Saturday, November 30, 2013

Road or MTB Components for Dahon / Tern Folding Bikes? - Part 2

Continuing from the first part of this article, Road or MTB Components for Dahon / Tern Folding Bikes? - Part 1, let us now continue with the brake components. In this second part, we will look at the different types of brake calipers and brake levers, and learn which brake levers are compatible with which brake calipers. With this understanding of the different brake systems, you can better determine what brakes to use on your folding bike.

Before you read on, I strongly recommend that you check out Part 1 of this guide, and also the other Guide To Upgrading your Dahon / Tern folding bike. This will give you the necessary background and info for basic folding bike upgrading.

2) Brake Calipers + Brake Levers

On modern bicycles, there are 3 main types of brakes: Linear pull brakes (commonly known as V brakes), caliper brakes and disc brakes. Some other less common types are cantilever brakes (still found mostly on cyclocross bikes only), roller brakes, coaster brakes or drum brakes. For more info on each of these brakes you can refer to this link here.

Wikipedia: Bicycle Brakes

V brakes and disc brakes are normally classified under MTB components, while caliper brakes are normally seen only on road bikes. Sometimes, when we upgrade a folding bike, we will be faced with a choice of using V brakes or caliper brakes. This will be dependent on the type of brake lever that you have. Before we look at the compatibility, it will be good to have some background info about these different brake systems. If you are only interested in what works with what, then skip right past this section to the part below labeled "Compatibility Between Brake Levers and Brake Calipers".

Background Info for Brake Systems:
Each brake system is made up of two main parts: The brake lever that is installed on the handlebar, and the brake caliper that is installed around the wheel.

Each type of brake lever and brake caliper has two important attributes that determines compatibility between brake levers and brake calipers: Mechanical advantage (or leverage ratio) and cable pull.

Mechanical advantage refers to the leverage provided by the brake lever or brake caliper. This is derived based on the distance of the activation point to pivot, compared to the distance from the brake pad to the pivot. Using brake levers and calipers of incompatible mechanical advantage will lead to an abnormal braking feeling in the brake lever, and also undesirable braking performance.

Cable pull refers to the amount of brake cable that the brake lever or brake caliper needs in order to function properly. It is important to match the cable pull of brake lever and brake caliper, for the brake system to function effectively.

Mechanical advantage and cable pull are directly related: For example, a V brake caliper has a high mechanical advantage, and requires a long cable pull. On the other hand, a road caliper brake has a lower mechanical advantage and thus requires a shorter cable pull to function.

Confused? Don't worry, each brake system's mechanical advantage and cable pull will be listed below, and there will be a summary to show you the compatibility between different brake components.

For the 3 most common types of brake systems, there are advantages and disadvantages to each of it. Let us take a brief look at them before we move on.


Brake Calipers:
V Brakes:
 
 Avid Single Digit 7 V brakes on my Boardwalk. One of the first few upgrades.

V brakes are found on more than 95% of Dahon and Tern folding bikes. From an entry level Dahon Eco 2 (SGD 300+) to high end Tern Verge X20 (SGD 4000+) folding bikes, they come with V brakes of different levels. Why are V brakes so common on folding bikes?

Advantages of V brakes:
1) Cheap
2) Easy to set up
3) Spare parts such as brake pads are cheaply and easily available anywhere
4) Simple mechanism makes it very reliable
5) Sufficient stopping power for almost all usage (except for perhaps loaded touring or downhill bikes)
6) Relatively wide pad clearance to accomodate out-of-true rims
7) Comparatively lightweight
8) Large clearance for fenders

Disadvantages of V brakes:
1) Less stopping power than disc brakes
2) Poor braking performance in the wet
3) Brake pads disintegrates very fast in the wet
4) Maintenance and cleaning is necessary after riding in the rain or wet roads, as the brake pads will leave a lot of residue on the rims
5) Wears out wheel rims (usually not a problem as it takes a long time and high mileage)

Mechanical Advantage of V brake calipers: High
Cable Pull of V brake calipers: Long


Caliper Brakes:
 

Very few Dahon or Tern folding bikes come stock with road caliper brakes, with the rare exceptions being the Dahon Speed Pro TT or the Tern Verge X30h. The reason why these bikes come with caliper brakes is NOT because caliper brakes work better, but because they are needed to pair with the road shifter/brake lever combo, or Dual Control Levers (DCL) in other words.

These two bikes are equipped with bullhorn bars and Road DCL, which means that they need caliper brakes for proper brake compatibility. So what are the pros and cons of a road caliper brake?

Advantages of road caliper brakes:
1) Lower frontal profile for less aerodynamic drag (not sure if it is true?)
2) Brake pads are easily available
3) Reliable

Disadvantages of road caliper brakes:
1) More expensive than V brakes
2) Less pad clearance to accomodate out-of-true rims
3) Less clearance for wider tires and fenders
4) Small clearance between tires and brake arch causes mud buildup in wet conditions
5) Less stopping power than disc brakes
6) Poor braking performance in the wet
7) Brake pads disintegrates very fast in the wet
8) Maintenance and cleaning is necessary after riding in the rain or wet roads, as the brake pads will leave a lot of residue on the rims
9) Wears out wheel rims (usually not a problem as it takes a long time and high mileage)

Mechanical Advantage of road caliper brakes: Low
Cable Pull of road caliper brakes: Short


Disc Brakes (Mechanical and Hydraulic): 
 
Hayes Mechanical Disc Brake Caliper


Very few disc brake systems are found on Dahon or Tern folding bikes. Some bike models which come with disc brakes are the Dahon Formula S18 and the Dahon Dash P18, which both have a mechanical disc brake system.

Other brands of folding bikes such as JAVA and Bike Friday do have a few more models with disc brakes. However, disc brakes are still not common on folding bikes, as the rotors can be prone to damage or bending when the bikes are folded and transported around.

The advantages and disadvantages of disc brakes listed below are with respect to folding bikes, which may not necessarily apply to full sized bikes such as mountain bikes.

Advantages of disc brakes on folding bikes:
1) Excellent stopping power for all terrain and riding conditions
2) Works well in all weather
3) Little to no maintenance required after riding in the rain
4) Does not affect tire choice or impede fender installation
5) Less affected by muddy conditions as compared to V brakes or caliper brakes
6) Does not wear out wheel rims
7) Not affected by out-of-true rims as the braking surface is on the rotor and not the rims

Disadvantages of disc brakes on folding bikes:
1) Slightly heavier than V brakes or caliper brakes
2) More expensive
3) Difficult to bleed hydraulic systems as compared to fixing mechanical brake systems
4) Spare parts are less readily available and more tricky to install
5) More prone to brake rubbing due to small clearance between rotor and brake pad
6) May not be suitable for folding bikes due to possible tight bends on the hydraulic hose when folded
7) Rotor is prone to damage when the bike is folded and laid on its side
8) More difficult to DIY as compared to V brakes and caliper brakes
9) May interfere with some rear racks, if the rear brake caliper is mounted on the seatstay

Hydraulic disc brake systems are more powerful than mechanical disc brake systems, but the tradeoff is heavier weight and higher price.

For hydraulic disc brake calipers, they can obviously only be used with hydraulic brake levers. These usually come as a set (including the hose and already pre-bled) and so there is no compatibility issues. The only problem is the hydraulic hose length. If the hose length is too long or short, they will need to be cut or changed, which involves bleeding the hydraulic fluid in the brakes.

As for mechanical disc brakes, there are models that are compatible with V brake levers, and models that are compatible with road brake levers (such as drop bar DCL). As such, they have different mechanical advantage and cable pull.

For use with V brake levers:
Mechanical Advantage: High
Cable Pull: Long

For use with road brake levers:
Mechanical Advantage: Low
Cable Pull: Short

That was a lot of info regarding brake calipers! Now, we need to look at the different types of brake levers out there, and from there we can determine the compatibility with brake calipers.


Brake Levers:
There are 2 main types of brake levers, flat handlebar (FHB) brake levers and drop bar brake levers. FHB brake levers are for bikes with flat handlebars, such as most folding bikes and practically all MTB. Drop bar brake levers can be dedicated brake levers, or available as a DCL with the shifters. Examples are shown below.

Avid Speed Dial 7 brake levers for FHB. Customised with gold coloured cable adjust bolts.

Shimano drop bar shifter/brake lever DCL on the left, drop bar brake lever on the right


Flat handlebar brake levers:

Flat handlebar brake levers are available as V brake specific only, road caliper brake specific only, or both V brake and road caliper brake compatible. If your brake lever is from a MTB or Trekking groupset, such as Deore or SLX/LX, then the brake lever is likely to be V brake only. There will only be one hole or hook for the brake cable.

Avid FR-5 V brake levers, for use with V brake calipers only. From MontagueBikes.com

 Shimano BL-R550, for use with road caliper brakes only. Note the short distance between the pivot and the brake cable hooking area (not shown). This is what gives it a short cable pull but high mechanical advantage.

There are also brake levers that are compatible with both V brakes and road caliper brakes. These brake levers feature a selectable position for the brake cable hook, which allows it to have the correct leverage ratio and cable pull for the different brake calipers.

Shimano BL-R780, with a slot on the lever itself. This makes it compatible with V brakes or caliper brakes. Picture from Ebay.

A clear illustration showing how to set the brake lever to be compatible with either V brakes or caliper brakes.

V brake levers are actually also compatible with most MTB spec mechanical disc brakes. However, they are not compatible with road-specific mechanical disc brake calipers, such as Avid BB7 or Shimano BR-R505.


Drop Bar Brake Levers:

Most drop bars use a drop bar brake lever such as the Shimano BL-R600, or the shifter/brake lever combo type of Dual Control Lever. These brake levers are only supposed to be used with caliper brakes and not V brakes.

Shimano BL-R600 for drop bars or bullhorn bars. Only a brake lever and not a shifter.

SRAM Apex shifter/brake levers. It is both a shifter and also a brake lever. Used on drop bars or bullhorn bars.


Mechanical Advantage (Leverage Ratio) and Cable Pull of Various Brake Levers:

Each type of brake lever also has a different mechanical advantage ratio and cable pull. This determines which type of brake caliper it is compatible with!

V brake specific brake lever:
Mechanical Advantage: Low
Cable Pull: Long
Examples: Avid FR-5, Deore BL-T610

Road caliper specific brake lever (Mostly drop bar brake levers):
Mechanical Advantage: High
Cable Pull: Short
Examples: Shimano BL-R550, Shimano Ultegra 6800, SRAM Force 22

Brake Lever with selectable cable pull:
Mechanical Advantage: Low (for V brake) / High (for caliper brake)
Cable Pull: High (for V brake) / Low (for caliper brake)
Examples: Avid Speed Dial 7, Shimano Tiagra BL-4600, Sora BL-3500


Compatibility Between Brake Levers and Brake Calipers

After all the background info, we will now go back to answering the question: Road or MTB components for Dahon / Tern folding bikes? To be more specific, V brakes or caliper brakes for Dahon / Tern folding bikes?

To ensure compatibility, the key here is to ensure that the cable pull of the brake lever and brake caliper matches. For example, if you are using a drop bar brake lever (such as Shimano 105 5700 road shifters) with a short cable pull, you will need to pair it with a brake caliper with a short cable pull (such as a road caliper brake).

The best way to understand and check the compatibility is to use a table such as the one I created below.

Compatibility table for brake levers and brake calipers

Another way to look at it is that a brake lever with low mechanical advantage must be paired with a brake caliper of high mechanical advantage. An example would be to pair a V brake lever (low mechanical advantage) with a V brake caliper (high mechanical advantage). The resulting mechanical advantage would be not be too high or too low for proper braking function.

So what happens when you pair incompatible brake levers and calipers together?

Scenario 1:
Your existing folding bike uses a V brake lever and V brake calipers, such as a Dahon MuP8. You upgrade the bike to use a drop bar with road shifter/brake levers, but you did not change to caliper brakes and instead continue to use V brakes.

Drop bar brake lever: High mechanical advantage, short cable pull
V brake calipers: High mechanical advantage, long cable pull

What happens in this case is that you get very high overall mechanical advantage, which means that the braking force is very high. However, this is much higher than designed, and you will get a very spongy feeling at the brake levers due to the excessive leverage. What you are feeling is the flexing of the brake calipers or stretching of the brake cables due to excessive leverage.

Also, the cable pull ratio does not match. The V brake calipers require a long cable pull to activate fully, but your brake lever can only supply a short cable pull. You will need to set your brake pads very close to the rims in order to ensure that the brake pads can touch the rims when the brake lever is pulled. Even then, the brake lever will go very close to the handlebar when activated, which can be dangerous if the brake lever "bottoms out" on the handlebar, which prevents you from pulling any harder on the brake lever if required.

End result: Spongy brake feeling, chance of brake lever hitting handlebar, high chance of brake pad rubbing the rim due to small clearance.

You could use something such as a Travel Agent on the V brake caliper to alter the cable pull ratio, but the end result is usually not satisfactory. For more info check out the links below.

Travel Agent on Dahon Boardwalk
Caliper Brakes on Dahon Boardwalk
Travel Agent on Dahon Vitesse
Caliper Brakes on Dahon Vitesse

Scenario 2:
Your existing bike is a Tern Verge X30h with bullhorn bars, using road shifter/brake levers and road caliper brakes. You decide to ditch the bullhorn bars and convert the bike to using a flat handlebar. Due to that change, you change to a standard V brake lever, but you continue to use caliper brakes as there is no mounting point available for V brake calipers.

Brake lever for V brakes: Low mechanical advantage, long cable pull
Road caliper brakes: Low mechanical advantage, short cable pull

What you have here is the exact opposite of Scenario 1. The overall mechanical advantage is very low, as both the brake lever and brake caliper has low mechanical advantage. The cable pull ratio also does not match; the caliper brake only requires a short cable pull, but your V brake lever is generating a long cable pull.

The effect of this set up is that you will only need to pull your brake levers a very short distance before the brake pads touch the rim. The braking feeling will be very firm, which may seem good, but the actual fact is that this is caused by the low mechanical advantage of this brake setup. You will be unable to apply sufficient braking force, due to the low mechanical advantage of this system. Even if you pull hard on the brake lever and the feeling is firm, the actual braking force acting on the rims will be quite low.

End result: Firm braking feeling but poor braking power. The fingers will need to pull extra-hard on the brake levers to generate sufficient braking force.

This scenario is much less common than Scenario 1, but there is such a possibility if someone changes from a drop bar to a flat handlebar.

This incompatibility issue can be easily solved by using the correct FHB brake lever. Just get those types are are specific to road (such as Shimano BL-R550), or those with selectable cable pulls (such as BL-3500, 4600, R780). You can use either V brake calipers or road caliper brakes, and setup the brake lever to match accordingly.

Shimano Tiagra BL-4600, with selectable cable pull ratios. This makes it compatible with all cable actuated brake systems.

After reading through this long article, you should now understand the advantages and disadvantages of each brake system. Also, the compatibility between different brake levers and brake calipers can be found easily using the compatibility table above.

Almost all Dahon / Tern folding bikes come stock with V brake calipers, and it is possible for some to use road caliper brakes. Before you change your brake levers to road DCL, it is best to check if your bike frame can accept caliper brakes.

My recommendation is to always use caliper brakes with road shifter/brake levers, and not resort to other methods such as Travel Agents or short arm V brakes, as these do not work well enough in my opinion.

In the next part of this series, we will look at the other components, such as the crankset and cassette, and see if it is better to use road or MTB variants of these components on Dahon / Tern folding bikes.

3rd Part of this series!

14 comments:

  1. Hi-
    I'm having trouble mounting avid single digit 7 on my tern d8. The boss does not allow the brake arm to mount flush to the boss flange leaving a small space between. Have you heard of this, and do you have any suggestions on how to solve it.
    Thanks!

    ReplyDelete
    Replies
    1. I'm sure the bike came with V brakes already mounted. It does not matter if the brake arm is not fully flush against the boss, as long as the brake arm is secure.

      Delete
  2. I'm looking to upgrade the V-brakes that came on my Dahon D7 bike. It is a 2011 model bike. One of the v-brakes you recommended is the Shimano Brake T780. They are pretty expensive compared to the Shimano Acera Mountain Bicycle V-Brake. Are the Acera brakes better than the v-brakes that came on my bike? Thanks

    ReplyDelete
    Replies
    1. I would suggest getting the Deore BR-T610. They are inexpensive and perform well. Definitely better than the stock brakes. For best performance, upgrade the brake levers to Deore too.

      Delete
    2. Hi Steve,

      I've read a lot of good reviews on the Avid SD-7 V-brakes. I see you also had them installed at one point.

      Given the fact that both are in the same ball-park price range, can you please compare the 2 and give your opinion to which is preferable to replace the stock Kinetics (seem very similar to SD-5s) on my Tern P9.

      Cheers,

      Delete
    3. If you already have the Kinetix v brakes, the Sd7 or sd5 are very similar. The Sd7 uses more stainless steel which makes it more resistant to rust.

      To have a more obvious difference, you will need to upgrade the brake calipers and brake levers. The Deore brake caliper and brake levers will be better, the XT brakes will be even better.

      Delete
  3. which avid bb7 is suitable for folding bike? road or MTB version?

    how important is the brake lever?

    ReplyDelete
    Replies
    1. Are you talking about the brake caliper BB7?

      The brake lever is of course important.

      Delete
    2. the caliper.

      is it advisable or useful to change from 160 to 180 rotor for foldie?
      how to know whether the bike can handle the braking power of 180mm rotor?

      Delete
    3. No need for 180mm rotor, it is overkill for a folding bike ridden on road. Only downhill bikes or off road bikes will need 180mm or larger rotors.

      Delete
  4. Hi Steve
    I would like to change the Groupset sram to Shimano for my Tern X20(Model 2015)
    Could you please advise or recommendation

    ReplyDelete
    Replies
    1. Suggest getting the components that I have on my flat bar Dahon Muex.
      http://handsonbike.blogspot.sg/2014/04/how-to-build-affordable-high.html
      You can choose higher grade 10 speed road components for rd, fd and crankset if you like. Ultegra 6700 or Dura-Ace 7900.

      Delete
  5. Hi Steve
    Thanks
    Fyi I was given as gift of Aerospoke carbon wheel 20inch
    I am not sure if u want to change the existing Kinetic XPro to that Aerospoke
    As I believe Aerospoke will be gain some weights on it
    What your recommendation and comment should I?
    Looking forward

    ReplyDelete
    Replies
    1. The Kinetix Pro wheels are very good, and there is no reason to change it unless you prefer the looks of the Aerospoke wheels. Most probably it will be heavier too.

      Delete