Front disc and rear canti?

[Dirk]

It really doesn't matter how powerful a brake you put on the front. It will make not one jot of difference to current frame design, or the ability to make use of the available braking power. Tyre and rim brake technology already far exceed the capabilities of existing frames.
Try grabbing a big handful of Ultegra rim brakes at 40 mph if you need proof.

 

[dan_bo]

I can't quite grasp what meaning that picture is trying to convey in the context of this thread.

Use yer imagination.

 

[Dirk]

Use yer imagination.

It looked like they'd hit something solid head on; doesn't seem to have any relevance to the thread.

 

[Kajjal]

It really doesn't matter how powerful a brake you put on the front. It will make not one jot of difference to current frame design, or the ability to make use of the available braking power. Tyre and rim brake technology already far exceed the capabilities of existing frames.
Try grabbing a big handful of Ultegra rim brakes at 40 mph if you need proof.

It is important you don't make up contradictory statements which can endanger people. It does matter how powerful brakes are and denying frames have been redesigned to allow for the additional force from disc brakes is untrue.

Read up on disc brake frame design, and why the changes were made.

http://www.sheldonbrown.com/disc-brakes.html

 

[dan_bo]

It looked like they'd hit something solid head on; doesn't seem to have any relevance to the thread.

Try 'how we used to stop our bikes'

 

[Dirk]

@Kajjal - No matter how powerful a brake you put on a bike, you are limited as to how much you can use. Rim brakes are effective enough to get the back end off the deck at high speed - how much more do you want?
I have not said that certain parts of frames have not had to be redesigned to accommodate the fitting of disc brakes - that goes without saying. However, you implied that the whole area of frame design, for front disc braked bikes, was different to rim braked ones because front discs somehow put more stress into the frame. They do not.
With reference to the actual subject of the thread, it makes no difference what the frame is, if it's converted to a front disc - so long as the correct forks are used. There are no magical 'disc specific' forces induced into the head stock.

@dan_bo - I don't ever recall having to run into a solid object as being the normal method of choice when stopping on any of my bikes.

 

[Ajax Bay]

Tyre and rim brake technology already far exceed the capabilities of existing frames.

don't make up contradictory statements which can endanger people. It does matter how powerful brakes are and denying frames have been redesigned to allow for the additional force from disc brakes is untrue.

@Dirk Thrust - Didn't you mean: the capabilities of existing frames can more than manage any stresses tyre and rim brake technology can throw at them. Think that your sentence is what Kaj thinks is contradictory, though "endanger people" - hmmmmmm?
Provided brakes are 'powerful enough' - and Dirk has suggested rim brakes are, it doesn't matter how much more powerful they are - rubber on the road becomes the limiting factor, combined with the rider's skill.
Frame redesign. Remember the issue is modifying a bike by fitting a front disc brake only, so redesign of the chainstay for a rear disc brake is not relevant, in this context.
You linked to Sheldon (btw think the article is rather dated): "But be aware: disc brakes can't be retrofitted without frame modification. A front disc brake stresses the fork heavily and can tear the front wheel out of the dropouts unless special measures are taken." There is no further reference to frame modification. So I'm still in denial. Please shake me out of that by answering the question I posed earlier. @Kajjal you advised and asserted: "Be careful fitting a front disc brake if the frame is not designed to take the extra force disk brakes have" and "Unless already capable most disc brake frames were strengthened at key points" and I asked "Which 'key points' on the frame would those be, please?"

what's likely to happen if I run a front disc with a rear cantilever?

Get the geometry of the new fork reasonably close (offset) to the existing fork.

 

[Dirk]

@Ajax Bay
I meant that regardless of how strong a frame is made, using current design and geometry, a good rim brake can overcome its riders ability to maintain control. A big handful of front brake will either have the back end off the deck, or the front end washing out - either way you are losing control.
Making the frame stronger, to 'cope' with even more powerful brakes, will not have any effect - you will still lose control.

 

[Sheffield_Tiger]

Disc, rims, what's the diff? Both have limitations

And by the way, after this I bought a bike with V's front & rear, then later bought disc forks for it and put these disc brakes on the front with mini-V's on the back. Worked fine. No hassle, no great twisty, breaky disasters