what size brake disc pads/

[MikeS]

Hi Everyone - long time since I posted.
My nephew is very good with bike maintenance so he serviced my Halfords Crossfuse for me, and I thought I had some new rear disc pads for him to replace. But he said they were 'wrong' I think he expected to see circular pads for the rear barkes because ceratinly the hydraulic cylinder and housing LOOK circular. The ones I must have bought years ago are genuine Shimano B01S .... are these the correct ones, because if so I will try and fit them tomorrow? Here's a picture of the rear brake itself.
Thanks
Mike

 

[matthewslack]

They won't be circular, and the B01S fits many Shimano calipers. Easy to check, although removing wheel is needed for a good look. Look from the underneath view and you should see the straight sides.

B01S work fine, but have been superceded twice by B03S and now B05S. Longer lasting is the main difference.

 

[AndyBike]

Theres a number on the brake caliper that would identify which pad it is supposed to get.

It will start BR-M.... for example BR-M200

 

[saneagle]

Hi Everyone - long time since I posted.
My nephew is very good with bike maintenance so he serviced my Halfords Crossfuse for me, and I thought I had some new rear disc pads for him to replace. But he said they were 'wrong' I think he expected to see circular pads for the rear barkes because ceratinly the hydraulic cylinder and housing LOOK circular. The ones I must have bought years ago are genuine Shimano B01S .... are these the correct ones, because if so I will try and fit them tomorrow? Here's a picture of the rear brake itself.
Thanks
Mike
View attachment 63574

You know they're the right ones when they're the same shape as the ones you have. It takes about one minute to look.

 

[Luccguire]

Hi Mike — the Shimano B01S pads are actually a common type, but whether they fit depends on your brake caliper model, not just the shape of the housing. Can you check the exact caliper model (usually printed on it)? If it’s something like Shimano BR-M375 or similar, B01S might fit. Otherwise, best to confirm before trying to install them.

 

[Sturmey]

There are many types. I have four types on various bikes in the family, but my bike uses the top left type.

 

[MikeS]

Hi Mike — the Shimano B01S pads are actually a common type, but whether they fit depends on your brake caliper model, not just the shape of the housing. Can you check the exact caliper model (usually printed on it)? If it’s something like Shimano BR-M375 or similar, B01S might fit. Otherwise, best to confirm before trying to install them.

Thanks guys - I bought a pair of B05S from Halfords for just £5.99 which I thought was worth a risk. And they fitted fine. brake is back to normal-ish, but I suspect I need to do something with the fluid as there will be no 'pull' left when these pads are only half worn if the last lot are anything to go by. I was surprised that Halfords didn't sell the shimano brake bleed kit.
Mike

 

[Waspy]

Thanks guys - I bought a pair of B05S from Halfords for just £5.99 which I thought was worth a risk. And they fitted fine. brake is back to normal-ish, but I suspect I need to do something with the fluid as there will be no 'pull' left when these pads are only half worn if the last lot are anything to go by. I was surprised that Halfords didn't sell the shimano brake bleed kit.
Mike

No need to bleed your brakes, just adjust the brake lever reach screw.

 

[saneagle]

£0.60 per pair from here, where I get mine from:
1-10pairs Bicycle Brake Pad Resin Disc Pads For SHIMANO B01S Wear-resistant MTB Bike Hydraulic Brake Pad B03S B05S Brake Parts - AliExpress

Shimano hydraulic brakes are self-bleeding, so don't waste your money on a bleeding kit. You only need that if you fit a new hose. Even then, it's not necessary if you assemble the brake right.

Some hydraulic brakes go spongy or don't operate after you turn the bike upside down to service a wheel or whatever. In that case, just press the lever a few times to bleed the air back into the reservoir. You can mitigate that a bit by having sufficient fluid in the reservoir, but do not over-fill or else your brakes will lock on when the fluid expands due to heat when you use the brakes.

 

[Raboa]

AI says

No, Shimano hydraulic brakes are not self-bleeding. While they are designed with a bladder in the reservoir that helps direct air bubbles towards the bleed port, they still require periodic bleeding to remove air and maintain optimal performance. If you notice spongy feeling brakes or a low brake lever engagement point, it's likely time to bleed your brakes according to bike shops.

You can do a gravity bleed incase of using syringes but you still need certain equipment.

Shimano rotors need replacing when they are 1.5mm thick and the pad material ( a disk brake pad is made of a backing and brake pad) need replaced when they wears down to 0.5 mm or less.

Clean the rotors and pads with isopropyl alcohol regularly.

 

[Waspy]

Here we go...

 

[saneagle]

AI says

No, Shimano hydraulic brakes are not self-bleeding. While they are designed with a bladder in the reservoir that helps direct air bubbles towards the bleed port, they still require periodic bleeding to remove air and maintain optimal performance. If you notice spongy feeling brakes or a low brake lever engagement point, it's likely time to bleed your brakes according to bike shops.

AI knows about as much about Shimano brakes as the ginger cat walking through my front garden right now. Many Shimano brakes don't even have a bladder in them. I suppose you could ague that what it said is correct because it qualified the comment with "according to bike shops", but, of course, many bike shops see a sucker when someone comes in with spongy brakes.

 

[Raboa]

I am basing my comment on
2. Volunteering at a bike charity and discussing this with qualified mechanics with years of experience.
2. Shimano dealers manuals
3. Hydraulic brake systems are closed systems, if hydraulic self bleed the air would have to escape from an open port, if this was the case it would not be a closed system.
Yes, not all Shimano hydraulic brakes have an air bladder.
Shimano hydraulic brake air bladders compensate for fluid expansion due to heat and pad wear, maintaining consistent brake lever feel. They act as a reservoir, allowing fluid to expand into the bladder without affecting brake performance. As the brake pads wear, the bladder also allows for the extra fluid needed to maintain proper lever feel.

Here's a more detailed explanation:

• Fluid Expansion:
  When brakes are applied, the brake fluid heats up and expands. The bladder in the reservoir allows this extra fluid to move into the bladder, preventing it from creating pressure that would affect brake performance.
  
  
• Pad Wear Compensation:
  As brake pads wear down, the pistons in the brake caliper need to move further out to contact the rotor. The bladder provides the extra fluid required to maintain the same lever feel, even as the pads wear.
  
  
• Open System:
  Shimano hydraulic brakes utilize an open system, meaning the reservoir and bladder allow for the addition or removal of fluid as needed.
  
  
• Consistent Lever Feel:
  By compensating for fluid expansion and pad wear, the bladder ensures a consistent brake lever feel, preventing a spongy or soft brake lever.
• 
  
• If Shimano hydraulic brakes have an air bladder why do they still need bleed.
• 
  
• Shimano hydraulic brake systems still require bleeding despite having an air bladder because the bladder's primary function is to compensate for fluid expansion due to temperature changes and pad wear, not to remove air introduced into the system. Air can still enter the system through various means, and when it does, it needs to be removed through bleeding to ensure proper brake function.

 

[saneagle]

I am basing my comment on
2. Volunteering at a bike charity and discussing this with qualified mechanics with years of experience.

And how many hydraulic brakes did you actually work on in said charity, and how many times did you try using the self-bleeding procedure? I guess not a lot judging by your comments about bladders. Are you sure that your research isn't telling you about motorbike brakes?

BTW, you can try it on your own bike. Turn it upside down, work the brake lever a few times until there's no resistance. Turn it back up the right way to see that the lever does nothing, then keep operating the lever as you feel how it slowly comes back to normal.

 

[Waspy]

I am basing my comment on
2. Volunteering at a bike charity and discussing this with qualified mechanics with years of experience.
2. Shimano dealers manuals
3. Hydraulic brake systems are closed systems, if hydraulic self bleed the air would have to escape from an open port, if this was the case it would not be a closed system.
Yes, not all Shimano hydraulic brakes have an air bladder.
Shimano hydraulic brake air bladders compensate for fluid expansion due to heat and pad wear, maintaining consistent brake lever feel. They act as a reservoir, allowing fluid to expand into the bladder without affecting brake performance. As the brake pads wear, the bladder also allows for the extra fluid needed to maintain proper lever feel.

Here's a more detailed explanation:

• Fluid Expansion:
  When brakes are applied, the brake fluid heats up and expands. The bladder in the reservoir allows this extra fluid to move into the bladder, preventing it from creating pressure that would affect brake performance.
  
  
• Pad Wear Compensation:
  As brake pads wear down, the pistons in the brake caliper need to move further out to contact the rotor. The bladder provides the extra fluid required to maintain the same lever feel, even as the pads wear.
  
  
• Open System:
  Shimano hydraulic brakes utilize an open system, meaning the reservoir and bladder allow for the addition or removal of fluid as needed.
  
  
• Consistent Lever Feel:
  By compensating for fluid expansion and pad wear, the bladder ensures a consistent brake lever feel, preventing a spongy or soft brake lever.
• 
  
• If Shimano hydraulic brakes have an air bladder why do they still need bleed.
• 
  
• Shimano hydraulic brake systems still require bleeding despite having an air bladder because the bladder's primary function is to compensate for fluid expansion due to temperature changes and pad wear, not to remove air introduced into the system. Air can still enter the system through various means, and when it does, it needs to be removed through bleeding to ensure proper brake function.

Mate, I am definitely not trying to dispute your experience, but here is my personal experience for anyone who needs it:

I have Shimano MT200 hydraulic brakes.

Both hoses were too long.

I disconnect them at the master cylinder, cut them shorter, fitted a new barb and olive, reconnected them, pumped the levers a few times, everything works perfectly. No bleeding required.

I would never dream of doing this on a car or motorbike without bleeding, but for some reason on Shimano pushbike brakes it just works.

 

[chris_n]

The reason bike brakes will self bleed (usually) is because air is lighter than brake fluid and will always try to find the highest point. Sometimes with rear brakes you have to put the bike on an angle in a bike stand so that the hose runs consistently upwards, sometimes you need to rotate the brake lever to be at the highest point. My mate has a bike shop and never uses syringes on 'normal' systems, he screws a pot with brake fluid in into the upper bleed port, the pot has a small 'jiggler' in it which stops the fluid leaking when not on the bike. If you fit this pot and operate the brake lever if there is air in the system it will bubble up through the pot on the return stroke. Using this method the only time I have seen any problems was when an apprentice was fitting a new part (can't remember if it was a caliper or hose) couldn't get the flow to start, loosening the bleed screw on the caliper was enough to get the fluid moving then it could be closed and finished just using the pot. The only reason the pot is actually required is to allow fluid to be added without leaving a mess.

 

[Raboa]

Thanks for the replies.

You can also what is known as burping the brakes.

Sometimes this is not enough and a bleed is required.

Shimano hydraulic brake bladder article

NSMB.com - Shimano Brake Bleed and Bladder Repairs

Dismantling master cylinders on Shimano brakes in the name of repairs with the end goal of powerful, consistent braking.

nsmb.com