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Too short or too long? How do you know the correct length stem for your road bike? road.cc has the answer

How do you what the correct stem length for you and your bike is?

I’m going to start by suggesting the best way to find the answer to that question is to arrange a professional bike fit with a reputable bike shop. Most shops offer bike fits of various varieties from simple to advanced, and many offer it as part of the buying process so you’re not charged loads of extra money on top of your new bike.

Stems come in many lengths from stubby to super stretched. Put simply, if you want a racy, aggressive and aerodynamic position, a longer stem will provide a more stretched out riding position. If comfort is your top priority, a shorter stem length will bring the bars closer to the saddle and put you in a more upright position, placing less strain on your back.

But the stem length needs to be considered as part of the bigger picture of the frame size, saddle height, saddle fore-aft adjustment and the shape and size of the drop handlebars. That’s where a professional bike fit is invaluable, as all those other factors will be considered.

Read more: 9 top tips for setting up your new road bike

Stem length affects handling

Changing the stem length not only impacts your fit and comfort, it affects the handling dynamics of a road bike. A shorter stem will result in snappier steering, a longer stem will produce slower steering. Adjusting the stem length can be used to tailor the handling. That’s generally why cyclocross races use a shorter stem, and long distance road cyclists opt for a longer stem.

Storck Fascenario.3 Platinum - riding 3.jpg

Storck Fascenario.3 Platinum - riding 3.jpg

Correct reach

Stem length alters the reach to the handlebars. Reach is a measurement from the centre of the head tube to an imaginary vertical line drawn through the bottom bracket. All new bikes are supplied with reach (and stack) measurements which aid in purchasing a new bike. A longer stem doesn't change this reach, but it does change the effective reach of the bike, and it's worth taking into account.

If you’ve been riding your bike for some time though and you’re happy with the general fit, a good indication of whether the stem length on your bike is correct is simply to go on how you feel. Do you feel too stretched and reaching the hoods strains your back? Or do you feel cramped? Pain in the neck, shoulders and lower back can be clear indicators that you might be better off with a longer or shorter stem.

- 9 ways to make your bike more comfortable

Optimum position

What you’re aiming for is a position that ensures you have a slight bend in the elbows to allow your arms to bend easily as the front wheel tracks the road surface. You don’t want your arms locked out straight, that’s a sign of a stem that is too long. It’s tricky to assess yourself when riding though - riding past shop windows is a good tip, but even better is, as I’ve mentioned before, getting a professional bike fit.

One good rule of thumb for choosing the correct length stem (and it works for the road.cc team) is to sit on the bike with your hands on the top of the hoods and look down at the front hub. If the stem length is correct, the handlebars should completely hide the front hub. If you can see the hub in front of the handlebar, the stem is too short.

Experiment with stem length

Don’t be afraid to experiment. Making small changes can bring about noticeable improvements in comfort or aerodynamic performance, depending on what you’re trying to achieve.

Canyon Endurace Wmn CF 9.0 - stem.jpg

Canyon Endurace Wmn CF 9.0 - stem.jpg

If you’re friendly with your local bike shop they’ll likely have a couple of spare stems and they’ll lend you one to try out, or you could try a cycling friend or even your local club.

Start with a stem that is 10mm longer or shorter, depending on whether you want to extend or reduce your reach to the handlebars, and go for a ride. How does it feel? Better? It’s good to do a couple of rides of decent length to see how the stem length change impacts your riding comfort.

But if you’re making radical changes, a 70mm stem on a 58cm frame or a 140mm stem on a 52cm frame, for example, is a clear indication that you might be riding the wrong frame size.

Read more: How to fit and set up a saddle

Frame size-specific stem lengths

Most bike manufacturers fit different length stems across the size range, so shorter stems on smaller frames and longer stems on bigger frames. This size-specific approach goes a long way to getting you set up with the correct stem length, providing you’ve chosen the right size frame (another area where a bike fit comes in useful).

Generally speaking, stem lengths on road bikes vary from 80 to 140mm, with 100 to 110mm perhaps the most common sizes. There are shorter and longer stems available if you’re short or very tall and ride a frame size at the extreme end of the size range.

Stem angle

The other factor to also consider when choosing stem length is the rise of the stem. If you want a lower position, opt for a stem with a negative rise stem that lowers the handlebar height in relation to the ground. If you crave a more upright position, a stem with a positive rise will lend you a more comfortable fit. It’s all down to personal preference.

Don’t copy the pros

Over the years I’ve seen many amateur cyclists simply take their stem length decision directly from what the pros are using. But a word of warning. A professional cyclist covers 30,000+km in the saddle each year. The bike is essentially their office, and their bodies are conditioned to a stretched, aerodynamic position. Plus, they do a lot of core work in the winter to give them the strength and flexibility to maintain such positions.

things pros do - 1 (16).jpg

things pros do - 1 (16).jpg

But there are many pros that clearly ignore sensible bike fitting advice and forge their own path, and pros riding smaller frame sizes and fixing the reach with a super long stem is common in the professional peloton. That’s why 130 and 140mm are common stem lengths, and we’ve even seen custom made 150mm stems on some bikes.

Based on that, I wouldn’t advocate copying any professional rider when choosing your stem length. They might look fast and slammed but replicating their fit could be asking for back and neck trouble. You’ve been warned.

Read more: Tour Tech 2017 – The stems the pros are using

There’s an app for that

Yes, in this world of apps for everything, there are some apps that claim to be able to help you adjust your stem length and bike fit from the comfort of your living room.

Bike Fast Fit uses the phone's video camera to dynamically record the rider’s position to analyse a whole range of measurements, including stem length as part of the frame reach, forearm and torso angle.

We hope this was helpful? If you have any tips you use for setting the correct stem length, do add them to the comments below.

David has worked on the road.cc tech team since July 2012. Previously he was editor of Bikemagic.com and before that staff writer at RCUK. He's a seasoned cyclist of all disciplines, from road to mountain biking, touring to cyclo-cross, he only wishes he had time to ride them all. He's mildly competitive, though he'll never admit it, and is a frequent road racer but is too lazy to do really well. He currently resides in the Cotswolds.

28 comments

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Mark B [27 posts] 10 months ago
2 likes

If it's true that "Reach is a measurement from the centre of the head tube to an imaginary vertical line drawn through the bottom bracket", as you say, then a stem can't have any effect on this.

I understand what you're trying to say, but I think you need to rewrite that paragraph. You need to introduce something like "effective reach" perhaps?

 

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David Arthur @d... [887 posts] 10 months ago
2 likes

Mark B wrote:

If it's true that "Reach is a measurement from the centre of the head tube to an imaginary vertical line drawn through the bottom bracket", as you say, then a stem can't have any effect on this.

I understand what you're trying to say, but I think you need to rewrite that paragraph. You need to introduce something like "effective reach" perhaps?

 

 

Good point, have tweaked that para. Thanks

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SculturaD [51 posts] 10 months ago
0 likes

So there's only iPhones out there, from the one app link provided.

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curdins [60 posts] 10 months ago
0 likes

"If comfort is your top priority, a shorter stem length will bring the bars closer to the saddle and put you in a more upright position, place less strain on your bike."

Really? Is  this simply a typo, where, if you're talking about comfort, you actually mean 'place less strain on your back'?

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David Arthur @d... [887 posts] 10 months ago
0 likes

curdins wrote:

"If comfort is your top priority, a shorter stem length will bring the bars closer to the saddle and put you in a more upright position, place less strain on your bike."

Really? Is  this simply a typo, where, if you're talking about comfort, you actually mean 'place less strain on your back'?

 

Clearly it's a typo that I missed. Thanks for pointing it out, I have amended it

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downesdesign [18 posts] 10 months ago
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Another point worth noting: From painful personal experience, I can say that replacing a long stem with a shorter one can be an effective means of reducing/eliminating neck problems (aka, Schermer's neck).

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BehindTheBikesheds [2299 posts] 10 months ago
0 likes

And shoulder/hand issues, as less of your upper body weight is being borne by them in a more upright position.

I've got fairly long arms for my height/upper body but with old hand/shoulder injuries but fortunately I've alwsys tended to buy a frame size that most would deem to be far too large (5ft 11 and 3 of my rides are 59/61cm sloping and a 62cm traditional) but still use a 100/110 stem and the longer/taller headtube helps alleviate the pressure.

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Roadie_john [85 posts] 10 months ago
1 like

The main reason the pros use long stems is because they often ride what would be for a ‘normal’ person, an undersized bike. 

I use long stems because I’m tall with long back and arms. My winter bike has a 145mm stem and that was a massive improvement on the original 130mm stem, which left me cramped. But it’s a 57 when I normally ride a 59...

Stem length is a personal thing...

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james-o [239 posts] 10 months ago
2 likes

While realising that this complicates things and isn't the focus of the article, it's worth getting the saddle in the right place so you're well balanced (height and fore-aft) first before thinking that stem length is a full fix for any discomforts. It can help but it's not the main thing. Start with the saddle as your base point for all fitting, then move on to other areas. 

The stem obscuring front hub thing tends to happen on classic geometry road bikes so it's a handy guide there but could lead to an overly-long stem on newer 'gravel' geometries with shorter stems and slacker head angles or longer fork offsets. Like knee over pedal it's usually a coincidence rather than an aim.

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SimonS [40 posts] 7 months ago
0 likes

So why do pro's often ride bikes that appear too small with extra long stems?

The top end bikes are supposedly designed with the pro's needs in mind so they should have short enough head tubes to get the drop they want, there shouldn't be any issues with stiffness now (which might have been an issue back in the days of thin walled steel tube gates), weight is added to frames to keep them UCI legal.   

A frame that's too small potentially results in excessive seat post (where you will get some flex) and a very long stem will affect the steering (on  a bike that's supposedly has carefully tuned handling based around one of normal length) 

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check12 [229 posts] 7 months ago
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SimonS wrote:

So why do pro's often ride bikes that appear too small with extra long stems?

The top end bikes are supposedly designed with the pro's needs in mind so they should have short enough head tubes to get the drop they want, there shouldn't be any issues with stiffness now (which might have been an issue back in the days of thin walled steel tube gates), weight is added to frames to keep them UCI legal.   

A frame that's too small potentially results in excessive seat post (where you will get some flex) and a very long stem will affect the steering (on  a bike that's supposedly has carefully tuned handling based around one of normal length) 

 

because they aren't designed with pros in mind, and pros need longer/lower reach. 

See the 1x 3t bike winning race bike and it's stem for example. 

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Jimmy Ray Will [938 posts] 7 months ago
0 likes
SimonS wrote:

So why do pro's often ride bikes that appear too small with extra long stems?

The top end bikes are supposedly designed with the pro's needs in mind so they should have short enough head tubes to get the drop they want, there shouldn't be any issues with stiffness now (which might have been an issue back in the days of thin walled steel tube gates), weight is added to frames to keep them UCI legal.   

A frame that's too small potentially results in excessive seat post (where you will get some flex) and a very long stem will affect the steering (on  a bike that's supposedly has carefully tuned handling based around one of normal length) 

 

Never forget that pro riders are generally young men. Young men that have often made decisions about positioning and frame preferences prior to even being men.... do not think that professionals choices are made through wisdom and insight, its often not the case.

That said, a smaller frame will handle quicker (due to the shorter wheel base), and the extra seatpost will indeed flex... which is a good thing for someone sat on the end of it for hours.

Plus long, slammed stems look good. 

I was 28 before I made the realisation that 110mm stems provide the best balanced handling, and actually, having my bars a bit higher was still aero enough and a damned sight more comfortable. 

 

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kil0ran [1071 posts] 7 months ago
0 likes

I was surprised to find after a recent bike fit that +10mm on the stem completely solved lower back pain, particularly as I didn't feel particularly cramped on the bike. At 5-11 I would normally be riding a 56 but a nominal 54 with a 110mm stem seems to be sweet spot (usually 54s come with a 100mm stem).

In the search for a new bike I've been relying on absolute stack/reach measurements and stack/reach ratio. Geometry Geeks is great for comparing geos and seeing if a bike's going to be within your fit envelope.

The one thing I regret is that I didn't measure the effective stack & reach of my old, perfectly set up bike. I've got the frame stack/reach from the manufacturer but have had to estimate the other measurements. If you're searching for a new bike make sure you've recorded the basic fit parameters from your old one:

Frame stack

Frame reach

Saddle tip to bar centre

Saddle setback (tip distance behind BB centre)

Bar centre stack

Bar centre reach

Saddle height from BB centre

Also record the position of your shifters and drops angle, if you're not swapping bars over.

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StraelGuy [1516 posts] 7 months ago
0 likes

We're all different. I'm 5' 11" and  ride a 58 cm frame with the stem shortened a centimetre to 100 mm and a 56 cm frame with the stem lengthened to 120 mm.

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imajez [109 posts] 1 month ago
0 likes

You cannot alter stem lenght without affecting handling. So you really need to use wider bars with shorter stems and vice versa to maintain handling. Assuming handling is fine to start with.

 

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henryb [56 posts] 1 month ago
0 likes

Indeed - I'm 5'11" too, but ride a 56cm frame with a 80mm stem

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srchar [1002 posts] 1 month ago
1 like

I have a mate who's obsessed with "looking pro" and has a long, negative rise, slammed stem because it puts him in a more aerodynamic position.  I on the other hand have 25mm of spacers and a straight 110mm stem.  Only one of us can ride in the drops for any length of time, which is the most aero position.  Guess who?

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don simon [2530 posts] 1 month ago
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I heard the salesman in a certain northern internet bike shop what also has a small salesfloor tell a customer that he had the perfect triangle whilst sat on the bike.

Get the perfect triangle and you'll have the correct stem length.

Does anyone know what the perfect triangle is?

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StraelGuy [1516 posts] 1 month ago
0 likes
don simon wrote:

I heard the salesman in a certain northern internet bike shop what also has a small salesfloor tell a customer that he had the perfect triangle whilst sat on the bike.

Get the perfect triangle and you'll have the correct stem length.

Does anyone know what the perfect triangle is?

 

Maybe he meant back, arms and top-tube  ?

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don simon [2530 posts] 1 month ago
0 likes
StraelGuy wrote:
don simon wrote:

I heard the salesman in a certain northern internet bike shop what also has a small salesfloor tell a customer that he had the perfect triangle whilst sat on the bike.

Get the perfect triangle and you'll have the correct stem length.

Does anyone know what the perfect triangle is?

 

Maybe he meant back, arms and top-tube  ?

Go on...

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hawkinspeter [2372 posts] 1 month ago
0 likes
don simon wrote:

I heard the salesman in a certain northern internet bike shop what also has a small salesfloor tell a customer that he had the perfect triangle whilst sat on the bike.

Get the perfect triangle and you'll have the correct stem length.

Does anyone know what the perfect triangle is?

Nope.

I'd assume that the triangle would be the 3 contact points - pedals, saddle and bars. However that doesn't make much sense as those 3 points are just what the bike is set up as, so they don't relate to the rider until there's been some measuring/fitting/adjusting.

They probably meant the back, arms and legs, but I wouldn't have thought that you could come up with a "perfect" triangle as that'd depend on the rider's flexibility etc.

Avatar
don simon [2530 posts] 1 month ago
2 likes
hawkinspeter wrote:
don simon wrote:

I heard the salesman in a certain northern internet bike shop what also has a small salesfloor tell a customer that he had the perfect triangle whilst sat on the bike.

Get the perfect triangle and you'll have the correct stem length.

Does anyone know what the perfect triangle is?

Nope.

I'd assume that the triangle would be the 3 contact points - pedals, saddle and bars. However that doesn't make much sense as those 3 points are just what the bike is set up as, so they don't relate to the rider until there's been some measuring/fitting/adjusting.

They probably meant the back, arms and legs, but I wouldn't have thought that you could come up with a "perfect" triangle as that'd depend on the rider's flexibility etc.

There can't be any hard numbers as we're all different, so I imagine the lead up as being on the lines of:

Salesman: Swing your leg over this mighty steed. How does that feel?

Punter: It feels fine,

Salesman: I thought so, I can see the perfect triangle (top tube, back, arms).

Punter: Perfect triangle, eh? This bike must've been made for me. Sold!

 

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StraelGuy [1516 posts] 1 month ago
0 likes

I just meant that if the lengths and angles formed by the triangle formed by back, arms and top tube look like an equilateral triangle, he considers the bike well set up?

Having said that, if a certain Mr. Hawkins has his two penneth, I'm sure squirrels will come into it somewhere .

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hawkinspeter [2372 posts] 1 month ago
4 likes
StraelGuy wrote:

I just meant that if the lengths and angles formed by the triangle formed by back, arms and top tube look like an equilateral triangle, he considers the bike well set up?

Having said that, if a certain Mr. Hawkins has his two penneth, I'm sure squirrels will come into it somewhere .

Could be, but you don't really want your arms straight as usually that means you've got too much weight on them.

Hmmm, perfect triangle?

 

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Jitensha Oni [140 posts] 1 month ago
0 likes
don simon wrote:
hawkinspeter wrote:
don simon wrote:

I heard the salesman in a certain northern internet bike shop what also has a small salesfloor tell a customer that he had the perfect triangle whilst sat on the bike.

Get the perfect triangle and you'll have the correct stem length.

Does anyone know what the perfect triangle is?

Nope.

I'd assume that the triangle would be the 3 contact points - pedals, saddle and bars. However that doesn't make much sense as those 3 points are just what the bike is set up as, so they don't relate to the rider until there's been some measuring/fitting/adjusting.

They probably meant the back, arms and legs, but I wouldn't have thought that you could come up with a "perfect" triangle as that'd depend on the rider's flexibility etc.

There can't be any hard numbers as we're all different, so I imagine the lead up as being on the lines of:

Salesman: Swing your leg over this mighty steed. How does that feel?

Punter: It feels fine,

Salesman: I thought so, I can see the perfect triangle (top tube, back, arms).

Punter: Perfect triangle, eh? This bike must've been made for me. Sold!

 

Yep, I’d assume that was the scenario in that case.

There are other defintions of the triangle that involve the balance of power, comfort and aerodynamics according to need, however, as described in:

http://go4distance.blogspot.com/2009/11/bike-fit-triangle.html

 

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Pushing50 [106 posts] 1 month ago
1 like
don simon wrote:

I heard the salesman in a certain northern internet bike shop what also has a small salesfloor tell a customer that he had the perfect triangle whilst sat on the bike.

Get the perfect triangle and you'll have the correct stem length.

Does anyone know what the perfect triangle is?

A bike salesman once told an ex-girlfriend in front of me that she had the perfect triangle during a bike fit. I knocked his bloody teeth out!! cheeky

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Karbon Kev [706 posts] 3 weeks ago
0 likes

So basically you're saying David, to keep trying out different stem lengths until you get the right length?

Your first tip to get a proper professional bike fit is the only way to ensure the correct length, done by a professional and not any old bike shop!

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Skytriker [3 posts] 6 days ago
0 likes

I just wasn't comfortable riding my Giant Defy. I felt too stretched out. After reading advice here, and elsewhere, I took the plunge and changed my 100mm stem for and identical 70mm one. That 40mm has made a huge difference. I am more comfortable, have noticed no change to handling and the numbness in my hands has decreased significantly. Although probably nothing to do with the stem change, my speed has increased by an average of 2 mph