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dual front brakes, or one?... your opinion?

20K views 74 replies 20 participants last post by  Dodsfall 
#1 ·
i see a lot of people with older bikes wanting to go with a dual front brake front end.. and i was wondering what the tradeoffs would be.. there has to be some downside to it... more unsprung rate, more to repair and maintain, etc...

so... what would you say some of the pros and cons are of both single disc front ends, and dual disc front ends, what you would prefer, and why?
 
#33 · (Edited)
Math time! There's a formula that explains it pretty well. Hydraulic multiplication of force is directly related to the surface area of the pistons involved. If you take the surface area of the caliper piston and divide it by the surface area of the master cyl piston, you have your force multiplier. So if your brake caliper piston is 1.5 sq in, and the master cyl is 0.25 sq in, you get something like this:

1.5/0.25=6

So, so for every 1 pound of force input, you get 6 pounds of force output.

When some brilliant mind decides to hack off a caliper in a dual disc setup, no only to they halve the amount of friction surface, they halve the clamping force of the hydraulic system itself. Oops?

Be aware the reverse is also true. If you ADD a caliper, you not only double friction surface, you potentially double the clamping force of both calipers. So, our 1:6 ratio becomes 1:12. Why is this bad? Well, 10 lbs of force is easy stuff for a human hand. But that becomes 120 lbs of clamping force at the calipers, for each caliper. 120x2=240. So, 240 lbs of force, on the front contact patch of a 400 lb-ish bike, with no more hand effort than it takes to carry a sack of groceries. Oops again?
 
#34 ·
An excellent explanation, and this shows why if you start mucking with things such as brakes, you had BETTER know what you are getting into.

And even if the job is done rigth, there is the issue of how the improved braking performaance needs to be learned on the bike. This is because the rider will be used to how it USED to be on that bike. So, you may consciously know that the braking will be different, but the body still needs to learn the difference.

That being said, what can be done to make this done right?
I do not know the OP's bike, but I can use an example I do know. My own bike.

Now, if I were to change it to dual disks up front, how can I do this, and make it so the pressure applied to each caliper piston is the same as before? Use a master sylinder set up for twice the number of cylinders, and the associated lines. Easy enough. Honda made the exact one I need for the 1800 VTX. Now, upon doing this, I am going to have a hell of a learning curve ahead of me. I will have effectively twice the braking force available to me. I will NEED to relearn the bike.

If your in any way uncertain about this, my recommendation is to not try to mod the brake system from a single caliper to dual calipers. If you really feel the need for better braking, you can change the pads, and even the lines to braided stainless. Or, you can get a different bike with dual disks already.
 
#35 ·
A larger master cyl, gives a quicker oil flow, but a lower pressure.
Regardless, you just will have to squeeze the lever a bit harder, no harm done; unless the brake pads and disc are really small, and not upto the task of braking the bike well.

Though most are, and just as long as you squeeze hard enough, you'll be able to lock the wheel.

It'll just 'feel' different, but not pose a hazardous situation.

Don't forget, that even 20 years ago, the top end, deluxe bikes, had way less comfort, and mechanical reliability in these things like brakes, than modern budget bikes!
Technology has come far, even in hydraulic brakes (for one, brake pads have changed, to be more durable; hoses have become better, less leaking, handling higher pressures, disc brake calipers last longer, have better seals etc..), ..

So if we could be happy with a 20 yr old bike, we can for sure be happy with a modern bike which's brakes are not functioning 100% to todays standards, however which brakes are still functioning better than the older models!
 
#36 ·
Pro, I'm glad that you are ready and eager to meet Jesus...

Just...wow. I sincerely hope no one follows your advice. It is unsound, and largely untrue.

See, I had a friend in high school that tested this theory the hard way. He tried "improving" the brakes on his camaro by swapping in the master cylinder from a 3500 HD truck. Direct bolt on, just bigger bore. Yeah, he made it all of two blocks before he totaled both his car and someone else's because "it wouldn't stop." Worst part was his insurance wouldn't cover any of it because his UNSAFE MODIFICATION was the direct cause of the accident.

If you don't understand something that involves the safety of you and those around you, don't f*** with it!
 
#37 ·
I'm not saying it is a good and sound solution, but it will work.
Like duct taping a drain pipe is not sound, but could get you going for a few weeks, months, or in some cases a few years...
Some day you'll probably have to repair it though.
But seriously, a master cylinder pushing 2 brake calipers can easily push one. The response is a bit different, but you could stop the bike with it!
That remembers me of a time, when my car's rear brakes stopped working because of an oil leak in the drums.
Braking was more difficult with the front 2 brakes, but at no time was it impossible!
Even hard braking was possible!
And if anything, a lot of bikes are made for one disc brake per wheel. Cars are not made for 2 disc brakes.

Just saying...

Eventhough it's not a sound solution, it is not impossible to use that solution.
 
#38 ·
I guess what Prodigit is saying is true. You may be able to stop a motorcycle or a car with malfunctioning brakes, or brakes that are not as good as the original manufacturers brakes. But if you had a choice, why would you want to?

Not all "progress" is good, but improvements in brake technology is one of those progress improvements that certainly have been worthwhile!

Bottom line: unless you really know what you're doing stick to the brakes that the manufacturers have designed. they certainly have a vested interest in giving you the best brakes they can.

Having said this, I can certainly see how some improvements might be worthwhile: Better brake pads, ventilated discs, Steel braided brake lines are certainly improvements that are easy to make and will improve braking performance.
 
#39 ·
And I can tell you up is down and left is right, I does not make it right. You are messing with the front brake, which is YOUR STOPPING POWER not a leaking cylinder on a 4 brake system.

Even that you should have gotten fixed as soon as you found out not continued driving.

If you don't know what you are talking about DO NOT give advise.
 
#40 ·
"Math time! There's a formula that explains it pretty well. Hydraulic multiplication of force is directly related to the surface area of the pistons involved. If you take the surface area of the caliper piston and divide it by the surface area of the master cyl piston, you have your force multiplier. So if your brake caliper piston is 1.5 sq in, and the master cyl is 0.25 sq in, you get something like this:

1.5/0.25=6

So, so for every 1 pound of force input, you get 6 pounds of force output."

Thanks for posting. Okay, now I have my head wrapped around it. So it's not so much that the internal pressure changes, it's that the total work applied to the rotor(s) is changed.

...and since the caliper pistons don't come as quickly to a "hard stop" against the rotor, and there's less pressure against the caliper pistons (as a function over time,) it takes a harder "squeeze" on the lever to try and get the same amount of usable force against the rotor.

The bike I just mentioned, by the way, does stop. I'm sure it doesn't stop as quickly as it did, and the brake lever feels a little mushy, but I wouldn't say in that particular case it's unsafe.
 
#41 ·
Well, if you're really into fast braking, then just install a super master cylinder and equip your forks with 4 brake cylinders per wheel... Might work better than a single or dual system.

I have to say that my single piston brake caliper, and single disc brake provides plenty of braking power; especially for city riding.
Perhaps not for racing, but then again, it's a cruiser bike, not a racing bike...
 
#42 ·
i guess if you wanted better braking, without over complicating the system you could focus on the brake components themselves... a higher quality, vented brake rotor which bleeds off the heat caused by the friction of the brake faster would offer better braking performance without increasing the complexity of the system
 
#44 ·
I got dual 300 mm disc brakes up front, and a single in the rear. like the response of stopping power if say a deer comes running out of the woods at last minute. Nearly destroyed one the other night as it jetted out in front of my plow while going 42 mph. I swear if I had not taped on the brake pedal, that deer would of been a blood bath all over my blade.

I have a halogen on my cruiser, like most bikes out there ( will upgrade to LED in future once I find one reasonably priced).

Though I would imagine when the time comes for pad replacements I will be paying more vs single up front, however out of all the bikes I owned with the exception of my ATV, I never replaced my pads on them. I must have owned about a dozen or so bikes since I was 11 years old.

I do find it amusing how some builders on TV like to build bikes with ridiculously huge wheels, and have one average single rotor up front and claim it is worthy of a daily rider. And the 1-2 gallon tank sometimes they use only cough:cough: PJD cough:cough:

As far as your ride coming standard with a single disc brake up front, unless you are upgrading the wheel size, I personally wouldn't bother adding a dual set up. Single disc brakes are more then capable of stopping 400-500 lbs bikes. The heavier ones 750 lbs and up, thats where a dual set up makes more sense, that and super sport bikes cause of their potential high rate of top end speed, which some may or might not want to travel at that rate of speed. But it's a peice of mind knowing you have the dual disc brakes.
 
#51 ·
"I mean that bike is quite a heavy lump, and whilst it's all very well saying it's a cruiser and not a sports bike, you might still want to haul it up quickly from 70mph one day, and I pity anyone in that situation aboard that bike."

Everyone that rides should know and understand the capabilities of their bike. And, almost all bikes are different so it takes more then one or two short rides to really get to know any of them. It is no more "unforgivable" that Harley puts single disks on the front of some of it's bikes then it is "unforgivable" that some other brands still use disk brakes in 2013. They're just different, that's all, and they require a different skill set from the rider.

One of my bikes weighs a lot more then any Sportster, yet it only has a single disk with a little bitty single caliper, and that of 17+ year old technology as well. No, it will not stop as suddenly as a dual disk bike of the same weight but I've never yet had a problem with that. Why? Because I understand the difference, I know that bike, and I adjust my riding style (usually) so that I survive the ride.
 
#53 ·
Everyone that rides should know and understand the capabilities of their bike. And, almost all bikes are different so it takes more then one or two short rides to really get to know any of them. It is no more "unforgivable" that Harley puts single disks on the front of some of it's bikes then it is "unforgivable" that some other brands still use disk brakes in 2013. They're just different, that's all, and they require a different skill set from the rider.

One of my bikes weighs a lot more then any Sportster, yet it only has a single disk with a little bitty single caliper, and that of 17+ year old technology as well. No, it will not stop as suddenly as a dual disk bike of the same weight but I've never yet had a problem with that. Why? Because I understand the difference, I know that bike, and I adjust my riding style (usually) so that I survive the ride.
You simply cannot say that a braking set up is adequate because you learn to adapt to it in every day riding conditions.
The only way you really know how effective your brakes are is when you have to stop quickly, and in a short distance.
Until you have been in that situation, you do not know how good (or bad), your brakes are.
 
#61 ·
Follow the two second rule and every bike out there will stop before the car in front of it, even though he hit his brakes first.

R1 or 883 both two seconds behind another vehicle will stop without hitting it.

The R1 may stop in a shorter distance, but that just means he has to watch his mirrors harder to make sure the car behind him doesn't hit him.

Bottom line drive safely and you will be able to stop your ride.
 
#64 · (Edited)
Yes. You could take an old 1980's disk brake setup and attach it to a 2013 model and stop in the same distance, as long as it was working correctly.

Given the same weight, same tires, same suspension, same steering geometry, same tire temperature and same road conditions.

Brake fade could come into play, which is the advantage of having more modern, dual, or larger better-ventilated disks. With normal street riding, brake fade rarely happens unless the rider is going down a mountain or braking an unusually heavy amount.

In a track scenario, where the brakes are being used hard and often, a dual setup with more modern brake cooling setups will help combat brake fade and be more efficient.

In a straight line stopping scenario without overheated brakes the minimum stopping distance is determined almost exclusively by the friction of the tires on the pavement at or near threshold braking. The point at which the rubber meets the road (where the stopping friction does the work of slowing the motorcycle) won't care how the stopping power is applied to the wheel, just that it is applied.
 
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#73 ·
http://www.motorcycleforum.com/showpost.php?p=910693&postcount=75

In a nutshell, dual disks and/or more efficient brake setups resist brake fade much better than a standard single disk. Most riders will not use their brakes hard enough with normal street usage to make a difference.

The question is pretty much the same as arguing, "Since engines with 27 horsepower produce enough energy to do highways speeds, why don't all motorcycles have them?"
 
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