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Mechanic’s Corner: Disc Brake Rotor Wear

mechanic working on bicycle

We’re deep into the riding season, here in the Northern Hemisphere anyway. It’s time to consider the preventative maintenance that can keep your riding free of clicks, creaks and pops. In addition, wearable items are starting to see the effects of your daily mileage. To help maximize your Team Edition and Ride Prep Tool Kits, and any one of our premium bike repair stands, a couple of weeks back we took a look at the most common wear items today we’ll dive a little deeper. 

DISC BRAKE ROTOR MAINTENANCE

With the ever-increasing popularity of disc brakes (hydraulic and mechanical), one of the easiest bike maintenance procedures is to inspect disc brake rotors. This maintenance tip suggests a quick way to insure you are getting the best performance from your braking system.

WHY DO I NEED TO DO THIS?

Disc brake rotors endure a large amount of heat and friction on a regular basis. They can withstand large forces and are responsible for slowing our bikes down, which they do quite well. But as a result of these physical demands, it is a good idea to check them for wear regularly. Disc brake rotors will typically last through 2, maybe 3 pairs of brake pads (pad material and riding conditions influences this), but it’s never a bad idea to add a thickness check to any regular maintenance schedule. 

DISC BRAKE ROTOR MAINTENANCE – THICKNESS INSPECTION

Rotor inspection is easiest with the wheel removed because the minimum thickness standard is etched quite small on the rotor. This print is located on the outer surface and is presented something like  “Min. TH=1.5”. This is interpreted as “minimum thickness of 1.5mm”. Anything less than 1.5mm means it is time to replace (for this particular Shimano rotor). This measurement is not the standard for all rotors – for instance, Hayes is 1.52mm, Shimano is 1.5mm, Sram minimum disc brake rotor thickness is 1.55mm. However, these aren’t guidelines, but rather highlight the fact that there is no universal standard and looking closely at your specific rotors is crucial.  

Use your Feedback Sports Digital Calipers and measure the thickness at the braking surface, ensuring you have as much of the rotor braking surface within the calipers jaws (as seen). With such precise measurements, it’s good to check several points on the rotor, multiple times. 

If your rotors measure above the indicated minimum thickness then you’re in the clear. If your digital calipers measure below, contact your local bike shop (LBS) to purchase new ones. Your shop will have questions, so be sure to take note of your rotor size (140, 160, 180, 200, 203mm, etc.) , mounting style (centerlock or 6-bolt), and manufacturer of your disc brake caliper.

Since you’ve got the wheels out it is a good idea to double check your centerlock lockring or your rotor bolts for torque. The Team Edition Tool Kit includes the Bottom Bracket + Lockring Tool (which can manage standard and over-sized centerlock lockrings) and our Range Torque + Ratchet Wrench can handle 6-bolt, T25 torque specs.  If you’re replacing the rotors, be sure to face any writing on the rotor outward from the hub as pictured. 

Now that you’re confident you understand the mechanical status of your rotors, reinstall the wheels and get back to riding! Or replace them if needed, of course!

This simple check, and so many more to come, can be done with little mechanical experience. As we always say, with the right tools and a quality bike repair stand, anybody can service their bike. 

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Mechanic’s Corner: Summer Maintenance Essentials with Mike Gavagan (Gav The Mechanic)

bicycle tools

It’s mid summer, and all the miles on the bike are adding up – it’s time for some basic maintenance to your bike. Fortunately, some of the most common wear items and how to check them over are well within the grasp of even new mechanics. Mike Gavagan, seasoned technical veteran, will share some tips! 

Tires and Sealant

The classic signs of service are excessive wear on the tread, cuts or tears, worn knobs, flat spots, or visible tire casing. When in doubt, replace the tire. And as you’ll no doubt notice, rear tires wear faster! Use the Dual-Sided Pick to pull out any debris from the tire – glass and small pieces of metal can sit in the tire, just waiting to be the source of your next flat. 

If your tires are in good shape and you are running a tubeless tire system, it may be time to refresh your tubeless sealant. You can do this without breaking the seal/bead of the tire . Using your Valve Core Wrench, remove the presta valve core. Using a sealant injector to add 1-2 oz of sealant to your tire (check the manufacturer’s suggested volume). Inject the sealant at the 6 o’clock position. After the sealant has been injected rotate the tire to the 12 o’clock position and then remove the sealant injector. Trust me, you’ll avoid a lot of mess if you do this. Finally make sure the valve nut is finger tight.

If your tire has to be replaced or you want to visually inspect how much sealant is left in your tire, you’ll need to break the bead and remove at least one side from the rim. This is also a great time to clean out any old or dried sealant from inside the tire. This will allow your wheels to spin more balanced. When tubeless sealant dries, it forms a sealant ball, or simply dries to the inside of there tire like a thin skin. Using a set of Steel Core Tire Levers remove one side of the tire. If you are replacing the tire remove the old tire from the rim and install the new tire in the correct tread direction but not installing the tire completely.

Dump in the recommended sealant volume and install the tire bead back onto the rim. You will likely need a high volume floor pump, charger pump or a compressor to re-set the tire bead onto the rim. Pump it back up until the tire seats completely – don’t be alarmed if you hear a loud pop, and don’t exceed the tire’s maximum pressure. Once the bead is seated on both sides, you can then set your tires back to your preferred riding pressure.

Brake Pads and Rotors

Check to see that there is an adequate amount of brake pad left – this goes for disc brake and rim brake systems. Many rim brake pads will have a small line indicating their wear limit. If you are running disc brakes, you want to see about 2.5mm of brake pad material left. If the brake pads are worn past this point it’s a good idea to replace them. Also check to see if the pads are wearing evenly. If one is significantly more worn than the other, it could result in the pad backing contacting the rotor and generally poor braking, as well as damage to the rotors. 

If your brake pads are worn down to the metal it is most definitely time to replace not only the brake pads but the rotors as well. More about this topic in our next post!

Drivetrain

If you are experiencing poor shifting regardless of derailleur adjustments, excessive noise from your chain, or excessive chain slap, it’s probably time for a new chain and or cassette. If the cassette has excessive burring on the teeth of the cogs a brand new chain may not sync with old cassette and may slip or pop in certain gears. Shifting performance will also suffer. Other ways to look for wear on your drivetrain, is if the teeth of the cogs, or the teeth of your chain rings have a very sharp shark tooth profile on the loaded edge. If you notice this shark tooth profile then it is time to replace. Our chain tool is ready to do the job, even for new Sram AXS 12-speed drivetrains. 

Visit Your Local Bike Shop

If you’re uncomfortable making any of these repairs, or unsure of if you should replace a part due to wear, always be sure to take your bike to your local bike shop. But having this information can at least help you be informed, and help you and your mechanic communicate. 

Mike Gavagan is the owner and sole mechanic of Gav the Mechanic. Mike has years of retail service experience, but has also worked for numerous pro and amateur teams such as Drapac Cycling, Specialized S-Racing, Rally UHC, and Slipstream Sports.