New rear wheel 24 or 28?

ibericb · May 7, 2015

tvad said:
My fault.

Thanks for playing anyway.

Don't want the engineers to be insulted, compared to us science type they're rather temperamental .

tvad · May 7, 2015

Certain wheel builders publish suggested spoke counts and weight limits. November Bicycle, for example, publishes 20/24 for 175lbs and 20/28 for 200lbs for the Alloy Nimbus Ti build (with an asterisk comment "sorta. Weight guidelines can vary widely based on terrain and riding style. If you're unsure which build will provide you with the best performance, contact us").

With that in mind, would those here who recommend 28 spokes over 24 spokes for the OP who weighs 140lbs agree or disagree with the November Bicycle spoke count/weight guidelines?

Jay Strongbow · May 7, 2015

tvad said:
Certain wheel builders publish suggested spoke counts and weight limits. November Bicycle, for example, publishes 20/24 for 175lbs and 20/28 for 200lbs for the Alloy Nimbus Ti build (with an asterisk comment "sorta. Weight guidelines can vary widely based on terrain and riding style. If you're unsure which build will provide you with the best performance, contact us").

With that in mind, would those here who recommend 28 spokes over 24 spokes for the OP who weighs 140lbs agree or disagree with the November Bicycle spoke count/weight guidelines?

I most certainly would especially with Stans 340 being one of the rim options.

All I know is I'm 145 and have had issues with 24 but not 28 and that I don't see 28 taking any performance away from me. Granted my riding style and high volume combined with really bad roads might require more than the typical person my size.

My case for 28 might be shakey but what's the case for 24 other than 'because you can get away with it"?

rruff · May 7, 2015

Mike T. said:
**Engineers into wheelbuilding (that I'm aware of) -

Roger Musson.
Jobst Brandt (I haven't read the late great Jobst's book in years; the calcs could be there)
Meltingfeather (frequent poster at MTBR "Wheels" section)

And me.

For someone who weighs 140 and isn't in the habit of destroying things, 16f and 20r would be plenty with those rims. 18f and 24r should have a ton of margin. I weigh 170, and if I could buy 16h SL23s I'd run 16f and 20r myself. This is based on my (good) experience with much lighter rims.

Quantifying the degree of strength or life increase would require a detailed FEM or destruction testing, and I'm not aware of any being published. And it still wouldn't answer the question of how much is enough for a particular rider.

IME the likely scenario for ruining a rim is to hit a sharp pothole or rock and dent the brake tracks. Normally the number of spokes is not a factor, unless the rim is prone to cracking, or you regularly put loads on it that causes spokes to go slack.

Mike T. · May 7, 2015

rruff said:
And me.

Ron, I'll add you to my list. I dunno what I'm going to do with it though. I have enjoyed Meltingfeather's (engineer over at MTBR) debates about wheel structures over the years. He never backs down from his stand on skinny spoke gauges (DT Rev in his case) for most people - and he builds mostly 29'er disc brake MTB wheels and whether a bike stands on its spokes or hangs from them. That latter "debate" is always classic.

For someone who weighs 140 and isn't in the habit of destroying things, 16f and 20r would be plenty with those rims. 18f and 24r should have a ton of margin. I weigh 170, and if I could buy 16h SL23s I'd run 16f and 20r myself. This is based on my (good) experience with much lighter rims.
Quantifying the degree of strength or life increase would require a detailed FEM or destruction testing, and I'm not aware of any being published. And it still wouldn't answer the question of how much is enough for a particular rider.
IME the likely scenario for ruining a rim is to hit a sharp pothole or rock and dent the brake tracks. Normally the number of spokes is not a factor, unless the rim is prone to cracking, or you regularly put loads on it that causes spokes to go slack.

I'm someone to whom the tiny benefit of a few less spokes isn't worth the potential penalty of less spokes - a wheel might not turn in frame or fork if a spoke breaks. I would think that the warp in the rim would be greater if there are less spokes in a wheel. Yes, rim stiffness would be a variable factor here - of unknown effect to a mere mortal like me. I could be called a wheel curmudgeon or overly cautious as even I can't ever remember a front wheel spoke snapping on me and it's got to be 20+ years since a rear spoke broke on me** I just like to think of me as "practical". I'm just lucky that I don't have to satisfy those who think they have to have wheels with the least possible spoke numbers.

**Never a broken rear spoke ever since I found out about the benefits of careful spoke tension balance.

robt57 · May 7, 2015

jnbrown said:
My current bike has the same wheelset except with H2 hubs and has 20F 24R. I weigh 140lbs and have had no issues at all with the 24 hole rear

How old are these wheels? Miles etc?

Have those rims even been out on the market for long enough time [compared to 90s velocity rim I built] where one can take your 'no issues' comment to be significantly relevant. Which kind of follows with which, a 24 or 28 will be in service longer in higher likelihood...

I always am weary of space between the spokes.

The lower profile the rim, the more weary I am. I trust the spoke more than the rims is what I am getting at I guess...

I can say I love the SL23 rims/wheels I built. But @ 210lb and 28 Spokes and 100 miles on them, I sure can not make any claims of 10k miles. Although my sense is they should be good wheels in the long run from experience of the process and similar? products I can make claims about...

jnbrown · May 7, 2015

It seems there is no clear right or wrong answer to this.
I happen to be an engineer, but electrical not mechanical, but have built quite a few wheels.
Since 24 has worked for me and I think hub dimensions are the same, I will stick with 24. You have to draw a line somewhere, you can argue if 28 is better then why not 32? i think its diminishing returns.
One thing I didn't see mentioned much was the stiffness of the rim which i believe these rims are pretty good in that category.

robt57 · May 7, 2015

jnbrown said:
It seems there is no clear right or wrong answer to this.

If it was my question "how old are said wheels" there is actually no answer.

I'd lean towards feeling the wider and thus stiffer rim make for the correct side of the equation. But again, in my minds eye low spokes = more tension and stress on each spoke hole/bed/area and expect the lower the weight of rim and spoke bed thickness the more that feeds to the other side of the equation...

Will they rims last 5 year or ten. Or 3 and not 10 etc...

Jay Strongbow · May 7, 2015

jnbrown said:
It seems there is no clear right or wrong answer to this.
I happen to be an engineer, but electrical not mechanical, but have built quite a few wheels.
Since 24 has worked for me and I think hub dimensions are the same, I will stick with 24. You have to draw a line somewhere, you can argue if 28 is better then why not 32? i think its diminishing returns.
One thing I didn't see mentioned much was the stiffness of the rim which i believe these rims are pretty good in that category.

They're not.

rruff · May 8, 2015

Mike T. said:
whether a bike stands on its spokes or hangs from them. That latter "debate" is always classic.

Jobst RIP was the originator of that one I believe. I'm still amazed that some people can't get it.

I'm someone to whom the tiny benefit of a few less spokes isn't worth the potential penalty of less spokes

Yes, but it is easy to get carried away, too. If 28 is good, then how about 32 or 36? If the guy is a normal rider and weighs 140 lbs then a well built rear wheel with 20 light spokes and the SL23 should be fine for 20-30k miles, or more. 24 is extra safe IMO.

Yes, rim stiffness would be a variable factor here - of unknown effect to a mere mortal like me.

It's a large one. Radial stiffness effects lateral stiffness of the wheel a lot also. I built a lot of wheels with the XR200 rim and 28 spokes for riders considerably heavier than him. The SL23 makes a much stiffer wheel.

Rim stiffness doesn't effect the torque loading on the spokes, which is something to consider. But a 140lb rider won't be putting a lot of torque into a wheel. Even if he is strong (high power/ weight), he will climb fast because he is so light. It is the really heavy guys who can over-torque a light wheel on a steep climb.

**Never a broken rear spoke ever since I found out about the benefits of careful spoke tension balance.

Yep, balance is very important, and a broken spoke is a very rare occurrence in a well built wheel. Your site is a great primer for getting it right.

dcgriz · May 8, 2015

Take two wheels using the same type rim and spokes. One wheel uses 36 spokes at a tension of 1000 N per spoke and the second wheel uses 24 spokes at a tension of 1500 N per spoke. What these two wheels share in common? Identical rim compression at 5730 N or 1288 lbf.

But it's not wise to drive the spoke tension that much high, you say. Ok, then add four more spokes and your 28 spokes, now tensioned at 1285 N, will give you your 5730 N rim compression. How about 32 spokes @ 112 N? Same rim compression.

That's what adding or taking away spokes means, IMO. Whether or not the resulting rim compression is optimized to offset the load applied by the rider's weight, pedaling stroke output and the direction its being applied from for a number of load cycles are questions that need significantly more input and analysis than is typically offered by simply stating the rider's weight. However, even if one had this information, it is doubtful what he would do with it short of a Finite Element analysis which still would be subject to variables to predict deflections. Since hiring proffesionals to conduct a FE analysis is not what most are willing to do, they rely on the wisdom of the wheelbuilder to determine the "correct" number of spokes from empirical exposure to what seems to be working for most people with perceived similar predicaments.

So, if you have a wheel that seems to be indestructible for thousands of miles, it would be a fair assumption to make that the number of spokes could be reduced while maintaining the same spoke tension as the original wheel and still end up with a rim compression suitable for the rider's load profile. Can't be more specific than that so its best to stop obsessing about it and go ride your bike.

Aladin · May 8, 2015

Skimming this thread.. it's hilarious. Typical.

Sans any measurables... hub width etc.. one can't make comparisons. Comparing identical builds just adding 4 spokes a 28 divides those stresses over of course more units. Only the rider can decide if an ounce is worth carrying. I've no use or interest in 11's, I wonder what left side tensions are though... compared to what you riding now. Likely at that weight level it'd be irrelevant. Build quality is the bottom line.

I ride a 28 at 200 lbs.. albeit 18-10 .. a hybrid triplet design of my own lacing. Left side tensions around 85% of DS.. you don't need to run excessive tensions right side to get a stable left. No spoke prep.. glue here. And they stand.

dcgriz · May 8, 2015

Aladin said:
I ride a 28 at 200 lbs.. albeit 18-10 .. a hybrid triplet design of my own lacing. Left side tensions around 85% of DS.. you don't need to run excessive tensions right side to get a stable left. No spoke prep.. glue here. And they stand.

Nor you need exotic lacing patterns or 85% tension ratios. All you need is the NDS at a tension value above 55 kgf to keep unglued spokes from loosening up. Most 11s hubs will let you do that with a normal 2x or 3x lacing, just by raising the DS tension a tad. If you need fancy lacing and glued spokes to keep a wheel together, you havent used enough spokes or enough tension or enough care to equalize the tensions.

jnbrown · May 8, 2015

Aladin said:
Skimming this thread.. it's hilarious. Typical.

Sans any measurables... hub width etc.. one can't make comparisons. Comparing identical builds just adding 4 spokes a 28 divides those stresses over of course more units. Only the rider can decide if an ounce is worth carrying. I've no use or interest in 11's, I wonder what left side tensions are though... compared to what you riding now. Likely at that weight level it'd be irrelevant. Build quality is the bottom line.

I ride a 28 at 200 lbs.. albeit 18-10 .. a hybrid triplet design of my own lacing. Left side tensions around 85% of DS.. you don't need to run excessive tensions right side to get a stable left. No spoke prep.. glue here. And they stand.

I believe the spacing on the WI T11 and H2 hubs are the same, so you are not loosing anything by going to 11 speed and you are gaining a gear. I will going from 12-28 to 12-29 so slightly wider gear range and less jumps between gears. On my current wheels I used DT revs on the NDS, with the thinner spokes there is less chance of them going slack.

Jay Strongbow · May 9, 2015

jnbrown said:
I believe the spacing on the WI T11 and H2 hubs are the same, so you are not loosing anything by going to 11 speed and you are gaining a gear. I will going from 12-28 to 12-29 so slightly wider gear range and less jumps between gears. On my current wheels I used DT revs on the NDS, with the thinner spokes there is less chance of them going slack.

Again, it's not.

Anyway, the debate isn't so much about what the answer is but what the question is. It's either "is 24 enough" or "is 28 too many". Almost certainly and no are the answers so either 24 or 28 is fine depending which question you ask so I'd prefer to ask the latter and be on the side of caution. "because I can get away with it" isn't a good enough reason for me to choose 24 over 28 (though in the past it was) given I can't detect any down side to 28. I own and ride otherwise identical 24 and 28 spoke rear wheels and if I'm slower with the 28s I certainly can't tell so can't think of a reason why not.

robt57 · May 9, 2015

Maybe go with 28h and 14/17 spokes, or 24 with 14/15.

I am 210lb and just did SL23 28hole with 14/17 except I used 14/15 for the 7 drive side trailing spokes and used brass nip for the 7 and AL nips for the rest. So you could do that if you have the ability to wind up a wheel more so than not. I don't think I would go less that 28 for me for a rear, and no less than 24 for a front and would use 14/15 on those. If you weigh less than me you could push farther than I. But I think I you save 2 gram approx per spoke with 14/17 over 14/15. X 56 spokes is 1/4 lb lighter simply put. Another bit with AL nips over brass etc etc.

BelgianHammer · May 9, 2015

jnbrown,

Can I ask, since you write "I weigh 140lbs and have had no issues at all with the 24 hole rear....", do you have a friend who has 32 or 36H rear wheel they could loan you, so you could ride a couple of days? What I mean is, I think if you were somehow made to wear those lower eye blinders and you were not allowed to see your bike and/or its components before you got on & pedalled away, do you think you could tell the difference between a 24H and 28H rear rim (with all other components remaining the same)? With 24 to 32, you might and/or should. But between 24 and 28?? I honest to Gosh think you couldn't tell any difference between a 24H and a 28H rim (with everything else remaining equal) if you weren't told about it before you got on the bike and/or knew it from building it yourself. It's just way too subjective for most of us. But, that said, if you are one of those incredible 140lb power sprinters and/or out of the saddle long power climbers, then maybe you might and there'd be no harm, no foul, in adding four more little itty-bitty spokes (wheel life, in terms of durability, sure would go up...that you might notice).

And if you forsee increasing amounts of Ben & Jerrys pints raining down on you & your body's aging future, having 4 more spokes in the rear is going to be de rigueur :thumbsup:

Jay Strongbow · May 9, 2015

robt57 said:
Maybe go with 28h and 14/17 spokes, or 24 with 14/15.

I am 210lb and just did SL23 28hole with 14/17 except I used 14/15 for the 7 drive side trailing spokes and used brass nip for the 7 and AL nips for the rest. So you could do that if you have the ability to wind up a wheel more so than not. I don't think I would go less that 28 for me for a rear, and no less than 24 for a front and would use 14/15 on those. If you weigh less than me you could push farther than I. But I think I you save 2 gram approx per spoke with 14/17 over 14/15. X 56 spokes is 1/4 lb lighter simply put. Another bit with AL nips over brass etc etc.

yeah, thicker drive side and brass nips is another one with no definitive answer (that I'm aware of) so probably, like the original question, I'd answer with why not error on the side of caution. I say that inspite of doing the opposite with my most recent wheel build.

I've spoken with several extremely qualified wheel builders about both thicker spokes on the drive side and brass nips and opinions are mixed. Some say good idea and others don't see the benefit. No one has said it's a bad idea and only mention weight as a reason not to.

Aladin · May 9, 2015

dcgriz said:
Nor you need exotic lacing patterns or 85% tension ratios. All you need is the NDS at a tension value above 55 kgf to keep unglued spokes from loosening up. Most 11s hubs will let you do that with a normal 2x or 3x lacing, just by raising the DS tension a tad. If you need fancy lacing and glued spokes to keep a wheel together, you havent used enough spokes or enough tension or enough care to equalize the tensions.

LMFAO. Thanks for the good chuckle.

To the 'from the tad' world.. ahhhh... I'll practice 'catch and release'. You couldn't wrap your noodle around it.

Aladin · May 9, 2015

Jay Strongbow said:
yeah, thicker drive side and brass nips is another one with no definitive answer (that I'm aware of) so probably, like the original question, I'd answer with why not error on the side of caution. I say that inspite of doing the opposite with my most recent wheel build.

I've spoken with several extremely qualified wheel builders about both thicker spokes on the drive side and brass nips and opinions are mixed. Some say good idea and others don't see the benefit. No one has said it's a bad idea and only mention weight as a reason not to.

Count me Jay from the 'no benefit' camp. I've come to the conclusion so long as the NDS has enough stretch NOT to completely de-tension and give 'head slap' they don't break. Most all riders won't notice/benefit from heavier spokes DS... with a tension of 120 kgf. 'Heavier' spokes just stretch less during the cycle... and that butted section no matter the gauge wire keeps the elbows fatigue and breakage down.

New rear wheel 24 or 28?

ibericb

tvad

Jay Strongbow

rruff

Mike T.

robt57

jnbrown

robt57

Jay Strongbow

rruff

dcgriz

Aladin

dcgriz

jnbrown

Jay Strongbow

robt57

BelgianHammer

Jay Strongbow

Aladin

Aladin

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