Slow_sevens

Chasing a noise.
Right rear wheel.
Thwick thwick thwick once per wheel revolution.
Does it most of the time but not all of the time.
Does it when coasting, accelerating and braking.
Noise gets much louder on right hand turns.
Noise got worse after I pulled and reinstalled drum to check pad thickness.
Pad thickness is good according to manual at 4mm.

Wheel has a spacer and current theory is one of the spacer bolts is slightly too long and touching something behind the drum under unweighted conditions. However did not see any marks inside brake that would match this theory. Going to take it all apart again…. Anyone got any suggestions of what else to look for once I am inside?

1981 FB all original except wheels. Drum brakes on rear.

(Sooooo glad to be finally posting something other than a chronic flooding issue!)

KansasCityREPU

iTrader: (9)

Is your spacer hub centric?

Slow_sevens

New to this world so checking my terminology. Hub centric means the adapter centers on the hub using a bevel on the large hole that slides over the hub boss, and lug centric means the spacer centers on the hub using the bevels on the lug nuts that attach the spacer to the hub?
My recollection is that the spacer attaches to the hub with four chamfered bolts that tighten like regular lug nuts to center the spacer. Then there are four threaded studs sticking out of the spacer over which the wheel slides and attached with four chamfered nuts. My kid did the work with the help of the auto shop he was working at so would need to take it apart to refresh my memory.
Am I going to die?

KansasCityREPU

iTrader: (9)

Here is a good explanation. RX-7's are hub centric. If your wheels are not hub centric, they will need hub centric rings.

https://www.discounttire.com/learn/hub-rings

Slow_sevens

Spent a couple of hours down the rabbit hole Googling around various forums. An awful lot of chatter and nothing definitive. The link provided concludes that hub centric rings would help with centering but are not required structurally… but opinions elsewhere are all over the place.

dwallsknox

Warped brake drum maybe? Could have one spot out of round that's contacting the backing plate or one of the shoes.

Maybe swap the drums side to side and see if the noise travels with it?

Slow_sevens

I do like the idea of switching drums side to side as a way of narrowing down the cause of the noise. I will be working on the Watts link tomorrow and will add the drum swap to the list.

KansasCityREPU

iTrader: (9)

What can happen is that without the rings on a non-hub-centric wheel, it can drop a few mm and cause an imbalance. That imbalance is transferred to the axel and causes it to wear at the bearing.

Slow_sevens

Interesting. Will check the bearing when I have the wheel off tomorrow, see if I have play or can feel/hear anything. Rear does make a constant grumble noise at highway speed but assumed that was because The Kid removed all trunk lining mats when the hatch window leaked and everything got soaked.

Slow_sevens

Fixed! Swapped the drums left to right and it got worse. Thwick thwick thwick from BOTH sides. And louder…. Pedestrians were turning to see what the noise was.

Pulled both wheel spacers and cut the bolts shorter (making sure I left enough for full thread engagement plus a bit extra). Noise has now gone.

Now for the next project…. Rack and pinion steering.

KansasCityREPU

iTrader: (9)

Nice. Glad you found it.

Banzai

iTrader: (13)

So was it the spacer or the length of the bolts? Not sure about FB's, but SA's did have two different lengths of stud bolts. One for the aluminum waffle rims and a shorter version for the basic steel rims. It even extended to the hold down bolt for the spare. Would assume this carried over to the early FB's. If you have an aftermarket rim, maybe those are also thinner in this area and required a shorter bolt?

Slow_sevens

It was the bolts that came with the spacer. Plenty of clearance on the front discs, but too long for the rear drums. Sadly the original wheels are long gone, car came with some pretty nasty five spike ‘90s wheels.

Frogman

Funny I have a very faint ticking ( you can only hear it if you drive next to a wall) just like this that only started after I got the Rewinds. Gonna try your fix.

Slow_sevens

Defn worth checking. Mine has been silent ever since I cut the bolts down. You probably already know this but just in case… thread a nut of the same diameter and pitch on to the bolt before cutting then you can remove the bolt which will clean up the thread and make it easier to start the bolt back in to the hub.

Frogman

I have driven 5'000 miles with this noise . I Suspect something in the drums rubs. I also have a much more anoying wooshing sound from the driver side and a faint scraping sound from the rear. At this point the only real option is a bearing replacement and a complete rear drum swap from a 79 to a 81+ drum set up. These sounds are not really audible past 40 mph. I also have no cabin padding in the rear . Some of you guys have louder trans whine than whatever the hell I have and your trans shift well .
Also great tip. I learned that sheet the hard way a few years ago lol.