 rear brake adjustment |
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| Medtner3 |
 Oct 3 2021, 10:24 AM
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#1
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Member  Group: Members Posts: 180 Joined: 7-July 20 From: Cedar Park Member No.: 24,467 Region Association: None  |
Should the rear brakes have a slight rub when you turn each rear wheel ? I believe I correctly adjusted with a feeler gauge to .8 mm but I do get a rub when I spin the wheel... that does not seem right with the parking brake off
Thanks in advance for any comments |
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| mepstein |
Oct 3 2021, 10:30 AM
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#2
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914-6 GT in waiting Group: Members Posts: 19,260 Joined: 19-September 09 From: Landenberg, PA/Wilmington, DE Member No.: 10,825 Region Association: MidAtlantic Region 
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After you adjust, go for a quick drive and then check the wheel rub. The pistons need to cycle though a couple times after you adjust them.
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| Medtner3 |
Oct 3 2021, 02:11 PM
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#3
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Member Group: Members Posts: 180 Joined: 7-July 20 From: Cedar Park Member No.: 24,467 Region Association: None |
QUOTE(mepstein @ Oct 3 2021, 11:30 AM)  After you adjust, go for a quick drive and then check the wheel rub. The pistons need to cycle though a couple times after you adjust them. I have already put 30-40 miles on it since the brake job Are the rear wheels supposed to have a slight rub? |
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| mepstein |
Oct 3 2021, 02:19 PM
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#4
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914-6 GT in waiting Group: Members Posts: 19,260 Joined: 19-September 09 From: Landenberg, PA/Wilmington, DE Member No.: 10,825 Region Association: MidAtlantic Region
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QUOTE(Medtner3 @ Oct 3 2021, 04:11 PM) QUOTE(mepstein @ Oct 3 2021, 11:30 AM) After you adjust, go for a quick drive and then check the wheel rub. The pistons need to cycle though a couple times after you adjust them. I have already put 30-40 miles on it since the brake job Are the rear wheels supposed to have a slight rub? No. |
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| davep |
Oct 3 2021, 05:29 PM
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#5
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914 Historian Group: Benefactors Posts: 5,139 Joined: 13-October 03 From: Burford, ON, N0E 1A0 Member No.: 1,244 Region Association: Canada  |
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| Medtner3 |
Oct 3 2021, 07:36 PM
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#6
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Member Group: Members Posts: 180 Joined: 7-July 20 From: Cedar Park Member No.: 24,467 Region Association: None |
QUOTE(davep @ Oct 3 2021, 06:29 PM) I will double check mine but I am pretty certain that if I reduce the clearance then I will be rubbing brakes very hard Currently, I spin the wheel and each side rubs briefly then it's free, so perhaps 45 degrees of the 360 degree spin or if it were a clock face then it rubs from 1-3 oçlock I am thinking that maybe the rotors are warped? |
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| mxkinn01 |
Oct 3 2021, 08:30 PM
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#7
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Member Group: Members Posts: 228 Joined: 18-June 17 From: Las Vegas, NV Member No.: 21,195 Region Association: Southwest Region
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Season 1 episode 1 of the 900 series show, they are adjusting rear brakes on a 914. Its at 10:51 in the episode. You can see it on Tubi for free.
BTW on episode 6 at 7:20 there is a real handsome guy talking about his 914 at a local show. |
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| iankarr |
Oct 3 2021, 10:26 PM
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#8
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The wrencher formerly known as Cuddy_K Group: Members Posts: 2,472 Joined: 22-May 15 From: Heber City, UT Member No.: 18,749 Region Association: Intermountain Region
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Go to 17:30 in on this video...
https://youtu.be/oUvYRPe2bDw There's usually a high spot on the rotor. You put the high spot under the brake pads when setting the venting clearance. Yes, the spec is .004, but you don't need to be too precious with a feeler gauge. Just turn the adjuster till the pad contacts the rotor (one side at at a time), then back it off till it juuuuust doesn't touch. if the high spot is too high out of flat, then yes the rotor may need to be replaced. You don't want the brakes rubbing at all, as they'll get hot and/or the flex lines will swell. If you're not comfortable with this, please go to a pro. There's no shame in making sure your brakes are working correctly (IMG:style_emoticons/default/wink.gif) |
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| Medtner3 |
Oct 4 2021, 08:33 AM
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#9
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Member Group: Members Posts: 180 Joined: 7-July 20 From: Cedar Park Member No.: 24,467 Region Association: None |
QUOTE(iankarr @ Oct 3 2021, 11:26 PM) Go to 17:30 in on this video... https://youtu.be/oUvYRPe2bDw There's usually a high spot on the rotor. You put the high spot under the brake pads when setting the venting clearance. Yes, the spec is .004, but you don't need to be too precious with a feeler gauge. Just turn the adjuster till the pad contacts the rotor (one side at at a time), then back it off till it juuuuust doesn't touch. if the high spot is too high out of flat, then yes the rotor may need to be replaced. You don't want the brakes rubbing at all, as they'll get hot and/or the flex lines will swell. If you're not comfortable with this, please go to a pro. There's no shame in making sure your brakes are working correctly (IMG:style_emoticons/default/wink.gif) Ian thank you ! Perfect explanation! |
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| davep |
Oct 4 2021, 09:53 AM
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#10
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914 Historian Group: Benefactors Posts: 5,139 Joined: 13-October 03 From: Burford, ON, N0E 1A0 Member No.: 1,244 Region Association: Canada |
Often, when the rotors wobble (also called run-out) there are several factors to consider. If the rotors are old, then warping or uneven wear can be the culprit. Resurfacing the rotors can be done, but turning them on a brake lathe often results in reducing thickness below minimums. Disc-brake grinding was developed by a friend of mine, and Bear Alignment & Brake purchased his design. I remember working in a Honda shop 30 years ago this method was used on new rotors upon installation.
With new and used rotors I have found it best to sand the face and edges of the hub and the inside of the rotor where they mate. ANY surface high spot here will not allow the rotor to spin true. Once cleaned up, spin the rotor on the hub just like lapping a valve. To check the run-out you must have the rotor clamped to the hub just as if the wheel was torqued in place. Mark the high spots. Then index the rotor by one bolt hole, and do it again again and again until all positions have been tried. Figure out the orientation with the minimum run-out. If the run-out is more than the venting clearance, then you might have a problem. |
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| Medtner3 |
Oct 4 2021, 02:51 PM
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#11
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Member Group: Members Posts: 180 Joined: 7-July 20 From: Cedar Park Member No.: 24,467 Region Association: None |
QUOTE(davep @ Oct 4 2021, 10:53 AM) Often, when the rotors wobble (also called run-out) there are several factors to consider. If the rotors are old, then warping or uneven wear can be the culprit. Resurfacing the rotors can be done, but turning them on a brake lathe often results in reducing thickness below minimums. Disc-brake grinding was developed by a friend of mine, and Bear Alignment & Brake purchased his design. I remember working in a Honda shop 30 years ago this method was used on new rotors upon installation. With new and used rotors I have found it best to sand the face and edges of the hub and the inside of the rotor where they mate. ANY surface high spot here will not allow the rotor to spin true. Once cleaned up, spin the rotor on the hub just like lapping a valve. To check the run-out you must have the rotor clamped to the hub just as if the wheel was torqued in place. Mark the high spots. Then index the rotor by one bolt hole, and do it again again and again until all positions have been tried. Figure out the orientation with the minimum run-out. If the run-out is more than the venting clearance, then you might have a problem. Thank you I will go through this process first then adjust the clearance. much appreciated |
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| friethmiller |
Oct 6 2021, 10:04 AM
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#12
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Member Group: Members Posts: 471 Joined: 10-February 19 From: Austin, TX Member No.: 22,863 Region Association: Southwest Region
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Glad I saw this post yesterday. I had just finished my first test drive the day before and forgot that I needed to do this. I went out and adjusted the vent clearance on my rear calipers. No issues with this entirely new brake system. Blown away by the quality work done by PMB on my calipers and proportioning valve.
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| mark04usa |
Oct 6 2021, 07:18 PM
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#13
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'70 1.7 Tangerine Group: Members Posts: 351 Joined: 14-September 09 From: Austin TX Member No.: 10,805 Region Association: Southwest Region
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QUOTE(friethmiller @ Oct 6 2021, 11:04 AM) Glad I saw this post yesterday. I had just finished my first test drive the day before and forgot that I needed to do this. I went out and adjusted the vent clearance on my rear calipers. No issues with this entirely new brake system. Blown away by the quality work done by PMB on my calipers and proportioning valve. Congrats on the first test drive! Glad to hear that there is another 914 on the road here in Austin. (IMG:style_emoticons/default/beerchug.gif) |
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| friethmiller |
Oct 6 2021, 08:59 PM
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#14
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Member Group: Members Posts: 471 Joined: 10-February 19 From: Austin, TX Member No.: 22,863 Region Association: Southwest Region
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QUOTE(mark04usa @ Oct 6 2021, 08:18 PM) QUOTE(friethmiller @ Oct 6 2021, 11:04 AM) Glad I saw this post yesterday. I had just finished my first test drive the day before and forgot that I needed to do this. I went out and adjusted the vent clearance on my rear calipers. No issues with this entirely new brake system. Blown away by the quality work done by PMB on my calipers and proportioning valve. Congrats on the first test drive! Glad to hear that there is another 914 on the road here in Austin. (IMG:style_emoticons/default/beerchug.gif) @mark04usa - Yes!! Hope to see you at a car show in the area then. I just got done driving it around from noon till well after dark. I'm like a little kid again. Had to make sure those piston rings got a chance to set into the cylinders. Feels so good to drive it after a 4 year restoration. Now, if Ford could just build my Bronco, I'd be in second heaven! |
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