Commuting wheels

Pete Biggs said:

Ben C said:

David Lloyd said:

On 16 Nov, 08:53, Ben C <[email hidden]> wrote:
>
> Lighter wheels won't really make much noticeable difference to
> performance I don't think, because the difference in weight won't
> be all that much. Tyres and tyre pressures make more difference.

Lighter rims really do make a big difference. Being nearly the
furthest point out from the hub, they have a great impact on radial
inertia. The mass of anything that rotates has a disproportionate
impact on energy input required.

That is true. In fact, the energy stored in a rotating wheel
travelling at a given speed is exactly twice the energy stored in the
same wheel travelling at that speed and not rotating (treating the
wheel as a thin cylinder with all its mass on the outside).

Lightweight racing rims weigh about 400g each. A much chunkier rim
perhaps 600g.

Perhaps not supplied with a road bike.

Quoted message said:

That's 200g per rim,

In your imaginary extreme example.

It was intended to be an extreme example (because I set out trying to
demonstrate that the rim weight doesn't make any difference, even for an
extreme example).

But I thought I'd better check, and so had a quick look at Mavic's
website. They had a 700C rim that officially weighed 540g. So I thought
600 was actually a fairly reasonable estimate.

It was this one, a touring rim, the A119:

http://www.parker-international.co.uk/ProductDetails/mcs/productID/5326

Quoted message said:

Quoted message said:

so 400g for both, and you can double that because of the rotational
inertia. So that's like an extra 800g (from the point of view of
power required to accelerate the bike on the flat).

Less than 1% of the combined weight of rider and bike. All the same,
perhaps you might notice 800g.

Mavic Open Pro, road rim often recommended for good wheels: 425 grams
(officially). Open Sport, bog standard cheap road rim: 490 grams.

That's a difference of 65 grams, and often the difference is less than that
between a "good" rim and a "cheap" rim. Also note that actual weights vary
from example to example due to the manufacturing process. Open Pros
can weigh as much as 450 grams.

Agreed, so it might be worth saying yes you might possibly notice a
difference between a touring rim and a road rim, but probably not
between two different road rims.

Ben C said:

Pete Biggs said:

Ben C said:

On 2007-11-16, David Lloyd <[email hidden]> wrote:
> On 16 Nov, 08:53, Ben C <[email hidden]> wrote:
>>
>> Lighter wheels won't really make much noticeable difference to
>> performance I don't think, because the difference in weight won't
>> be all that much. Tyres and tyre pressures make more difference.
>
> Lighter rims really do make a big difference. Being nearly the
> furthest point out from the hub, they have a great impact on radial
> inertia. The mass of anything that rotates has a disproportionate
> impact on energy input required.

That is true. In fact, the energy stored in a rotating wheel
travelling at a given speed is exactly twice the energy stored in
the same wheel travelling at that speed and not rotating (treating
the wheel as a thin cylinder with all its mass on the outside).

Lightweight racing rims weigh about 400g each. A much chunkier rim
perhaps 600g.

Perhaps not supplied with a road bike.

Quoted message said:

That's 200g per rim,

In your imaginary extreme example.

It was intended to be an extreme example (because I set out trying to
demonstrate that the rim weight doesn't make any difference, even for
an extreme example).

OK, sorry about that, I didn't take in what you were saying.

Keep up the good work ;-)

~PB

in message
<[email hidden]>,

Darth. (') said:

[Also posted on the forum at BikeRadar - need to get replacements this
weekend!]

After nearly 5,000 miles of London potholes, sudden braking at traffic
lights and near misses with transit vans the wheels on my Specialised
Sirrus have finally given up the ghost. The braking surface on the
rear one is completely worn and the front wheel isn't far behind. I'm
looking for advice on replacements.

Ideally I'd like to get some wheels where I'll notice the difference.
I'm a fairly fast commuter (20-24 mph) so a nice light set of wheels
would be great fun. However, I'd also like something quite sturdy so
that I don't have to replace them again for a while. Are these
mutually exclusive?

No. I've had both the cheapest and (now) the most expensive Mavic Ksyriums.
These are incredibly strong, durable wheels. The ES ones are also
extremely light wheels. I really recommend them - but they are not cheap,
and they do look flash which may be too much of a thief magnet for riding
in London. The alternative is a good pair of hand-built wheels, which
would also be very strong and durable and wouldn't look so flash.

http://www.jasmine.org.uk/~simon/album/kitchenpr0n/

The front wheel of my old, cheap Ksyriums was in a crash in which I hit

Quoted message said:

Or does the frame mean that a wheel upgrade is not worth it? Should I
stick to something sensible and boring and save the money for the new
bike, planned for Spring 2008?

Why buy a new bike? Why not upgrade a component at a time, as you can
afford it?

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

Anagram: I'm soon broke.

in message <[email hidden]>, Ben C

(') said:

Darth. said:

[Also posted on the forum at BikeRadar - need to get replacements this
weekend!]

After nearly 5,000 miles of London potholes, sudden braking at traffic
lights and near misses with transit vans the wheels on my Specialised
Sirrus have finally given up the ghost. The braking surface on the
rear one is completely worn and the front wheel isn't far behind. I'm
looking for advice on replacements.

The brake tracks will always wear out. I don't think it makes much
difference what rim you've got, although it may be that some brake pads
scrape away the rims more rapidly than others.

Brake tracks, as you say, will always wear out, but 5,000 miles seems a
very short life to me. I too would look at brake blocks as possible
culprits.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; 99% of browsers can't run ActiveX controls. Unfortunately
;; 99% of users are using the 1% of browsers that can...
[seen on /. 08:04:02]

in message <[email hidden]>, Pete Biggs

(') said:

David Lloyd said:

Ben C said:

Lighter wheels won't really make much noticeable difference to
performance I don't think, because the difference in weight won't be
all that much. Tyres and tyre pressures make more difference.

Lighter rims really do make a big difference.

How many grams and how much difference?

Quoted message said:

Being nearly the
furthest point out from the hub, they have a great impact on radial
inertia. The mass of anything that rotates has a disproportionate
impact on energy input required.

Only when accelerating.

Quoted message said:

This is why, when considering
upgrading a bike, wheels should be the first thing to be swapped out.

Even if it means spending big money to save 50 grams per rim? I don't
think so.

Hang on, what's big money and what's big money? This bike has commuted him
in and out of London for a year, at an average of around twenty miles a
day. In doing so, it has saved a fairly sizable chunk of money, whichever
alternative method of transport it replaced. Given that, putting a £500
pair of wheels onto it would still be economically justified, if they
provided him with reliability and the performance he seeks.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

Do not sail on uphill water.
- Bill Lee

David Damerell said:

You'd do just as well making sure you pee before setting off.

That sounds like a good idea anyway :-)

-- PMM

In article <[email hidden]>,

David Damerell said:

ie, twice if they really were at the very edge (which they're not) for
acceleration only, which a moment's consideration will show makes the
difference between light rims and heavy ones about diddly for normal
purposes. You'd do just as well making sure you pee before setting off.

The reasons to try to reduce the mass of a bike are IME largely to do
with the ease of acceleration (and braking). I suppose how true this
is for you depends on how hilly your usual rides are. I calculate
that accelerating from 0-36kph is equivalent in energy to a 5m height
increase so this will depend very much on whether you're largely
commuting at rush-hour in a flat but busy city centre or touring in
mountain ranges. And of course it also depends how much you value the
potential energy you get back on the downhill.

The point here is that because the wheels rotate, the effect on the
acceleration performance of a particular extra rim mass is roughly
twice the effect of the same mass fixed to the frame.

It's true that because the rim isn't exactly in contact with the road
the rotational energy is slightly less than the linear energy but as
Ben C says the difference is small.

So as a rule of thumb if you mainly ride in cities on the flat, and
are willing to make some sacrifice (be it money, robustness, or
whatever) for a particular weight saving in a static piece of the
bike, you should be willing to make the same sacrifice for going on
for as little as half the weight saving in the rim, tube or tyre.

--
Ian Jackson personal email: <[email hidden]>
These opinions are my own. http://www.chiark.greenend.org.uk/~ijackson/
PGP2 key 1024R/0x23f5addb, fingerprint 5906F687 BD03ACAD 0D8E602E FCF37657

Ian Jackson said:

I calculate
that accelerating from 0-36kph is equivalent in energy to a 5m height
increase

Negotiating traffic lights does not necessarily result in loss of
mechanical energy. A proficient cyclist will stop pedalling in advance
of a red light, slow down without using the brakes and will often be
able to time his arrival at a light with it changing to green,
particularly on a commute where you get to know the timing of the lights
on your route.

Only braking results in a loss of mechanical energy.

Quoted message said:

The point here is that because the wheels rotate, the effect on the
acceleration performance of a particular extra rim mass is roughly
twice the effect of the same mass fixed to the frame.

If so, a 300g weight difference between a set of Aksiums and a set of
Ksyriums translates in 600g dead weight. At a bike weight of 8kg and a
rider weight of 75kg this equates to 0.36%. The price difference between
a set of Aksiums and Ksyriums is what, £200? Lotta money to pay for a
0.36% advantage (on a commuter bike).

--
Membrane

In article <[email hidden]>,

Darth. said:

[wants new wheels]

I have roughly the same question. My old rear wheel (came with the
bike, not sure what it was) has had too much abuse - a crash, a thug's
boot, and now my new route to work has unavoidable speed bumps.
The wheel doesn't hold its true any more.

So far I've seen three recommendations all of which are 20-spoke
wheels. Isn't this mad ? Surely the optimum spoke number is greater
than 20.

I tried to find what the rim weight was of a Mavic Aksium so I could
compare it to separately-marketed rims but without success.

--
Ian Jackson personal email: <[email hidden]>
These opinions are my own. http://www.chiark.greenend.org.uk/~ijackson/
PGP2 key 1024R/0x23f5addb, fingerprint 5906F687 BD03ACAD 0D8E602E FCF37657

In article said:

In article <[email hidden]>,

David Damerell said:

ie, twice if they really were at the very edge (which they're not) for
acceleration only, which a moment's consideration will show makes the
difference between light rims and heavy ones about diddly for normal
purposes. You'd do just as well making sure you pee before setting off.

The reasons to try to reduce the mass of a bike are IME largely to do
with the ease of acceleration (and braking).

If you can brake hard enough to lock your wheels/get thrown over
your handlebars, then reducing the rotating weight isn't going to
make any difference (and reducing the static weight of both wheels
isn't going to shift the centre of gravity much). So it's only for
acceleration that weight at the rims is (nearly) twice as important
on the flat as weight elsewhere.

Ian Jackson said:

In article <[email hidden]>,

Darth. said:

[wants new wheels]

I have roughly the same question. My old rear wheel (came with the
bike, not sure what it was) has had too much abuse - a crash, a thug's
boot, and now my new route to work has unavoidable speed bumps.
The wheel doesn't hold its true any more.

So far I've seen three recommendations all of which are 20-spoke
wheels. Isn't this mad ? Surely the optimum spoke number is greater
than 20.

More rigid rims don't need as many spokes, but I suspect there's an
element of fashion too.

Quoted message said:

I tried to find what the rim weight was of a Mavic Aksium so I could
compare it to separately-marketed rims but without success.

Well if you ask me things like Aksiums (and Ksyriums) are not great
value for money.

Wiggle have a pair of Aksiums for £143. Total weight 1855g.

Or, you could get two Mavic CXP23 rims for £50 altogether and two Campag
Veloce hubs (or your favourite Shimano equivalent) for another £50. You
should have a bit of change left over for linseed oil from your total
£143 budget after getting 64 quality stainless butted spokes. Total
weight 1921g.

Difference in weight of 66g. If that bothers you, use 28H instead of 32H
and leave the dustcaps off-- that should make up the difference and
you'll still have more spokes.

I would much rather have pukka Campag or Shimano hubs than those Mavic
things on the Aksium. Plus you can re-use them (and the spokes) when the
rim wears out.

You will also have a very durable set of wheels, suitable for commuting
over Belgian pavé:

http://www.cervelo.com/wallpaper/1/w037_2560ws.jpg

Membrane said:

Ian Jackson said:

I calculate
that accelerating from 0-36kph is equivalent in energy to a 5m height
increase

Negotiating traffic lights does not necessarily result in loss of
mechanical energy. A proficient cyclist will stop pedalling in advance
of a red light, slow down without using the brakes and will often be
able to time his arrival at a light with it changing to green,
particularly on a commute where you get to know the timing of the
lights on your route.

Nice idea, but not practical in central London, IME. There's just far too
many traffic lights, close together, and on red for a long time*. You'd
have to be dawdling along at 1 mph a lot of the time to avoid stopping (if
you want to be legal). I'd rather just go up to the lights and have a
break.

Anyway a lot of acceleration and deceleration is involved on congested city
roads if you want to be quick but safe. The fast-but-steady urban cyclists
I see take too many risks for my liking.

* Thanks to Red Light Ken Livingstone.

~PB

Ben C said:

Well if you ask me things like Aksiums (and Ksyriums) are not great
value for money.

Wiggle have a pair of Aksiums for £143. Total weight 1855g.

2006 Aksiums: £105 for a Shimano compatible set (£100 for Campag) @
Chainreaction

--
Membrane

in message <[email hidden]>, Ian Jackson

(') said:

In article
<[email hidden]>,

Darth. said:

[wants new wheels]

I have roughly the same question. My old rear wheel (came with the
bike, not sure what it was) has had too much abuse - a crash, a thug's
boot, and now my new route to work has unavoidable speed bumps.
The wheel doesn't hold its true any more.

So far I've seen three recommendations all of which are 20-spoke
wheels. Isn't this mad ? Surely the optimum spoke number is greater
than 20.

I don't think it's mad. A wheel is a system. Modern factory manufactured
designer wheels are designed as a single system, without compromises, and
the good ones are extremely good. That isn't to say that if you built a
wheel with a conventional rim and hub, and only 18 spokes, it would
automatically be a strong wheel (although I've seen Graeme Obree riding a
pair of wheels built like that). But yes, I'd back any factory-made Mavic
wheel to be stronger than than a conventionally built no-name wheel with
twice the number of spokes, and I'd guess that that applies to at least a
few other brands, too.

I'd still expect a hand-built wheel from a good wheel builder to be at
least as strong, though; the Mavic wheels are not magic.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; I'd rather live in sybar-space

in message <[email hidden]>, Membrane

(') said:

If so, a 300g weight difference between a set of Aksiums and a set of
Ksyriums translates in 600g dead weight. At a bike weight of 8kg and a
rider weight of 75kg this equates to 0.36%. The price difference between
a set of Aksiums and Ksyriums is what, £200? Lotta money to pay for a
0.36% advantage (on a commuter bike).

Just out of interest, I worked it out:

Front Rear Total Price Saving £/g
(pair) grammes
Aksium 870 985 1855 £128
Ksyrium Equipe 810 960 1770 £216 -85 -1.04
Ksyrium Elite 770 920 1690 £335 -165 -1.25
Ksyrium SL 645 840 1485 £522 -370 -1.06
Ksyrium SLP 645 835 1480 £612 -375 -1.29

So you pay around £1.10p per gramme saved.

Looking at other relatively heavy parts of the bike, that's not a bad rate;
for example if you look at chainsets:

Campagnolo Xenon Ultra-Torque 768 grammes, £55
Campagnolo Record Carbon Ultra Torque 643 grammes, £400

which is about £2/gramme.

I'm a bit skeptical of the idea that weight saving on the wheel rims should
be valued higher than on other parts of the bike - that's true only under
hard acceleration, which isn't a significant component of a typical race
let alone a typical leisure ride - but nevertheless you seem to get more
saving for your spondulics on wheels.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

Error 1109: There is no message for this error

Simon Brooke said:

Just out of interest, I worked it out:

Front Rear Total Price Saving £/g
(pair) grammes
Aksium 870 985 1855 £128
Ksyrium Equipe 810 960 1770 £216 -85 -1.04
Ksyrium Elite 770 920 1690 £335 -165 -1.25
Ksyrium SL 645 840 1485 £522 -370 -1.06
Ksyrium SLP 645 835 1480 £612 -375 -1.29

Interesting. I always imagined that the lighter components get, the more
you pay per gram of weight saved. Your calculation shows that at least
for this Mavic wheels example this isn't really the case.

Quoted message said:

So you pay around £1.10p per gramme saved.

It still seems like a heck of a lot of money to me. Despite your
calculation example suggesting otherwise, I can't help believing that
there is sort of a "sweet spot" in a price vs bike weight graph (total
bike weight). A knee-joint type spot in the graph so to speak.

--
Membrane

In article <[email hidden]>, Ben C
[email hidden] says...

Quoted message said:

I would much rather have pukka Campag or Shimano hubs than those Mavic
things on the Aksium. Plus you can re-use them (and the spokes) when the
rim wears out.

What's wrong with Mavic hubs? They always used to be better than
Shimano. And I thought you could just send Mavic wheels to their
service centre to have them rebuilt.

Rob Morley said:

In article <[email hidden]>, Ben C
[email hidden] says...

Quoted message said:

I would much rather have pukka Campag or Shimano hubs than those Mavic
things on the Aksium. Plus you can re-use them (and the spokes) when the
rim wears out.

What's wrong with Mavic hubs?

I'm going on this:

http://groups.google.co.uk/group/rec.bicycles.tech/msg/65878ede82ab9336

which is from a very respected poster who works in (possibly owns) a
bike shop.

Quoted message said:

They always used to be better than Shimano.

Well I don't know, but Shimano hubs these days (apart from perhaps the
very cheap ones) are beautifully made and last a long time. Same goes
for Campag. The Mavic ones are at best an unknown.

Another consideration is that the Aksium is about Mavic's most budget
"wheel system", but the alternative traditional wheels you can build up
for around that price are using either known good Shimano stuff well up
into the range or Campag Veloce.

In article <[email hidden]>, Ben C
[email hidden] says...

Quoted message said:

On 2007-11-18, Rob Morley <[email hidden]> wrote:

Quoted message said:

Quoted message said:

What's wrong with Mavic hubs?

I'm going on this:

http://groups.google.co.uk/group/rec.bicycles.tech/msg/65878ede82ab9336

which is from a very respected poster who works in (possibly owns) a
bike shop.

Fair enough - my Mavic hubs don't have a freehub, or any plastic parts.

Quoted message said:

Quoted message said:

They always used to be better than Shimano.

Well I don't know, but Shimano hubs these days (apart from perhaps the
very cheap ones) are beautifully made and last a long time. Same goes
for Campag. The Mavic ones are at best an unknown.

My bad experience of Shimano hubs is limited to an Ultegra front that
ate cones. The replacement hub (NOS Ultegra) seems to be OK so far and
the rear hasn't been a problem - maybe there was a bad batch.

Quoted message said:

Another consideration is that the Aksium is about Mavic's most budget
"wheel system", but the alternative traditional wheels you can build up
for around that price are using either known good Shimano stuff well up
into the range or Campag Veloce.

I'd be unlikely to buy weird Mavic wheels anyway, being a bit of a
traditionalist, but I wouldn't have doubted their quality until now.

in message <[email hidden]>, Membrane

(') said:

Simon Brooke said:

Just out of interest, I worked it out:

Front Rear Total Price Saving £/g
(pair) grammes
Aksium 870 985 1855 £128
Ksyrium Equipe 810 960 1770 £216 -85 -1.04
Ksyrium Elite 770 920 1690 £335 -165 -1.25
Ksyrium SL 645 840 1485 £522 -370 -1.06
Ksyrium SLP 645 835 1480 £612 -375 -1.29

Interesting. I always imagined that the lighter components get, the more
you pay per gram of weight saved. Your calculation shows that at least
for this Mavic wheels example this isn't really the case.

Quoted message said:

So you pay around £1.10p per gramme saved.

It still seems like a heck of a lot of money to me. Despite your
calculation example suggesting otherwise, I can't help believing that
there is sort of a "sweet spot" in a price vs bike weight graph (total
bike weight). A knee-joint type spot in the graph so to speak.

I suspect there is, but I suspect it's below the base point of designer
wheels. Ordinary factory-built conventional wheels from the far east
are 'good enough' for most purposes. What you're getting with designer
wheels is very small improvements in bearings, weight, and aerodynamics.
Is it worth it? that's a very subjective judgement. For me it is.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; may contain traces of nuts, bolts or washers.