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The Punk Hucker
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3,755 Posts
Discussion Starter · #1 ·
I'm having problems finding the right dimensions for a Shimano FH-M756 rear hub. Using the database in the spocalc, I have two different values. The DT swiss spoke calculator gives a third set. The Shimano's website gives a fourth set...

What the hell? How hard is it to have values for this hub...

Anyways, anybody ever hand measured them or used some values in spocalc successfully?

Thanks!
 

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Premium Member
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48,238 Posts
PissedOffCil said:
I'm having problems finding the right dimensions for a Shimano FH-M756 rear hub. Using the database in the spocalc, I have two different values. The DT swiss spoke calculator gives a third set. The Shimano's website gives a fourth set...

What the hell? How hard is it to have values for this hub...

Anyways, anybody ever hand measured them or used some values in spocalc successfully?

Thanks!
IME all of the Shimano 6-bolt hubs are the same dimensions. If in doubt, measure them yourself (best in any case, as always).
 

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The Punk Hucker
Joined
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3,755 Posts
Discussion Starter · #8 ·
I ended up measuring them, just for the sake of being precise. So I got the bike out of the pile, unlaced the wheel and measured. It turns out the values from DT swiss are pretty close but a little off, same as those from Shimano. The 2nd row in spocalc (that reads Shimano Deore XT FH-M756-L) is completely wrong (45mm spoke hole diameter?????)

So the right value are
61mm PCD
19.75mm C-R
33.25mm C-L
2.6mm SHD

It's close enough that it gives the same spoke length as DT's value and as spocalc's 1st row, but it's a 5th spec...
 

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transmitter~receiver
Joined
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9,334 Posts
PissedOffCil said:
I'm having problems finding the right dimensions for a Shimano FH-M756 rear hub. Using the database in the spocalc, I have two different values. The DT swiss spoke calculator gives a third set. The Shimano's website gives a fourth set...

What the hell? How hard is it to have values for this hub...

Anyways, anybody ever hand measured them or used some values in spocalc successfully?

Thanks!
It's not hard at all. Call Shimano.
(800) 423-2420
 

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transmitter~receiver
Joined
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9,334 Posts
PissedOffCil said:
Shimano's values are not right... But maybe you should have read the whole thread don't you think?

And no need to call them to get bad values : http://bike.shimano.com/publish/con...roduct.-code-FH-M756-L.-type-fh_mountain.html
mmm... I did read the whole thread.
I trust Shimano's dimensions over yours all day long. Measuring hub dimensions (particularly flange off-sets) to the 0.1mm or 0.01mm can be a bit tricky, especially for someone who's 'lazy' (your words). Using somebody else's (DT Swiss', in this case) specs for a product that is not theirs based solely on 'XT' and '6-bolt' is a crap shoot and should carry no weight. I have built many wheels with Shimano hubs using Shimano dimensions obtained by calling them and have never had a problem with spoke length. Not once... ever.
I'm sure you'll be fine.
How'd you get to that page, BTW? I couldn't get there on my own, either by searching or navigation.
 

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transmitter~receiver
Joined
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9,334 Posts
PissedOffCil said:
I ended up measuring them, just for the sake of being precise. So I got the bike out of the pile, unlaced the wheel and measured. It turns out the values from DT swiss are pretty close but a little off, same as those from Shimano. The 2nd row in spocalc (that reads Shimano Deore XT FH-M756-L) is completely wrong (45mm spoke hole diameter?????)

So the right value are
61mm PCD
19.75mm C-R
33.25mm C-L
2.6mm SHD

It's close enough that it gives the same spoke length as DT's value and as spocalc's 1st row, but it's a 5th spec...
There is only one 'spec' (specification), and it is obtained from Shimano. Everything else is an approximation, estimation, or measurement, and subject to additional layers of error.
Question: if they all give the same spoke length (with the obvious exception of the spokecalc outlier), what does it matter?
 

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meow, meow.
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2,498 Posts
My turn to measure this hub.
Here goes, one Shimano FH-M756 rear hub, black, 6-bolt, 36H.
Bought at CRC, January 2010.
Hub body is machined well and with good precision.
Measured with generic digital calipers and a steel crafts ruler.

Disk side spoke circle diameter 61.1 mm, spoke hole diameter 2.6 mm.
Drive side spoke circle diameter 61.1 mm, spoke hole diameter 2.6 mm.
Center do disk side flange, 31.5 mm.
Center do drive side flange, 18.5 mm.

I always advise my customers to bring me the rim and the hub, so that I measure them myself and calculate spoke lengths. But some choose to trust whatever they find online, in order to "save time" by purchasing rim, hub and spokes simultaneously. Most often this turns out bad, sometimes very bad. Recently I had to build a DT 240s/ZTR Olympic/CX-Ray wheelset where spokes were 4 mm loo long. It still goes strong, but I predict failure of (rear driveside) nipples within the next racing season.
 
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