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Old 11-25-2011, 03:07 PM   #1
wildcatlock
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c4 rear brake upgrade details and pics

Ok after much searching and research I have found another way to upgrade the rear brakes on an early c4. There is a guy making modified parking brake shoes and brackets for the use of c5 calipers and c6 z51 rotors on the rear of early c4 and I think he has the parts for late c4 as well his email is dcgls1@comcast.net . Prices are way less than the speed shop parts (though not as much bling ). I have then ordered and almost installed and will post with pics when done. Only snags so far are the brackets had to slightly midified to keep the abs sensor and change a few bolts. ( I have to email him about these issues ) but if you have an 84-85 they dont have the abs so will be a straight bolt on deal and are good looking parts. You use the c5 calipers, pads, and abutments and a c6 z51 13" rear rotor and get to keep the parking brake but need 17" wheels minimum ( no problem there if you are upgrading the front to c5 / c6 then you have to use 17" a-molds or larger anyway ). Just thought I would do a quick post to let all know there are options out there if your interested. Should provide a bit more stopping power with the much larger rotors, I guess no longer is it not worth it to upgrade the rear brakes on a c4. What do you guys think?


Last edited by wildcatlock; 12-26-2011 at 03:32 PM. Reason: added pics
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Old 11-25-2011, 05:13 PM   #2
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Quote:
Originally Posted by wildcatlock View Post
I guess no longer is it not worth it to upgrade the rear brakes on a c4.
What do you guys think?
For those interested in actual performance and not just "wow" factor ,would be interesting to see if it makes a difference worth the cost and effort ;
seeing that the bulk of braking is done by the fronts ( esp hard braking )

Given the brakes have been available since '97 and there was a rapid uptake of the C5 fronts on a performance / cost basis (vs J55 option );
if there was a perceived advantage of using the rears then more would have fitted them in 14 years

Last edited by vetteoz; 11-26-2011 at 03:30 PM.
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Old 11-25-2011, 06:37 PM   #3
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Did you do any stopping tests prior to tearing down to see if there is an improvement when you are done?
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Old 11-26-2011, 07:04 AM   #4
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Yes but brakes were stock non hd and worn out. With the c5/6 front upgrade the stock rears always looked a bit small to me so we will see how these do. I have a g-tech meter and all info from stock brakes so I will test again when completed, although it wont be totally accurate as the entire suspension is also undergoing a complete rebuild.

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Old 11-26-2011, 04:04 PM   #5
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this uses the c6 z51 rotors and c5 calipers. The 13" rear z51 rotors started in 06 if I recall correctly so that woould only be 6 years tops. I agree that there is no advantage to using the c5 rear rotors for the cost but if you go to the c6 z51 13" then you are +1" diameter and almost 1/2" thicker than the c4 stock rears. Should be an improvement if for no more than fade resistance( added mass )and for what I have in the set up ( under 500 ) worth a try. I had the rotors and calipers w/ abutments left from when I purchased the parts for the c5 front upgrade.
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Old 12-02-2011, 05:05 PM   #6
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I am interested ,only because the rear c4 calipers are ugly as hell ,compared to the c5s.
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Old 12-03-2011, 06:37 AM   #7
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small update. I have contacted Dale ( the parts guy ) and we are in the process of getting them to be "bolt-on" for 86-87 also. He used an 85 hub for mock-up and didnt realize until it was mentioned. I have sent him pics of the needed mods and I think I have a raw set comming to mod and return to him for a pattern. I think I also am going one step further as I have found that the 06 j56 rear rotors are slightly bigger still at 13.4" vs. 13". Looks like they will fit without much trouble and really fill up the wheel. Plus they are drilled from the factory and a bit lower in cost than the 13" j55 rotors. Getting real cold here so work may slow for a bit but I will get it posted with pics when complete.
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Old 12-03-2011, 06:43 PM   #8
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What about an 89?
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Old 12-04-2011, 06:23 AM   #9
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89 has e-brake in the caliper correct? If so then it can be done but you will lose ebrake. If not and they are in the rotor had then this would be perfect. Hope that helps. If you arent looking for a size upgrade then just swap the calipers I think they will bolt up to the c4 abutments with no issues( have to check though ) rotors are not as thick but with new pads might be ok. Might work if you just dont like the look of the stock c4 calipers.
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Old 12-14-2011, 09:30 PM   #10
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I am trying to use the c5 rear brakes also but Im using the stock size c5 rotors will these brackets work?
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Old 12-15-2011, 03:35 PM   #11
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Not with the c5 rotors you have to use the c6 13" rotors from 2006 - up j56 brake package and a c5 caliper and abutment. I have been trying it with the J55 13.4 rotors for 06-up but it requires at least an 18" wheel and I am working with Dale to get the adapters right for that rotor so they would be a bolt on affair. Found the 13" rotors at o'riley auto for about 80 ea. new and the 13.4 for a bit less. As far as I have found that is cheaper than the c5 rotors. These rotors are also at rockauto.com for 48 ea part # 580407 . Hope this helps you out. I will be updating progress soon as we get the abs issues addressed so he can go into production as a bolt on for 86-87. Kind of holding up progress so I dont have to keep tearing it back apart. Do it once - do it right kind of thing.
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Old 12-16-2011, 08:30 PM   #12
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I already have the c5 rotors and calipers and abutments I wonder if I can get the brackets to fit into the space or if I can weld the material so I can attatch the c5 abutment brackets
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Old 12-17-2011, 03:49 PM   #13
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I already have the c5 rotors and calipers and abutments I wonder if I can get the brackets to fit into the space or if I can weld the material so I can attatch the c5 abutment brackets

The c5 abutments work fine just need to use the c6 13" rotors. The c5 rotors are 12 1/4" if I remember correctly and the way these brackets are made if they were drilled for the c5 rotor you would have interference with the hub. Only thing it looks like you would need is the c6 rotors listed above. I am going to update this thread shortly so check back. I got the part templates done for Dale and will be getting them back to him this week, so I could now finish up with the upgrade and will post pics and details later. Does this clear things up a bit?
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Old 12-17-2011, 04:34 PM   #14
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Ok I finally got the brake upgrade done so here is a little walkthrough of what was involved and some pics.

first here are the parking brake shoes available from dale (email address posted above)

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Old 12-17-2011, 04:40 PM   #15
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I had to modify the brackets he sent, but this should soon be resolved as I have sent him a template part for the abs sensor relief. He mocked up the original parts on an 85 hub so didnt have the abs on it. anyway this is what I had to do to get them to work. These are the modified bracket compared to the original as sent bracket.




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