Mountain Bike
Cockpit Setup & Seat Height

Bike Fit & Cockpit Overview

When it comes to mountain bike sizing, the proportional lengths of your arms and legs are arguably more important than your overall height. Your mountain bike's fit is determined by several adjustable contact points that make up what riders call the "cockpit" – the area where you interface with the bike. This includes:

>> Handlebars - height, width, & sweep

>> Stem - length & angle

>>Controls - brake levers, shifters, & dropper post lever

>> Grips - type, size, compound, & pattern

>> Saddle - height, fore/aft position, & angle

Stuck Between Sizes?

It’s actually quite common for riders to modify the stem, handlebars, and seatpost to get the best fit for their individual body dimensions. Every model of mountain bike has a different geometry, so when you're between bike sizes, these adjustments become even more crucial:

>> A bike that's slightly too large can be adapted by using a shorter stem and/or lower or swept back handlebars.

>> A bike that's slightly too small might work better with a longer stem and/or wider handlebars.

Terrain & Riding Style

The style of riding you’re doing will also dictate your body position and how much space you have in the cockpit. Although there’s a range of variance spanning each category, generally speaking:

>> Cross Country (XC): More stretched out cockpit, higher saddle position

>> Trail: Balanced position, moderate drop from saddle to bars

>> Enduro: More upright, wider bars, lower saddle

>> Downhill (DH): Very upright, wide bars, low saddle position

Essential Tools

Before getting started, gather these tools:

>> 4 / 5 / 6mm Allen Keys

>> Torque Wrench

>> Tape Measure or Ruler

>> Bubble Level

Cut-to-size increments shown on OneUp's carbon and aluminum handlebars.

Choosing Your Width
Handlebar widths are somewhat subject to trends - early mountain bikes featured very narrow bars and more recent generations tend to be closer to 800mm. Riding discipline has a little to do with it but it’s also dependent on rider size. Riders with smaller shoulder widths will likely find 800mm too wide, for example.

Your local bike shop should be able to give you suggestions for starting point widths and you can easily trim your bars if you find them too wide. In fact, a common mistake is not trimming them down as most bikes ship with full width bars. All of OneUp's handlebars feature cut-to-size increments to make cutting them down easy.

Choosing Your Rise
Rise can be tweaked with spacers or a riser handlebar, which will have different effects, and we’re just going to focus on handlebars here. Flatter bars will make it easier to put more weight on your front wheel but riser bars are more comfortable overall. A riser bar will give you a more centralized position and reduce fatigue.

A high rise is generally considered 40mm and up, but a nice starting place would be a little bit lower. OneUp handlebars come in 20mm and 35mm rises - just enough to make a difference without totally changing your ride.

For more info, check out: How to Choose Mountain Bike Handlebars

OneUp's 35mm Rise (top) and 20mm Rise (bottom) Handlebar Options

Stem Length 101
The length of your stem will have a substantial impact on your riding position and is the easiest way to dial the fit of your bike. Generally speaking, mountain bike stems keep it simple with a 0° rise (aka flat) and just three lengths: 35mm, 42mm, and 50mm.

If you feel like you’re between sizes on a particular model of bike, then consider the following changes to your bike’s stem:

>> Shorter stems can fix a bike that feels too big and make the bike more responsive.

>> Longer stems can help riders that feel too cramped in the cockpit and will slow steering down.

Stem Clamp Diameter
As far as stem diameter goes, the main thing is ensuring that it matches your handlebar diameter — 31.8mm or 35mm. If you're starting from scratch and not sure what handlebar diameter to go with, checkout our handlebar video in the section above.

Brake Lever Positioning
Proper brake lever setup is crucial for control and comfort:

>> Position levers where your fingers naturally rest while riding

>> Adjust reach so you can comfortably operate brakes from the hoods

>> Angle levers to create a straight line from your arms through your fingers

>> Set lever throw to engage early in the stroke for better modulation

Shifter & Dropper Lever Positioning
Proper shifter and dropper lever positioning allows for quick adapting on the trail:

>> Mount shifters inboard of brake levers

>> Position dropper lever where it won't interfere with braking

>> Ensure all controls are easily reached from your typical riding position

Mountain Bike Grips 101

Grips are ultimately a personal choice, although we are big fans of OneUp’s Lock-On Grips, which come in regular, thin, and thick options. When choosing grips, you should consider:

>> Lock-On vs Slip-On: Almost all mountian bikes utilize lock-on style grips to prevent unwanted movement on the trail.

>> Diameter: 30-40mm is the most common

>> Compound: Softer for comfort, harder for durability

>>Pattern: More texture for wet conditions

Finding Your Optimal Seat Height

Correct saddle height is crucial for power output, knee health, and overall control. While there are several methods to determine proper saddle height, we recommend starting with these steps:

1. Sit on your bike in riding position with your shoes and pedals mounted
2. Place your heel on the pedal at its lowest point
3. Your leg should be completely straight
4. When you clip in or place the ball of your foot on the pedal, this will give you the slight bend needed for optimal pedaling.

Need help choosing a seat? Check our How to Choose a Bike Seat guide.

Dropper Post Considerations

Modern mountain bikes typically have dropper posts, which allow for on-the-fly saddle height adjustments. While a dropper post allows for dynamic control over your bike seat height, you’ll want to ensure that your dropper post:

>> Has enough insertion depth in the frame (check manufacturer specs and visit our guide on How to Choose Dropper Posts). Provides full leg extension at maximum height

>> Drops low enough for technical descents - we like OneUp’s droppers for their short stacks and large amount of drop

>> Has its remote lever positioned for easy activation - the OneUp levers in particular have been praised for their smoothness

Setting Saddle Angle & Position

Start with your saddle level and centered on its rails;

>> For trail riding (a mix of ups and downs) a flat/level saddle is typically optimal.

>> For cross-country (XC) riding and/or frequent riding uphills, try angling the nose down 1-2 degrees; this relieves pressure on soft tissue and shifts the rider’s weight over the front wheel

>> For downhill (DH) riding and/or frequent riding down steeper terrain, try angling the nose up 1-2 degrees; this shifts the rider’s weight over the rear wheel

>> Fore/aft position should place your knee over the pedal spindle when cranks are horizontal

Use your smartphone and a leveling app to set your saddle angle.

Final Safety Check

Last but not least, before you go out riding, verify:

>> All bolts are torqued to manufacturer specifications

>> Stem is properly aligned with front wheel

>> Brake levers are secure and working correctly

>> Saddle clamp is tight and level

>> Grips are locked in place

>> Controls move freely without binding

Remember that bike fit is personal—matter of fact, we even have a women's specific bike setup guide—and may require fine-tuning over time. Start with these guidelines and adjust based on your comfort, riding style, and local terrain. If you're experiencing persistent discomfort or uncertainty about your setup, consider getting a professional bike fitting at your local evo bike shop.