Why would you want to replace your chainrings? Well, it might be that you’re upgrading them, changing the size, or you might want to experiment with some Osymetric or Rotor rings on the road. If you’re a mountain biker, it might be that you’ve hit them and they’re slightly warped. Or for any chainring, it might be that you’ve used them a lot over time and they’re starting to get worn. You can tell that if the teeth are starting to get low, although do bear in mind that a couple of teeth, even when new, are quite low because that aids the shifting from one chainring to the other.
So, in this video we are going to show you how to change the chainrings. For the majority of chain sets, all you need for the job is a 5mm allen key and one of these specialist tools, which you put on the back of the chainring bolts to prevent them from slipping when you’re both loosening and tightening them. Although for some modern chain sets- modern Shimano ones and also some Campagnolo chain sets- they are using these torx bolts, which are a slightly more star-fangled thing, and that reduces the chances of them being rounded off as you loosen and tighten them.
We’re going to start with a fairly standard Shimano mountain bike chain set. With this one we need to start with the inside ring because the teeth of that partly cover the backside of the outer chainring bolts. Undo each bolt, a little at a time, using your 5mm allen key. You can do the last bit by hand, putting the bolts safely to one side. Once you’ve taken the last one off, the chainring should come away from the cranks. Make a note of which way around the chainring was mounted. For this one, we need to use our special tool to prevent the bolt on the other side from moving. Again, undo each outer bolt a little at a time. On this particular crankset, there are also some crank arm tabs which you will need to keep safe. After, all the bolts are removed the chainring will come away from the cranks. Before you replace your chainrings, clean each of the bolts using some degreaser and then apply some fresh anti-seize paste.
To replace your chainrings, start with the outer one. Marry it up to the holes in the crank spider. There is often a small tab on the outer chainrings, which needs to go in line with the crank arm. This prevents the chain falling between the ring and the crank. Then, put one of the chainring bolts in, doing it up by hand. Then do the same with the opposing bolt, and then the remainder. Next, use your chainring bolt tool to hold the back side of it still, and tighten the other side using your allen key.
Repeat this for each of the other bolts and then finally go over them all again to make sure they are tight. Next, we can put the inner ring on. Generally, any writing on the chainring should be facing you as you put it on. This will make sure that you have the ring on the right way around. If you don’t have any writing, try looking at the teeth of the chainring. One side of each tooth should be steep sided, and the other a little more slanted. It should be the steep side that pushes against the links of the chain as you are pedaling forwards. Put the bolts back on and tighten each a little at a time, going around again at the end just to make sure they are all tight.
Here, we’ve got a 2012 Ultegra chain set which uses the torx-style bolts. To remove the chainrings on this, all we need to do is loosen the five bolts. As ever, undo each a little at a time unit you can take them off by hand. Once the last one is out, you will be able to remove both the inner and outer chainrings. Before you replace or renew them, clean the bolts using degreaser and then apply a small amount of anti-seize paste. To put the outer ring on, pull the crank arm through it, and make sure the tab on the chainring is sitting behind the crank itself. Then put the inner ring on, making sure that any writing is facing you as you do it. Start one of the bolts by hand and then do the same with the remaining ones. Then start tightening them properly using your torn tool. Rather than going around the chainring, tighten opposing bolts a little at a time, and once they feel tight, go around them one final time just to make sure. Then you are ready to replace your cranks.