Topic: CB550: uneven braking

[Franky]

When I use the rear brake, the braking action is not smooth and constant. Instead it alternates in a wobbly kind of way: hard braking, less-hard breaking, hard breaking, etc. the sensation increases the harder I brake. I had a look at the pads and they seem evenly worn.

any ideas?

[flybox1]

That pulsating sensation would lead me first to cleaning the brake drum or rotor surface.
rub it down with fine emery paper, then clean it really well with spray brake parts cleaner and/or compressed air. 
wear some sort of mask as ingesting the brake dust isn't a good thing.
cross contamination of the brake pads is possible. 
if you reuse contaminated pads, the problem might reappear.

[calj737]

Also, do a comprehensive check on your wheel bearings. The braking pressure could easily be causing the wheel to wobble that is otherwise not noticed. Is your wheel also aligned properly left-to-right? Do also check your swing arm bushings and be sure your shocks are fully tightened.

If you've checked your pads and the brake surface, then the problem lies somewhere else as described above.

[LesterPiglet]

Liner is susceptible to cracking on 550's. Check it carefully.

[dave500]

gday franky,the brake hub may be out of round,does the pedal pulse up and down a little bit at the same time?

[Franky]

I'll take apart the (drum) brake and follow your suggestions. I have a new set of bearings I need to fit, so that will rule out the possiblility that they are at fault.

Hi Dave: No, the pedal doesn't seem to move.

[calj737]

Since you'll be pulling the wheel, that will provide you an excellent opportunity during re-assembly to make certain all the alignment and fasteners are properly tightened. Do also check your swing arm bushings while the rear is apart.

A last bit: if you have the means, check the rear wheel for "true". Pop the axle onto a make-shift stand, slide wheel over the axle and measure for runout. Who knows, wouldn't hurt to cross that off the list when it's so easy to verify.

[Franky]

Thanks calj737. I actually have a set of new spokes too. I have recently build a new front wheel (http://forums.sohc4.net/index.php?topic=118983.0;all) , so maybe I should go all the way and get that done too... Just a few too many projects these days :-)

[strynboen]

mine hub vas cracket total..aluminium korodes inside and press the cast irom ring to break

there are 2 types of hubs. for the 1978 k3.....(.f type and k type.).i got a vront type home from germany

i have a reserve plan..to drill the brakecast matrial aut...and chrimp a cast iron drum in and turn it aut to spec....and safe it aganst turning vith some brass bolts through the matrial..think a drum brake from a littel car trailer can delevre the parts

[LesterPiglet]

A popular substitute in the UK was a drum from a Morris Minor.

[strynboen]

ha.... a bit hard to find in today"s denmark... ..but like to hear the idea has be done before...my other idea vas to make a hub instrt to konverse to disc mounting..but to find a small disc/kaliber mounting..(this 750 sets are massive)..but spoken hveel small disc make the  parts marked small

[LesterPiglet]

  http://www.morrisminorspares.net/shop_item.php?ID=1525
That's a 7", there is 8" as well. I'm not sure what you need.

[MoMo]

also, check the chain for tight and loose areas-that could cause hop when rear brakes are applied...Larry

[calj737]

Another good idea!

[seanbarney41]

How much have you ridden the bike?  I have had similar symptoms with bikes that have sat for a very long time.  It eventually smoothed out on it's own through use.  ...not the safest way to do it.