Ok front brakes now

Classic Goldwings

Help Support Classic Goldwings:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Yep. I think the WORST of 'em going bad is from exposure to UV rays... after all, they're plastic. If one could cut glass, fit 'em tight, and find some quality epoxy that won't be eaten by DOT brake fluid, that'd be the way to go...

I've never seen a motorcycle with hydraulic drum brakes... but... I've seen a SIDECAR with hydraulic drum brake.

I had an '80 Sportster with hydraulic disk in the rear... but all my others have mechanical drum... and frankly, that was more than sufficient IMO, because when I really need to stop, there's only one (front) tire on the ground... at that point, a rear brake is totally moot.

Back to the blackboard:

The important thing to understand about brakes, and particularly... hydraulic brakes, is that the whole point of it, is to turn the kinetic energy of a rolling motorcycle... into HEAT.... and that's all brakes do.

I could run through the energy calculation process and demonstration that I used for the ACELA high speed trainset, but it'd take lots of whiteboard that doesn't exist here, but the principles are what's really important:

If you're a 900lb motorcycle, travelling at 100 feet per second, the kinetic energy is simple: Energy = Mass times Velocity squared...

900 x 100 x 100 = 9 million foot pounds per second
(I used pounds, because I started with 900 pounds, and I used feet and seconds, because the velocity is in seconds!)
that means, if I were to stop the motorcycle in JUST ONE SECOND, the force would be 9 million pounds.

Seems like alot, doesn't it? 100 feet per second is... 68.18mph. (think about that when you're texting... 3 seconds is... a football field )
Let's see what that really amounts to in horsepower. One horsepower is 33,000ft-lbs per MINUTE.

So take 9000000, divide by 60... that's 150,000ft-lbs per minute. Divide that by 33000, and it's... 4.5 horsepower... for ONE MINUTE.

Let's say you make that stop in 4 seconds... that's 1/15th of a minute... so 4.5 * 15... that's 67.5hp absorbed by the braking system. Doesn't seem like much, does it? 1hp/min = 42.41 btu/min... that means your 4 second braking yields 67.5*42.41= 2862.675 BTU (British Thermal Units) of energy.

Now, one BTU is the amount of energy it takes to raise one pound of water, one degree farenheit.... and in the case of the above, that's happening in FOUR SECONDS. One gallon of water is 8lbs... that means 2862/8 = 358 degrees in that same four seconds.

Let's say that front brake disk was water, and weighs 8lbs... it'll see a 358 degree rise in four seconds... if it starts at 60F, it'll be 358+60= 417 degrees once you're stopped.

Are we tired of math yet?
 
Did you know Honda did make a few Cable-Front disc models? A CB125 and I think the CM250T or one of those about that time frame.
 
I could run through the energy calculation process and demonstration that I used for the ACELA high speed trainset, but it'd take lots of whiteboard that doesn't exist here

I know, I am :0fftopic: :mrgreen: , but couldn't they have worked out the math so that the ACELA didn't have so much harmonic vibration at high speed that it didn't shake me across the isle compared to the old Metroliner coaches? I will take the Northeast Regional over ACELA any day just for the more comfortable ride!

OK, back on topic.......front brakes. :doh: :hihihi:
 
Sheesh I’d love to have cable everything ...personally on a bike I see hydro crap as a downgrade period ...the leverage involved doesn’t warrant the application cables can made so much better than they ever were and be dam near invincible
 
As long as they don't combine the 2 like cars did for rear disc brakes in the 80s and 90s, and some still today. Actually I'm surprised the PTB have not "mandated" a parking brake combination caliper for motorcycles, just to spite everyone.
 
Cable actuation vs hydraulic, there's an obvious advantage and disadvantage to each. First being, that cables just don't leak... Plumbing, being the Root Of All Evil... invites a host of challenges. The cable isn't naturally self-adjusting, but cables just don't leak. They get bindy... but they don't leak...

OT, but... Mac- the Acela's shaking... that's called HUNTING... and it goes WAY beyond the Acela trainset... it involves the AEM-7 locomotive, the Metro cars, and freight service. Hunting is a result of the steering geometry (wheel taper) and track geometry (rail profile and curve radius and offset) not being harmonized. Until the Northeast Corridor trackway, and all equipment is set to work on the same geometric plan, you will have hunting. To correct this, the freight service must be excluded, the old cars must be removed, and the trackway geometry corrected to work with high speed service. At the same time, all at-grade crossings must be eliminated (either elevate the road traffic over, or sub it under, or block it off), and be full protected right-of-way, so that they can run per the original design spec. They'll also have to get the towns along the way to remove speed restrictions, and convert the electrification to all be unified on 25kv 60hz, so the tap changers in the power cars don't have to chunk from one mode to another when going through the antique territories.
 
[url=https://classicgoldwings.com/forum/viewtopic.php?p=212106#p212106:31kb45m8 said:
DaveKamp » less than a minute ago[/url]":31kb45m8]
Cable actuation vs hydraulic, there's an obvious advantage and disadvantage to each. First being, that cables just don't leak... Plumbing, being the Root Of All Evil... invites a host of challenges. The cable isn't naturally self-adjusting, but cables just don't leak. They get bindy... but they don't leak...

And moments after I wrote that, I realized all the occasions where strange things happened... like... the one time I was driving my wife's old Buick, and found automatic transmission fluid dripping from the dashboard onto my shoe... :shock:
 
[url=https://classicgoldwings.com/forum/viewtopic.php?p=212055#p212055:is54zin2 said:
pidjones » August 20th, 2019, 7:21 pm[/url]":is54zin2]
I hate brakes. Put a whole can of DOT3 through the fronts on the '79 and it still looks a little muddy, but the work. Afraid the reservoir may be leaking now, though.

Bought an eBay reservoir from Saber Cycles, IIRC. Works fine.
 
[url=https://classicgoldwings.com/forum/viewtopic.php?p=212091#p212091:2jufn00w said:
GTC@MSAC » August 22nd, 2019, 5:39 pm[/url]":2jufn00w]
Did you know Honda did make a few Cable-Front disc models? A CB125 and I think the CM250T or one of those about that time frame.

I have a drum operated front cable on my 400cc Honda. It is one of my major criticisms of that bike.
 
I have a drum operated front cable on my 400cc Honda. It is one of my major criticisms of that bike.

Hee hee... like... I've got it pulled in all the way, and the only thing that's happening... is the front spokes are getting really loose? :smilie_happy: :rant:

The 'truck bike' I built previous to the GN400 was a KZ250, and IT had a front drum brake, single-leading design... IIRC it was about barely larger than a McDonald's Cheeseburger... and I think the cheeseburger could do a better job stopping me... :beg:

I can't say I've seen a cable-op disc on a motorcycle, but I've set up cable-op disc calipers on tandem bicycles... there was one outfit that made a really nice one, and the op concept was pretty simple- the 'piston' was a piece of stainless tube with a trio of helical grooves machined in, that had ball bearings, and a matching groove in the caliper body. It was very effective when 'right', but it was kinda susceptible to road crap IIRC.

Hydraulics is basically a (sigh) necessary evil with disc calipers nowdays.
 
Joe, my advice on it, is to just dive in- get the caliper hoses off, put catch pan under, and pump the fluid out of 'em, run it all out, get the master cyl and calipers off, replace the flexible lines, flush the hard lines, rebuild both ends good, and reassemble with new banjo bolt washers.

There's no escaping getting brake fluid on stuff, but you CAN minimize damage by just goin' through all of it at once...
 
Can't you bleed at the banjo bolt at the brake itself? Messy, but I've bleed car brakes in a similar manner.
 
They make bleeder rescue kits so you drill out the old bleeder and out to 1/8" pipe tap (you supply drill and tap). They supply a brass plug with a small steel bleeder in it. I've rescued a couple calipers that had the bleed screw so tight or rusted in that PBblaster, a week wait, heat, tapping, gentle torquewith a drill bit shaft inside to prevent collapse still resulted in snapping off the bleeder. I get the kits at the local auto parts chain. I hate brakes.
 
Top