Wtf Front Brake Lever Caved In

[KRS1]

I was checking the oil window by holding the bike straight up by the right grip and had the front brake lever pulled in to keep it steady, then the the brake lever kinda caved in and went all the way to the grip, like the pump seal gave or something ...<deleted> ?

This ever happen to anyone else....? The brakes still work, but this kinda freaked me out, dont want to get caught by surprise because i ride mainly in the canyons, and have to brake hard 50% of the time...

What exactly happened to the front brake?

[wantan]

Just a guess: Air in the brake lines? Old brake hoses?

[KRS1]

not sure man, but i did squeeze the lever harder than usual, since i had to hold the bike up. Its like the pressure just passed through.

But still pressurized the front brakes.

[BigBikeBKK]

What kind of bike??

[Garry]

If your brakes recovered from pumping, its more than likely an air bubble. Bleed your brakes

Sent from my iPhone 3 using ThaiVisa app

[KRS1]

What kind of bike??

2005 SV 650s

Im thinking about replacing it with a sv 1000, or a 2008 gsxr 600...

Edited September 12, 2012 by KRS1

[KRS1]

If your brakes recovered from pumping, its more than likely an air bubble. Bleed your brakes

Sent from my iPhone 3 using ThaiVisa app

I think that would be a smart move, i have a ride this weekend in canyon country and dont want to go flying off a cliff... i once had an NSR 150 that did something similar during a drag race, back brakes went out completely and it never did it again.

Any chance the seal is deteriorating and only able to hold a certain amount of pressure? There is a little fluid on the lever where the stub pushes in the piston, but no actual fluid in the area of the piston...strange, maybe i have to take a closer look.

Edited September 12, 2012 by KRS1

[BigBikeBKK]

If your brakes recovered from pumping, its more than likely an air bubble. Bleed your brakes

Sent from my iPhone 3 using ThaiVisa app

I think that would be a smart move, i have a ride this weekend in canyon country and dont want to go flying off a cliff... i once had an NSR 150 that did something similar during a drag race, back brakes went out completely and it never did it again.

Any chance the seal is deteriorating and only able to hold a certain amount of pressure? There is a little fluid on the lever where the stub pushes in the piston, but no actual fluid in the area of the piston...strange, maybe i have to take a closer look.

Brakes are kinda important. If brake fluid has escaped (and it sounds like it has) then there's obviously a problem. Rebuild or replace your master just to be safe.

[KRS1]

hah yeah just a little important !...any idea if a cylinder from a gsxr will fit, any additional benefit ?

[Garry]

If your brakes recovered from pumping, its more than likely an air bubble. Bleed your brakes

Sent from my iPhone 3 using ThaiVisa app

I think that would be a smart move, i have a ride this weekend in canyon country and dont want to go flying off a cliff... i once had an NSR 150 that did something similar during a drag race, back brakes went out completely and it never did it again.

Any chance the seal is deteriorating and only able to hold a certain amount of pressure? There is a little fluid on the lever where the stub pushes in the piston, but no actual fluid in the area of the piston...strange, maybe i have to take a closer look.

Brakes are kinda important. If brake fluid has escaped (and it sounds like it has) then there's obviously a problem. Rebuild or replace your master just to be safe.

A rebuild can't hurt, meaning a seal kirt change and bore & piston condition check. Believe it or not high fluid & air pressures can cut O-rings if the medium is allowed to seap past the O-ring. I've seen it happen on aircraft hydraulics, but fortunately aircraft have double, triple redundant systems. Haven't seen that on a bike yet.

[Garry]

What kind of bike??

2005 SV 650s

Im thinking about replacing it with a sv 1000, or a 2008 gsxr 600...

I know where there is a fairly mint K9 (GSXR1000) for sale. If I had the money, I would buy it.

[KRS1]

Im still stateside or else id check it out

I checked out some rebuild kits, looks like its going to run about $35 plus shipping. I wonder though if i can just get the seal if thats all thats bad.

Edited September 12, 2012 by KRS1

[yankee99]

I agree that a rebuild is in order. A air pocket should not just appear for no reason....The kits are cheap enough to save your life...

[KRS1]

Anyone know if a cylinder from a gsxr will give any additional improvement? or the cylinder from any other bike that has the same fittings contributing to improvement?

[BigBikeBKK]

Anyone know if a cylinder from a gsxr will give any additional improvement? or the cylinder from any other bike that has the same fittings contributing to improvement?

The important thing is that you use a master cylinder that will work with your brake calipers.

If you radically mismatch your master cylinder and calipers you can really mess up your brakes.

Basic rules:

If you INCREASE the size of the master you will LOSE braking force.

If you DECREASE the size of the master you will GAIN braking force.

You don't want to go too far in either direction or you can end up with brakes that either don't work properly or brakes that will lock up your wheels way too easily.

If you want to install a different size master cylinder you probably ought to calculate the hydraulic ratio between your master cylinder and your calipers.

A quick explanation of Hydraulic Advantage (aka, why hydraulic brakes work so well):

When you squeeze the brake lever you are forcing brake fluid down the brake lines to the calipers.

The bore of the master cylinder is always much smaller than the combined bores of all the pistons in your brake calipers.

When you squeeze your brake lever, the pistons in the calipers only move a little bit (small force and big action at the master produces small action and big force at the pistons)- this is hydraulic advantage and explains how hydraulic brakes work- small force at the master cylinder creates very strong force at the calipers.

Here's where it gets a little confusing and counter-intuitive:

If you increase the size of the master cylinder, you will REDUCE the power of your brakes. Yes, with a bigger master cylinder, you will have to squeeze HARDER to get the same braking force at the calipers. This is because you are reducing the hydraulic advantage you have over the calipers. Conversely, if you decrease the size of your master cylinder you will increase the power of your brakes.

Now, to make sure that your master cylinder will actually work with your calipers you need to do some math.

If you are going to play with different master cylinders you need to work out the surface area of your caliper pistons and divide it by the area of your master cylinder piston to determine your brake ratio.

That math is beyond me but maybe Dave can help you out with it.

OR, just look at the master cylinder that is on your bike. There should be a number stamped on it somewhere. Most Japanese bikes use 14mm Nissin master cylinders. If that's what's on your bike just compare it to the GSXR master you want to replace it with and you'll know if you are going up or down in size and what changes to expect in your brakes.

Good luck! Let us know how it goes!

[dave_boo]

I think someone asked me to help with some math.

Tony's explaination was a good start. But we need to also consider mechanical leverage. Obviously the first place you get that will be at the lever (hence their name). Using a longer lever usually translates into more force applied. Usually because depending on where the fulcrum is you can have similar or even lesser force applied. Measuring both levers, assuming your also putting new ones on, and doing the simple "distance from end to fulcrum" / "distance from fulcrum to master cylinder connector" ratio will let you compare the differences there. HOWEVER, in reality, nobody is going to grip their levers at the end and the force from your hand closing will be distributed (unevenly) over the width of your hand.

I think that Tony's explanation can also use a bit of clarifing. Hydraulics don't magically increase force. Any more than block and tackle, levers, or gearing does. In all those instances, to increase force you need to increase distance. The block and tackle requires more rope, the lever a greater distance traveled on the applied force end, and in gearing more turns of the force applier. The same thing happens with hydraulics. Having a the same size piston on each end would require the same force to be applied as will be applied. However, going to a smaller piston reduces the force applied....if you're willing to have longer travel.

So, on to the math. We'll assume that you have a 15mm cylinder. We all remember that area = pi*r². 3,1416*7,5²=176,715mm². Go to a 14mm cylinder and you're looking at an area of 153.938mm². One would assume that it meant the 14mm cylinder would than require 87% of the braking force as your old one. However, in actuality, if you're not moving the smaller piston the same distance would not move the calipers the same distance as your old cylinder. The actual clamping force will be much greater, but the caliper pistons will not move as far as you'd be moving a smaller amount of fluid. As Tony stated, you're going to need to know the caliper piston sizes. I couldn't find that information on wikipedia, but will be happy to provide you with the formula if you're really interested in it as it is very simple.

[wantan]

KRS1, i can give you a very easy and safe formula: Go to your Suzuki dealer and get the original spareparts

The next owner of the bike sure will like such easy solution too.

[eezergood]

I think someone asked me to help with some math.

Tony's explaination was a good start. But we need to also consider mechanical leverage. Obviously the first place you get that will be at the lever (hence their name). Using a longer lever usually translates into more force applied. Usually because depending on where the fulcrum is you can have similar or even lesser force applied. Measuring both levers, assuming your also putting new ones on, and doing the simple "distance from end to fulcrum" / "distance from fulcrum to master cylinder connector" ratio will let you compare the differences there. HOWEVER, in reality, nobody is going to grip their levers at the end and the force from your hand closing will be distributed (unevenly) over the width of your hand.

I think that Tony's explanation can also use a bit of clarifing. Hydraulics don't magically increase force. Any more than block and tackle, levers, or gearing does. In all those instances, to increase force you need to increase distance. The block and tackle requires more rope, the lever a greater distance traveled on the applied force end, and in gearing more turns of the force applier. The same thing happens with hydraulics. Having a the same size piston on each end would require the same force to be applied as will be applied. However, going to a smaller piston reduces the force applied....if you're willing to have longer travel.

So, on to the math. We'll assume that you have a 15mm cylinder. We all remember that area = pi*r². 3,1416*7,5²=176,715mm². Go to a 14mm cylinder and you're looking at an area of 153.938mm². One would assume that it meant the 14mm cylinder would than require 87% of the braking force as your old one. However, in actuality, if you're not moving the smaller piston the same distance would not move the calipers the same distance as your old cylinder. The actual clamping force will be much greater, but the caliper pistons will not move as far as you'd be moving a smaller amount of fluid. As Tony stated, you're going to need to know the caliper piston sizes. I couldn't find that information on wikipedia, but will be happy to provide you with the formula if you're really interested in it as it is very simple.

Well thats what I was thinking anyway!

[Lickey]

The bike doesnt look very old, but if youve been away a few months its more likely a semi-seized piston in a caliper, suddenly mowing from the extra force [as you said] you put on the lever,

On an older bike i would have suggested wheel bearings, seized floating disc and sticky calipers,

[KRS1]

Tony and Dave thanks for writing all that out...im going to check out some alternatives.

The steering was locked to the left, i was on the right of the bike, lever was pulled in, bike started to tip over to the left so i had to pull back to the right. At that moment when the bike tipped to the left i strengthened the grip on the brake, and at that moment added about an additional 100lbs of force to the brake lever do to the bikes weight tipping over and pulled the bike back up.

Guess i dont know my own strumpth....where's the muscle smiley when you need one.

[dave_boo]

Tony and Dave thanks for writing all that out...im going to check out some alternatives.

The steering was locked to the left, i was on the right of the bike, lever was pulled in, bike started to tip over to the left so i had to pull back to the right. At that moment when the bike tipped to the left i strengthened the grip on the brake, and at that moment added about an additional 100lbs of force to the brake lever do to the bikes weight tipping over and pulled the bike back up.

Guess i dont know my own strumpth....where's the muscle smiley when you need one.

[BSJ]

A kit at 35 bucks and a couple of extra bucks for brake fluid is pretty cheap insurance.