Have heard some conflicting stories so looking for an answer. I have a 2008 base with the Z51 package, do the Powerstop Z26 rotors fit the rear of my car. I was told by someone they were too small and the Z23 rotors are the right size. Website says they do but real world knowledge is more valuable to me

 

with Z-51 you need Z-26. Now powerstop has different levels too, that’s just their most expensive.

I’d go on the RockAuto website, they generally have the best deals and it’s all laid out nicely.

Sorry, Z-26 is Powerstop’s Level of Performance in a way, that’s their “High Performance” Brake Pad/Rotor

Z-23 is their “Premium” line of brake pads/rotors.

If you go to Rock Auto or generally anywhere it will say with Z-51 Package or without/standard brakes.

 

Z23 and Z26 are 2 different product lines from PowerStop. In either case, you need to match the specifics of your car to the kit number, which you can do from this entry point https://www.powerstop.com/resources/...BoCbHsQAvD_BwE

If you go through the selection process, you’ll see that each product line has an offering for the rear for rotors and pads for your Z51. I’ve got their Z26 kit on all 4 corners of my GS.

 

I've come to think the person I was talking to either was clueless or they had a packing error from the factory. I think I'm going with z26 package, I don't track but I am known to do some very spirited mountain driving

 

GM OEM HD pads will have the highest of working temps for any street pad your going to find for the car, that will also hard bite dead cold as well. Hence second to none for initial bite, pedal feed back, and working temps to prevent brake fade on the street.

Bluntly, the J55 and JL9 brakes use the same size brake pads, and it comes down to the material that the pads are made from that is bonded to the backing plate.

Having had street pads catch on fire during road driving heavy use, the first thing that I always look at is the working temp range of the pads above all else.

 

i thought standard brake have smaller rotors. and the J55 which were an option for non z51 came with bigger rotors. So you have those two option
Then GS/ Z06 have a different setup instead of two pads they have 4 per side

 

JL9 is the base calipers with smaller rotors, while the J55 is the same size caliper (different size pistons in the back), with larger rotors.
The JL9 and J55 use the same size brake pads, and on the J55 system, different caliper brackets to move the calipers more outwards to work with the larger rotors.

On the GS, its a wide body car, so uses the caliper and rotors from the Z06, (that are not either JL9 or J55 rotors used on the narrow base car).

Bottom line it, in 2010, GM did away with the Z51 option for the base car for autocross built use, and came out with the wide body GS (steel frame) that used z06 brake parts for autocross use instead. As for upgrade the GS brakes, would be the z07 option, which would the Zr1 larger rotors (carbon or steel, which would need the larger ZR1 rims, to give the needed clearance for the larger rotors).
As for pads on the GS, can come in either padlets, or you can get pads that are one piece per side instead.

So bottom line, when it comes to either the Jl9 or J55 calipers, they do use the same size pads per front and back, and it really comes down to the pad material of the pad steel backer plate. The OEM HD J55 semi metalic pads are a lot more aggressive to give better initial bite and pedal feed back, have a higher working temp so you don't melt them during Autocross use, but do wear out faster, wear the rotors out faster as well.
If our looking for a pad that will give better life, less dusting, slightly lower working temps that the oem HD pads, but not give up the initial bite and pedal feed back, then would look at the 1521'.
If you are just looking to go cheap, then the Duralast ceramic pads will go for around $100 for all for corners, but going to give up intial bite, pedal feed back, and lets face it, use the brakes hard enough, going to melt the pads as well.

To bottom line it, until Power stop does give some specs on their different pads in regards to temp friction, and even temp ranges, better off going with a brand that does from the start.

 

Thanks for a super through post. Really great info