Help: Fitting Disk Brakes to an older bike

Is it possible to fit front and rear disk brakes to an older bike that
doesn't have the 'native' mounting points? I have a really nice (i.e. super
light), but old, mountain bike that I now use for commuting. It's always
wet here in Vancouver an the rims really take a beating from all the crud.
I'm thinking that if I use disk brakes, I won't have to replace my (rather
expensive) rims as often. I have to change the wheels now, and although I'd
rather not get rid of the nice hubs that I have, now would be the time to
switch to disk brake hubs if that's an option.

Thanks for any advice.

"BlahBlah" wrote in message
...
Is it possible to fit front and rear disk brakes to an older bike that
doesn't have the 'native' mounting points? I have a really nice (i.e.
super light), but old, mountain bike that I now use for commuting. It's
always wet here in Vancouver an the rims really take a beating from all
the crud. I'm thinking that if I use disk brakes, I won't have to replace
my (rather expensive) rims as often. I have to change the wheels now, and
although I'd rather not get rid of the nice hubs that I have, now would be
the time to switch to disk brake hubs if that's an option.

Ceramic coated rims? Ok, they're expensive, but you said your existing ones
were too, so less of a pain. And they do work. Means you keep your nice
hubs, and your nice frame without worrying about brake mounts.

On Sep 15, 7:14*pm, "BlahBlah" wrote:
Is it possible to fit front and rear disk brakes to an older bike that
doesn't have the 'native' mounting points? *I have a really nice (i.e. super
light), but old, mountain bike that I now use for commuting. *It's always
wet here in Vancouver an the rims really take a beating from all the crud..
I'm thinking that if I use disk brakes, I won't have to replace my (rather
expensive) rims as often. *I have to change the wheels now, and although I'd
rather not get rid of the nice hubs that I have, now would be the time to
switch to disk brake hubs if that's an option.


Seeing as you can get a decent rim brake wheelset for $100 US from an
online discounter--why worry? Complement your old bike with a set of
nice light vee brakes and replace the commodity wheels as needed. If
you find a disc fork on sale--you can switch the front to disk at a
later date. If that's the plan--get a disk wheelset with rim braking
surfaces.

For rim brakes, you could get and afford to wear out some LX/Rhynos:

http://www.pricepoint.com/detail/132...-Lite-Rims.htm

or for future front disc, Deore/Rhyno for only a few bucks mo

http://www.pricepoint.com/detail/120...-Lite-Rims.htm

BlahBlah wrote:
Is it possible to fit front and rear disk brakes to an older bike that
doesn't have the 'native' mounting points? I have a really nice (i.e.
super light), but old, mountain bike that I now use for commuting. It's
always wet here in Vancouver an the rims really take a beating from all
the crud. I'm thinking that if I use disk brakes, I won't have to
replace my (rather expensive) rims as often. I have to change the
wheels now, and although I'd rather not get rid of the nice hubs that I
have, now would be the time to switch to disk brake hubs if that's an
option.

If you buy a heavier blade disc fork, sure. Start about $80.

Taking apart a rear end to use heavier disc type stays
and/or new ends is not usually cost effective but it is
technically possible.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

On Sep 15, 7:56*pm, AMuzi wrote:
BlahBlah wrote:
Is it possible to fit front and rear disk brakes to an older bike that
doesn't have the 'native' mounting points? *I have a really nice (i.e..
super light), but old, mountain bike that I now use for commuting. *It's
always wet here in Vancouver an the rims really take a beating from all
the crud. I'm thinking that if I use disk brakes, I won't have to
replace my (rather expensive) rims as often. *I have to change the
wheels now, and although I'd rather not get rid of the nice hubs that I
have, now would be the time to switch to disk brake hubs if that's an
option.

If you buy a heavier blade disc fork, sure. Start about $80.

Taking apart a rear end to use heavier disc type stays
and/or new ends is not usually cost effective but it is
technically possible.

And naturally a stronger mounting point--still, I'd be scared to ride
a "light" frame that had been retrofitted with disc brake mounts. My
minds eye sees the torque used when removing a freewheel using a bench
vise time severalfold. Crrrrunch! You'd probably want a little bracing
between the stays if doing this mind exercise. Ahhh, better.

New cheap rigid fork + cheap n' good brake like a BB5/7 + commodity
wheel(s). $150 American if you shop the blowouts or +100 and labor for
the LBS to do it. If you do the former and aren't a wheel person, at
least pay your LBS $15 to tweak the wheel. It'll be very well
invested.

I'll probably do this to my own utility/everything bike if I find a
disc wheel or hub for cheap or swap with D.'s bucket of bits, as my
fork is disk ready. Converting both ends to disc on a city machine
isn't necessary. Just remember to favor the front brake in slop--a
good practice anyway.

BlahBlah wrote:

Is it possible to fit front and rear disk brakes to an older bike that
doesn't have the 'native' mounting points? *I have a really nice (i.e. super
light), but old, mountain bike that I now use for commuting. *It's always
wet here in Vancouver an the rims really take a beating from all the crud..
I'm thinking that if I use disk brakes, I won't have to replace my (rather
expensive) rims as often. *I have to change the wheels now, and although I'd
rather not get rid of the nice hubs that I have, now would be the time to
switch to disk brake hubs if that's an option.

Drum brake hubs offer better reliability in poor weather, along with
greater resistance to damage and warping, than disc brakes. Consider
using a drum on the rear at least (Sturmey Archer offers a cassette
rear with drum) and either mounting a drum in front or having a
framebuilder modify your fork with a disc brake tab.

Drum brakes are weak when new, but they break in over a surprisingly
long period to become equivalent to good caliper or decent cantilever
brakes.

Chalo

On 09/15/2009 05:14 PM, BlahBlah wrote:
Is it possible to fit front and rear disk brakes to an older bike that
doesn't have the 'native' mounting points? I have a really nice (i.e.
super light), but old, mountain bike that I now use for commuting. It's
always wet here in Vancouver an the rims really take a beating from all
the crud. I'm thinking that if I use disk brakes, I won't have to
replace my (rather expensive) rims as often. I have to change the wheels
now, and although I'd rather not get rid of the nice hubs that I have,
now would be the time to switch to disk brake hubs if that's an option.

Thanks for any advice.

as pointed out by others, the design and tube of the light steel frames
is not appropriate for disk tabs. get a cheapo $99 mtb frame from
nashbar [or equivalent]. it's got tabs and it won't rust. or, as
mentioned by others, use ceramic rims. they are very effective and last
virtually forever.

On 09/15/2009 06:04 PM, Jobst Brandt wrote:
A shy person wrote:

Is it possible to fit front and rear disk brakes to an older bike
that doesn't have the 'native' mounting points? I have a really
nice (i.e. super light), but old, mountain bike that I now use for
commuting. It's always wet here in Vancouver an the rims really
take a beating from all the crud. I'm thinking that if I use disk
brakes, I won't have to replace my (rather expensive) rims as often.
I have to change the wheels now, and although I'd rather not get rid
of the nice hubs that I have, now would be the time to switch to
disk brake hubs if that's an option.

From what you write, I take it this is a typical old bicycle with
road-like fork blares that taper to about 1/2" diameter at the curl to
vertical dropouts. The reason such forks have traditionally tapered
to near nothing is that there is no torque at the fork ends. Even rim
braking loads primarily the steertube that has less (fore and aft)
bending stiffness than the fork blades that have a greater in-line
cross section toward bending.

The curl at the end of the fork is there to achieve proper tail, not
spring cushioning as has often been claimed.

wow. spectacularly wrong. the spring "test" you used to "determine"
this was flawed jobst - use of an elastomeric tape stretched across the
arc remains tight because it is, er, elastic, not because the fork is
not springing. such a fundamental error is just amazing.


Fork blades do not flex
in use or they would soon fail in fatigue.

nope. all things flex when loaded. by definition. and you clearly
haven't a clue about fatigue.


This also applies to
curved seat- and chainstays.

nope. same reasons - they do spring and they don't fatigue.

what did you really study at stanford jobst? it clearly wasn't basic
engineering principles.



So... You'll need a torque strut to the fork crown from the pivoted
brake caliper (a straight rod that attaches between one caliper ear
and the fork crown on shear pins. Preferably the caliper should be
positioned ahead of the fork, so it pulls down on the torque strut and
pushes the front axle up into the dropout instead of trying to
dislodge one end of the axle downward.

The caliper cannot be rigidly attach to the fork or it will break it,
if it is not designed to support fork end torque. The caliper must be
on a swivel pin through one ear and retained against rotation by the
torque strut in the other. Then you'll be in the clear.


utter drivel. fundamental failure to comprehend basics.

And naturally a stronger mounting point--still, I'd be scared to ride
a "light" frame that had been retrofitted with disc brake mounts. My
minds eye sees the torque used when removing a freewheel using a bench
vise time severalfold. Crrrrunch!

You're speaking of the braking forces applied to the retrofitted rear caliper
tabs? A disc brake's torque is all circumferential (direction of rotation).
No lateral (parallel to the axle) force at all.

Rear disc mount tabs on a modern bike's dropout are very modest. Witness:

http://tinypic.com/r/2nbbnfl/3

Note almost no lateral support. None needed.

All braking forces are pressing down against the seat stay. Very simple
design requirements, easily retrofitted by a competent mechanic & welder. A
bit of test-fitting with rotor in place and caliper + mount in-hand is
required.

A basic drawing of the international standard mount is he

http://www.hayesdiscbrake.com/support_downloads.shtml

(Scroll down to the section "Industry Standard Mounts")

You'd probably want a little bracing
between the stays if doing this mind exercise.

???

The OP may want to consider the costs involved. Cheap frames from Nashbar
(under $100) & others make modification of your frame financially inviable
unless it's an emotional-attachment thing.

Hi Fester:

Thanks for your note.

I was looking at the Nashbar frames. Are they any good? How heavy are
they?

The frame I have now is an aluminum - carbon fiber composite and is super
light. I'm not particularly emotionally tied to it; it's just that it's
still in relatively good shape and it would be a shame to get rid of it.

"Fester Bestertester" wrote in message
...
And naturally a stronger mounting point--still, I'd be scared to ride
a "light" frame that had been retrofitted with disc brake mounts. My
minds eye sees the torque used when removing a freewheel using a bench
vise time severalfold. Crrrrunch!

You're speaking of the braking forces applied to the retrofitted rear
caliper
tabs? A disc brake's torque is all circumferential (direction of
rotation).
No lateral (parallel to the axle) force at all.

Rear disc mount tabs on a modern bike's dropout are very modest. Witness:

http://tinypic.com/r/2nbbnfl/3

Note almost no lateral support. None needed.

All braking forces are pressing down against the seat stay. Very simple
design requirements, easily retrofitted by a competent mechanic & welder.
A
bit of test-fitting with rotor in place and caliper + mount in-hand is
required.

A basic drawing of the international standard mount is he

http://www.hayesdiscbrake.com/support_downloads.shtml

(Scroll down to the section "Industry Standard Mounts")

You'd probably want a little bracing
between the stays if doing this mind exercise.

???

The OP may want to consider the costs involved. Cheap frames from Nashbar
(under $100) & others make modification of your frame financially inviable
unless it's an emotional-attachment thing.