# Hub Center to Flange Center???

Discussion in 'Cycling Equipment' started by !Jones, Aug 25, 2007.

1. ### !Jones Guest

I'm playing with a spoke calculator. Why do we need "Hub Center to
Flange Center"? What does it give me that I use in the wheel? If the
wheel is symmetric, then what difference does it make?

I'm looking at http://www.bikeschool.com/spokes/index.cgi

I also note that the distance between the flanges isn't an input. Can
I calculate the width of the wheel (meaning the flanges) from that?

I don't think I'm measuring it right.

Jones

#1
Tags:

2. ### JeffWills Guest

On Aug 25, 9:58 am, !Jones <p...@off.com> wrote:
> I'm playing with a spoke calculator. Why do we need "Hub Center to
> Flange Center"? What does it give me that I use in the wheel? If the
> wheel is symmetric, then what difference does it make?
>
> I'm looking athttp://www.bikeschool.com/spokes/index.cgi
>
> I also note that the distance between the flanges isn't an input. Can
> I calculate the width of the wheel (meaning the flanges) from that?
>
> I don't think I'm measuring it right.
>
> Jones

Trigonometry, my dear boy. The distance from hub center to the flange
gives you the base of the triangle where the vertical distance from
the hub to the rim is the height and the spoke forms the hypotenuse.
Without knowing this measurement, you can't correctly determine the
spoke length.

Many hubs (most rear and some front) are not symmetrical right-to-
left. You need to determine the distance from center to flange on each
side to get the lengths exactly right. It can make a difference-
highly dished rear wheels can have a difference of 2mm from left to
right.

Try using Spocalc: http://sheldonbrown.com/rinard/spocalc.htm . The
spreadsheet includes data on many common rims and hubs, and allows
independant data entry for items not included. It's never let me down.

Jeff

#2
3. ### !Jones Guest

On Sat, 25 Aug 2007 11:19:51 -0700, in rec.bicycles.tech JeffWills
<jwills@pacifier.com> wrote:

>Trigonometry, my dear boy. The distance from hub center to the flange
>gives you the base of the triangle where the vertical distance from
>the hub to the rim is the height and the spoke forms the hypotenuse.
>Without knowing this measurement, you can't correctly determine the
>spoke length.
>
>Many hubs (most rear and some front) are not symmetrical right-to-
>left. You need to determine the distance from center to flange on each
>side to get the lengths exactly right. It can make a difference-
>highly dished rear wheels can have a difference of 2mm from left to
>right.
>
>Try using Spocalc: http://sheldonbrown.com/rinard/spocalc.htm . The
>spreadsheet includes data on many common rims and hubs, and allows
>independant data entry for items not included. It's never let me down.
>
>Jeff

Ya know, my dear boy, what we need are four points:

>Trigonometry, my dear boy. The distance from hub center to the flange
>gives you the base of the triangle...

A distance alone does not give you the base of a triangle... if you
knew trig, dear boy, then you'd already know that; if all you have is
distance, you're not in Euclidean space yet, so it's nonsensical to
start talking about triangles until you unequivocally fix three
noncolinear points. (Actually, I think you're fixing two and taking a
perpendicular delta, but that's not what you wrote.)

address me as "my dear boy" until you're sure that you know your
subject... I'm pretty well up to date on my trig... "dear boy".

Jones

#3
4. ### !Jones Guest

On Sat, 25 Aug 2007 13:31:13 -0700, in someplace JeffWills
<jwills@pacifier.com> wrote:

>OK- *you* explain to *me* how you're going to calculate spoke length
>without knowing how far the flange is from the center of the hub.

That's what I was asking. Is that what it is? Would zero mean that
you only had one flange? (That would be an unstable wheel, naught?)
Would 0.5" mean that the centers were an inch apart?

Jones

#4
5. ### Gary Young Guest

On Sat, 25 Aug 2007 12:58:08 -0500, !Jones wrote:

> I'm playing with a spoke calculator. Why do we need "Hub Center to
> Flange Center"? What does it give me that I use in the wheel? If the
> wheel is symmetric, then what difference does it make?
>
> I'm looking at http://www.bikeschool.com/spokes/index.cgi
>
> I also note that the distance between the flanges isn't an input.

It is, in a sense. Lefthand Hub-Center-to-Flange-Center distance +
righthand Hub-Center-to-Flange-Center distance = distance between flanges.
What may be confusing you is that this particularly calculator only does
one side of a wheel at a time.

> Can
> I calculate the width of the wheel (meaning the flanges) from that?
>
> I don't think I'm measuring it right.
>
> Jones

http://www.damonrinard.com/spocalc.htm

Scroll down to "How to Measure Hub and Rim Dimensions."

"Hub Center to Flange Center" is the same thing as WL and WR on the
diagram. (That's W-subscript-L, W-subscript-R.)

#5
6. ### !Jones Guest

On Sat, 25 Aug 2007 15:40:57 -0500, in rec.bicycles.tech Gary Young
<garyyoung3@gmail.com> wrote:

>It is, in a sense. Lefthand Hub-Center-to-Flange-Center distance +
>righthand Hub-Center-to-Flange-Center distance = distance between flanges.
>What may be confusing you is that this particularly calculator only does
>one side of a wheel at a time.

Oh... well, that's a "light bulb moment"!

Got it!

Thanx!

Jones

#6
7. ### JeffWills Guest

On Aug 25, 1:24 pm, !Jones <p...@off.com> wrote:
> On Sat, 25 Aug 2007 15:40:57 -0500, in rec.bicycles.tech Gary Young
>
> <garyyou...@gmail.com> wrote:
> >What may be confusing you is that this particularly calculator only does
> >one side of a wheel at a time.

>
> Oh... well, that's a "light bulb moment"!
>

Ah-ha! My own light bulb moment: you were using a crappy spoke
calculator. Spocalc is so much nicer. I will now retire to my couch
and cats.

Jeff

#7
8. ### Qui si parla Campagnolo-www.vecchios.com Guest

On Aug 25, 11:58 am, !Jones <p...@off.com> wrote:
> I'm playing with a spoke calculator. Why do we need "Hub Center to
> Flange Center"? What does it give me that I use in the wheel? If the
> wheel is symmetric, then what difference does it make?
>
> I'm looking athttp://www.bikeschool.com/spokes/index.cgi
>
> I also note that the distance between the flanges isn't an input. Can
> I calculate the width of the wheel (meaning the flanges) from that?
>
> I don't think I'm measuring it right.
>
> Jones

When measuring hub dimensions you need 2..flange diameter..center hole
to center hole across the hub flange and center of the hub to flange
dimension on each side and yes, if the hub is symmetric, the spoke
lengths will be the same on each side.

#8