Samuel D

The Dura-Ace FC-7400, FC-7402, and FC-7410 cranks all appeal to me for their low Q factor (tread), elegant design, and presumably high quality. I like the hard-edged design of the earlier ones, while the 7410 has a nice low-profile width across the bottom bracket – meaning its effective Q factor may be lower still if you need the ankle clearance.

Which of these is better from a practical, user perspective?

Mainly the bottom brackets worry me. For the 7400 and 7402, no-one seems able to definitively pin down the required square-taper standard. For the 7410, a 103 mm spindle length is needed but no longer available from Shimano.

I’m not sure of the differences between the 7400 and 7402, either.

Conversation welcome.

ThermionicScott 

Have you checked VeloBase.com yet? They indicate that all three are JIS, and take a 112mm BB for 7400 and 7402 (113mm for Italian frames), and a 103mm BB for the 7410.

Velo-Orange sells a 103mm cartridge BB that's currently on sale for $20 (a steal!) Tange-Seiki also makes 103/104mm BBs.

Hope this helps!

Samuel D

On the VeloBase page for the FC-7402, there is some debate in the comments about the correct bottom bracket.

For the 7400/7402, I’m worried a 113 mm cartridge bottom bracket (there being no 112 mm models) would not have the same symmetry (even if the taper geometry is right).

Maybe the 7410 is the better bet, even if it means going with a non-Shimano bottom bracket like the Tange Seiki you pointed out to me. However, part of the appeal of going back to square taper is improved bearing life. I trust Shimano more than anyone else in this regard.

Or perhaps I should get an FC-7400/7402 (what’s the difference?) and a NOS 112 mm Dura-Ace bottom bracket, and then service it myself often and carefully, hoping it would last ‘forever’ with good grease and periodic new balls. I’d need to get the tools for servicing those old-style bottom brackets, adding further to the cost of this option.

ThermionicScott 

Most of what I've read has leaned toward 7400+ BBs being JIS taper, or closer to it than ISO, but I don't have hands-on experience with much above 600/Ultegra.

An original DA spindle would be one way to make sure everything works as intended.

I tried "staying pure" with the loose-ball bottom brackets on my bikes for a while. Even with regular regreasing and careful adjustment, I still had a couple of spindles develop pitting. I gave up and went to the Shimano/Tange cartridges and have not had the first issue, many thousands of miles later.

Samuel D

Do you recall which grease you used on the traditional bottom brackets? I think premium grease would make a difference in this application.

Yeah, the Shimano square-taper cartridge bottom brackets last a long time with no fuss.

I wish Shimano would support these old products a bit better, but it probably makes no economic sense.

rccardr 

DA 74XX series is indeed JIS (said the guy with a bunch of it). The difference between 112 and 113 isn't worth worrying about. On some frames I've even used a 110. Sure, an original BB makes the finished product more collectible, but from a 'rider' standpoint, cartridge is easier to maintain.


While many people feel that 'grease is grease', on my personal collection I use only Phil Waterproof.

ThermionicScott 

Park Tool grease every time. I used plenty, and tried to keep on top of repacking them each time I'd been out in the rain, etc. Perhaps the aftermarket spindles I was using were inferior quality or something.

I was really bummed, because I like the idea of serviceable stuff you can keep using for decades.

P.S. One of the guys in the C&V forum noticed that www.loosescrews.com is back up. They have NOS 112mm spindles: https://www.loosescrews.com/product/...er-bb-spindle/

Samuel D

Just bumping this to see if anyone else has experience running the FC-7400, FC-7402, or FC-7410 with a Shimano cartridge bottom bracket, i.e. which one works and the resulting chainline.

Also hoping that someone on the whole internet knows the difference between the FC-7400 and FC-7402!

Thanks.

rccardr 

I own, build and ride all 3. JIS bottom brackets work fine and give you the proper chainline.

Personally, I would not be ale to tell the difference between a symmetric 112 and a 113, nor would I expect a half mm to dramatically change the chainline, but that's just me.

Plenty of nice to NOS DA bb's out there as mentioned previously, and not all that expensive. That Tange 103 would work as well as a Shimano, their products are excellent.

Could not tell you the difference between a 7402 and a 7400 crankset, although I believe that the 7402 was available in longer lengths. For example, I have a 177.5 7402.

CommaCam

Samuel, did you eventually build such a bike? I am working on a similar project with the FC-7400 but haven't done the final installation yet.

For what it's worth, I calculate a symmetrical-equivalent bottom bracket of 115mm for the FC-7400. FC-7400 originally used bottom bracket BB-7400, which was 3mm longer on the right spindle (see dimensions by searching google for "SI-N-69-000" [use the quotes for precision -- I'm sorry I don't have the cred to post links, but the top result should be the official Shimano FC-7400 service manual with a diagram of the BB-7400]). According to my calculations, the right half of the BB-7400 is 57.5mm, as measured from the mid-point of the bottom bracket shell to the far right edge of the drive-side spindle. I get this by adding length C to length B** divided by 2, or:

32.5 + (50/2) = 57.5mm

If true, this means 115mm is the symmetrical-equivalent bottom bracket which preserves the 43.5 chainline. The downside is that it appears to push the left crank outboard by 3mm as a result of the original asymmetry. (The original BB-7400 had a total width of 112mm, 57.5 of which was on the drive side and 54.5 of which was on the non-drive side. With a new symmetrical bottom bracket, the left side and right side are now equal at 57.5mm, adding 3mm to the non-drive side).

One issue I actually ran into was frame clearance. A symmetrical 113mm (a suggestion I saw in several places) puts the FC-7400 uncomfortably close to my chainstays at both the big ring (53t) and the drive-side crank arm. 115mm backs it up just far enough that I am reasonably confident it will not strike the frame, so I'm willing to live with an extra 3mm on the non-drive side (which is easily correctable with foot position).

**I assume the center part of the BB-7400 was designed to be centered over the frame shell and thus can be used as a proxy measurement for the right half of the bottom bracket. Is this true?

Samuel D

I didn’t get enough solid information to be confident I would find a suitable bottom bracket at a reasonable cost, so I never ordered one of these cranks. There is also the JIS versus ISO question to worry about.

However, just a couple of weeks ago a friend gave me a FC-7410, so your post is a timely reminder to look at this problem again. (The first thing that surprised me was that the FC-7410 was anodised. Somehow I’d thought it was polished like the older Dura-Ace cranks.)

Here (PDF for other readers).

That makes sense given your above sleuthing, but how do you know your 113 mm is symmetrical? That info is not always published.

Don’t know, but that’s what I’d guess too. The last page of this Tange Seiki catalogue (PDF) has a “BB chart” from which the asymmetry, if any, of Tange Seiki bottom brackets can be deduced. The LN-7922 seems like an affordable, light, and high-quality option in one of those lengths (113.5 mm?). Made in Japan like the cranks, too!

For my FC-7410, I’ll need something a lot shorter.

Frame clearance is of course necessary, but for chainline purposes we should take into account that we may be running wider hubs (130 mm?) with wider cassettes than the original 6-, 7-, or 8-speed Dura-Ace freewheels and cassettes.

CommaCam

You know, perhaps I stand corrected on the 113. Unfortunately I don't have it around anymore to measure, but I do have a 115 (which I tentatively plan to use with the FC-7400) and also a 110 that I have lined up for a different bike. Both of them are Shimano BB-UN55. The 115 is symmetrical (or close enough to be negligible) -- but the 110 is definitely not. The drive-side spindle is shorter on the 110 than the non-drive spindle, a bit like the 111 in the Tange catalog you linked above (great find, btw).

But be that as it may, the 113 was still too close to my chainstay. It technically cleared, but it made me really nervous to see it that close (and this was before torquing it down, which would have made it worse). Plus I feel pretty good about the math -- to preserve the original 43.5 chainline, one would need 57.5mm on the drive-side of the bottom bracket. Looking at the Tange diagram (for 68mm shell widths), that would be the 115 just as with the UN55 (for Tange, take lengths D/2 + JR = (68/2) + 23.5 = 57.5mm). I think your idea of 113.5 would also work very well. It would seem to bring the drive side inboard by .5mm (basically negligible) but would improve the left crank position compared to the 115.

As for ISO/JIS, I found a thread here that seems to resolve that question solidly in favor of JIS. The thread name is "BB for DA 7402 cranks". (And note that the Sutherland charts posted there are total BS.)

Also, the 7400 is definitely anodized as well. I have it here and can see the gleamy sheen all over it, which is so nice.

Yes the BB-7410 is significantly shorter (103) as those cranks were designed to be "low profile" cranks. Which opens up another question.... What exactly does Shimano mean by "low-profile" in that context? Do they mean it colloquially, or are they referring specifically to the "low profile JIS taper" spindles, a shorter version of the JIS taper. Sheldon discusses this briefly in his article about bottom bracket interchangeability, but doesn't really go into detail about the dimensions. Shimano has the old service manual available for BB-7410 ("SI-1TA0A-000-00-ENG_FRA"), but they don't clarify this other than simply calling it "low profile". This might be something you just dive into and experiment with until you find the right BB.

Your point about rear hub width is also an excellent one. FC-7400 appears to have been designed for 125/126mm. My bikes are all 130s. If I'm imagining this correctly, putting an FC-7400, with its original 43.5 chainline, on a bike with 130mm rear spacing should effectively move the chainline inboard slightly with respect to the rear cassette (I'll be running 8-speed on this bike, fyi). If true, then I actually like the sound of that. I so seldom use the small cog in the rear that a slight bias up the cassette might actually be a good thing for me. For reference, Park Tool calculates an approximate 43.1mm rear chainline for an 8 speed Shimano cassette on a 130 frame. So if I can get the FC-7400 to approx 43.5, that puts my front and rear chainlines into a very nice balance for my normal shifting/riding style.

Samuel D

News to me! It therefore makes sense that the intermediate FC-7402 would also be anodised as indeed is specified on this brochure page.

PDF here. Thanks for the pointers.

CommaCam

I got my hands on an FC-7410 with the original BB-7410 bottom bracket.

68mm shell
103mm total length
17.5mm spindles protruding from the 68mm shell on both sides

I did this with an old-fashioned vernier caliper using the same measurement points as in the Tange catalog above. The Tange 103 is close enough that it should work fine (although the Tange is slightly asymmetrical with spindles of 17 and 18mm rather than 17.5x2).

Assuming my caliper skills are adequate, the "low profile" language appears to refer to the length of the JIS taper. The taper starts out at what looks like the exact same width at the end of the spindle as a normal JIS BB -- it's just a shorter taper section and slightly narrower at the point where the taper ends (the wide part). The usable taper section of the BB-7410 is approx 15mm long. The taper section of a modern BB-UN55 is approx 18mm. When I set the caliper at the bottom (widest) width of the BB-7410 taper, and then move it over to the BB-UN55, it goes on the same 15mm length, leaving approx 3mm of irrelevant taper on a modern JIS spindle.

verktyg 

Jumping on to the Zombie thread...

I recently got a set of NOS Shimano FC-7410 Cranks. I was looking for a Shimano 103mm BB cartridge to go with them. Looks like 107mm is the shortest square drive cartridge still made by Shimano.

I checked out a Tange Seiki 103mm BB cartridge today. It had steel "cups" and was over $40.00 so I decided to try a new Shimano BB-UN55 107mm BB with aluminum cups for $25.00 instead. 4mm is only a .157" difference.

For starters, the Shimano 107mm BB-UN55 measured 108mm overall length not 107mm.

The drive side is 21.2mm from the BB shell so it's 3.7mm longer than the 103mm Shimano BB-7410 BB. - less than 4mm.

The adjustable cup side is 18.3mm long.

Here's the BB spec sheet from the above mentioned Tange Seiki catalog. Note overall length L is ± 1.0mm so the Shimano 107mm BB is within the manufacturing tolerances of the Tange 107mm BB.



A few things to considers, once cranks have been mounted onto a spindle the soft, malleable aluminum deforms to match the taper of the spindle. Repeated removal and replacement further deforms the squares in the crank arms.

ALL OF THE FRETTING AND HAND RINGING OVER JIS vs. ISO TAPERS IS A BUNCH OF HORSE PUCKY! IF IT FITS IT WORKS!

I recently mounted a set of Stronglight 93 cranks on a Campagnolo Centaur/Veloce cartridge. No problem! I had to put two 1mm spacers under the fixed cup because the BB shell was 66mm not 68mm.



This shows how far the crank seated onto the spindle when torqued down. If it were a bike that I planed to ride a lot, I'd use a different BB but these sealed bearings are going to far outlast me.



I did this Flickr album in a hurry about 10 years ago when I was looking for a BB to build a SS wet weather beater. Click on the photos and scroll down to see my notes.

https://www.flickr.com/photos/282672...57627678462359

An important thing to check for when doing mix and match setups is how far the crank fits onto the spindle.



Check it out by hand first to see how the crank fits onto the spindle like above.

Next put the spindle in the BB hand tight with caged bearings and no grease to check to see how much clearance there's going to be between the chain rings and the chain stays. The crank arm with seat at least 2-3mm further onto the spindle when it's torqued down.

To answer the question about "low profile" cranks, this info from Sutherland's 5th shows the difference. BTW as noted above, BITD some of the specs in the older Sutherland's Handbooks were: HUH???



Hope this helps...

@CommaCam Thanks for posting the specs on the FC -7410 and BB-7410. It saved me a lot of searching.

verktyg

verktyg 

Addendum to what I mentioned above about checking fit by hand.

Front side to check on insertion depth.



Rear side fit



This allows you to guesstimate whether the spindle and crank will fit properly on your frame.

verktyg

CommaCam

Very welcome. I tend to think there's no such thing as a "zombie" thread when discussing 30 year old cranks, but maybe that's just me.

Fwiw, I put mine on my town bike -- an old aluminum road bike -- as a 1x8 with a 42 front (big ring position), 11-28 rear. When I mounted them on the bb-7410 (103mm), I found the chainline was absolutely perfect, with no spacers or other modifications needed to get up and down the rear cluster and avoid the common 1x pitfalls, which suggests my copy of the cranks (very well used but with a surprisingly attractive "patina" to them) were likely spread out from multiple prior applications as you noted above. But it doesn't bottom out, doesn't creak, etc., so I'm very happy with it. To make it a 2x, I would almost certainly have to move to a 107mm.

One thing I constantly marvel at is how absolutely dead sexy these cranks are. They have such a pleasant shape and finish to them, and no gaps at all between the arms and bb shell -- from a distance it almost looks like one continuous piece of hardware, which is so, so cool.

ThermionicScott 

Good stuff, as always @verktyg.

Robiiiii

Hi guys, I'm working on a Look Team replica KG96, I've only got the frame but I believe it originally came with the option of running Shimano DA 7400. I'm trying to replace the BB and was wondering if any of you knew what I should be looking for or how I could find out... or maybe if there are any modern alternatives I could run?

Any help would be super appreciated!! : )

R

rccardr 

Couple of options, all good:
1) New or lightly used DA 7400 113mm bottom bracket. Lots out there, eBay particularly, in both english and italian threading. Pick what you need and go from there. Pricing usually from $40-$125$ depending on new vs. used and how greedy the seller might be
2) Any Shimano or Phil bottom bracket that's in the 112-115 range. Cartidge ones work just fine, last pretty well darn forever. Again, pickk your bottom bracet cup size correctly.
3) Any japanese style and sized cup and cone bottom bracket with a 112-115 spindle and, again, correct cup size. Some like these better because they have less resistance from the get go as seals do not need to be broken in, others not so much because they require periodic maintenance. You can even mix and mtch from time to time with NOS spindles that will work with non DA cups, I have one such combination for a future italian thread build, Sugino cups and bearings with a NOS italian DA spindle.