Triplet lacing still relevant with disc brakes?

[rice rocket]

Either I've had real good results with triplet lacing or I'm excessively overbuilding my wheels, but either way all my road rear wheels for the past 10 years have been on fairly light 24H rims and have survived plenty of crunching on pot holes.

That said, I'm building a gravel bike and assuming radial lacing isn't wise on the NDS side, I'm not sure how to build the rear.

Am I falsely attributing the wheel strength to equal spoke tension? I know it's not the builder because I'm a hack...

[oldpotatoe]

Originally Posted by rice rocket

Either I've had real good results with triplet lacing or I'm excessively overbuilding my wheels, but either way all my road rear wheels for the past 10 years have been on fairly light 24H rims and have survived plenty of crunching on pot holes.

That said, I'm building a gravel bike and assuming radial lacing isn't wise on the NDS side, I'm not sure how to build the rear.

Am I falsely attributing the wheel strength to equal spoke tension? I know it's not the builder because I'm a hack...

Heavy enough rim and not uber-thin spokes..24H will 'work'. ..And altho it looks cool, not sure it does anything when compared to radial non drive side, normal crossed drive side(rear). Tension is higher, NDS but not really equal.

Yup, radial lacing disc side is not a great idea.

BUT, do a 24h triplet, disc brake..and report back.

[hollowgram5]

Is it even advisable to lace a 24h hub 3x? I have always understood maximum crossing=spoke count/9 and the round down. 24/9=2.6666 => max number of crosses on a 24h hub would be 2.

I could be completely wrong, but that's what I've always followed.

[oldpotatoe]

Originally Posted by hollowgram5

Is it even advisable to lace a 24h hub 3x? I have always understood maximum crossing=spoke count/9 and the round down. 24/9=2.6666 => max number of crosses on a 24h hub would be 2.

I could be completely wrong, but that's what I've always followed.

It's possible to lace 24/3 cross but the spoke, as it leaves the hub, 'may' overlap the head of an adjacent spoke. Pretty big bend, as it goes over the hub flange but yup..I use 24/2 cross, 28/3cross..

[Mark McM]

Originally Posted by rice rocket

Either I've had real good results with triplet lacing or I'm excessively overbuilding my wheels, but either way all my road rear wheels for the past 10 years have been on fairly light 24H rims and have survived plenty of crunching on pot holes.

That said, I'm building a gravel bike and assuming radial lacing isn't wise on the NDS side, I'm not sure how to build the rear.

Am I falsely attributing the wheel strength to equal spoke tension? I know it's not the builder because I'm a hack...

Yes, triplet lacing is still quite relevant with disc brakes, and for the same reasons as it is with rim brakes. Several wheel manufacturers use triplet lacing for their disc brake wheels, including Campagnolo and Fulcrum.

As noted, the spokes on the left (brake side) should be crossed. For 24 spoke triplet lacing, you've got a choice of 1-cross or 2-cross on the left side. the 8 spokes on the left are the same as on a symmetrically laced wheel with 16 spokes, so you can use most spoke calculators to get the spoke length. With 1-cross, the spokes angle will be 45 degrees, and with 2 cross the spoke angle will be 90 degrees (tangential), both of which should work with standard flanges. I've used both 1-cross and 2-cross, and both worked out fine.

[Mark McM]

Originally Posted by hollowgram5

Is it even advisable to lace a 24h hub 3x? I have always understood maximum crossing=spoke count/9 and the round down. 24/9=2.6666 => max number of crosses on a 24h hub would be 2.

I could be completely wrong, but that's what I've always followed.

The number of crossings that work depends not on the total number of spokes, but on the number of spokes on each side of the wheel. A 24 spoke wheel with triplet lacing has 16 spokes on the right side (much like a 32 spoke symmetrically laced wheel), and 8 spokes on the left side (much like a 16 spoke symmetrically laced wheel). Like other wheels with 16 spokes on one side, you can do 2 cross or 3 cross on the 16 spoke side of a triplet wheel. On the 8 spoke side, only 1 cross or 2 cross are possible.

[rice rocket]

Thanks all, that all makes sense, not sure why I didn't think you could do anything other than radial on the NDS.

Now to find a hub...DT only does 28h rear now it seems. XTR is still available in 32h, but I prefer cartridge bearings.

[robt57]

I am big, so front brake get some extra work to be done.

I laced a 28h cx75 front 2x, went 400' down my street turned back and relaced/re-spoked disc side 3x.

Take what you will from that.

I do on disc wheels use 14/15 leading disc side with 14/17 trailing and right side if 28+h. Likewise heavier rear drive trailing and disc leading, lighter on the rest. Just my fiddling approach from building boredom perhaps...

I might sanction triplet front disc, even try it sometime. Disc side 3x for my girth though.

I do have 24h disc wheels, just not self built... 2X, but aot stiffer and carbon rims than what i built previously, 26mm max height.

This is as much spoke play for my weight i found does not effect braking wind up/back.

Now i was 235 when i did these builds. Being closer to 200(ish) it may change the dynamic a bit.

[NHAero]

For a given rider, which imposes higher torque on the wheel, the disc or the cassette?

Originally Posted by Mark McM

Yes, triplet lacing is still quite relevant with disc brakes, and for the same reasons as it is with rim brakes. Several wheel manufacturers use triplet lacing for their disc brake wheels, including Campagnolo and Fulcrum.

As noted, the spokes on the left (brake side) should be crossed. For 24 spoke triplet lacing, you've got a choice of 1-cross or 2-cross on the left side. the 8 spokes on the left are the same as on a symmetrically laced wheel with 16 spokes, so you can use most spoke calculators to get the spoke length. With 1-cross, the spokes angle will be 45 degrees, and with 2 cross the spoke angle will be 90 degrees (tangential), both of which should work with standard flanges. I've used both 1-cross and 2-cross, and both worked out fine.

[Mark McM]

Originally Posted by robt57

I am big, so front brake get some extra work to be done.

I laced a 28h cx75 front 2x, went 400' down my street turned back and relaced/re-spoked disc side 3x.

Take what you will from that.

I don't know what to take from that. Wheels with any number of crossings have very high torsional stiffness, so differences in the numbers of crossings shouldn't be discernible. On the other hand, wheels have relatively low lateral stiffness, and increasing the number of crosses actually decreases lateral stiffness.

Originally Posted by robt57

I do on disc wheels use 14/15 leading disc side with 14/17 trailing and right side if 28+h. Likewise heavier rear drive trailing and disc leading, lighter on the rest. Just my fiddling approach from building boredom perhaps...

I'm not sure what the point of this is. With leading and trailing spokes of the same gauge, torsion loads are distributed equally between all spokes (the leading spokes see the same amount of load decreases as the trailing spokes see load increases). Using thicker trailing spokes will result in a higher percentage of the load being taken by the trailing spokes. But since all the spokes have the same thicknesses at the elbows and threads (the places where spokes fatigue and break), this can actually decrease the fatigue life of the trailing spokes.

[Mark McM]

Originally Posted by NHAero

For a given rider, which imposes higher torque on the wheel, the disc or the cassette?

This depends on the gear ratios used. Of note here is that because the CG of a bicycle is very high relative to the wheelbase, there is substantial forward weight shift during braking. This means that it doesn't take too much brake force before so much weight is shifted off the rear wheel that the tire looses traction, limiting the amount of braking force that can be applied to the rear wheel. Typically, a rear wheel can't apply a braking force of more than about 1/4 - 1/3 g.

On the other side of the question, some bikes have gears so low that the front wheel can lift off the ground under pedalling torque. This require an acceleration force of about 1/3-1/2 g. So bikes with very low gears can generate more drive torque than rear brake torque.

A few other pertinent comments: Even with high drive torque, half radial wheels work just fine, which shows that wheels can be reliable with only half the spokes subject to torque loads. Also consider that the highest loads experienced by the spokes are from vertical weight bearing forces, and not drive/brake torques. The reason for this is that vertical weight bearing loads are experienced only be a few spokes near the ground contact point, whereas the torque loads are nearly equally distributed among all the crossed spokes. Finally note that due to forward weight shift, as brake torque on the rear wheel increases, vertical weight bearing loads on the wheel decrease, so under maximum braking the rear wheel spokes are under less total combined load then when simply coasting.

Edit:
Shimano and Campagnolo/Fulcrum also appear to think that triplet lacing is even more relevant to disc brakes, because both companies use triplet lacing not only on rear wheels, but also on front disc brake wheels (after all, front disc brake wheels are also dished). Both companies use double the number of spokes on the cassette side of rear wheels, and on the disc rotor side of front wheels.

And to give an idea on how unimportant rear disc brakes are for spoke loading, take a look at the new Shimano 12spd WH-R9270-C60 wheels. these disc brake wheels use 24 spokes in a triplet pattern (16 right/8 left) on the rear wheel. Apparently they realize that the rear disc brake produces little torque load on the wheel, as they don't even bother crossing the spokes on the disc side (left):

https://bike.shimano.com/en-US/produ...0-HR-TL-R.html

Fulcrum/Campagnolo also has several disc brake wheels with triplet lacing and which the left spokes are not crossed.

[oldpotatoe]

Originally Posted by robt57

I am big, so front brake get some extra work to be done.

I laced a 28h cx75 front 2x, went 400' down my street turned back and relaced/re-spoked disc side 3x.

Take what you will from that.

I do on disc wheels use 14/15 leading disc side with 14/17 trailing and right side if 28+h. Likewise heavier rear drive trailing and disc leading, lighter on the rest. Just my fiddling approach from building boredom perhaps...

I might sanction triplet front disc, even try it sometime. Disc side 3x for my girth though.

I do have 24h disc wheels, just not self built... 2X, but aot stiffer and carbon rims than what i built previously, 26mm max height.

This is as much spoke play for my weight i found does not effect braking wind up/back.

Now i was 235 when i did these builds. Being closer to 200(ish) it may change the dynamic a bit.

Sure, why not but I generally use 14/15 all around and 3 cross unless 24h. If the gent wants a bit 'lighter'...thinner spokes on non disc side front is about all.
For some builds I have even used Sapim Force or Strong spokes..
https://www.sapim.be/spokes/butted/force
https://www.sapim.be/spokes/butted/strong

BUT, I've found that anything but just 14/15/14 butted spokes make very little difference in wheel performance. Weight savings is teeny. I use the Burley spokes for big guys and a not heavy rim and maybe too few spokes but don't like to go down the '3 strikes and you are out' path.
-Thin spokes
-light rim
-too few spokes

But, admittedly, I am way conservative when it comes to wheel builds.

'French Bridge Builder' comes to mind.....and wheel building rep.

But, for your wheels, why not. I even built a crow's foot once and even a twisty spoke wheel..once...for myself..

[binouye]

Thanks for that post Mark (and others). I'm building a wheel today, but 32 3x because I'm re-using some hubs and that is what the previous build was (I've read multiple places that hubs should always be re-laced with the same pattern, but haven't ever tried anything else so can't compare effects on flange longevity). I've idly wondered about drive vs braking vs pothole forces before, so its nice to have somebody else provide rough figures.