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Replacing A Front Derailleur |
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Mountain Bike Surgery -
Derailleurs
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Written by stumpy_dan
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Hits 1027
Tuesday, 27 November 2007
Derailleurs Front:
A front derailleur needs to have the right clamp diameter to fit your frame, cable routing (top or bottom pull) and swing (top or bottom). Most Shimano MTB derailleurs have multi-fit clamps and will operate with cable pulling from top or bottom.
Top swing
derailleurs have the clamp below the cage, bottom swing ones have the
clamp at the top. Which of these you require depends on your frame so
it's best to copy the one you already have.
Tips
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Check out your current set up first before you buy anything.
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Before you start helps to take a good peer in as to how it all fits together and whereabouts everything is positioned on the frame as likely you will look to replicate the relative positioning (this was my justification for not cleaning my bike as dirt is a great guide for where things used to be;)
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Use the manufacturer guidelines. Everything else is supportive.
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Tools used: an Allen key set, a spanner, some lube and and some great John Lee Hooker blues....Nothing Ifix is quick.
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Really helps when doing this to take your back wheel off.
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Undo the cable from the derailleur at the start but have a good look how it went in. There are two types ( I know of) a) From the top and b) Normal (sort of the bottom!)
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Before you remove the derailleur you need to lose a chain link temporarily so when you undo the derailleur bolts it can get free of the bike. I do this later in the video as my derailleur had split in half so the chain slid through it easily.
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Now it is time to connect your lovely piece of kit. Try and match up positioning and ensure you don't remove the Pro Set Alignment Block (not just yet). This helps you measure the relative positioning of your bits and bobs. (Check manufacturer instructions here)
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Check out your frame post width. It may be if a thin one you will need to use an adapter to fit around the inside of the clamp to make it fit. I didn't but this is really common place and dead simple. You should check this out before oyu buy and make sure it is multifit so has adapters for all the frame sizes. You can tell once you put it around the frame or you can check your manufacturer manual for which size frame and hence adaptor you will need.
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In terms of Torque again check your "destructions" but mine said 5-7 N-m (44-60in. lbs). This is secured using a 5mm Allen key.
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In fitting the level section of the chain guide outer plate should be directly above and parallel to the largest chainring.
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I changed my cables as they were worn and I needed a bit more length. Once you unplug these from the frame they slide out from your gear levers.
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Keep a good amount of length of cable (bit of excess you can cut off later is fine)
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Follow the cable through from the gear lever entry point and through the old casing or if using new casing use the old ones for measurement. More detailed stuff on this follows.
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The adjustment is black magic.
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Low adjustment. First remove the pro set alignment block. Next set so that the clearance between the chain guide inner plate and the chain is 0-0.5mm
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To connect and secure the inner cable.. operate the lever 2 or more times to set the lever to the low position. After removing the cover, place the end of the cable onto the hook. In this condition operate the lever 2 or more times to set the lever to the top position and then pass the cable through the outer casing adjustment bolt and pull the cable all the way through. After this operate the lever to set it to the low position and install the cover.
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After taking up the initial slack in the cable - re secure to the front derailleur either top or normal way
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Top adjustment - set so the clearance between the chain guide outer plate and the chain is 0 - 0.5mm.
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When carrying out adjustment of the intermediate chain ring, set the chain to the largest sprocket and at the front set the chain to the intermediate chain ring. Adjust using the outer casing adjustment barrel so that the clearance between the chain guide and the inner plate in 0- 0.5mm
Go out and ride.
Useful Links:
Park Tools
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enjoy your ride!
