"Removing your rear derailleur to clean it could result in cross-threading the derailleur hanger when reinstalling if you are not careful and if your bike does not have a replaceable derailleur hanger (mine doesn't), you are in some real trouble."
Here's what I've said in the guide;
"To re-fit, hold the mech as per the photo to ensure that the body adjust screw has cleared the mech hanger stop. Take care when re-fitting the derailleur that you're matching the threads with the mech hanger. If threading feels tight, back it off and try again; it should thread on easily until you torque it up at the end of the thread."
If you've read the short note I added about buying and using tools, you'll have seen that I've mentioned the risks involved in doing your own wrenching. However, the more you do things the less likely it becomes that you'll mess something up. We all understand this, it's why so many people take their bikes to a shop to be maintained; a) the risk is with somebody else; and b) they've made their mistakes way back when and are less likely to muck up on your bike. I say 'make your own mistakes, just remember to learn from them'.
Computers and bikes are very poor at supplying each other with analogies. If I only defragment my hard drive every ten years, then it's going to take me a relatively long time to do the defrag when I do do it, but it'll be done all the same. Maybe even some computer expert will come along and do it quicker, or offer a better alternative, but the end result will be the same physical component doing the job. If I don't clean and relube my chain it'll work for a few months and then it will fail. When I say 'fail', I mean that it will never work again, it will be 'worn out', it will cease to be effective. Nobody can fix it. In that same period of time, my rapidly wearing chain has been rapidly wearing my cassette, my jockey wheels and my chain set. Same as the chain, when these components have physically worn away, they have to be replaced with new ones. Have you ever priced out even a cheap complete drivetrain? Obviously, components have to be renewed periodically, but the reason for my guide is to assist people in getting not only more from their components, but also in getting more from their riding as a result of not having to stop every few miles to adjust cack-filled componets, or becoming frustrated that their shiny new chain is spinning like crazy over their worn out cassette whenever they try to climb a hill.
I can't give people the confidence to start pulling their bike apart and putting it back together to keep it running sweet, they have to develop that for themselves. But they're never going to get that confidence, or the knowledge and experience, if they're just too darn afraid to try in the first place. What I can do is show them how I've done it, if for no other reason than to show them that it can be done by yourself, and relatively simply, too.
The guide is there because enough people asked for it, so there are (thankfully) enough people who are at least willing to have a go at doing their own wrenching. It's true that some of them will thread stuff (or worse), and that some of those incidents will be more costly than others, but so what? I've bust stuff, (I've only been doing this for a couple of years, by the way), plenty of stuff, but I've never done the same component or bolt twice.
My only advice to folk would be; do it carefully, but do it all the same. I think that that message is clear throughout my maintenance guide.
As I've said before, I welcome any constructive criticism and I welcome any information that would add to the effectiveness of the guide. I don't think that suggesting people don't even try would fall into either of those catagories.
Sincere regards,
Steve
PS I will make an addition to the guide which will cover the breaking/closing of a chain which doesn't use a Powerlink, thanks for pointing that out.