Re: Radial lacing on drive side R Wheels

United Bicycle Institute

TECHNICAL FORUM

UBI Main Page

UBI Courses and Schedules

[ Post a Reply ] [ UBI Technical Forum ] [ FAQ ]

Subject: Re: Radial lacing on drive side R Wheels
Posted by: Al on August 10, 2006 at 06:42:04:
In Reply to: Re: Radial lacing on drive side R Wheels posted by Andy on August 09, 2006 at 15:17:47:

Message:
>>>I've been having this debate in our shop about radial lacing on drive side of rear wheels, as some shimano wheels have become as well as some others. Is the greater torsional load in the pulling spokes (non drive in this case)or in the drive side of the wheel. Where is the greatest load on a 3x by 3x rear wheel then, if radial lacing does work with a strong enough hub to transfer the load to the non-drive side? Anybody have any crazy thoughts on wheel physics. To me radial lacing on the drive side just doesn't do it.
>>I think that the higher torsional loads on a radial drive side wheel are going to be on the pulling spokes non drive. Radial lacing has no capability to prevent torsional movement. The key word here is radial, as soon as that spoke leaves a line that radiates directly out from the center of the hub they can now start to resist tortional movement because it can create torque. The question then becomes does a biker create anough force to rotate the hub to a degree that the drive side spokes can create a greater torque than the non-drive spokes to resist rotation. This can only be answered if the tortional stiffness of the hub is known. But if you do some simple trig you will find that if the hub rotates so that the spoke is at an angle of .1deg. with the imaginary center line that goes from the rim to the center of the hub and your spoke is at 1100n then the torque that is created per spoke is only about 1.92n were as a three cross on the non-drive side will have a spoke angle closer to 5 deg. which with an 800n spoke will create close to 68n of force. therefore the non-drive will take the majority of the tortional load assuming the hub is stiff enough.
>>Now if we look at a wheel that is 3x drive and non-drive the majority of the tortional load will be taken up by the drive side. This is because the drive side has greater tension and since the drive and non-drive sides have the same spoke angle the torque produced by a drive side spoke is greater. One other thing to consider is the tortional stiffness of the hub body. I don't really know how to explain this except that as the drive flange rotates the hub body tries to rotate with it the non-drive spokes are the only thing stoping the body from rotating. Therefore if a hub body is stiffer it will be able to exert a greater force on the non-drive spokes per degree of rotation thus allowing those spokes to share some of the load being exerted by the rider. But since the non-drive spokes are at lower tension and because there will always be some twisting in the hub body the non-drive spokes will handle less torsional load than the drive side.
>>I hope this makes some sense. If it doesn't, I will be more than happy to try and clarify anything that doesn't make sense.
>I appreciate your words of knowledge. It makes some sense. So how do you know if a hub is stiff enough? Is it fair to say, most quality hubs today can handle this? I'm a smart guy with a science background but this is still confusing some. Fun to figure out though. This means there is no real problem with radially lace drive-side wheel (again assuming a good hub body), that there is no lost torque transfering the load to the non-drive side, even though they are at a lower tension? It still seems that even the fact that non-drive crossed spokes are at a lower tension would adversely affect wheel performance. Any further clarification would be appreciated. Is a radial/3x wheel okay in your book then?
If you scroll down to 04/04/06, you will see that "we" discussed this in some length ...
The wheels whose radial spoking is on the DRIVE side (MAVIC & SHIMANO) have hubs which have received a token amount of engineering which accidentally imparts a minimal (vs. negligible) amount of torque transfer -- that is, the nipple on the drive side of those hubs are held in place whereas if you were to radially lace EITHER the drive OR non-drive side of ANY standard rear hub then you are forcing the side which has crossed spokes to do ALL of the torque transfer. That is, for all practical purposes, there is ZERO TORQUE TRANSFER on a spoke that is radially laced on a standard hub; and, I would suggest that to radially lace a drive-side spoke on a standard hub invites eventual spoke breakage of those spokes because the will be in constant abrasion at the J-bend as they wiggle back-and-forth in the spoke hole. Granted, it will be a small amount of motion, but it will be repeated thousands of times ... hundreds of thousands of times.
While it is periodically in vogue to lace radially on a rear wheel -- the non-drive side in the past -- I personally would recommend against it.
If you are contemplating radially lacing on a rear wheel for cosmetic purposes, then it had better be a show bike that isn't being ridden BECAUSE you are thereby asking the active spokes to carry all the transfer ... would you otherwise lace up a 14 spoke rear wheel? A 16 spoke rear wheel? An 18 spoke rear wheel?
Maybe, yes. Maybe, no.
If you are choosing radially lacing it to save weight, then buy some double-butted or titanium spokes, instead, AND lace them x1 or x2.
If you want to build a strong & reliable wheel, then lace the drive side x3 and the non-drive side x2 -- that lacing has been "calculated" by someone to result in close-to-equal tension on both sides of the wheel ...
FWIW. It has been observed that most professional racing teams train on 32x3 wheels ... of course, they race on wheels which the sponsor is trying to sell.

Post a Follow Up To This Message

Follow Up Message:

>>>>I've been having this debate in our shop about radial lacing on drive side of rear wheels, as some shimano wheels have become as well as some others.  Is the greater torsional load in the pulling spokes (non drive in this case)or in the drive side of the wheel.  Where is the greatest load on a 3x by 3x rear wheel then, if radial lacing does work with a strong enough hub to transfer the load to the non-drive side?  Anybody have any crazy thoughts on wheel physics.  To me radial lacing on the drive side just doesn't do it.

>>>I think that the higher torsional loads on a radial drive side wheel are going to be on the pulling spokes non drive. Radial lacing has no capability to prevent torsional movement. The key word here is radial, as soon as that spoke leaves a line that radiates directly out from the center of the hub they can now start to resist tortional movement because it can create torque.  The question then becomes does a biker create anough force to rotate the hub to a degree that the drive side spokes can create a greater torque than the non-drive spokes to resist rotation.  This can only be answered if the tortional stiffness of the hub is known.  But if you do some simple trig you will find that if the hub rotates so that the spoke is at an angle of .1deg. with the imaginary center line that goes from the rim to the center of the hub and your spoke is at 1100n then the torque that is created per spoke is only about 1.92n were as a three cross on the non-drive side will have a spoke angle closer to 5 deg. which with an 800n spoke will create close to 68n of force. therefore the non-drive will take the majority of the tortional load assuming the hub is stiff enough. 
>>>Now if we look at a wheel that is 3x drive and non-drive the majority of the tortional load will be taken up by the drive side.  This is because the drive side has greater tension and since the drive and non-drive sides have the same spoke angle the torque produced by a drive side spoke is greater.  One other thing to consider is the tortional stiffness of the hub body. I don't really know how to explain this except that as the drive flange rotates the hub body tries to rotate with it the non-drive spokes are the only thing stoping the body from rotating.  Therefore if a hub body is stiffer it will be able to exert a greater force on the non-drive spokes per degree of rotation thus allowing those spokes to share some of the load being exerted by the rider.  But since the non-drive spokes are at lower tension and because there will always be some twisting in the hub body the non-drive spokes will handle less torsional load than the drive side.  
>>>I hope this makes some sense.  If it doesn't, I will be more than happy to try and clarify anything that doesn't make sense.

>>I appreciate your words of knowledge.  It makes some sense.  So how do you know if a hub is stiff enough?  Is it fair to say, most quality hubs today can handle this?  I'm a smart guy with a science background but this is still confusing some.  Fun to figure out though.  This means there is no real problem with radially lace drive-side wheel (again assuming a good hub body), that there is no lost torque transfering the load to the non-drive side, even though they are at a lower tension?  It still seems that even the fact that non-drive crossed spokes are at a lower tension would adversely affect wheel performance.  Any further clarification would be appreciated.  Is a radial/3x wheel okay in your book then?

>If you scroll down to 04/04/06, you will see that "we" discussed this in some length ...

>The wheels whose radial spoking is on the DRIVE side (MAVIC & SHIMANO) have hubs which have received a token amount of engineering which accidentally imparts a minimal (vs. negligible) amount of torque transfer -- that is, the nipple on the drive side of those hubs are held in place whereas if you were to radially lace EITHER the drive OR non-drive side of ANY standard rear hub then you are forcing the side which has crossed spokes to do ALL of the torque transfer.  That is, for all practical purposes, there is ZERO TORQUE TRANSFER on a spoke that is radially laced on a standard hub; and, I would suggest that to radially lace a drive-side spoke on a standard hub invites eventual spoke breakage of those spokes because the will be in constant abrasion at the J-bend as they wiggle back-and-forth in the spoke hole.  Granted, it will be a small amount of motion, but it will be repeated thousands of times ... hundreds of thousands of times.

>While it is periodically in vogue to lace radially on a rear wheel -- the non-drive side in the past -- I personally would recommend against it.

>If you are contemplating radially lacing on a rear wheel for cosmetic purposes, then it had better be a show bike that isn't being ridden BECAUSE you are thereby asking the active spokes to carry all the transfer ... would you otherwise lace up a 14 spoke rear wheel?  A 16 spoke rear wheel?  An 18 spoke rear wheel?

>Maybe, yes.  Maybe, no.

>If you are choosing radially lacing it to save weight, then buy some double-butted or titanium spokes, instead, AND lace them x1 or x2.

>If you want to build a strong & reliable wheel, then lace the drive side x3 and the non-drive side x2 -- that lacing has been "calculated" by someone to result in close-to-equal tension on both sides of the wheel ...

>FWIW.  It has been observed that most professional racing teams train on 32x3 wheels ... of course, they race on wheels which the sponsor is trying to sell.

[ UBI Technical Forum ] [ FAQ ]