HOW TO... FIT AN ISCG-05 CHAIN GUIDE

Single-ring (1x) drivetrains often use a chain guide to help keep the chain on the front chainring. The International Standard Chain Guide mounting system was introduced in 2003, and ISCG-05 is the latest iteration. It consists of three mounting points, spaced 55.92mm apart. Chain guides have a backplate that bolts to the bike frame. At the top of the backplate sits the guide itself, on an adjustable slider. This allows it to be moved up or down to fit the chainring size. Some chain guides also have a bashguard at the bottom to protect the chainring from impacts. To fit an ISCG-05 guide, first lift the chain o the chainring. Check the removal/installation procedure for your crankset. For Shimano cranks, loosen the two pinch-bolts on the non-driveside crank arm, before flicking back the locking chip and removing the preload screw. Remove the driveside crank arm and check for wear on the crank spindle and the bottom bracket bearings (they should feel smooth, not gritty). Use degreaser and a cloth to clean the crank arm(s) and spindle thoroughly, as well as the area where the guide will be mounted. Insert the bolts through the backplate, fit washers on the reverse side (ensuring that the plate clears any pivots/other frame details) and screw it loosely to the frame. Align the plate so that the slider is vertical. Reinstall the crank arm(s) and lift the chain onto the chainring. Fit the top guide. Lower the top guide into position (using markings on the backplate or fixing it 3mm above the chain) and tighten it in place. The chain should run through the centre of the guide – if it doesn’t, you’ll need to remove the backplate from the frame and experiment with washers to get a good chainline. Remove the driveside crank arm again, tighten the backplate bolts so that the chain guide is secured in place and then reinstall the crankset. For Shimano cranks, tighten the preload cap (using a Shimano star tool), flip down the locking plate and tighten the pinch-bolts. Shift gears and check that the chain doesn’t rub on the top guide in the highest or lowest sprockets. If it does, make a note of which side it’s rubbing on and then remove the cranks. Unbolt the backplate from the frame and add or remove spacers, then repeat steps 6 to 8.