View Full Version : Disc Brakes - Design flaw?

04-28-2016, 12:28 PM
Hey all....

No matter how hard I look at the designs for the disc brake mounting on the rear axle, I still seem to have an unanswered question in my mind. The hub is welded to one end of the axle, and the disc brake mounting flange is also welded to the axle. Here's my question.... how do you change out the rotor should the brake rotor wear out? Seems like the clearance to either side would be insufficient to swap out the rotor. Any thoughts/experience? Maybe I'm just looking at it the wrong way.


04-28-2016, 01:12 PM
You don't typically wear out disc rotors on a bike- you wear out the pads. On 2 wheeler you can damage them in falling but on 3 wheeler they are well protected.

04-28-2016, 01:13 PM
I thought the disc rotor flange and the freewheel mount were secured via grub screws onto the rear axle on a delta .

only the hub flanges were welded on at one end

Mine are still a ***ger to remove as the shaft does get a little pitted with the indent made from the grubscrew point.

regards emma

02-25-2017, 02:41 AM
Hey Emma~

From what I can tell, the freewheel mount is secured via grub screw (which is fine) with an option to weld, but the rotor flange is welded straight to the axle. I guess my current plan is to just use the set-screw for the freewheel mount and then just plan to have enough clearance to slide the axle outboard enough to take off the rotor and put a new one on. Hopefully I never have to do that! :juggle2:

Looking back through the plans, it's actually hard to tell what they do on the end of the axle the brake goes on. This is the last clear picture they put in there... maybe just a washer and a bolt/huge cotter pin could secure it at the end of the shaft.

02-25-2017, 06:41 AM
... Mine are still a ***ger to remove as the shaft does get a little pitted with the indent made from the grubscrew point...

Normal engineering/design pratice is to put a flat on the shaft, where the grub screw "bites", so that any indents/marks are submerged below the shaft diameter.
You could also use small brass pad as an "intermediary" between shaft and grub screw.

02-25-2017, 06:45 AM
You don't typically wear out disc rotors on a bike...

That's a wishful thinking :)
All it takes is slightly longer, hard application of brakes, for a disc to warp from the heat... making more or less useless (and annoyingly noisy when it rythmically touches the pad).
Discs are just as much wearable items as pads.

02-25-2017, 11:39 AM
I have a co-worker using disc brake on his upright to work. In last 10 years he replaced the pads 5 times. And the bike once because he got hit. Never the disc. My nephew activitly runs up an down mountains has replaced his pads 6 time in last year and replaced disc once. So I am only guessing wear will depend on usage. My son goes through rim pads every 6 months. I am the one to change them. He's a road rider. But it his only means of transport. But that is where I observed the wear.

02-25-2017, 12:11 PM
I am not disagreeing with you, as to what wears the most.
What I am suggesting is that to disregard the need for provisions to replace a disc is foolish.
It would take a lot to "wear" the disc, but it doesn't take a lot to heat distort or bend the disc - at which point you will be very happy to be able to simply replace it :)

02-25-2017, 02:21 PM
Agree with Mr B here , Discs and calipers should both be replaceable , unless you want to remake a rear axle assemble , whatever turns you on .

My idea of

works well if you are well weight endowed I suggest a 3rd middle mount .

point Noted Mr B but then I am not a mechanical engineer ( I left in my first year ).

regards emma