Jim’s Tech Talk
by Jim Langley
“Andy” is a cycling friend I’ve known for decades. When I was the head mechanic and service manager at a bike shop here in Santa Cruz, California he was a loyal customer. I ran into him at the grocery store the other day.
After catching up a bit, he told me he had recently retired. He said that now that he has more time to ride, he’s shopping for what he expects will be his last new road bike. He wants a really nice one.
He told me that while he has a good idea of what he’s looking for in the way of frame, wheels and drivetrain components, he needs my help with one critical detail. The final decider for him is whether or not his new road bike should have disc brakes? Andy has always ridden road bikes with side pull rim brakes – the standard type on most road rigs since the dawn of road riding.
I’m going to share with you what I told Andy, and then you can have your turn expressing your point of view in our comments.
I’m sure the discussion will be helpful to many more riders than Andy because this is the time of year when lots of roadies shop for new bikes. And, disc brakes have been coming on road bikes for a few years now, so there are plenty of bicycle brands and models to choose from.
What I told Andy
The first thing that I did was to congratulate my friend on his timing. Because there are signs that if he waits even only a few more years it’s possible the choices in new road bikes with rim brakes will be significantly reduced. Which would mean he couldn’t get them even if he wanted to unless he bought a certain brand or model – maybe not on his wish list – or a previous year bike.
I’m not going to get into why this is happening, because the reasons are complicated and I only partly understand the forces at work. But, personally, I find it frustrating when a major change like this is forced on us. And, specifically with rim brakes, there’s no good reason to stop making bikes with them.
Since he asked my opinion and I know that Andy rides like I do on the same roads, I told him I would recommend sticking with rim brakes. Keep reading for my reasoning.
Why rim brakes still have their place
Before I talk about disc brakes, I’ll explain what’s so great about rim brakes. In a nutshell it’s their simplicity. Because they attach to the bicycle frame and are operated by wire cables, they’re easy to setup with basic hand tools and they hold their adjustment for a long time.
Most rim brakes have built-in barrel adjusters allowing riders to tighten the brakes by hand when needed. Most also have quick release mechanisms to ease wheel removal. Brake QRs also come in handy for opening the brake to provide clearance should you break a spoke or hit a pothole knocking your wheel out of true.
Rim brakes might also feature wheel guides built in that help the wheel find “home” and center itself when it’s installed. And most have ways to easily center them over the wheel built in.
As long as the brake pads are replaced as needed on rim brakes – a quick and easy job on most – they can operate perfectly for years with no other attention. Also, rim brakes can be made to weigh next to nothing and still provide excellent stopping power.
Limitations of rim brakes
One of the biggest issues for many riders is reduced braking performance in the rain. Water is picked up by the wheels and can greatly decrease the brake pads’ grip on the rim until they clear the water and can “bite” into the rim again.
A related issue is rim wear from braking in inclement weather. Dirt and debris gets stuck in the brake pads essentially turning them into sandpaper and causing them to grind through the rim braking surfaces.
Another common problem is the brake rubbing the rim on one side. It’s usually easy to fix, but if you don’t know how to do it, it can be annoying.
Advantages of disc brakes
The biggest advantage of discs is that they keep working perfectly no matter how bad the riding conditions get. And, you will never ruin a rim again because nothing rubs on the rim, disc brake pads rub only on the rotor.
Also, because the rotor is a flat piece of metal (carbon rotors exist but are rare), the brake pads can’t compress it the way they can squeeze and compress rims. This is one of the reasons disc braking feels more powerful and consistent when riding or pumping the brakes on a long descent.
In the case of hydraulic disc brakes, the feel is even stronger and more exact. Because they use fluid inside a sealed system to operate the brakes, instead of the wires used for rim brakes and cable-activated discs. Wires/cables and the housings they run inside can let the cables develop slack under pressure changing the braking performance. Hydraulic disc brakes won’t change at all unless something’s wrong.
Another big plus for hydraulic disc brakes is that their hydraulic hoses aren’t affected by tight turns the way wire brake cables and housing are. So, with hydraulic discs it’s possible to completely hide the hoses in the frame, stem and bars. This is resulting in some the cleanest looking road bikes ever – if you can ignore the rotors.
And, because nothing is rubbing on them, the rims can be lighter on a disc road bike. For example, there’s no need to add braking tracks on carbon disc rims. And, since the rims are rotating weight, the grams shaved here can drastically improve a bike’s performance. Plus, the light rims might never wear out saving money over the long haul.
One more plus, while it’s kind of an extreme example, if you’re a roadie who regularly breaks spokes or dents rims, rim brakes can prove problematic. Because the rim damage and broken spokes can make the rim wobble enough that it constantly rubs on the brakes.
You can always open the brake quick release or even disconnect the brake cable to widen the pads. But, with disc brakes the wobbly, damaged rim(s) hardly matters at all because there’s no rim brakes to rub on. Only if you bend the rim badly enough to hit the frame or seriously warp the disc brake rotor do you have serious rubbing issues.
And, lastly, disc brake road bikes typically accept wider tires than rim brake bikes. This is because rim brakes need to be small in order to provide sufficient power. This usually means more tire clearance on a disc brake bike than a rim brake model.
Why disc brakes shouldn’t be on “every” road bike
As you see, the advantages of disc brakes are many, however there are drawbacks, such as:
- Disc brakes are more complicated and difficult to setup and repair for average people than rim brakes, especially so with hydraulic discs
- Disc brake systems result in a slightly heavier road bike, due to required reinforcing of the fork and frame where the calipers attach plus the weight of the metal rotors
- Related to the required reinforcing, most new disc brake bikes feature through-axle wheels, which are slightly slower to remove and install than standard quick-release wheels
- Most through axle wheels require tools for removal
While it usually creates less drag, disc brakes are just as likely to rub as rim brakes, and any rubbing is annoying
- Roadies who have grown to love the minimal look of stealth road bikes may have a hard time appreciating the look of rotors
- If you swap wheels between bikes, disc brake wheels are incompatible with rim brake wheels and vice versa
Those are the main reasons I told Andy that if I was new bike shopping, I’d be looking for a rim-brake model not a disc-brake model. I realize it may sound like I have something against disc brakes.
Actually, I wouldn’t be without discs on my mountain bikes and gravel/cross bike (I use both cable-activated and hydraulic). If I was building a commuting or shopping bike, I’d put them on it, too.
But for Andy, who rides just like I do, I lean toward him sticking with rim brakes. And, hopefully, he has enough information now to choose which braking setup is right for his new dream machine. Now that I’ve had my say, what would you tell Andy?
Ride total: 9,150