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jcpatrickharrison Samba Member
Joined: November 23, 2005 Posts: 294
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Posted: Sat Apr 17, 2021 3:01 pm Post subject: Brake drum measurements |
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Hey,
I’m trying to figure out if I need to buy new brake drums. They look pretty decent. How do I know if they need to be turned? Is there an easy way to tell if they are out of round? I was thinking I could measure the wall thickness with a digital caliper. Would this work? |
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Cusser Samba Member
Joined: October 02, 2006 Posts: 31379 Location: Hot Arizona
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Posted: Sat Apr 17, 2021 3:29 pm Post subject: Re: Brake drum measurements |
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I'm in Phx AZ, and the big parts stores here don't have adapters to turn old VW drum these days; so maybe a old-fashioned machine shop or a VW shop can help there. I'd guess the parts stores could measure for you.
So what do I do? Even though I "think" a local VW machine shop could turn these, if my own drums feel grooved like an old record, I likely would replace them. I don't generally replace even/smooth drums (or rotors) and jsut do brake shoes (or pads). So that's my 2 cents. _________________ 1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297 |
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modok Samba Member
Joined: October 30, 2009 Posts: 26790 Location: Colorado Springs
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Posted: Sat Apr 17, 2021 3:54 pm Post subject: Re: Brake drum measurements |
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brake drum measuring tools... some are calipers with extended anvils, others are...more difficult to explain, like a ruler with two sliding arms on it.
In any case the reason it's a special tool is t be able to reach in and check the size without going through the middle.
Because in the middle is the hub, or arbor,.....have to reach around that. Measure runout with a dial indicator.
You can feel free to invent your own ways to do it if you understand the principles.
OD minus wall thicknesses would be fine, but is that easier? It is if you can do it.
Any place that deals with brake drums I expect would measure them for you, for free, but who knows. |
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61SNRF Samba Member
Joined: March 29, 2009 Posts: 4657 Location: Whittier 90602
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Posted: Sat Apr 17, 2021 4:40 pm Post subject: Re: Brake drum measurements |
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Look where the shoes wear in the middle, if you see a raised lip around the edge or as Cusser mentions any grooves you can feel with your nail those are indications they need to be turned.
New they are about 9.065" Max inside diameter is 9.115" so there is not a lot there to turn.
Being they are cast iron you really can't get an accurate measurement using wall thickness and besides there are no specs for this.
They make special drum gauges with a dial indicator read-out but they are specialty tools. If your local FLAPS advertises drum turning they probably have one.
You can get a fair measurement with an inside micrometer but those take care and experience to get an accurate reading _________________ -Bruce
An ounce of prevention is worth a pound of cure. |
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Eric&Barb Samba Member
Joined: September 19, 2004 Posts: 24764 Location: Olympia Wash Rinse & Repeat
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Posted: Sat Apr 17, 2021 8:53 pm Post subject: Re: Brake drum measurements |
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This and lots more is explained in the workshop manuals:
https://www.wolfsburgwest.com/cart/DetailsList.cfm?ID=book1
Get one that is applicable to your year of beetle ASAP. Yes, the above is out of stock, but there are other VW suppliers that should have it available. Also do check thesamba classifieds. They do show up from time to time in good used shape for less $$$. _________________ In Stereo, Where Available! |
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scrivyscriv Samba Electrician
Joined: October 04, 2011 Posts: 2922 Location: Memphis
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Posted: Sat Apr 17, 2021 10:01 pm Post subject: Re: Brake drum measurements |
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jcpatrickharrison wrote: |
...Is there an easy way to tell if they are out of round... |
Not really, but the quickest way to check for out of round is mount it in a brake lathe and either check runout with a dial indicator, or actually start cutting. You'll see the wear pattern as you go. _________________ Robert in Memphis
Dünkelgrügen 1967 Java Green bug thread
Engine rebuild thread
If you're ever in the Memphis area, you are welcome to stop by for advice and help. |
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EVfun Samba Member
Joined: April 01, 2012 Posts: 5481 Location: Seattle
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Posted: Sun Apr 18, 2021 9:24 am Post subject: Re: Brake drum measurements |
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If someone made a pushrod that was 230mm long you could get a decent check for round and basic diameter with feeler gauges. You couldn't reach the outside face but you measure at several points around in about the center of the area where the shoes run.
I bought a pair of '58-'64 drums, a low swap meet price on used VW originals, hoping they would be good based on looks. They were to large to run, even though smooth and the lip from previous shoe wear was not very large. I suspect they had been turned years ago and then run through several more sets of shoes. I ended up buying new drums. I was trying to avoid that because rear replacement drums for '58-'67 Bugs are 6mm wider than original '58-'64 drums.
Bug drums should have a new diameter of 230.1mm and an maximum diameter of 231.4mm according to my cheat sheet on brakes. _________________
Wildthings wrote: |
As a general rule, cheap parts are the most expensive parts you can buy. |
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jcpatrickharrison Samba Member
Joined: November 23, 2005 Posts: 294
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Posted: Sun Apr 18, 2021 3:29 pm Post subject: Re: Brake drum measurements |
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Thanks everyone! |
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stevebaz Samba Member
Joined: March 14, 2008 Posts: 189 Location: El Monte CA
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toxicavenger70 Samba Member
Joined: July 28, 2019 Posts: 871 Location: CO
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Posted: Mon Apr 19, 2021 12:53 pm Post subject: Re: Brake drum measurements |
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I though my drums had a imprint on them stating how much they can go before they are garbage. So check and see if you have nay numbers on them. |
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