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22 Apr

Bike fitting

Posted by Bold Apps

This is a guide for home bike fitting. It's a service that I no longer provide due tine constraints. This guide works for all road bikes, MTB's e.t.c you know bicycles. This guide avoids the usual methods like kops which if used in isolation end up confusing the fit rather than enhancing it. Bike fitting is a process and you cannot start in the middle then to the begining and then move to the end. Follow the guide as I lay it out and it works. You may also find you dont need that new saddle after all. 


Bike fitting is pretty straightforward. All bike fitting start it must start with the saddle

Step 1 now level that saddle off with a spirit level. Some saddle have a shape where a spirit level is useless you can either change your saddle here or use your eye. Tilted down a couple of degrees wont hurt (old shimano seatpost only allowed your seat to be nose down slightly) but you might slide forward a bit. Nose tilted up is never desirable.

Step 2.
Now set your saddle height. This is measured from centre of bb axle to the top of the saddle. Once this is determined this is fixed height for all your bikes. The saddle height is the single most important thing to get right which is why it has to be done first. The lemond method takes your inseam measurement (taken with a book jammed into your crochet and a tape then dropped to the floor) and multiply it by 0.883. This is your saddle height but it only a start. It may have to go up or down a bit. The weakness here is crank length. It takes no account of crank length with 20+ bikes with cranks from 165mm to 177.5mm my saddle height has to vary a bit by a couple of mm from bike to bike. For me its 795mm. Correct saddle sort many knee issues out.

If your hips rock alot or you have dip your foot at the bottom of the pedal stroke then your probably got your saddle too high. Let your legs dangle when on the saddle. The angle your lower leg make to your upper is not far off the how your leg should look at the bottom of the pedal stroke. You can do this bio mechanically without measuring anything. I know the how your leg should look by eye. You may not but you can set your saddle height by raising it till your hips start to rock when pedalling. If there is more than 2cm of movement left hip to right hip then your saddle is too high. That's not an exact measurement but your hips should not be rocking. Your foot is another tell tale sign. When pedalling the tow of your foot should be pointing up a bit, like your scraping shit of your shoe. Whe your saddle gets too high you toe no longer does this so stop raising your saddle. Between these three observations the saddle can be set. Once it is set correctly, measure it.

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Step three. Sit on the bike and pedal. Do this for a minute of two until your settled. Note how far back your bum is. Your bum should be at the back of the saddle. Adjust saddle for and aft till your bum is at the back of the saddle when pedalling normally.

Now that's the saddle set. Dont alter it. This is fixed unless your leg length changes. Most saddle comfort issues are addressed by proper positioning. Saddle choice is often affected by position and clothes worn. Harder saddles work well for long rides with padded shorts. Soft saddles are fine in civies and shorter journies. The more upright your position the wider the saddle can be. The flatter you are the narrower the saddle needs to be. If proper position does not help you your saddle has to be changed.

Now to the front of the bike. When one is sitting on a bike you should really feel like your in it. This means something specific in terms of position. Your back should be straight
Not ruler straight as backs are not like that but you should not be hunched or have an excessive curve in the upper half of your back. You should feel relaxed. Your arms should be slightly cocked on the tops, hoods and drops. Your arms should also be perpendicular to your torso. If that arm to torso angle is greater than 90 dgress your probably over stretched and the shape of your back will show it. Your shoulders should not be pushing back out of your back. This leads to bunching. You end up cranking your neck then. Essentially imagine your standing then bend over,that how your back should look. Your neck then sorts its self out. To achieve this position you have stem length, rise and bar reach/drop to sort alter.

You can take any position from upright to flat and makes an arc because you arms in all cases are only slightly cocked I.e a relaxed out position. Even if you think your not flexible you dont have to have the bars higher than the saddle. That's for upright positions. Upright right positions are not more comfortable. They are used or should be for improved visibility. This is important in urban areas. Hense riding tt bikes in cities is not always wise. That old trek bike below is mine. I cant get within 15cm of my toes when trying to touch them yet I consider that position on the dirty old trek to be conservative. Lacquer is peeling but it works hand that all that matters really. It's also offers a comfortable position for 200+ mile rides. Again its comfortable well as a comfortable as a alumium bike is with 22mm tyres that is. With proper position you can adopt a range of positions on the arc your body shape allows. You can of course ride in a more upright position it's perfectly fine if it's on the arc of acceptability.

So step 4.

Adjust your bars so the drop ends are parallel to the ground. Tilted up a bit is acceptable. Exactly how they sit will depend on your shifter brake levers. shifter/brake lever position should lever a flat area for you hands with modern unit. The bar tops to the levers are essentially flat. When levers are pointing up to bring them closer that a sign that the bar reach or stem length is too long. This also has the effect of putting stress on the wrists as they are no longer in line with your forearms. Perhaps the steerer has been a cut too short, in other words parts should be changed. Old bikes with old brake levers dont give you this luxary. Your meant to sit in the drops and brake from the drops.

Select your bars so you can sit with your hands on the tops,hoods and drops and operate all the controls without you shoulders pushing back, arms straight but slightly cocked and you should feel relaxed. If your too flat you'll feel it. I get pain around my hip and crotch if I am too flat.

Stem length is picked to complement the bars. Stem angle is the last main thing. Stems come in different angles. Commonly road bikes have a negative angle stem so with commonly used head tube angles. They can be either way up and flipped they raise the bars but shorten the stem. 82 to 84 degrees angle is common. 0 degree stems are neutral. They are the same flipped. Stem with rise will pull the bars in as they lift them. So be careful your not creating undue bends in your arms. The higher the rise the shorter the stem is effectively.

You can also lift the stem up which was easier on old quill stems. Given the head tube angle lifting the stem up means pulling the bars back so stem length may have to alter.

Most of the problems start with position when the rider feels uncomfortable and starts altering the front end in a haphazard way often making matters worse.

That's the basics it can be done at home. The approach has to be methodical.

Of course it helps to be on a frame that is sized so you can make it fit.

 




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