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Old 12-11-2018, 10:32 PM   #1
GIZZ
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Rear disc brake kit trouble

Im sure somebody here has seen this and has a solution. Im having issue fitting the rear brake rotors on my 69 c10 axles(narrow). The rear rotors in this brospeed kit have a 3 center bore, my stock axles have a 3.55 hub on the axle flange. Did they give me the wrong rotors? Is there something wrong with my axles?

Any ideas? Whats the best solution?

TIA

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Old 12-12-2018, 02:15 AM   #2
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Re: Rear disc brake kit trouble

You need different rotors. The ones you show would likely fit an '88-up truck for a rear disc conversion. Don't waste your time trying to machine the rotors or the axle. Get the right part and save yourself some trouble. Years ago the flange on one of my axles of my '89 got tweaked somehow and the disc conversion I had would thump every time I applied the brakes. I ordered a set of axles from Yukon and they were the type on square body trucks and not the GMT400 trucks. They made it right but I learned the difference between the two at that time. Sorta long, but take the time to get the correct rotors.
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1989 K1500 Chev. EC
Original owner; some of the aftermarket parts I've installed are Borla headers, Hypertech chip, Edelbrock water pump, and a Stillen rear disc brake conversion kit.
2009 Hummer H3T 3.7L 5M.
1997 K2500 Chev. EC 7.4L/ 4L80E
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Old 12-12-2018, 02:25 AM   #3
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Re: Rear disc brake kit trouble

These pics should help. Earlier this year I was worried that I didn't have replacement parts when my rear pads wore out on my conversion. Turns out that the calipers are the same ones used on my '98 Firebird so I used the spare pads I had along with the DBA Aus rotors I had resurfaced. Problem solved on my '89.
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1989 K1500 Chev. EC
Original owner; some of the aftermarket parts I've installed are Borla headers, Hypertech chip, Edelbrock water pump, and a Stillen rear disc brake conversion kit.
2009 Hummer H3T 3.7L 5M.
1997 K2500 Chev. EC 7.4L/ 4L80E
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Old 12-12-2018, 02:50 AM   #4
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Re: Rear disc brake kit trouble

Thanks for the reply,

Your '89 setup has a 3" hub. Do you know what rotor is used? It looks like a gmt800 1/2 ton front rotor.

These aftermarket early 6 lug kits, I wonder if they just take the '99-07 1/2 ton front rotor and bore the center from 3" to 3.5"
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Old 12-12-2018, 01:42 PM   #5
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Re: Rear disc brake kit trouble

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Originally Posted by GIZZ View Post
Thanks for the reply,

Your '89 setup has a 3" hub. Do you know what rotor is used? It looks like a gmt800 1/2 ton front rotor.

These aftermarket early 6 lug kits, I wonder if they just take the '99-07 1/2 ton front rotor and bore the center from 3" to 3.5"
I'm pretty sure they don't re-bore the hole for the hub. The hat on the rotors on my truck are shallower than the hubs on a GMT800 truck. I also have the internal expanding drum for the emer. brake. That rules out front rotors. The kit on my truck was discontinued a number of years ago. I tried the SS Brakes and Baer kits and felt that the Stillen kit was the best rear disc conversion at the time. They have conversion kits (Baer & SS Brakes) now that are double the $$$ that I paid. I mentioned in the previous post that my rotors are DBA Australia rotors and they are still available. I don't know what vehicles they were originally made for. I have to look for the spare set I have for a part #; buried under boxes in my garage somewhere.
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1989 K1500 Chev. EC
Original owner; some of the aftermarket parts I've installed are Borla headers, Hypertech chip, Edelbrock water pump, and a Stillen rear disc brake conversion kit.
2009 Hummer H3T 3.7L 5M.
1997 K2500 Chev. EC 7.4L/ 4L80E
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Old 12-12-2018, 02:54 PM   #6
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Re: Rear disc brake kit trouble

I found my spare rear disc rotors. They are DBA-Aus part#DB 0015M. I'd like to find out what vehicles they also fit in a stock application if that's what they were designed for.
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1989 K1500 Chev. EC
Original owner; some of the aftermarket parts I've installed are Borla headers, Hypertech chip, Edelbrock water pump, and a Stillen rear disc brake conversion kit.
2009 Hummer H3T 3.7L 5M.
1997 K2500 Chev. EC 7.4L/ 4L80E
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Old 12-12-2018, 07:54 PM   #7
VictoriaHardware
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Re: Rear disc brake kit trouble

bro-speed should not be advertising this kit as fitting your truck when it will not fit your axle. You can get all your money back through ebay.
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Old 12-13-2018, 02:28 AM   #8
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Re: Rear disc brake kit trouble

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Originally Posted by VictoriaHardware View Post
bro-speed should not be advertising this kit as fitting your truck when it will not fit your axle. You can get all your money back through ebay.
I never thought of that, I checked eBay and they list it as 6x-69 6 lug and also now mention 3 bore, well that makes no sense. They havent replied to any of my msgs, I think they also operate under sae-speed. Id be happy just to get the replacement info at this point, I modded them today.
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Old 12-13-2018, 03:29 AM   #9
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Re: Rear disc brake kit trouble

Brave man! Do those rotors fit snug on the hub now? Those rotors actually look very similar size-wise to the rotors on my truck (before the hub boring). Do they also have the internal drum brake surface? It looks like they do from the pic you posted.
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1989 K1500 Chev. EC
Original owner; some of the aftermarket parts I've installed are Borla headers, Hypertech chip, Edelbrock water pump, and a Stillen rear disc brake conversion kit.
2009 Hummer H3T 3.7L 5M.
1997 K2500 Chev. EC 7.4L/ 4L80E
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Old 12-13-2018, 02:35 PM   #10
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Re: Rear disc brake kit trouble

They do have the internal drum surface machined in to the inside. I'll take full measurements and post it up for reference. I'm thinking about sending the dimensions into maybe Centric and see if they would be so kind as to help out as to what they are from. I seriously doubt these companies are having rotors spec'd and made.

The center bore, unbelievably I used a 3.5" Milwaukee bore saw and the bore is almost exactly that. The axle is like 3.55" so I need to take the rotary file to it today.

I don't like the fact that replacing the rotors in the future will not be easy, I see you will be in the same boat once you are done with your spare set. I'm considering saving up and changing the whole setup which may include the wheels.
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Old 12-14-2018, 02:20 PM   #11
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Re: Rear disc brake kit trouble

I should measure my spares when I have the time for comparison sake. One of the websites that I bought some of the Brembo rotors I installed on my vehicles also included specs of the rotors. That was over ten years ago and I just don't find that information anywhere at this point in time. Even the Brembo rotors I used are hard to find now. I sent an e-mail to dbausa.com and never received a reply yet. DBA AUS was very helpful, but they are in Australia which makes that help difficult, to say the least.
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1989 K1500 Chev. EC
Original owner; some of the aftermarket parts I've installed are Borla headers, Hypertech chip, Edelbrock water pump, and a Stillen rear disc brake conversion kit.
2009 Hummer H3T 3.7L 5M.
1997 K2500 Chev. EC 7.4L/ 4L80E
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Old 12-16-2018, 02:19 PM   #12
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Re: Rear disc brake kit trouble

I have the rotors fitting over the axle now with very minimal runout.

I took some measurements of the rotors, I now see I forgot the center bore size.

It looks like I might be able to use 80ish k10 front rotors with a large 4" center bore on my rear. Might need to shim but overall the dimensions are close.
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Old 12-19-2018, 01:34 AM   #13
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Re: Rear disc brake kit trouble

Funny I just ordered Moser replacement axles for my 66 and the register on the end of the axle is 3" not 3.5 like the factory axles which for me is ok because I'm doing a disc brake kit on it as well.
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Old 12-19-2018, 03:45 AM   #14
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Re: Rear disc brake kit trouble

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Originally Posted by wichita View Post
Funny I just ordered Moser replacement axles for my 66 and the register on the end of the axle is 3" not 3.5 like the factory axles which for me is ok because I'm doing a disc brake kit on it as well.
Are you sure they're going to work? The diffs are different. When I ordered new axles I was sent axles for the earlier truck for my GMT400 and I had to send them back. Might have to check on that.
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1989 K1500 Chev. EC
Original owner; some of the aftermarket parts I've installed are Borla headers, Hypertech chip, Edelbrock water pump, and a Stillen rear disc brake conversion kit.
2009 Hummer H3T 3.7L 5M.
1997 K2500 Chev. EC 7.4L/ 4L80E
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Old 12-21-2018, 11:50 AM   #15
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Re: Rear disc brake kit trouble

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Originally Posted by wichita View Post
Funny I just ordered Moser replacement axles for my 66 and the register on the end of the axle is 3" not 3.5 like the factory axles which for me is ok because I'm doing a disc brake kit on it as well.
What part # did you order?

I thought no almost every c10 kit would use rotors with 3.5" centre bore, no biggie usng those over a 3" axle pilot IMO as the studs will centre it. What size stud holes in the new moser axles?

One last thing about this kit, the rotor offset or the caliper bracket offset is slightly off. I've now flipped the brackets side and shimmed them out the correct amount to avoid drag. Thea bracket also placed the caliper so far in that the pad hits the rotor hat, either that or the rotor hat is too wide. I ground the brake pad backing to make it work.

Overall this kit has been a fail, I would not buy again.
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Old 12-21-2018, 02:12 PM   #16
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Re: Rear disc brake kit trouble

I was reviewing some pics from '05 when I installed my Stillen disc conversion in my GMT400 truck. This kit has been discontinued, but I thought it was the best one out there at the time. In the past year I needed new brake pads and it turns out that these calipers are the same PBR calipers used on my '98 Firebird so I had spare parts available. I was worried for a short time but that got resolved.
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1989 K1500 Chev. EC
Original owner; some of the aftermarket parts I've installed are Borla headers, Hypertech chip, Edelbrock water pump, and a Stillen rear disc brake conversion kit.
2009 Hummer H3T 3.7L 5M.
1997 K2500 Chev. EC 7.4L/ 4L80E
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Old 12-21-2018, 06:13 PM   #17
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Re: Rear disc brake kit trouble

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Originally Posted by Mr_Rich View Post
Are you sure they're going to work? The diffs are different. When I ordered new axles I was sent axles for the earlier truck for my GMT400 and I had to send them back. Might have to check on that.
Yes they fit, I'm assuming the register is smaller because they're 5x5 bolt pattern so you wouldn't be using the stock drum brakes with them
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Old 12-21-2018, 06:23 PM   #18
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Re: Rear disc brake kit trouble

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Originally Posted by gizz View Post
what part # did you order?
moser a30-65gmt5

Quote:
what size stud holes in the new moser axles?.
1/2"
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