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 Post subject: Back disc brake?
PostPosted: Mon Feb 08, 2016 7:05 pm 
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Hi,

sorry if this seems like a stupid question, but I was just wondering whether it would be possible to replace the rear drum brake with a disc brake?


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 Post subject: Re: Back disc brake?
PostPosted: Mon Feb 08, 2016 11:21 pm 
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That would be a lot more trouble than it's worth. The rear brake is really useful only at low speeds or on bad surfaces. It contributes only a little to a hard stop during the first second or so before most of the bike's weight has shifted off the back wheel to the front. All of this is to say that the humble drum brake is more than adequate on the Rebel.
The front disk does a great job of pulling the Rebel down quickly from highway speeds all by itself, and i generally don't use the rear for normal braking.
To make a conversion to disk would require a new wheel and caliper assembly plus a lot of custom reworking of the master cylinder and brake pedal mounting. A lot of work for no real benefit.

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 Post subject: Re: Back disc brake?
PostPosted: Tue Feb 09, 2016 9:23 am 
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Well...there would be one benefit: ease in changing pads versus full rear wheel removal for shoes.

But as mentioned, it would entail a lot of one-off construction. About the only way to simplify (and I use the term loosely here) the job would be to see if you could find a "sprotor" that fits the lug pattern. Alas they're HD spec so you'd still need a HD spec rear wheel mated to the swingarm. Like I said, I used the term loosely. ;)

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 Post subject: Re: Back disc brake?
PostPosted: Tue Feb 09, 2016 2:00 pm 
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Yeah, I don't know much (anything?) about sprotors, but having seen what my sprockets look like after a few thousand miles, I would worry that the stopping power would be akin to spraying penetrating oil on your rotors before each ride.
brent

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 Post subject: Re: Back disc brake?
PostPosted: Tue Feb 09, 2016 3:04 pm 
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A "sprotor" ?? Are you kidding me?
As Brent describes, that has to be one of the dumbest ideas ever. Either lube your chain or keep grease off your brake disc.. Not the kind of choice you want to have to make.

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 Post subject: Re: Back disc brake?
PostPosted: Tue Feb 09, 2016 5:29 pm 
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I had actually forgotten about the existence of those things. :rofl: Honestly, the first time I saw one, it was really hard for me to believe it was a mass-produced part because it was such a bad idea (unless, of course, you find one for belt drive, where it makes _marginally_ more sense). Not only is there the issue of chain lube all over your rotor, there's also the problem with the heat of braking resulting in increased sprocket wear and, of course, deformation-- the "wobble" type scraping common to rotors that have had a few heat cycles run through them, particularly when you're running through puddles or rain regularly.

This warpage leads to additional chain and output shaft wear, and on and on---

it's just an incredibly bad idea. The first one I saw I really believed was something that the owner had machined himself. About two years after that, I found out it was something you could buy. While I didn't _quite_ die laughing, I must have laughed hard enough to get just enough brain damage to forget about their existence. :lol:

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 Post subject: Re: Back disc brake?
PostPosted: Wed Feb 10, 2016 9:54 am 
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See...this is exactly what NO riding for five months can do to someone.

I may have to take a BRC when this ordeal is over.

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 Post subject: Re: Back disc brake?
PostPosted: Wed Feb 10, 2016 5:23 pm 
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Duke wrote:
Honestly, the first time I saw one, it was really hard for me to believe it was a mass-produced part because it was such a bad idea (unless, of course, you find one for belt drive, where it makes _marginally_ more sense).


I'd like to see the brake caliper that would fit over a belt pulley. The slot would have to be an inch or more wide. Combining brake and drive sprocket/pulley is just a terrible idea period

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 Post subject: Re: Back disc brake?
PostPosted: Sat Feb 13, 2016 4:24 am 
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Yeah, costs way less to replace drum brakes than to install a disc brake.
I've got 15k miles on my Rebel, and the rear brakes are as good as new, barely ever used.
They also stop the bike better than the front disc!
Especially with a passenger!

replacement of brake pads is really easy on the drum,
the only discomfort is the need to remove the rear wheel,
the rest speaks for itself, and is about as hard as replacing disc break pads.


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 Post subject: Re: Back disc brake?
PostPosted: Sat Feb 13, 2016 6:30 am 
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MeeLee wrote:
They also stop the bike better than the front disc!
Especially with a passenger!.


rofl rofl rofl rofl Good one!
:popcorn:

brent

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 Post subject: Re: Back disc brake?
PostPosted: Sat Feb 13, 2016 7:09 am 
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MeeLee wrote:
.......the rear brakes are as good as new, barely ever used.
They also stop the bike better than the front disc!
Especially with a passenger!


If you believe this, you are in danger of unnecessarily becoming involved in a collision due to ineffective braking.
Your statement can easily be demonstrated to be false by doing a couple of test stops using only front or rear brake from a fixed speed. (assuming proper braking technique is used on both wheels)

The weight of a passenger is essentially irrelevant to stopping distance on any motorcycle which can lock up its brakes under any real world load (unlike a heavy truck) . Brakes don't stop your bike, the wheels gripping the road stop your bike. Brakes just stop the wheels. Available braking force of a wheel is proportional to the friction coefficient of the tires on the road times the weight on the tire, and forward energy to be dissipated when stopping is proportional to weight times velocity squared. therefore the weight cancels out of the equation.

During hard braking, the weight of bike and passengers transfers toward the front, making most of the weight and braking power available on the front wheel rather than the rear.

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1996 Ducati 900SS
1973 Norton 850 Interstate


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 Post subject: Re: Back disc brake?
PostPosted: Sat Feb 13, 2016 9:47 pm 
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Reconcile these two statements:

MeeLee wrote:
I've got 15k miles on my Rebel, and the rear brakes are as good as new, barely ever used.


with
MeeLee wrote:
They also stop the bike better than the front disc!


Given the two comments, _you're_ not using the rear brake much; certainly not enough for extensive testing if they're barely ever used.

How have you decided that the brake you don't use is far more effective than the one that you _do_ use, particularly against the volumes of evidence to the contrary?

Moreover, how do you sleep at night putting nonsense like this up here where true novices might actually think you have some clue what you're talking about?

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 Post subject: Re: Back disc brake?
PostPosted: Sun Feb 14, 2016 8:55 pm 
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I'm not sure what you all are saying.
The rear brake is capable of locking up the wheel, while the front brake isn't (unless you go really crazy on the lever).

With a passenger, a lot of weight is added on the rear wheel, so rear wheel braking is even the better!
The Rebel has a lousy front brake, but a great rear brake!
Anyone saying anything else, is plain :naughty:, and doesn't know squad about a Rebel, and making an idiot of himself!

Not sure what you guys are not understanding about this..??


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 Post subject: Re: Back disc brake?
PostPosted: Sun Feb 14, 2016 9:37 pm 
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MeeLee wrote:
I'm not sure what you all are saying.
The rear brake is capable of locking up the wheel, while the front brake isn't (unless you go really crazy on the lever).


Emergency braking requires application of the front brake up to the point of locking the front wheel. If done smoothly and progressively the rider will get timely feedback from the front tire, (squirming and squealing) warning of impending lockup and telling the rider that he has reached the limit. It takes knowledge of the technique and practice to be able to do this consistently.
If you can't squeeze the front brake lever hard enough to lock the front wheel, you should go back to school and learn how. I'd suggest in your case it is inexperience and fear of the front brake that is the problem.

locking the rear wheel doesn't contribute significantly to stopping if you are using the front brake, but can contribute to losing control and crashing.

MeeLee wrote:
With a passenger, a lot of weight is added on the rear wheel, so rear wheel braking is even the better!


If you are using the front brake as indicated above, most of the passenger's weight, your weight, and the bike's weight will be transferred to the front wheel within a second or two of brake application, making it very resistant to locking due to the combined weight pressing it into the road. This is why you apply the front brake quickly but gradually to allow this weight transfer to happen before reaching maximum braking effort. The more weight on the wheel, the more braking force it can apply without locking up. The rear wheel and brake will be mostly just along for the ride after the first second or so of emergency braking.

It's quite irresponsible of you to be carrying a passenger who has a right to expect you are a qualified rider if you don't understand this.

MeeLee wrote:
The Rebel has a lousy front brake, but a great rear brake!


I suspect that few, if any, experienced riders would agree with you on this. I know I don't.

MeeLee wrote:
Anyone saying anything else, is plain <img src="http://rebel250.com/rebelforum/images/smilies/naughty.gif" alt=":naughty:" title="naughty" />, and doesn't know squad about a Rebel, and making an idiot of himself!


In all fairness, after nearly 50 years of riding and wrenching on all kinds of motorcycles, and 16 years of teaching others how to ride, I would suggest I probably know a lot more about Rebels and riding them than you do.

MeeLee wrote:
Not sure what you guys are not understanding about this..??


I don't understand why you keep spouting nonsense while expecting knowledgeable people to buy into it.

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 Post subject: Re: Back disc brake?
PostPosted: Mon Feb 15, 2016 8:06 am 
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MeeLee wrote:
I'm not sure what you all are saying.


I'm not sure you know what you're saying.

Duke pointed out how you contradicted yourself, first by claiming you hardly use the back brake then later by claiming it's the best brake based on your observation that the rear brake (that you don't use) being worse than the front brake (that you use even less).

Explain that and we can go forward with the topic.

Quote:
The rear brake is capable of locking up the wheel, while the front brake isn't (unless you go really crazy on the lever).


Ah, see...now we're getting somewhere. You are basing the brake's effectiveness by your ability to lock them up. In other words, it would appear that you haven't learned proper braking technique.

Quote:
With a passenger, a lot of weight is added on the rear wheel, so rear wheel braking is even the better!


And all that passenger weight gets transferred to the front brake once the rear is applied. Once you learn proper braking technique that will become readily apparent.

Quote:
The Rebel has a lousy front brake, but a great rear brake!


Duke and Duckster already explained this one better than I can.

Quote:
Anyone saying anything else, is plain :naughty:, and doesn't know squad about a Rebel, and making an idiot of himself!


Even though you are posting in a different guise I will remind you once more of this board's policy regarding name calling.
That was pretty close, tread carefully as prior warnings from your old account are equally applicable to your current account.

That said, I daresay anyone here that has responded in this thread has more miles backing their Rebel out of the driveway than you have on your odometer.

Quote:
Not sure what you guys are not understanding about this..??


We do understand this. You don't, not until you grasp proper braking technique anyways.

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 Post subject: Re: Back disc brake?
PostPosted: Mon Feb 15, 2016 5:37 pm 
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I wasn't discussing braking techniques here,
Just braking capabilities.
The rear brake can lock up the rear wheel, meaning I see no reason to improve on it.
The front brake.... I don't know... I've been riding a few years on a rebel, and have never locked up the front brake.
I fear that the rubber hose would burst before I completely lock the front wheel.

My technique is indeed braking with the front brake, despite it braking a lot worse.
I use the rear brake for compensating the front in case stopping power isn't great enough.

With me in the seat, there is about an even distribution of weight on the wheels; which does shift forward as we brake.
With a passenger, more than 90% of the passenger's weight is added on the rear wheel.
When braking only a fraction of that weight goes to the front,
resulting overall in a better braking on the rear than on the front brake; because the front brake calipers and pads are too small to essentially stop the bike, plus rider and passenger in a distance shorter than the rear brake.

They say 80% of the weight goes to the front wheel when braking.
But the stock braking calipers aren't up to the task for decent stopping.


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 Post subject: Re: Back disc brake?
PostPosted: Mon Feb 15, 2016 7:12 pm 
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MeeLee wrote:
I don't know... I've been riding a few years on a rebel, and have never locked up the front brake.
I fear that the rubber hose would burst before I completely lock the front wheel.


There... you just explained your own problem... You don't know and you're afraid of the front brake.

It's clear from your comments about Rebel braking capabilities that your braking technique is sadly lacking.
If you were a proficient rider, you would know that the braking performance of the Rebel (or any motorcycle really) is primarily due to its front brake and the Rebel brake is quite good for a lightweight motorcycle. Do yourself a favor and take a motorcycle course where you will learn what your front brake can do for you in an emergency.
In the meantime, here's an interesting report that may replace some of your misconceptions with some factual information.

https://www.msf-usa.org/downloads/imsc2006/Belmonte-Performance_Evaluations_of_Various_Braking_Systems-Paper.pdf

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 Post subject: Re: Back disc brake?
PostPosted: Mon Feb 15, 2016 8:50 pm 
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FWIW that same grade of rubber hose is used on Honda's CBR and Gold Wing for their dual disc systems.

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 Post subject: Re: Back disc brake?
PostPosted: Tue Feb 16, 2016 6:30 am 
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MeeLee: I think you are vastly overestimating the contribution to braking (i.e actually stopping the bike) of a locked-up (i.e. skidding/dragging) tire.
Please, for your own sake, take some time to learn effective motorcycle braking technique and for the sake of your unwitting passenger(s), leave that pillion seat empty for the time being.
brent

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 Post subject: Re: Back disc brake?
PostPosted: Tue Feb 16, 2016 11:50 am 
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Also noteworthy, if one fully grasps proper braking technique they would also understand why the rear locks up so easily.

Remember what I said about the weight transferring to the front wheel? There's the clue.

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Dismantling, sawzalling, and rattle canning does not make a bobber. That's called an "ANCHOR".
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