52cm frames, particularly top tube and stem measurements, seat post angle will be steeper also. They should suit her qite nicely. http://www.feltbicycles.com/felt2006/03ROAD/road.php

Leg length isn't an absolute as you need to examine the upper leg vs. the lower leg. Two people with a 32 inch inseam may not both have the two parts of their leg divided equally.

Personally, I don't like to muck with an extreme short or extreme long stem to compensate for an improperly sized frame.

Deanster04 said:

Stability is good on the short stem it is the quickness change that people going from longer to shorter stems that people react to which is a muscle memory and perception issue not one of stability. What ever one is used to.

Yeah, I should have clarified that a bit better. Dynamic stability is only dependent on factors like trail, wheel mass, and cg relative to wheelbase. Stem length only affects control input.

capwater said:

Personally, I don't like to muck with an extreme short or extreme long stem to compensate for an improperly sized frame.

There's certainly enough variation in top tube length between brands/models that nobody should have to. How much it really matters is debatable though. There are a lot of pros using 130 and 140mm stems simply because their sponsors can't provide the right sized frames for them. The shortest I've personally used is 90mm. It feels to me to be right on the edge of being too twitchy, but it's on a soft enough frame that it's not a problem.

capwater said:

Leg length isn't an absolute as you need to examine the upper leg vs. the lower leg. Two people with a 32 inch inseam may not both have the two parts of their leg divided equally.

Personally, I don't like to muck with an extreme short or extreme long stem to compensate for an improperly sized frame.

Exactly, my thought as well.

100-115mm has always done me well(on Road)- and thats with a properly sized frame/top-tube. On my MTB, I have a 120mm (my LBS told me to get this size when I was picking up parts for it..... I wasn't sure what size stem I needed... and initially thought the top tube was going to be a little short for me , thus I thought I needed a longer stem- like a 130mm ... WRONG 🙂

The length of your stem should be an extension from your top-tube length... to give you an A(top tube length) + B(stem length) = C(your reach to the top part of the hoods on the bar).

Do you think that having for ex. a 56cm top tube and a 11 cm stem would be the same as a 54 cm top tube and a 13 cm stem?

It's a question I'm asking myself since a while...

A shorter stem gives you a quicker steering, but then a longer top tube gives you a longer wheelbase, so what's the difference?
(probably a shorter top tube also means a shorter seat tube, unless you are doing your custom geometry).

frenk said:

Do you think that having for ex. a 56cm top tube and a 11 cm stem would be the same as a 54 cm top tube and a 13 cm stem?

It's a question I'm asking myself since a while...

A shorter stem gives you a quicker steering, but then a longer top tube gives you a longer wheelbase, so what's the difference?
(probably a shorter top tube also means a shorter seat tube, unless you are doing your custom geometry).

Your top-tube length is EXTREMELY VITAL... in comparison to your stem length(big deal... you stem is too long/short , swap it out for something else) , but you cannot change a top-tube length.

LOOK at it this way, your top tube sizing directly influences your geometry/position on the bike. SO, to answer your question ... the 56cm TT vs. 54cm TT .................. NO, they are not the same.

For me, the 56cm TT + 11cm stem is a good fit for ME(5' 10" w/o shoes on , maybe a 55%lower body, 45% upper body ).

Trying to compensate for a shorter top-tube w/ a longer stem 130mm+ ..... is not a solution to the real underlining problem. Get a proper fit.... and I guarentee 98% of the time , your reach to the bars will in effect result in a 10-12cm(MAX) stem. 😉

snails_pace said:

I am trying to find a road bike for my wife. In the process of fitting her one of the LBS adjusted the stem length to 80mm.

My question is will this negatively affect the bikes handling? ...

Stem length does not really affect the bike stability. As an extreme example, Terry sells a T-stem (i.e. 5 ot 10-mm stem) for their small (women's) road bikes, many mountain bikes come with a tiny stem and I have seen a few short tourers who used a reversed stem. Generally speaking, women have a long pelvic structure, and therefore a relatively short torso, so they need closer handlebars.

As for your friend who "lost some stability when he went from 110 to 90 mm", it's not related to stem length per se but rather to front/rear weight distribution. By using a shorter stem, he is more upright, puts more weight on the rear wheel and less on the front one. It's roughly the same phenomenon one may observe by riding on the drops, then on the tops. If he (she) were riding on ice, he would feel a striking difference, with more traction because there's more weight on the rear wheel, but less steering because the front wheel would float.

As a user of 80-90-mm stems, the only "problem" I see is that they are hard to find.

mgagnonlv said:

Stem length does not really affect the bike stability. As an extreme example, Terry sells a T-stem (i.e. 5 ot 10-mm stem) for their small (women's) road bikes, many mountain bikes come with a tiny stem and I have seen a few short tourers who used a reversed stem. Generally speaking, women have a long pelvic structure, and therefore a relatively short torso, so they need closer handlebars.

Another extreme example: imagine a 2 meter-long stem. With that stem you would have to move your hands a lot to make a turn (the circumference "drawed" by the handlebar around the fork is much larger, so to turn say 10 degrees you have to make a bigger translation over the circumference).
In other words, a small movement of the handlebar won't change much the direction of the wheel.

OTOH a short stem means a small "imaginary circumference" drawn by the handlebar, so a small movement will result in a bigger angle.
Of course if a small handlebar movement causes a big angle rotation your bike is less stable.
Now we are talking about differences of the order of 2 cm, but still the principle is the same.

mgagnonlv said:

As for your friend who "lost some stability when he went from 110 to 90 mm", it's not related to stem length per se but rather to front/rear weight distribution. By using a shorter stem, he is more upright, puts more weight on the rear wheel and less on the front one. It's roughly the same phenomenon one may observe by riding on the drops, then on the tops. If he (she) were riding on ice, he would feel a striking difference, with more traction because there's more weight on the rear wheel, but less steering because the front wheel would float.

As a user of 80-90-mm stems, the only "problem" I see is that they are hard to find.

if
shorter stem => less weight on the front => less stability
holds, then also
shorter stem => less stability
holds. :-)

All useless argument!

Stem length is more about bike fit and comfort than stability.

For issues on stability look into fork rake and head tube angle.