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What stem length do I need?

Everything you need to know about the effects of stem length on fit and bike handling

Stu Bowers
28 Apr 2022

Stem length has a huge effect on how your bike handles. Located right beneath your nose, your road bike or gravel bike's stem is perhaps the part that you look at most while riding, but how much consideration do you give it?

There’s every chance you simply stick with whatever stem comes fitted when you buy a bicycle, but stem length affects your position on the bike, not to mention how the bike handles.

Let’s start by considering the options. Stock stems for road bikes and gravel bikes typically come in lengths from 60mm to 140mm, so there’s huge scope for making changes to a bike’s reach. But that’s only half the story.

Stem length in brief

  • Stems are measured centre-centre
  • There's no single ideal length
  • Can be used to adjust fit
  • Road stems are typically 90-120mm long
  • Gravel stems are typically 60-100mm long
  • Stems come in different angles and can be flipped to adjust stack
  • Shorter stems turn quicker, but the difference is small

What stem length do I need?

There's no single right answer and you should choose the stem which gives you the best all-round position on the bike.

Stem length is measure from the centre of the steerer clamp to the centre of the handlebar clamp.

The sweet spot stem length for road bikes is often said to be in the 100mm to 120mm range, but not everyone agrees, and shorter stems are not unusual.

Gravel bike stems are often considerably shorter (e.g. 70mm), with relative frame reach lengthened to compensate.

‘It’s a bit of a cliché that a too-short stem will over-quicken the handling. It’s only true to a point,’ says Phil Cavell, director of Cyclefit in London.

‘Needing a 70mm-80mm stem [on a road bike] probably means bike sizing needs to be reviewed, but many riders are happy to ride a 70 or 80 or 90mm stem without difficulty. Conversely we also sometimes fit 130mm.’

‘We design our bikes around a 110mm stem,’ says Anders Annerstedt, co-founder and chief designer at Rolo Bikes.

‘But there’s no single ideal stem length. Each case is different depending on the rider and geometry. But on our bikes a 70mm stem would feel very twitchy.’

Some riders will be more sensitive to change than others, which Annerstedt puts down to how close to ideal the set-up is in
the first instance.

‘The better your fit, the more likely it is that you will notice smaller changes. If you’re starting from a poor fit in the first place then bigger changes may not be so noticeable.’

Photo: Joseph Branston

But making any positional changes, no matter how big or small, should not be done without considering the knock-on effects elsewhere.

‘Even a 10mm change in stem length can make a huge difference,’ says Jez Loftus, bike fit specialist for Trek. ‘Also be aware no single adjustment is mutually exclusive.

‘Changing stem length will alter the way a rider holds their head, which can affect muscles in the upper back, neck and shoulders, but less obvious could be shifts in knee tracking or even ankle angle.

‘You have to consider every element of the fit each time you make a single adjustment.’

There is of course no harm in experimenting with stem length, and changing stems takes just a few minutes on most road and gravel bikes.

Make sure you choose a replacement stem that matches the diameters of your handlebar and headset, and follow our guide to adjusting your headset to make sure you get the tricky part right.

The latest high-end road and gravel bikes sometimes make things more difficult here by using proprietary bar and stem setups.

Some will have non-standard spacers that limit your choice of stems while at the extreme end, one-piece bar and stem assemblies force you to change the entire cockpit for a simple stem length adjustment. 

Given the choice between a fancy aero cockpit that doesn't allow any adjustment, and a more traditional option made up of separate components, we'd favour the latter as it's just more convenient.

What angle stem do I need?

Headset bearings - Loosen stem bolts

Stems also come in a wide variety of angles too, with inclines commonly ranging from +/-6° to +/-17° (+/- because stems can usually be flipped and used either way up).

This is because the stem mounts to the fork steerer, which is itself at an angle – commonly around 73° to the horizontal. That means a stem with an angle of -17° will sit parallel to the road, while a -6° stem will point slightly upwards.

Again, there's no single right answer here, but changing angle is another way to change the height of your handlebars. For example, if your -6° stem is already mounted as low as possible on the fork steerer with no spacers underneath it, but you want to get even lower, you could swap to a -17° stem. 

Alternatively, if you want to raise your handlebars but your stem is already mounted as high as it will go, flipping your -6° stem upside down so it becomes a +6° will bring them higher, and you could also opt for a stem with more rise (a bigger angle) to go higher still.

Stem length and the correct reach  

‘The first thing you have to ask is: why are you changing the stem?’ says Cavell. ‘Often it’s the go-to place to correct postural issues. Sometimes the bars feel too far away, but it’s not always as straightforward a fix as it seems.

‘For instance, pelvic rotation is a component of reach, so a passive and weak posterior rotation – which could be a consequence of a number of things such as inflexible/short hamstrings, poor core or poor postural awareness – can lead to feeling too stretched.

‘A body adaptation may be needed, not a stem change. Pressure mapping [on the saddle] is a great diagnostic tool to establish this.

‘Another important component is centre of gravity, which also shifts depending on stem length,’ Cavell adds.

‘This will affect weight distribution, and so have a knock-on effect on braking, cornering and so on. It could also affect power production – if the stem is too short it could take the tension out of the glutes and negatively affect muscle recruitment.’

How does stem length affect bike handling?

‘The textbook theory goes a little like this,’ says Annerstedt. ‘A long stem length is effectively a longer steering lever arm, so will be less responsive but may feel more stable, particularly at high speed.

‘A short stem will be more responsive to steering inputs but potentially a little less stable. It’s essentially the same reason a bus has a very large steering wheel, and an F1 car has a tiny one.’

Another often overlooked consideration is that a longer stem can also flex more easily, which can in extreme cases also make for more vague steering, although this is unlikely to be an issue with a good quality stem from a mainstream manufacturer.

With so many variables at play, it would be best to seek advice from a qualified bike fitter. Even then, attitudes may change over time, and Annerstedt thinks we’re due a rethink.

‘I know I’m contradicting all of the pros in cycling right now, but for me the future will be stem lengths getting much shorter and top tubes getting longer, just like in mountain bikes,’ he says.

‘The frame is much better able to absorb road shocks with longer tubes and a longer wheelbase, plus it will be more stable, while reduced fork rake and a shorter stem will keep the handling sharp.

‘But as always in the bicycle industry it’s so hard to get people to try something new.’

Got your head around how stem length affects the handling of your bike? Read the next in our series on bike fit variables on understanding the role of wheelbase

This article first appeared on Cyclist in 2018 and has since been updated with contributions from our team of experts.

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