We carried a folding spare on the first trip (Bike Fridays here too). No flats with our Marathon Pluses so it hasn't come with us on any subsequent trips and my tires have thousands of miles on them and still going strong. No flats on three different trips and only one on Bruce's bike which was a tube failure, the tire was fine. This was on mostly paved roads in SE Asia but includes Myanmar where the roads are made out of rocks and tar with potholes and cracks you can lose small children in. I wouldn't pack a spare again, but if you are using a sag wagon then perhaps you might as well, if it gives you peace of mind.

Some more info on my last Walmart replacement tire:

From my crazyguy reports
Western NC to Central FL and back on a Giro
By Mark Boyd ★★  
from Day 9:

When I was about 10 miles from MacClenny, I crossed the road to a place where I could take a break. I stopped in the road, got off - this was mostly a butt break - and walked the bike across the road. It felt like the rear tire had developed a lump. I checked but didn't see anything obvious so I rode on. The lump became a side ways fetch for every turn of the wheel. That felt like cord damage to me and I started thinking about how I would replace that tire.

I did have a spare tire with me till the day before yesterday. Then it disappeared. It was there before I stopped at McDs for lunch and gone two hours later when I stopped for a break. I don't know if it was taken while I ate or fell off later.

I figured correctly that MacClenny would have a Walmart but would not have a bike store so my only tire source would be Walmart. l lucked out in that it turned out that it was possible to walk from my motel to the Walmart. Not easy, but possible. l found that out from a fellow who works at the McDs where I stopped for a snack and net access. The nearest bike shop near my route is in Gainesville - one day away - and won't be open till day after tomorrow since this is Saturday. The Walmart Super Center is one mile away via a closed road that can be bicycled. I decided to walk there after I checked in at a motel near McDs.

Once I was in my room, I checked the tire carefully. Something had slashed the sidewall deeply enough to damage the cord structure, so it was not repairable.

from Day 10:

The trip to Walmart was successful but took almost two hours. Part of that time was due to a wrong turn which added half an hour walking on a dirt road and exploring paths into a woods. I found some neat places to stealth camp, but couldn't get through to Walmart. I also picked up a lot of burrs on my socks and knickers and noticed that one of my shoes was torn. The route on Barber Rd, included a blocked off bridge over a creek. It was passable on foot, even carrying a unloaded bike, but not with a recumbent or a loaded bike. I mention this because Google Maps wanted to route me over it on the way out of town.

I started by partially unloading my bike. I really only needed to remove one pannier, the rear one on the drive side. It actually is easier to remove and space the rear wheel with the the other panniers still on the bike. Just lay the bike on the non drive side panniers after loosening the quick release and the brake. Thanks to my bad experience with Marathon Plus tires, I had lot of practice doing this by the side of road, and it is just as easy to do in motel room that has enough available floor space. Although my motels breakfast was lousy, the room was large.

After I removed the wheel From the bike, I carried it to the bathroom to do the tire swap. I wiped down the tire and the rim with toilet paper to minimize the dirt that would get on my hands while i worked and I used the clean water in the toilet bowl to wash my hands with soap when they did get dirty. My objective, which I did achieve, was not to get anything other that the water in the toilet dirty.

Swapping the tires went smoothly. The new tire was smaller than the old one so the tube, which I did not replace, was a tight fit. It also took some work to get the bead, which is folding, over the rim, but I didn't have any real problems. I was finished by 10 and packed and out of my room by 10:30.

I inflated the new tire to a much higher pressure than I used in the old tire. While Marathon Supremes and Conti Travel Contacts have very flexible construction, Walmart tires don't, so they would have a much larger rolling resistance at low pressure. On the road I really didn't notice much change in the feel of the bike.

from Day 11:

Yesterday, when writing about my Walmart tire, I said that I'd pumped it up to a higher pressure than I'd used with the Marathon Supreme because I thought it would have high rolling resistance at low pressure. I was right about the rolling resistance, but wrong about the pressure. Last night I used a car type pressure meter and discovered that I'd badly under inflated it. It was at about 25 psi! I inflated it to about 60 psi and instead of being stuck at 8 mph, I was able to average 9.5 mph today. That meant a 6.25 hour riding time to cover 60 miles today. At 8 mph, it would have taken 7.5 hours. I got to Silver Springs at 5 PM instead of 6:15 PM.

Thanks Mark.

Thanks Andrea.  If I had a support vehicle the decision would be a no-brainer: the spare would come along for the ride, for certain.  But I'll be doing all the stuff-schlepping myself, on the bike.

As you've seen from the thread, opinions vary.  Some do, some don't.  For me, it may come down to a "How confident do I feel right now?" moment as I am making the final packing preparations.

Andrea and I don't even think about bringing along an extra tire anymore.  Maybe we have simply been lucky but I believe that Marathon Plus tires are bulletproof.  We have ridden them over all sorts of trash (not to mention really rough roads made of sharp rocks) all through SE Asia and have never had anything go wrong.  Baring a unique and strange occurrence that would slash any tire, I would say that you could be completely worry free for a minimum of 2500 miles and probably twice that.  Also, I have always been under the impression that if we ever did need to buy a new tire in a small town in, say, Myanmar, there are always kid's bikes galore and aren't they usually 20 inch?   

I don't carry a spare tire for my Dahon Speed TR. I have (blind? foolish?) faith in them to last.

Yes I usually did back carry a spare tyre back  in ancient times when international cycle-touring was possible.

My wife and I have 20” Bike Fridays.  On most tours I packed the lightest, smallest 20” tyre I could buy as a spare. Enough tyre to get us to a town.  I never had to use it.

Whether I carry a spare tyre is determined by how likely it is I could easily source a replacement tyre, and what the consequences would be of unfixable tyre damage. Hence any tour involving remote roads days from towns, I carry a spare tyre.

An alternative is to carry a tyre ‘boot’ and be capable of repairing a major cut or blowout of the tyre casing.

Graham said: "An alternative is to carry a tyre ‘boot’ and be capable of repairing a major cut or blowout of the tyre casing."

Part of my standard kit, always on the bike, is a collection of Tyvek strips maybe 2 inches by 12-15 inches.  In the event of a sidewall failure I can wrap the inner tube in the Tyvek, basically creating a small section of localized "tire casing" that's good enough (I hope) to limp to a source of new tires.

I've also heard of people who carry a 6 inch chunk of actual tire for that purpose.

My favorite technique in this regard is one told to me over breakfast years ago by Bob Anderson of Massachusetts, a blogger on a former site who we met in a BnB in Carlton.  He once experienced multiple flats on a lonely road in the Snake River Canyon, and finally made an emergency repair by lining the inside of the tire with a $20 bill.  When he pumped the tire up again the tube exploded, creating a cloud of cash confetti.  he gathered up the scraps, and when he returned home he took them into a bank and redeemed them for a fresh bill.

Hi Graham

I carry a tire boot, or rather two or three of the Park Tool ones, on each bike, including my carbon road bike that doesn't go touring.  Had the bit of glass I pulled out of its tire gone through to pop the tube, I would have put the boot in when I replaced the tube.  As it was, I put the boot in at home to spread the pressure over the weakened bit of my almost-new tire.  It's on the rear so not as dangerous, imo, as if it were on the front.

Neither Al nor I have ever carried a spare tire, but then we've never toured anywhere particularly remote.  Al had to replace a tire on our 2019 tour in France; we had some Park Tool boots and some currency, but nothing was going to fix that particular failure.  I described it in my journal from that day.

Al's wheels for that bike (he did that tour on "loaner" wheels since the ones he'd ordered hadn't arrived) and my newest bike have tubeless tires, which we really like.  I've added a curved needle and superglue to my touring repair kit, along with some plugs.   On tour I have dental floss but I'll probably add some extra-strong thread before the next trip.  These will theoretically allow me to stitch up a hole too big for a plug so the tire will contain a tube (I carry one) or even hold air if patched and sealed.  I hope never to have to test the technique, though.