Originally Posted by andr0id

If you do a good weekly check/clean then you don't need to carry a tool except to help others in need.

I carry 2 tubes, 2 CO2 cartridges, 1 tire tool and an inflator head and have only had 2 instances in the last 10 years where I've not got by with that. Both involved busted chains, so I would have needed a multi-tool with a chain tool and a spare link.

In our group rides, there are usually a few people that feel the need to bring an entire bike shop with them on their backs though.