Lacing triple cross 28h

[cribbit]

I've done 32h a few times. I normally do four at a time and it's pretty straightforward.

How do I do 28h triple cross? My brain isn't getting it and I'm struggling to find videos - I'm probably bad at searching.

[tctyres]

Originally Posted by cribbit

I've done 32h a few times. I normally do four at a time and it's pretty straightforward.

How do I do 28h triple cross? My brain isn't getting it and I'm struggling to find videos - I'm probably bad at searching.

Same way. 7 groups of four instead of 8.

Put down the spokes. Eat something and come back to it in an hour or tomorrow. It will be obvious.

[11.4]

Except that for a 28 spoke wheel you're somewhat better off doing it 2-cross rather than 3.

[cribbit]

Originally Posted by tctyres

Same way. 7 groups of four instead of 8.

Put down the spokes. Eat something and come back to it in an hour or tomorrow. It will be obvious.

I was doing 4 on the same side.

Originally Posted by 11.4

Except that for a 28 spoke wheel you're somewhat better off doing it 2-cross rather than 3.

I've been trying to look into this and finding no real information. Do you have a source / info on impact?

[ultraman6970]

28 triple cross?? depends a lot of the hub IMO because at 3x the spokes start overlapping a little bit more than what you really want.

[dddd]

I built up my Pacenti Brevit 28h rims onto these 7700 hubs the other night and was able to compare using 2x in front with 3x in back.

The 3x looks far better to me in terms of minimizing any cyclic changes in spoke tension due to drive torque on the rear hub.





FWIW, I was able to just get to 100kg driveside tension before any further tension increase tended to force the rear rim well out of true.
These are vintage-style rims that nevertheless "hit the numbers" in terms of credibly vintage profile, prodigious width and light weight.
As such, they are not going to build into as high-performing a structure as a rim with a modern profile, especially on an 8s, 130mm rear hub.
Very nice rims though, just what people have been asking for! Build weight was 1753g using 14/15G spokes and brass nipples.

[oldpotatoe]

Originally Posted by cribbit

I've done 32h a few times. I normally do four at a time and it's pretty straightforward.

How do I do 28h triple cross? My brain isn't getting it and I'm struggling to find videos - I'm probably bad at searching.

Same way to lace 28h, just instead of 'over, under', it's 'over, over, under'..with longer spokes it's easy. I do 'drop spokes' right side, turn wheel ovr, drop spokes other side..turn wheel over, rotate hub(either right for inside pulling or left for outside pulling), and then spokes inside out..lacing over, over, under.

Unless the hub flange diameter is large, I do 3 cross 28 on all rears, 2cross on fronts.

[tctyres]

I do what oldpotatoe does, so I don't know how you're lacing -- I drop all the "innies" in, flip over, and drop all the "outties" in.

Originally Posted by cribbit

I've been trying to look into this and finding no real information. Do you have a source / info on impact?

Originally Posted by ultraman6970

28 triple cross?? depends a lot of the hub IMO because at 3x the spokes start overlapping a little bit more than what you really want.

For a symmetrically drilled hub, divide the number of holes by 9 and round down. A 36h hub can be laced 4x without crossing another spoke hole. A 32h hub can be laced 3x without crossing another spoke hole. If you lace a 32h hub 4x, the spoke will cross directly behind or in front of another spoke hole.

Max crosses (symmetric hubs):
36h: 4x
32h: 3x
28h: 3x
24h: 2x
20h: 2x

Edit: Relative strength of the wheel in torque goes as crossings squared. A 4x rear has a multiplier of 16; 3x is 9, 2x is 4. This simple relationship explains why radially laced drive side spokes on standard road wheels always fail catastrophically. It's not a matter of "if" but "when." NB: This is a straight apples-to-apples comparison: same type of spokes, same rim sort of thing. Road front wheels see a lot less torque, so are often laced radially. Track front wheels ridden only on a track just about never see a torque because they are ridden on a dead flat surface. Lateral strength is mainly in the rim. The spokes just keep the hub centered laterally.

[cribbit]

So how do I decide between 2 cross and 3 cross? Front wheel, disc btw. Wouldn't 3 cross give me better strength for the torque of disc braking?

[oldpotatoe]

Originally Posted by cribbit

So how do I decide between 2 cross and 3 cross? Front wheel, disc btw. Wouldn't 3 cross give me better strength for the torque of disc braking?

Yes..no payback for 3cross and 28 unless big flanges..spoke overlap

[Mark McM]

Originally Posted by tctyres

Edit: Relative strength of the wheel in torque goes as crossings squared. A 4x rear has a multiplier of 16; 3x is 9, 2x is 4. This simple relationship explains why radially laced drive side spokes on standard road wheels always fail catastrophically. It's not a matter of "if" but "when."

This makes no sense; what wheels with crossed spokes don't have enough torsional strength? None that I know of. And where did this square of the crossings come from? And there are a number of wheels with radially laced drive side spokes, and they don't suffer from an inordinate number of broke spokes. (And how do spokes fail "catastrophically"? They either break, or they don't.)

Originally Posted by tctyres

NB: This is a straight apples-to-apples comparison: same type of spokes, same rim sort of thing. Road front wheels see a lot less torque, so are often laced radially. Track front wheels ridden only on a track just about never see a torque because they are ridden on a dead flat surface. Lateral strength is mainly in the rim. The spokes just keep the hub centered laterally.

Any front wheel without a hub break sees virtually no torque, road or track. Lateral strength relies on both the rim and the spokes, but the primary factor is the spokes - after all, they are the only thing that connects the tire/rim to the hub. With the same type or rim and hub, increasing the number of spokes dramatically improves wheel lateral strength.

[Mark McM]

Originally Posted by cribbit

So how do I decide between 2 cross and 3 cross? Front wheel, disc btw. Wouldn't 3 cross give me better strength for the torque of disc braking?

The decision between 2 and 3 cross with 28 spokes should primarily be determined by how the spokes interact with the hub flange. On some hub flanges, a 3 cross pattern may cause the spokes to overlap the heads of adjacent spokes, or may cause the spokes to overlap the flange too much, so a 2 cross may be better. With 28 crossed spokes, the individual spoke loading due to torques (driving or braking) is minimal, so the number of crossings has minimal effect on spoke longevity.

[tctyres]

Originally Posted by Mark McM

This makes no sense; what wheels with crossed spokes don't have enough torsional strength? None that I know of. And where did this square of the crossings come from? And there are a number of wheels with radially laced drive side spokes, and they don't suffer from an inordinate number of broke spokes. (And how do spokes fail "catastrophically"? They either break, or they don't.)

Any front wheel without a hub break sees virtually no torque, road or track. Lateral strength relies on both the rim and the spokes, but the primary factor is the spokes - after all, they are the only thing that connects the tire/rim to the hub. With the same type or rim and hub, increasing the number of spokes dramatically improves wheel lateral strength.

I take catastrophe as more than one spoke breaks and/or the flange breaks from the stresses. There are plenty of radial nds rear wheels on the internet that show a "catastrophe." If one breaks, that's one thing. If they all break in unison, that's a catastrophe, and the rider is likely going to crash.

Tandem, loaded touring, and mtb wheels all come to mind as wheels that have additional torques.

Track wheels don't even have the torque from a brake. I consider 2x up front safety for braking and potholes.

Rims vs. spokes: Take a double walled aluminum rim and try to bend it with your hands one spoke length apart. Wheels flex all the time laterally in the spokes from hard pedaling.

I'll see if I can find the reference on the crossings, same with the lateral strength. It was a discussion with an engineer whose PhD was on the bicycle wheel. I will try to find his contact info.

[dddd]

Catastrophic failures due to radial spoking can be due to the added stress on the hub flanges pulling outward instead of tangent to the flange.

But then the real catastrophe occurs when (due to radial spoking pattern) a spoke flange breaks and then leaves two consecutive same-side spokes without tension. The localized force imbalance at the rim then prevents the wheel from even turning in the frame or fork.

Crossed spoke wheels that suffer a flange "explosion" of two spokes will lose tension in locations along the rim that are spread out enough to likely allow the wheel to keep turning.

[Mark McM]

Originally Posted by tctyres

I take catastrophe as more than one spoke breaks and/or the flange breaks from the stresses. There are plenty of radial nds rear wheels on the internet that show a "catastrophe." If one breaks, that's one thing. If they all break in unison, that's a catastrophe, and the rider is likely going to crash.

It is true that when a flange breaks with radial spokes, then it is likely that several adjacent spokes will be released. But that's more of an issue with the whether the hub is designed for radial spoke loads. But that's still a moot point, because if the spokes on the other flange are crossed, then the radial spokes experience no additional loads due to wheel torque.

Originally Posted by tctyres

Tandem, loaded touring, and mtb wheels all come to mind as wheels that have additional torques.

Please explain where these torques come from. The wheel bearings separate the wheel/hub form the rest of the bike and pass virtually no torque loads between the wheel and the fork/frame. Unless there is an additional coupling between the fork/frame and hub (such as disc or drum brake), then there is no significant spoke loading due to torques.

Originally Posted by tctyres

Rims vs. spokes: Take a double walled aluminum rim and try to bend it with your hands one spoke length apart. Wheels flex all the time laterally in the spokes from hard pedaling.

The rim is supported by the spokes, with only short spans between the spokes. The rim can not flex if the spokes don't flex, so the stiffness of the spokes will greatly affect the stiffness of the assembled wheel. Grab the two ends of a spoke, and try to stretch it. You'll find that the spokes are far stiffer than any rim.

Also consider this: The heaviest spokes weigh about 230 grams for 32 spokes - but for many wheels, the total weight of the spokes is about half of that. The weight of the lightest rims is about 280 grams - but most rims weigh far more than this. If you were to take a few dozen grams off of the rim on the average wheel, and add extra spokes equal to the same weight, I guarantee the wheel will have more lateral stiffness.