Multi-tool for rides

Another vote for topeak mini 18 here, it's really small but well made, though I haven't had to use it in anger yet (touch wood!). I also find the idea of my chain breaking difficult to imagine, but having a spill and breaking the derailleur or hanger (i.e. fixing bike as single speed to get home), that seems a bit more likely to me.

On my vintage commuter/tourer I've got a small home-made case with all the bits I need for it (allen keys, screwdriver, small 12/13,14/15 spanners, patches, levers, chain tool, link, chalk, gaffa) as it has too many odd large nuts and bolts that don't come on multitools. That stays in the bottom of my bag perpetually, as I ride it much more of the time.

Topeak RatchetRocket - http://www.topeak.com/products/Mini-Tools/RatchetRocket - all the hex keys needed, chain breaker. Add a pair of tyre levers and you're all done. If any of the bits are unsuitable for your bike, you can buy ones that are suitable - if you mash any up you can buy replacements.

The way I look at it is, if your bike is well maintained, you don't need to worry so much about issues. Except maybe for tyres then a little kit to replace inner tubes is necessary. Bikes these days have virtually all bolts that are allen head. So a little selection of keys could be useful for something coming loose. I have never had to do anything other than change the odd inner tube and adjust my seat post a few mm.

Lezeyne make some pretty good compact tools. Definitely have one with a chain splitter; any novices will be in complete awe of you as you reconnect your chain! Top tip though; ditch a chain you've repaired on the roadside as soon as possible. I usually find the repair breaks again a few rides later. A Magic Link also gets you going quicker once you've cleared the broken one.

It's not so much the frequency of a chain break that's the issue but the consequences (as well as its unpredictability). If you're riding any distance unsupported it makes sense. Naturally, we'd all be happy if we never, ever need one...

Topeak Hummer, now renamed Hexus II contains all the tools you need in a decent package with decent amounts of leverage on the allen keys.
I have used Topeak chainsplitters to fix and fit 10speed chains with no issues.

broken a couple on MTB's not road - mangled rear mech = stick ? and one on a very bad gear change on a steep hill - [hobbyhorse]reckon 10/11 speed more prone to chain breaks - on sportives seen more riders with broken chains in last few years than last few decades[/hobbyhorse]

suggest looking at the Lezyne range, got given one as a present and now have on each n+1 - stainless steel and various options eg Torx if you run disks and some with the essential chain tool ^^^as above

For those not using things like a powerlink (which I've heard about snapping on a few occasions on this forum), I'm curious as to how many people have ever had a chain break on them?

For the 30-odd years I've been riding a bike I've never broken a chain.

If you're planning to ride anywhere that would be hard to get home from in event of a mechanical, I would take a chain tool. It is not fun to try to put a chain back together with rocks and allen wrenches.

This is the best multi tool you can get:

http://topeak.com/products/Mini-Tools/ALiEN_II

I have one of these:

http://www.decathlon.co.uk/12-function-multitool-id_8302874.html

Everyone in my club comments on how compact/useful it is and when in stock, only costs £7.50 from Decathlon. All the relevant tools including a chain breaker. ...can also be found under another brand name - I'll let you know if I remember what it is!

I've got a few different ones, luckily I've never had cause to use anything more than the Alan keys.

I have a Topeak Mini 18+ and a Park I-Beam 3 and find the Topeak the better of the two, have used the chain splitter in anger on both and the park one just seems too much faff. Plus the Topeak is about 1/2 the size and comes with a neoprene pouch that stops it rattling about.