1979 GS 1000 rear brake "torquing"

[jknappsax]

We finally got a weekend with no rain on Saturday, and I finally got the GS inspected! Felt good to be riding. I had replaced the spokers with cast wheels and Dunlop GT501s.While out riding, I noticed what at first felt like the rear wheel sliding a little when applying the brakes, but I think is actually the rear wheel "torquing" when I apply the brake. I've checked that the wheel bearings don't have any slop, the axle and adjusters are tightened properly, and that the swing arm doesn't have any lateral or twisting sloppiness. The wheels are centered properly in the forks and the swingarm, and are in line with each other. The rear tire is brand new, as is the front. I haven't seen anything when letting the back wheel spin in first on the center stand and tapping the rear brake, and obviously can't look at the rear wheel closely while riding. Other than the above items, does anybody have any further items to check? Thanks.

[Steve]

Check how hard you are pushing on the brake pedal.

The 501s are not the best tire, and you say they are new, so that combination might actually be sliding under you.

.

[KEITH KRAUSE]

Without feeling it myself, I'm not sure what you have going on.
Is the swingarm-to-caliper arm brace torqued correctly?
How much did you torque the axle nut?
Changing from spokers to mags, are the complete assemblies (wheel and spacers) the same width?

[TheCafeKid]

Without feeling it myself, I'm not sure what you have going on.
Is the swingarm-to-caliper arm brace torqued correctly?
How much did you torque the axle nut?
Changing from spokers to mags, are the complete assemblies (wheel and spacers) the same width?

No..If I remember right there is an outboard spacer on the rear that isnt used on mag wheels...

[Big T]

No..If I remember right there is an outboard spacer on the rear that isnt used on mag wheels...

No outboard spacer on spoked 1000s

Just a washer and nut

[Steve]

No..If I remember right there is an outboard spacer on the rear that isnt used on mag wheels...

No outboard spacer on spoked 1000s

Just a washer and nut

I think he means "outboard" as in "between the caliper and swingarm" not "outside the swingarm".
"Inboard" would be between the the caliper and wheel.

Am I close, TCK?

.

[rphillips]

The spacer between the wheel & caliper is a different width, I think the spacer is appx. 1/4" wider (thicker) for the cast wheel. I don't think that spacer would cause your problem. I don,t think the wheel will turn at all with the wrong spacer. Sounds exactly like a rear wheel that isn't tight, but I know you already checked that. ???????

[rudy]

+1 on the wheel that ain't tight. I forgot to tighten mine when I first took it out. Felt REAL weird. I'd say check it again.

[jknappsax]

I changed out to the proper spacer for the mags

The bearing flinger on the spoked wheel was about 1/4" longer than on the cast wheel; I changed that out for one of the proper thickness, as the longer one would not allow the disc to line up properly in the caliper. I did go back and check the tighness of the rear axle, and noticed that the wheel adjuster on the right side had allowed the move forward about 2 gradations on the adjuster marks, and I reset this and made sure all was tightened properly. I tested the rear brake, and it was much better, though I still felt a little vagueness, but as Steve mentioned, it is a brand-new tire, and that's possibly what I'm feeling. The one thing I'm not sure about is the length of the rear axle; the one from the spoker is a little longer. It still tightens completely, but the notches in the nut are further inboard than the holes in the axle threads, so I've got to safety-wire the nut instead of a cotter pin. Now I notice that the front brake doesn't feel very powerful, even though the line is stainless steel, and the fluid level is correct. At least it's on the road finally; lousy weekends haven't let me work on it much lately.

[Steve]

The one thing I'm not sure about is the length of the rear axle; the one from the spoker is a little longer. It still tightens completely, but the notches in the nut are further inboard than the holes in the axle threads, so I've got to safety-wire the nut instead of a cotter pin.

You could also put a couple of washers between the swingarm and the nut to space it out a bit.

.

[jknappsax]

My thought exactly, Steve!

[KEITH KRAUSE]

Regarding the front brake feeling weak, if you just assembled it the pads may not be seated perfectly with the rotors yet (?). Also very commmon is the rotors can get dirty from handling and the dirt film will greatly diminish braking power.
After cleaning my bike I always spray some brake cleaner on a towel and wipe down the rotors several times. Even then, the first couple of lever compressions can feel a tad weak but it returns to normal quickly.

[jknappsax]

Keith, thanks for the suggestion. I was planning on taking off the front caliper this weekend to get a better eyeball on the situation, so a good cleaning on the rotor, pads, and caliper assembly (short of taking it apart and rebuilding) is definitely next on my list. I had only planned on these tires and wheels until this winter, when I plan to install a 92 GSXR 1100 front end, and a GS 1100 swingarm, and the Gixxer wheels withrotors, calipers, master cylinders. Now that she's on the road, I may wait until NEXT winter; I don't want to be without a streetable bike for another summer.

[TheCafeKid]

No outboard spacer on spoked 1000s

Just a washer and nut

No no, Steve is right, I mean twixt the caliper hanger and the swinger. Outboard of the wheel. Now that i think about it tho i may have that reversed. The Mags may have used the spacer and not the spokies...One doesnt and one does, and use of one or lack of use will cause alignment problems in the caliper, causing it to drag..guess how i know?? LOL

[jknappsax]

I've changed from spokers to cast wheels before. On the GS 1000 there IS a spacer between the swingarm and caliper mount, on both spokers and cast. The only difference is the length of the bearing flinger, and once I installed the correct flinger, it all lined up.