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Rotors - C6Z front rotors are curved vane but one side only. I think the C6 Z51 front one was also. Meanwhile the C6 Base went from the left and right front and rear (C5) to a pillar vane front and L/R rear. Then on C7's - iirc none are curved vane including the Z06 disc. It's not like GM does not know this. Something is telling them to make an angled/curved vane disc but to not make a L/R. That saves a rotor mold and a part number which is a decent chunk of $$.
That said - sometimes I should be quiet. You should see the friendly Youtube replies
10 point Bolt: I knew the fastener was weird but I didn't see it until the car was on the lift. Got the pads Friday - install Saturday - test on Monday. No time for EBay. I'll still likely replace the bolt so I don't have to keep a unique tool. YMMV
The pads are stuck on the piston pretty firmly. For the first pad swap I'd probably still just pull the caliper.
The one thing I didn't do was to use any threadlocker on the pad pins. There is stuff on there when new. Now that they are not held by a detent or cotter pin it would seem like it's needed. It needs to be semi-permanent but not affected by heat?
The point of the video was to get it all shown so you'll be ready when the time comes. Other than what's discussed there is nothing new other than the semi-odd pad geometry. The car did not go into limp mode from high brake temp's or anything like that. The brakes help up to 3 hours of track time pretty well and we did not change the brake fluid. I should have it back on the lift Wednesday to have a look at it and I'll put up some pics.
-Ken
Thanks for the great video Ken! The two left rotor thing is so weird... Do you think this could be a mistake made on the assembly line? It makes sense that GM would want to save money on castings, but why do two lefts? Why not make them "neutral," so there's no difference in air flow? Really curious.
Thanks for the great video Ken! The two left rotor thing is so weird... Do you think this could be a mistake made on the assembly line? It makes sense that GM would want to save money on castings, but why do two lefts? Why not make them "neutral," so there's no difference in air flow? Really curious.
There is only one front rotor part number so that is what they made.
Further inspection: The vanes are angled but not curved which adds mass and surface and perhaps the flow is not reduced too much going the other way. It's odd. I won't make a KNS rotor that way most likely.
Thanks for the great video Ken! The two left rotor thing is so weird... Do you think this could be a mistake made on the assembly line? It makes sense that GM would want to save money on castings, but why do two lefts? Why not make them "neutral," so there's no difference in air flow? Really curious.
The C7 Z51 only had one rotor part number and it had grooves, so you could tell just by looking that the same rotor was used on both sides.
The C7 Z51 only had one rotor part number and it had grooves, so you could tell just by looking that the same rotor was used on both sides.
Pretty sure they did not want to repeat the mess that was the C7 Z51
The car has been on track for about 4 hours now. While the Z51 brakes so far seem better than the previous gen Z51 cars they are still overmatched a bit for serious track use. Better - but we'll need Z06 or aftermarket BBK's as expected.
FYI - for those changing pads, it is recommended to disconnect the battery to keep the e-boost system from running a self-test that can pressurize the system when you are not expecting it like sometimes when a door is opened, etc. Don't shoot the messenger - I was surprised to read this as you guys probably will be, too.
When servicing vehicles with the Electromechanical Brake Booster, including brake pads or rotor replacements, the battery must be disconnected to prevent the brake master cylinder from pressurizing the hydraulic system during its automated self-diagnostic tests that can possibly occur when a door is opened or the key fob is activated. Failure to follow this precaution may cause personal injury. A “Brake System Failure, 62 mph Top Speed” (or 100 km/h) message will be displayed on the DIC if the battery is not disconnected prior to brake service. (Fig. 11)
Fig. 11
If the battery is not disconnected and the DIC message appears, it will be necessary to perform a hydraulic system test. The test procedure will not be covered under warranty for failing to disconnect the battery.
Good work....Also note, this tool IS NOT NEEDED on the base (non-Z51) brakes. They continue to use the 2 push pin retainers as in previous designs.
That's correct.
I ordered 2 sockets today - we'll see how long they take.
I had the car apart again last night to look it over.
-Did the battery disconnect this time - but I think it won't fire the pressure pump at least from a door open signal.
-The bolt can be easily replaced with something easier so you won't have to keep track of the socket
-Seems like the half-pins are waiting to strip the caliper or the T40 strips. (For the heavy track guy)
I ordered some front rotors and brake lines to get a closer look as well. They may take a while to get.
Not much of this matters to the 'switch to low dust pads' guy but the DIY track guys should be getting at least a little bit of a headstart.
My G-LOC GS1 pads from KNS are being delivered today!
Thanks for your info and pics. Just a note re the Amazon product you bought and I did as well based on your info!
In case anyone reads the purchse comments they may see one that says it doesn't fit all the way. I made this composite from two of your pics and ones from the video!
First, there is a lot of room around the 11 point nut to fit the socket. Second, looks like the main load is placed on the upper part of the 11 point bolt. Just need to be sure the socket is placed properly and not at an angle when starting to remove.
In addition, your comment about it not taking much force to remove makes me wonder why they used it versus a hex on the center bolt on my front 2017 Grand Sport 6 piston calipers. But now I can just concern myself about getting the strong two side brake pad tape separated (lower pic.) Let us know what you used when you install!
Original pic is from my early 2014 Z51 brake pad install that used the same very strong two sided brake pad to piston tape. Note is was not used on the rear (like the C8) nor on later 2014's only the early ones like mind built September 2013.
^^^
Perhaps he's right but considering the caliper strength and thickness it would be hard to over torque with a 3/8 ratchet or even 1/2 inch, IMO. Also it was stated it comes off easy! And I don't buy don't remove it and require folks to remove the caliper to replace pads! It's NOT an unusual or unique safety bolt head like those on my Microwave etc etc. Have sockets and tips for those star bolts with center pins as well. But since I don't know, we'll have to see, perhaps your tech's comment is correct.
I ran Wilwood SL6Rs on a C5 racecar that had a similar caliper bridge bolt. You barely tighten it. You wanted to still be able to spin the bolt and bolt tube just slightly by hand.It keeps the caliper from expanding and would be in tension. Over tightening it would deflect the caliper inward.
JerryU,
I believe 90% of the techs would over torque this bolt and distort the caliper.
The 10 point bolt goes into the back of the top caliper pin. If the bolt puts any tension on the caliper at all, it would be determined by the length of the pin not bolt torgue.
An M8 x 1.25 shoiud only have about 10 ft lbs of torque. The factory bolt had a little blue loctite on it. It loosened up accordingly.
Not having seen anything like this bolt before, I've gotta think that it must have some kind of threaded shaft on the bolt head side to allow the bolt to be torqued down to some amount, rather than hoping for some minimal torque value that limits the tension on the caliper.
05-16-2020, 12:02 PM
Fig. 11
Thanks for your info and pics. Just a note re the Amazon product you bought and I did as well based on your info!
