Disc Sizes

[A1Foxxy]

Hi All, I am very new to ebikes and want to save money when I can. I am a bit confused about this Disc size front and back of the bike. On the calipers there are two different sizes (
F160 R140 F180 R160 . So if I was to buy a pair of calipers do I need the same size disc's or what it says on the calipers or can I have the same size front and rear. Please help!!!!

 

[Az.]

What are you trying to do? Upgrade brakes on your bike? What bike? What brakes are there already?

Disc Brake Guide - Merlin Cycles UK

www.merlincycles.com

Quite often rotors on front wheel are bigger, because front wheel provide more stopping power.
F180 R160 means front rotor is 180mm and rear is 160mm, but it is also normal to have same size rotors on both wheels.

Usually everything what is required (including rotors) already is installed on a bike, and you replace brakes only.

 

[matthewslack]

If you pick a brand name and look at their range, you will probably soon understand all you need to know!

Start with Hope - the brand, not the sibling of Charity.

There are different mount styles, post mount and flat mount the most common. Flat are often front or rear specific, post usually either end. Flat for modern road frames, post for mountain bikes. You probably don't need to know about ISIS.

The numbers are disc diameter in mm.

You can get standard adapters that go between caliper and frame mount to allow use of a larger disc.

Frame mount and fork mount set the minimum disc size you can use, with a caliper of the right mount type, and no adapter.

Look at pictures, then go round looking at bikes, as unsuspiciously as you can, repeat until clear.

 

[saneagle]

Hi All, I am very new to ebikes and want to save money when I can. I am a bit confused about this Disc size front and back of the bike. On the calipers there are two different sizes (
F160 R140 F180 R160 . So if I was to buy a pair of calipers do I need the same size disc's or what it says on the calipers or can I have the same size front and rear. Please help!!!!

The caliper has to fit on whatever size disc you have. They do that by having an adapter between the caliper and the frame or fork. There are adapters of every size so that your caliper will always fit. You can't always go by the numbers. The calipers normally come with adapters. When you come to fit it and you find that the caliper is too high or low, you can buy an adapter the next size up or down for a few quid. You can also use washers to lift it up a bit, or grind the adapter down a bit if the adjustment needed is only a few mm.

MTB Rotor Brake Caliper Mount Adapter Front Rear PM IS 160mm 180mm 203m Air Bike | eBay

Bicycle tools & Accessories. Suitable for mountain bikes, touring bikes, folding bikes, etc. Sound & Vision. Made of high quality aluminum alloy, high strength, light weight, easy to install, simple and practical.

www.ebay.co.uk

 

[AndyBike]

Hope technology(made in Barnoldswick) also has a chart thats quite easy to navigate as it gives the minimum starting size, which in most cases for many forks is 160mm*

https://www.hopetech.com/_repository/1/documents/BrakeAdaptorChart2021.pdf

Unless its a higher end fork, in which case the starting point is 180mm. But for the Suntour Mobie - I believe that is 160mm

TAKE NOTE on this chart it is showing forks that it might not be compatible with. But it states there what it is or is not for.

Cheapest way to improve your braking performance is to increase the rotor size. And in my own opinion(which may differ from others) a good set up is 200mm front and rear. I say this because most mid drive ebikes with large batteries tend to be in the starting weight of 50lb, plus of course your body weight and any luggage(panniers) or shopping you are carrying.

 

[Raboa]

Look at the disk rotor, it's size should in the rotor itself.

 

[SkyMonkey]

I have just installed a Bafang BBS01b 250w motor and 20Ah battery to my 2007 Kona road tourer, and it now weighs 22kg (~48lbs).
The extra weight and the poor condition of the old original mechanical Avid BB7 Road brakes, made me decide to buy new BB7 Road S callipers and uprate the front rotor from 160mm to 180mm.
The new calliper and larger diameter front disc is most confidence inspiring.
But, the new 160mm rear seems woeful now in comparison, so another 180mm rotor and bracket on the way.

Brackets are labelled for the additional front rotor diameter they add, compared to the standard minimum (+0mm or directly mounting) for that frame or fork, e.g. +20mm, +40mm, etc.
Calliper mounting brackets can be used front or rear, but the bracket will allow 20mm less rotor diameter on the rear than stated.
The arrow or triangle on a bracket indicates the bracket is installed with the arrow pointing upwards.

My Kona has IS (International Standard) mounts front and rear, but the BB7 is a Post mount calliper.
So they need IS to Post adapter brackets.
The old IS mount adapter brackets for two 160mm rotors were +0mm F, and +20mm R.
The new IS mount adapter brackets for two 180mm rotors are +20mm F and +40mm R.

One advantage of same size discs front and rear is that if you suffer a damaged rotor when out on the trail/road, with the right multi-tool, you can get home with at least a working front brake (i.e. the one that does the most of the work).

This article may help clarify the matter.
Note the CPS washer sets used on some mountings.
They help when the mating surfaces of the mount plate and bolt head are not parallel.
They can also help with setting the calliper parallel to the rotor.

How To Choose The Right Brake Mount

So you've bought a new set of brakes or some larger rotors to install on your bike. It's as simple as just bolting them on and hitting the trails right? Well, not really. There are a few things to consider when installing different sized rotors and it's easy to get a little bamboozled by all the...

www.mtbdirect.com.au

 

[saneagle]

I have just installed a Bafang BBS01b 250w motor and 20Ah battery to my 2007 Kona road tourer, and it now weighs 22kg (~48lbs).
The extra weight and the poor condition of the old original mechanical Avid BB7 Road brakes, made me decide to buy new BB7 Road S callipers and uprate the front rotor from 160mm to 180mm.
The new calliper and larger diameter front disc is most confidence inspiring.
But, the new 160mm rear seems woeful now in comparison, so another 180mm rotor and bracket on the way.

Brackets are labelled for the additional front rotor diameter they add, compared to the standard minimum (+0mm or directly mounting) for that frame or fork, e.g. +20mm, +40mm, etc.
Calliper mounting brackets can be used front or rear, but the bracket will allow 20mm less rotor diameter on the rear than stated.
The arrow or triangle on a bracket indicates the bracket is installed with the arrow pointing upwards.

My Kona has IS (International Standard) mounts front and rear, but the BB7 is a Post mount calliper.
So they need IS to Post adapter brackets.
The old IS mount adapter brackets for two 160mm rotors were +0mm F, and +20mm R.
The new IS mount adapter brackets for two 180mm rotors are +20mm F and +40mm R.

One advantage of same size discs front and rear is that if you suffer a damaged rotor when out on the trail/road, with the right multi-tool, you can get home with at least a working front brake (i.e. the one that does the most of the work).

This article may help clarify the matter.
Note the CPS washer sets used on some mountings.
They help when the mating surfaces of the mount plate and bolt head are not parallel.
They can also help with setting the calliper parallel to the rotor.

How To Choose The Right Brake Mount

So you've bought a new set of brakes or some larger rotors to install on your bike. It's as simple as just bolting them on and hitting the trails right? Well, not really. There are a few things to consider when installing different sized rotors and it's easy to get a little bamboozled by all the...

www.mtbdirect.com.au

I don't want to rain on your parade, but I think it's important to say what I have to in case other people get encouraged by your posting. I'm sure what you've done is an improvement on what you had before, but it cost so much.

You could have bought decent hydraulic brakes for a lot less money, and they would have been significantly better. Cable disc brakes are fundamentally flawed, in that only one pad moves, so the caliper has to bend the disc to grip it. and as the pads wear, the bending becomes more and more, and the braking efficiency goes down until you adjust the fixed pad. Hydraulic brakes are maintenance free apart from replacing the pads every 5000 miles or so.

Note: There are some double-actuated cable disc brakes with moving pads on each side, but I can't remember who makes them, and they're bound to be expensive.

 

[SkyMonkey]

I don't want to rain on your parade, but I think it's important to say what I have to in case other people get encouraged by your posting. I'm sure what you've done is an improvement on what you had before, but it cost so much.

You could have bought decent hydraulic brakes for a lot less money, and they would have been significantly better. Cable disc brakes are fundamentally flawed, in that only one pad moves, so the caliper has to bend the disc to grip it. and as the pads wear, the bending becomes more and more, and the braking efficiency goes down until you adjust the fixed pad. Hydraulic brakes are maintenance free apart from replacing the pads every 5000 miles or so.

Note: There are some double-actuated cable disc brakes with moving pads on each side, but I can't remember who makes them, and they're bound to be expensive.

OK. That is great for an MTB conversion, but I'm not sure you actually read my post.

Mine is is a drop handlebar road bike from 2007, that originally came fitted with BB7 Road discs, that worked fine for many years, in an era before hydraulic road shifters were a thing, and is a 9-speed system (perfect for ebike conversion).
I was really just using my example to impart information about choosing the correct sizings for disc brakes in general.
At no point was I recommending mechanical disc brakes to the OP.
They are just a simple solution for drop bar cable systems.

But I've looked at your recommendations.

The new BB7 Road S callipers and rotors from BikeInn, with new Jagwire brake cables and housings from Amazon came in at about £150. Add on £10 for a 160mm rotor that I will not now be using.
So, a grand total of £160.

To 'Upgrade' to a drop handlebar hydraulic disc brake system would incur the cost of an entire new groupset, because Shimano don't make 9-speed road shifters with hydraulics.
A 12-speed Shimano 105 Di2 is about the cheapest hydraulic set I can find new, and that is discounted to £999.00.
12-speed would mean I would have to buy a compatible set of centre-lock wheels, built with far fewer spokes than is appropriate for loaded touring.
The nearest I can come up with is a rear centre-lock 12-speed Shimano 700c wheels for £512. It does come with only 24 spokes, but heigh ho!
Front wheels are generally cheaper, so call it £400. £900 for a pair.

I now have spent £1900 following your recommendations and have a bike I cannot use for its intended purpose.
But the brakes are fantastic!

 

[saneagle]

OK. That is great for an MTB conversion, but I'm not sure you actually read my post.

Mine is is a drop handlebar road bike from 2007, that originally came fitted with BB7 Road discs, that worked fine for many years, in an era before hydraulic road shifters were a thing, and is a 9-speed system (perfect for ebike conversion).
I was really just using my example to impart information about choosing the correct sizings for disc brakes in general.
At no point was I recommending mechanical disc brakes to the OP.
They are just a simple solution for drop bar cable systems.

But I've looked at your recommendations.

The new BB7 Road S callipers and rotors from BikeInn, with new Jagwire brake cables and housings from Amazon came in at about £150. Add on £10 for a 160mm rotor that I will not now be using.
So, a grand total of £160.

To 'Upgrade' to a drop handlebar hydraulic disc brake system would incur the cost of an entire new groupset, because Shimano don't make 9-speed road shifters with hydraulics.
A 12-speed Shimano 105 Di2 is about the cheapest hydraulic set I can find new, and that is discounted to £999.00.
12-speed would mean I would have to buy a compatible set of centre-lock wheels, built with far fewer spokes than is appropriate for loaded touring.
The nearest I can come up with is a rear centre-lock 12-speed Shimano 700c wheels for £512. It does come with only 24 spokes, but heigh ho!
Front wheels are generally cheaper, so call it £400. £900 for a pair.

I now have spent £1900 following your recommendations and have a bike I cannot use for its intended purpose.
But the brakes are fantastic!

You can get a pair of cable-operated hydraulic calipers for £20, so you don't have to spend £1900. That's ridiculous. I have hydraulic brakes on my carbon Giant TCR road bike. The whole bike was only £900, so I'm not sure how you arrived at £1900 just for the brakes.

I would bet that these give better braking than what you have, as they have two moving pads. They work very well on my folding bike. For only £20, you should try them. They take about 5 minutes to fit:

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

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

Giant TCR Advanced 2 Disc | eBay

Ridden multiple sportives etc and loved it. Giant PR2 wheels. The bar tape and ends need replacing as they are past there best (one of the plugs is missing). My pedals are currently fitted but will be removed.

www.ebay.co.uk

Shimano groupset with hydraulic brakes:

Shimano 105 R7120 Disc Groupset - 12 Speed | Merlin Cycles

Buy your Shimano 105 R7120 Disc Groupset - 12 Speed at Merlin. Free worldwide delivery available on most items!

www.merlincycles.com

£230 for this:

SHIMANO R7020 Groupset 105 R7020 Hydraulic Disc Brake Derailleurs ROAD Bicycle R7020 R7070 ST+BR+FD+RD shifter Brake Front Rear - AliExpress 18

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

 

[pedalfettal]

There is a bullsh!t-baffles-brains thing going on here. My notes:

Single-pistoned disc-brakes:
1. AVID BB7s are single-pistoned cable-disc-brakes (SJS GBP69.99)

Cable Double-pistoned disc-brakes:
2. TRP Spyre are double-pistoned cable-disc-brakes for road bikes (short-pull brake levers) (MERLIN GBP65.00)

3. TRP Spyke are double-pistoned cable-disc-brakes for MTBs (long-pull brake levers) (SPA Cycles ~GBP55.00)

4. ZOOM Double Piston Mechanical Disc Brake Caliper (flea-bay GBP18.50)

Cable-operated hydraulic-actioned disc-brake:
5. ZOOM XTECH HB100 MTB Hydraulic Disc Brake (flea-bay GBP25.00)

Prices per G@@gle today.

I've got #2s on my road bikes and #4 on my folder. I'm 100 kgs and use TEKTRO/TRP green pads on the front and TEKTRO/TRP red pads on the rear.

Option #5 is worth a go - however - longevity is is doubt.

 

[SkyMonkey]

Cheers @saneagle, but although those hydraulic shifter options are cheaper than my costing, they are still 12-speed/centre lock systems, and make the 9-speed, 6-bolt hubs and 36 spoke wheels I have incompatible.
As for the cable pull hydraulics, that is a personal no-go.
I wouldn't trust anything from Aliexpress that is safety critical. Buy cheap, die once.
The ZOOMs were 'MTB' versions too, and will not work with road shifters.
The corrects cable pull Road ones are £30, but only go up to 160mm according to the specs. But a mounting bracket might fix that.

Hydraulic Disc Brakes Gravel Bike | Zoom Hydraulic Bicycle Brakes - Road Bicycle - Aliexpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

I did find a review of the MTB versions that didn't inspire confidence:

ZOOM HB-100: Upgrading cable-operated disc brakes to hydraulic calipers

I'm just wondering if anybody else here has tried upgrading their mechanical disc calipers to hydraulic and what your thoughts are? Are these ZOOM HB-100 hydraulic calipers a good compromise or waste of time? With these it's only the caliper that's hydraulic, so you don't have an oil reservoir...

www.pedelecs.co.uk

Mechanicals do have an advantage over hydraulics of any kind though: ease of repair on the road.
Carry a spare cable and pads and you are safe.
Hydraulic brake failure requires an expert (who will book you in for next month), and specialist equipment & parts.
And a dirt free environment to replace the fluid in.
I know because I have bled and serviced my three MTBs and their Hope & SRAM hydraulic brakes in the past.
It was a ball ache compared to threading a new cable.
Worth it, but a ball ache.

Anyway, the point is moot.
The money is spent.
The customer is happy.

 

[SkyMonkey]

Single-pistoned disc-brakes:
1. AVID BB7s are single-pistoned cable-disc-brakes (SJS GBP69.99)

£37 at BikeInn, but I went for the blingier Road S versions at £51. Rotors separate though.
The CleanSweep 160mm was on offer for £10 when I ordered.

https://www.tradeinn.com/bikeinn/en/sram-avid-bb7-road-mechanical-disc-brake-caliper/137680551/p?queryID=12d7783119cd55ade706045dbf074723&buscador_search

 

[saneagle]

[QUOTE="SkyMonkey, post: 725167, member: 46693"
Mechanicals do have an advantage over hydraulics of any kind though: ease of repair on the road.
Carry a spare cable and pads and you are safe.
Hydraulic brake failure requires an expert (who will book you in for next month), and specialist equipment & parts.
And a dirt free environment to replace the fluid in.
I know because I have bled and serviced my three MTBs and their Hope & SRAM hydraulic brakes in the past.
It was a ball ache compared to threading a new cable.

[/QUOTE]
Hydraulic brakes never need any repair or maintenance other than replacing worn pads every 5000 miles or so. There's no cable to break or go rusty, no adjustment. Nearly all bicycle hydraulic brakes are self-bleeding, so there is no need to do any bleeding procedure. I have hydraulic brakes on all my bikes. In 12 years since I started with them, I've never done any maintenance at all, not even cleaning, except for replacing worn out pads. That's around 30,000 miles. Most of what I read about them from detractors is either pure finection or incompetence. Even Googles AI has it wrong, presumably because it can see all the bleed kits being sold to suckered and YouTube videos done for clicks, especially from cycle workshops that want to con you into paying for non-existent or unnecessary bleeding during your service.

 

[AndyBike]

I know because I have bled and serviced my three MTBs and their Hope & SRAM hydraulic brakes in the past.

Didnt you just flick the levers a couple of times and they magically bled themselves

I'll agree with the above member. Mechanical systems are easier to look after, but hydraulic are quite a simple system, and if you can maintain mechanical, you can maintain hydraulic. They are not 'specialist'
As to going wrong. well that is rarer than is being expressed. Though all brakes can fail through lack of any maintenance, be that canti or high end hydraulic, but that said, im not implying its a monthly task, usually its years between one service and another, and often its down to some problem arising like the pistons have become caked with dirt because the user didnt bother their backside to keep their bike clean.

Bleeding hydraulic requires a highly specialized small spanner and a length of highly specialized plastic tubing.
Oh and you might also need a highly specialized small allenkey, or possibly a highly specialized cross head screwdriver.

 

[Waspy]

Didnt you just flick the levers a couple of times and they magically bled themselves

Speaking from personal experience, it's hard to believe but it's true. I cut and shortened the hose on my Shimano MT200 rear brake. Reconnected the hose, pumped the lever, job done.

 

[saneagle]

Speaking from personal experience, it's hard to believe but it's true. I cut and shortened the hose on my Shimano MT200 rear brake. Reconnected the hose, pumped the lever, job done.

I've done exactly the same. I had even stupidly bought the bleed kit beforehand. It's still unused in my tool chest after 8 years.