gschreckchat@comcast.net

Given the stffer nature of steel over Ti, I would suspect that reinforcement would be less of an issue. I am sure the metalurgists will jump in now and tell me that I am completely wrong.

The bolt on retrofit is very cumbersome, and i would rather spend the money to fix the frame. On the other hand, unless there is something special about your frame, it may be cheaper to buy a new frame or a compeltely new bike, by time you factor in new wheels, new brake calipers, retrofitting the frame and perhaps a new fork (unless it already has tabs). By time you pruchase all those items, a new bike often is less expensive

--

George Schreck
gschreckchat@comcast.net
(503) 502-0425

-------------- Original message --------------
From: Devin Flynn
Yes, the reinforcement would be necessary most likely. But I don't think it would be to hard for a frame builder to do the alignment and the reinforcement. Also if it were brazed (doug at Curtlo cycles does it this way) the would probably be less of a chance of overall misalignment of the frame do to any high heat warping.

Also, I believe that steel is MUCH easier to work with than Ti. Perhaps that is part of the reason why it was going to cost so much ?

I would plan on it costing a couple hundred dollar on a steel frame to add the tab and support. This is more expensive than the Brake therapy solution, but I think it looks much better. Especially if you have the builder remove those "ugly" rim brake mounts at the same time. ;)

Martin Baker wrote:
Adding disc brake tabs is actually a fair bit more complex than changing the dropout due to the change in forces applied to the seat-stay. Rim brakes apply the braking forces high up on the seat-stay near the junction with the seat-tube where it?s pretty strong (and designed for it). A disc brake applies the braking forces far down the seat-stay nearer the dropout, where the stays are typically thin and spindly on a frame designed for rim brakes. This can cause flex and misalignment as well as cracking, unless the welder adds appropriate reinforcement and gusseting to counter the braking forces. I looked into this for my ?99 Litespeed Obed Ti frame. Litespeed would only do it by replacing the entire rear triangle (cubic $$$!), but I did find a local builder who would add the tab and a gusset for much less. Ultimately I decided that it?s not worth it.

Martin

From: obra-bounces@list.obra.org [mailto:obra-bounces@list.obra.org] On Behalf Of Devin Flynn
Sent: Wednesday, April 25, 2007 9:03 AM
To: obra@list.obra.org
Subject: [OBRA Chat] adding disc brake tabs to steel hardtail

It can be done pretty easily. I had something similar done to a bike of mine not long ago. I had the original vertical dropouts replaced with horizontal ones to use for riding SS. I went ahead and hid the whole frame sand blasted and repowder coated while they were at it. It cost me just a bit over a couple hundred bucks for new dropouts and new powdercoat.

Adding only a disc brake tab would be much easier.

Doug at Curtlo Cycles in Washington did my work for me. But lots of people could do it. Brazing or tig would work.

-Devin Flynn

Ahhh...imagining that irresistible "new car" smell?
Check out new cars at Yahoo! Autos.

Ahhh...imagining that irresistible "new car" smell?
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john

With steel it is very easy to add material. But I certainly would not tig it ... since like mentioned the tubing can be thin in the middle, and arc welding always adds stress concentration...

The forces are higher fro a disc brake then at a rim brake because the moment arm is much smaller. The tubing up high on the seat stays is not really any beefier, well ok, you do have two tubes, but mainly much lower forces..

I would silver braze it. You could probably even get away with soft solder IF the joint is well lapped and it wets properly (experiment with flux and solder). Low heat, Propane torch is always easy to work with, and its difficult to mess up steel with the low heat of a propane torch.... But silver-solder would be more durable and permanent..

I would take a 6" -8 " section of spare seat stay tube or fork tube (cut off a junk frame...) and split it in half (like a log) and lap one half on your frame tube to spread the forces out.
I might also add reinforcement, ie a tube or gusset, in between the chain stay and the seat stay.
No sharp corners ! (stress concentrations points, AKA as crack initiation points).

A good framebuilder (portland has many) will know what to do, but its amazing how many can be way too conservative, and how others are not conservative enough... but most important they will have supplies and equipment to quickly and easily do the modification. I would show up with as much work done as possible. Cleaning and prep are 95% of the work !!

Martin Baker wrote:
v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} st1\:*{behavior:url(#default#ieooui) } Adding disc brake tabs is actually a fair bit more complex than changing the dropout due to the change in forces applied to the seat-stay. Rim brakes apply the braking forces high up on the seat-stay near the junction with the seat-tube where it?s pretty strong (and designed for it). A disc brake applies the braking forces far down the seat-stay nearer the dropout, where the stays are typically thin and spindly on a frame designed for rim brakes. This can cause flex and misalignment as well as cracking, unless the welder adds appropriate reinforcement and gusseting to counter the braking forces. I looked into this for my ?99 Litespeed Obed Ti frame. Litespeed would only do it by replacing the entire rear triangle (cubic $$$!), but I did find a local builder who
would add the tab and a gusset for much less. Ultimately I decided that it?s not worth it.

Martin


---------------------------------

From: obra-bounces@list.obra.org [mailto:obra-bounces@list.obra.org] On Behalf Of Devin Flynn
Sent: Wednesday, April 25, 2007 9:03 AM
To: obra@list.obra.org
Subject: [OBRA Chat] adding disc brake tabs to steel hardtail

It can be done pretty easily. I had something similar done to a bike of mine not long ago. I had the original vertical dropouts replaced with horizontal ones to use for riding SS. I went ahead and hid the whole frame sand blasted and repowder coated while they were at it. It cost me just a bit over a couple hundred bucks for new dropouts and new powdercoat.

Adding only a disc brake tab would be much easier.

Doug at Curtlo Cycles in Washington did my work for me. But lots of people could do it. Brazing or tig would work.

-Devin Flynn


---------------------------------

Ahhh...imagining that irresistible "new car" smell?
Check out new cars at Yahoo! Autos.

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john m schmidt
portland oregon

Devin Flynn

Yes, the reinforcement would be necessary most likely. But I don't think it would be to hard for a frame builder to do the alignment and the reinforcement. Also if it were brazed (doug at Curtlo cycles does it this way) the would probably be less of a chance of overall misalignment of the frame do to any high heat warping.

Also, I believe that steel is MUCH easier to work with than Ti. Perhaps that is part of the reason why it was going to cost so much ?

I would plan on it costing a couple hundred dollar on a steel frame to add the tab and support. This is more expensive than the Brake therapy solution, but I think it looks much better. Especially if you have the builder remove those "ugly" rim brake mounts at the same time. ;)

Martin Baker wrote: v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} st1\:*{behavior:url(#default#ieooui) } Adding disc brake tabs is actually a fair bit more complex than changing the dropout due to the change in forces applied to the seat-stay. Rim brakes apply the braking forces high up on the seat-stay near the junction with the seat-tube where it?s pretty strong (and designed for it). A disc brake applies the braking forces far down the seat-stay nearer the dropout, where the stays are typically thin and spindly on a frame designed for rim brakes. This can cause flex and misalignment as well as cracking, unless the welder adds appropriate reinforcement and gusseting to counter the braking forces. I looked into this for my ?99 Litespeed Obed Ti frame. Litespeed would only do it by replacing the entire rear triangle (cubic $$$!),
but I did find a local builder who would add the tab and a gusset for much less. Ultimately I decided that it?s not worth it.

Martin


---------------------------------

From: obra-bounces@list.obra.org [mailto:obra-bounces@list.obra.org] On Behalf Of Devin Flynn
Sent: Wednesday, April 25, 2007 9:03 AM
To: obra@list.obra.org
Subject: [OBRA Chat] adding disc brake tabs to steel hardtail


It can be done pretty easily. I had something similar done to a bike of mine not long ago. I had the original vertical dropouts replaced with horizontal ones to use for riding SS. I went ahead and hid the whole frame sand blasted and repowder coated while they were at it. It cost me just a bit over a couple hundred bucks for new dropouts and new powdercoat.

Adding only a disc brake tab would be much easier.

Doug at Curtlo Cycles in Washington did my work for me. But lots of people could do it. Brazing or tig would work.

-Devin Flynn


---------------------------------

Ahhh...imagining that irresistible "new car" smell?
Check out new cars at Yahoo! Autos.

---------------------------------
Ahhh...imagining that irresistible "new car" smell?
Check outnew cars at Yahoo! Autos.

Martin Baker

Adding disc brake tabs is actually a fair bit more complex than changing the
dropout due to the change in forces applied to the seat-stay. Rim brakes
apply the braking forces high up on the seat-stay near the junction with the
seat-tube where it's pretty strong (and designed for it). A disc brake
applies the braking forces far down the seat-stay nearer the dropout, where
the stays are typically thin and spindly on a frame designed for rim brakes.
This can cause flex and misalignment as well as cracking, unless the welder
adds appropriate reinforcement and gusseting to counter the braking forces.
I looked into this for my '99 Litespeed Obed Ti frame. Litespeed would only
do it by replacing the entire rear triangle (cubic $$$!), but I did find a
local builder who would add the tab and a gusset for much less. Ultimately I
decided that it's not worth it.

Martin

_____

From: obra-bounces@list.obra.org [mailto:obra-bounces@list.obra.org] On
Behalf Of Devin Flynn
Sent: Wednesday, April 25, 2007 9:03 AM
To: obra@list.obra.org
Subject: [OBRA Chat] adding disc brake tabs to steel hardtail

It can be done pretty easily. I had something similar done to a bike of
mine not long ago. I had the original vertical dropouts replaced with
horizontal ones to use for riding SS. I went ahead and hid the whole frame
sand blasted and repowder coated while they were at it. It cost me just a
bit over a couple hundred bucks for new dropouts and new powdercoat.

Adding only a disc brake tab would be much easier.

Doug at Curtlo Cycles in Washington did my work for me. But lots of people
could do it. Brazing or tig would work.

-Devin Flynn

_____

Ahhh...imagining that irresistible "new car" smell?
Check out new
cars
at Yahoo! Autos.

Devin Flynn

It can be done pretty easily. I had something similar done to a bike of mine not long ago. I had the original vertical dropouts replaced with horizontal ones to use for riding SS. I went ahead and hid the whole frame sand blasted and repowder coated while they were at it. It cost me just a bit over a couple hundred bucks for new dropouts and new powdercoat.

Adding only a disc brake tab would be much easier.

Doug at Curtlo Cycles in Washington did my work for me. But lots of people could do it. Brazing or tig would work.

-Devin Flynn

---------------------------------
Ahhh...imagining that irresistible "new car" smell?
Check outnew cars at Yahoo! Autos.