Disc Compatible Hubs

Burning_Ranger [email hidden] opined the following...

Quoted message said:

I've ordered a bike without disc brakes (forks are disc compatible), gonna
come tomorrow. What I want to know is it possible to use disc brakes by
simply replacing out the old hub with a disc hub? I realise the wheels will
have to be re-built, will a LBS do this for me and how much is it likely to
cost?

It'd probably be worth having your LBS "face" the disc mounts (Grind
them so they are perfectly perpendicular to the hub axis) before fitting
discs if none have been fitted before. If they are fitting the discs
they probably ought to do it by default.

Other than that, it's just a case of new wheels. Costs seem to vary
dramatically depending on your LBS. If you have a choice, it's probably
worth asking around to see who builds good wheels locally (Or learn.
That way it's your fault!).

Jon

Jon Senior said:

Burning_Ranger [email hidden] opined the following...

Quoted message said:

I've ordered a bike without disc brakes (forks are disc compatible),
gonna come tomorrow. What I want to know is it possible to use disc
brakes by simply replacing out the old hub with a disc hub? I
realise the wheels will have to be re-built, will a LBS do this for
me and how much is it likely to cost?

It'd probably be worth having your LBS "face" the disc mounts (Grind
them so they are perfectly perpendicular to the hub axis) before
fitting discs if none have been fitted before. If they are fitting
the discs they probably ought to do it by default.

Other than that, it's just a case of new wheels. Costs seem to vary
dramatically depending on your LBS. If you have a choice, it's
probably worth asking around to see who builds good wheels locally
(Or learn. That way it's your fault!).

Perhaps I wasn't clear; What I'm asking is can you re-use the old spokes and
rims with the newly bought disc hub?

I've looked at disc wheels and they seem to cost £50+ for each wheel. I can
just afford front and rear hydraulic brakes (in a month or two) for £130-140
but another £100 for wheels is too much.

--

Burning_Ranger

To email: [email hidden]

Burning_Ranger said:

I've ordered a bike without disc brakes (forks are disc compatible),
gonna come tomorrow. What I want to know is it possible to use disc
brakes by simply replacing out the old hub with a disc hub? I realise
the wheels will have to be re-built, will a LBS do this for me and
how much is it likely to cost?

Do you *need* disc brakes? My understanding is that because the front wheel
needs to be dished for the disc to fit, it's not as strong.

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

Quoted message said:

Perhaps I wasn't clear; What I'm asking is can you re-use the old spokes

and

Quoted message said:

rims with the newly bought disc hub?

You can use the old rims, obviously make sure the spoke count is the same
(usually 32 for XC 36 for DH or heavier folks).
It's unlikely you'll be able to use all the spokes, if any, as the spoke
flanges of disc hub can be of different diameters on each side so at best
only half will fit.
As Jon Senior has said one way to save money is to re-build the wheels
yourself, not that difficult just requiring time and patience.

http://www.dtswiss.com/index.asp?fuseaction=news.bike&id=31

www.hopetech.com

http://www.sheldonbrown.com/wheelbuild.html

http://www.parktool.com/repair_help/howfix_truing.shtml

Regards,
Pete

Doki [email hidden] opined the following...

Quoted message said:

Do you *need* disc brakes? My understanding is that because the front wheel
needs to be dished for the disc to fit, it's not as strong.

Simple test. Ride bike on whatever surface you'll normally be cycling.
Wear a stack of protective clothing (Dress like the Michelin Man).
Attempt to lock wheels. If you can, then you have little need for
stronger brakes. The only other reason I can think of is for
circumstances where there will be prolonged braking which might put the
tyre at risk of overheating (Alpine descent?).

Jon

Jon Senior said:

Simple test. Ride bike on whatever surface you'll normally be cycling.
Wear a stack of protective clothing (Dress like the Michelin Man).
Attempt to lock wheels. If you can, then you have little need for
stronger brakes. The only other reason I can think of is for
circumstances where there will be prolonged braking which might put the
tyre at risk of overheating (Alpine descent?).

The reason for disc brakes is not stopping power - any decent brake will
lock the wheels especially on loose surfaces. Its the control of that
power - the so called modulation - which is a lot lot better on good
discs than any rim brake plus the relative immunity from mud and wet.

Tony

in message <[email hidden]>,

Burning_Ranger (') said:

I've ordered a bike without disc brakes (forks are disc compatible),
gonna come tomorrow. What I want to know is it possible to use disc
brakes by simply replacing out the old hub with a disc hub?

Yes.

Quoted message said:

I realise
the wheels will have to be re-built, will a LBS do this for me and how
much is it likely to cost?

With a bit of patience and care you can easily rebuild your wheels
yourself. The only tool you need is a spoke key. Instructions here:
<URL:http://www.sheldonbrown.com/wheelbuild.html>

A wheel takes around about an hour to build for someone who knows what
they are doing, so expect to pay whatever your LBS charges for an
hour's workshop time. Up to £30 per wheel is reasonable. Of course, if
your new hubs have a different diameter to your old ones you will need
new spokes as well. There's a spoke length calculator here:
<URL:http://www.sheldonbrown.com/rinard/spocalc.htm> (get the full
version, not the 'express' one).

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

;; MS Windows: A thirty-two bit extension ... to a sixteen bit
;; patch to an eight bit operating system originally coded for a
;; four bit microprocessor and sold by a two-bit company that
;; can't stand one bit of competition -- anonymous

in message <[email hidden]>, Tony Raven

(') said:

Jon Senior said:

Simple test. Ride bike on whatever surface you'll normally be
cycling. Wear a stack of protective clothing (Dress like the Michelin
Man). Attempt to lock wheels. If you can, then you have little need
for stronger brakes. The only other reason I can think of is for
circumstances where there will be prolonged braking which might put
the tyre at risk of overheating (Alpine descent?).

The reason for disc brakes is not stopping power - any decent brake
will
lock the wheels especially on loose surfaces. Its the control of that
power - the so called modulation - which is a lot lot better on good
discs than any rim brake plus the relative immunity from mud and wet.

I think this is also a matter of hydraulic versus cable. Cable operated
brakes suffer from more hysteresis and drag in the system, which
hampers modulation. So in my opinion and experience it is hydraulic
brakes (irrespective of rim or disk) which offer better modulation, and
disk brakes (irrespective of cable or hydraulic) which offer relative
immunity to mud and wet. Obviously, with hydraulic disk brakes you get
better modulation _and_ better wet weather performance, but at a cost
in weight and relative lateral weakness of the wheel (and also, of
course, loadsamoney).

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

to err is human, to lisp divine
;; attributed to Kim Philby, oddly enough.

Simon Brooke wrote:

Ta everyone.

--

Burning_Ranger

To email: [email hidden]

Simon Brooke said:

Obviously, with hydraulic disk brakes you get
better modulation _and_ better wet weather performance, but at a cost
in weight and relative lateral weakness of the wheel (and also, of
course, loadsamoney).

I've yet to see any evidence of the supposed lateral weakness of the
wheel. Disc brakes are used in the more extreme forms of mountain
biking where other brake systems rarely go and yet lateral weakness does
not seem to be a weakness.

Tony

"Jon Senior" <jon_AT_restlesslemon_DOTco_DOT_uk> wrote in message
news:[email hidden]...

Quoted message said:

Doki [email hidden] opined the following...

Quoted message said:

Do you *need* disc brakes? My understanding is that because the front

wheel

Quoted message said:

Quoted message said:

needs to be dished for the disc to fit, it's not as strong.

Simple test. Ride bike on whatever surface you'll normally be cycling.
Wear a stack of protective clothing (Dress like the Michelin Man).
Attempt to lock wheels. If you can, then you have little need for
stronger brakes.

Wrong!!!
I was riding on wet grass off-road in the Peak District yesterday. My disc
brakes very easily caused the wheels to lock and tyres to slide as would
even mediocre cable rim brakes eventually.
But it was less of a problem than with v-brakes because the discs worked
more or less immediately and with good modulation. In the same conditions
cable rim brakes would not have been immediately effective and then would
have provided sketchy feedback
I'm fully converted to hydraulic discs and accept the cost, small extra
weight and regular checking of the front skewer as a small price. In the
wrong conditions they're an expensive toy, in the right conditions a real
riding pleasure enhancement.

Regards,
Pete

Jon Senior jon_AT_restlesslemon_DOTco_DOT_uk said:

Doki [email hidden] opined the following...

Quoted message said:

Do you *need* disc brakes? My understanding is that because the front wheel
needs to be dished for the disc to fit, it's not as strong.

Simple test. Ride bike on whatever surface you'll normally be cycling.
Wear a stack of protective clothing (Dress like the Michelin Man).
Attempt to lock wheels. If you can, then you have little need for
stronger brakes. The only other reason I can think of is for
circumstances where there will be prolonged braking which might put the
tyre at risk of overheating (Alpine descent?).

There was a lovely smell of very hot metal coming from the front of my
bike coming at the bottom of 250m of (slow (I was aiming not to come
off, and it was most steep)) descent on rocky ground this morning
which I believe indicates I was better off with discs. In England. In
a similar situation in Norway, albeit with 600m of descent, and I melted
my brake blocks and got cramp in my hands.

With the disc, I think it made things easier.

N.B. This was transport cycling, albeit from a rather remote
location. And there was an alternative road route, but as that would
involve a 1 in 5 hill on a single track road, I'd still need the brake
performance.

A

Peter B [email hidden] opined the following...

Quoted message said:

Wrong!!!

Right actually, although I forgot about modulation. Put simply, if you
are capable of locking the wheels of your bike with your current brakes,
then they _are_ strong enough.

Quoted message said:

I was riding on wet grass off-road in the Peak District yesterday. My disc
brakes very easily caused the wheels to lock and tyres to slide as would
even mediocre cable rim brakes eventually.
But it was less of a problem than with v-brakes because the discs worked
more or less immediately and with good modulation. In the same conditions
cable rim brakes would not have been immediately effective and then would
have provided sketchy feedback
I'm fully converted to hydraulic discs and accept the cost, small extra
weight and regular checking of the front skewer as a small price. In the
wrong conditions they're an expensive toy, in the right conditions a real
riding pleasure enhancement.

As Simon mentioned, the modulation is a consequence of the hydraulics,
not the disc. Hydraulic rim brakes are also bery good (apparently) while
cable operated disc brakes are no better than (Or possibly worse than)
V-types / DPs.

An observation of mine (Please could someone correct me if I'm wrong
here) is that rim brakes will have a better braking power for the same
force on a larger rim than a smaller one. This comes from my trying to
work out why it is that I can't get anywhere near the stopping power
that I would like on the bent despite having a pair of (reasonably) well
set up V brakes. If there was the possibility of fitting discs, I'd do
so, but that'd require a new fork (Or worse, my welding a home made disc
mount onto the existing forks... that would probably count as dicing
with death.

Jon

"Jon Senior" <jon_AT_restlesslemon_DOTco_DOT_uk> wrote in message
news:[email hidden]...

Quoted message said:

Peter B [email hidden] opined the following...

Quoted message said:

Wrong!!!

Right actually, although I forgot about modulation. Put simply, if you
are capable of locking the wheels of your bike with your current brakes,
then they _are_ strong enough.

Sorry Jon, the point is ultimate stopping power isn't the be-all end-all.
In wet and/or muddy conditions both cable rim brakes and hydraulic discs may
be capable of locking up the wheels but in my very practical experience the
hydraulic discs will do so sooner, more reliably and with less effort.
Apply this to several long, wet and gritty descents and the ease and
reliability of the discs overwhelms cable rim brakes.
I say this with some14 years experience of using canti and linear pull
brakes in these conditions and 8 months of hydraulic discs.
(And it's easier to replace disc pads than canti/vee pads and rims).

Regards,
Pete

Peter B [email hidden] opined the following...

Quoted message said:

"Jon Senior" <jon_AT_restlesslemon_DOTco_DOT_uk> wrote in message
news:[email hidden]...

Quoted message said:

Peter B [email hidden] opined the following...

Quoted message said:

Wrong!!!

Right actually, although I forgot about modulation. Put simply, if you
are capable of locking the wheels of your bike with your current brakes,
then they _are_ strong enough.

Sorry Jon, the point is ultimate stopping power isn't the be-all end-all.

I know. Hence the mention of modulation and the comments about the
difference between hydraulic and cable brakes.

Quoted message said:

In wet and/or muddy conditions both cable rim brakes and hydraulic discs may
be capable of locking up the wheels but in my very practical experience the
hydraulic discs will do so sooner, more reliably and with less effort.
Apply this to several long, wet and gritty descents and the ease and
reliability of the discs overwhelms cable rim brakes.

Again. You're comparing a hydraulic system with a cable system.

Quoted message said:

I say this with some14 years experience of using canti and linear pull
brakes in these conditions and 8 months of hydraulic discs.
(And it's easier to replace disc pads than canti/vee pads and rims).

I haven't disputed any of this. The key point is that unless you are
suffering from melted brake pads or exploding tyres then a disc brake is
not the be-all and end-all of braking. A hydraulic rim brake will
provide a significant improvement over cable-operated rim brakes.

I say this with some 16 years of experience of a multitude of cable-
operated braking systems including single-pivot, centre-pull, dual-
pivot, V-brakes and discs. A cheap cable operated disc brake is nothing
compared to a similarly cheap (Proportionally to the higher spec models)
V-brake.

The smaller diameter of the braking surface requires a greater force to
be exerted. With cables this force is (or appears to be) in the order of
the force required to stretch the cable. I _cannot_ lock the back wheel
of the bent with my cable disc brake. I have little doubt that
replacement with a hydraulic disc would solve this, but also have little
doubt that replacement with a good cable / hydraulic rim brake would
also.

With regard to modulation, I've heard much talk about it, but sadly the
only hydraulic braked bike that I've ridden for long enough to evaluate
the braking quality had not been configured properly so one of the pads
rubbed at the front. I imagine that the inherent lack of energy loss in
the system should help greatly.

I'm not criticising disc brakes (hydraulic or otherwise) or claiming
that locking your wheels is the only thing that brakes need to be able
to do so please stop looking for an argument where none is to be found.

Out of interest, what disc brakes do you use?

Jon

Jon Senior said:

An observation of mine (Please could someone correct me if I'm wrong
here) is that rim brakes will have a better braking power for the same
force on a larger rim than a smaller one.

Ok, you're wrong. At least, there is in theory a minuscule effect due to
the diferent ratio of rim size to wheel outside diameter, but wheel size
alone is not relevant. The (linear) speed of the rim past the brake is
the same in each case, deceleration = force/mass, power dissipation =
speed X frictional force etc. Wheel size does not come into it (and for
disk brakes it is the ratio of disk to wheel size not the absolute disk
size that matters).

James
--
If I have seen further than others, it is
by treading on the toes of giants.
http://www.ne.jp/asahi/julesandjames/home/

James Annan [email hidden] opined the following...

Quoted message said:

Jon Senior said:

An observation of mine (Please could someone correct me if I'm wrong
here) is that rim brakes will have a better braking power for the same
force on a larger rim than a smaller one.

Ok, you're wrong. At least, there is in theory a minuscule effect due to
the diferent ratio of rim size to wheel outside diameter, but wheel size
alone is not relevant. The (linear) speed of the rim past the brake is
the same in each case,

Why? No. Don't answer that, just worked it out. But you do still have a
leverage advantage with larger wheels. Without doing the maths I
couldn't say how this compares to the larger momentum <correct term?>
caused by the larger rim.

Quoted message said:

deceleration = force/mass, power dissipation =
speed X frictional force etc. Wheel size does not come into it (and for
disk brakes it is the ratio of disk to wheel size not the absolute disk
size that matters).

OK. I may have to break out the back of the envelope for this one... but
not until I've had some sleep. Oh well, something to do on the train to
Glasgow tomorrow morning.

Jon

"Jon Senior" <jon_AT_restlesslemon_DOTco_DOT_uk> wrote in message
news:[email hidden]...

Quoted message said:

James Annan [email hidden] opined the following...

Quoted message said:

Jon Senior said:

An observation of mine (Please could someone correct me if I'm wrong
here) is that rim brakes will have a better braking power for the same
force on a larger rim than a smaller one.

Ok, you're wrong. At least, there is in theory a minuscule effect due to
the diferent ratio of rim size to wheel outside diameter, but wheel size
alone is not relevant. The (linear) speed of the rim past the brake is
the same in each case,

Why? No. Don't answer that, just worked it out. But you do still have a
leverage advantage with larger wheels. Without doing the maths I
couldn't say how this compares to the larger momentum <correct term?>
caused by the larger rim.

Any leverage advantage of the bigger rim is almost exactly cancelled out by
the leverage disadvantage of having the bigger rim (brake to hub leverage vs
hub to ground leverage). No maths required. Momentum is pretty much
irrelevant, being to do with the weight of the wheel.

cheers,
clive

Jon Senior <jon_AT_restlesslemon_DOTco_DOT_uk> wrote in message news:<[email hidden]>...

Quoted message said:

But you do still have a
leverage advantage with larger wheels.

Um...

Quoted message said:

Without doing the maths I
couldn't say how this compares to the larger momentum <correct term?>
caused by the larger rim.

WTF?

James