CT70 brake question

Lucan

Member
I noticed that no matter how much I adjust the brakes on My 70 KO, I cannot get the brakes to brake quicker than a gradual stop. I dont expect stop on a dime performance, but is this normal for the stock brakes?
 

HondaCTer

New Member
It is not normal. Check your pads for wear and your drums. I have seen in one case, where I wasn't paying attention, assembled the front brake set and place the brake arm too far back. When braking the lever would only pull back half way and stop. I found out the brake arm was jamming against the brake cover. Made a quick adjustment and had enough braking power to do an endo.
 

OLD CT

Well-Known Member
Also, we need more info! Are the shoes 40+ years old? Have you inspected the drum linings for pitting/rust?
 

69ST

Well-Known Member
The short answer...Pull the drums, clean them, along with the brake plates, removing all traces of dirt, brake dust, oil & grease. Measure the ID, if it's close to, or beyond 111mm...or/and you find major rust pitting, it's time to replace the drums. They probably won't be beyond 109-110mm. Source new shoes, front & rear, preferably with grooved friction material; that helps to keep brake dust from accumulating between the friction surfaces.

For tech discussion purposes, let's assume that you have them properly adjusted, are getting full lever force to the brake cams, and the plate assemblies are not binding in any way.

That leaves two issues: shoe contact and contamination. The former is easy enough to figure out; clean & scuff the friction material, make a couple of test stops, then see how much of the surface is developing a normal, glazed, appearance. It should be 100%. This is more of an issue with the combination of new shoes and worn drums. The greater the ID, the bigger the drum arc...and the farther the new shoes have to wear-down toward their centers to get full contact. That's why there's a max ID spec (111mm).

Contamination is sometimes not obvious, especially with 1970s-vintage, original, brake shoes...as OLD CT mentioned. That said, grease/oil can penetrate the friction linings and it doesn't take much to kill braking power. I've seen original brake shoes that still worked as well as they ever did...and others that looked like new but were totally worthless, even after cleaning & scuffing. FYI, Brakleen is only effective if used before petroleum has gotten more than surface-deep. Otherwise, it'll be a short-term/semi-effective fix. The residual oil will be drawn to the surface by capillary action. Normal braking heat will speed that process.

Rust is also a surface contaminant that reduces friction. Best way to remove rust, from drum surfaces, is low-pressure bead blasting. It's thorough and removes less solid metal than any other mechanical process. Unless it's substantial (and it rarely is) the impact of pitting on stopping power is minimal. Scoring, OTOH, doesn't have anywhere near the impact that intuition says it should have. As long as drum ID isn't near, or beyond, the limit, the main effect of scoring is increased break-in mileage for new shoes. I wouldn't want scored drums but, scoring alone doesn't necessarily mean that they're suitable only for paperweights, model boat anchors or recycling.

The final judge of success is actual braking performance. It's a foolproof way of compensating for lack of technical/mechanical expertise. Braking power, into the low 50mph range, will be pretty decent...if everything is working & adjusted as it should be. You should be able to lock the rear wheel, though I'd only ever try that as a test and at very low speed...it's brutal on the machinery. Up-front, forget trying to pull a stoppie. It's a lot safer, not to mention easier, to test front brake power at a dead stop. Grab a handful of front brake lever and attempt to push the bike forward. With optimal brake action, the front wheel should remain locked, or at least damned close to it. FYI, break-in, typically called "bedding-in" of brake shoes/pads is part of the adjustment process. Even new drums & shoes won't perform optimally until this has been done. So take this into account, if anything has been replaced, it can make a BIG difference.
 

Lucan

Member
OK, more info. I just replaced the rear shoes. I scuffed the drum, and there is no contamination. I definitely cannot lock the rear brake, and I don't want to adjust it so that it binds before braking. I moved the brake lever so that I can adjust it more than before. I haven't replaced the front shoes, that's next. Ive always heard that the brakes aren't the best on these bikes. I feel that it stops ok, but this bike has a Lifan motor and more power and speed than the stock motor. I don't know if I could stop that fast from 35-40 mph if for instance I had to make a panic stop.
 

Enginedoctor

Well-Known Member
The brakes on these bikes (drum/drum) and a small diameter to boot, arent the best, but ive driven full size dirt bikes with disk front drum rear, and they were able to lock up a 17" rear wheel witout a huge amount of effort. The brakes should be adequate, at the very least. The info racerx gave you above involves both objective measurements (calipers used on the ID of the drum) and trial & observation (scuffing the shoes and looking for a contact patch) diagnosis. Until you attempt these things, you really are just providing subjective information, which doesnt help anyone. I would suggest listening to what he wrote and seeing what hits what where (on the shoes) and seeing if the drum/hub OD is out of spec. Eliminating obvious problems firls will probably speed your diagosis.
 

69ST

Well-Known Member
I ran the stock drums with 60mph+ power until 2005. The stopping power was quite acceptable up about 50mph. Above that speed, I used compression braking to decelerate down to ~50mph before dropping anchor for real. It was possible to execute a panic stop from 60mph, if a little more dramatic than I'd care for...ask me how I know.:whistle: That's about 3x the braking force, compared with the same maneuver at your stated 35-40mph. Get the picture? If your brakes are properly setup, within spec, and bedded-in you should be getting way better stopping power than you're indicating. I can only point you in the right direction...it's up to you to use the info and figure out what needs to be changed.

FYI, eventually I went to a 220mm disc brake on the front. Going from 60-to-0 in ~6 seconds is now easy. I'm still running a stock-type drum brake on the rear. IOW, the stock drums are better than you seem to think...if everything is working properly.
 

OLD CT

Well-Known Member
Moving the brake arm on the brake plate from the factory position is never a good idea. That may be why you can't lock the rear wheel, which you should be able to do easy enough.
I suggest putting it back in the position it was. There is a really small dot on the arm and it needs to line up in the non splined section.
 
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kirrbby

Well-Known Member
I have a bike that the brakes felt really "spongey". Like yours it had new shoes and cleaned and blasted brake drum. The drum measured around 110mm. I never verified by checking how the shoes were wearing, but I figured they just needed to wear in. So I would use them in such a way as to speed the wear in...sometimes I would just touch the brake as I cruised down the road, trying to burn off some friction material. At some point I just kinda forgot about it. I assume that was about the same time they WERE worn in. I'd say, get them working as best as you can. Then try to get em broke in while being over cautious about not needing a panic stop.
 
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