Different spoke count front-rear, still OK with hub brakes?

[dabac]

Quite recently Sheldon Brown wrote something along the lines of "If you have the same number of spokes front and rear either your front is heavier than it needs to be or your rear is weaker than it should" somewhere on this site.

For a "traditionally" configured bike, rim braked and with a dished rear this makes good sense, but what about bikes with hub-mounted brakes, either drum or disc?

Rear still has the disadvantage of dish, carries the heavier load during most riding, and has to deal with the propelling torque. But the front can become heavily loaded during braking, particularly on pavement/tarmac, so is it still recommendable to use a lower spoke count front?

(I think I'm clear on the forces involved, but I'm uncertain about order of influence/magnitude..)

I assume the original recommendation is mainly a spoke fatigue issue, so (how) would the addition of hub-mounted brakes change the recommendation? Is there a possibility of causing front wheel failure through brake generated torque? Or through dynamic weight transfer during braking?

(this would be with a drum brake hub(high flange), so front would be symmetrically dished)

I'm not thinking of anything particularly extreme here, maybe a 36(3X, half radial)-28(2X) combo on a lightly loaded commuter.

Functionally I could very probably get away with a much more generic build, but where's the fun in that?

Cheers,

 

[dabac]

Quite recently Sheldon Brown wrote something along the lines of "If you have the same number of spokes front and rear either your front is heavier than it needs to be or your rear is weaker than it should" somewhere on this site.

For a "traditionally" configured bike, rim braked and with a dished rear this makes good sense, but what about bikes with hub-mounted brakes, either drum or disc?

Are there really NO opinions available regarding this matter?

It's not like this forum to miss a chance to debate the various merits and drawbacks to different spoke counts and configurations!

(ah well, there's always the fallback of trial-and-error...)

 

[daveornee]

Quite recently Sheldon Brown wrote something along the lines of "If you have the same number of spokes front and rear either your front is heavier than it needs to be or your rear is weaker than it should" somewhere on this site.

For a "traditionally" configured bike, rim braked and with a dished rear this makes good sense, but what about bikes with hub-mounted brakes, either drum or disc?

Rear still has the disadvantage of dish, carries the heavier load during most riding, and has to deal with the propelling torque. But the front can become heavily loaded during braking, particularly on pavement/tarmac, so is it still recommendable to use a lower spoke count front?

(I think I'm clear on the forces involved, but I'm uncertain about order of influence/magnitude..)

I assume the original recommendation is mainly a spoke fatigue issue, so (how) would the addition of hub-mounted brakes change the recommendation? Is there a possibility of causing front wheel failure through brake generated torque? Or through dynamic weight transfer during braking?

(this would be with a drum brake hub(high flange), so front would be symmetrically dished)

I'm not thinking of anything particularly extreme here, maybe a 36(3X, half radial)-28(2X) combo on a lightly loaded commuter.

Functionally I could very probably get away with a much more generic build, but where's the fun in that?

Cheers,

You could write an email to Sheldon and see what he says.
I think that using a front hub brake, even one that is symetrically spoked, increases the dynamic loading significantly.... especially due to the fact that front wheels carry most of the braking load.
If you don't already have the front hub and the rim for it, why not go for 36 spokes front as well?

 

[alfeng]

... (this would be with a drum brake hub(high flange), so front would be symmetrically dished)

I'm not thinking of anything particularly extreme here, maybe a 36(3X, half radial)-28(2X) combo on a lightly loaded commuter.

Functionally I could very probably get away with a much more generic build, but where's the fun in that?

FWIW. I treat the brake side on a front disc hub as if it were the drive side on a rear hub -- consequently, I chose to lace a 32h 700c CXP14 rim onto an XT hub with a x4 on the BRAKE side & x1 on the non-brake side -- straight 14g spokes, of course [just the facts ... not necessarily trying to keep THAT controversy alive].

The rear was x4 on both sides with 14g spokes.

A front disc hub is NOT symmetrically dished, BTW.

 

[dabac]

Thanks for replying.

FWIW. I treat the brake side on a front disc hub as if it were the drive side on a rear hub --

I've been thinking along those lines too, but been a bit uncertain about how far to carry the comparison. Undoubtedly a rear wheel would see more "drive impulses" than a front would see "brake impulses", but OTOH I could probably brake harder than I can accelerate....

...I chose to lace ... x4 on the BRAKE side & x1 on the non-brake side

Can't say that it's a combo I would have thought of anytime soon, but I can see what you're aiming for. Isn't x4 considered a bit awkward to lace, denpending on the hub?

...A front disc hub is NOT symmetrically dished, BTW.

But the drum brake front hub I'm thinking of using would be.

 

[dabac]

Thank you for replying.

You could write an email to Sheldon and see what he says.

I believe I did that. But either it got lost when my email provider was having some difficulties or he'd been too busy to reply.

I think that using a front hub brake, even one that is symetrically spoked, increases the dynamic loading significantly.... especially due to the fact that front wheels carry most of the braking load.

That seems highly probable, but to what degree? Enough to have negative consequences? Wheel failure is usually fatigue related(and not sudden overloads) and you don't brake half as much as you pedal.

..If you don't already have the front hub and the rim ...

I have the front hub already. It's actually a 36H but I planned to leave some holes empty. If Rinard can get away with it so can I...

Leaving holes empty in the rim though isn't tempting even for me...

.... why not go for 36 spokes front as well?

Well, mainly because the statement from Sheldon and the final line from my original post:Functionally I could very probably get away with a much more generic build, but where's the fun in that?
Unless it's too weak to function it'd still make more sense than a crow foot lacing for instance.

It's not like I really need this bike anyhow so I thought I'd indulge myself with some light experimenting - unless you guys think this is a certain recipe for wheel collapse and road rash.

Cheers,

 

[alfeng]

Can't say that it's a combo I would have thought of anytime soon, but I can see what you're aiming for. Isn't x4 considered a bit awkward to lace, denpending on the hub?

Yes, x4 is problematic on a low flange hub, but not as much as most people would like you to think ... and, it really isn't a problem on a high flange hub, IMO ... but, that's just my opinion, I suppose -- i.e., IMO, having a spoke in contact with (or, lay over in the case of a low flange hub) another spoke in the flange area is no more a real problem than the J-bend OR the contact between interlaced spokes ... so, it really becomes more of a cosmetic issue (at least, IMO!).

Lacing the non-brake side x1 came down to a cosmetic issue (radial lacing is a generally BAD IDEA, IMO). A x2 lacing & x3 lacing didn't look the way I wanted (at the time) AND I deduced/decided that the x1 lacing would provide adequate lateral "support" with the stiff CXP14 rims.

You know, the only thing that you need is a good spoke calculator (I use Dan Halem's http://www.geocities.com/d_halem/wheel/wheel.html because I find it exceedingly easy to use, FWIW) & an inclination of how you want the wheel to function & look ...

If your drum brake hub is truly symmetrical, then I would probably lace it x4 on the drum side & x3 (or, x2) on the non-drum side.

 

[alfeng]

I have the front hub already. It's actually a 36H but I planned to leave some holes empty. If Rinard can get away with it so can I...

NB. Having a mis-match in the number of holes in the hub & rim introduces a REAL, potential aggravation that you need to be aware of -- that is, you will probably need at least THREE DIFFERENT SPOKE LENGTHS (using more lengths is probably slightly better) ...

I added FOUR holes to a 28h 3-speed hub (steel) so that I could lace it to a 32h 700c Open Reflex rim, and THREE different spoke lengths is what I ended up using ...

 

[dabac]

Yes, x4 is problematic on a low flange hub, but not as much as most people would like you to think ... and, it really isn't a problem on a high flange hub, IMO ...

And this hub would qualify as high flange... Dang! I reall didn't need another option on how to build these wheels!

..radial lacing is a generally BAD IDEA,

So I've heard, yet I have a radial front wheel built around an old LX hub that seems to be doing fine so far, several seasons down the line.

Lacing the non-brake side x1 came down to a cosmetic issue ...A x2 lacing & x3 lacing didn't look the way I wanted (at the time) AND I deduced/decided that the x1 lacing would provide adequate lateral "support" with the stiff CXP14 rims.

Makes sense to aim for something that's more than "only" functionally pleasing while you're still at it, doesn't it?

You know, the only thing that you need is a good spoke calculator ..I find it exceedingly easy to use, .. an inclination of how you want the wheel to ... look ...

It has an illustration feature? That WOULD make a change from the DT one that I normally use.

Cheers,

 

[dabac]

NB. Having a mis-match in the number of holes in the hub & rim introduces a REAL, potential aggravation that you need to be aware of -- that is, you will probably need at least THREE DIFFERENT SPOKE LENGTHS

Duly noted. I've seen (and toyed with) some spoke calculators / formulas that claim to deal with this problem. but I don't feel quite confident with the answers given. Some LBS will get a repeat customer for some days when it comes to final assembly. The "normal" length should be enough to get the wheel to hold its shape though, which would make it easier to determine the length of the other ones.

I added FOUR holes to a 28h 3-speed hub (steel) ...

Now THAT sounds tricky, it must have been an exceedingly helpful flange design to leave you with enough material for such an operation.

 

[alfeng]

So I've heard, yet I have a radial front wheel built around an old LX hub that seems to be doing fine so far, several seasons down the line.

Radially lacing places more stress on the flange than crossed lacing UNLESS the hub has been designed for radial lacing -- e.g., DT redesigned/re-spec'd their flanges to have a larger diameter.

Since a MTB generally has a front suspension AND fat, low-pressure-by-comparison tires, the negative ride characteristics of radial lacing aren't noticed ...

Radially laced (front) wheels on a ROAD bike are for those who are slaves-to-fashion OR who are gluttons for punishment, IMO.

 

[alfeng]

Now THAT sounds tricky, it must have been an exceedingly helpful flange design to leave you with enough material for such an operation.

The flange size on a 3-speed hub is equivalent to the size of a high flange hub, so there WAS enough space (certainly, no more tightly spaced than the spoke holes on a 36h low flange hub) -- two extra holes per side -- I would NOT have done it with an alloy hub, BTW.

 

[dabac]

NB. Having a mis-match in the number of holes in the hub & rim introduces a REAL, potential aggravation that you need to be aware of -- that is, you will probably need at least THREE DIFFERENT SPOKE LENGTHS ..

Now I remember. I found a link some time ago that offered a modified spoke calculator that dealt with mismatched no. of holes in hub/rim, but it only generated ONE new recommended spoke length. This seemed odd to me since the spoke length deviation shouldn't be static.
If you have a group of spokes with an empty hole at each side at the hub the middle spokes in this group will be pretty darn close to where they would have been in a matched configuration, while the ones closest to the hole will show the most deviation, particlularly the ones reaching "across" the hole.

 

[alfeng]

It (Dan Halem's spoke calculator) has an illustration feature? That WOULD make a change from the DT one that I normally use.

BTW. Dan Halem's spoke calculator does not have "an illustration feature." It does have an extensive (though dated & incomplete -- e.g., the ubiquitous MAVIC Open Pro is not included, so I use the Open Reflex data & generally adjust the ERD, accordingly) database whose variables you can modify quite readily -- i.e., start with a something that is close (if not included), modify the one-or-two variables ... et voila!

So, you MAY actually have to measure the ERD (effective rim diameter) and locate/select a similar (in dimension) rim in the database ... OR, hold a "new" rim next to all your other rims to see if anything appears to be close enough to use as a starting point. For example, I have some UKAI 700c (622-17) rims which are not in the database, but which I ascertained to have an ERD comparable to a "standard" sew-up rim; and consequently, I simply used the Campagnolo Strada (tubular) rim for the spoke calculation.

When I laced up the CXP14 rims to the XT disc hubs, I selected the Campagnolo Hi-Flange front hub & changed the value for the left flange offset.

When I've looked at OTHER calculators, they were not any easier/faster to use -- at least, the way I use it -- so, I continue to use Dan Halem's.

BTW. With Halem's calculator, you can/should ROUND DOWN to a slightly shorter spoke.

 

[alfeng]

Now I remember. I found a link some time ago that offered a modified spoke calculator that dealt with mismatched no. of holes in hub/rim, but it only generated ONE new recommended spoke length. This seemed odd to me since the spoke length deviation shouldn't be static.
If you have a group of spokes with an empty hole at each side at the hub the middle spokes in this group will be pretty darn close to where they would have been in a matched configuration, while the ones closest to the hole will show the most deviation, particlularly the ones reaching "across" the hole.

Yes. I (would) wonder how that calculator worked out the ONE, compromise spoke length ... in theory, half of the spokes on each side would actually have a different length, but the centimeter-of-threading (some spokes do have MORE) does leave wiggle-room in the calculation.

FWIW. I essentially used trial-and-error to get the THREE different spoke lengths that I used (thank heavens I have my own spoke threader!) ...

I think I began with the calculated length, laced up the rim, and then inspected for (looked at ... measured/reckoned/guessed-at) the variance ... and, THREE different lengths was the minimum I was able to use on a 32h rim (I suspect that FOUR different lengths might have been slightly better).

If I had been lacing up a "dished" wheel whose rim & hub had a mismatched count (BTW. there is a miniscule offset on a 3-speed hub which I chose to ignore as being inconsequential), then then I would have needed (?) SIX different lengths.

 

[dabac]

Yes. I (would) wonder how that calculator worked out the ONE, compromise spoke length ...

See here:
Basically, convert the hole mismatch into a fractional value and enter it in the spreadsheet.

..thank heavens I have my own spoke threader! ...

I wouldn't mind one of those myself, but then again I like butted spokes. Can't remember if I've ever seen butted spoke blanks sold anywhere...

 

[alfeng]

See here:
Basically, convert the hole mismatch into a fractional value and enter it in the spreadsheet.

Thanks ...

Very interesting!?!

I wonder when Damon Rinard laced that particular wheel ... and, why!?!

... Because I'd need to be EXTREMELY motivated to want to mate a commonly available 36h hub [it's not an expensive-by-comparison Hugi or Chris King hub, and Rinard isn't stranded in a Third World country without access to components] to a 24h rim rather than to choose-and-use an equally common 32h hub for the particular rim & wheel build ... and, thereby have an effortless construction.

But, as an exercise (x2/x0) with the disparate components he chose, I guess/HOPE(!) it was worth Damon Rinard's effort.

It's too bad Rinard didn't indicate the actual spoke lengths that one would NORMALLY use & the ones that his calculation ultimately suggested rather than leave it to the reader to recreate his calculations (from scratch).

AND, subsequently, it would be nice to see the outer edge of the rim where the nipple is seated to see how-much-or-how-little spoke protrudes from the end of the nipple's head ... AND, it would be nice to know whether the spokes he used had a now-typical 1cm of threads, or more ... plus, whether Rinard used long (now used for aero rims) nipples.

Of course, although Rinard says that he's laced a few rear wheels with the particular lacing, he doesn't say how soft/stiff the wheel is compared with a more traditional lacing (i.e., how the wheel actually performs & the weight of the rider using the wheel).

Calculations can be an expedient to illustrate what might be; but, their revelation is incomplete when compared with empirical observation ...

Having said all of that, I do have my suspicion as when/why Rinard did what he did, but the conjectured why (vs. the actual) would depend on the when ...

I wouldn't mind one of those myself, but then again I like butted spokes. Can't remember if I've ever seen butted spoke blanks sold anywhere...

I got my spoke threader USED, otherwise I'm sure I could not have justified the acquisition ... it's an unnecessary luxury ... but, very convenient ... unfortunately, it does encourage unconventional adventures.

BTW. Double-butted "blanks" are probably not practical because of the variability in length of the alternate gauged middle section of different length spokes ...

Regardless, it really is easier to start with a spoke that is within a centimeter of the desired length because if there are NO existing threads, then (at least with my old, CYCLO threader) you would need to nip the tip of the spoke (an easy enough, added step which would nonetheless become tedious after a while) to assist the rollers begin the threading.

 

[dabac]

.. I'd need to be EXTREMELY motivated to want to mate a commonly available 36h hub ..to a 24h rim ... I guess/HOPE(!) it was worth Damon Rinard's effort.

I guess it all depends on the amount of effort a certain undertaking actually will cost you, and the amount of enjoyment it will give you.
I've certainly done equally questionably things mainly because I could, I wanted to and I had the time.
If you want details, ask me about when I swapped out a single-piece crank for a conventional 3-piece...

..It's too bad Rinard didn't indicate the actual spoke lengths that one would NORMALLY use & the ones that his calculation ultimately suggested .

I agree, it would have been interesting to know how much difference there actually is. I know from experience that 3 mm mismatch can be survivable, so maybe this isn't such a big deal?

..AND, subsequently, it would be nice to see the outer edge of the rim where the nipple is seated to see how-much-or-how-little spoke protrudes from the end of the nipple's head ...

As long as the nipple either doesn't bottom out or the spokes protrudes enough to risk puncturing(on a double-walled rim) I could certainly live with a little overshoot.

.. it would be nice to see .. whether Rinard used long (now used for aero rims) nipples.

Maybe that would be an easy way around this, use one spoke length and two kinds of nipples?

.. Of course, although Rinard says that he's laced a few rear wheels with the particular lacing, he doesn't say how soft/stiff the wheel is compared with a more traditional lacing (i.e., how the wheel actually performs & the weight of the rider using the wheel)..

Unless he felt compelled to cut back on the spoke tension to avoid overstressing the less-than-ideally loaded flanges the differences between a 24-24 and a 24-36 would surely be minimal? (assuming same spoke patterns, spokes, flange width etc...)

..I got my spoke threader USED, ..... but... it does encourage unconventional adventures.

You should see what having vacuum-bagging and laminating gear does to you then, not to mention the lathe and a welder ...

..Double-butted "blanks" are probably not practical because of the variability in length of the alternate gauged middle section of different length spokes ...

There's been a thread here about how different butted spokes have different lengths from where the threads stops and the thinned-out section begins, which might indicate that the butting is done in fewer and bigger steps than the actual threading and cutting. Might not help you if you alternate between road wheels and MTB wheels, but might certainly be enough to handle left/right and front/rear issues within the same type.