Hydraulic Cable Brakes

[saneagle]

What's the make of the brakes? Are they cable (as in a normal brake cable) activated hydraulic disk brakes?
When you buy disk brakes they should come with a plastic shim that fits between the pistons This stops the pistons closing together when doing maintenance.
If the reservoir has a certain amount of oil in it when bought then I would not go by over that amount
If it cable activated then use the barrel adjuster to put more tension on the cable, this will bring the cable attachments closer together on the caliper resulting in the brake lever not requiring so much of a squeeze .

ZOOM XTECH HB100 MTB Hydraulic Disc Calipers Front and Rear Rotor G3 160/180MM MT200 M315 160mm Rotor Hydraulic Brakes for Bikes - AliExpress 18

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The diameter of the pad pistons is about 20mm and the diameter of the actuator piston is about 10mm, which means the ratio of linear movement would be 400:100, but there are two pad pistons, so if the pads wear 1mm, the actuator piston has to move an extra 8mm. If you look at the picture in the listing, then imagine those bellows being 8mm shorter, you can see the problem.

 

[Raboa]

The cable pull on the brakes activates the fluid reservoir system which then pushes against the pistons.
The advantage of this is that it gives you a similar feeling to a full hydraulic system but without so much of the complications of a full system.
If you are not using all of the pads then you do not have enough tension in the brake cable to activate the full capacity of the fluid reservoir.
Adjust the cable tension like you would a v brake, under or overfilling the reservoir system will have a negative effect.
On the caliper body it has a barrel adjuster, your brake lever should have one as well.

 

[saneagle]

The cable pull on the brakes activates the fluid reservoir system which then pushes against the pistons.
The advantage of this is that it gives you a similar feeling to a full hydraulic system but without so much of the complications of a full system.
If you are not using all of the pads then you do not have enough tension in the brake cable to activate the full capacity of the fluid reservoir.
Adjust the cable tension like you would a v brake, under or overfilling the reservoir system will have a negative effect.
On the caliper body it has a barrel adjuster, your brake lever should have one as well.

There is no reservoir. That's the problem. It's a closed system witha fixed volume of fluid.

 

[Raboa]

The reservoir is on the caliper body, when the brake lever is pressed the cable activities a system on the caliper that pushes the oil in the reservoir against the pistons.
That is how it is designed, if the brake lever has too much travel then the problem is with cable tension
I would do this:
1. Fit a new brake cable
2. Fit compression less cable housing
3. Fit new pads
4. Make sure the pads are aligned properly with the rotor
Think of this as a cable only activated system and set up accordingly.

 

[Peter.Bridge]

From @saneagle s links there are 2 distinct designs

Open circuit design (with reservoir) eg Trp hy/Rd, Rush

Close circuit design (without reservoir) eg Zoom HB100s

The close circuit design does not cope well with pad wear

 

[Raboa]

Thanks for pointing that out.

I would look into replacing the outer housing.

 

[saneagle]

There is a adjustment that might buy you a bit of time to keep you going in an emergency, but the adjustment is not enough to deal with another 1mm of pad wear. Like on mormal hydraulic brakes, you can adjust the start point of the actuating piston with a small grub-screw at the end of the piston rod in the actuating lever. You can just see it poking out in the pi tures

 

[Raboa]

In your calculations did you factor in the amount of movement the hydraulic fluid provides. The piston pushes on the hydraulic fluid reservoir, this then makes the fluid move, this movement will make the pistons go outwards.

Thanks for helping the person with the bike, the amount of pad left seems excessive, that's why I think cable tension is a factor.

 

[Tony1951]

The pads cost pennies.

If they can't be adjusted any more, chuck e'm and replace.

The zoomtec brakes are a cheap replacement for much worse performing cable mechanical calipers.

Not Rolls Royce.

Not priced as Rolls Royce.

Mine have done 1150 miles since i fitted them and they are still working. When they start failing, a fiver for two sets of pads won't keep me awake.

 

[saneagle]

The pads cost pennies.

If they can't be adjusted any more, chuck e'm and replace.

The zoomtec brakes are a cheap replacement for much worse performing cable mechanical calipers.

Not Rolls Royce.

Not priced as Rolls Royce.

Mine have done 1150 miles since i fitted them and they are still working. When they start failing, a fiver for two sets of pads won't keep me awake.

Have you looked at how close the lever has come to bottoming out on the body of the caliper? Actually, it's the bellows that become fully compressed first, which makes the bottoming out squishy.

 

[Tony1951]

Have you looked at how close the lever has come to bottoming out on the body of the caliper? Actually, it's the bellows that become fully compressed first, which makes the bottoming out squishy.

No. I will have a look after lunch and report back.

Thanks.

 

[Raboa]

Check the thickness of your disk rotor, the minimum thickness should be stamped on the rotor.

 

[Tony1951]

On the rear brake the gap is about 3mm - not less. As you describe the boot is compressed. It is possible that this is restricting movement of the arm. The front brake has much more arm clearance - easily 5mm. I had actually noticed a slight tailing off in stopping power of the rear brake. This is likely the cause. The front brake is fine.

Since I was looking at them, and had in stock about 7 or 8 pairs of pads, I replaced the rear one which was the most worn. It only took a few minutes.

I would say the replaced pads had about 30 thou of pad still usable, but given the lack of clearance on the actuating arm to the caliper body, it was not worth waiting any longer.

Most of my riding is in the countryside, so generally I am not using the brakes that much as you would in town with start stop riding, but as it is a hilly area, I do use the brakes to temper the speed on downhills. As I wrote to you in a PM a while back, this Argos folder design seems prone to speed wobble at over 30 miles an hour, so on long down hill runs, I use the rear brake to slow it to avoid the risk of it becoming unstable at speed. This is why I have differential rate of wear front and back.

 

[Raboa]

For a "Zoom" brand disk brake, like other disk brakes, you should replace the pad when the friction material is worn down to 3mm or less, though a common guideline is to replace them when they get below 1mm or if a wear indicator is reached. While there is no specific thickness for "Zoom" pads, you can measure the material remaining on the brake pad itself, not including the metal backing plate.

 

[saneagle]

On the rear brake the gap is about 3mm - not less. As you describe the boot is compressed. It is possible that this is restricting movement of the arm. The front brake has much more arm clearance - easily 5mm. I had actually noticed a slight tailing off in stopping power of the rear brake. This is likely the cause. The front brake is fine.

Since I was looking at them, and had in stock about 7 or 8 pairs of pads, I replaced the rear one which was the most worn. It only took a few minutes.

I would say the replaced pads had about 30 thou of pad still usable, but given the lack of clearance on the actuating arm to the caliper body, it was not worth waiting any longer.

Most of my riding is in the countryside, so generally I am not using the brakes that much as you would in town with start stop riding, but as it is a hilly area, I do use the brakes to temper the speed on downhills. As I wrote to you in a PM a while back, this Argos folder design seems prone to speed wobble at over 30 miles an hour, so on long down hill runs, I use the rear brake to slow it to avoid the risk of it becoming unstable at speed. This is why I have differential rate of wear front and back.

View attachment 64408

It would be interesting to see how much effect that adjuster screw has. When I was working on them, I saw it, but I already had it in my head to put more oil in before I started.

Each 1mm of pad wear on both pads will cause the piston to be 8mm further forward. There's no way that the adjuster screw can cope with that, but an adjustment of say 4mm might be possible, which only takes 10 secs and would give you another 500 miles at your wear rate.

 

[Tony1951]

It would be interesting to see how much effect that adjuster screw has. When I was working on them, I saw it, but I already had it in my head to put more oil in before I started.

Each 1mm of pad wear on both pads will cause the piston to be 8mm further forward. There's no way that the adjuster screw can cope with that, but an adjustment of say 4mm might be possible, which only takes 10 secs and would give you another 500 miles at your wear rate.

I wondered when I was checking whether the actuating arm could be loosened and put back on in a slightly different orientation.

I have done that many times over the years with motorbike brake arms on drum brake systems to get a better mechanical action on part worn, rear brake shoes. You want no less than a 90 degree angle between the actuating rod and the brake arm on a rear motorbike mechanical brake. If the actuating arm was working on a splined shaft that might work on the zoomtec actuating arm. But most likely the arm will be on a squared shaft because it is so small, so it's not likely to be an option.

In the end, having so many sets of pads, it was a no brainer to just dump the old pads and replace them.



By the way, I just checked Ali Express and the black calipers are going for £16 a set post free. That's an amazing price.

Hydraulic Brake Mt200 Bike | Hydraulic Disc Brakes Zoom | Mt200 Front Hydraulic Brake - Bicycle Brake - Aliexpress

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[saneagle]

I wondered when I was checking whether the actuating arm could be loosened and put back on in a slightly different orientation.

I have done that many times over the years with motorbike brake arms on drum brake systems to get a better mechanical action on somewhat worn rear brake shoes. You want no less than a 90 degree angle between the actuating rod and the brake arm on a rear motorbike mechanical brake. If the actuating arm was working on a splined shaft that might work on the zoomtec actuating arm. Bit mot likely the arm will be on a squared shaft because it is so small.

In the end, having so many sets of pads, it was a no brainer to just dump the old pads and replace them.



By the way, I just checked Ali Express and the black calipers are going for £16 a set post free.

Hydraulic Brake Mt200 Bike | Hydraulic Disc Brakes Zoom | Mt200 Front Hydraulic Brake - Bicycle Brake - Aliexpress

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Aliexpress pricing is a bit weird. When I click on that link, they're showing as £29.39, though I did see them for about £24 yesterday. I've noticed that if you look at an item, then disregard it, it pops up down the page at a lower price on the next or near future item that you look at, and if you look at that one and disregard it, you can often find it at an even lower price. I'm getting pretty good at buying their stuff now. I can often shave at least 30% off their prices.

I've just seen on that same page as your link, in the ads at the bottom of the page, they're offered at £23.59.

I just got three 10 magnet pedal sensors for £5.10 inc. shipping.

 

[Tony1951]

Aliexpress pricing is a bit weird. When I click on that link, they're showing as £29.39, though I did see them for about £24 yesterday. I've noticed that if you look at an item, then disregard it, it pops up down the page at a lower price on the next or near future item that you look at, and if you look at that one and disregard it, you can often find it at an even lower price. I'm getting pretty good at buying their stuff now. I can often shave at least 30% off their prices.

I've just seen on that same page as your link, in the ads at the bottom of the page, they're offered at £23.59.

I just got three 10 magnet pedal sensors for £5.10 inc. shipping.

Did you check the price of the different colours?

You probably did but when I first load the page it shows the price of a disk which was a bit over a fiver, but the first caliper is a fancy purple one and that is shown as about £29, but if you click the black one it is £16.80 or something like that.

You are right of course that the price varies if they are trying to tempt you. Amazon does that too.

 

[saneagle]

Did you check the price of the different colours?

You probably did but when I first load the page it shows the price of a disk which was a bit over a fiver, but the first caliper is a fancy purple one and that is shown as about £29, but if you click the black one it is £16.80 or something like that.

You are right of course that the price varies if they are trying to tempt you. Amazon does that too.

Yes, I checked the black one first.

I hate it when they show a linked listing for what you want at a very low price, but when you click on it, the price is for bag to put it in or something like that, and the actual item is expensive. As a matter of principle, I just close down the page when I see that if I'm not desperate for the item.

 

[Tony1951]

Yes, I checked the black one first.

I hate it when they show a linked listing for what you want at a very low price, but when you click on it, the price is for bag to put it in or something like that, and the actual item is expensive. As a matter of principle, I just close down the page when I see that if I'm not desperate for the item.

My pet hate is when they show something you want at a brilliant price, but when you click on it you get a message saying they can't post it to your location.

I wonder why they will sell me that caliper for £16.70 but for you it is £29?