denaffen

I currently have an 89 Trek 520 and I'm not sure about the fit. I measure it as a 52cm, which I think Trek called a 21" back then. At any rate, it feels a touch big to me. In particular, the standover height gives me the willies. It feels like a very, very tall 52 cm to me. Certainly moreso than my 52cm Bianchi.

I'm eyeing a 640 frameset, which -- as I understand -- was pretty much the same as other early to mid-80s 620, 630, etc. Treks. I'm told it's a small, 48cm frame (19" as listed by Trek back in the day).

So, two questions... first, while the 640 frame should certainly solve my standover issue, would I be likely to feel cramped on it. I'm concerned with the shorter wheelbase compared to the 520, coupled with the smaller size, I'd feel like I was just trying to ride all bunched up.

Second, in general, how should I expect the 640 to compare, riding-wise, to the 520?

thook

the 48cm is going to be very small compared to your bianchi. and, if the bianchi is comfortable to you, then you should probably stick close to that size. 4cm's makes a very big difference. you will feel cramped
the trek 520 might have a higher bottom bracket than your bianchi, too. that would explain the difference in standover. if compared to the '94 520 i had, the bottom bracket drop was 6.5cm. and, your bianchi is lower, i'm sure, by at least 5mm or maybe 10mm. as well, tire size makes a difference. does the 520 have bigger tires than your bianchi?

canopus 

Here is the info for your trek 520, what year is the 640? Standover height will be affected by wheel size and tires.
You can look this up at the Vintage Trek site. https://www.vintage-trek.com/


1989 Trek Chromoly frames.

RiddleOfSteel

@denaffen do you have a photo of said potential 640 (or link if for sale online)? I believe it was only one year, which would be 1983. I'd have to deduce the geometry from prior years, but it's possible. Which Bianchi are you comparing it to? Year and model would be most helpful in trying to obtain the geometry for that.

Trek geometry and resulting ride quality for their sport tourers and tourers should be solid, if not very nice, regardless of rank. The '89 520 does have a bottom bracket that is 7mm higher than previous years of Trek. I don't know why, but that, plus larger tires (as it is a touring bike and not a small/skinny tire race bike) contribute to a taller standover height.

I'm at the other end of the size spectrum and run all geometries I can find through CAD to get an idea of how a frame will fit me and what sort of stem, bar, and brake lever combo I'd need to make it work. At your height, I would welcome the ability to "grow" a frame, potentially, via use of a longer stem. So many times, frames are simply not short (in the top tube) enough for many low five-foot riders. Why so many manufacturers would spec an 80mm to 90mm stem on modern bikes that size just baffles me.

Anyways, let me run through some CAD real quick, but I'll need that Bianchi info to make a more thorough comparison, especially if that is a bike you like and measure other bikes, too (and if not, what bike would that be?).

mechanicmatt

I have a '91 Trek 750, essentially the same geometry. Same problem. It's tall on standover height (due to a high bottom bracket height) but the geometry is right for me.

denaffen

> tire size makes a difference. does the 520 have bigger tires than your bianchi?

Yes, that is one factor. The Bianchi is on 700x28 (or 25, I can't recall which), while the 89 520 was the last year for 27 x 1 1/4. I'm toying with a 700c conversion on the 520, but still debating on whether or not the frame itself is right for me.

> what year is the 640

640 was one-year-only (83), although I understand the same basic frame was used on 6x0 models before and after then.

> Which Bianchi are you comparing it to?

It's circa 89-ish Campione D'Italia

> The '89 520 does have a bottom bracket that is 7mm higher than previous years of Trek.

That's very interesting... it *feels* like a high BB to me, which would go a long way to explain why for a given size it feels so tall (and the standover height)

> I would welcome the ability to "grow" a frame, potentially, via use of a longer stem

That's another interesting data point... The Bianchi has a ~100mm stem and feels right (with Soma Highway 1 bars). The 520 has a very short (60mm?) stem fitted, but it still feels like a reach to me. That may be the vintage, longer reach bars, and it's not a problem, but it is another interesting data point.

I actually have a bit of a preference for longer top tubes, partially because i came up on BMX and MTB, but also because I'm short legged/long torso'd. In my ideal world, the 640 would be shorter height, but with the same general top tube length as the 520. That would probably be a slam dunk for me.

The Golden Boy 

I haven't done a lot of looking at the geometries after 87/88 (or really after 86)- so this chart is interesting in that the 400 and the 660 share geometries. Where the 660 was squarely a race bike and the 400 used to be squarely a "sport tourer;" the 420 seems to occupy that all-rounder ground in 1989.

thook

back to the beginning (sort of), use your 52cm bianchi as a basis when judging the proposed 640. leave standover and the 520 out of the picture for the moment. again, that 49cm is quite small. how long is the reach...ie. stem length, bar reach, saddle set back....on your bianchi (that i presume fits to your liking)? let's say you have a 10cm stem on the bianchi. you will need a quite a long stem for the 640. furthermore, there's a difference in saddle height and stem height. even though you have short legs, you will need to account for that 3-4cm difference in bar/stem to saddle height between the bianchi and the 640. nitto technomics are most people's solution, but still....
another point to consider.....with your current 520. a 27 x 1 1/4 wheel/tire is within the same diameter range of a 700x35c wheel/tire. a possible solution with your standover dilemma is to run a smaller wheel/tire combo on it. maybe 700x28 or 32c?

is this making sense to you?

otherwise, i'd say hold out for a 50/51cm frame. maybe trade out your 520 over in the frame doesn't fit/pass around thread. that 640 is just gonna be small, imo

RiddleOfSteel

I ran some geo calcs through good ol' Rhino 6 here. Interesting results! From what I researched, the 1983 600/620/630/640 frames in the 19" size seem to follow the precedent set by the 1981/1981.5 models 510/710 (only ones that Trek had that small). Running the geometries forward to 1985, when Trek reintroduced full size range geometries, they don't seem to match up with what I see in image searches for 1983 6x0 bikes, namely that the seat tube angle is quite steep. 76 degrees! The 1981/1981.5 models 510/710 had that angling, and as that is the only data point to go on (that is as near to 1983 as possible and matches most closely), I used that. From my ownership and geometry measuring and calculating experience with this era of Trek (pretty much my favorite), Trek trailed a lot of previous years' numbers or "logic" into later years, while at the same time, introducing new features and geometry "logic". This thinking is a bit in the weeds, so I'll get back to the matter at hand.

First, some 1983 bikes to show geometry.

1983 640 - 19" / 48cm


1983 630 - 19" / 48cm (notice the steep seat tube angle--head tube angle is a normal 73 degrees)


Now for the CAD work. Four panels of comparison!

1989 Trek 520 - 21" vs. ~1989 Bianchi Campione d'Italia - 52cm (used 1991 Bianchi Eros geometry as that was what I could find)
The Bianchi's stand over height is about 10mm shorter via basic geometry, but combined with the 520's larger diameter wheels and tires, add another 10-13mm and you basically end up with a stand over height difference of about 20-23mm or just shy of 1", which can make a huge difference.


1989 Trek 520 - 21" vs 1983 Trek 640 - 19" / 48cm (hypothetical, combined geometries from 1983 and 1981 years)
Being that both bikes can accommodate a 700x32mm tire, this will be a good comparison. We have a 72mm BB drop for the 640 vs a 65mm drop for the 520 (and the Bianchi Eros, too). Stand over height for the 640 is a full ~51mm or 2" less than the 520!


1983 Trek 640 - 19" / 48cm vs ~1989 Bianchi Campione d'Italia - 52cm
There is less of a stand over height difference here, about 35mm or just under 1.5".


All three bikes laid over each other.
Here we see the remarkably similar "average" head tube angle and--quite crucially--position. What I am saying here is that you could run a, say, 80mm Nitto Technomic in a "high position" on the 640, and a more "slammed" position on the 520, and end up with the bar clamp position in essentially the same exact place, thanks to all three head tubes being more or less "along the same line". All that to say that a 19" / 48cm 640 won't be or feel cramped, length-wise. I think we'd all appreciate photos of your 520 and Bianchi as that allows us to see saddle height and cockpit setup, giving us more context, but for now, apart from quill stem height/elevation, you're theoretically not going to have an issue with the 640. Good news.

denaffen

That is truly fantastic. Thank you. And it matches up very well with what my butt has been telling me.


Here is the 520



And the Campione



And, just for fun, my very small framed Nyala. What I’m trying to get to is something in between it and the Campione.

(and yes, I'm aware there are issues with all three bikes, I'll get to it)

denaffen

As I look at those pics, and especially the head tubes, it's striking to me that the 520 and Campione both measure out at 52, and the Bianchi is the smaller feeling of the two.

RiddleOfSteel

What I think is not always considered, and it really took me owning my 620 to do so, is that one must factor in a fork's axle to crown height. Due to the 520's touring design, which necessitates large rims (27"s in this case, though 700C normally), large tires, and room for fenders (vertically), the fork blades are quite long and thus "creep in on" the head tube's overall length/height. It's deceptive, but the math adds up. If that frame ran small racy tires and an appropriate fork, the head tube would be longer. The seat tube, top tube, and upper head lug are all in the same place. This has happened to me when evaluating a frameset that I thought was for 700C wheels, but was really for 650C. The head tube length was massive, good for a 65-66cm bike (hooray!), but the seat tube measured just 60cm or so (horizontal top tube and everything). Enter confusion. Then enter a 700C wheel and deflated 23mm tire that can't even slot fully into the fork's dropouts. Ahhhh, this is a 650C frame. It also explains the 39cm chain stays as well.

denaffen

I picked up the 640. As near as I can tell with it just sitting on some rims, unbuilt, I think it should fit nicely

denaffen

It just now occurred to me to try to compare them side be side.

tge

520 has notably longer stays, as expected. The 640 step over is much lower, as expected.

as I measure the top tube length is within 1cm. Very close.

Road Fan

I have had a few Treks in the 1980 to 1985 time frame, and usually find the 21" models pretty uniform across the line. My first one, a 21" 1984 610 initially struck me as tall at the top tube, with its 27" wheels, 7 cm BB drop, and medium-upright seat tube (73 degrees). A bud had a 1981 600 (red paint, I think I got it right ... ) always felt lighter and more compact, though it measured nearly the same. It had the same seat tube angle, BB drop, and other frame dimensions, but it 700c 22 mm lightweight clinchers, rather than 32 mm 27" tires. I did not expect that to make such a difference. I've since acclimated to the '84 610, once I found a saddle/seatpost with adequate setback. But mainly I found that a small change in standover when the TT is nearly in contact, can make a big difference.

I was very surprised at how hard it was to ride a 56 cm 620, which was a lot bigger to me than the next size downward. But seat tube angle can make a big difference as can the interplay of dimensions - I have a 55 cm 1952 Rudge club-style frame with a similar standover and reach feeling to the 1984. It has a 55 cm ST, 71 degree seat tube, 57 cm TT. But the standover is just a bit less than for the 610, and the reach works even with the long TT. I still want to make a comparison based on stack and reach, but this all highlights to me that comparisons between frames based on a single frame dimension can be very misleading, when you are trying to infer how it will ride.

The 520 of the early '80s used three tubes of 9/6/9 butting and standard diameter, which are the same profiles and dimensions as the highly-respected Columbus SL, from which a whole generation of winning and competitive racing bikes were made. In contrast, the "higher rated" 6xx (db Reynolds 531 main tubes) series frames in that time frame had a 10/7/10 downtube, which in that position made the ride and pedaling always stiff-feeling. At the moment I'm putting together (well, alignment first!) a 1982 720 with very similar tubing though 100% db Reynolds 531. But the long skinny rear end of the 720 should feel different, and that's what I want to understand.

Keep in mind as well that you may need to experiment with saddles seatpost setbacks and handlebar stems to get your reach correct. After you get the saddle positioned back far enough you may need to adjust the stem extension and handlebar reach for a comfortable shorter arm extension. I'm 5'6", and that's how I fit frames in this size range.