+1 for using a height gauge and posting photos. OCD is pleased with this

 

That's a significant difference in piston diameters. I presume the reduced diameter portion of the piston is outward facing (seal lip) and possibly what @Drspencer measured as the rest would be obscured by the seal?

@theredgmc Did you experience the same pad overhang issue as @Drspencer did?

BTW... The calipers look a lot better with some color on them. They look so utilitarian out of the box. This post may have swayed me a little closer to these from the Wilwood Aero6 setup.

 

What is also interesting (but not really surprising) is the T1 calipers have the exact piston diameter and volume as the three previous generation floating calipers. The newly discovered PPV caliper piston diameter brings the volume up to 92% of the floating calipers vs 58% from the 1.25" piston measurement. I like this much better for petal feel and actual clamping force. Just for reference the Wilwood Aero6 pv is 5.4 sqin vs 5.83 of the PPV (assuming 1.573" pistons) for a 6.7% reduction as compared to oem floating calipers.

 

Honestly I didn't check for pad overhang. I wanted to rotate my tires this weekend, I'll have to check.

 

I ran into clearance issues with these on my Yukon with same wheels. I choose not to get wheels spacers because I was worried about vibrations, have you experienced anything negative with those? Also why did you use lug centric and not hub centric spacers? I'm going to get into mine again shortly. Is the 1/2 space plenty or would you have gone a tad thicker?

 

It's a tight fits with a 1/2'' spacer. I bought lug centric ones because I could get them the next day off amazon. Some day I'll buy a 1/2'' hub centric spacer. I'm okay with the fitment, others may not like the caliper being that close. I wanted the minimum needed wheel spacer to keep lug nut thread engagement. I personally hate how factory GM lug studs have a 1/2'' of un-threaded portion at the tip. If I was to replace wheel hubs, I'd put fully threaded studs in the hub and then maybe do a 15mm spacer just for piece of mind.

 

While you have that 4 piston apart, you mind measuring the thickness behind the pistons? Someone was curious how much material is back there as they have that little bump out on the outside that hits some wheels. I have milled a couple sets down at their request but was curious how much can be removed. Consider its flat on the inside behind the pistons but the outside has that casting bump. I just figured it has something to do with the casting process.

 

Do you feel that the 15mm will leave enough factory lug nut threads to be safe? I'm going to order some today.

 

Or advise as to what wheel offset will clear. For some reason I can't get this thru my old man head.

 

My wheel is a 22x9 with a 24mm offset. A 1/2'' (12.7mm) wheel spacer makes an offset of around 11mm. The inner profile of the wheel determine if it fits or not, because not every wheel type or design is the same. Sorry, but I don't want to advise what would be safe to use with spacer or not.