Experiment #1: 20h disc front wheel

[Gummee]

Just 'finished' a rebuild of a front wheel. I think I need 2mm longer nipples for looks. The threads are at the bottom of the nipples inside the rim

Its an experiment. 'They say' that you can't run a 20h disc hub up front. We'll see. I'll either keep this as is, re-do the nipples, or sell it to someone smaller than me.

As it is: 650g Sapim butted spokes (14/15), black brass nipples, Bitex CX hub. The rear is up next. I'm debating ordering some longer nipples 'just because.'

M

I can't seem to get the 2nd pic to upload. Someone wanna try it for me?

[weisan]

When they first move to 32h, the 36h people was like :no:
And then when they move to 28h, the 32h people was like :no:
And then when they move to 24h, the 28h people was like :no:
And then when they move to 20h, the 24h people was like :no:
And then when they move to 16h, all hell breaks loose. :D

I have an expression for this phenomenon, it's called Generational Gap.

[cachagua]

https://cdn6.bigcommerce.com/s-mrkn324fu0/products/1378/images/3086/uw20sil__87475.1470422078.500.750.jpg?c=2

[zap]

Regarding "they say you can't" Rolf has been making them for years..........20h front disc wheel for singles and tandems.

[oldpotatoe]

When they first move to 32h, the 36h people was like :no:
And then when they move to 28h, the 32h people was like :no:
And then when they move to 24h, the 28h people was like :no:
And then when they move to 20h, the 24h people was like :no:
And then when they move to 16h, all hell breaks loose. :D

I have an expression for this phenomenon, it's called Generational Gap.

Build a couple of low spoke count DISC brake wheels...and then see how they do. I guess the generational gap is the gap between experience and comments on the interweb. That's my 'expression'...

IMHO, of course, 'pal'..

[93KgBike]

When they first move to 32h, the 36h people was like :no:
And then when they move to 28h, the 32h people was like :no:
And then when they move to 24h, the 28h people was like :no:
And then when they move to 20h, the 24h people was like :no:
And then when they move to 16h, all hell breaks loose. :D

I have an expression for this phenomenon, it's called Generational Gap.

That's awesome!

[GonaSovereign]

Data point: Boyd had to replace some hubs under warranty in a set of deep carbon wheels I owned. I asked them to replace the hubs with disc versions, but they wouldn't do it b/c the wheel had too few (20) spokes. It was annoying to me, but I respected that they know a lot more about wheels than I do.

[Pastashop]

I’m sure you could get away with it for some number of miles and uses... What I don’t fully understand is what compelling gain there would be / reason for running a 20h wheel... (But then again, neither do I understand the reason for running a radially spoked wheel instead of 3-cross, NDS tension mitigation excluded.)

[hollowgram5]

When they first move to 32h, the 36h people was like :no:
And then when they move to 28h, the 32h people was like :no:
And then when they move to 24h, the 28h people was like :no:
And then when they move to 20h, the 24h people was like :no:
And then when they move to 16h, all hell breaks loose. :D

I have an expression for this phenomenon, it's called Generational Gap.

And then Shimano and Campy did 12h front wheels and the world started burning...

[Gummee]

I’m sure you could get away with it for some number of miles and uses... What I don’t fully understand is what compelling gain there would be / reason for running a 20h wheel... (But then again, neither do I understand the reason for running a radially spoked wheel instead of 3-cross, NDS tension mitigation excluded.)

I had an 'extra' wheelset that didn't brake well, so I figured an experiment was in order

Next CX season, I'll be rockin and rollin the disc tubulars

M

[ergott]

The threads are at the bottom of the nipples inside the rim

Where are you with respect to this chart?

http://www.wheelfanatyk.com/wp-content/uploads/2010/07/nipple-thread.jpg

[CiclistiCliff]

I don't like where this is going.....

Low spoke count, spoke/nipple interface not ideal and disc brake. :banana:

[Mark McM]

So, take a look spoke loading from the disc brake:

Torque loads (as from pedaling or hub brakes) are distributed nearly equally among all the spokes. So with a large number of spokes, the stresses from torque loads will be much smaller than the stresses from radial (weight bearing) loads, which are distributed over a smaller number of spokes. But with a smaller number of spokes, stresses on individual spokes increase. But there are several mitigating factors at work on this particular wheel:

1) Stresses from torques are inversely proportional to flange size. Since rotor-side flange on this wheel is oversized, that will help reduce spoke stress.

2) Spoke stresses from torque also decrease with spoke angle. The rotor-side spokes on this wheel are laced in a 2x pattern which results in a 72 degree spoke angle, which isn't far from tangential (and also greater than the 67.5 degree spoke angle in the popular 32 spokes 3x pattern).

Personally, I wouldn't have a problem with this 20 spoke disc brake wheel. Spoke stresses from disc brakes are small and infrequent enough to begin with, and this particular wheel doesn't increase them by much.

[Gummee]

So, take a look spoke loading from the disc brake:

Torque loads (as from pedaling or hub brakes) are distributed nearly equally among all the spokes. So with a large number of spokes, the stresses from torque loads will be much smaller than the stresses from radial (weight bearing) loads, which are distributed over a smaller number of spokes. But with a smaller number of spokes, stresses on individual spokes increase. But there are several mitigating factors at work on this particular wheel:

1) Stresses from torques are inversely proportional to flange size. Since rotor-side flange on this wheel is oversized, that will help reduce spoke stress.

2) Spoke stresses from torque also decrease with spoke angle. The rotor-side spokes on this wheel are laced in a 2x pattern which results in a 72 degree spoke angle, which isn't far from tangential (and also greater than the 67.5 degree spoke angle in the popular 32 spokes 3x pattern).

Personally, I wouldn't have a problem with this 20 spoke disc brake wheel. Spoke stresses from disc brakes are small and infrequent enough to begin with, and this particular wheel doesn't increase them by much.
I knew 2x was minimum and I got that. This is a race wheel. Or at minimum a training wheel that will strictly be for CX. The wheelset is likely to have this year's race tires glued on as I buy another pair of new new race tires for next season

I don't plan on this wheel seeing a whole lot of mileage.

If it starts to be a problem child, I'll sell it to someone small.

The rear is 24h. Should be Ok.

AFA the nipples, from the outside, they look like they're OK (the good pic)

M

[Gummee]

Let's try this

[Gummee]

The rear is trued and tensioned.

It weighs 860g

Gonna be a lightweight backup wheelset for next fall

M