OEM Brake Caliper Piston Size
 

Are the front and rear piston size the same? I stupidly dropped one and now have to get a replacement. I'm looking at Centric with part # 146.40012 but they also have part # 146.40041. I think I'm supposed to get part # 146.40041. Looks like Toyota have the same part number for front and rear. They also look like the same dimensions when I put them side to side. Just want to make sure before I pull the trigger on the Centric 146.40041 part.

I think I figured it out. 146.40012 is for the smaller rotor calipers and the 146.40041 is for the bigger rotors they sell in the US or as the GT or GTS for foreign markets don't know which one. Bleh looks like the one I need is sold out everywhere.

So it broke when you dropped it? I wouldn't have thought it would be that brittle.

Sorry, that's not a particularly helpful reply but I'm definitely curious.

Not broken but left a noticeable deep scratch on the surface. I rather not risk leaks by testing my luck with it.

I was under the impression the fronts were 42.8mm and the rears 40.4.

The non-us 277mm fronts should still have 42.8mm pistons, that's the size in literally every subaru 2-pot caliper. However, there are more than one caliper manufacturer and the front of the piston and dust boot setup varies.

The smaller rear brakes probably have 38.1mm pistons.

Interesting. They look exactly the same but I don't know how easily I can tell 2.4mm. I would think I can tell the difference. Toyota and Subaru also gives the same part number for the pistons so I hope they are the same size.

Any confirmation that the 277mm front calipers have same piston size as the US calipers? If anything I'm 90% sure the 146.40041 is for the fronts if different size. I took a measurement of the front and rear pistons with a tape measurer and it was the same diameter. It was around 40mm or so give or take.

I looked at Centric website and got the tech details for their remanufactured calipers and the bore size is 40.5 front and rear. Their caliper piston size is 40mm. The smaller non-us calipers have the same bore and piston size but other specs are different but they couldn't tell me without comparing side by side.

Either way the part I need from them is out of stock everywhere which sucks since the part is $45 from Toyota.

CL/FB/OU/Ebay/Junkyard and pick up a used caliper and rip the piston out?

Yea that's the plan. I'll just get a single caliper from ebay that way I have an extra piston in case I get clumsy again.

The Zenki models should have 42.8mm pistons. The Kouki models should be 40.5mm

Ugh I give up on this caliper piston stuff lol :bonk:. I just bought a single 2017 brz front caliper. I guess I'll find out if there's a difference.

You could buy a different kind of caliper and measure them yourself.


also wtf do zenki and kouki mean

Yea I now have a set of 2014 frs calipers currently on my car, a set of 2015 brz limited calipers, and a single 2017 brz front caliper. I think I have an okay sample size to get to the bottom of this.

I think zenki is 2013-2016 and kouki is 2017+.

kooky is what i call crazy people!

I don't speak Japanese so may not be exact but seems to be the common definition given when I googled.

Zenki = before
Kouki = after

It is used when talking about cars to refer to different versions of the same gen (like the 2017 facelift).

Let us know what you find size wise. I see there was an updated part number but seems all years can still use the current one for the pistons.

hey sorry for the semi off topic but I had a quick question:

I've never ordered rotors online before, and Im looking at a new set on rockauto and I don't get the two different sizes 277mm or 292mm? Is the front and back rotors different sizes? Other than cost is there any reason not to get the 292mm rotors for front and rear?

This is what I'm looking at, the centric ones under daily driver with the heart icon:

https://www.google.com/url?q=https:/...4i58U7_n2jNYrQ

Any advice or guidance form more experienced folks would be greatly appreciated, I gotta order some asap so I can hopefully do the job by next weekend.

Since you're in the US, we only got the bigger rotors. I believe if you were to run the smaller rotors, the pads will overlap the rotors. I think the smaller rotors are narrower too and the rear rotors are solid, not vented. You really want the larger one which fits our calipers and bracket.

Cool thanks man, and it is the same size rotor all round correct?

Not sure but the front and rears are different since the rears have the drum ebrake. So make sure you get a set of front and a set of rears. Not 4 fronts or 4 rears.

Fronts are 292mm and get specifically the VENTED rear rotors.

These are the Centric part numbers for the rotors I bought a while back:

Fronts: 12047021

Rears: 12047031

Awesome thanks man, that helps a lot. I see both those part#s so I will just order 2 of each. Doesn't help rockauto does not label which ones are front and which ones are rear. I was about to order 4 fronts lol.

Update - So I got the 2017 caliper and haven't removed the piston yet but it seems like the exposed part of the piston is the same diameter as the ones I have now.

So I'm just going to say its the same all years at 40mm or something. Not sure where the 42.8mm and 40.4mm numbers came from other than that's what they were for other Subaru models.