Scored CG brake drums

[mudcow007]

Morning all

just in the middle of rebuilding a '84 CG125

just took a look inside the rear drum an its pretty scored - it looks like a stone or something has got inside an tore the shoes to shreds

i'm guessing you cant do much with it so its a new wheel??



ta

[ricklincs45]

Depends whether or not the scoring has gone past 'tolerance' point. If it's light, the drum can be machined true again, if not, there are engineering companies that can re-line the drum.

Probably cheaper to buy a replacement 2nd hand wheel.
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Author '80 Bikes, and counting...' Currently getting frustrated with an MZ 125 TS.

[mudcow007]

Ahh

this cheap rebuild is starting to mount up!!!!

cheers

[YBR Ric]

A method I've used successfully in the past is to attach some wet/dry to the brakes with double sided carpet tape, adjust the brake shoes until its rubbing against the drum then spin the wheel to smooth the contact surface. Once the rubbing stops, dismantle, check, and repeat as necessary using finer graded paper. Do not exceed the drum lining wear limits.

This is best done by hand and not by using the engine to drive the wheel because if the double sided gets too warm the wet/dry will slide and jam, possibly resulting in unwanted damage.

When happy with the result, thoroughly clean the drum, fit new brake shoes and just remember to bed them in carefully.

[mudcow007]

Cheers Ric

i will give it ago, im guessing the tolerance ratings will be stamped into the hub somewhere?

its pretty manky in there so i will clean em up first

just priced a spanking new wheel from Davidsilvers an its coming out at over 200 notes unbuilt

[Vincent]

It's not the actual scoring that makes the drum unfit for use, more the raised parts. As above, if you can get rid of them, you can still use the drum.
Some previous owner had probably let the pads get too low and the rivets have eaten into the drum.
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Space Is Deep

[YBR Ric]

The limit could be somewhere on the hub, otherwise it's in the workshop manual.

For the YBR, it's listed as 130mm new with a service limit of 131mm, ie half a millimeter of lining insert wear.

[ricklincs45]

Just had a look in a Haynes manual for the CG; it says the drum inside diameter is 110mm standard, with a wear limit of 111mm.

If the hub is still within wear tolerance, still might be worth letting a machine shop check it for trueness - over the years they tend to go slightly oval, though if that has happened, machining it back to 'round' may take it pass the wear limit. Other option (if still usable) is as YBRric mentioned, to rub any high points out by hand.

That's the prob' with old bikes, one job leads to several others!

Rick
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Author '80 Bikes, and counting...' Currently getting frustrated with an MZ 125 TS.

[mudcow007]

cheers all

i think the rear is toast so looks like i will have to trya n find a wheel

i haven't looked at the front, but im guessing if the back is bad - the front will be worse

anyone know if all CG's used the same wheel size?

[unitynotsocri...]

its a cg drum brake,flatten off the rough bits and just pull the shoes out every 3,000 mile and file em flatter.As long as there's no really deep bits.
In my extensive experience of honda cg/cb drum brakes..........their performance is more affected by cable stretch than pad contact.
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nearly a normal tax paying tosser.......with ferrileness suzi100,cg125,cb125scb100n,cb175,cd100,cj250t,kh250,c15,125 bantam,super 6,rickman gs750,xt500,250rs,dt175,lifan125,dolomite1850,metro,Morris220ld,morrisfg,leyland princess,range rover,corsa,vw camper .now struggling with legs. MORE ORDER = MORE CHAOS

[mudcow007]

im just worried that if i ride on a scored hub there is a possibility of the brake binding an locking on at some point?

is that a possibility?

cheers

[Walloper]

[ricklincs45]

Have had/run loads of these little Honda's and have never had a problem with back brakes. Scoring by itself is unlikely to cause a brake to lock on - you'd have to have some serious faults such as a drum or shoes breaking up for that to happen.

As the back brake is rod operated, no issue with cable stretch. Have seen bikes running without problem even when the shoes are worn and the brake plate actuating arm has been turned round one notch.

Would certainly be worth giving it a thorough clean and examining for cracks in the drum while it's off, just to be safe.

The rear brakes are usually very good; if you can use the current hub I'd be tempted to 'make do' if safe to do so and spend the money saved sorting out the front - they're usually in need of new cable/shoes and probably a skim (a CB100N disc brake is far, far better if you're not bothered about originality...).

Rick
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Author '80 Bikes, and counting...' Currently getting frustrated with an MZ 125 TS.