I decided to build a touring from scratch. I have two frame options: a 2007 Trek 520 and a 1990 Trek 750 (lugs). Does anybody have ideas or knowledge about strength and durability comparisons? Both frames are in same good conditions. Thank you.

The 520 is a proven performer in the touring niche and would be my choice.

Brad

One consideration is the length of the chainstays - the longer the better for heel clearance. I don't know the geometry specs but I would guess the 750 is going to have a little more upright position so your riding preferrence and types of places you plan to tour may be a factor. The 750 may also get you more clearance for wider tires and fenders. Does the 750 have mid front fork rack mounts?

Yes, the 750 have mid front fork rack mounts.

I own a 950, have panniers (Tubus rack) and no problem. Same chainstays than 750: 16.9". Nevertheless 520's are 17.7". Any comment on the strength/durability area? Thank you again for your insights.

Which frame do you think will fit you best? The 750 was billed as a hybrid, which will likely provide a more upright riding position with geometry designed for straight bars. 520 proven tourer, with drop bars.

Personally, I'd go for the 520 if it fit.

Thank you Brad.

I run an early 1990s tig-welded Trek 520 59cm x 59cm and it's flexy like a noodle when loaded or when ridden hard.

Both are adequate.

No need for the guessing and speculation. The Trek catalog clearly lays out that the Trek 7xx bikes from that year are the same geometry as the 520 from that year, just with the 7xx bikes having an inch shorter chain-stay. The 750/790 are also made with the same True Temper butted chromoly tubing as the 520. I have a 90 750 that's a good bike. I personally slightly prefer the shorter chain stay for the slightly better handling, but I'm sure it's a tiny difference. I still have clearance for panniers with a size 10 shoe. It does have a little front end shimmy at high speeds if I take my hands off of the bars while peddling, but that's my only complaint about it and my friend's brand new Salsa Fargo has the same problem even worse. Just don't ride at speed with no hands while peddling.

That said, I personally would probably see if the newer 520 is supposed to be any stiffer than the older bikes. If so, I'd go with the newer one. I think I'd be a little happier with a stiffer frame than what my 750 has. If they're the same stiffness, I'd probably just go with whichever one appealed to me visually(assuming they both fit well and cost ~the same). They're both suitable.

If you're going with rear panniers on a touring bike, chain stay length matters. There are other things that can take care of the problem (narrower bags, longer rails on the rack) but ideally you have a bike that works with most every combo you might throw at it. Everything else being equal, I'd get the 520 for that reason alone.

Not knowing the history of either frame, I'd go with the newer one. It has had less time to rust or fatigue. While there are no guarantees either way, I'd think a 7 year old bike would be less likely to break than a 24 year old bike.

As I wrote previously both frames are in same good conditions, good paint, no rust, but I think you have a point: you can't see fatigue. I'll go with 520: +20mm chainstays and younger. Thank all for your kind and fruitful advisement.

Either one. The 1990 lugged Trek Multitrack 750 has a cromoly double butted frame and has the SAME touring geometry as the Trek 520!

They just didn't call it a touring bike in Waterloo but for all extents and purposes its a rebadged Trek 520.

They made a touring bike! Its not as famous around here as the 520 but its a capable tourer. Not to be confused with LATER TIG welded Trek Multitracks which really are hybrid bikes.

You're right about the TIG welded 750s. Nothing special about them. But the early lugged 750s were clearly designed with touring in mind and the half inch difference in the chainstay length from the 520 is inconsequential. The fact they spec'ed them with front rack mounts indicates that Trek had at least two different touring bikes in its lineup in the early 1990s. That was to subsequently change.