What’s wrong with Chris Froome’s disc brakes?

Chris Froome moved from the Ineos Grenadiers (formerly Team Sky) to Israel Start-Up Nation for the 2021 season, and he’s done more than change his jersey. Froome has also switched from Pinarello to Factor bikes, a move that will see him racing on disc brakes for the first time in his career.

But in a video where he tried his hand at reviewing his new Factor Ostro VAM, Froome wasn’t singing the praises of disc brakes. Despite saying that the performance in both wet and dry conditions impressed him, he didn’t feel the same way about all aspects of his new components. It's a very honest review of the bike which is certainly refreshing from a pro rider, most of whom usually repeat the lines that the marketing department has given them.

> 8 reasons not to get disc brakes — find out the hassles before you switch

We’ve re-watched Froome's review, paying particular attention to his comments about what he doesn’t like about those disc brakes, and we’ve noted the likely causes, the fixes, and how to avoid the issues in the first place. You can thank us later, Chris. Maybe in your Tour de France winner’s speech.

Froome makes a valid point regarding disc brakes being something that many racers wouldn’t have chosen had the manufacturers not pushed them. Froome says that they “are going to have to adapt and learn to use them, because if you're not on disc brakes already it's only a matter of time before you're made obsolete and forced onto them.”

Froome's points are also common issues that many riders that are new to disc brakes will encounter, so it is certainly useful to explore the tips and tricks that will make the disc-brake user experience better if you too have just switched over.

Before we dive in, we’re not about to bash either rim brakes or disc brakes. Each system has good and bad points and has been used in and out of the racing world just fine for years.

Right then, let’s get into the issues that Froome cited in his video, and see if we can help fix them.

A downside to disc brakes is the constant rubbing

Yep, just like a rim-brake, a disc system will rub if incorrectly set up. If the rubbing is constant and you can hear the noise through the whole rotation of the rotor, the calliper needs repositioning. Check the thru-axle is tight first.

> How to look after disc brakes — 7 ways to get the best performance

If you can hear a noise at only a certain point in the rotation, the rotor is likely bent/warped. Straighten it with a disc brake rotor truing tool.

Potential for mechanicals

What can go wrong with a hydraulic disc brake system out on the road? There are a few things like a loss of braking power caused by a leak in the system, the brake rubbing, or even just noise caused by contamination. 

Fixing these problems while out training or on a leisurely ride is a case of riding home with one working brake, attempting to straighten the rotor, or simply putting up with the noise.

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

If you’re a pro in a race, you can switch to your spare £11,000 bike at a quiet moment, but an issue with a rim brake setup would likely have you dropping back to the team car anyway.

We'd say that a snapped brake cable and a loss of pressure in a hydraulic disc brake system are equally rare. To avoid issues with either system, check your brakes regularly and keep on top of cleaning and maintenance.

Overheating

If you drag any brake system – ride with the brakes engaged – you’ll eventually overheat a certain part of that system. On a rim brake bike, you could end up exploding the tyre’s inner tube, melting the tubular glue if you’re on tubs, delaminating the carbon brake track, or something else equally disastrous.

Disc brakes, on the other hand, simply fade (they lose power) – but it takes a very steep hill, a lot of weight and a long time dragging the brakes to do this. The air temperature is also a factor.

On both rim brakes and disc brakes, the answer is simply to avoid dragging your brakes. Actuate them one at a time, allowing each to cool off a bit before you next use it.

The discs become warped

This is a really annoying one. Under really heavy, repeated, or consistent braking, disc rotors can warp, or in simpler terms, go a bit wonky. They need straightening with a proper disc brake rotor truing tool. It might be a good idea to add one to your saddlebag; they’re not heavy.

One piston firing more than the other

This is a dastardly problem that is tricky to spot unless you’ve got the pads out, exposing the pistons.

One piston that moves less than the other can be caused by brake dust that gets deposited on the piston’s rim. If this contamination gets trapped between the calliper and the piston, it can cause friction, stopping the piston from moving freely.

To avoid this, don’t press the pistons back into the calliper if they’re dirty.

> What's the best way to clean disc brakes on a bicycle?

If you have done this, the fix is to clean the brake dust off. You’ll need to expose the piston by actuating the brake lever without the pads in the calliper. Go careful, you don’t want to press the pistons out.

Next, clean the piston rim using cotton buds and something like acetone. Before you press the pistons back into the calliper using a proper piston press, apply a little brake fluid to the piston rim using a clean cotton bud.

You can take this chance to ‘exercise’ each piston individually by actuating the brake while holding the opposite piston back with a plastic tyre lever. Repeat this until both pistons move equally.

Will Froomey be a contender in 2021 if he gets his brakes sorted? Let us know what you think.