Stem length affect on steering

[Dave_C]

I have been given a lovely Dawes Audax by a friend who not longer rides it. The frame if 60cm but I'm used to riding a 57/58(?)cm frame. I'm 6ft or 183cm tall and of normal proportions.

The reach is further than I'm used to, so I'm thinking of fitting a shorter stem. I plan to measure from the top of the 'seat post to the handlebars' and then compare and buy a shorter stem, so the reach is the same. But what I want to know is, how this is going to affect the handling, steering etc? Anything negative or positive. The current newer forks are ITM Millenium replacing the original Steel Quil Stemed forks. I have the original forks, quil stem etc...

Many thanks, Dave C

(The steering currently appears to wonder to the side very easily, though only when stationary, I have not tried it when moving).

[BrianI]

Don't know if this helps, but I changed the stem on my XL (59cm effective top tube, 56cm C-T seat tube) Pinnacle Dolomite 2 from the supplied 120mm stem, down to 100mm. Can't say I noticed any difference at all in the steering or the handling. 

When I'm on the tops, or in the drops, when I look down at the front wheel, the hub is obscured by the bars, which suggests to me the stem length is about right?

[PaulF]

Contrary to what BrianI found when I switched the stem on my Peregrine from 120 to 100mm it total transformed it! Went from handling like a barge to a nice snappy responsive bike.

Different bikes, different riders so I’d say give it a try and see how it works for you.

[phantasmagoriana]

I changed my stem from 90mm to 80mm (well, it was changed at a bike fit) and noticed a difference - whereas it's more comfortable, the handling's definitely twitchier. I rode a bike with a 120mm stem on holiday a few months back, and was amazed at how much more stable it felt - I could even ride no-handed, which I've never been able to do before. I should really have a smaller frame, though.

[sojournermike]

Shorter stem(reach)/narrower bars tend to make handling a bit slower quicker and feel more less stable. How strong the effect is depends on lots of other factors such as geometry and tyre size/pressure, probably including where you like the saddle and how that affects weight distribution etc. Probably you will get used to most but try it and see. Possibly the stability of a longer stem might mean it's preferable downhill all else being equal.

Other interesting points:

1. I think changing stem length is unlikely to affect whether you can ride no hands - most likely down to othe rgeometry differences

2. modern mountain bikes have really short stems and wide bars, but geometry is very slack so they need the short stem or the steering is way too slow

[Brucey]

FWIW if you notice a big change in handling when riding normally with a (small) change in stem length there are two main possible reasons for this

1) changing the stem length has changed the weight distribution

or

2) there is/was too much weight on the handlebars to start with

to a first approximation, when you are pedalling normally, you should be able to take one hand off the bars without tying yourself in knots or having the bike head off at an angle; the action of pedalling ought to exert a force on the upper body that  largely unweights the handlebars, and the correct riding position varies a little with both rider build and  how you pedal.

Note that when descending at speed, it is normal for there to be more weight on the handlebars, and handling may vary a bit more with stem length than when riding normally.

cheers

[Dave_C]

Many thanks for the replies, I appreciate the feedback and help. You all raise some interesting points and I am very grateful.

I measured the top of the seat post to handlebar of my Dawes Galaxy (57/58?) and it is 68cm (approx.). The Dawes Audax (60) is 72cm so that would suggest I need a 4cm shorter stem. The current stem is 12cm (assuming stem length is dead centre of the bars to the dead centre of the steerer). Now never having changed stems (about the only thing I haven't changed/upgraded/ordered), am I right in this assumption that, the stem length is dead centre of the bars to the dead centre of the steerer?

Thanks, Dave C

[Blodwyn Pig]

you need to compare saddle position to the handlebars on both bikes, yes, BUT compare with similar bars.Some bars have long ramps,  needing  shorter stem to put the hoods where you want them, whereas other bars have short ramps, needing a longer stem. The  difference is that the hoods remain the same but the 'tops' are at different distances from the saddle. What i mean is.....comparing one bike against another is awkward is the bars are significantly different.  Also type and length of 'brifter' used, has an effect, on weight distribution.

Take Olive for example.  came with a 120mm stem and bars with small ramps,  meaning the tops were a bit of a stretch to suit my preferred  saddle position, so swapped for a 100mm stem and Nitto Noodles, with looong ramps, but the hoods are near enough the same. ( noodles actually sweep backwards before the bends)

I set my bikes up with some sticky tape ,a pencil and a plumb bob ( peice of string with a weight, usually a spanner, on the end)  Sticky tape to top tube of both bikes,  level surface, and plumb bob thro bb c/c, mark on sticky tape,  then straight edge thou bb c/c and pencil mark,  and measure both saddle set backs, to ensure the same, then measure to tops, and hoods, THEN compare, and see where you want to go.best of luck

[Dave_C]

you need to compare saddle position to the handlebars on both bikes, yes, BUT compare with similar bars.Some bars have long ramps,  needing  shorter stem to put the hoods where you want them, whereas other bars have short ramps, needing a longer stem. The  difference is that the hoods remain the same but the 'tops' are at different distances from the saddle. What i mean is.....comparing one bike against another is awkward is the bars are significantly different.  Also type and length of 'brifter' used, has an effect, on weight distribution.

Take Olive for example.  came with a 120mm stem and bars with small ramps,  meaning the tops were a bit of a stretch to suit my preferred  saddle position, so swapped for a 100mm stem and Nitto Noodles, with looong ramps, but the hoods are near enough the same. ( noodles actually sweep backwards before the bends)

I set my bikes up with some sticky tape ,a pencil and a plumb bob ( peice of string with a weight, usually a spanner, on the end)  Sticky tape to top tube of both bikes,  level surface, and plumb bob thro bb c/c, mark on sticky tape,  then straight edge thou bb c/c and pencil mark,  and measure both saddle set backs, to ensure the same, then measure to tops, and hoods, THEN compare, and see where you want to go.best of luck

This is true Blodwyn, and I intend to get the same bars as on my audax bike, 3T Ergoterra Pro Alloy Road Handlebar.

[frankly frankie]

When I'm on the tops, or in the drops, when I look down at the front wheel, the hub is obscured by the bars, which suggests to me the stem length is about right?

I've read that the ideal is, in your normal riding position, the front hub should be visible midway between the bars tops and the fork crown.  That probably assumes 'touring' angles of 72/73 degrees.  That said, I'm like you, the hub is obscured by the bars, I prefer a forward position.

[rafletcher]

Don’t forget fashion. When I bought my first “proper racer” (in the late ‘80’s) I was recommended a 60cm frame. Nowadays it’s a 56cm frame. I’ve not changed much.

A shorter stem will “slow” the steering, making it less twitchy, which is IMO good on a tourer.  You’ll have less seatpost showing than on your “normal” size, but again for a tourer that’s fine IMO.

[Ian H]

A shorter stem will “slow” the steering, making it less twitchy...

Interesting idea.  Will it have that effect when riding no-hands?

[BrianI]

Many thanks for the replies, I appreciate the feedback and help. You all raise some interesting points and I am very grateful.

I measured the top of the seat post to handlebar of my Dawes Galaxy (57/58?) and it is 68cm (approx.). The Dawes Audax (60) is 72cm so that would suggest I need a 4cm shorter stem. The current stem is 12cm (assuming stem length is dead centre of the bars to the dead centre of the steerer). Now never having changed stems (about the only thing I haven't changed/upgraded/ordered), am I right in this assumption that, the stem length is dead centre of the bars to the dead centre of the steerer?

Thanks, Dave C

Hi Dave C, I have a spare oversize 31.8mm 7 degree 80mm stem if you want it? (it's a cheap on-one one) The only other spare stems I have in the shedde is an oversized 7 degree 115mm or a comedy +35 degree 110mm one ;-) 

Cheers, Brian (from the most excellent forth bay wheelers)

[rafletcher]

A shorter stem will “slow” the steering, making it less twitchy...

Interesting idea.  Will it have that effect when riding no-hands?

No that’s down to basic geometry.

[Ian H]

A shorter stem will “slow” the steering, making it less twitchy...

Interesting idea.  Will it have that effect when riding no-hands?

No that’s down to basic geometry.

So how/why does it affect steering otherwise?

[aidan.f]

Pendulum effect of the bars damping oscillations?

[sojournermike]

A shorter stem will “slow” the steering, making it less twitchy...

Interesting idea.  Will it have that effect when riding no-hands?

No that’s down to basic geometry.

So how/why does it affect steering otherwise?

Weight distribution, bar movement to achieve particular steering angle (think linear distance bar moves not angle) and longer reach means hands push forwards more further stabilizing steering

[Kim]

bar movement to achieve particular steering angle (think linear distance bar moves not angle)

I'm not convinced this matters.  Ever ridden a tiller steering recumbent?  The linear distance is massive, and it makes the whole thing *look* really wobbly to an observer, but the rider just thinks in terms of steering torque^[1] and gets on with it.  Obviously a longer leaver means you need less force and vice-versa, which will make it feel different, but I don't think that translates to a change in the bike's stability.

Agreed that there's an effect on weight distribution from moving the bars on an upright^[3], which can obviously affect the behaviour of the bike.

(As for the current trend to wide bars and shorter stems on MTBs, I think this is simple geometry: If you want you hands wide apart for more leverage^[2], the stem has to be shorter so you can reach.)


_{[1] The absolute angle doesn't matter, it's how much you're pushing.
[2] I think the trend has gone too far, but perhaps I value keeping my hands out of the scratchy stingy stuff and the ability to fit my bike through doorways and into vehicles too much.
[3] Unless it's a sit-up-and-beg position, which is basically a recumbent in steering terms:  The bars may be loaded with some fraction of the rider's arm weight, but they aren't supporting the upper body and making a substantial difference to the centre of mass, and wouldn't normally be subjected to pedalling reaction force.}

[valkyrie]

I've changed stem lengths several times on several bikes. Makes a difference to comfort, no difference at all to handling.

[sojournermike]

bar movement to achieve particular steering angle (think linear distance bar moves not angle)

I'm not convinced this matters.  Ever ridden a tiller steering recumbent?  The linear distance is massive, and it makes the whole thing *look* really wobbly to an observer, but the rider just thinks in terms of steering torque^[1] and gets on with it.  Obviously a longer leaver means you need less force and vice-versa, which will make it feel different, but I don't think that translates to a change in the bike's stability.

Agreed that there's an effect on weight distribution from moving the bars on an upright^[3], which can obviously affect the behaviour of the bike.

(As for the current trend to wide bars and shorter stems on MTBs, I think this is simple geometry: If you want you hands wide apart for more leverage^[2], the stem has to be shorter so you can reach.)


_{[1] The absolute angle doesn't matter, it's how much you're pushing.
[2] I think the trend has gone too far, but perhaps I value keeping my hands out of the scratchy stingy stuff and the ability to fit my bike through doorways and into vehicles too much.
[3] Unless it's a sit-up-and-beg position, which is basically a recumbent in steering terms:  The bars may be loaded with some fraction of the rider's arm weight, but they aren't supporting the upper body and making a substantial difference to the centre of mass, and wouldn't normally be subjected to pedalling reaction force.}

I suspect we largely agree - the handling/stability is really down to geometry etc. Apart from weight distribution effects, the stem length probably affects feel more than handling, although steering that needs less movement and/or effort may contribute to less actual stability if the rider makes unintentional inputs.

I completely agree mtb design has gone too far down the slack headtube, wide bar, sort stem approach. I know what it’s meant to do, but 66 degree headtube angles are not really suitable for my riding.

[Brucey]

I've changed stem lengths several times on several bikes. Makes a difference to comfort, no difference at all to handling.

for a small change to make a big difference, you would have to alter the weight distribution. If you have a well-set riding position, there may be so little weight on the handlebars (when pedalling normally) that there won't be any real difference, any more than there would be moving your hands around on the bars.

However if you have too much weight on the bars anyway, changes in stem length can make a bigger difference.

I am of the view that any tiller/reverse tiller action is most often soon got used to, but that it is important, esp at low speeds.  You only get a few goes at being unfamiliar with it on any given machine and after that it becomes 'normal' and you don't notice so much any more.

However if two weird features are combined (eg recumbent with front wheel weight bias and reverse tiller steering) then an uphill start can become virtually impossible without a lot of practice. One weird feature alone is much easier to cope with...

cheers

[frankly frankie]

for a small change to make a big difference, you would have to alter the weight distribution. If you have a well-set riding position, there may be so little weight on the handlebars (when pedalling normally) that there won't be any real difference, any more than there would be moving your hands around on the bars.

And if its a small change (less than 2cm) you will probably slightly adjust your hands/bum positions to compensate, at least partially.

By the way we forget what a luxury it is, to mess about with stem lengths.  With the old quill-type stems it is just about the very last component you would want to change.