Just as a little point about how nice the bicycles were, who among Retrogrouch Blog readers wouldn't start salivating like one of Pavlov's dogs over a mid-'80s mint condition red Specialized Allez SE with SunTour Superbe components, just like the bikes from the 1985 film American Flyers? . . . Exactly. Also, I have one of the early Stumpjumpers with the lugged frame and twin-plate fork crown, and the workmanship on that frame is fantastic.
Anyhow, as I'm gathering up components for a bike build, I thought I'd take a close look at one of my favorite triple cranksets - the Specialized ST, sometimes known as the "flag" crank because of the logo engraved on the arms. It's a really well-designed crank - simple, pretty, and strong. I've used them on a few bike builds over the years, whether built for myself or for others.
|It's the kind of design that looks good on a bike whether new or old.|
I was able to get some info about the cranks from Jim Merz, who had been one of the pioneering framebuilders in the Portland, Oregon bike scene until he went to work for Specialized as a product designer in 1982. He has also been a "Master Frame Builder" for the company. Jim was the designer of these cranks, and many other high-quality components. According to Jim, the cranks were cold forged, using the strongest alloys available, and with rings made from 7075 T6 aluminum - the same as was used by Campagnolo. As mentioned, the cranks were manufactured for Specialized by Sugino.
|As a contrast, the sharp transition between the arm and the spider on this old Campagnolo crank serves as a stress riser, where cracks could develop. Lots of old Campy cranks suffer this fate. With continued use, a crack like this could eventually break all the way through. (photo, minus added text, from fixed.org.au forum)|
Another detail about the crank that makes it very versatile is its 110/74 bolt circle diameter (BCD). Though that would quickly become the most common standard for triple cranks for the next couple of decades, it was still a pretty fresh development when this crank was designed.
|The crank used the 110/74 BCD which means that chainrings are easy to find, even today.|
In the 1970s, as long-distance touring bikes gained popularity (especially after the epic Bikecentennial ride of 1976), and then at the end of the decade when mountain bikes were in their infancy, finding a good wide-range triple crank with seriously low gearing wasn't so easy. There were numerous "standards" for bolt circle diameter, and very little compatibility between different brands. One of the more popular choices for tourists and early mountain bikers was the TA Cyclotourist -- not necessarily because they loved the crank so much (it had some idiosyncrasies) but because it could be had with a then-diminutive 26 tooth granny ring. The TA had a tiny 50.4 mm BCD onto which the biggest chainring bolted. Then the middle and inner rings bolted directly onto the outer ring with an 80 mm bolt circle. One downside of the crank was that the space between the rings and the crank arm was so narrow that it could create interference with some front derailleurs. And the whole thing bolted together with a confusing mess of different sized nuts and bolts. Also, larger chainrings on the TA crank could lack stiffness. The bigger the ring, the more it could flex. Still, for many people, and for quite a while, it was the best thing going.
Stronglight had certain models that were very similar to (or interchangeable with) the TA Cyclotourist, but they also had other, more modern triple cranks (their model 99 comes to mind, for example) that used a proprietary 86 mm BCD. Those were also copied by Sakae Ringyo (SR) and used on some of Trek's early touring bikes. They were decent triple cranks, but the smallest chainring one could install was 28 teeth. Low, but not low enough for some tourists and mountain bikers.
When Shimano released its original Deore group in 1981, which was intended to be a premium group for touring bikes, the first generation Deore crank copied the 50.4 BCD used by TA. But in typical Shimano fashion (does not play well with others), only the outer ring was interchangeable with the TA Cyclotourist. The middle and inner rings used a proprietary 85 BCD, making them compatible with nothing else. It also meant that the lowest gear was limited to 28 teeth.
In 1982, Sugino released the AT triple crank. "AT" stood for "Aero Tour" but it probably wasn't a coincidence that it was just like "TA" backwards. The AT had the outer and middle rings bolted to a 110 mm circle, which could accept rings as small as 34 teeth (They also offered rings as large as 53 teeth, but nowadays it's hard to find them larger than 50). A second set of threaded holes was set into the spider with a 74 mm bolt circle, which could accept a granny ring as small as 24 teeth. Altogether it was a good combination. The larger rings still got plenty of support, avoiding the flex that would come with a smaller bolt circle. Middle rings could be as small as 34, and the 24 tooth granny ring was about the lowest gear anybody was offering at the time. I remember a number of bikes in the '80s, especially sport-touring models, that came with 110/74 cranks that were set up as doubles. Turning them into triples if the owner wished was a simple operation. The cult-bike Bridgestone XO-1 came equipped like that, too.
As Jim Merz tells me, he designed the Specialized crank in 1983, using the same 110/74 BCD. Sakae got a version on the market very quickly. When Shimano redesigned their Deore crank, around '84, they made a rare choice to adopt 110/74 as well. Pretty soon many in the industry were embracing a common standard for triple cranks. Even TA started making cranks and rings to the standard. And there was much rejoicing.
As usual, the idea of common standards has gone out the window, and cranks today are all over the place. Innovations such as MicroDrive in the '90s made bolt circles and chainrings even smaller (more ground clearance for mountain bikes, I guess), and now more and more cranks have discontinued 5-bolt spiders in favor of 4-bolt versions - many with their own unique asymmetrical bolt patterns, and others with removable spiders. But luckily 110/74 rings were once very common and can still be found today without trouble.
The ST triple crank had a less expensive sibling, designated as the ST-4. Overall, the cranks looked very similar, with the most obvious difference being the logo. However, the real difference between the two was not in the logo, but in the manufacturing. The ST crank was cold-forged out of the strongest available aluminum alloy, whereas the ST-4 was made by the process known as gravity casting -- sometimes mistakenly called "melt forging" but there is a difference. Read on . . .
|That's the cold-forged ST on the left, and its similar-looking sibling (minus rings) on the right. The model designations are marked on the back, but the logo ("flag" vs. "S") is a quick identifier.|
Cold Forging vs. Hot Forging vs. Gravity Casting vs. Melt Forging
They're all fine ways to make a bicycle crank, but differences in methods and materials affect the strength - and differences in the manufacturing cost obviously affect the price. A really good description of all the methods can be found in the 1992 Bridgestone catalog, but here's a quick summary:
Cold forging starts with the strongest alloys, and requires several major wallops (not a technical term) with hardened forging dies with tons of weight and pressure -- as in, hundreds of tons. Cold forging imparts a grain structure that makes the component very strong, but the tooling and equipment mean more expense. Very few bicycle component makers can afford the massive forging "hammers," and therefore most actually have their cold forging outsourced to specialists. Because of the added strength, cold forged components, like cranks, can be made sleeker and lighter. By the way, Jan Heine's blog had an interesting article last year about forging hammers and the companies that do such work (HERE).
Hot forging involves alloys that are slightly lower in strength than cold forging (though still very strong), heating them to make them softer, then giving them typically one or two hard wallops in the forging dies. It still imparts a grain structure to the component so the parts are very strong, but it takes fewer wallops and less tooling so the cost is lower.
Gravity casting and melt forging both involve melting alloys that start out as somewhat lower strength from either of the previously described methods - but between the two, gravity casting uses a stronger alloy than melt forging. In gravity casting, the molten metal is poured into a mold, then allowed to cool slowly while any air bubbles that might be present gravitate upward and out. In melt forging, the molten metal is forced into a mold under pressure, then liquid-cooled quickly. It is the fastest method and probably requires the least expensive tooling, though the material is not necessarily as strong, nor do the parts develop the same kind of grain structure. For that reason, melt-forged components tend to be "chunkier" to make up for it. Melt forged components also don't take to anodizing, so the finished products are often painted or powder coated. It goes without saying that melt forging is the least expensive of the described methods.
By the way, the '92 Bridgestone catalog says that the Specialized ST-4 crank was gravity cast, but then got extra strength by being whacked in a forging die for good measure. How cool is that?
Cranks in the Vintage Market:
If you're looking at either of these Specialized cranks on the vintage marketplace, like eBay, keep in mind that the prices will vary more by condition than by the model of crank. Most buyers and sellers on eBay or elsewhere probably don't really know the difference between the two versions, nor do they know or care what the things sold for when new. A really clean ST-4 will probably sell for more than a badly scuffed ST, regardless of what the original prices might have been. It's good to know what you're getting, though. Sometimes I see these selling for $100 or more, but unless it's unused, mint-in-the-box, I'd say that's ridiculous. Clean used examples like the ones shown above can often be found for under $50.
I love this kind of post. Very interesting. Keep it up and thanks.ReplyDelete
as a person with Sugino AT cranks on two bikes, I love it for its quality and the ability to configure it as either a double or triple. Since the Specialized crank was developed after the AT, I wonder why they bothered? Was it just to get the cast-in bosses for the triple, which might reduce costs a bit?ReplyDelete
I don't think I could answer that one. However, I neglected to mention (since I was focusing on triples) but they also made a similar-looking racing double crank with a larger BCD. I don't know for sure, but based on what I've seen out there, I have a feeling the triples sold more than the doubles.Delete
I just love those cranks.ReplyDelete
Are the Specialized cranks yours, or did you find those pics online?
Both of those are mine. I'm planning to use one of them soon, though I may take off the granny ring and run it as a compact double.Delete
Ahh, nice. They look to be in pretty good condition.Delete
46/36/26, looks like. Keep the 46, I'd guess, and switch the 36 for a 34? Or you could go the Riv route and do 46/30.
Heh, I love projects and new builds, even when they're somebody else's.
Thanks. I could go 46/34, though I could also go 48/34. Or 48/36. I've got enough rings to do a little experimenting. Nice to have choices.Delete
Had a Merz adaptor , Sugino Road adaptor middle ring ,allowed TA small rings .Back in the day,I put it on a "Trailmaster", Phil hubs and B.B., Mafac tandems, proud ride .ReplyDelete
I've heard or the Merz adaptor ring -- but I don't think I've ever seen one in person -- just pictures.Delete
Those were great cranks indeed. I have a Sugino Alpina double on one bike and an '80's Deore on another. Really, I don't see any reason to use anything besides a 110 or 110/74 BCD, unless you're racing.ReplyDelete
I really enjoyed reading this. Thank you.ReplyDelete
Pardon me if I've shared the following before. http://davesbikeblog.squarespace.com/blog/2014/3/12/46-big-ring.html http://davesbikeblog.squarespace.com/blog/2014/3/24/more-on-practical-gearing.htmlReplyDelete
Really great article, thanks for writing it! I like these old Sugino 110/74 triples and it's interesting to read about how they are made and some history on them. Sometimes you can find really nice ones on old non-suspension mountain bikes that few people seem to really want anymore.ReplyDelete
https://goo.gl/photos/scZFiioH3Hm6nqCYA Some shots of a perfect 1983 Sequoia with the forged flag crankset. Jim MerzReplyDelete
Thanks, Jim -- that is a really sweet bike.Delete
Just bought a set of these labeled "Stumpjumper" cranks and they turned out to be doubles, were these also cold forged? or same forging, different machining?ReplyDelete
Unfortunately, I don't have the answer to that. Maybe someone else out there can speak to that.Delete
Definitely a different forging, because the doubles are 144bcd. Great article, thanks for making me smarter!ReplyDelete
Hello--first post and I'm not sure what my name will appear as.ReplyDelete
I just bought a tapered square triple crank -- Sugino but branded Specialized.
Ebay link is -- http://www.ebay.com/itm/252421355709?_trksid=p2060353.m2749.l2648&ssPageName=STRK%3AMEBIDX%3AIT
I'm trying to figure out whether I need a 68x107 or 68x110mm bottom bracket to put it on my Giant 980c road bike and run with a 7spd shimano drivetrain. I have 3x7 spd STI levers to complete the setup.
Any ideas on which BB size will provide the proper chain line?
I believe that Specialized recommended a 115 with that crank when used as a triple. Here was something I found on one of the forums that might help : http://www.bikeforums.net/classic-vintage/900765-bottom-bracket-length-specialized-flag-emblem-touring-crankset.htmlDelete
My own crank is currently set up as a 2-ring crank with 34/48 rings -- and I'm pretty sure I used a 110 bottom bracket to make that work (I say pretty sure, but I cannot check it for certain at the moment - and to know for sure would mean taking off the cranks to measure it).
I am mid way through the process of putting an old ST-4 on a Specialized sirus (1980s vintage) The current bb is 113 mm shimano cart and its too short. It looks like 3 or 4 mm of too short so I am going with a 118. UN55 I am going to buy it at the local rei cause they will take it back if I get the wrong length.Delete
BTW I scored my ST-4 at a thrift store for $5. Looks like I will be able to go from a double to a triple for less then $30, I already had an ultegra triple rear derailleur. Good luck.
Do you know if the ST-4's that were made by gravity casting still have the word "Forged" stamped into the end of the arms where the length is also stamped?ReplyDelete
Mine doesn't say "forged" or "cast" or anything of the sort.Delete
I'm not 100% sure, but my memory is that the 74mm bolt circle was first introduced on the Avocet/Ofmega cranks, which used a 144mm bcd for the outer rings, but the spider was drilled for the 74mm circle on their triples. Pretty sure those pre-date the Sugino AT.ReplyDelete
You may be right about that. They did offer a 74 mm bcd, and its possible they predate the Sugino. But it's the combination of 110/74 that really caught on for triples - as opposed to 144/74 which gave the really low granny gear, but the middle gear couldn't be lower than 42 teeth (41 could be found, but was really pushing it - as there was virtually no metal left around the bolts).Delete
Hello there, great write up ... beautiful crankset too, I had the triple on a '93 red Bridgestone MB2 - fantastic bike! Can you give any info on the spindle size? You say it was shorter than most ... do you think the following data is accurate?ReplyDelete
If so, for the Flag double, would you use the Specialized (Eng./Fr.) measurement of 107mm, or the Sugino (Eng./Fr.) 112mm measurement?
That image was, I believe, from the Specialized catalog from that era - it is probably a good guide for what you need.Delete
To clarify, in case it is needed, my old MB2 had the Specialized "S" branded crankset ... I now have the Flag branded double - (with Specialized dust caps though) ... and am wondering which spindle I need. Thanks!ReplyDelete
Any idea what the E-4 vs. E-5 on the back of the arms (of a double) indicate? I just bought a set on eBay that had one of each ... wondering if they are mismatched?ReplyDelete
Just checked my doubles, both stamped D6 Sugino date codes D=1984 6=June... looks like you have April/may 1985. I bet they shipped like that all the timeReplyDelete
Thanks for the info J. I also thought that may be be a possibility.ReplyDelete
FYI - Using https://www.sheldonbrown.com/cribsheet-bcd.html as a guide, it appears the Specialized "Flag" double, has 144 BCD.ReplyDelete
Just came across a 170mm ST set that I don't have a use for. Anybody interested in snagging it? Unfortunately the chainrings are mismatched and beat up, but the crank is in good condition.ReplyDelete
Do you know what size bottom bracket the st-4 requires?ReplyDelete
After reading your article, I purchased a used Flag Triple crankset minus the chainrings in good used condition. I found a brand new Specialized 46t chainring and also purchased a Vuelta 28t and a 36t. I replaced the old Exage 400 LX crankset on my 1992 Specialized Rockhopper. My BB has a 122.5mm spindle length and it works just fine with that. It looks great on the bIke and it was a fun project. I was very impressed with the quality of the crankset and chainring. Thanks for the great article. It can be hard to find good information on older components. I would love to see you do one on the 1990's Era Future Shock suspension fork. I have a vintage rebuild kit, but can't find decent instructions.ReplyDelete
When I built up my custom MTB tandem and my Salsa a la Carte in about 1985, I used Specialized ST cranks on both bikes. Thirty-five+ years later they're going strong, though the set on my Salsa are much more worn. I bought the cranks through a friend in the industry, who advised me to buy an extra set. This set still sits in the original box in my garage; they're too beautiful to use!ReplyDelete
Lately, those TA Cyclotourist cranks have become fashionable, especially with randonneurs. But I agree with the author that they are lacking. I tried them on my Jack Taylor in the 1970s and I found them awfully flexy.ReplyDelete