Drilling 11" drums with fins????

Hey Gang,

OK, did some hunting/gathering for 11" brake parts today. NAPA had all parts listed on the tech page, but there were some problems. I'll focus on a specific one.

The drums from NAPA were finned. I checked at AutoZone and Checker, neither had the drums in stock, and Checker quoted me some stupid price like $105 per drum. If AutoZone follows suit (I didn't ask the price yet) then I'll stick to the NAPA drums.

However, I'd still like to drill them. It gets dang hot here, and any advantage I can gain will be useful....

That means that if I want to do 3 rows of holes around the circumfence of the drum, I'll be drilling on row into the narrow diameter, one row between the fins, and another row in the thicker part of the drum. (Where it comes over the backing plate.) Can anyone think of a reason why I couldn't/shouldn't drill out the finned drums? Should I only do 2 rows instead? Any thoughts?

For those interested, the other problem I ran into was the NAPA hardware kit only includes the hold down hardware. That is the springs, pins, and slotted washers to hold the shoes to the backing plate. Checker had a more complete kit with all springs and holding hardware. They also gave me a part # for the self adjuster kit so I can go to the main store tomorrow and hopefully get everything I need. Only thing I'll be missing is the stupid pins for the wheel cylinder to shoe.

On a good note, the AZ and Checker guys I dealt with were quite helpful and respected that I knew what I was talking about. Nice for a change as opposed to some kid who thinks he has all the knowledge of the world in his computer monitor....

I'll be keeping track of all this stuff and doing a write up for my site when I'm done. Hopefully this will keep others from having to dig too hard.

 

Thad,
How much did nappa want for the drums?
Steve

 

I would think twice about drilling finned drums. The fins were put there to help dissapate heat and although drilling should help, I would be afraid of damaging the drum and maybe screwing up the balance.

As always, I could be wrong. Just my thoughts.

 

$78 each. I did see that Krage's had the non finned for about $50. I also have a couple 4x4 places I'll be checking on Monday. If I can get them for around $50 each, I'll be taking the finned drums back.....

 

what Tom said
x2

 

Balance doesn't worry me. I'll be using my mill with a rotary table. Having scribed a 14" circle with 1440 ticks around the perimeter and coming out exact at the end, 2~3 rows of 20 holes or so on a 11" drum will be a cakewalk. Still, I'll be looking for the non finned ones first....

 

Hmmm, you can see where he's drilled through the double flange to get to the braking surface. That tells me he's not afraid to go through the thicker part, so all I need to worry about is making sure that I line up between the fins. I wonder if he rebalanced after he was done drilling or if he didn't sweat it? It would seem that you would end up with a slight imbalance by drilling through different thicknesses. Interesting, very interesting....

It's also clear that he moves each successive hole over the thickness of the drill bit so that, as Mike said, every part of the pad gets swiped by a hole. Now I"ve got some mental gymnastics to do.....

Still gonna see about the non finned first tho'......

 

When I checked with AZ, they carried 2 drums, One for about $50 and one for about $90. I don't remember what the difference was. I think I would space the holes so that I was drilling between the fins. Makes for an interesting challenge on how to figure out a balanced spacing. Good luck.

tommy b

 

I decided to wait on the drilling and after installing 11"ers on both axles and test driving it, I'm not sure if I would want my brakes to work any better wet or not. I swear the rear axle lifts off the ground when I lock up the brakes! I

 

Staggering the holes so they cover the whole surface of the shoe seems kind of overly anal to me, and a lot of extra work. How many of you have actually done that? The photos that Billy's posted of his drums with two roles of holes look entirely adequate to me. That's how I'm gonna do them.

 

:iagree: But I imagine that anything we do in that regards has to improve things. I'll probably set up to stagger the holes as shown to gain the maximum benefit. Doesn't take any super effort once it's set up in the mill.

Oh, BTW, I took the finned drums and the bogus hardware kit back to NAPA. Got back just over $200. I'll be looking for the non finned tomorrow.

 

not many rivers/streams/creeks in Phoenix to worry about

 

There is a guy on ebay that sells both regular and finned for decent prices. I will try to find a link to his store and post it.

If you want to drill some, I have a pair of finned ones I bought off ebay and one of them had most of the fins rusted off. I decided to go with a pair of regular drums for now. I am thinking of keeping the better finned one and try to find a mate someday.

You can have the one not so good drum for free plus shipping if you want. They are kinda heavy and I don't know if it can be turned enough to be usable. Might be a good one to experiment with before you drill good ones anyway.

Jim


Edit:

Here is a link to the guy who sells 11" brake drums.

http://cgi.ebay.com/ebaymotors/POST...ewItemQQcategoryZ33565QQitemZ8032093328QQrdZ1

It doesn't look like he has any listed right now. I talked to him by email once. He works on postal Jeeps and usually keeps both kinds in stock. As I recall, his finned drums were not much more than the regular.

As for regular drums, I had one that was a ford that I had the center hole cut out to go over the hub. It is a much heavier drum than the Jeep. I think I would much rather have ford drums than Jeep drums if they are not the finned ones.

JC

 

True, but the holes will help vent the brakes as well. Preventing brake fade is a good thing.

 

Thanks Jim, but I'm going to see what I turn up locally. I'll PM you if I decide to grab that from you. Appreciate the offer.

 

Billy... the photos I have of your drums look like there's two rows of holes, and both rows are straight. Like if you put them on a lathe and scribed two lines around the outside, then drilled the holes on each line, only staggering the holes in relation to each other.

The drums above look like the holes "spiral" across the drum. Like drill the first hole near the edge, turn the d/h 2 turns, dial the table in .125 (1/8th inch), and drill the next one, etc.