Drum Brakes Grabbing - SOLVED!

[Easternair]

If you have drum brakes and have serviced the brakes and replaced many parts including the brake shoes and now your drum brakes drag and lock up when turning in forward direction but release when turning in the opposite direction the problem are your brand new brake shoes! The primary shoe has the shorter brake lining material and many new brake shoes are coming with that front lining not centered but much lower on the brake shoe (see pic). Many reputable companies are putting out these brake shoes probably because they are all being imported from the same factory in China. And therefore have the front lining off center. After reading many forums at 'b-bodiesonly' and having many well intentioned participants giving out the same wrong information and changing many parts including wheel cylinders..master cylinder..even the power brake booster and trying out multiple return spring combinations thinking that they weren't strong enough to pull the shoes back, the problem would not go away. The brakes continued to self generate when rotated in the forward direction and lock up but functioned normally in the reverse direction. The solution is to look at the photos closely and replace your brake shoes with ones that have the lining material in the center. (see 2nd and 3rd pics). The problem is that the top edge of the off centered lining is getting caught on the brake drum when the brakes are applied and causing the shoes to self generate which is clearly visible by watching the star adjuster move aft as the drum catches the leading edge of the front shoe and starts to self generate causing the wheel to lock up. Change the brake shoes with ones that the linings are centered and your problem is solved.

 

[AR67GTX]

Would aggressively chamfering the edge of the linings help any?

 

[peabodyracin]

That's a great tip. Thank you!

 

[pnora]

Most of the ones I see the problem is in the adjustment. The shoes need to anchor and if the parking brake is partially on due to stuck cables or adjustment they will not anchor. The correct procedure is parking brake backed off, shoes centered and anchored then the service brake is adjusted. After that the parking brake can be adjusted. I have seen the different linings for ever and have never considered that to be a problem. Axle lube leaks and oversize drums would also be an issue.

 

[R/T Boy 67]

Good info. You saved plenty of hair pulling for a lot of people.

 

[Easternair]

Would aggressively chamfering the edge of the linings help any?

It might.

 

[#41]

I had out-of round brand new chinisium drums cause grabbing also. It took me a while to figure out. Once turned on a lathe everything was ok.

I never thought I'd have to add "check new parts for flaws" to my diagnostics list, but it's now its the first thing on the list.

 

[kiwigtx]

Thanks for the great information, and for sharing it @Easternair ...this thread is now a Sticky for all to benefit from.

 

[theman440]

. . .or just convert to discs.

 

[69 Q5 Bee]

I've had a related issue with drum brakes locking up on me with only the slightest touch of the brake pedal. Chamfering the width edge of the shoes corrected the problem for me. The edge of the shoe material was contacting the drum first causing the issue.

 

[Ceedawg]

I’ll look at some of my old shoes (1970s) I’m almost sure they are all made that way. Maybe the problem is the new ones are just made too short on the top edge. Old ones are both equal on bottom not raised like in your pic, I’m thinking the lining should be up to that notch

 

[Mayfair]

I spent nearly 3 weeks finding my similar problem. The lining on the new shoes was also too far around the shoes but also the rub blocks were in the wrong place and smaller. The shoes were rolling over backing plate edge and hanging up there. I also changed springs and cylinder without success and only when comparing original shoes to replacement parts found the defects. Improper shoes were Spectra and found right shoes at Canadian Tire. Will post photos when I find them(lost in my computer).

 

[Daniel J 11704]

As a side note, when converting to disc brakes, you must remove the residual check valve in the master cylinder. Most are located under the brass seat in the outlet port. A small tap to thread internally and pull it out to remove it

 

[wthalin]

Where did you buy the good ones? My drum locks up on me but probably more due to what pnora is talking about since it is only the driver side rear.

 

[Mayfair]

I purchased what appears to be the last Wagner OE Spec CR169 from a Canadian Tire store. They no longer show them available. My grabbing brake was only on the front right, it got worse with each brake application but went away when backing up. It created a lot of heat as it was dragging but did not seem to cause pull to the right except when brakes applied. The location of the lining on the primary shoe along with the small rub pad on the shoe and 60 years of wear on the backing plate probably all contributed to the drastic wheel lock. The first set of shoes I installed were from Wrench Monkey, Canadian version of Rock Auto, they were Raybestos 169PG. They were separating and cracking at the rivets and were changed by a brake shop who were doing safety inspection for gov't so I could register the car,held prisoner till safe to drive. They then put in the Perfect Stop and did mention car pulled slightly but would not hinder driving, it did work well enough to drive out of shop and hand over to me. Called this shop to report what was happening and basically told so what. Buying auto parts on line is hazardous as you can't compare and displayed item is usually generic, I now try to source from local distributors and take old part with me. I try to avoid anything made in China but hard to do.

 

[Ceedawg]

From what you said I’m Glad I don’t live in Canada

 

[Easternair]

Where did you buy the good ones? My drum locks up on me but probably more due to what pnora is talking about since it is only the driver side rear.

I finally went all in and got the Matrix Ceramic brake shoes from Musclecarbrakes.com. They are quieter than semi-metalic...do not prematurely wear the drums out...outlast the regular oem shoes, do not heat up as fast, have way better fade resistance, twice the stopping power and finally they put out a white dust which is less noticeable and objectionable than the black brake dust from normal brake shoes so your wheels stay cleaner. The down side is their price. Way over priced at $129.95 per set (4 shoes each) for both front or rear drums. Many magazines have written positive articles on these brakes. Many have run comparisons with the oem shoes and they do meet the mfg's claims that they stop as good as disc brakes. But at almost $160 with shipping its a pretty steep price for brake shoes. I wrote the company telling them that I had been waiting on purchasing their ceramic brakes for over 4 years because of the price...which in that same time period I could have purchased two maybe three sets if the price had been more reasonable. Hopefully they can run the numbers and see the error of pricing themselves out of what most car enthusiasts of normal means can afford or are willing to pay for brake shoes. BTW they have other drum brake performance parts such as higher volume brake wheel cylinders and high performance drums to bring your old drum brakes into modern standards as far as stopping distances. They sell complete kits or individual parts as needed. On another note...you don't have to spend that much to get your drum brakes to work properly...my rear shoes cost me all of about $29 bucks and they work flawlessly...just make sure whatever brake shoes you eventually go with that the primary or forward shoe brake lining is centered and not positioned to low to the bottom. Hope that helps.

 

[toddrod69]

I am having similar problems on the front of my 68 GTX. Car came with 4 corners non-self adjusting breaks. I converted the rear to self adjusting. Issue is that the driver side(left) front locks up when I press the breaks. It has new break lines and wheel cylinders. Pads where replace recently. I noticed the the left front has a shorter front pad than the other one. Right side has equal lenght pads. I adjusted the drives side in as much as I can and the passenger side out as much as I can. Please help. Been trying to resolve this issue all month. Thanks Todd

 

[toddrod69]

I am having similar problems on the front of my 68 GTX. Car came with 4 corners non-self adjusting breaks. I converted the rear to self adjusting. Issue is that the driver side(left) front locks up when I press the breaks. It has new break lines and wheel cylinders. Pads where replace recently. I noticed the the left front has a shorter front pad than the other one. Right side has equal lenght pads. I adjusted the drives side in as much as I can and the passenger side out as much as I can. Please help. Been trying to resolve this issue all month. Thanks Todd

 

[toddrod69]

Having trouble getting the pitures to post but I'm working on it.