Brake bosses on a Reynolds 753 fork?
 

Is the fork too fragile to add bosses to it? Its a Raleigh Technium. the bosses would be for a Ultegra 8010 Caliper.

Given that the bosses would be located in the blades' strongest area, their top, I suspect the fork would be able to handle the stresses. However I have not worked with the 753 material so what do I know? Andy

The crown goes down quite far. If the bosses were on the crown, is that any better or worse?

It certainly would be better to have the bosses mostly on the crown.

I was going to mention exactly where the bosses might end up at, perhaps overlapping w/ the crown. But I am not sure of the actual locations having not yet built a frame w/ these brakes, so I'm not sure. Once again this is when a measurement is worth all of our opinions, WRT boss locations.

The other aspect of 753 that I am unsure about, w/ the current versions, is the heat treating and the brazing temps not playing nice. Back when 753 was first introduced Reynolds claimed using brass as a filler would anneal the tubes and thus weaken the joint area. IIRC this was addressed somewhat with later editions. Silver had been "required" as the filler by Reynolds. Silver is somewhat more dependent on joint fit up and prep then brass so who ever does the work needs to be proper in their methods. Andy

When 753 first came on the market, Reynolds said no braze-ons of any type were acceptable. But people being what they are, over time 753 frames with bottle mounts, lever bosses, cable guides, and (heaven forfend) even front derailleur mounts were made with no undue problems. But all those can be attached with low-temperature silver, while I'd be leery of anything but brass for brake bosses. At best, the higher temperature of brass brazing would reverse the heat treatment 753 tubes get and leave you with plain 531. At worst, who knows? If it were my bike, I'd get a different, non-753 fork for the brake bosses.

All the 753 blades I have measured were just as thick as 531. So even in the worst case where you lost the heat-treat, they'd be as strong as 531, which are if anything a bit too strong for my taste, for most riders and purposes.

I really wish they'd made a lighter blade, to make proper use of the stronger steel, if only to get a more supple, bump-eating "undamped suspension". And maybe they did, but again all I saw were the heavy ones. Even Columbus SL were a little lighter than 753 IIRC.

Plus you can put brake bosses on with silver, if you make a suitable fillet. Fillet Pro from Cycle Design is probably the best filler rod to use, though any old 40% silver is probably good enough if done properly. Yes 40% has a liquidus a little hotter than Reynolds recommended for 753, but still way cooler than brass, and with fillet brazing you're working above the solidus but below the liquidus — in theory anyway.

Mark B

The 531SL blades were thinner, I thought. At least the ones I have are.

They created such a myth around 753. As you say since it was stronger the idea is to make it thinner. I think they did do that for the rest of the frame if not the fork. But then they brought out something called "653" for a time which was apparently 753 but minus the heat treatment. In other words thinner 531. But that was obviously considered strong enough to actually use on a bike. Some people even made mountain bikes out of it.

I have a Reynolds catalog from 1978 — I think, hard to tell. It does have a mysterious code of "778" on the back though. It covers 531, 531SL and 753. This was back when 753 only came in metric. Three choices in gauges of the main triangle tubes, but all just called 753, no "R" or "T" after it, at that time.
It just says all the blades are 19/24 gauge (British wire gauge), where 19 gauge (1.0 mm) is the wall at the top, and 24 (0.56 mm) is the gauge at the bottom before tapering. After tapering they are just a little thicker at the bottom than at the top, essentially plain gauge.

It's a bit frustrating that they give all the thicknesses of all the tubes in the 531SL and 753 charts except for the blades, where only the outside dimensions are given. But the earlier page on just fork blades specs them as 19/24 with no other choices given. Well, they had "Continental Oval", which to Reynolds meant the older, skinner 19 x 16 mm oval, and those are quite a bit thicker, 18/21 gauge. The 19/24 gauge was for the "New Continental Oval" (NCO), the one similar to Columbus, about 28 x 20 mm, which was what all 531SL and 753 sets came with.

That 19 gauge number jibes with the later (early '90s?) catalog I have that gives the blades as 1.0/.5, for 753, 731OS, 708 and 653. (531SL didn't exist anymore when that catalog was made.) It also jibes with the "Reynolds Tubing Constructors Guide" (late '80s?) which lists the blades for 531c, 753, 708 and 653 all as 1.0/0.5 mm. Only 531 ST (touring) blades were different, at 1.2 mm.

Yes, I know that catalogs often don't reflect reality, so I will be glad to get any real world measurements. Can you dig your 531SL blades out and measure? I know that is "assigning homework" and may not be what you wanted to spend your time on, so feel free to say No. But if you do feel like it, that would be educational and much appreciated.

I have 531SL, 753 and 531 sets in stock and I can measure them again to refresh my memory. It's been at least 10 years since I did that exercise, maybe 20. Those tubesets are pretty well buried though — my storage is in the midst of a long remodel project so it may take me a while to get that done. But anyway that'll only tell us what those particular tubesets came with. We won't be able to definitively say that 753 (or 531SL) never came with other, lighter blades at other times, or by special order. Hard to prove a negative.

Mark B

Not quite. 653 had 531 forks (no heat-treat @ 120,000 psi), 753 rear stays (full heat treat @ 195.900 psi), and main triangle was 653 which is stronger than 531, I have heard that was via cold-working (@ 138,500 psi). They called this "Variable Strength Technology". It came in road and "All Terrain" versions.

https://cimg6.ibsrv.net/gimg/bikefor...cc5c7d782a.jpg

Sorry this is so small, I don't have a hi-res copy, can you see it?

I'll see if I can measure those fork blades. I disassembled the fork they were in a couple of years ago. I think the big difference between 531 and 531sl fork blades may have been that the 531sl were bigger diameter towards the dropout end.

It's true that the '78 catalog lists 753 blades as 12 mm at the bottom, versus 13.5 mm for 531SL.

This seems to say that they are not just the same blade, with or without heat-treat.
Why would they taper the 753 blade more? Not a clue.

-Mark B

To make them more flexible. Matches the flexible of the rest of the frame.

Sure, but some of the 753 tubes weren't any thinner than 531SL. I guess your theory makes sense for the lighter 753 variants. I still wish they'd just made a lighter blade though, like Columbus and Tange did, among others.

I don't think that theory fits the era. Not many people were looking for more flexible anything on a bike frame at that time. Not sure when that idea came into vogue, but it wasn't in the late '70s or early '80s.

Mark will probably find an advertisement that contradicts what I just wrote :)

This chart from Equus Bicycle suggests 753 (road and track) and 531 "Professional" and "Competition" shared the same blade taper. This is also what the chart in the Paterek manual shows:

SL became pro, right?

I'm sure that I cut the excess off of the small end, but it's over 15.5 mm at the dropout on this fork. Looking at the 531 forks I have, that wouldn't be possible on a 700c fork.

Ha ha, no, not in those years, but In the '40s and '50s (maybe earlier too), smaller diameter blades at the bottom were in vogue, specifically for rough-pavement comfort. I have 531 blades as small as 12.2 mm at the bottom, and I'm pretty sure they made them down around 11 mm in days of yore. French constructeurs of high-end touring and rando forks seemed to favor the "pencil-thin" forks, curved the blades with a small radius form, and kept the bend all down near the bottom, specifically (I believe) to absorb more road shock. They even get Reynolds to make them with a rapid taper so more of the lower part was at the small diameter. That type of rake is back in fashion, but you can't get the really small diameters at the bottom anymore.

So, I went out to the shed to measure some blades. I didn't weight them though, sorry.

Name/Type Wall (top) Tip Dia.
531 wide oval 0.98 13.2
531 wide oval 1.03 13.3
753 (older, metric) 0.97 13.2
753 ('90s, inches) 1.02 13.0
653 1.00 13.2
Col. SL 0.85 12.5
Prestige 0.92 12.3
Excel 0.67 12.9
531 narrow oval 1.22 13.8
531 narrow oval 1.23 13.0
531 narrow oval 1.18 12.2
Kaisei “Toei” 0.96 13.2
Kaisei “Toei” 1.05 13.2
Prestige narrow oval 0.87 12.7
531 Tandem (non-OS) 1.40 13.1
'Jack Taylor’ tandem 1.40 13.5
Col. Tandem (OS) 1.20 13.0
Col. Max (original) 0.61 14.0

Why so much variation among supposedly identical blades, like the Kaisei or 531 examples? Some may be due to the inherently imprecise way I measured. I used high-quality Mitutoyo calipers, but that's not as good as a micrometer, especially the special micrometers made for tube wall thickness. Also most of the tubes had some odd shapes at the cut ends, not just a burr but sort of a rounded-over section, last mm or so. Hard to tell if it was bent, or metal removed or what. I tried best I could to avoid measuring on those areas. I deburred them as best I could, took repeated measurements at different places, and averaged the results (roughly, in my head, this ain't rocket science). I threw out any anomalous measurements that were way off, probably due to some localized lump or burr. I used a little pressure ("feel") on the calipers, same as it took to make the empty caliper read zero.

As to the original question, are 753 blades the same wall thickness as 531, I'm sure the answer is Yes, within the precision of my measuring method and/or the normal range of thicknesses due to manufacturing tolerance, and/or changes over the years. For example '70s 753 blades probably weren't drawn over the same mandrels as '90s 753 blades. My two sets of Kaisei blades were purchased a few years apart too.

Oh I said earlier I had a set of 531SL, but that was wrong. I have a box that says 531 SL on the outside, but with other stuff inside. I guess I just kept the box out of some sentimental attachment... I did find a 653 set that I forgot I had though. No surprise those measure the same as 531, since Reynolds always said they are 531 blades.

Mark B

Isn't the thinnest 753 (.38/.6mm main tubes) the most flexible steel frame?

753 is the lightest with the exception of the Tange Silhouette.

Could you explain what you mean in more detail? Your short statement is a bit ambiguous, but it sounds wrong to me no matter how I parse it.

Did you mean the lightest fork blade (what this thread is about)? Your mention of Silhouette makes me think you mean forks — that's a brand name of a Tange fork, correct? I know of several blades that were available in the past that were lighter. Like Excel, much lighter. Prestige had two lighter gauges, the lighter (and rarer) of which was two tenths lighter than 753. Even Columbus SL was a little lighter than 753. Some of those would be hard to source today. Also I think there are a couple blades still made that are lighter, like 853 and 953, though I haven't used them. Someone here will know. But basically, 753 blades aren't very light.

If you mean main triangle or an entire tubeset, I still know one or two historical sets that were lighter. Again, hard to source today, but apples to apples: original superlight 753 is not thick on the ground either.

Your statement also doesn't talk about how 753 frame tubes came in different thicknesses, and how those choices changed over time. (Blades never varied much though — to the best of my knowledge only one weight was made.) Most 753 was light (up until Rivendell started using heavyish 753), but not all was superlight. Maybe you meant that as "the lightest 753 was the lightest..."? Sorry if that was obvious, I just like having all the assumptions and qualifiers spelled out, in a discussion like this.

I made a few frames with Prestige that was truly .6/.3, measured directly and confirmed by tube weight matching the calculated weight (based on nominal dimensions and the density of steel). 753 was closer to .7/.4, though Reynolds somewhat dishonestly calls it .3 in some of their materials. Did anyone ever get a 753 tube that truly was 0.3 in the unbutt? I'd love to hear about any confirmed sightings.

Ishiwata also had a tubeset with 0.3 mm bellies, from reliable reports, but I never held it in my hand IRL.

Mark B

Wow, I thought I have seen a lot of forks on the internet. But not compared to you. Could you give me any links to show lighter forks than 650 grams (for 57cm frame)?
I have had Columbus SL fork that was built for me 40 years ago and pick up the 753 fork last year. The 753 fork is 640 grams, and the Columbus SL is 697. I was finally able to get a Prestige fork off ebay It will arrive in July and I will update this when it arrives.
What was the true gauge of the Reynolds 753 at the butts? Somewhere between .65 to .69 obviously.
The Ishiwata Alpha downtube has a .3/.65 gauge. I do not think I am light enough (80kg) to use that. No mention of heat treating on that too.