RiddleOfSteel

This thread will be a grab bag of sorts, more of a list of discoveries over the last few months. Pictures and ROS component outfitting will, of course, be presented!

Ok, to the bigger of the two headline items: Trek 620s and their 531CS tubing.

Many of us, certainly myself, have read other members wondering about what is Trek's 531CS tubing mix and how does it compare to other years. I think this inquiry also extends to 531C and similar on top road and touring models as well. I finally have frameset weights, at least in their largest size, to compare.

A month or so ago, I was mentally spitballing the idea of selling my '85 620 and wondering how I'd set it up to make its price appealing, its components attractive and effective, and my shirt not totally lost. Frame purchase plus canti stud work plus powder coat plus decals has always provided an adequate defense against selling it as I'd have to come into an entire nicely functioning bicycle for free to have a chance at breaking even in a sale that the market would support. Breaking even has always been a goal of my bicycle endeavors, and like many of us, I've won some and lost some over the years.

For this 620, I began changing a few things--stem, bars, then seatpost; and then a few more--wheels and tires; trying to lighten the component investment price while still having an attractive product, and, well, I failed. Turns out that polished TB14s and brown wall Donnelly XPlor 40mm gravel tires look really freaking good together. And the ride is equally as good. Especially against the satin black of the frame. And with all the other polished components. I documented these minute changes but won't bore you with them right now. Maybe if this thread gets some momentum.

The end result is a bike that I am keeping, still, that rides like a Cadillac, has better off road capability than before, and expands (vis disproving previously held conclusions) wheel and tire possibilities. The '85 now looks like this:



A couple weeks ago, I picked up a 1984 620 in my size (25.5") for a good price. Extremely low mile, with much dust and decay of consumables to show for it. These '84s, as we know, have 45.5cm chain stays compared to the longer, 720-matching 47cm chain stays of the '85s. Frame angles '84 vs '85 differ slightly, but both are equally tall (65cm CTT essentially) and nearly as long as each other. My '84 looked like this:

RiddleOfSteel

I was able to air up the old tubes and tires, get some scraps of used EVA bar tape wrapped around the brake levers (after peeling off the decayed hoods), adjust the rear brake, put some SPD-SL pedals on it, and get out on the bike. It showed plenty of those Reynolds-tubed Trek virtues, even with narrow tires, and confirmed once again that these long wheelbase bikes really suit me. I swapped bars and did some more test riding before putting the bike on the stand and disassembling it.

But we're here for frame weights! I'll stop burying the lede..

1985 Trek 620 frame, fork, headset weight: 3,533g / 7.77 lbs

1984 Trek 620 frame, fork, headset weight: 3,250g / 7.15 lbs

Both framesets use/used Stronglight headsets of essentially identical design (angled needle bearing with removable steel races) and both were 25.5" that measured 65cm CTT or within a couple mm. Chain stay length differs by just 15mm and both are designated touring bikes with canti brakes, rack and fender mounts, including on the fork blades.

Pretty mind-blowing difference in weights, eh??? Nearly 300g or 0.62 lbs for nearly the same length frame!

I'll show some more detailed photos of tire clearances, but the '85 620 continues to show its immense capability and flexibility. It can hold a 40mm tire with room for fenders vs the '84 tops out at 35mm with no additional room for fenders in front. The '85 is a freak, in all the best ways.

We can likely conclude that "531CS" from one year is not "531CS" of another, certainly as it applies to 1984 and 1985 Trek 620s. Maybe on a shorter wheelbase sport (600, 610) or racing frame (660, 670) from these years, the difference is smaller, but I don't know. The '84 620's lugwork and aesthetic are the last of its kind before the techy look of the '85. Heck, they look very nicely thinned on the '84, which I will never say no to! A 1983 620 is spec'd with "531C", so I'd imagine there's more tubing DNA relation between 1983 and 1984 620s than to the latter years. Trek should have probably called the '84 620 a 620 SL given just how close it is in weight to 700-level bikes of similar size. It's 90g heavier than my '82 720 and just 70g heavier than the nearly as long 1980 510s I've had (granted they are similar spec fully-DB Ishiwata 022). To be nearly 300g lighter than the following year's model with the same tubing designation is considerable.

I will say though, there is this weight difference, but the Trek and/or Reynolds 531 DNA, as it bears out in ride quality, is very consistent. The '85 handles lightweight wheels and tires equally well as heavier ones (TB14s at 505g each, Donnelly tires at over 500g each), owing, I think, much of that capability to the frame's beef. The '84 620 strikes me as likely being a punchier '82 720, which I think will be fun to experience. It will get the chance with appropriate wheels and tires (that I have available), so stay tuned. The French stuff will go, but I'll keep the timeless Shimano 6206 triple crankset.

RiddleOfSteel

To fulfill the full thread title here, late last year, I picked up a 1984 Nishiki Medalist frameset for a song. 63cm CTT. 74°/74° angles, 57cm top tube, interestingly slightly longer 415mm chain stays, Tange Champion 1 tubing. Paint and decals are beat up, with surface rust plus a tiny ding in the upper seat stay on the non-drive side.

The headset was a boat anchor at a whopping 150g, but somehow the frame, fork, and headset combined weight (my standard method of weighing) came to just 3,006g. So, with, say a standard Stronglight headset or anything aluminum from Tange or Shimano, that's easily under 3,000g which puts it in pretty special territory. But wait, it has fender eyelets with short reach calipers?

Frame as bought. Looking sad, but also special with a number of nice details:



The only Champion #1 tubed bike I've owned thus far:



"Hey, what does this thing look like mildly assembled into the form of a bicycles?"



"Why do we have these fancy Shimano 11-speed wheels and 32mm GP5000 tires on this bike?" Well, because when I put older brake calipers on it (because I was just going to build it super cheap to sell), I had to set the pads at their lowest in the slots. This meant there was a good chance that ~30mm tires would clear vertically, and maybe that would be enough to work with the 11-speed era of brake caliper from Shimano, which of course is grouped with other nice parts....

Oh look, miracles!



...with healthy chain stay clearance???



Aaaaand the deal is sealed. It's time to build this with absurd components.

Sedgemop 

Man, that '85 620 is looking good.

jdawginsc 

Could the weight difference not be the tubes, but the trek integrated head tube and joints compared to the thinner lugged ‘84.

And Tange 1 is under-rated stuff. Nishiki built some great frames (or contracted well).

Ex Pres 

The socketed lugs on the '85 weigh more than the '84's "plain" attachments.
The longer chainstays on the '85.
The cantilever posts on the '85. EDIT - I was thinking '83 w/o posts. If I just looked closer before I typed I could see the '84 has 'em, too.
Trek had some headtube assembly differences on some frames about this time, too, didn't they? And I don't know if it included the 6xx frames or not.

.

RiddleOfSteel

[Post #3 Continued:] And I did, after test riding it in this "just get it running enough" form:

It was little more than a glorified single speed. Cranks were shorter 172.5s instead of 175s, I had the bars cranked upward to mimic more closely my typical saddle to brake hood drop while also giving enough reach to be accurate. This was not an ideal setup, but in- and out-of-saddle dynamics were encouraging enough to progress.



And progress to this: Another Innicycle headset swap, this time with the fancy road bits that, if proved good, would pave the way to run my 11-speed Dura-Ace group. The alloy drop bars were quite narrow, and these carbon ones (which have lived on many bikes of mine) are my normal 42cm width.



It's a handsome looking bike, even with this mish-mash of parts.



So now we have a full-crazy bike here. Dura-Ace Di2 from another bike, a 3.75" saddle to brake hood drop (nearly double my norm) that is somehow quite comfortable, a 26.6mm seatpost and an old Avocet Touring I saddle. Makes for about a 20 lb bike all said and done, which is nuts. The 32mm GP5000's are about 30mm IIRC and do very well. The curve of the fork blade is gorgeous, and I like the chromed elements, even if they're not in the greatest shape. The bike rides and handles very well. Out-of-saddle feels pretty darn good and ride comfort is definitely good.

I'm in a housing location/bike riding environment transitionary phase right now, and we're entering fall, so any further developments on this will be slow. It will remain intact for the time being as I figure out what to do with it. It is, IMO, far more a frameset than the $15 I paid for it, so while I could still just build it super cheap and sell it, that seems a dismissive fate for a frame as well-featured as this. What stalls me a bit from powder coating and re-decal'ing it is that the financial practicality of that runs right up against the formidable trio of 531-tubed Trek tourers (and a 715), bikes which need no paint nor decal work and are dynamically preferable to a small tire race frame at this juncture. I'm certainly not doing it to have a faster bike. I crushed that possible reality the other week by replicating a 17-mile ride I'd done a month prior on my carbon Orbea with this very Di2--an 18.0 lb build--with my '82 720. 17.0 mph average or just under for the Orbea and me in cycling clothes, vs 17.0 mph on my 24+ lb 720 in street clothes (t-shirt and shorts)... This Nishiki certainly wouldn't be any slower, but...those darn Treks crowding out the podium of goodness...

Anyway, let me know your thoughts or if you have any questions. I'll be posting more photos and details, though likely tomorrow or later this week.

mhespenheide 

This was my first thought as well, before I scrolled down to see it mentioned here. Who knows how thick those one-piece head tube / "lug" assemblies were, and the seat lug is costing you weight as well. Easier to build, though.

I'd love to find a frame with Tange #1 in my size. But it seems like every one I see in the tall sizes has a short top tube, like the 57cm for this Nishiki (If it fits you, that's great, but I like 62-63cm frames with a 58.5-59cm top tube.)

mhespenheide 

At a certain point we have to admit to ourselves that we just like messing around with bikes even if it's unlikely that they're going to be keepers. I have multiple terrific bikes that are not likely to be leaving the collection and a limit of n = 10. So if I want to check out new bikes or frames or new ideas (650b? Are canti's as bad as I remember or are they worth trying again?), a new-to-me bike or frame isn't likely to stay in the collection once I've experimented with it and learned something from it and it needs to get passed along. Nothing wrong with that being part of your process of enjoying the sport/hobby/passion. {shrug} If I had infinite resources and space, I'd have a lot more bikes. But I don't so there has to be a certain amount of turnover.

RiddleOfSteel

The head tube and head lugs are all one piece on the '85 620. They used this design on the 720 and 760, 770, and 170 for 1984 and then essentially the whole lineup in 1985+. My friend @ctak here had a 1985 720 in the 24" size and I did some CAD work, using their provided geometry and calculated the frameset weight were it to be in my 25.5" size. The weight was around other 720's weights.

I noted the longer chainstays in previous posts, but it seems to me the two largest contributors to a 300g weight difference would be the thicker head tube walls (the lug portions are not appreciably different than traditional ones) and beefier tubing. There are cantis for both years, so that's the same and I don't believe there's too much gained with the lugs. The '85 has longer fork blades and it takes a 35mm tire to ease it over troubled pavement. It's just built for battle.

RiddleOfSteel

I don't mind a short top tube too much since it allows me more flexibility to play with stem and bar combos to dial in reach and aesthetics/proportions. A 57cm top tube on this frame with it's 74° seat tube angle, "normalizes" to a 58cm top tube with a standard 73° seat tube angle. It's still a touch short perhaps, but within range. 65cm frames with 59cm top tubes are what I prefer and thankfully, that's what many of these Treks provide.

The one piece head tube/lug assembly's "head tube" walls are thick enough that they have a recess for headset cups deep enough that it makes getting some cups out really tricky. It's chunky.

RiddleOfSteel

Yeah, my default approach is frame character curiosity and building it in ways to bring about its character as best as possible. Or that and making it look cool and work for me. I have a space limit as well, which has always been a factor. I'd love to collect, restore, and ride all the super tall 700-level Treks, but I don't have that space, so I let some (and other brands) go. The big, long wheelbase tourers are the keepers for me. That puts n at 3 right now, with all the other bikes up for sale but not really selling just yet..

Piff 

My only desire is to read more threads of yours. Great builds, great write-ups

bulgie 

Great thread, nothing much to add so far except I don't trust an Avocet (aka Ofmega) seatpost. That is what's on the Nishiki, correct? Mine suffered a broken bolt that almost dumped me on the back tire, then later (after replacing the bolts with Grade 8), another broke. Or was that on a different seatpot? I don't remember; this was 30-40 years ago. But I'd guess it was the front bolt each time, since it gets added tension when you sit on the back of the saddle. The static tension from just tightening the saddle angle, then the added dynamic forces from you hitting potholes etc.

Later, there was an internet, and I told this story, and several people reported the same thing happened to them. So it's not just me.

I think a 5 mm bolt is just too small for the forces it sees. Campy 2-bolt style is 7 mm, which is a huge difference in strength. Has anyone here ever heard of a single failure in a Campy 2-bolt seatpost, ever? I haven't. I have heard of maybe 5 broken Avocets, counting my two.

That's a small number, and other people have reported many happy decades riding them without breaking a bolt, so maybe my experience is a fluke. But you're a big dude, and the stakes are high. It's a cute seatpost and I wanted to like it, but I won't risk it, meself.

Mark B

RiddleOfSteel

Thank you! I do try to be worth the read here. I will share the '84 620's final build when I get there.

I was quoted and replied to by @Hobbiano though I think he deleted his post. I re-read it via email and he said that the 700-level bikes that he has observed with this one-piece head tube/head lug setup are decidedly different (aka the head tube portion is thinner/normal looking) than the lesser level Treks. This makes sense to me as 1) Trek had it in their power to do this, and 2) ya gotta make the 700-level bikes worth it in weight savings and performance, so this would be a par-for-the-course move. A very welcome insight, so thank you!

RiddleOfSteel

Thank you and great to know! I suppose the two elements decreasing the risk of this happening to my 200 lbs self is that I am leaned forward a bit due to the saddle-to-brake-hood drop as well as the plushness of the Avocet saddle. Dramatic reduction in acute force vector numbers. That and the C24 carbon/aluminum wheels, latex tubes, and 32mm tires. @Mr. 66 thought that a 26.6mm seatpost on a Champion #1 frame seemed a bit small given the tubing's pedigree. 26.8mm to 27.2mm would be expected, but there are no signs of a too-small seat post being used. Doesn't help that Nishiki Medalists don't show up in the one or two catalogs year-relevant catalogs online. At least aftermarket solutions exist should I pursue them.

bulgie 

OK, but I was a racer with a flat-back aero position back then, and quite a bit skinnier than I am now, when I managed to break those bolts. But you're right that the idea of using such fat tires for road hadn't gotten popular back then. Bigger softer tires definitely take the sting out of road bumps for the equipment as much as for our puny human corpses.

Big OEMs didn't get "tube sets" from Tange, they got boxes of 50 or 100 top tubes, other boxes with DTs, STs, stays etc. Each tube could be ordered separately and it wouldn't surprise me at all if they substituted a slightly heavier tube for such a large frame. But even the catalog-correct ST for #1 was .9/.6/.9 double-butted — quite different from Reyn. and Col. with their single butted ST. That DB ST wasn't used on all Japanese bikes, but it was quite common. That ST naturally takes a 26.6 mm post. Only downside is it makes the frame heavier — by what? An ounce? Not noticeable, and the improvement in reliability of the seat cluster is noticeable. I think it's a good idea, the only downside (besides weight) being you can't make a full size run of frames with only one length of double-butted tube, unless you make the butt long and the unbutted section short. It's that or make them with different unbutted section lengths, and make the manu order the right number of each length. Not sure if they did that — we always ordered our Tange STs in the single-butt variant (27.2 post).

Interesting to me, one mid-'80s(?) catalog shows Champion #1, #2 and #3 all with the same ST, 9/6/9 DB. The other tubes varied in gauge of course but not the ST. I don't know if that was true for the whole life-span of the Champion tubes line, or if they changed it up sometimes. Again a particular OEM could order lots of other choices. There was no enforcement on truthfulness of the tubing decals, that I ever heard about anyway.

Mark B

RiddleOfSteel

Thank you for providing context to the seat post bolt failure scenario. I'll continue to be mindful of mine, though if I decide to do anything with the bike, and especially if it keeps its go-fast components, I'll be replacing the seat post.

Thank you also for giving insight into how tube sets were ordered/delivered and used. I would have never known that, and it's nice to know that, at least for Tange, it wasn't an issue of a smaller diameter denoting a lesser tube set (at least with Champion 1 through 3).

bulgie 

Yeah and the next heavier/cheaper Champion, #4, takes a larger seatpost! It uses 1.0/0.7 single butted tubes for all 3 of the main triangle tubes. Single butting is cheaper/easier because of the difficulty of getting the mandrel out when double-butting. The mandrel is bigger in the middle and smaller at both ends, tricky to pull it back out after the tube is whammed down onto it to form the butts.

So seatpost diameter as a proxy for frame lightness comes with caveats.

Mark B

Hobbiano 

Yes. I deleted my post. I just couldn't get it to make much sense no matter how many times I edited it. So I'll try again:
As an aside, near the beginning of this thread there was some conversation about the different head tube configurations Trek used. I wanted to share what I think they did on the '84 & '85 models in the various series, based on my own experience with bikes I own, information from the catalogs, & what I've read from various threads here in C&V. This is just what I think is correct, but I'm by no means an expert, and welcome any corrections.
Based on my frames, Trek used three different head tube configurations in '84 and '85: The one-piece bulge-formed headlug used in '84, the Trek one-piece investment cast headlug - noted in the "85 catalog, and a three piece configuration consisting of two investment cast lugs brazed on to a normal head tube.
Here is what they used on my red 400 & blue 610. Note that you can see the ends of the top & down tubes. The entire headlug is formed from sheet steel, punched, rolled, & welded:




Here is a one-piece Trek investment cast head lug on an '85 560. Note the "TREK" cast into the sides on the lug portions, and how nicely finished looks on the inside, and the shouldered socket that the tube is inserted into. This headlug was specified for the 400 through 600 series in the '85 catalog:


This is how my '84 770 (green) & '85 760 (it's actually Treks Beaujolais) look. I think this uses Tange investment cast lugs brazed to a normal headtube. I think this is the most traditional construction and probably the most time consuming. Whether the tubes or mitered or they fit into shouldered sockets in the lugs i don't know. Note the small vent holes which I think indicates three piece, two lugs, a headtube, construction:




I think the 700 series, in '84 & '85, used three piece head tube/ lug construction, and everything else used one of the two one-piece headlugs.
I'm not trying to sidetrack this thread, just trying to fill in some information.

Kontact

Is there a question as to what 531CS is? I thought it was a very off-the-shelf combination of 531 and 501?

mhespenheide 

I think the question is whether there were different wall thicknesses across the years even if the metallurgy / composition of the tubes was consistently 531 in the main triangle and 501 in the stays and fork blades.

mhespenheide 

I don't think those lugs are physically long enough to have perpendicular cuts to the tubes and then plug into shouldered sockets. If you think about where the bottom of the tube has to end, the top of the tube wouldn't be in the lug if it were cut square. I think these lugs have to have mitered tubes.

Kontact

531 is an alloy, and was available in many configurations. But I thought 501 is the name of a tubeset made of standard chromoly, and therefore unlikely to be variable.

But as a product 531CS is a cost saving compromise to allow builders to put out a "531" frame a discount. So I guess I'd be surprised if builders or Reynolds would bother secretly "improving" it with custom configurations that they aren't telling anyone about. It's like suggesting that some Toyota Corollas were slightly superior in some mysterious way. So color me skeptical that there is any important variation.

mhespenheide 

531 is a manganese / molybdenum alloy of steel and was available in different wall thicknesses. 501 is Reynolds' name for the (now more standard) chromium / molybdenum alloy of steel. I believe it was offered in multiple wall thicknesses as well. A major builder like Trek could pick and choose between different wall thicknesses as they liked, just like the discussion above for Tange tubing. I don't think that's "secret". It's well-known that Trek specc'ed a thicker 1.0/0.7/1.0 down tube in its 531CS bikes, compared to the standard 0.9/0.6/0.9 wall thicknesses or even the 0.8/0.5/0.8 wall thicknesses used by others. It was just part of the choices that framebuilders or companies made to try to differentiate themselves from a sea of otherwise functionally-identical lugged steel frames.

Bianchi did something similar, mixing in Columbus SP downtubes and chainstays into a frame that was otherwise SL.