Early Dura Ace Hub Questions
09-18-22, 06:35 AM
#1
Senior Member
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Early Dura Ace Hub Questions
Good morning. So I have this early model Dura Ace rear hub. I an unsure what model it is. Dura Ace painted lettering has worn off. Dust caps say "Dura Ace" Uniglide freehub has evenly spaced splines, I am told only an early Dura Ace casssette fits. So my questions are:
A. What model hub is ths?
B. What cassette fits it?
Thank you.
A. What model hub is ths?
B. What cassette fits it?
Thank you.
09-18-22, 06:52 AM
#2
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Check with Velobase for sure, but I would say DA 7200, which I believe came in both freewheel and freehub styles.
Any UG cog will fit that hub pattern but you’ll need a special ‘reduced internal diameter’ first cog to tighten everything down. They got as small as 12 teeth.
Cogs are out there, lots on eBay..
You can also slightly modify any HG cog with a file or Dremel tool to fit all but the first position, by widening the single narrow notch.
Any UG cog will fit that hub pattern but you’ll need a special ‘reduced internal diameter’ first cog to tighten everything down. They got as small as 12 teeth.
Cogs are out there, lots on eBay..
You can also slightly modify any HG cog with a file or Dremel tool to fit all but the first position, by widening the single narrow notch.
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09-18-22, 08:46 AM
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I have purchased 1st position cogs for these early DA hubs from Loose Screws. Brand new and good turn-around time on the order.
Dean
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09-18-22, 11:42 AM
#4
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Uni Glide.
Other than the screw on end cog, you can take HG cogs and widen the narrow spline to make them fit.
The flat cogs can also be flipped to "double" their life.
Apparently, Dura Ace screw on cogs have a different thread diameter than other Shimano screw on cogs. (flat cogs have same spline though)
I've never dealt with these, but maybe Andrew Stewart, FBinNY or others can fill in the details.
Other than the screw on end cog, you can take HG cogs and widen the narrow spline to make them fit.
The flat cogs can also be flipped to "double" their life.
Apparently, Dura Ace screw on cogs have a different thread diameter than other Shimano screw on cogs. (flat cogs have same spline though)
I've never dealt with these, but maybe Andrew Stewart, FBinNY or others can fill in the details.
Last edited by Bill Kapaun; 09-18-22 at 11:57 AM.
09-18-22, 02:38 PM
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No FH-xxxx stamped in the hub between the two spoke flanges? Then we'd all know better what is being dealt with. I think it was usually 180° opposite of the Shimano Stamp. But it might have been a label or ink printing that wore off instead of being stamped into the aluminum.
09-19-22, 06:07 AM
#7
Senior Member
I'm fairly sure that rcdardr is correct that it's from the Dura Ace EX 7200 family. However, Shimano documentation archives list 4 different FH-72XX hubs:
FH-7250: 5 speed, 120mm OLD
FH-7260: 6 speed, both 120 mm and 126mm OLD
FH-7261: 6-speed, 126mm OLD
FH-7271: 7-speed, 126mm OLD
The FH-7261 and FH-7271 had what Shimano termed "Direction System" hub flanges. Essentially, these appear to have been stepped flanges that allowed all spokes to be inserted from the inside of the flange without mutual interference when crossed. (Shimano claimed it improved wheel strength, but it didn't catch on and appears to have been discontinued.) The stepped flanges are shown in diagrams and/or pictures found in Shimano's documentation.
Your hub doesn't seem to have those stepped "Direction System" flanges, so it's likely either a FH-7250 or a FH-7260. Lack of those same stepped flanges also rules out it being a a Dura Ace AX FH-7360 or FH-7370-R that's missing its NDS aero dust cap, since both of those hubs also had the "Direction System" flanges.
Since the FH-7260 was made in both 120mm and 126mm OLD versions, you'll need to measure the length of the freehub to ascertain which it is. If I recall correctly, a Shimano 6 or 7 speed freehub should have a length of around 30-32mm. A 5-speed freehub would be significantly shorter, probably by at least 5 mm (not sure, never seen one and couldn't find any info on width of a 5-speed Shimano freehub).
Per the Shimano docs, the smallest available screw-on last cog was an 11T cog. I've read elsewhere that that allowing the use of an 11T smallest cog was the reason the Dura Ace used smaller internal diameter threading for the early Dura Ace freehubs.
To find the appropriate available Shimano docs, follow the link above. Or you can enter the model numbers above manually (e.g., "FH-7250") in the appropriate data field on the webpage linked above. (There's no separated exploded view for the FH-7261 and FH-7271; those exploded view diagrams - along with that for the corresponding front hub - are are found in one of the two SI docs that come up on the search.)
If it's a 5-speed, I'm thinking you've caught a unicorn. But you're not out of luck; according to the late Sheldon Brown's cassete/freewheel spacing cribsheet, 5-speed and 6-speed used the same cog spacing and width. So you should be able to use loose 6-speed Uniglide cogs and spacers on it to gear it as you like. Using modified 7-speed Hyperglide cogs for the largest 4 might (or might not) also be a possibility if you use 7-speed spacers and add a 1.5mm or 1.8mm spacer behind the largest (7-speed cogs and spacers were each a bit narrower than 5 or 6 speed cogs/spacers - if I've done the math right, using 7-speed cogs and spacers 4 cogs and 3 spacers would be 1.65mm narrower than their 6-speed counterparts). But you'll definitely need a threaded smallest cog in either case.
Hope this helps. Best of luck.
FH-7250: 5 speed, 120mm OLD
FH-7260: 6 speed, both 120 mm and 126mm OLD
FH-7261: 6-speed, 126mm OLD
FH-7271: 7-speed, 126mm OLD
The FH-7261 and FH-7271 had what Shimano termed "Direction System" hub flanges. Essentially, these appear to have been stepped flanges that allowed all spokes to be inserted from the inside of the flange without mutual interference when crossed. (Shimano claimed it improved wheel strength, but it didn't catch on and appears to have been discontinued.) The stepped flanges are shown in diagrams and/or pictures found in Shimano's documentation.
Your hub doesn't seem to have those stepped "Direction System" flanges, so it's likely either a FH-7250 or a FH-7260. Lack of those same stepped flanges also rules out it being a a Dura Ace AX FH-7360 or FH-7370-R that's missing its NDS aero dust cap, since both of those hubs also had the "Direction System" flanges.
Since the FH-7260 was made in both 120mm and 126mm OLD versions, you'll need to measure the length of the freehub to ascertain which it is. If I recall correctly, a Shimano 6 or 7 speed freehub should have a length of around 30-32mm. A 5-speed freehub would be significantly shorter, probably by at least 5 mm (not sure, never seen one and couldn't find any info on width of a 5-speed Shimano freehub).
Per the Shimano docs, the smallest available screw-on last cog was an 11T cog. I've read elsewhere that that allowing the use of an 11T smallest cog was the reason the Dura Ace used smaller internal diameter threading for the early Dura Ace freehubs.
To find the appropriate available Shimano docs, follow the link above. Or you can enter the model numbers above manually (e.g., "FH-7250") in the appropriate data field on the webpage linked above. (There's no separated exploded view for the FH-7261 and FH-7271; those exploded view diagrams - along with that for the corresponding front hub - are are found in one of the two SI docs that come up on the search.)
If it's a 5-speed, I'm thinking you've caught a unicorn. But you're not out of luck; according to the late Sheldon Brown's cassete/freewheel spacing cribsheet, 5-speed and 6-speed used the same cog spacing and width. So you should be able to use loose 6-speed Uniglide cogs and spacers on it to gear it as you like. Using modified 7-speed Hyperglide cogs for the largest 4 might (or might not) also be a possibility if you use 7-speed spacers and add a 1.5mm or 1.8mm spacer behind the largest (7-speed cogs and spacers were each a bit narrower than 5 or 6 speed cogs/spacers - if I've done the math right, using 7-speed cogs and spacers 4 cogs and 3 spacers would be 1.65mm narrower than their 6-speed counterparts). But you'll definitely need a threaded smallest cog in either case.
Hope this helps. Best of luck.
Last edited by Hondo6; 09-19-22 at 03:45 PM.
09-19-22, 06:19 AM
#8
Senior Member
No FH-xxxx stamped in the hub between the two spoke flanges? Then we'd all know better what is being dealt with. I think it was usually 180° opposite of the Shimano Stamp. But it might have been a label or ink printing that wore off instead of being stamped into the aluminum.
I'm pretty sure Shimano has done all three of those when it came to marking their hubs with model numbers. And I've seen at least one where the hub marking was on one of the dust caps - I've got a pair of old FH-HG20s with the model number stamped into the metal NDS dustcap.
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