This post compares the advantages and disadvantages of 140mm and 160mm disc brake rotors.
The Advantages of 160mm Rotors
- Superior Braking Power
160mm rotors are 14% larger than 140mm models. Consequently, the brake caliper is positioned further away from the center of the rotor and the hub.
The extra distance increases the leverage that the caliper has on the rotor and the hub/wheel. (In simpler words, the larger rotor acts as a longer lever.)
The additional mechanical advantage that the larger rotor offers decreases the effort that the rider has to exert through the brake lever to slow down or stop the bike.
When all other variables are equal (brake model, pads, levers…etc.), the same squeeze of the lever produces more stopping power when the rotor is bigger.
Note: The additional braking power makes 160mm rotors better for heavy riders and touring cyclists traveling with a lot of gear.
- More Effective Heat Dissipation
The friction between the brake pads and the disc brake rotors increases the temperature of each. As one might expect, the effect is much more pronounced during long descents when the rider has to apply the brakes over a long period of time.
160mm rotors have a larger thermal mass and thus offer better heat dissipation than 140mm models.
In extreme cases, overheating of the brakes could create the following issues:
a. Reduced Braking Power + Brake Pad Damage
During long descents, the heat could melt the upper layer of the brake pads and transfer parts of it to the rotor. This results in notable braking loss because the pad is no longer contacting with bare metal.
b. Disc Warping
Disc warping is a process during which the surface of the rotor becomes uneven.
The source of the issue are bad brake pads and/or a bent rotor. Brake pad overheating can facilitate disc warping because the heat damages the pads at random locations.
The Downsides of 160mm Rotors
- Easier To Bend
The extra size of 160mm rotors makes them more susceptible to external damage (e.g., banging the rotor against an object while storing the bike.) A bent rotor results in brake rubbing, loss of braking power, and premature wear of the pads and the upper layer of the rotor itself.
- More Aggressive Brake Modulation
Larger rotors come with extra leverage, and the calipers grab them earlier. The result is reduced brake modulation (control over the braking force).
If the brakes have too much modulation, they will bottom out (arrive at the end of their travel) before reaching full braking power.
If there’s too little modulation, braking is stiff, there’s little feedback, and the brakes work in on/off mode with small or no phases in between.
The extra material needed for 160mm rotors makes them slightly heavier:
|Shimano RT-CL900||96g||NOW8 Ultralight disc||67g|
|Shimano RT-CL800||96g||Jagwire Sport SR1||129g|
|Trickstuff Dächle UltraLeicht||72g||Trickstuff Dächle HeavyDuty||111g|
|Jagwire Sport SR1||112g||Rotor UNO||95g|
|Carbon-Ti X-Rotor||65g||NOW8 Float||108g|
|Dura Ace Saint XTR RT-MT900-SS||90g||Magura MDR-C||140g|
|G2 Clean Sweep||91g||SRAM Centerline Round Edges||112g|
|SLX SM-RT70-SS||121g||FSA Afterburner||125g|
|XTR SM-RT98-SS Center Lock Internal||101g||Carbon-Ti X-Rotor SteelCarbon 2||77g|
|NOW8||79g||Shimano RT86 Ice-Tech||113g|
|Average:||92.3g/3.26oz||Average:||107.7g / 3.79oz|
Conclusion: The average weight difference between 140mm and 160mm rotors is small enough to completely ignore it unless one is trying to build the lightest possible bicycle. In that case, it’s logical to choose 140mm rotors.
The Advantages of 140mm Rotors
140mm rotors have the following advantages:
Since 140mm rotors require less material, they tend to be slightly cheaper. Of course, the final price depends on the particular model.
- Less Likely To Bend
The smaller profile of 140mm rotors makes them less susceptible to external damage.
- Lower Chances Of Brake-Rub
140mm rotors have a smaller radius. As a result, it takes a larger bend to experience brake rubbing.
As already mentioned, 140mm rotors are a bit lighter than 160mm ones.
- Better Modulation
Since 140mm rotors aren’t as grabby they offer better modulation. Hence why some riders put them at the back. After all, the rear brake is used primarily for slowing down rather than stopping. (The front brake provides a lot more stopping power thanks to the extra traction of the front wheel.)
The Disadvantages of 140mm Rotors
- Less Braking Power
The only notable disadvantage of 140mm rotors in comparison to 160mm rotors is the smaller braking power. This could be problematic if the bike is loaded and/or used for long and extreme descents.
How to Switch From 140mm to 160mm Rotors (Short Guideline)
Step 1: Determine the Type of Disc Mounts That You Have
There are three types of disc brake mounts – International Standard, Post Mount and Flat Mount
International Standard (IS) is found on older forks and frames. The brake caliper attaches via bolts screwing perpendicularly to the mount. Modern fork manufacturers have completely abandoned the International Standard.
If you have IS mounts and want to switch from 140mm to 160mm rotors, you will need a +20 IS to Post Mount adapter.
Post Mount (PM) is found on modern bikes. The caliper attaches via bolts going straight into the mount.
If you have PMs designed to run 140mm rotors by default and want to upgrade to 160mm, you will need a 20mm post mount adapter.
Flat Mount (FM)
The flat mount is a fairly new disc mount standard found on road bikes. The caliper attaches to a flat part of the fork or frame. The goal is weight saving and simplicity.
If you have FMs designed to run 140mm rotors by default and want to upgrade to 160mm, you will need a 20mm FM adapter.
Step 2. Install the Calipers
Once you have the right adapter on, install the brake calipers.
Step 3: Replace the Old Rotors
Remove the wheel, unscrew the rotors, and screw on the new ones. Get the bolts to the torque required by the brake manufacturer.
Step 4: Install the Wheels
Summary: What You Need To Know
1. 160mm rotors offer more stopping power than 140mm models. This makes 160mm rotors better for heavier riders and extreme descents.
2. 140mm rotors are lighter, provide better modulation and work sufficiently well for small riders and bikes that won’t be used for downhill riding.
3. You can switch from 140mm to 160mm by installing a 20mm mount adapter.
4. Many people run a 160mm rotor at the front for extra braking power and a 140mm one at the back for greater modulation.