Installing a front mech

The front mech is a little easier to do than the rear. It normally only has 2 or three locations and the tolerances are generally greater.

Fitting hardware
The first step is to install the mech. There are 2 types of connecting method used in biked today. Braze on and clamp on. Braze on connects to a pre existing hanger that is supplied as part of the frame. Clamp on has a band that clamps around the seat post. Check your frame before purchasing your group set so that you know what one you require. If you require clamp on ensure that you read the frame specs on torque settings for the clamp. Too tight and you can squash tubes.

Height
The most important step of hanging the front mech is to ensure it is installed at the correct height. You ate looking to get about 1 to 2 mm between the cage and the big chain ring. If the gap is too big the chain won’t shift properly.

Angle
The second important point is to ensure the cage is parallel with the chain ring. Viewing the bike from the back ensure the cage follows the same line as the rings. At the same time view the bike from the drive side and ensure the rear of the cage drops off downwards with the chain ring. Again the more of the cage you can get to flow down with the chain ring the better. Sometimes only the first section fits nicely, don’t stress to much if that’s the best you can do.

Trims
As with the rear mech we have a high and a low setting. These will control how far the mech throws each time you change gears. Initial trim can be done without a chain in place but the final Trimming is best done with a chain on. So without a chain. Or with it pulled out the way, begin to Lind up the high and low position. Start with the small chain ring. This is the mechs home’ position. Using the trim screw, line the center of the cage with the center of the chain ring teeth. Using your hand push it to tr bug ring and do the same. Release it back to the low position and install the cable. Making sure barrel adjusters have been wound tight and then back 2 turns, this gives us play to make adjustments later as cables stretch. Again check manufacturers specs on how the cable should connect and Ensure you have the shifter set to first position it has. Take up any slack in the cable and tighten

Fine tuning
Install your chain and start shifting the front mech. If all has gone to plan you should be able to shift across your chain rings. If you hear rubbing or it does not shift correctly then we need to fine tune it.
Place the chain on your smallest cog on the rear and the big chain ring. Fine tune the trim so you have a gap of about 1.5mm between the outside edge of the cage and the chain. Shift to largest cog and smallest chain ring and then fine tune trim so you have the same gap but this time with the inside edge of the cage and the chain. When tuning the bug chain ring you will most likely have to shift down the back up as the shifter will have to take up the new position and extra cable slack.

Conclusion
Front mech is a fair bit easier than the rear but if positioned incorrectly in relation to the chain ring shifting performance can be very poor. So take the time at the start to ensure you get it right first time

This post is tagged derailleur, front mech, maintenace