I have a 1989 Trek 520 that I currently use for commuting. There are a few things that I would like to be able to do on my commuter. I bike a bit more than I drive so I am okay putting some money into it. No matter what, I would like to own just one bike (so the 610 is likely going away no matter what). Here is my inventory and resources for a commuter/tourer:

Wants:
A solid commuting bike and touring rig
Dynamo Lighting
Front and rear racks

Assets:
$400 - 1989 Trek 520 (22.5", everything is working, minor paint knicks on frame/fork, all original but saddle)
$300 - 1984 Trek 610 (531, Shimano 600 crank, 105 derailleur, etc)
$1,200 - willing to put into a new bike or pour into the 520 if I can get what I need

Negatives with the 520:
Has 27 x 1.25 wheels
No dynamo lights
Older components (like the BioPace crank)
Not set up for optional trail/gravel travel

Positives with the 520:
If I keep it, I can probably keep the 610 as well as a back-up bike
It looks great
It is fully functional and sized right

So, what would you do? Put a bunch of money into wheels/dynamo lighting and some upgrades on the 520 or sell the two Treks and get something like a Surly Ogre/ECR/LHT/CC, Salsa/Soma, custom build from frame? If you have suggestions on the lighting situation on a 27x1.25, I would love to hear them as well.

Keep the Treks- buy a used Ultegra 10 or 11 speed group off the 'Bay and upgrade the 520. Probably run you about 300 for the groupset. Buy a decent set of wheels for under $200. Or look for a donor bike on local CL and strip the wheels and groupset off of that, sell the frame and whatever you don't use. You can also sell the stuff off your 520 for a good amount of money to subsidize the upgrades.

This is easy; keep the two vintage bikes and get what you need for commuting. You can set up the 520 to work with 700c wheels. Try out some 700c wheels and see if the cantilevers adjust down. If they do, you're good to go. If not, do a bit of research and find some cantilevers that will work. These are both great bikes; you will not find a better new bike.

By the way, I own and ride a 1984 610; it's a great road bike for all purpose riding. I also own (and I'm in the process of fixing up) my 1983 Trek 720 (the precursor to your 520). I use it as a touring bike but it makes a great commuter as well. And I run 700c tires on it.

If I were looking for a gravel bike, why not a vintage mtb? Those make great all purpose bikes. Or simply use your 520; a touring bike works well as a gravel bike.

If you like the 520 I don't see any reason not to upgrade it with new wheels to get specifically what you want. Unless there's a problem with the components, keep them. They were quality when made. You can buy a 700c wheel with a dynamo, a 700c rear wheel (any 11 or 8-9-10 speed wheel can take a 7 speed cassette with a spacer), and since that will make your wheels a little smaller it will give you about 4mm more vertical room to install fatter tires.

I don't think you can expect to get bikes this good today, plus the accessories you want, for $1200. A 520 today costs $1260 MSRP. A name-brand gravel grinder with any pretentions to being nicer and more modern than that will run you up to nearly $2000 once you add the lights.

I would use the bikes you have. I had an 89 520 and hated it, felt like a slug. I have an 85 720 and love it. Converted to 700c wheels and albatross bars. Whichever bike you like the most upgrade to what you want and keep or sell the other. I have many bikes set up for different purposes, but do have overlap. My 720 is set up as light as possible, just a saddlebag. The Schwinn passage is set up similarly with Soma Oxford bars but has racks front and rear and fenders. Both ride similar, if I need to haul more or rain in future, ride the Schwinn, if clear and do not need to carry anything, the Trek. I have a dyno-hub I can swap to either pretty quickly. The trick is to define exactly what you need and work to that goal. In the past it seems I ended up having all of my bikes outfitted the same and would end up selling one or more and buying others just to do the same thing. I am getting more disciplined as I age and am lucky I really enjoy all of the bikes I have, even if I do not ride some very much.
Enjoy the ride,
Tom Palmer
Twin Lake, MI

No one has yet mentioned it...you can change the chainrings on your 520 to whatever the BCD permits. Nothing wring with 27" wheels, either, except a more limited tire selection. What really needs to change, the front hub?

Your 610 is a dangerous bike...I have heard of all kinds of frame failures. I'll take it off your hands and properly dispose of it for you

Why do you prefer the 520 over the 610? Just wondering, I don't have experience with either, myself. Do they both fit?
You can change out the chainrings. Most likely 110 BCD, which can be found for pretty cheap. Full 10 speed groupsets can be had for fairly cheap these days, as everyone is creaming over 11 sp. If you are going down to a 700C wheel, you have more tire options and can surely squeeze a 35-38 wide tire on, if not larger.

On Chain Reaction, you can currently get an 11 sp 105 full groupset for $400, then all you really need are your wheels. You should come in well under your budget.

Another possibility is that the 610 may well be a good bike for a 650 conversion; that will give you fat tires and you can build it with a dyno hub.

It's usually a pretty easy conversion from 27.5 to 700c wheels, but the fact that your 520 has cantilever brakes might be an issue. If you do stick with 27.5 you'd probably either have to build a wheel with a dyno hub yourself or find someone to do it for you. It's not impossible.

Otherwise I don't see any particular reason not to keep your 520. They are highly regarding touring bikes. You might be sorry you sold it. With some upgrades it would be as enjoyable to ride if not more so than the other bikes you're thinking of.

On the other hand, they do fetch some pretty good money. If you sold it, it wouldn't be that much more expensive to get a new bike with the components you like compared to upgrading everything on the 520.

If it were me, unless there was something in particular about the geometry I didn't like, I'd probably keep it.

[MENTION=90453]tjspiel[/MENTION] is right...a new Trek 520 has an MSRP of $1260, a 520 with discs is $1360, a 720 disc is just under $1900 and a 920 disc (adventure touring model) is right under $2k. You could sell both Treks and you could easily go as high as the 920 disc (of course, that is without dyno hub - but if you want a bike that can tackle anything, wow.)

A few questions:

1. I have thought about going the donor bike route. What specifically would you look for? I am always worried I will get something and none of the components will work or I wont be able to convert to 700c.

2. can I fit the 10 speed group on the 520?

I like the gearing (really hilly here in ATL north suburbs) and the bike just fits well.

1. As long as you don't get something with French or Italian threaded parts, you should be fine for most everything
2. You will need to cold set the rear triangle to 130 mm spacing. Sheldon has instructions
3. That's cool. If it works for you over the 610, that's what matters most (Though I'll still dispose of that 610 for you ...I'm only 3-3.5 hours away) Your limiting factors on your 520, as already mentioned, will likely be your cantilever brakes. You might be okay, but you'll have to measure the reach and how much adjustment you have, both vertical and horizontal. It's easier to make the switch down to 700C with single or double pivot brakes, as they mount above the tire and not on a post next to it.

Other than bike fit, you mention gearing...which would be moot if you are changing that. If you can get ahold of a 700c wheel, try mounting it to see if you can adjust your brake pads enough to work. I would mount both front and back, just to be sure.

Here are the two bikes. Not sure if the images help at all.

Cool! The 610 will definitely be easier to convert down to 700c, if those current brakes don't have the reach just throw some Tektro R559s on it. However, there is nothing wrong with 27" wheels. If you wanna get really fancy, keep the rims, and get new hubs and spokes and have someone build them up for you, if you can't do it yourself. I've thought about doing it to a bike I converted down, I just haven't wanted to spend the money. That way, you can put a modern cassette and drivetrain on with no problems or worries about brake reach.

So you think I should actually put the dynamo lights with a 700c rebuild on this frame instead of the 520 for commuting?

If you are deadset on going down to 700c, that will be the best choice. If you can though, dry fit a set onto your 520 and check if you have enough adjustment on your cantis first. You might luck out. If not, you can always try and find different cantis that have enough adjustment, but it will require some luck and trial and error. If anyone else here has ever made the conversion or knows of a good brakeset, please chime in here. Paul Touring brakes probably would, though it's an expensive trial and error there.

If you really like your 520 that much more, I suggest having new hubs laced to the existing rims, or even getting some new 27" rims as well, just because. The expensive route is to take it to a frame builder and get your cantilever posts rebrazed to the correct height for 700c wheels, then have your frame and fork repainted or powdercoated.

I think both bikes are terrific bikes.

You could easily swap the crank from the 520 onto the 610, but if you like the fit of the 520 better I think that trumps everything else. Are they different sizes?

I'd probably stick with the 520 for the purposes you describe. Do you have any 700c wheels you can use to experiment with the brakes? That would be the first thing I'd figure out. I think there's a very good chance it will work, but it will depend on the brakes you end up with. Since you're looking at having a new front wheel (at least) built, you could stick with 27" if you had to, but it's always nice to standardize.

You shouldn't have a problem putting modern (10/11 speed) parts on the bike except that you'll need to update the rear spacing as bmthom.gis suggested (not all that hard but it might be worth having a bike shop do it to get the alignment just right). An alternative to the donor bike route is to order from one of the UK websites that sells Shimano components much cheaper than you can find them in the U.S. You can get a full 11-speed Ultegra groupset (shifters, derailleurs, crank, bottom bracket, chain, cassette, plus caliper brakes that you can re-sell) for about $550.

there is no need to change a 27 1/4 wheeled bicycle to 700c wheels unless there is a new style tire you would want to use. i have a raleigh sprite that i converted to a 21 speed. still used for distant work.

that old bicycle has bell kevlar tires. they are good for road debris

Likely will not have to respace the 520. I've done 2 ('87 & '91) 400 trek 10 speed conversions and neither required cold setting the frame. 130mm hubs fit right in. You'll often find late '80's early '90's are spaced at 128 to allow different setups due to the change over in that time period.

unfortunately the only reason i converted the raleigh sprite was because it almost fell off a vehicle the rear triangle was damaged and thought well if im going to fix that much might as well up grade it. err