Bike Fit Basics: How to Set Up Your Mountain Bike
A good fit stops the bike fighting you. Work through saddle height, position, reach and controls in this order, and change one thing at a time.
Bike fit sounds like a specialist job, and at the extreme end it is. But the adjustments that decide whether a ride feels easy or painful are simple, and you can work through them at home with a multi-tool and a tape measure.
Saddle height first
Set the saddle so that, with your heel on the pedal at the bottom of the stroke, your leg is almost straight. Clipped in and pedalling normally, your knee should keep about a 25 to 30 degree bend. Too low and your knee compresses every stroke; too high and your hips rock and your lower back complains.
- Front knee pain: usually saddle too low or too far forward.
- Back-of-knee pain: saddle too high.
- Numb hands: too much weight on the front; revisit reach, not just the saddle.
Fore and aft
Slide the saddle so that your knee sits roughly above the pedal spindle when the crank is level. Riders who climb seated a lot often slide the saddle a little back; riders on tight, technical trails often prefer it forward for weight over the front wheel.
Write your numbers down. Saddle height and saddle setback are the two measurements you will want to repeat on every bike you own.
Reach and stem length
Reach is the usual culprit behind sore hands and shoulders. A stem 10 to 20 mm shorter moves weight off your hands, opens your chest and quickens the steering. Try a shorter stem before you consider a new frame; it is one of the cheapest and most effective changes you can make.
Bar width, roll and height
Wider bars add steering leverage and control on descents; narrower bars suit smooth, tight climbing. A common trail width is 760 to 800 mm, and many riders trim a few millimetres at a time until it feels right. Roll the bar so your wrists sit in a relaxed, neutral angle. Add or remove stem spacers to raise the front if your lower back tightens, or lower it if the front wheel lifts on steep climbs.
Controls
Angle your brake levers so they line up with your forearms, and set the reach so one finger sits on the end of the blade. A lever angled too far down forces your wrist to reach and weakens your grip on rough ground.
A simple process
Change one adjustment, ride your usual loop, and note how your hands, back and knees feel at the end. Do not change saddle height, stem and bar roll in the same week. Fit also drifts with time, injury and the trails you ride most, so review it once a season and after any big change in saddle time.
Get the basics right and the bike disappears underneath you, which is exactly what a well-fitting mountain bike should do.
Frequently asked questions
How do I set my saddle height?
With your heel on the pedal at the bottom of the stroke, your leg should be nearly straight. Pedalling normally, keep a 25 to 30 degree knee bend at the bottom.
What is the fastest bike fit change?
Often a shorter stem. Dropping 10 to 20 mm of reach moves weight off your hands and usually fixes numb hands and shoulder fatigue.
How wide should mountain bike bars be?
Many trail riders run 760 to 800 mm. Wider bars add control on descents; trim a few millimetres at a time until they feel right for your trails and shoulders.
