The transmission of Mountain biking – Technical guide to mountain biking

La trasmissione della mountain bike è formata da componenti meccanici che trasformano la spinta delle gambe nella rotazione delle ruote, and are part of: Crankset, chain, cassette and freewheel, Central rear derailleur and front derailleur.

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The rear derailleur

An exact adjustment of Exchange reduces the risk of release of chain, and improves progression legs effort break the pace because of a changed too slow.

Adjusting the rear derailleur is done in two phases: bottom hose stop and cable tension. Bottom-adjustment is made by turning the screws above the graft of the cable to the derailleur body: These force the Exchange to move between two fixed end points that prevent chain output 1. With the shift on the largest sprocket turns the screw marked with the letter L (Low) to align the upper guide pulley with the pinion gear. Same goes bringing the change on the smallest COG, but this time it will act on the screw marked with the letter H (High).


The gearshift control cable tension adjustment happens so: you start by screwing the screw registers on the shifter and handlebar control and carrying the same on the last shot (the smallest COG). From this location, loosen the Allen screw that locks the cable to the derailleur and check that this is tense, by pulling the end and tighten the screw. At this point begins the actual adjustment by turning the adjustment screw on the body where you change gear cable. Starting from the smallest COG on which we had positioned the shifter, We operate the command by one click to insert the pinion while the largest contiguous turning pedals rather slowly to test the best shifting speed: If the change effort and seems to grind scrap metal, the cable is too slow and to stretch it turn the adjusting screw on the gear of one-quarter turn clockwise and repeat the operation. When we feel that the change goes smoothly on the sprockets way way more, you need to check that the cable is not too tight as to prevent shifting on the sprockets children: If that happened, you have to loosen the cable by screwing the adjusting screw in a clockwise direction. Optimum adjustment is obtained with a good compromise between speed of ascent and descent gear, remembering simply that if the change effort to rise you must tighten the cable, If you struggle to get off you have to loosen it. Another adjustment is that of the spring that closes the change on the sprockets, and whose record of pre-charge is near 1 gear attack on dropout. Mount the chain on the smallest chainring and the largest sprocket, and turn the crank backwards. Turn the adjusting screw to position the upper pulley as close as possible to the pinion but without touching it. Verify that even with the smallest COG pulley not touching. By loosening the set screw nears the pulley to the cassette, screw the strays.


If you are unable to achieve the right balance as you adjust the Exchange, There could be problems in the smooth running of the cable along the way (by shifter, along the sheath, until Exchange), so the shift return spring fails to overcome the friction of the cable and when we climb out of smaller sprockets the gear is not responding ... in this case should lubricate the cable in step inside the sheaths (operation should still occasionally), the pins of the parallelogram derailleur, and check that the tubing that leads the cable from downtube to return you long enough (about 30 cm): Beware that if you possess a teflon coated cables (Sometimes they're Black externally) do not absolutely lubricate them and that the cable clamp on the exchange the cover should be scratched for better grip.

Even Avid Rollamajig type of pulleys allow you to greatly reduce the friction at the crease making sheath for the gearbox and this helps a lot owners of rotary knob Grip Shift type commands or Sachs. Remember that the liners must be hard round wire type, not rectangular like girdles as a brake which must respond to another type of solicitations.


Formula for determining the gear stick lengths

When you buy a new bike the problem does not arise because the change has already been mounted so it will work properly with the other components of the transmission, But if we wanted to replace the gearbox or modify the esoteric transmission aftermarket components (Titanium or sprocket teeth chosen by us, tubular steel Crankset with integrated bottom bracket axle, CNC machined from billet rear or front derailleur ...), c’ is a criterion to determine the exact length of the balance of Exchange:

(Senior Crown + larger pinion) – (Crown less + smaller pinion) = Changed.

On one side of the change should be given the capacity to changed, and you should also check that the maximum acceptable pinion gearbox, (following value always on one side of the Exchange), is equal to or greater than the set of teeth of your largest sprocket.

Central front derailleur

Front derailleur adjustment is similar to that of Exchange, and in fact it always acts on bottom screws and cable tension log. First off though, You should check that the derailleur is properly installed on the frame: the walls of the cage must be parallel to the crowns, and that with the front derailleur on the plant Crown the distance “Coronal teeth – lower bound of the cage” both on the 2-3 mm.


Brought the handlebar control on the last shot (minimum Crown or “small frying pan”), loosen the cable clamp, you screw the cable tension on the handlebar register command to check that the live wire by pulling the end and refastening the screw. Now we set the bottom-course trying to tighten the screws until the front derailleur takes the frying pan and the Pan: This always to avoid the exit of the chain. Once this is done, you insert the central command, and verify that it snaps match the sudden ascent of the chain from the frying pan to the Central, otherwise we tend the cable by loosening the cable on the handlebar control: When the “Central shifting” is satisfactory, you check that using extreme chain pinions behind does not touch the interior walls of the front derailleur cage. If this is the case with the largest sprocket, loosens the cable, If it happens with the smaller one you tend.






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