Newbie Q: Wheels?

Oh and just to add. It's dual suspension. I was hoping for a hardtail for
pannier racks but beggers can't be choosers!

Al

"justAL" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Hey folks,

I've picked up a bike off a mate at work that was cheap so I can commute
into work. This allows me to turn my motorbike into a weekend toy and
become alot more fit.

It's a mountain bike of some sort and quite frankly on the cheap side of
things. The front wheel is out of whack and I was wondering where I might
find a 2nd hand 26" rim to replace it that would also have the provision
for a front brake disc?

If anyone can help me out that would be much appreciated.

I'm in Melbourne BTW.

Cheers,
Al

justAL said:

It's a mountain bike of some sort and quite frankly on the cheap side of
things. The front wheel is out of whack and I was wondering where I might
find a 2nd hand 26" rim to replace it that would also have the provision for
a front brake disc?

If the bike already has a disc on there, you can probably repair the
existing wheel by truing the spokes. There's some good info at
http://sheldonbrown.com/wheelbuild.html . Total cost is an appropriate
decent spoke key, or about $10.

If it's beyond fixing, but the hub is decent, you might be able to put a
new rim on it. You'll need the rim and a spoke key, and a couple of hours.
If you look around you might be able to find someone clearing out old rims
for under $50, but you're probably looking at $70-80 as a minimum.

Steer clear of K-mart stuff as replacements. It's cheap, but it's cheap.
If you let us know where you are, I'm sure someone can point you to a
decent LBS (local bike shop) who can help you.

Other spots to try are ebay, farkin.net and 26inches.com. There are
generally a few wheels going as people upgrade, or want $$$ for new toys.

--
Dave Hughes | [email hidden]
"Soon we will be able to harness the rotational energy from Orwell's
grave to solve all world energy problems" - GigsVT

Ahhh another one comes over from the dark side... Welcome ;-)

justAL said:

Hey folks,

I've picked up a bike off a mate at work that was cheap so I can commute
into work. This allows me to turn my motorbike into a weekend toy and
become alot more fit.

It's a mountain bike of some sort and quite frankly on the cheap side of
things. The front wheel is out of whack and I was wondering where I might
find a 2nd hand 26" rim to replace it that would also have the provision for
a front brake disc?

If anyone can help me out that would be much appreciated.

I'm in Melbourne BTW.

Cheers,
Al

Hey Dave,

Top stuff! It's a start.
I'm in Cranbourne North.

Al

"Random Data" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

justAL said:

It's a mountain bike of some sort and quite frankly on the cheap side of
things. The front wheel is out of whack and I was wondering where I
might
find a 2nd hand 26" rim to replace it that would also have the provision
for
a front brake disc?

If the bike already has a disc on there, you can probably repair the
existing wheel by truing the spokes. There's some good info at
http://sheldonbrown.com/wheelbuild.html . Total cost is an appropriate
decent spoke key, or about $10.

If it's beyond fixing, but the hub is decent, you might be able to put a
new rim on it. You'll need the rim and a spoke key, and a couple of hours.
If you look around you might be able to find someone clearing out old rims
for under $50, but you're probably looking at $70-80 as a minimum.

Steer clear of K-mart stuff as replacements. It's cheap, but it's cheap.
If you let us know where you are, I'm sure someone can point you to a
decent LBS (local bike shop) who can help you.

Other spots to try are ebay, farkin.net and 26inches.com. There are
generally a few wheels going as people upgrade, or want $$$ for new toys.

--
Dave Hughes | [email hidden]
"Soon we will be able to harness the rotational energy from Orwell's
grave to solve all world energy problems" - GigsVT

Hey Jules,

I don't feel so alone now :P

Al

"Jules" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Ahhh another one comes over from the dark side... Welcome ;-)

justAL said:

Hey folks,

I've picked up a bike off a mate at work that was cheap so I can commute
into work. This allows me to turn my motorbike into a weekend toy and
become alot more fit.

It's a mountain bike of some sort and quite frankly on the cheap side of
things. The front wheel is out of whack and I was wondering where I
might find a 2nd hand 26" rim to replace it that would also have the
provision for a front brake disc?

If anyone can help me out that would be much appreciated.

I'm in Melbourne BTW.

Cheers,
Al

justAL said:

Hey folks,

I've picked up a bike off a mate at work that was cheap so I can commute
into work. This allows me to turn my motorbike into a weekend toy and
become alot more fit.

It's a mountain bike of some sort and quite frankly on the cheap side of
things. The front wheel is out of whack and I was wondering where I might
find a 2nd hand 26" rim to replace it that would also have the provision for
a front brake disc?

Be aware that a wheel that's not made for disk brakes is likely to be a
disaster waiting to happen (not the rim, the rim's irrelevant to the
equation, mostly), but since you'll be swapping the hub anyway
(presumably?) then this isn't an issue as long as the wheel's built to
handle disk forces.

Disk brakes mean lots more stress on spokes.

In aus.bicycle on 14 May 2006 07:01:22 -0700

Bleve said:

Disk brakes mean lots more stress on spokes.

So it's the spokes not the rim that need to be upgraded for disk
brakes?

I'm getting new spokes to go with the disk brake dynamo hub anyway,
but was going to get it built in to my current Alex rim.

Zebee

Zebee Johnstone said:

In aus.bicycle on 14 May 2006 07:01:22 -0700

Bleve said:

Disk brakes mean lots more stress on spokes.

So it's the spokes not the rim that need to be upgraded for disk
brakes?

That's my understanding. I'm not a guru of diskbrake wheels though 🙂

I understood that disc-specific wheels only differed from
'conventional' in having a disk-compatible hub and perhaps a rim with
no braking surface.

Donga

Theo Bekkers said:

"Bleve" wrote

Quoted message said:

Be aware that a wheel that's not made for disk brakes is likely to

be a

Quoted message said:

disaster waiting to happen (not the rim, the rim's irrelevant to the
equation, mostly), but since you'll be swapping the hub anyway
(presumably?) then this isn't an issue as long as the wheel's built

to

Quoted message said:

handle disk forces.

Disk brakes mean lots more stress on spokes.

Given the same stopping force (just short of going over the bars),
please explain why or how the force on the spokes would be different?
Disc brakes will [censored] he hub, rim brakes the rim. I can't see how
this will put more or less stress on the spokes.

Think about it .. rim brakes, the braking force is retarding the rim
directly. Disk brakes - the braking force is retarding the hub, which
is connected to the rim by?

The amount of force brakes can generate is far greater than the force
you can generate pedaling too.

justAL said:

Hey folks,

I've picked up a bike off a mate at work that was cheap so I can commute
into work. This allows me to turn my motorbike into a weekend toy and
become alot more fit.

It's a mountain bike of some sort and quite frankly on the cheap side of
things. The front wheel is out of whack and I was wondering where I might
find a 2nd hand 26" rim to replace it that would also have the provision for
a front brake disc?

If anyone can help me out that would be much appreciated.

I'm in Melbourne BTW.

Cheers,
Al

Welcome Al,

Don't bother upgrading your current bike. Just fix it enough to be safe & ride the life out of it. Once you've ridden this bike into the ground you'll know what type of replacement you'll need. You may even discover that you want a weekend bike and a commuter bike. 🙂

Quoted message said:

Given the same stopping force (just short of going over the bars),
please explain why or how the force on the spokes would be different?
Disc brakes will [censored] he hub, rim brakes the rim. I can't see how
this will put more or less stress on the spokes.

Well, you woudn't radially lace the drive side of a rear wheel would
you? Lack of a crossed spoke pattern means you don't have any
tangential spokes to transmit the drive torque effectively.

Likewise, if you are braking at the hub with a disc, then you are
imparting a torque, albeit in the other direction, which must be
transmitted through the spokes to the rim, tyres, and then ground in
order to slow down.

"Bleve" wrote

Quoted message said:

Theo Bekkers wrote:

Quoted message said:

Quoted message said:

Given the same stopping force (just short of going over the bars),
please explain why or how the force on the spokes would be

different?

Quoted message said:

Quoted message said:

Disc brakes will [censored] he hub, rim brakes the rim. I can't see

how

Quoted message said:

Quoted message said:

this will put more or less stress on the spokes.

Quoted message said:

Think about it .. rim brakes, the braking force is retarding the rim
directly. Disk brakes - the braking force is retarding the hub,

which

Quoted message said:

is connected to the rim by?

Spokes. Do I get a star? With rim brakes is the bicycles momentum NOT
being retarded by the spokes?

Theo

"Andrew" wrote

Quoted message said:

Theo wrote

Quoted message said:

Given the same stopping force (just short of going over the bars),
please explain why or how the force on the spokes would be

different?

Quoted message said:

Quoted message said:

Disc brakes will [censored] he hub, rim brakes the rim. I can't see

how

Quoted message said:

Quoted message said:

this will put more or less stress on the spokes.

Well, you woudn't radially lace the drive side of a rear wheel would
you? Lack of a crossed spoke pattern means you don't have any
tangential spokes to transmit the drive torque effectively.

Quoted message said:

Likewise, if you are braking at the hub with a disc, then you are
imparting a torque, albeit in the other direction, which must be
transmitted through the spokes to the rim, tyres, and then ground in
order to slow down.

I think you are making my point. Braking force must be tranmitted
through the spokes, no matter what kind of brakes you have.

Theo

Quoted message said:

I think you are making my point. Braking force must be tranmitted
through the spokes, no matter what kind of brakes you have.

If that's true, then motive force must also be transmitted via the
spokes, whether you have a chain on a cog, or a small wheel contacting
the road wheel.

Why then is radial lacing rarely used in rear wheels, and even less
common on drive side rear?

If you take a wheel that's radially spoked with low tension and the rim
is held firmly, it's fairly easy to rotate the hub wrt to the rim, as
radial lacing can't transmit torque very well. If it was laced 3 or 4x,
with the same low tension, it's much harder to rotate the hub wrt to
the rim due to the tangential spokes.

So if you jam on a disc brake on an radially laced wheel, the hub will
be rotated slightly CCW compared to the wheel due to the poor torque
transfer. If you jam on a rim brake you're transmitting torque from the
rim, across the bead/rim interface and then from the tyre to the
ground, so the spokes aren't involved in torque transfer, except to
support the wheel.

Have I made a fundamental error here?

AB.

Theo Bekkers said:

Quoted message said:

Think about it .. rim brakes, the braking force is retarding the rim
directly. Disk brakes - the braking force is retarding the hub,

which

Quoted message said:

is connected to the rim by?

Spokes. Do I get a star? With rim brakes is the bicycles momentum NOT
being retarded by the spokes?

Ah, yes, but -- as I understand it -- with disc brakes, you have to
apply the force to the hub, which then gets transmitted down to the
rims, which is where the primary stopping force is applied. Then you've
got the force being transmitted back up through the spokes to the hub,
and from there to the rest of the bike.

Think of it as somebody pushing you from the front, whilst somebody else
pushes you from the back. The net force might be close to zero, but
you're still being squished rather severely.

As I said -- this is all my understanding, and is very much off the top
of my head. Take with an entire ocean's worth of salt.

--
My Usenet From: address now expires after two weeks. If you email me, and
the mail bounces, try changing the bit before the "@ to usenet".

"Andrew" wrote

Quoted message said:

If that's true, then motive force must also be transmitted via the
spokes, whether you have a chain on a cog, or a small wheel

contacting

Quoted message said:

the road wheel.

The motive force has to move the mass of the vehicle, most of which is
you. The tyre contact patch has to have force applied to it. How can
that be other than via the spokes?

Quoted message said:

So if you jam on a disc brake on an radially laced wheel, the hub

will

Quoted message said:

be rotated slightly CCW compared to the wheel due to the poor torque
transfer. I

So a brake is a silly thing to have on a front wheel spoked radially?

Quoted message said:

If you jam on a rim brake you're transmitting torque from the
rim, across the bead/rim interface and then from the tyre to the
ground, so the spokes aren't involved in torque transfer, except to
support the wheel.

Have I made a fundamental error here?

I believe so. The mass you are trying to stop is mostly you, and you
are exerting a force which can only be counteracted by means of the
spokes. (unless you hit a wall).

Theo

"Stuart Lamble" wrote

Quoted message said:

Theo Bekkers wrote:

Quoted message said:

Quoted message said:

Spokes. Do I get a star? With rim brakes is the bicycles momentum

NOT

Quoted message said:

Quoted message said:

being retarded by the spokes?

Quoted message said:

Ah, yes, but -- as I understand it -- with disc brakes, you have to
apply the force to the hub, which then gets transmitted down to the
rims, which is where the primary stopping force is applied. Then

you've

Quoted message said:

got the force being transmitted back up through the spokes to the

hub,

Quoted message said:

and from there to the rest of the bike.

You think the force goes both ways through the spokes? I take it then
there is a special lacing for kids bikes with back-pedal brakes, which
should exert the same forces as disc brakes.

Theo

Quoted message said:

So a brake is a silly thing to have on a front wheel spoked radially?

A disc brake, yes. Not a rim brake.

Quoted message said:

I believe so. The mass you are trying to stop is mostly you, and you
are exerting a force which can only be counteracted by means of the
spokes. (unless you hit a wall).

The spokes are bearing mass of the bike and rider, but it's the
drive/brake torque that we're debating here, and how radial versus
cross lacing is able to transmit this.

Quoted message said:

You think the force goes both ways through the spokes? I take it then
there is a special lacing for kids bikes with back-pedal brakes, which
should exert the same forces as disc brakes.

They're cross laced. Just like all sensible wheels. With tangential
spokes in both directions to transmit torque effectively in both
directions, be it acceleration or braking. For the purposes of this
discussion, disc, drum and coaster brakes are in one camp, canti, v,
caliper in another.

Here's what I've been trying to explain, but clearer, from
http://www.geocities.com/spokeanwheel/lacinggw.htm:
------
One thing every wheel builder needs to know is that drive and hub
braked wheels cannot be fully radially laced. It would work, but it
puts the spokes and the hubs under a high stress situation that
shortens spoke life and could cause the spokes to 'pull out' of (tear
through) the hub. Drive wheels will turn out to be 'spongy' under
power, that is the wheel would have wind up and will not transmit drive
torque efficiently. The pedals would feel as though they were a big
rubber sponge. The wind up will be the worst under high power
situations like sprints, starts and hill climbs. A wheel with the
braking at the hub will also suffer from wind up during braking, and
the harder you applied the brake the worse the effect will become.
During braking the wind up could cause brake modulation, and under
really hard braking the modulation could cause the wheel to
unexpectedly lock up.

In a cross laced pattern on a rear wheel there are 'push' spokes and
'pull' spokes. The 'pull' spokes are the spokes that transfer all the
drive power. The power that enters the hub increases the tension at the
hub end of the spoke. The spoke then transfers this tension to the rim.
Since the rim isn't attached to the ground the rim starts turning. This
all happens instantaneously. The 'push' spokes don't really push, but
their build tension is reduced from the reaction to the increase of the
tension on the 'pull' spokes (every action has an equal an opposite
reaction law of physics). A hub braked wheel has the same principle,
only the direction of the force on the spoke is reversed, it's
traveling from the rim to the hub.

If you fully radially laced a rear or hub braked wheel, there would be
no 'pull' spokes. The torque forces at the hub and rim would cause the
hub to turn in relation to the rim. The spokes will turn at the hub and
pivot on the rim until the force of the increased spoke tension equals
the force of the torque being transferred. The harder you pedal or
brake the more the spokes will stretch. A cross lacing doesn't have
this stretch problem because of the triangular shape of the force
vectors acting on the spoke
--------

Where's Jobst when you need him...?