Bicycle Mechanics - first wheel build is 'backwards'

I just built my first wheel and discovered that I have it backwards. It is a disc wheel (front) and the disc-side spokes are angled incorrectly for the torsion force, they will push instead of pulling tighter.

Do I need to start over, or can I just un-do one side somehow?

It's not a big deal if I have to start over...

(other than that, I'm actually pretty happy with it. It's a lot truer and rounder than I thought I'd be able to do myself, but I do need to work on the dishing)

You should have spokes leading and trailing on both sides, unless this is some cool new lacing pattern I've never seen before.

Maybe if you posted some pics of the setup it would help out.

If you mean that the right side leading spokes are heads in instead of heads out, or vice versa, it does not matter.

I just built my first wheel and discovered that I have it backwards. It is a disc wheel (front) and the disc-side spokes are angled incorrectly for the torsion force, they will push instead of pulling tighter.Other than building a radial wheel, there is ALWAYS a pulling and pushing spoke pair. The only difference would be if the pulling spoke came out on the outside or inside of the hub-flange. So yea, it doesn't matter.

So yea, it doesn't matter.

Actually, on a disc wheel yes it does. All the braking torque is directly at the hub, so there's a lot of force on a smaller swept area for braking forces

http://techdocs.shimano.com/media/techdocs/content/cycle/SI/Deore-LX/BR-M585/SI_8DB0C_001_EN_v1_m56577569830621527.PDF

Just an example, it shows the difference front/rear and left/right for disc lacing.

Oh no my wheels aren't laced Shimano approved! What will I do?

Its a minor difference.

At the end of the day, you are probably more likely to destroy the wheel getting a stick stuck in the spokes or you get your wheel jammed in some rocks and fold it.

Though not specifically for front wheels, here is a geeked out thread on lacing rear disc wheels. I would assume it would apply to the front wheels but the right side wouldn't matter too much because there is no drive torque being applied like a rear wheel

http://www.bikeforums.net/showthread.php?t=322461

Other than building a radial wheel, there is ALWAYS a pulling and pushing spoke pair. The only difference would be if the pulling spoke came out on the outside or inside of the hub-flange. So yea, it doesn't matter.

The pushing spokes come out the outside of the disc-side flange, the pulling spokes (obviously) come out the inside. I forgot to mention that it's a 3-cross pattern disc front wheel. I'll get some pix tomorrow, and thanks (almost) everyone for the replies.

Actually, on a disc wheel yes it does. All the braking torque is directly at the hub, so there's a lot of force on a smaller swept area for braking forces

http://techdocs.shimano.com/media/techdocs/content/cycle/SI/Deore-LX/BR-M585/SI_8DB0C_001_EN_v1_m56577569830621527.PDF

Just an example, it shows the difference front/rear and left/right for disc lacing.

Yep, that's what I'm talking about (although these are CK hubs, same thing). My front left is laced like Fig. 2 instead of Fig. 1.

you're going to be fine. ride your wheels, young jedi.


just make sure to tension properly

The pushing spokes come out the outside of the disc-side flange, the pulling spokes (obviously) come out the inside. I forgot to mention that it's a 3-cross pattern disc front wheel. I'll get some pix tomorrow, and thanks (almost) everyone for the replies.

You're fine. Ride on it to your heart's content.

I've had to lace wheels the "wrong" way many times- the offset drilling of the rim and the valve hole location forced the outside spokes to be facing backwards (so the chain would be pulled into the hub with crank tension rather than outward). But there's no evidence that this would make any difference- I try not to drop the chain from the inner cog no matter how my wheels are built. Front wheel- no problem.

As long as it's not radially laced, and I see it's not, you are ok.

I've done this one one of my first wheels and it was fine for miles and miles. I didn't realize it until my next wheel build and I took it off to look at as a sample to copy and I realized it was wrong.
you should be fine - just tension it up nice and true.

Yup. Just because some people read right to left doesn't make right right. Relax. It'll probably outlive Shimano.

You'll be fine. According to CK you've built your wheels correctly. They disagree with Shimano. And all the factory built CK wheels I've seen are laced like yours.

Chris King Instructions specify:
"The front ISO Disc should be laced 3-or-more-cross with the rotor (left) side pulling spokes (relative to braking direction) heads out/elbows in (when laced 3-cross). The final cross of the pulling spoke must be on the outside so that as braking force is applied, increased pulling spoke tension will pull the crossed spokes towards the center of the hub and away from the caliper. Lace the wheel symmetrically."

Here's a link to the CK Manual
http://chrisking.com/files/pdfs/ISOManual-11-07-A.pdf
The information I quoted is on the third page (CK refers to it as page 1).

I don't think there's a right way or a wrong way just preferences.

Thank you everyone for replying!

Just remember that "pulling" spokes under braking are aimed to the back of the bike.

Oh Crimminy! Can we get a picture? I'm sure it's fine.

Happy trails!

Just remember that "pulling" spokes under braking are aimed to the back of the bike.

I know that's true with rim brakes but wouldn't disc brakes, which apply the brakeing force at the hub, be different?

I know that's true with rim brakes but wouldn't disc brakes, which apply the brakeing force at the hub, be different?

On that note, a rim brake is also a disc brake, just with the disc further away from the hub...

On that note, a rim brake is also a disc brake, just with the disc further away from the hub...

I've heard that analogy before but I don't think that it's valid.

On a disc brake equipped bike the brakeing force is applied near the hub and all of the brakeing forces have to be transferred through the spokes to the rim and contact patch.

On a rim brake bike the brakeing effort connects the rim with the fork crown. A portion of the brakeing force is transferred through spokes but much goes around the rim to the contact patch.

Oh no my wheels aren't laced Shimano approved! What will I do?
Brace yourself as the sky's gonna fall. Mine is too.

I've heard that analogy before but I don't think that it's valid.

On a disc brake equipped bike the brakeing force is applied near the hub and all of the brakeing forces have to be transferred through the spokes to the rim and contact patch.

On a rim brake bike the brakeing effort connects the rim with the fork crown. A portion of the brakeing force is transferred through spokes but much goes around the rim to the contact patch.

I'm far from being up on my physics, but all I meant was that as far as lacing is concerned the braking forces are of the same nature/direction, albeit different in degree. At least I think that's correct...surely there's an engineer around?

I'm far from being up on my physics, but all I meant was that as far as lacing is concerned the braking forces are of the same nature/direction, albeit different in degree. At least I think that's correct...surely there's an engineer around?

This comes down to the same reason why you can use radial lacing on a front wheel with rim brakes, but not disc brakes. With rim brakes there is no rotational deflection of the hub in relation to the rim. How could there be, it's on bearings. However, with disc brakes there is rotational deflection of the hub relative to the rim. The braking force begins at the disc, travels through the hub flange and through the spoke tension to the rims.

If you used radial lacing with disc brakes, the amount of tension required in the spokes to stop the bike would either cause them to stretch the first time you used them or snap clean off. The spoke needs to act at an angle to the hub in order to pull the rim along. This is also the reason why the CK tech doc insists that their disc hubs be laced at least 3 cross.

Well, there's actually torsional stresses on rim brakes as well. Just that the reverse-torque generated through the moment-arm from the pads to the hub, closely matches the torque generated from the ground to the hub. So they cancel each other out and the force on the wheel is straight as if the bike was vertical facing downwards.

On a disc-brake, due to the difference in distance between the pads-to-hub versus ground-to-hub, you end up with a lot more torque from the disc. So if the distance from hub-to-ground is about 12" and you've got a 6" diameter disc (3" radius), you'll need 4x the reverse-torque from the disc to match the torque of the rim. This leads to the disc twisting the spokes more in one direction than the ground twisting the rim in the opposite direction.

On a disc-brake, due to the difference in distance between the pads-to-hub versus ground-to-hub, you end up with a lot more torque from the disc. So if the distance from hub-to-ground is about 12" and you've got a 6" diameter disc (3" radius), you'll need 4x the reverse-torque from the disc to match the torque of the rim. This leads to the disc twisting the spokes more in one direction than the ground twisting the rim in the opposite direction.

The distances don't matter -- the brake torque equals the ground torque no matter what the radii of the braking surface or wheel are. (the _force_ is 4x greater on a disk brake, but it's torque that matters here, not force). The significant difference is that with a rim brake, both brake and ground apply torque though the rim, whereas with a disk brake, brake applies torque through the hub and ground applies torque to the rim.

Buell made a motorcycle with a big disc brake for better heat dissipation, then they bolted the disc to the rim instead of the hub. Even though the tire is still much taller than the disc, there's practically no braking torque on the hub, so they can use nearly radial spoking to save weight:

http://www.thebikerzone.com/road_tests/images/buell/buell311203_22708.jpg

OK, here's a photo (finally). This http://img27.imageshack.us/img27/2710/dscn8303small.jpg is the front hub left side so rotation is counter-clockwise, the spokes in question are the ones that come out of the flange (heads-in) and are oriented clockwise. This means that any torsion will push on the spokes instead of pulling them tight.

Safe to ride or do over? If do-over, undo all of the spokes or can I just re-do all of the spokes on the left side?

Ken, every time spokes have torsion half are "pushing" and half are "pulling." You are good to go:)

Ken, every time spokes have torsion half are "pushing" and half are "pulling." You are good to go:)
I'm trying to develop a set that has ALL the spokes pulling so then I can use 1/2 the effort for the same speed or go 2x as fast for the same effort (take yer pic). I expect to have them done in exactly fifteen days :roflmao2:

I'm trying to develop a set that has ALL the spokes pulling so then I can use 1/2 the effort for the same speed or go 2x as fast for the same effort (take yer pic). I expect to have them done in exactly fifteen days :roflmao2:

http://sheldonbrown.com/power_wheel.html

http://sheldonbrown.com/power_wheel.html
Dohh! I see he's also done the mono-spoke wheel too. I'd better find something else for my thesis. :innocent:

If do-over, undo all of the spokes or can I just re-do all of the spokes on the left side?

It looks like you've laced both sides like CK recommends and the opposite of how Shimano recommends. :backpedal: As others here have written, Shimano is not the be all end all of recommendations - especially as these are not Shimano hubs!

:geek: The way the wheel is now, when braking, tension will increase on the spokes to the inside (ie heads out) of both flanges. Tension will decrease on the outside (heads in) spokes. The tension changes will cause the inside spokes to win in the tug of war between the inside and outside spokes at the spoke crossing. Because the inside spokes actually go to the outside of the crossing, this will cause the lacing to flare inwards, away from the brake hardware.

If you do decide to redo one side, then you should redo both sides.

Q for the experts: How many different manufacturer recommenations are there for lacing disc brake wheels? There's the Shimano recommendation linked above which mentions different lacing for front and rear wheels. The Chris King recommendation linked above only mentions front wheels.

I just wanted to thank everyone for taking the time to respond. The wheel is on the bike in the car and I'll be riding it at lunch!