Log in:  

Register

Brakes.

Whether you are wondering how to true a wheel, how to fix that clicking sound or simply maintain your bike for the long haul, the Workshop & Maintenance forum is your one-stop online mechanic shop.

Moderator: Pricey_sky

Brakes.

03 Sep 2015 01:41

While there are dozens of different types of bike brake the ones you need to worry about fall under two main categories: rim brakes and disc brakes.

• Rim brakes, as the name suggests, use the rim of the wheel as a braking surface, slowing down the bike when the brake pads are compressed against it. Rim brakes are widely in use on BMX, road and city bikes and are favoured for their light weight and mechanical simplicity. There are a number of different types, the two main ones being caliper and cantilever brakes, with each one offering advantages and disadvantages depending on what type of riding you are doing.

Image

• Disc brakes are similar to the kind of brakes found on motorcycles. Instead of using the rim as a braking surface they use a circular metal disc mounted on the hub of the wheel. This disc rotates through a caliper, which contains the brake pads. Squeezing the brake lever applies the pads to the rotor, slowing down the bike. Disc brakes are either mechanical, where the caliper pistons are activated with a wire cable, or hydraulic, where compression of hydraulic brake fluid in sealed hoses is used to move the pistons and pads.
Because the braking surface is away from mud and wet (leading to improved braking performance as well as prolonging the life of your rim), disc brakes have all but replaced rim brakes as standard issue on MTBs. As technology advances and materials become lighter, disc brakes for road and Cyclo-X bikes are now increasingly becoming an option.

Image

MOUNTAIN BIKE DISC BRAKES

Once the preserve of only high-end bikes and carrying a hefty price premium as well as a weight penalty, disc stoppers are now standard on all but the most budget bikes.

Meanwhile at the upper end of the market, advances in materials technology have resulted in reduced weight and improved performance for the most demanding riders and racers across all disciplines.

How do disc brakes work?

As with v-brakes, all disc brakes are operated with a handlebar-mounted brake lever. At the business end of the brake system is the brake caliper, with front brake calipers mounted close to the bottom left leg of your forks, and back brakes bolted securely to the rear left seatstay. Attached to the hub of each wheel is a circular metal rotor, the outer strip of which runs through the caliper and is your braking surface.
While there are differences in how individual brake systems work the principles are generally the same. Inside the caliper are a number of pistons – usually two, one for each side of the rotor – to which the brake pads are attached. Pulling on the levers will result in the pistons moving inwards, towards the rotor, and the brake pads making contact with its surface. The resulting friction is what will bring your bike to a controlled halt in all conditions.

Why disc brakes?

Disc brakes carry two main advantages over v-brakes or cantilevers.
Firstly, by moving the braking surface from the rim of the wheel to a hub-mounted rotor, they keep it clear of the inevitable water and mud that are part and parcel of the MTB experience. This means a vast improvement in stopping power and reliability when things turn damp – compared to the ‘haul-and-hope’ experience that is v-brakes in wet weather – but also an end to having your rims and rubber pads constantly chewed by a grinding paste of gritty crud, thus lengthening the life of your kit.
Secondly, disc brakes offer great improvements in terms of pure performance over their rim-brake rivals, with much improved levels of stopping power increasing according to brake type, rotor size and more. While v-brakes still have their fans, most bikers have now embraced the multiple performance and longevity advantages of the modern generation of disc anchors.

Brake type

There are two main types of disc brakes – mechanical (in which the piston is activated by a wire cable, like on a caliper or v-brake) and hydraulic (where the piston is activated via hydraulic fluid in a sealed hoses, like the brakes on your car).
• Mechanical discs: These are cheaper than hydraulic disc brakes and to v-brake users their simple steel cable operation can appear less daunting than hydraulics when it comes to repair and maintenance. While good mechanicals are on the market, in general terms they are outperformed by hydraulics.

Image

• Hydraulic discs: These have hoses filled with incompressible brake fluid meaning that any movement at the lever is transferred immediately to the pistons. This means not only more power, but more control when compared to open cable systems which can stretch and become clogged with grit and water.

Image

Disc brake aficionados looking to upgrade to a better set of stoppers are spoilt for choice when it comes to aftermarket options. Most major manufacturers have radically overhauled their brake offerings in recent years, meaning top-end lightweight trail anchors are now offering the stopping power that was once the sole preserve of heavyweight DH-only units. The best of these give most riders more than enough for their needs while at the same time shaving considerable weight.
However for full-on DH, Enduro and Freeride, you can choose to boost your stopping not only by increasing your rotor size, but also be investing in some heavy duty multi-piston caliper systems. Instead of the two opposing pistons (‘pots’) present in most calipers, four- or even six-pot units can not only provide ultimate stopping power but also minimise the risk of your brakes losing power when they overheat under heavy and sustained use, causing the brake fluid to boil in the system (‘brake fade’).
Eliminating brake fade by improving heat dissipation is also the reasoning behind a new generation of vented and/or ‘floating’ rotors. The former consist of two parallel discs with a space in between, allowing cooling air to flow between the two sides of the braking surface, while floating rotors feature a stainless steel outer braking surface bolted to an aluminium central carrier, or ‘spider’. This two-part rotor stays cooler longer, and is also lighter than an all-steel equivalent.
Other upgrade options include braided hoses, designed to increase brake power by cutting down on energy loss through hose expansion.

Mountain Bike Disc Brakes in Depth:-

Compatibility - frame and forks

First thing to consider if upgrading to disc brakes is whether your frame, forks and wheels can take them. Nowadays most MTB frames and forks will have disc mounts as standard, but you will want to check if you are kitting out older models. If disc mount tabs aren’t present, you do have the option of purchasing bolt-on adaptors, but this is not an ideal solution. Something else to consider is facing your frame’s brake mounts – removing any excess paint or metal left over from the manufacturing process to make sure the mounts are perfectly parallel. This can ensure that calipers are mounted perfectly for optimum performance, but it’s generally a job for a professional workshop.

There are two main types of disc mounts for attaching calipers to frames and forks, International Standard (where the bolt holes are positioned perpendicular to the frame) and Post Mount (where the holes are parallel to the frame). With IS mounts an adaptor is generally needed to fit the caliper, while a Post Mount enables it to be bolted directly on. Most frames will be equipped with IS mounts for the rear brake, but more and more fork and brake manufacturers are finding the Post Mount system more convenient for the forks.

NOTE: Before buying your brakes make sure to check which mounts are present on your frame and forks, and choose your stoppers accordingly. Some brake manufacturers will offer the products with a choice of mount types, but if not you may have to buy an adaptor in order to fit your stoppers.

Compatibility – wheels

Your wheels will also need to be disc-ready in order to attach the rotors. If they do not have hubs with mounts to attach a rotor, you are looking at rebuilding with disc hubs, or as may be more practical, a new set of wheels.
There are two main standards for rotor mounting, six-bolt and centrelock. As the name suggests, six-bolt systems have hubs with six evenly-spaced holes to bolt on a matching rotor. Rotor bolts generally use Torx heads so you will need to make sure you have a Torx tool to tighten or loosen them – don’t try to fudge the job with an Allen key or you will risk stripping the bolts.

The Centrelock system used by Shimano foregoes rotor bolts in favour of a splined hub-rotor interface secured with a locking ring (special tool needed). This is claimed to reduce installation time but it does put limits on mixing and matching hubs and brakes as most other manufacturers stick with the six-bolt system. Again however, adaptors are available to mount six-bolt rotors to Centrelock hubs, and vice-versa.

Rotors - width

Each caliper is designed to take a specific size of rotor, in terms of both diameter and thickness. Whereas you can generally vary the diameter size of the rotors with the use of adaptors, different manufacturers and brake models will use marginally thicker or thinner rotors. Although the differences in thickness are tiny, you’re best to avoid mixing and matching rotors with calipers if you want to avoid problems with brake rub (where the pad is constantly touching the rotor surface, therefore wearing it prematurely as well as creating an annoying noise while cycling) in the case of too-thick rotors, or overheating in the case of too-thin. Stick with rotors that are made by your brake system manufacturer or specifically designed to be compatible.

Rotors - diameter

An essential consideration is rotor diameter. Broadly speaking, the bigger the rotor you are using, the more braking power available.
The bigger the disc, the more braking surface is available per revolution of the wheel and the more leverage your brakes are able to exert on it. The most common rotor sizes are 160, 180 and 203mm. When choosing, you must take into consideration the type of bike you are riding and the type of riding that you do. Most XC and trail riders will find 160mm rotors offer more than enough stopping power for their needs; gravity-oriented AM or Enduro riders will find benefit in stepping up to 180mm, and downhill racers will requires discs of at least 200mm as a matter of course, not only for the increased power that they offer but also because bigger discs take longer to overheat, and cool down faster.

You may find that mixing and matching rotor sizes suits you best – many riders appreciate the power advantage of a bigger disc up front (where it matters), and run 180mm front/160mm rear, or 203mm front/180mm rear. Generally what works for you in terms of disc size will depend on what kind of riding you’re into – if you enjoy the downs more than the ups you’re unlikely to be too perturbed by the slight weight addition of bigger discs, but xc and marathon riders won’t see much point in adding more weight for braking power that they probably won’t need.
Fitting basics

Many modern disc brake sets come pre-bled, so all you need to do is bolt them on and bed them in.
However if your hoses need to be cut down to fit your frame, or if you buy a set that needs to be assembled, they will also have to be bled – meaning any air bubbles trapped in the system will need to be let out, or the brake system will feel ‘spongy’ in use. The procedure for assembling and/or bleeding brakes will vary according to every manufacturer and brake system, so pay close attention to the instructions supplied with your new brakes, and take your time. Bleeding isn’t difficult, but it does take patience and care.

USEFUL TERMS

Single-piston: Single-piston brake calipers feature one stationary piston to one side of the rotor, and just one moving piston, which as it moves inwards bends the rotor slightly so that it is caught between the pad surfaces.

Bite point: The point in the arc of pulling the lever at which the pads make contact with the rotor and the brakes engage. Bite point is adjustable in many higher-end brake models, allowing riders with smaller or larger hands to dial in their own personal preferences.

Modulation: Modulation is accurately controlling the amount of brake power you use. Well-modulated brakes give you a large degree of control over the power level before the brakes fully bite, locking the wheel.

Bedding in: All new brakes must be ‘bedded in’ in order to work as they are supposed to. After fitting new anchors or when trying out a new bike, ride up and down the street or a flat section of trail, pedalling up to a decent speed and hauling hard on the brakes until the bike stops. Repeat 10-15 times to enable the new pads and rotor properly mate for improved stopping power.

Pads: Organic vs. Sintered: Brake pads come in two types: Organic (or ‘resin’) and sintered. Organic pads, made from a high-density ceramic, have a softer compound than metallic sintered pads. Organic pads generally provide better stopping power and heat dissipation, but can wear out more quickly in wet and gritty conditions – your preference may depend on your riding location, or the season.


MOUNTAIN BIKE V-BRAKES

Hydraulic disc brakes are now used on the majority of mountain bikes but some riders still prefer the light weight and user-friendliness of non-disc or rim brakes (so-called because they use the rim of the wheel as a braking surface), which are also common on budget bikes.
There are two main types or rim brake – caliper brakes (as used on most road-racing style bikes including time-trial and triathlon bikes as well as tourers) – and cantilever brakes.

Image

The vast majority of MTBs and/or city bikes/hybrids that use cantilever brakes use a specific type called v-brakes. These consist of individual brake arms mounted via two brake bosses, with each arm of the brake attached to a boss on each seatstay or fork leg.
With v-brakes (also called ‘direct-pull’ brakes as opposed to the ‘centre-pull’ cantilevers found on Cyclo-X bikes, see above) the cable is aligned to the side of one of the brake arms, rather than down the middle. The outer cable connects to a hollow metal housing or 'noodle', which itself sits into a fitting on the top of one of the brake arms. The inner cable meanwhile runs on through the 'noodle' and is clamped to the top of the opposite brake arm. When the cable is pulled, one arm is pushed inwards and the other pulled, bringing the brake pads into contact with the rim.

In truth there’s not much to choose from between different makes or levels of v-brakes - at all price points they share the same basic principles and design, with more expensive models making use of lighter, stronger materials and offering better pads for improved braking performance.
The question to be considered is ‘why v-brakes?’ rather than ‘which v-brake?’, as discs have generally been proven to be better performers in all conditions.
V-brakes do have some advantages – they are generally lighter than disc brakes and are mechanically simpler, therefore their repair, adjustment and maintenance can be less daunting.
Many riders also appreciate the sharp, direct feel of a quality set of v-brakes, while others may simpler have an older bike without the mounts required to run discs.
Their major disadvantage is that by using the rim as a braking surface they are more prone to deteriorating in performance and lifespan when riding in wet and muddy conditions. Disc brakes have been developed to overcome these drawbacks, but for urban riders and those who are lucky enough to enjoy dry trails for the majority of the time, rim brakes provide ample stopping power.

Remember that to fit v-brakes you will need to ensure that your frame, forks and wheels are compatible (for example when building a bike from the frame up).
When fitting v-brakes or other cantilevers both frame and forks will need to have bosses to which the brakes themselves attach. These are threaded metal stubs on the fork legs and on the seatstays of the frame – adaptors are available in case your frame or forks doesn't have them.
Meanwhile your wheel rim will need to have a braking surface – disc-only wheels are not suitable.



ROAD BRAKES

The vast majority of road bikes –including road racing bikes, TT and tri bikes and tourers - use a type of rim brake called caliper brakes.

Image

These use brake arms that reach downwards from above the tyre, with the entire brake unit attached to the frame or forks via a central pivot bolt positioned above the wheel. Pulling on the cable pivots both the arms inwards, bringing the brake pad into contact with the rim. When adjusted correctly, both pads will hit the rim at the same time.
Caliper brakes have the advantage of being compact, light and easily adjustable. However their braking power is eclipsed by that of hydraulic disc brakes, which also have the added advantage of using separate braking surface positioned away from the wet and grit of the road.
While caliper brakes are ubiquitous on most road bikes, more and more road models are starting to use hydraulic discs, with manufacturers racing to refine MTB disc designs to suit road bikes and road brake/gear lever combos.

As with v-brakes, caliper brakes for road bikes are functionally very similar across brands and price points – paying more will get you a lighter brake with sharper performance, but even the most budget calipers will work the same way as the most expensive.
Caliper brakes for road bikes fall can either be single-pivot, where both arms pivot at a single point (the centre bolt), or dual-pivot, where one arm pivots at the centre and the other at the side (the second pivot attached to the other arm).

Image

Single-pivot brakes are generally lighter but dual-pulls offer more braking power. Most modern road bike calipers are side-pull (the cable actuating the brake is to one side instead of in the centre).
Caliper brakes for road bikes are usually attached with a bolt which threads through a corresponding hole on the frame – road bikes may have a short brace that connects the seatstays close to the seat tube, with the hold drilled through this, while on road forks the hold will be found just below the steerer tube.
NOTE: Most caliper brakes are used in conjunction with the combined brake and gear lever units found on modern road bikes. Separate brake levers are available but cantilever brake levers (e.g. v-brake levers) are not compatible with calipers as they require a different amount of cable to be pulled in order to work properly.
If you are considering a disc brake upgrade for your road bike, be sure to check compatibility. As with MTBs, disc brakes for road bikes will require mounts on the frame and forks for the brake calipers, and bolt holes on the wheel hubs for the disc rotor. As disc brakes are only making inroads into the road market now, fewer road bikes will be ‘disc-ready’ as standard and it may be an expensive upgrade (also, for hydraulic discs you will need new brake/gear levers, or a cable-actuated widget called a disc brake converter which allows you to run hydraulic hoses to conventional road levers). Either way, it’s likely to work out an expensive upgrade.

Brake pads – cartridge v non-cartridge
If you’re not happy with the performance of your road bike caliper brakes, you might want to take a look at the type of brake pads you are running. Stock pads are often hard and cheap, with better-quality aftermarket options capable of vastly improving your braking power.
When upgrading pads look for a rubber compound that suits the conditions you ride in (wet, dry or all-round compounds are available). Also, two-piece ‘cartridge’-type pads –which consist of a rubber block that slides into a metal cartridge – generally outperform the ‘all-in-one’ type pads that may be fitted as standard on llow- to mid-end bikes.
A brake pad upgrade could be a cheap and effective way of getting the best out of your stoppers.

Long-drop brakes

Image
An important factor to consider when choosing caliper brakes for a winter trainer or touring bike is the amount of ‘drop’ they have – i.e. the length of the brake arms. Because bikes designed for touring, winter training and commuting (or ‘four-season’ road bikes) offer enough clearance to accommodate larger tyres (28mm and up) you are going to need to ensure that the brake arms are long enough to get around the tyres and reach the rim, and can also be used with mudguards. Look for ‘long-drop’ or ‘deep drop’ brakes rather than ‘standard drop’ and you should be good to go.
User avatar JackRabbitSlims
Member
 
Posts: 1,474
Joined: 10 Jan 2010 01:06
Location: On The Road.

05 Sep 2015 16:49

Fantastic writeup, you should have a blog for this stuff and get some ad revenue rather than giving it to (our good friends, but come on!) cyclingnews.com. :)
User avatar red_flanders
Veteran
 
Posts: 5,705
Joined: 03 Apr 2009 06:45

09 Sep 2015 19:18

you're very welcome

more to come on other areas & topics

when i find the time
User avatar JackRabbitSlims
Member
 
Posts: 1,474
Joined: 10 Jan 2010 01:06
Location: On The Road.

17 Sep 2015 01:48

I have a burning question for you, JRS, regarding some "vintage" caliper brakes - not sure if they need replacing, or if I'm just adjusting them wrong. (Either way they're driving me nuts, I'm used to messing around with just your basic v-brakes.)

I'll take a picture of them once I have a camera handy, I think pictures would be helpful.
User avatar Tricycle Rider
Member
 
Posts: 1,748
Joined: 09 Feb 2013 11:12

Re:

17 Sep 2015 03:14

red_flanders wrote:Fantastic writeup, you should have a blog for this stuff and get some ad revenue rather than giving it to (our good friends, but come on!) cyclingnews.com. :)
Not sure about JSR, but I consult what I consider "the bible of Sheldon Brown" when I need help (plus lots of youtube videos), but this can be very impersonal and it can be hard to ask specific questions. So...

If we can somehow help each other out here (without having to part with our money) I think that would be cool.
User avatar Tricycle Rider
Member
 
Posts: 1,748
Joined: 09 Feb 2013 11:12

Re:

17 Sep 2015 06:31

Tricycle Rider wrote:I have a burning question for you, JRS, regarding some "vintage" caliper brakes - not sure if they need replacing, or if I'm just adjusting them wrong. (Either way they're driving me nuts, I'm used to messing around with just your basic v-brakes.)

I'll take a picture of them once I have a camera handy, I think pictures would be helpful.


vintage stuff is not really my forte, but post up some pics and I'm sure there will be some assistance offered
User avatar JackRabbitSlims
Member
 
Posts: 1,474
Joined: 10 Jan 2010 01:06
Location: On The Road.


Return to Workshop & Maintenance

Who is online

Users browsing this forum: No registered users and 2 guests

Back to top