GL1200A Rear End Rebuild

The Problem

The tag end of 2003, we started noticing noise in the drive line of our 1986 Aspencade.

It turned out that the inboard bearing had spun in the rear wheel, and had wallowed out the

aluminum hub. This is not a good thing to have happen, as the wheel is not generally considered repairable and the replacement parts from "Big Red" are quite expensive.

The Cure

Having heard through several grapevines that the final drive from a 1500 would fit the 1200, and that the rear wheel from the 1500 should fit, I decided to try this solution.

Three minor modifications were necessary, the four holes in the rear end of the 1200 driveshaft housing need to be drilled to match the larger size studs found on the 1500 drive.

Also you have to mill or grind the strut for the 1500 brake caliper mount to allow it to fit in the 1200. Third modification is to grind the end of the left lower shock absorber stud to allow the insertion of the stud and prevent contacting/damaging the rear rotor.

The single spacer from the 1500 is used in place of the dual spacers from the 1200.

The rear tire is actually better centered than with the original 1200 setup.

With the expertise of fellow "Winger" Bob Hitch, and some help from me, and the changeover was completed.

Problems

Problem #1: As the Avon of choice (160/80 B16) is 0.3 inches wider at the shoulder and 0.4 inches greater radius than the OEM Dunlop when properly inflated, there arises a possible conflict of interest  with the rear fender,

The primary point of contact is at the top of the fender on the left side.

When riding solo, you will probably get away with no to low pressure in the rear shocks.

When riding two up, depending on the weight of both the rider and the passenger, you may need to run maximum allowable pressure in the rear shocks.

The above listed potential problem can be avoided by using Avon's 150/80 B16 77 H Venom X.

The 150/80 B16 77 H Venom X is rated at 908 lbs., and is 0.7 inches narrower than the 160/80 tire.

Problem #2: Unknown and unseen at the time of assembly by either Bob or myself, the original rear brake hose had enough slack between the front connection point and the factory supplied clamp that it had developed a bend in the direction of the tire. The 160/80-16 Avon "Venom" was wide enough to contact the brake hose, and it took about 200 miles to wear through.

Fortunately, we were not in an emergency situation when we lost the rear and one front rotor braking, and were able to proceed with caution the last few miles home.

This was fixed when installing a new hose, by using two heavy duty Panduit straps (zip ties) to anchor the hose to the top of the swingarm in front of the factory supplied clamp assembly.

Note: The factory supplied clamp assembly may have to be slid approximately 0.25 inch towards the front connector.

Since the modifications, my wife and I have put over 7000 miles on the bike, and have had no additional complaints.

Riding two up with the increased tire size and the GL1500 rear rotor, the braking is incredible!

Note: If total weight of passengers exceeds 420 lbs., you will not be able to use the 160/80-16 "Venom X" tire as it will rub on the left side at the top regardless of pressure in rear shocks.

Instead, use the 150/80-16 "Venom X". The tire is actually slightly narrower that the OEM Dunlop, but has a load rating of 908 lbs.

The boss on the right is for the axle, and is not modified.

The one on the left, is for the left shock absorber lower bolt, and needs to be milled or ground to approximately 0.510 inches to fit into the 1200.

Note that all grinding is done on the side away from the wheel.

Also note the partial grinding of the strut webs.

The grinding on the webs of the strut is necessary to allow the strut to rotate into its final position without springing the rear swingarm assembly.

If you don't properly grind these webs, the strut will twist from its proper position also twisting the rear brake caliper causing rapid wear of the brake pads and destruction of the rotor.

Closeup view of the reworked areas.

View from bottom of caliper strut showing in detail the reworked areas.

Note that the original caliper does not have to be removed from the system as the 1200 and 1500 use the same rear caliper

Since the recommended Dunlop "Elite II 491" 160/80B16 for the 1500 has a load rating of only 853 lbs. @ 41 psi, I chose to replace this with the Avon "Venom X" 160/80 B16 TL with a load rating of 1019 lbs. @ 49 psi. We also use the matching "Venom X" tire on the front wheel in the appropriate size for the 1200.

This tire fits well into the rear swingarm assembly, and greatly increases the loaded safety factor when riding two up and pulling a trailer.

For those of you with unmodified 1200's, consider these rating facts.

The GL1200A, with 2 well fed riders, saddle bags and trunk loaded, and pulling a trailer with cooler chest on the drawbar can approach 900 lbs. loading on the rear tire. This does not leave much of a safety margin with an OEM tire on a stock bike, and exceeds the tire rating of the OEM tire for a GL1500.

The Dunlop "Elite II 491" MV85B15, has a load rating of 910 lbs. maximum @ 41 psi., and the Avon "Venom X" 150/90 B15 TL has a load rating of 993 lbs @ 49 psi.

In all cases, you will find that the Avon's not only give superior road life expectancy, but greater traction and far less "trolley tracking" on grooved pavement and open steel deck bridges.

Additional photos below text

The camera saw it, but we didn't.

Make sure that the brake line to the rear caliper is strapped to the top of the swing arm with at least one heavy duty zip tie.

If the hose contacts the side of the tire, you will lose two out of three calipers for stopping until you replace the line.

Note the size of the rotor.

Use the foot brake with caution when riding one up, as there is tremendous stopping power with a 315 mm. rotor.

There is an indentation at the top of the rear fender that will rub on the side of the tire when riding two up if you do not inflate the rear shocks sufficiently.

Make sure that the caliper support strut pivots freely into place.

This is why you have to grind the strut webs as well as thinning down the anchor boss.

Any binding along the side of the swing arm will cause twisting which will cause rapid wear of the pads and rotor.

Approximately 3/16 inch needs to be ground off the tapered end of the lower shock bolt to prevent contact with the rotor.

GL1500 final drive and rear wheel in place.

A lot less modification than mixing 1200 & 1500 parts.

That's 6.6 inches of tire width stuffed into a 1986 GL1200A.

Almost done. Only the trim needs to go back on,

There is approximately 1/2 inch between the side of the tire and the driveshaft housing on the right side of the bike.

This is the Avon replacement for the GL1500 tire.