How-To: Fit Oversized Rotors

2 months ago | Words: Ollie Sharp | Photos: IKapture

This content was originally published in Issue #24 of Transmoto Dirt Bike Magazine, 2012

You don’t need to be a Pro to find an excuse to install an oversized front disc kit to boost your bike’s stopping power. Upgrading from the standard 240-260mm disc to a 270mm unit increases stopping power through the disc’s additional diameter and surface area. Not only do you benefit from more power at your fingertips for less input, you also gain much better feel through the brakeline. Most aftermarket brake kits will include the oversize disc and caliper mount, and installing the lot is super-easy – even for a first-timer. So grab your tools and follow this step-by-step guide to installing a GYTR brake kit onto a 2012 Yamaha WR450F.

Tools You’ll Need

● Loctite 243.
● 10mm T-bar.
● Brake cleaner.
● Wet & dry paper.
● Waterproof grease.
● 4 & 6mm Allen keys.
● 22mm axle spanner.
● Flat-blade screwdriver.
● 12 & 13mm spanners or sockets.

Break It Down

With your bike on a stand, first grab your 10mm T-bar and remove the two bolts that hold the caliper to the left fork leg. At this stage, it’s fine to let the caliper hang via the brakeline. Now remove the fork’s axle-clamp pinch bolts and the axle bolt. Slide the axle through and remove the front wheel.


Lie the front wheel down with the brake disc facing back up at you. Grab your 6mm Allen key and remove all the bolts. With the OEM disc stripped from the hub, grab a small section of wet and dry paper (very fine sandpaper) and lightly sand the exposed bolt-holes on the hub to remove any leftover Loctite. Lie the new disc onto the hub, align the holes, finger screw the bolts in – after first dabbing a smidgen of Loctite 243 to their threads – and tighten each bolt in a star pattern to the manufacturer’s torque specifications (usually 8-10Nm).


With a flat-blade screwdriver, remove the locking cap on the brake pads’ retaining pin. Then remove the pin itself, using a 4mm Allen key. Once the pads have dropped out, use your thumbs to gently push the caliper bracket arm off the caliper. Clean the caliper shafts with a rag and extract the steel spring-loaded retaining clip from the caliper bracket and the rubber bootie that covers the piston hole. Now grab your 12 or 13mm ring spanner – or deep-reach socket – and remove the piston shaft on the OEM caliper bracket and bolt this into the oversized caliper bracket. Finally, attach the spring-loaded brake pad clip and rubber bootie.


Before installing the oversized caliper bracket to the standard brake caliper, first apply a small coating of waterproof grease to both shafts on the bracket and caliper and stick some in the bracket’s hole. Slide the two units together, slip the new brake pads in (making sure the top of each pad locks into the spring-loaded steel clip), and insert the brake pads’ retaining pin and locking cap. After all that fondling, it’s common for the fluid in the brakeline to push the brake caliper’s pistons out, thereby reducing the gap between the pads. If so, gently coax the pads apart with the flat-blade screwdriver


With any new piece of manufactured metal, there’s always a high chance that it has some sort of anti-corrosion treatment, and the last thing you want in the case of your front brake is for that coating to glaze onto your brake pads. To prevent this, simply take your wet and dry paper and lightly sand the disc’s inner and outer surfaces. This will also give the pads a chance to bite onto bare metal and bed-in quicker.


Install the front wheel by approaching the forks head-on and leading with the brake disc on an angle. As soon as the brake disc slides between the pads, wiggle the axle back in and then lightly tighten the axle nut back up. Now gently tighten the fork’s axle-clamp pinch bolts, starting with the bolts on the caliper side first. Before torquing them up, give the front wheel a spin or two and grab a handful of brake each time. The sudden jolt will help centre the fork legs on the axle. Now you can torque the pinch bolts up to roughly 10Nm and give the axle nut one last whirl to double-check it’s secure.

Expert Tips

● Don’t leave your front brake caliper hanging at the end of the brakeline for extended periods of time. Gravity will eventually have its way and you’ll run the risk of creating cracks in the line and potential air leaks through the bolts.
● Although replacing the front brake pads with some fresh units when installing a new rotor isn’t mandatory, it comes highly recommended so that the pads can bed into the new rotor.
● Once the front-end is back together, generously spray the front disc and pads with brake cleaner to remove any metallic dust from the sanding process.

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