Aero wheels for a small light rider

freebsd_frank wrote:Why are

freebsd_frank wrote:

Why are the wider rims better than Open Pros? I’ve told you above that rims have little to do structurally with a wheel but anchor spokes and tyres. Your opinion is entirely bogus; you cant tell the difference between wheels with rims of similar section and weight. Mechanically and aerodynamically any
difference is going to be so vanishingly small as to be not measurable let
alone to be noticed by the rider.

The reasons why wider road rims might be advantageous have been talked about ad naseum in the cycling press over the last couple of years, it has little to do with structural issues, e.g. the effect on tyre volume are very, very, very far from vanishingly small so it would be odd if nothing could be noticed at all, wouldn’t you say ?

I got a bit bored leafing

I got a bit bored leafing through the last post. I guess frank has a bit
of a crush on Jobst brandt?

I’m sorry my post bored you. I guess it contained a bit too much in the way
of technical information with relevant links. Stuff you as a “professional”
engineer don’t seem to find interesting. Perhaps a more suitable occupation
for you would be as a toilet attendant.

As for my “crush” on Jobst Brandt, he wrote the definitive book on spoked
bike wheels. You should read it some time before you next spout your worthless
opinions on wheels on this forum. He would have whooped your sorry @rse
as an engineer. Fact.

If I were frank I would worry more about the Open Pros reputation for
cracking around the eyelets than whether a factory built wheel’s spokes
have been properly stress relieved.

That’s because you’re a muppet masquerading as an engineer. FYI, spokes that
haven’t been properly stress-relieved will fail in no short order. Read the
link I posted, sh*t-for-brains.

As for Open Pros cracking around the eyelets. All Al alloy componentry
subjected to cyclical stresses will eventually fatigue fail because it doesn’t
have a fatigue limit like steel. It’s why you should change your Al alloy
handlebars if you’ve done a lot of miles because if you don’t, you’ll end up
on your face when (not if) they fail. I don’t know if this was the reason that
they increased the diameter of alloy handlebars

FWIW many (most?) ‘factory’ wheels are built by hand anyway. Certainly the
Shimano ones are.

Hogwash. They’re laced and tensioned by machine. But are they stress-relieved?
The manufacturers don’t publish useful data like that, just marketing guff.

I have both 32 spoke and low spoke count wheels. Both are fine (i.e. the low spoke count wheels have not proved to be ‘weak’) and have lasted without problems for years, although as another poster recommended above I prefer a wider rim than the open pro.

Anecdote filling in for engineering facts. You should be ashamed of yourself
as an engineer.

What are the technical reasons for preferring a wider rim to an Open Pro?
Thought so: none, or you would have posted them.

I would buy something that has been designed for racing – e.g. low spoke count, deeper section rim with a profile optimised to reduce drag across a wide range of yaw angles (yes, wind tunnel testing does look at this),

How about a link? Not from a manufacturer (they’re trying to sell something)
but somebody independent. If the engineers doing the testing are of the calibre of you, what do you rate their chances of getting anything more than worthless
data? Vanishingly small, I’d say.

The original poster said they trialled some deep section clinchers and was MUCH FASTER on the same course than the previous year on mid section alloy rims, and so was asking for suggestions for aero wheels.

You obviously think it was the exact same conditions. I’ll let you into a
secret: the wind is a variable, so her anecdote is worthless; isn’t it?
Engineer? There are some useless ones in any profession, I guess.

In fact, in your last post you seem to be saying that all wheels except
those built by someone who has read Jobst Brandt are unsuitable for any
use at all.

No, anybody who builds wheels in accordance with the engineering principles
and facts established by Brandt. I gave a link to Musson’s book on
wheelbuilding who’s wheelbuilding method is based on Brandt.
I don’t need to read Principia to know that Newton was right.

I don’t know if this thread attracts techy types, but I am another mechanical engineer (B.Eng. + M.Sc. + 20 years in aerospace manufacture and quality roles).

Thanks for the info. That’s the last time I’m flying.

crikey wrote:Frank, you don’t

crikey wrote:

Frank, you don’t half write some rubbish.

It’s nice outside, go for a ride eh?

Quite, just what I am going to do, 300km overnight Audax on my new Ti frame. I guess I will be imagining any difference it makes to my comfort levels and speed?

the 32 hand-builts feel more

the 32 hand-builts feel more stable and more comfortable (not a contradiction – more spokes, round spokes and more crossing).

More stable than a deep section? Possibly. You wont have
side winds catching your low profile rims as much. But on the contrary,
your probably heavier deep section rims will have more angular momentum
at any given speed and require a greater torque applied via the handlebars for
the wheel to be deflected off course.

More comfortable? You’re imagining things. FYI, a properly tensioned spoked
wheel will not “give” to any significant degree. Not to an extent that you can
feel it. Doesn’t matter whether your spokes are laced radially or cross,
number of spokes and section of spoke or type of rim.
The spokes are made of stainless
steel which is a strong but not very elastic material. They will stretch a bit
and return to their original shape/length, but the longitudinal stress you have to subject a spoke to, for it to visibly stretch is considerable even though a
spoke is thin. To stretch it visibly, you’d have to apply a load that would
cause the material to pass it’s elastic limit ie. you’d have permanently
stretched the spoke and it would henceforth be useless. Rims don’t really
come into it, their purpose is as an attachment for the spokes and tyres.
Those who say “my deep section carbon rims are so strong” are talking rot.
What your 32 crossed spoke handbuilt wheels will be though, are much stronger.
Assuming, they’ve been built by a competent wheelbuilder.

A long time ago I asked my LBS to build me a set of wheels. The f*ckwit,
didn’t even realise that you had to use different length spokes on the rear DS
and NDS or he calculated the spoke lengths wrong. Hence, the rim wasn’t
centered between the dropouts!

After that experience, I built my own. I recommend others do likewise.

Perhaps it’s because of your different tyres on that wheel, you ask? No.
A racing tyre blown up to it’s manufacturer’s specification ie. at least
100psi, has the constituency of a rock. You can feel the gravel embedded in the
tarmac. Those who think they can tell the difference between a 23mm tyre
blown up to spec and a 25mm; they’re also fantasists. Those who think brand x
feels more comfortable than brand y? Fantasists. Those who buy expensive
carbon fibre seatposts because they “smooth” the ride and are more
“comfortable”? Fantasists. There’s a whole load of
them riding the TdF ATM. I saw on this site, that the journalist spotted that
one of the pros (or rather his mechanic had on his orders) had gone to the
trouble of re-branding his tyres to brand x from brand y. The pro was
obviously a fantasist who thought brand x was more comfortable/faster/better
than brand y. Yes, some tyres use grippier rubber compounds than others so you
wont get so many miles out of pair. Some are more puncture resistant than
others dependent on how they’re carcassed and with what material. But more
“comfortable”? Fantasy.

This re-badging dishonesty has been going on for years. When the pros used to
ride steel frames, it was strongly rumoured that some teams whose frame
manufacturers didn’t have a Ti frame in their range would use
re-badged/sprayed Ti Litespeeds!

Also worth noting that open pros have pretty much had their day, they are a good cheap training rim but not a patch on the newer wider rims from Velocity (Pacenti and so on, but I don’t have those). I base this *opinion* on having ridden both, one after the other on the same hubs with the same lacing pattern and the same tyres.

So what did you notice having ridden both? I suggest you noticed nothing. Why
are the wider rims better than Open Pros? I’ve told you above that rims have
little to do structurally with a wheel but anchor spokes and tyres. Your
opinion is entirely bogus; you cant tell the difference between wheels with
rims of similar section and weight. Mechanically and aerodynamically any
difference is going to be so vanishingly small as to be not measurable let
alone to be noticed by the rider.

Was the problem that the Open Pros were cheap? Why have they “had their day”?
Or is it because they have been around a longtime and hence not “trendy”
enough? My opinion: Open Pros have been around for a long time because it’s
difficult to improve on them and riders who have ridden them over the many
years they’ve been available must come back for more because they haven’t
been failed by them. They recommend them to friends. They say to themselves,
these rims were cheap, why should I risk going for a newer more expensive and
untrusted brand? That’s why Mavic keeps making them. You’ve no idea of the
tooling costs of making a different section Al alloy rim. It’s considerable.
Why tool-up when your product is still selling? It doesn’t make economic
sense.

I got a bit bored leafing
I got a bit bored leafing through the last post. I guess frank has a bit of a crush on Jobst brandt?

If I were frank I would worry more about the Open Pros reputation for cracking around the eyelets than whether a factory built wheel’s spokes have been properly stress relieved. FWIW many (most?) ‘factory’ wheels are built by hand anyway. Certainly the Shimano ones are.

I have both 32 spoke and low spoke count wheels. Both are fine (i.e. the low spoke count wheels have not proved to be ‘weak’) and have lasted without problems for years, although as another poster recommended above I prefer a wider rim than the open pro.

I like my hand builts on my commuter and ‘cross bike as they are easily re-trued and re-rimmed. I wouldn’t buy a 32 spoke wheel specifically to race / time trial on – I would buy something that has been designed for racing – e.g. low spoke count, deeper section rim with a profile optimised to reduce drag across a wide range of yaw angles (yes, wind tunnel testing does look at this), wider rim to better match tyre profile etc.

In fact, even when I race cyclocross I swap out my box sections for rims that shed mud better.

The original poster said they trialled some deep section clinchers and was MUCH FASTER on the same course than the previous year on mid section alloy rims, and so was asking for suggestions for aero wheels.

frank answered that by ignoring the request completely and denying that it is possible for wheels to have any real world aerodynamic benefits over box section rims and 32 spokes. In fact, in your last post you seem to be saying that all wheels except those built by someone who has read Jobst Brandt are unsuitable for any use at all.

I don’t know if this thread attracts techy types, but I am another mechanical engineer (B.Eng. + M.Sc. + 20 years in aerospace manufacture and quality roles).

Sorry, how rude of me, you

Sorry, how rude of me, you asked for a response on some ‘facts’ and I assume from an ‘engineering’ point of view.

That would be nice. As a CEng I would value your perspective on the matter
rather than the name-calling and pop-psychology.

1 aero wheels are weak: there is no inherent reason why this should be the case. Wheels with a lower spoke count will be less robust all other things being equal, however all other things are not equal. Deeper sections will have higher Section modulus and therefore resist bending better than shallow sections.

The strength of a spoked wheel lies overwhelmingly in it’s spokes, they are
in tension and the section modulus of the rim doesn’t really come into it. You
just need it strong enough that the spokes don’t pull through the eyelets on
the rim. I believe, that carbon fibre composite rims have re-inforcement at
the eyelets to stop spokes pulling through when they’re tensioned, during
the wheelbuilding stage or when out riding.

Aero wheels are weak because they are generally radially laced (which is not
as strong as conventional crossed lacings, although they’re crossed on the
drive side rear, for obvious reasons) and they use too few spokes. The fewer
the spokes, the weaker the wheel. As I said in a previous post, my Khamsins
are only rated for riders of no more than 82Kgs – that’s a weak wheel. They’re
medium section but 20 plain gauge spokes (butted or bladed spokes have a
higher Young’s modulus as they have been work-hardened in the forming process)
radially laced. Radial lacings with lower spoke counts also mean that the
spokes are in much higher tension. Campag Record hubs can’t be built radially
because the flanges fail. You have to use something beefy like steel forged
hubs. Because of this high spoke tension, you also need a stronger rim which
in practice means heavier.

You say that a deep section wheel will resist bending better than a lower
section rim. While true, composite carbon fibre is a very brittle material and
for all intents and purposes it will fail before it bends to any degree.
With Al alloy, as long as you stay below it’s yield strength you won’t put a
“set” into it. Go over it and you will. I prefer the behaviour of Al alloy in
practice: go down a pothole and you may bend the rim and break the odd spoke
or two. With the carbon fibre, if the stress isn’t along the lay-up of the
fibre, then you’re largely dependent on the polymer it’s embedded in for
strength ie. nothing like as strong as the Al alloy.

Have the engineers: manufacturing and
mechanical, working for the wheel manufacturers done all their homework about the various stresses in a wheel?
Have they read Brandt’s “The Bicycle Wheel”? I don’t know. As a CEng, you must
have come across people everyday who haven’t done their homework. Who was the
engineer who thought about using carbon fibre composite for spokes? They failed
catastrophically; they obviously hadn’t read Brandt.

A link to Brandt’s obit on this site (he unfortunately died recently):

http://road.cc/content/news/150563-rip-jobst-brandt-author-bicycle-wheel-engineer-cycling-guru

If you think I’m rude, you obviously never read Brandt on usenet. He would
batter any clueless newb or fashion follower into submission with engineering
and scientific fact. Never saw him bested; he knew his onions when it came to
engineering.

There’s an archive of some of his writings at Sheldon Brown’s site:

http://sheldonbrown.com/brandt/index.html

Read what Sheldon Brown has to say about the Spoke Scam:

http://sheldonbrown.com/wheelbuild.html#spokes

Somebody posted earlier about their spokes failing on their fairly cheap
wheels. Almost certainly because the wheels were factory made and the spokes
not being stress-relieved in the building process:

http://sheldonbrown.com/brandt/stress-relieving.html

My advice to the poster is build your own. I use Roger Musson’s instructions
(Roger has read Brandt):

http://www.wheelpro.co.uk/wheelbuilding/book.php

2 aero wheels are not very aero in most conditions:
there’s pretty good evidence that they are more aero most of the time than
box section rims,….

Have you got a link for that? If it’s wind-tunnel testing, have they tested
when the wind isn’t straight on to the wheel? Which it is most of the time if
you’re not on a track or in still conditions. I don’t know if you know
anything about sailing but I think it might be a comparable situation
where you get what’s called “apparent wind” which is the wind you get
if you add that created by the boats forward velocity to the existing wind.
Anyway, the action of the sails and the keel results in a vector of forces
being set-up, with a forward component driving the boat along. Of course, you
can trim sails, tack and alter the boat’s course. None of which you can do on
a bike.

so I assume what you’re getting at here is that they’re not aero enough
for enough of the time?

Very much so.

I think that’s up to the purchaser but again looking at the intended use, triathlon, drafting is illegal, courses are usually not mountainous and the handling issues are limited because there is no bunch racing so if there is a situation where the benefits are most likely to be realised this is probably it.

IIRC, the triathlon bike stage is about 40k. If it’s windy and the course
is winding or loops back on itself, then the wind is going to be coming from
all sorts of directions. I don’t know if deep section rims would be any
advantage in those circumstances.

3 they’re expensive: my first suggestion costs £400, roughly the same as your hand built open pro example. And there are non aero options up to the £1k limit given. So no, not necessarily. You can go cheaper than that if you’re willing to compromise on weight but given the budget available, there seemed no reason to. They certainly can be expensive like most things but it’s not a given.

I don’t know if the expensive wheels are that much better than the cheaper
ones. They all use radial lacings with few spokes with the
disadvantages that brings: weaker, heavier rims and hubs. The expensive ones
seem to use butted or bladed spokes: an advantage not for the minimal aero
gains but because they have a higher E and UTS so less likely to fail. But do
any of these machine laced spokes get properly stress-relieved? Or do they
just go round with a tensiometer and say: job done.

I’ll stick with my handbuilt Open Pros 32 spokes 3x. I know they’ve been built
properly and will last and I still think the OP would be better off with them
too. It’s an unfashionable opinion but so be it.

I might buy some. They look
I might buy some. They look cool :H

I don’t own the wheels in

I don’t own the wheels in question, I never said I did. I offered some opinions relevant to the question based on my research. I sought to help which was
graciously acknowledged.

Your “research” such as it was, seems to have consisted of going to various
online cycling shops and finding wheels within the original poster’s budget
and telling him without even posting a link(s).

Your “opinions” seemed to consist of nothing more “than brand x is cheaper
than brand y which costs z.”

I sought to help which was graciously acknowledged.

He acknowledged your help because he’s a brown-noser and a lickspittle and
you’re a regular poster, not because your “research” and “opinions” were of
any particular use. I’m sure the OP can use Google too.

I have a degree in engineering, I am a chartered engineer, I am a
director of one of europe’s larger engineering consultancies.
I don’t struggle in technical discussions, it’s what I am paid to do.

If you’re a CEng and don’t struggle in technical discussions, then why don’t
you discuss the technical merits of deep section rims and their low spoke
counts? Or do you know SFA about it? If so isn’t it about time you informed
yourself before telling somebody to blow £1000 on a set of weak wheels?

I don’t particularly care about being popular but I do care about common courtesy and reasonable manners. I challenged you as you seem not to care for these aspects of normal social interaction. The technical term for someone who has no regard for others opinions or feelings is ‘sociopath’.

If you don’t particularly care about being popular, why do you play to the
peanut gallery? As for caring about common courtesy and reasonable manners,
I’ve never heard such hypocritical BS. Who was it who wrote:

Hey freebase frank, if I buy 32 spoke 3 cross open pros like you say will I become an obnoxious, self opinionated @rse too?

It was you, you muppet. The self-regarding hypocrisy is staggering. You should
be thoroughly ashamed of yourself with posting such hypocritical guff but I’m
sure you’re not.

Where we disagree is that you have ignored the original post…

I replied to it with my opinions and technical arguments with regards to deep
sectioned rims using low spoke counts laced radially. You, a CENG, haven’t.
You just abused me and then in a latter post said such behaviour was abhorrent
to you.

I find aggression is often the result of insecurity, personally.

I didn’t come on here to hear your blatherings on pop-psychology, stick to the
engineering and try and post something worthwhile reading next time.