Spoke Count

[hubgearfreak]

just a suspicion that you have tyres smaller than 37mm, and no springs in the saddle.

i suggest that we all re read this thread and see where the anger started? it's a real mystery to me, as is picking wheels because they don't look crap. they have a hard job to do, and in sometimes rough conditions.

simon & GK, you are clearly happy to ride around with a low spoke count, i am not. we won't change each others opinions, so lets just be civil, hey?

as for the OP....weigh yourself and your bike, is it around 100kgs?
ok, now weigh 36 spokes, minus 36 holes in the rim AND 36 holes in the hub and deduct that from your total.

if it's a significant difference, or you're happy to forgo strength for weight, or you wish to choose wheels that are aesthetically elegant/ light go for it.

 

[Smokin Joe]

You don't forgo strength with a lower spoke count. The weight of the machine is suspended almost wholey by the few spokes which are at the top of the wheel at or near to 90 degrees from the hub at any one time, whether the wheel has 36 or 16 spokes. Integrety of build and quality of rim are the defining factors in the quality of the wheel. Hitting a pothole or a car will do the same damage to a rim no matter what the number of spokes, because the spokes only work in tension, they are too thin to bear any compression loading.

BTW Simon, how did you hit the back of a bus? Didn't you see it, or were you on the mobile at the time?

 

[hubgearfreak]

You don't forgo strength with a lower spoke count.

you're contradicting both Jobst Brandt and Gerd Schraner. both also go on to say that thinner, lighter spokes and rims are a better bet than fewer spokes if you're interested in weight reduction

The weight of the machine is suspended almost wholey by the few spokes which are at the top of the wheel

not according to Jobst Brandt

you can make up your own theories on the science & art of bicycle wheels if you wish, or you could start by reading the books by the two authors above, who are generally recognised as knowledgeable in their field.

 

[gkerr4]

you are right of course - there is no need for anger and you are right that you wil always like higher spoke count wheels and I will probably always like lower spoke counts.

You are also right about the fact that my bike does have narrower than 37mm tyres - it has 23mm in fact. and my specialized Toupe saddle most definitely does not have springs in it!!

who (or what?) is jobst brandt?


I thought that most road wheels worked in tension only I have to admit - because Mavic make a big fuss that their new r-sys wheels are the only wheels on the market to operate in compression as well - hence they can make a lighter rim (albeit with massive carbon tubes as spokes!)

 

[hubgearfreak]

You are also right about the fact that my bike does have narrower than 37mm tyres - it has 23mm in fact. and my specialized Toupe saddle most definitely does not have springs in it!!

i'm guessing that your bike is a bit lighter than mine

who (or what?) is jobst brandt?

http://preview.tinyurl.com/288vkz
well worth a read. even if you never build a wheel, it's interesting to know their construction & stresses

 

[andrew_s]

The weight of the machine is suspended almost wholey by the few spokes which are at the top of the wheel

not according to Jobst Brandt

The old "hangs from the top spoke"/"stands on the bottom spoke" argument
It's all a matter of semantics, and both points of view are equally valid, provided we are talking about a normal wheel under normal loads.

In an un-loaded wheel, all the spokes are equally in tension. When a load is applied to the hub, the tension in the bottom spoke is reduced by the amount of the load, all other spokes remaining in an unchanged state. The reduction in tension in the bottom spoke is because the rim is slightly deformed where it contacts the ground.

Smokin Joe looks at the forces on the hub, sees a large force acting upwards (tension in top spoke), and the applied load and a smaller force (bottom spoke) acting downwards. This situation he describes as the hub hanging from the top spoke.

Jobst et al look at the forces exerted by the bottom spoke. It's got the load pushing down at the top, and the reaction force from the ground pushing up at the bottom. The spoke is thus being compressed, and is supporting the load on the hub. The top spoke is in exactly the same state as it was in before the hub was loaded, and is therefore nothing to do with situation.


Back to spoke count...
Wheel strength is all in the build quality. I've known someone hit the back of a parked car at 30mph(+), and have an undamaged 32-spoke wheel after.
Low spoke-count wheels are better built than most 32/36 wheels - they have to be.
The qualities that some describe as a stiff wheel are those I describe as harsh.
With 18 spokes, if one goes you are walking. With 36, I've known people still riding with 6 broken spokes. Spokes can be brokes other than as a result of a poor build - eg someone else's pedal in them.

 

[Smokin Joe]

The old "hangs from the top spoke"/"stands on the bottom spoke" argument
It's all a matter of semantics, and both points of view are equally valid, provided we are talking about a normal wheel under normal loads.

In an un-loaded wheel, all the spokes are equally in tension. When a load is applied to the hub, the tension in the bottom spoke is reduced by the amount of the load, all other spokes remaining in an unchanged state. The reduction in tension in the bottom spoke is because the rim is slightly deformed where it contacts the ground.

Smokin Joe looks at the forces on the hub, sees a large force acting upwards (tension in top spoke), and the applied load and a smaller force (bottom spoke) acting downwards. This situation he describes as the hub hanging from the top spoke.

Jobst et al look at the forces exerted by the bottom spoke. It's got the load pushing down at the top, and the reaction force from the ground pushing up at the bottom. The spoke is thus being compressed, and is supporting the load on the hub. The top spoke is in exactly the same state as it was in before the hub was loaded, and is therefore nothing to do with situation.


Back to spoke count...
Wheel strength is all in the build quality. I've known someone hit the back of a parked car at 30mph(+), and have an undamaged 32-spoke wheel after.
Low spoke-count wheels are better built than most 32/36 wheels - they have to be.
The qualities that some describe as a stiff wheel are those I describe as harsh.
With 18 spokes, if one goes you are walking. With 36, I've known people still riding with 6 broken spokes. Spokes can be brokes other than as a result of a poor build - eg someone else's pedal in them.

I would disagree with that. Try leaning on a spoke and it will bend in half, I can't see how it supports any compression load at all.

 

[gkerr4]

http://preview.tinyurl.com/288vkz
well worth a read. even if you never build a wheel, it's interesting to know their construction & stresses

looks interesting - I do actually fancy having a go at building my own wheels - only really for my fixed gear bike where i will be looking for 28h track hubs on something like DT1.1 or CXP33 rims and the lightest spokes I can get my hands on.

however, seeing as I am only really likely to build this single set of wheels - the tools / equipment would seem to be an expensive one-of cost for one pair of wheels - probably best to just let a shop build em.

 

[bianco]

looks interesting - I do actually fancy having a go at building my own wheels - only really for my fixed gear bike where i will be looking for 28h track hubs on something like DT1.1 or CXP33 rims and the lightest spokes I can get my hands on.

however, seeing as I am only really likely to build this single set of wheels - the tools / equipment would seem to be an expensive one-of cost for one pair of wheels - probably best to just let a shop build em.

I'm having this debate with myself, but I figure I'll save money in the long run and I'll have a lot of knowledge gained.

 

[Steve Austin]

The Jobst Brandt book is a top read, even if you never build your own. Truly fascinating the science behind wheel building.

As for equipment: you only need a spoke key. that is it.

 

[gkerr4]

I'm having this debate with myself, but I figure I'll save money in the long run and I'll have a lot of knowledge gained.

thats just it - i doubt I would save money in the long run as the only wheels I want to build are for the fixed. I prefer factory built for my proper road-bike

i do get a lot of satisfaction from the build process though - i build my current road bike (an S-Works roubaixSL with campag centaur carbon g/s and Eurus wheels) and enjoy the upgrade / rebuild / general tinkering aspect of bike owership.

 

[Smokin Joe]

Personally, I think the like of Brandt turn a simple piece of engineering construction into an over-complicated science which is of little relevence outside the laboratory.

I've built wheels that have stayed true for years and I am certainly no expert.

 

[hubgearfreak]

The Jobst Brandt book is a top read, even if you never build your own. Truly fascinating the science behind wheel building.

As for equipment: you only need a spoke key. that is it.

as for a dishing tool, a 30" peice of 2"x1" with three screws in works perfectly well, and i'm guessing that you're building wheels for a bike with forks? - there you go

 

[hubgearfreak]

Smokin Joe looks at the forces on the hub, sees a large force acting upwards (tension in top spoke), and the applied load and a smaller force (bottom spoke) acting downwards. This situation he describes as the hub hanging from the top spoke.

Jobst et al look at the forces exerted by the bottom spoke. It's got the load pushing down at the top, and the reaction force from the ground pushing up at the bottom. The spoke is thus being compressed, and is supporting the load on the hub. The top spoke is in exactly the same state as it was in before the hub was loaded, and is therefore nothing to do with situation.

I would disagree with that. Try leaning on a spoke and it will bend in half, I can't see how it supports any compression load at all.

it's not just the top spoke, or just the bottom spoke. or both, but all.

if you imagine a wheel with just a few spokes at the top, and a few at the bottom, then you're right, the top spokes wouldn't snap, but the bottom ones would bend in half. this would leave the rim considerable below 622mm top to bottom and a far greater diameter from 3 o'clock to 9 o'clock.
ie. it would have collapsed into an oval. the rest of the spokes that are neither top nor bottom keep the wheel round under load

Wheel strength is all in the build quality.....Low spoke-count wheels are better built than most 32/36 wheels - they have to be.

exactly, they have to be well built, as they are inherently weaker. an equally well built 36 spoker will only be a tiny bit heavier, but a great deal stronger

 

[simonali]

Subject diversion: anyone seen the new Crank Brothers wheels? An interesting design.