After a year of commuting Mr Foldy has a catastrophic puncture. I came out to it after work. I don't know how it happened, but there are several 1/2 inch slashes in the side walls of the back tyre. Both sides. It was a Schwabe Marathon, on a Dahon MU.
Anyhoo, its the one thing I've been dreading. I'll have to take the back wheel off, obviously, and maybe buy a tyre and a new inner. Thing is, I have no experience with this stuff and my LBS would bleed me dry. Are there any clues about whether the tyre needs replaced? There is certainly loads of tread on it. Do I need to buy rim tape for a replacement tyre? Are there any do's and don'ts with getting the wheel on and off. And worst of all - until I fix this, I can't ride it!
Any advice, sympathy or jokes at my expense would be gratefully received.

Definitely replace both tire and tube. Depending on the rim tape that's on there it may not have to be replaced... old style rubber 'tape' breaks fairly easily, plastic or cloth will fare much better and will most likely be OK.

Shame on you, you haven't been practicing your flat fix technique? Also, what does your LBS charge for replacing a tire and tube? Any place I've worked we charged no more than $5 for the labor because it's a procedure that takes a couple of minutes at best when you're used to doing it.

What model Mu is it? Internal gear hub, or rear derailleur? You might be able to do a search on here and find a thread covering how to remove the rear wheel.

The place near me charges $20 to replace a tube.

According to sheldon brown's article on tyres, reasons for changing tyres are:

1. "When the tread is worn so thin that you start getting a lot of flats from small pieces of glass and the like, or the fabric shows through the rubber.
2. When the tire's fabric has been damaged, so that the tire has a lumpy, irregular appearance somewhere, or the tube bulges through the tire."

Further the article says:

"Cracks in the tread are harmless. Small punctures in the tire such as are typically caused by nails, tacks, thorns or glass slivers are also harmless to the tire, since the tire doesn't need to be air-tight."

https://sheldonbrown.com/tires.html

I replaced my rear tyre recently for reason no. 2 :-/

Cheers guys. My LBS wil want £12 which I think = $20. They will mark up on the tube and the tyre though. Above posts make me realise i will need both. The tyre did have a couple of bulges and the tube has several punctures. Rim tape seems like a good idea. I did some youtubing last night and the whole process doesn't look as bad as I feared. Worst thing is that Im now on a bus bored while Mr Foldy mopes at home....

Erg79 - its the Mu P8. The research I did last night suggests this might be simpler than hub gears. Fingers crossed.

So you've got a rear derailleur then? Google images of the P8 show derailleurs.

Anyway I've only ever had to change tyre by dismantling my Nexus 3 hub. Not a difficult operation at all. Then again this may be hub specific.

I never repair tubes, £3 each.
I might repair some for spares sometime, but proberly not.

I would worry about what happened to the bike! Is there no way you can bring it innside at work?

Hey Bad M. You are right and I really don't like leaving Mr F outside. I can't get him into my building though. On the plus side he is chained right outside and the security guards watch him all the time. The tyre is really shredded in several places, but I'm pretty sure its not vandalism...... Maybe I rode over a crocodile!

Then it must be the security guard (unless it is the butler..)

I have Marathons on my white folder so I know the tyre. I think it is always good to try to find out why it happened- to be able to avoid it happening again. Did you ride wit low air preassure or is the tyre just old? Like BNB said it is always good to practce when you can do it at home, in the weekend and in the daylight so you are not cought in a nasty situation.

Now that you mention it I did do a mile or so on really low pressure at the start of the year. I probably wrecked the tyre at that time. I'll certainly get some practice changing tubes and tyres now! I'll probably start carrying a spare tube and tyre levers from now on. The new stuff should all arrive tomorrow and I can get mobile again!

Are you sure the sidewalls are slashed and not just cracked? A picture would help. It is quite normal for a tire to look horrible when it's flat, because the fold of the sidewall will open up all cracks that you don't even notice when it's properly inflated.

I changed it all out last night. Was easier than I feared. Thank you tyre levers! Biggest faff was hooking the brake caliper back together. It comes apart easier! Thanks for the tea and sympathy and tips over all this. Im happily back on the road. If i can look the old tyre out I will post a pic. My suspicion is that a few miles on unnoticed lowpressure maybe damaged it. The reflective strip got very tattered. Cheers!

knowing how to fix a flat 'on route' is right up there with knowing.....just about anything! View an instructional video on "you tube". or buy "Anybody's Bike Book" ...& learn it in less time than it takes the bus to arrive.

Thanks kraftwerk. I agree with you that its a "must know" thing and I am happy to change a tube/tyre anytime now. I cycle with a spare tube rather than bother with a repair on the go. I don't like messing with the bike where there is even a tiny risk of messing it up, but it really was an easy job when I made myself do it!

This. If you don't figure out what happened, you have a higher chance of another flat tomorrow. Unfortunately, too many bike shops DON'T bother to locate the problem. I've had three flats repaired at bike shops and every single one reappeared within 1-7 days because the shop did not find the problem.

But don't get me started on having to re-do work I've paid bike shops to do...