Fat Is Where Its At !!
Making Room for Wider Tires

By Jerry Ferguson

Have you ever considered installing a fat rear tire but thought the fit might be a bit to tight ? Well here is a tip that will free up a little extra space you may need to accommodate that oversize tire. In a recent V-Boost issue we listed many of the available tires that will fit the Vmax and some that may be a marginal fit. The Metzler ME880 170/80-15 is just such a tire. A call to Metzler confirmed that the stock 3.5 inch wheel width is within specification for this tire application. However, without a little more clearance this tire will rub on the shaft side of the swing arm. There are a few brands of 170 size rear tires that will fit but for those of you who choose the marginal ones or just desire a bit of extra swing arm-to-tire clearance this may be the ticket for you.

This procedure basically moves the washer located on the rear axle between the brake arm and the swing arm to the other side of the wheel between the differential drive unit and the wheel drive hub. This provides extra clearance for the tire on the swing arm side of the tire equal to the width of the washer, about 1/8 inch. A bit of additional clearance may be obtained by making sure the differential unit is mounted to the swing arm as far to the right hand side of the bike as possible.

Place the motorcycle on the center stand, or something appropriate if the stock center stand has been removed (sometimes necessary for fitment of an aftermarket exhaust system).

 Remove the license plate to facilitate removal and installation of tire/wheel assembly.

 Remove the two bolts holding the rear brake caliper to the brake arm and swing the caliper out of the way. It will rest on the outward side of swing arm/shock or if you remove the right side shock it will simply sit on the floor.

 Remove the rear axle cotter pin, (pre-'96), axle nut, and washer on left side of bike. Loosen the axle pinch bolt on the right side of bike. You should now be able to pull the rear axle out from the right side of the bike while lifting the tire/wheel (to get the tire/wheel weight off the axle; it really isn't going anywhere at this point as the drive hub is still firmly seated in the differential unit). The washer mentioned previously on the right side of the wheel should drop to the ground when the axle is removed.

 The wheel will be continue to held off the ground as it is still seated in the differential drive unit. Pull the brake arm toward the rear and up past the top of the tire to get it out of the way. You may need to loosen the bolt holding the brake arm to the brake torque rod to swing it out of the way or it may simply be removed if you want some extra elbow room.

 You should now be able to pull the tire/wheel assembly to the right and away from the differential assembly while supporting its weight; it should drop to the ground. Roll the tire/wheel assembly out to the rear of the bike. If you have a very large tire already fitted to your wheel, you will probably need to let all the air out of the tire so it will slide between the differential and the right side of the swing arm.

 This is the prefect opportunity to clean up the inside of the differential and wheel assemblies, the brake arm, the rear caliper, and the axle. Maybe even your wheel!

 Before reassembly (and after cleaning), apply bearing grease to the splines inside the differential drive unit and lightly coat the rear axle, (moly grease is recommended).

 With the rear wheel off and out of the way you also have an opportunity to make sure the differential unit is mounted to the swing arm as far to the right as possible to take advantage of any extra clearance this may provide. Loosen the four nuts that hold the differential on to the swing arm. Just a bit loose; allowing the unit to be moved slightly with a few mallet taps. Tap the differential to the right side of the bike with a plastic or rubber mallet, and tighten the four nuts. It may or may not move at all, depending on factory assembly and tolerances.

 We are now ready for reassembly. Take the washer that was previously between the brake arm and the swing arm on the right side, (don't confuse it with the thicker washer that came off the left side from underneath the axle nut). Place this washer into the differential unit spline area near the center where the axle hole is. Insert a screw driver or other suitable instrument from the outside of the differential unit and into the axle hole to keep the washer in place until we can slide the axle back in through the wheel, (see photo).

 Roll the tire/wheel assembly back in between the swingarms and lift it up and onto the differential unit engaging the splines on the wheel and drive unit to hold it in place. Push the wheel to the left to make sure it if firmly seated in the differential while guiding the screwdriver through the center of the wheel hub. Once the wheel hub is fully seated it will press up against the washer we placed in between the hub and the drive unit and keep it from sliding our of position.

 At this point you may want to look into the axle hole from the outside of the drive unit to see if the washer in centered. If not, you should be able to move it slightly to center it before installing the axle, (leave the screwdriver in place until you are ready to push the axle through just in case).

 Swing the brake arm down and forward; make sure it is aligned between the wheel and the swingarm.

 Slide the axle back through the right swing arm, brake arm, wheel, washer (in between the wheel/differential unit), and differential. If you still had a screwdriver inserted to hold the washer in place, it should have been pushed out at this point and the axle should be protruding from the outside of the differential.

 Re-install the left side axle washer and nut and torque to the proper specification; reinstall a new cotter pin if so equipped.

 Re-install the brake caliper making sure the brake pads have been spread to facilitate sliding it over the brake rotor. Install the caliper retaining bolts and torque to the proper specification.

 Torque the axle pinch bolt on the right swing arm to the proper specification.

 Re-install the license plate (we wouldn't want you to get pulled over!).

 Be sure to your tire is inflated to the proper pressure and check for tire-to-swing arm clearance on the left side. You should have enough clearance to fit many, (perhaps all), of the 170 series tires available. Remember, the tire will expand when it gets hot under a load.

This procedure has been tested for years under heavy load conditions, (high speed, wheelies, etc), on many different Vmaxes with the long lived Metzler ME88 and the more recent replacement ME880 170 series tires with no apparent adverse affects to the drive engagement splines or any of the drive gear. Some rear ends do have minimal clearance due to manufacturing tolerances and the tire may still be too close after it heats up. This seems to be a rare occurrence but if it is encountered it would be wise to make sure the entire swingarm is not severely out of alignment.

A special thanks to Brad Thomas of Mesa, Arizona for sharing this tip. His many years of experience in the application of this modification on so many different Vmaxes allows it to be recommended without reservation.