Brake arm alignment

[tobyd]

Hello,

New to the forum and recently returned to biking via a cheap, old GS500E. Been trying to sort out some of the neglect on my '98 GS500e and generally tidy it up but come across a problem with the rear caliper. After a ill thought out drill-out-the-rear-fluid-reservoir-screws fail i had to dismantle the master cylinder and rebuild with new seals, then whilst bleeding the system down afterwards I thought i'd push the caliper pistons in where upon I discovered that the pads are worn in a 'bad' way.



That the Inner (worn almost the the backing plate) one is so bad whereas the outer one was alright made me think the that caliper piston on the outside was stuck so the inside was doing all the work. However, new EBC FS063 pads later, a ride, an examination and I think there might be a problem with the brake arm instead



It was a right sod getting the caliper back on, first attached to the arm, then slid over the disc, then aligned with the caliper bolt-holes. The upshot is the rear wheel is binding, if i detach the arm, as per the picture it runs quote well but with the arm attached its dragging quite badly. To the point that when i tested the bike earlier the disc at the back was too hot to touch with very little use. If the arm is constantly pushing the inner pad onto the disk that would explain the heat and the bad brake pad?

Anyone got any thoughts?

Is there a likely suspect for why the arm isn't aligned correctly? it looks too far mis-aligned to be the rear wheel alignment (I can add more 'alignments' if anyone wants) but the other neglect on this bike makes me think it's a possibility? Crash damage? the rest of the bike is grubby but doesn't look like its been stuffed into hedges and oncoming traffic too much?

So small update, the brake arm itself might be the problem - I've aligned the back wheel - it was off by a few mm. Then pulled the brake arm itself. Needed a ton of plus-gas at the frame end and some persuasion. If the arm loosely attached it is a very nice fit but the moment i nip-up the castellated nut the arm pulls outwards again. The frame-end bolt is pretty crusty and there is a fair bit of play between it and the nut end.



It almost looks like there should have been a clip or washer where the threads begin, although there is no room through the bracket for this?

[gsJack]

Once the torque bar is bolted in place and tightened it's a rigid triangle, there is no movement at either end.  See parts:

http://shop.shspowersports.com/fiche_section_detail.asp?section=92832&category=Motorcycles&make=SUZUKI&year=1997&fveh=2104

If anything is causing a problem I'd guess it's a caliper piston sticking causing your uneven pad wear..  I aways popped the pistons and cleaned them with steel wool or those green kitchen pads to get the crud off when installing new pads.

[tobyd]

Hello gsJack,

Its that the torque bar is out of alignment that I think is causing the pad wear - the moment its tightened down the wheel drags, I think this is why the worn-down pad is so bad, the caliper is always being forced away from the bike so the inner pad is constantly engaged (more than the usual) against the disc. I'm perplexed why that bar slips out 5-10mm (as per the first picture) as soon as its tightened down at the frame bracket - it's perfect between the two mounting points until then!

Thanks for the link - it confirms that there are no extra spacers or anything. I read in another post here that there is a spacer on the rear axle, but that looked like it was swing-arm side so if it was missing this would be even more pronounced?

I'm tempted to try adding a washer on bolts head -> bracket interface to even out how it sits. I think the whole arrangement rotting in place wouldn't push itself out of place this much.

[gsJack]

I wouldn't be too quick to start modifying that rear brake design, it's worked out just fine for me while wearing out 15 sets of rear pads evenly on 2 GSs over 180k GS miles.  If you have that umbrella shaped spacer 5 between the caliper bracket and wheel bearing and everything else across the axle is tight up then the rotor should fall between the pads without dragging on and wearing out the inside pad.

How about that spacer 9 you referred to as a missing spacer, is it there on your bike?  It's easy to loose and could be contributing to your problem.  If you pull the axle and lift the wheel and pull the spacer 10 from the seal 16 you can see if spacer 9 is there inside the cush drive bearing 15 that rides on it.

http://shop.shspowersports.com/fiche_section_detail.asp?section=92834&category=Motorcycles&make=SUZUKI&year=1997&fveh=2104

[gregjet]

This is what the rear axle spacers should look like. They are is order looking from the rear ie the left spacer is the one in the sprocket, then the interbearing one between the sprocket carrier and the left wheel bearing, then interbearing spacer then the disc side spacer. If any of then isn't there or is the wrong one you may have a spacer problem. These are off a 2005 but I don't think they changed at all.




Just had a thought. It may have been hit sidways and the rear swingarm is bent sideways? Might be worth a check. That usually makes the wheel not straight if you use the dent marks./.

[tobyd]

Ah great! I'll take that to bits tomorrow and see what is / isn't there. Thanks for the pictures and diagram, should make it easy to trace if anything isn't right. It does seem like something might have escaped at some point given its a good 10mm+ out of slotting together happily.

Nothing sticks out as obvious damage, the swing arm looks fairly square and even on either side. I might take a caliper to it and check a few dimensions across either side and see if they are about right. Trouble is this bikes been through quite a few owners, 44k and the history file is a bit thin so knowing whats happened to it is a bit tricky. I might try that 'string test' now the rear wheel is even between swing arm and axle on either side and see if its aligned front-to-back, might give some clue if the thing is mostly straight.

thanks again!

[tobyd]

Ok, so all spacers accounted for and all in the right place. The longer cylinder is inbetween the two bearings, can see it so not pulling them.

I'm a bit concerned however by two marks, about level with the brake host bracket, either side of the inside of the trailing arm, they look a little too imprecise to be from the factory?

Left Side


Left side closer


Right Side


Not sure how obvious that appears but on either side there is an impression as if the metal has been hammered in slightly slightly. I don't know if this is by design (as its a box section and curved) or because its been poorly repaired? I'm not sure if either leg of the swing-arm has been painted given how crusty the middle section is.

Jumping the gun completely, how much of a sod are they to change? It only looks like a couple of bolts top and bottom?

All the rust and grot is available at the right price

Update: theres a load of these on eBay and they seem to show similar impressions at the same points - so perhaps just a forming artifact of box section design after all?

[tobyd]

And more! Looks like its ok now! Reassembled it all to keep all the bits together, cleaned up the worst of the grot. Thought i'd see how to align the chain and adjust it up (thanks Slippry Mongoose!) since I was already there and covered in crud. Then trial fitted the other bits and pieces and it all was really smooth.

The torque bar seemed to be very particular to where the brake hose hoop went on the frame mount which I thought was odd? If I put it between the washer and castellated nut it messed up the alignment but between arm and washer it the whole thing was fine?

Just been out for a quite ride around town came back and the rear disc was warm but I could grab with both hands immediately after parking. Bike pulled better too, especially from a standing start. I'll check all the brakes over in a few weeks and check the alignment, I did the axle bolts up tight but my torque wrench is on a borrow 200 miles away so I wasn't certain. The rear wheel span nicely once parked up on the center stand too - before it barely managed anything after being pushed.

Anyway, thanks again for taking an interest - there might be various how-tos I can post since there are various things that need attention and the nasty nexxus exhaust is probably the first.

[pliskin]

You should consider replacing your chain. From the looks like in one of your pics it looks like several of the links are stiff. It should lay flat and be slack but yours looks all bunched up on top of the swingarm.

[J_Walker]

the "hammered in" effect, is how they bent the swingarms in the factory, no need to worry its normal.

[tobyd]

re: the chain - it was cable tied to various points to stop it dragging on the ground, probably looks pretty haggard in those pictures! I runs quite smoothly once re-attached to the sprocket with the wheel back in place. It's about middle of the adjustment points with 20mm of free-play and theres not a whole lot of play on the farthest link on the rear sprocket either.

Cool, thanks for confirming those 'dents' in the swing arm, it looks a bit haphazard how it was formed but i suppose with a box section you have no other option.

Anyhow, the thing seems a whole lot happier, i'll take it out tomorrow and give it a bit more of a test. The rear brake needs some more bleeding as its not 100% yet but I'm waiting on a replacement master cylinder -> frame screw (trying to round itself off) to properly tighten the MC back into place before I do this. Makes a world of difference not having it binding anyway!

Thanks again