mr928 Posted January 23, 2012 Report Share Posted January 23, 2012 So my 70 521 has stock brakes and they seem to be working ok but the thing doesn't stop for s... I've done a few repeated hard stops and checked the temps at all 4 corners and they all seem to have about the same amout of heat so I guess they are all working. I've pulled the drums off and there is plenty of shoe material and no apparent leaks infact it looks like someone rebuilt them all recently but it is nearly impossible to get them to lock up on dry pavement. I really wanted to leave the truck as stock as possible so converting to discs is not an option at the moment. The flex lines all look good but just to be safe I did order all new lines. Is there a shoe material or manufacture that is preferred? Quote Link to comment
ggzilla Posted January 23, 2012 Report Share Posted January 23, 2012 Before you replace them, adjust them to specification. You'll be amazed how good they work then. 1 Quote Link to comment
paradoxx Posted January 23, 2012 Report Share Posted January 23, 2012 does the drums have the same adjustment (freaking easy) style like the 510?? Quote Link to comment
mr928 Posted January 23, 2012 Author Report Share Posted January 23, 2012 Before you replace them, adjust them to specification. You'll be amazed how good they work then. If they are all working equally why adjust? With the truck in the air I had someone start to apply pedal pressure and they all started to drag about the same time. Quote Link to comment
KC Phirus Posted January 23, 2012 Report Share Posted January 23, 2012 Id it's anything like a 620.. Jack the truck up. Pull a wheel off (if you want)Find cog adjuster on the back of drum. Possibly maybe possibly possible behind a rubber cap. Use a wide screwdriver, or brake tool (my brake tool is too big) and spin the cog down (?) to adjust the brake shoes outwards (towards the drums) Grab the hub and turn it. You should get have friction but be able to turn it by hand. Repeat for the other 3 wheels. Quote Link to comment
paradoxx Posted January 23, 2012 Report Share Posted January 23, 2012 If they are all working equally why adjust? With the truck in the air I had someone start to apply pedal pressure and they all started to drag about the same time. they can be working equally, but the run of the brake pedal will be longer, when you adjust them, you lower the pedal run, making them to brake stronger and faster. Quote Link to comment
DanielC Posted January 23, 2012 Report Share Posted January 23, 2012 If you do not keep the shoes adjusted, they wear unevenly, and then wear out in one spot, and still have lots of good lining in other spots. Drum brakes are also self energizing. The forward motion helps apply the shoes tighter to the drum, and that actually helps reduce pedal pressure. But the whole shoe has to contact the drum for this to happen. Quote Link to comment
datzenmike Posted January 24, 2012 Report Share Posted January 24, 2012 Drum brakes are also self energizing. The forward motion helps apply the shoes tighter to the drum, and that actually helps reduce pedal pressure. But the whole shoe has to contact the drum for this to happen. Leading and trailing shoes? If on backwards they will grip better only backing up?. Quote Link to comment
jon521 Posted January 24, 2012 Report Share Posted January 24, 2012 Leading and trailing shoes? If on backwards they will grip better only backing up?. do 521s have leading trailing? when i replaced my rear shoes, they were the same. Quote Link to comment
datzenmike Posted January 24, 2012 Report Share Posted January 24, 2012 This was discussed the other day. Someone did their kingpins and put them back on the wrong sides. The shoes were put on correctly but because of wheel cylinder placement the leading and trailing shoes would have been reversed. They noticed that it would 'stop on a dime backing up'. Quote Link to comment
ggzilla Posted January 24, 2012 Report Share Posted January 24, 2012 Best brake shoe manufacture Order perfromance oriented shoes from brake shop, such as "Ott's Friction Supply" in Portland, Oregon. The big national performance brake companies don't supply small fry like Datsun 521. Quote Link to comment
mr928 Posted January 24, 2012 Author Report Share Posted January 24, 2012 Thanks for all the suggestions. I will pull off the drums again and inspect them then readjust them after checking how they were assmbeled. Quote Link to comment
skyblue Posted January 27, 2012 Report Share Posted January 27, 2012 the haynes manual i have says to turn the adjuster until the wheels will not turn. In other words the shoes are all the way out on the drum. then back off the adjuster 12 clicks. i did just this and my brakes stop pretty damn good. and that's with some raybestos economy shoes i slapped on. needless to say they are not the best but stop really well when properly adjusted. I can only imagine the improvement with better quality shoes. You may have to fiddle with it for a while to make sure they are evenly adjusted and don't pull to one side. but it's a good start. Quote Link to comment
ggzilla Posted January 27, 2012 Report Share Posted January 27, 2012 Yes, I'm not sure whey "evenly adjusted" doesn't work as well as "fully adjusted" (the way the manual outlines). But it makes a huge difference. Quote Link to comment
DanielC Posted January 27, 2012 Report Share Posted January 27, 2012 In a perfect world, the outside diameter of the brake shoes exactly matches the inside diameter of the drum. When it does, the brake shoe can sit very close to the drum, and still not touch it, and a very small movement of the brake shoe will push the whole contact area of the shoe against the drum. Even if you start out like this, the shoes tend to wear in one spot a little more, because the wheel cylinder pushes the top of the shoe. As the shoe continues to wear, the whole shoe no longer makes full contact with the drum. The pedal gets soft, the brakes do not self apply as much, and this requires more pedal pressure to stop, and the shoes wear even faster. Because drum brakes are self energizing, that is the forward rotation of the brake drum tends to force the brake shoe into contact with the drum, fully adjusted may apply one set of brakes more than the other. Due to slight differences in the brakes, you may need to back off from fully adjusted to evenly adjusted. This is more important on the front, if one side brakes harder that the other, the truck will pull that way when the brakes are applied. A lot of cars have disk brakes on the front, or both axles. Even most cars with drum brakes on the rear have a self adjusting mechanism in the rear brakes. A Datsun 521 does not have self adjusting brakes. This is why you need to adjust them often. the factory recommends adjusting the brakes every 3,000 miles. I would also suggest you adjust then more often after a brake job. Quote Link to comment
mr928 Posted January 27, 2012 Author Report Share Posted January 27, 2012 Well I had all the drums turned and I installed new Centric shoes and what a difference. I still need to work on the adjustment as I'm getting rear lock up but it is a huge improvement. I am missing the locking plate and retaing clip on one adjuster so I'll have to source that. Quote Link to comment
DanielC Posted January 27, 2012 Report Share Posted January 27, 2012 It you are talking about the sliding brake shoe mount on the bottom of the brake plate, I think all four are the same. The mount. The barrel inside it, is different from right to left. left hand threads, left side, right hand threads, right side. There is also a possibility the parts from a 620 truck may also work. But I am not sure. The barrel might have a slightly different diameter, requiring the sleeve that fits on the brake plate, or not. I am making a guess you have to keep the two threaded parts of the barrel and the adjuster that screw into it. The body bolts on a 521 are are American thread sizes, I believe the body bolts in a 620 are metric. I believe you can even swap a 620 wheel cylinder in to a 521. On the rear, for example, the wheel cylinder is the same physical size, but the nuts that hold a 521 rear wheel cylinder are 5/16-24, and the brake line flare nut is 3/8-24. On a 620 truck, the same part has M8-1.25 nuts, and the flare nut is M10-1.0 With turned drums it is important that you adjust the brakes a little more often at first. the drum is a larger diameter, and the shoes need to wear into the larger diameter, before they fit really good. Quote Link to comment
Siempreloco Posted January 27, 2012 Report Share Posted January 27, 2012 Well I had all the drums turned and I installed new Centric shoes and what a difference. I still need to work on the adjustment as I'm getting rear lock up but it is a huge improvement. I am missing the locking plate and retaing clip on one adjuster so I'll have to source that. I was going to highly suggested getting them turned, but you got it Quote Link to comment
ggzilla Posted January 27, 2012 Report Share Posted January 27, 2012 And Centric is not even one of the best brake shoe manufacturers... just goes to prove that Drum Brakes are alright. Quote Link to comment
mr928 Posted January 27, 2012 Author Report Share Posted January 27, 2012 This is the clip that is missing. This is also from the wheel that locks up first which might be because the adjuster can slide forward without resistance. Quote Link to comment
KC Phirus Posted January 27, 2012 Report Share Posted January 27, 2012 This is the clip that is missing. This is also from the wheel that locks up first which might be because the adjuster can slide forward without resistance. Yep yep yep. Rockauto.com Nissan whatever with drum brakes Brakes Misc hardware Clip 3.42$ Quote Link to comment
ggzilla Posted January 28, 2012 Report Share Posted January 28, 2012 Looks like more than just a clip is missing. There are two clips, and keeper and a rubber seal. Quote Link to comment
KC Phirus Posted January 28, 2012 Report Share Posted January 28, 2012 Looks like more than just a clip is missing. There are two clips, and keeper and a rubber seal. Yeah lets be all fancy and include the rubber cover Quote Link to comment
ggzilla Posted January 28, 2012 Report Share Posted January 28, 2012 Well without the seal it gets dirty and stops sliding. It's more than just looks. 1 Quote Link to comment
mr928 Posted January 28, 2012 Author Report Share Posted January 28, 2012 1327706606[/url]' post='621221']Yep yep yep. Rockauto.com Nissan whatever with drum brakes Brakes Misc hardware Clip 3.42$ Thanks for the lead. I will order shortly for all 4 wheels and hopefully they will have the rubber as well as all mine are missing. I'm sure that has something to do with the 2 frozen adjusters . Quote Link to comment
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