[Edited: the original post had 16mm, it should be 15mm...]

Hello,

Our family bicycles recreationally. We have an old mountain bike, an old cruiser for my wife, and two kids' bikes. To be able to take off a wheel, pedals, or to adjust handlebars or seats on either of the four, I need five wrenches -- 13mm, 14mm, 15mm, 1/2 inch, and 9/16 inch and a 6 mm Allen key.

Is there an alternative tool I can take when we go riding or am I stuck carrying a stack of wrenches with me?

-Dmitri.

P.S. I searched on-line for bike tools, but none of the multi-tools seem to have the right combo -- and none(?) have 15mm or 9/16 inch in them. I guess this is because these tools are geared towards more modern, or "professional," bikes?

Seat post clamp bolts are easily replaced with quick-releases.
The 9/16 could be taken down to 14 mm easily with a modest amount of grinding skill. The 1/2 and the 13 mm are close enough to work with the same 13 mm wrench. Or the same application of grinding skill can turn the 13 mm to a 1/2".
A little more application of a little more grinding skill will turn 13, 14, 9/16 and 16 mm into 1/2".
Or buy wrenches, cut them in half and ask someone to weld the desired halves together. Maybe first take the 13 mm nuts to 1/2", and the 9/16 to 14 mm. Then make custom wrench that's 1/2 at one end 14 mm at the other.

For recreational rides with the family, I'd suggest adjusting everyone's handlebars, seats, and pedals(?) before leaving for the ride.

Thanks for those ideas, dabac. (And sorry for the typo in the original post: it should be 15mm, not 16mm -- typo!)

Grinding is likely out of the question, as I have about zero grinding skill... and the 9/16 inch is the size I need for the pedals on the mountain bike. However, I can probably replace the 14mm nuts (on front wheels of two of the bikes) with 15mm nuts -- this will drop requirement for one wrench!

This is true: I don't see myself having to take off pedals

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They fit inside my bag on the back rack along with a set of tyre spanners, three inner tubes, two cycle locks and the occasional Cat.

Adjustable wrench perhaps?

get a tool roll to keep them in. it can be as simple as rolling them up in a garage rag.

Good bicycle maintenance is the key. I ride 4-5000 km per year, most often with friends, groups of 8 to 12. I cannot remember the last time I needed a tool for my bike, the last time I used my tools it was for someone else. If you need a pedal wrench on the road, shame on you, you haven't taken care of your bike. By far, the most common on the road problem is a flat tire, trailing far behind is a broken chain.
You should never have to adjust handlebars or saddles out on the road if you are taking proper care of your bikes

What's wrong with a 6" adjustable wrench?

+1 I carry a 6 inch crescent wrench. I have never had to use it on my bike, but have stopped and fixed several other bikes for people that carry nothing.

often pedals take a 15mm wrench no thicker than 1/8", or a 8mm hex 'allen' wrench.

packing to ship a bike means taking off the pedals, then putting them back on..

A six inch adjustable crescent won't fit anything on my bike, and it's almost 40 yo.

As for the OP.... I can only agree with those that ask, why are not all those things they mentioned already set before the ride?

There are many compact tool kits for bicycles, if the OP feels that one is needed to carry, then pick the one that has the tools in the sizes that fits the bike they ride.

...the 6 inch ones with thinned jaws fit a lot of stuff a regular crescent won't, like headsets, etc.

One can do a lot with a quality adjustable wrench.

Most pedals use 15mm wrenches, although some are close enough to a "standard" wrench that one can sometimes use one in a pinch.

There are several metric and standard wrenches that are close enough that one can frequently use either one.
13mm and 1/2" are very close.
3/4" and 19mm are also very close.
As mentioned, most pedals take 15mm, but I think I've used 9/16 to remove them in a pinch.

Also, as mentioned in another thread, many pedals can be removed with an Allen wrench.

Anyway, find a quality adjustable wrench (not those cheap China/Taiwan ones from 20 years ago). Either a good Made in the USA wrench, or perhaps a good quality newer one. Perhaps also get two, one for each side. Even Vice Grips can be handy in a pinch.

Evaluate what you'll likely need to be adjusting on the road. Cone Wrenches? Hub Bolts? Do you really need to remove pedals? Is your wrench narrow enough? Perhaps a multi-spoke wrench. Also throw in a chain tool, or a multi cycling tool including a chain tool. Brake and brake pad adjustments? Derailleur Cable adjustments?

I don't see any smaller wrenches in your list, 8,9,10,11mm? Again, a reason to have a good adjustable wrench.

Just make sure you get a metric crescent wrench

One tool to rule them all...

You do mean a metric adjustable crescent don't you? I guess I'll need to buy one to go with the 6inch adjustable that I must also get.

Sometimes with fast-growing kids, it's tough. It seems like every time my 6-yo gets on her bike, the seat or bars need to be adjusted. Usually we're still on our own street, so it's easy to swing back in to the garage for a tweak.
Since kid's bikes often have hex-head bolts on these, look for a set of 'ratcheting box-end wrenches' These will make those jobs much quicker. You may find that seatpost and handlebar stems on the kid's bikes are only one or two sizes, so you just need to bring those along, not the rest of the set.

If any of your bikes need to have on-the-road repairs or constant adjustments to finish a 5-10 mile ride, you need to do a more thorough job of going over them, or have a qualified tech do it, as this is a sign of a bike in bad repair.

I do carry a spare tube, and patch kit, on my bikes, since they do see longer rides, but the patch and pump work on any of the bikes. Most of the bolts on a modern (non-Walmart) bike are going to be allen-head sockets, so one of the 'swiss-army-knife' style multi-tools is sufficient.

I do have a bolt-on rear wheel on my vintage (1976) ten-speed, so I carry a small adjustable wrench to assist with removing the wheel for flat tire repair, but that bike has been re-built several times, and over a pair of 100-mile rides, it didn't need anything more than a trim adjustment on the front dr.

I used to do a lot of back-woods MTB trails, and you had to carry enough tools to get your bike rideable after a crash, or be prepared to carry your bike back to town.

As others have said, I'd probably carry a quality adjustable wrench (Crescent brand or similar) and a set of Allen-head wrenches. You can find these either bolted together (in a multi-tool) or sometimes connected to a key ring where they all dangle free and you can disconnect the one you need to use.

I can sympathize with the need. If you need to remove a wheel when out on the trail (to change a flat), you need to be able to turn that nut if it's not a quick release. The adjustable wrench should be able to do that. And kids seem to always want their seats or handlebars adjusted -- at least mine do. It's not EVERY trip, but it's not common for one of them to want their saddle slightly higher or lower, or the shifter twisted just slightly on the handlebar. Rather than make it a negative thing ("silly kid, set it before you leave the house!"), I keep it positive by showing them that bikes are easy to adjust and service and easy to customize to meet their need or desire, even if that changes mid-trip. The more they get accustomed to working on bikes, the more they're likely to ride.