Perfect Bike Fit
Article from the March 2013 issue of Ride Magazine.
Want every pedal stroke to really count? Need to go quicker in the rough? Here’s how.
Tape measure and plumb bob
The humble tape measure is very useful when it comes to bike fit. It pays to note down measurements as you experiment, then keep a record of your final settings. Include pressures and suspension settings; you’ll be glad of it one day. Measure the stem and bars (they’re not always as claimed) too, and don’t even bother buying a plumb bob – these highly useful things can be made from string and almost anything.
Step by step: Get the perfect fit
Essential tools • 4,5,6 mm Allen keys • T10 Torx • T25 Torx • torque wrench with measurements from 1,6 N.m up to 8 N.m • safety glasses • nitrile gloves • grease • tape measure • plumb bomb • fine sandpaper
1. Set the saddle height
To quickly get this right for cross-country or road riding, put one pedal right down and, with a straight leg, put your heel (without a shoe) on the pedal. It should be touching lightly. This should result in a slight knee bend when clipped in, which helps – you still need to float above the saddle at times. For a more in-depth set-up, see http://bit.ly/lgTqpG.
2. Sort the saddle set-back
Loosen the seatpost clamp, sit (carefully) on the bike, clip in and bring the pedals horizontal. Now slide the seat forwards or back until your knee sits directly above the pedal axle. You can use a plumb bob to line it up. With some extremes of saddle set-back, you’ll have to reset your saddle height.
3. Set the saddle angle
Loosen the saddle clamp: single-bolt clamps often use a 6 mm Allen key, while for twin bolt set-ups you only need to loosen one bolt (usually 4 mm) and tighten the other. The saddle is generally best horizontally, though a raised rear gives something to push against on climbs, and some prefer a raised nose. Keep within 5-7 mm – extreme angles suggest something more fundamental is wrong with your bike fit.
4. Set the base XC cleat position
For cross-country riding you need maximum pedalling efficiency, so start at the contact point: your cleats. Find the ball of your foot (it’s the middle of the first joint of your big toe) and mark this point on the outside of your shoe. Position the cleat 5-7 mm behind the line. Then, looking at the sole and imagining a centre line running from heel to toe, set the cleats straddling it 50-50.
5. Customise cleat angles
Check that both shoes match by clicking them in while empty and rotating them. Now your saddle height is set correctly, put your shoes on, clip in and make sure your feet run parallel to the cranks. Adjust the cleats to bring the heels either in or out until they are, though if you feel any pain or tightness in your knees, customise accordingly.
6. Choose bar and stem position
It’s important to factor in your flexibility, relative limb lengths and posture here; there’s no one right way. If you have poor core strength and a tight lower back, for instance, a classic head-down, bum-up race position will cause problems and eventually injuries. You’re looking for a relaxed, balanced stance that doesn’t torture wrists, thumbs, necks and bums.
7. Set stem length
If you’ve got a longer torso a longer stem can help provide that classic flat-back race position, but be mindful that it will also transfer more weight onto the front wheel, making the front wheel feel heavier, giving a slower turn-in and making the bike more prone to inadvertent endos. If your saddle is all the way back and your stem is over 90 mm, you’d benefit from a longer frame.
8. Is my bar height right?
For a cross-country race or road position, a large drop between saddle height and bar can increase pedalling performance, but that will compromise handling on rooty, rocky or steep trails – it makes it hard to unweight the front or to lower your centre of gravity. Higher positions work better on techy, rough and fast stuff, but can make the front feel remote if you go too far.
9. Quick height adjustments
Undo the headset bolt, loosen the stem clamp and slide the stem and spacers off. Add or remove spacers as needed. To reinstall, tighten the headset bolt first: put the front brake on and shove the bike back and forth, there should be no play. Then tighten the steerer clamp bolts. For best results, take Allen keys on a test ride and experiment with heights.
10. Get your bar width right
Wide bars give greater stability, leverage and control; broadly, up to 710 mm is fine for XC, while trail bikes are happy with 740 mm or more. Shoulder width plays a great part in what will work; the wider they are, the wider the bar you need for the same stability-creating triangulation. Size your bars personally as you would size a frame, and damn the rules.
11. Set sweep
Loosen the bars so they will, with effort, rotate. Sit (or stand if descending is most important) on the bike and spin until comfortable. If the position dips your wrists a little, your weight will naturally push your palm into the bar during rough-trail impacts, rather than rolling it over the top. Your thumbs should not be uncomfortably pushed back, either. Don’t forget to tighten the bolts to the torque setting!
12. Tune levers and shifters
As with saddle height, for cross-country riding it’s all about maximising efficiency. Use a 4 mm or 5 mm Allen key to loosen the clamps just enough to allow them to move, then sit on the bike. Angle the lever so your hand continues the line of your arm, and push the lever inboard until your index finger falls naturally in the lever crook. One finger’s all you need.
Trail set-up
13. Tune cleats for trail use
Use the cross-country cleat guide in step 4, but slide the cleat further back than 7 mm. This isn’t as efficient, but vitally helps you drop your heels and lower your mass on steep downhills. For flat pedal riders, replace any missing pins as soon as you can – they really can affect grip dramatically, and slipped pedals always suck.
14. Set saddles for aggro
See steps 1-3, but note that even an inch lower gives far greater manoeuvrability, while dropping your heels brings much of the pedalling efficiency back. If fitting a dropper post, lightly grease it before fitting to avoid it seizing. If the post has a remote, zip-tie the cable to avoid buzzing the rear tyre, but make sure it moves unrestricted through the whole travel.
15. Choose the correct trail stem
A shorter stem speeds up steering inputs and gives a more direct feel – great in loose or slippery conditions. They also work well with wider bars, and benefit slacker head angles and 29ers that have a slower turn-in. They also move your weight further behind the front axle, allowing you to weight or unweight the wheel easily and reducing the bike’s desire to cartwheel.
16. Tweak levers for trail use
A cross-country rider’s levers typically end up around 45 degrees from vertical, due to the high-seated position. However, if you use your brakes hardest while crouched low and to the rear-as on downhills-your arms will be closer to horizontal at that point. Raising the brakes to a shallower angle puts them back in line with your arms for the strongest, easiest pull.
Top tips
Torque talk
Torque is turning force, commonly measured in Newton metres (N.m) or inch pounds. Use a torque wrench, either a ratcheted type that slips once the setting is reached, or a beam type that shows the force on a readout. Torque wrenches are vital when working with handlebar and steerer clamps, as over-tightening can crack the stem or crush the bar. This can cause them to fail, and obviously that’ll happen when they’re under load…
Greasy does it
Grease all bolts so they don’t seize. With the right torque setting, you should not need threadlock.
Damage limitation
Nip up, rather than tighten, levers and shifters – if they rotate when you crash, they’re less likely to snap off.
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