Can you fit bigger rotors on a disc brake road bike?

Disc brakes have become pretty much ubiquitous on modern road bikes, and many riders will have a few questions when they eventually wear out through the rotor: How big am I, what should I actually use? , is there an advantage to going bigger? We’ve spoken to Shimano, SwissStop, Hope and SRAM to get you the answers.

What do you already have

If you’ve bought a road bike in the past few years with disc brakes, you probably have 140 or 160mm rotors. You can also have a jumpsuit with the smaller size on the back.

Take a look at your rotors, the size should be printed somewhere in the center of the rotor.

Can you get more power?

Simple physics dictates that yes, bigger rotors provide more stopping power. The basic principle is that when you increase the size of the rotor, you increase the leverage acting on the wheel, so it is easier to stop.

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Simple, right? Well, it’s not always that easy. Christian Heule of SwissStop said that “there are several limiting factors that can really affect how quickly a bicycle stops”.

The main obstacle to stopping power is grip. At some point, the force of the brake will overcome the friction between the tire and the road and you will lock up, causing a skid. Shimano’s Ben Hillsdon says, “If you use a rotor that is bigger than your riding style or the terrain demands it, you will have more aggressive stopping power and modulation will become more difficult.

This means that if you pull the brake levers with the same force of your hands, the larger rotor will lock the wheels sooner than with a smaller rotor. In practice, you can mitigate this just by being gentler with your hands. Danie Lategan of SRAM suggests that this reduction in manual effort is actually a benefit of the larger rotors.

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While you might not feel the difference in manual effort, it’s worth remembering the days when cantilever brakes were commonplace in the world of cyclocross. They lacked power even in the best conditions and the end of a wet run would leave your hands almost as tired as your legs. They were good at teaching you the right line choice, however.

Is bigger better?

But is bigger really better when it comes to rotor size? There’s no one answer for every rider, but every brand we spoke to agreed that if you’re a road rider using a 140mm rotor on the front of your bike, you will likely see benefits going up to a 160mm rotor.

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When disc brakes first appeared on road bikes, the 140mm size was seen as the size with the most rim brake-like feel, and the smaller size kept the weight as low as possible. As with a lot of things in cycling this has stuck, but there are plenty of bike brands and rotor manufacturers that choose to make their standard offer 160mm, at least on the front wheel.

Some brands of bikes, like Open, have also made native forks for 160mm rotors, meaning you don’t need an adapter that many road frames require use.

2020 Hope Technology Road CL Disc Rotor - detail 1.jpg

Component maker Hope, meanwhile, says it has always gone for 160mm by 140mm rotors. Robin Godden of Hope explains that “it doesn’t matter on-road or off-road, you always have the same moving mass to stop”.

On top of that, he says that “on the road you could go down at higher speeds for a longer time, so you would want consistent braking all the time. “

Christian Heule of SwissStop also pointed out the longer and faster road descents, claiming that the 160mm rotors have better heat management “due to the increased amount of material on the rotor surface and the longer time. until the brake pad touches the rotor again at the same point “.

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He continues, “With more efficient heat management, the rotor and pad can stay below their maximum operating temperatures and the entire brake system can perform as intended. “

Essentially, under the same braking conditions, SwissStop says that a 160mm rotor will continue to perform well for a longer period of time than a 140mm rotor.

Do bigger rotors weigh more?

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Yes, but there isn’t much in it. SRAM and Shimano both claim a weight gain of just 20g per rotor when going from a size of 140 to 160mm, and if your frame is designed to accommodate 160mm rotors natively, you can throw in the adapter used by many setups.

> Read our thoughts on SRAM Red eTap AXS brakes

Robin Godden of Hope says “the best braking is worth an extra 20 grams anyway.”

Is it easy to change the rotor?

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Increasing your rotor size from 140mm to 160mm is relatively easy, just check that your frame will fit larger rotors before spending the money. You will need to remove the rotor that is already attached to your wheel, but for center locking rotors this can be done with a cassette locking tool for rotors such as Shimano and SRAM road models, or a locking tool. 44 mm with 16 notches for systems like Campagnolo.

Torx with tool.jpg

The 6-bolt rotors are even easier to remove with a Torx 25 wrench all that is needed. Once you’ve put the new rotor in place you’ll need to adjust the position of the calipers, but it’s a simple job.

Are there any downsides to getting bigger?

Christian Heule of SwissStop suggests that one of those drawbacks is that they “tend to be less straight and bend more easily after use, which can cause the rotors to rub against the pads, causing drag”.

To guard against this, Christian says that SwissStop makes its rotors thicker as they increase in size. This, he says, “has the side effect of helping the rotor to cool.”

> Everything you need to know about disc brakes – read our definitive guide

You will also need to check that your frame and fork can accommodate larger rotors. This is best done by contacting the manufacturer.

As stated earlier, with the larger rotor providing more leverage on the wheel, you will need to learn how to control that power. This finer control of your hands may take a little getting used to, but you should be familiar with your newfound power within a few turns.

How to choose the rotor size

SwissStop 140mm catalytic rotor

SwissStop’s advice is: “On drop bar bikes, the general recommendation is to use 160 forward at all times to optimize braking performance. Almost all UCI teams use the 160mm and 140mm combination although they are generally lighter than us and a lot more experienced so we recommend at least this setup to start with for road bikes and maybe consider increasing the tail rotor for gravel applications. “

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Shimano says: “In general, bicycle manufacturers are required to ensure that their bikes meet EN / ISO standards, which also include braking performance. Therefore, bikes are equipped with rotor sizes which must be suitable for the type of bike and the use. If a rider has different riding needs or characteristics, factors such as weight reduction or more stopping power can determine whether they need a larger or smaller rotor.

SRAM 2 rotor size chart

SRAM, meanwhile, made a handy chart. This suggests that for most road trips, 140mm rotors are sufficient for riders weighing up to 73kg. If you’re heavier than that or do a lot of long, steep descents like on hilly or mountainous terrain, the graph suggests switching to a 160mm front / 140mm rear setup.

Interestingly, cyclocross riders weighing up to 82kg are recommended to use only 140mm rotors. This is an example of where a larger rotor could jam the wheels too easily due to lack of traction due to the combination of muddy surfaces and relatively narrow 33mm tires.

So, do the cons of gaining weight outweigh the positives? From what we can see, that’s a no, and aesthetics are generally the reason riders cite to stick with the 140mm rotors front and rear. If you can look past the visuals, there’s very little downside.

About Robert James

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