550 drum brakes - new shoes seem wimpy

Okay - other than my MSF, which was several years ago, my 550 is the only bike I've ever really ridden. Also, for the past few years, it hasn't had the greatest of rear brakes. It wasn't a big deal for me - I've always been a two-brake stopper.

HOWEVER, with all the other stuff I recently did with the bike, I finally got around to replacing the rear shoes, only to find that they're good for slowing the bike down - but not really for stopping.

Correct me if I'm wrong, but ideally, with new shoes, I should be able to lock that rear tire down, right? (And before the lectures start, I know I don't want to lock the rear tire, ever, but I should be able to, yes?)

When I had the wheel and brake cover off, I did notice that the drum was VERY smooth - almost glassy. I took some medium-grit hobbyist paper (synthetic, not sand) and went around the inside of the drum some, and it felt rougher, but again, performance is not optimal. I can stand on the pedal, and the bike does slow...but I have to use a front/back combo to get it to stop.

I feel like the rear brakes are intended to be much more aggressive. Am I wrong? And if I'm not, what else can I do to fix it?

 

For one answer, yes, you should be able to lock it up. Mine sure can, without excessive force. Do/did you have any oil deposits inside the drum? If your drum did get glazed from excessive heat, you may either have to have it resurfaced, or just replace it. I know not all drums can be turned, so it's hard to tell. But I know once their glazed, the will really suck at stopping power.

 

I'll argue that you DO want your back break to lock up. At lockup, braking force is maximum and given that the rear brake supplies about 20%+ of your stopping force, it does factor in significantly. I am glad that you use both brakes but the rear should work optimally, just like the front, although not as critically as the front.
You've done everything I would have done to fix the glazing, now replace the rear brake shoes, get the pivot points lubed up and the rod adjusted correctly.

 

soundman502 - I'm going to guess that's my problem, then. I didn't see any oil inside the drum at the time, but I can check again, since I need to take the exhaust off this weekend anyway - I might as well pull the wheel and open it up.

Robert - the "don't want to" comment came about because of how much they pounded on "don't lock your brakes" at MSF, and also (if I remember correctly) in Hough's Proficient Motorcycling. Believe me, I'll feel a lot safer when good pressure on that pedal brings me to a screeching halt.

Question - on the diagram in my Clymer guide, the drum looks to be an integral part of the wheel. Am I reading that right, as in, if I need a new drum I'm going to have to buy a whole new friggin' wheel?

 

Yup, sorry bout that. We all share in that with you amiga.

 

Okay, cool. Any recommendations as to what kind of place to look for to see if the drum can be resurfaced? Would it have to be a cycle-specific shop, or would a place that does a lot of car work be able to pull it off, as long as everything is within tolerances?

 

Good question, never had to approach this issue. Anyone care to enlighten us? I'd would think you would have to take it to a machine shop as the auto guy and the bike shop most likely will not have the equipment necessary to perform this process (rear disks are the predominate brake method now thank heavens).

 

Cursed Progress, why must you vex me so?

 

A lot of car shops do have the machinery to resurface drum brakes but I'm not so sure our whole wheel setup would fit on the machine.
Your best bet would be an old fashioned service station with the shop in the back where they actually work on stuff between filling up peoples tanks and washing their windshields.
OK, for those of you just finishing wiping the tears of laughter out of your eyes, out here in the sticks we still have a few of those, but only a few.

 

I would aruge that on a bike the rear does more than 20% of your braking. even when using both brakes. If your front did 80% we'd all be locking up the fronts and be in trouble. I mainly use the rear brake I guess that comes from my upbringing riding dirtbikes as on sand dirt, mud you absolutely don't grab on the front brakes hard if at all. Funny about the msf and the drving test I had only had the bike two weeks and didn't adjust up the rear brakes in the panic stop I locked the front up tight cause the rear barely grabbed. I stopped in time and at an acceptable distance. I even slid straight and the bike didn't even think about tipping. Yeah then I fixed the brakes hehe..

 

not really
think about what really moves in there, the cam opens , the pivot just pivots
the shoes move more at the cam end when the shoes are new a very small area might be all that's touching the drum, as the shoes wear in more and more touch and the brakes work better
when you take them off again you'll see how little contact there is, it will be right by the cam, help them get seated with some emery cloth on a flat board on the area that's touching
just a LITTLE BIT then take the emery cloth to the drum and have at it
80 grit emery should do it

 

Not everyone picked up on the fact that these are brand new brake shoes with effectively 0 miles on them.

Polock hit it, but it's even easier than that.

Your new rear brake isn't going to be at optimum for probably about 500 miles. It's going to be a LOT better after 200 then 300 etc., as the shoes break in to the drum. As long as you "broke the glaze" in the drum before installing the new shoes, it should be fine. I used a medium-grade emory cloth followed by Scotchbrite myself. As long as the drum itself isn't in horrible shape getting it machined shouldn't be necessary.

I just did new brakes on my '81 and the rear took about 300 or 400 miles of gentle use before it bedded in; I could lock the rear anytime I want to now and I'll bet if I pulled it apart the shoes are still not making 100% contact.

You need to break them in; no hard stops from 50 or 60mph, do those in stages, releasing and then reapplying the brake during the stop. You don't want to overheat and glaze your new shoes. Treat them gently for the first few hundred miles, adjust as necessary and then see where you are.

A note about motorcycle braking forces and rear brakes in general: Robert is correct in that the trend has been to rear discs over the past few years but I think that's a matter of weight more than anything else.
Under hard braking, the front really is doing at least 80% of the work if not more. The rear brake is really only a "guidance device" to keep the rear end from passing you when you have it stood on its nose.

The 550 Seca was a "sport bike" and as such was fitted with a smaller rear brake than the 550 Maxim "cruiser." They're both fine based on the stock tire size.

The bottom line is you need to break them in first, a process which can be hastened using Polock's method. I'm lazy.

 

Having turned drums at the parts store I worked at years ago, there is no way the rear wheel from an XJ would fit...

Before you replace the wheel, use the emory cloth as suggested, then make sure you have all the play out of the adjustment. The procedure is in the Clymer's manual and is pretty easy. I did the same thing - after replacing the rear shoes I had 2 - 3 + inches of travel. After adjusting, I'm down to less than 1" travel.

 

Okay, so no jumping the gun yet. Fitz, thanks for the explanation - I think I remember reading that when I first started riding (about breaking in drum brakes), but the shoes were already broken in when I bought the bike, so I must have filed the info away in the catacombs. I'll give it 3, 4 tanks of gas with gentle stops before I worry too much.

dmschuler - yeah, I learned the travel lesson my first ride out after putting everything back together. I think the arm's about as far in as I can get without dragging the shoes, now - haven't measured it, but I figure I'm at about 1-1.5". Although from what you say, I might be able to get a few more turns on the bolt. We'll see.

True story - I had NO IDEA how to read the brake wear indicator on the brake cover until I took it apart, put the new shoes in, and saw how it worked. Talk about ridiculously simple...

 

I'm not sure I'd agree. FWIW, I used to service and sell accessories for brake lathes.

Here's an Ammco A4000 as set up to turn drums: http://www.2ndlifetools.com/images/2ndl ... er%20b.jpg

You'll notice that the arbor overhangs the edge of the cabinet, allowing pretty large work items to be mounted. The only thing potentially blocking is the chip tray, which could be moved.

The other two main considerations are the arbor diameter and the crossfeed. The standard Ammco arbor is 1", but there's an 11/16" reduced arbor for old VW drums. As far as I can tell, the XJ axle is 22mm, which is larger than 11/16". For the crossfeed, I'm not 100% sure it would dial in far enough to reach into such a small drum, but if it doesn't, I'm pretty sure that something could be set up with, for instance, one of the 120 degree rotor tool holders, that would allow access.

My .02 anyway.

Paul