[rusty_sojah]

So not sure if it is that simple or not but since my car is not from USDM it seems much trickier for me to order the correct size rotors/pads for my car as a performance upgrade.

I'm trying to order better than stock without breaking the bank. on past cars i usually get something like stop tech rotors and hawk pads or whatever i can find at a reasonable price and i like those companies since I've used many times. On my new to me 2017 440i that was made for the JDM market i can't use the standard ecs or fcp upgrade kits it seems since my fronts are 340mm (think I'm good here) but rear rotors are 300mm and seem like the caliper is much smaller. Can anyone help me figure out what size pads i need, and will any newish 300mm bmw rotor work or does it have to be a specific one?? All the US sites seem to say the 300mm rotors are all for like the x28i models. But i can confirm they are coming in at 300mm for me on a 440i from the factory.

I'm looking at ordering the ECS v5 340mm rotors for the front and Stoptech z32 pads since they are flawless on my other LS460 F sport with the big breaks and zero dust + silent and cheap. But am at a loss for the rears ATM. Thanks all! Photo for reference.

[rusty_sojah]

It looks like a bmw OEM part number for the 300mm rotors might be 34-20-6-873-094 but i really have no idea. So how could i find some decent better than OEM pads based off this?

[_ObiJon]

My 428i originally came with 300mm rear rotors. According to realOEM.com, the part number is: 34216864900

[rusty_sojah]

Originally Posted by _ObiJon

My 428i originally came with 300mm rear rotors. According to realOEM.com, the part number is: 34216864900

Thank you for this. Were you ever able to source any aftermarket pads or rotors that were the same size as factory (plug n play) for your rears?

[_ObiJon]

Originally Posted by rusty_sojah

Thank you for this. Were you ever able to source any aftermarket pads or rotors that were the same size as factory (plug n play) for your rears?

Yes, tirerack.com, RockAuto.com and ebay have an assortment. However, when I had to replace the rotors/pads, I installed the 330mm calipers and did the upgrade.

Have you measured the rotor yourself? I only ask because I'm 99% positive that regardless of rotor size (bosch calipers), both setups came with the same backing plate. So depending on the rotor, you would see "more of it". Yours looks like mine, after going to 330mm rotors.

See my pics for before/after. I may be wrong but it's worth just taking out a tape and measuring twice.

[rusty_sojah]

Originally Posted by _ObiJon

Yes, tirerack.com, RockAuto.com and ebay have an assortment. However, when I had to replace the rotors/pads, I installed the 330mm calipers and did the upgrade.

Have you measured the rotor yourself? I only ask because I'm 99% positive that regardless of rotor size (bosch calipers), both setups came with the same backing plate. So depending on the rotor, you would see "more of it". Yours looks like mine, after going to 330mm rotors.

See my pics for before/after. I may be wrong but it's worth just taking out a tape and measuring twice.

Yes I measured the rear rotor size at 300mm. the fronts that came on the JDM m sport brake like entry level option here in japan where i am are the 340mm unfinished calipers so this is what is making finding the correct pairs difficult for me on US sites.

I have not checked tirerack or rack auto but the other 5 i have checked all had it layed out like the same, wherein you select your year/make/model, then when you found the size you needed it was pretty vague saying, only for fronts with blue or red or that say m sport or the brembo fronts. this is why i'm super sketched about which rears to get.

like literally why does it say if you have these fronts these are the rears for you, instead of saying something like if these are the rears you have then these are the rears you need.....?

[rusty_sojah]

i'm looking at tirerack right now, it says if you have the M sport brakes on one set of rears, on another pair it doesn't say the rear size only says rears that car has 312mm fronts... WTF man. not directed at you but why is this so convoluted...?

not a single rear says the size of the rotor on tirerack... onto rockauto now.

[rusty_sojah]

okay thanks looks like RockAuto is the ticket!!!! i think i see a winner here for the rears, what do you think? obviously it says excluding ones with xyz front, but i think i need to throw out this whole bit and just focus on the fact that it says for 300mm rear and accompanying pads. since i am getting z23 front pads i like this setup the most!

https://www.rockauto.com/en/moreinfo...9TvZoAV0v0JIud

[johnung]

What are the last 7 digits of your VIN? So you have front Brembo four piston calipers over 340x30 rotors. And single piston Bosch calipers over 300x20 rotors? With the VIN I can see what’s going on on realoem. Gotta check your rear e-brake diameter too

[rusty_sojah]

5c32285 here is the vin. i honestly have no idea what i have. on the vin lookup site that worked with my vin (not all US sites work for a japan JDM bmw vin for some reason) it didn't tell me the brake package.

but i can tell you i have 340mm fronts with grey unfinished calipers. let me go get a pic quick. thanks man.

[rusty_sojah]

i just remeasured and i think my fronts are 330mm now after triple checking.

really glad we had this talk, i was moments away from ordering 340mm z32 kit from ecs.

can you tell by the photo if these are single piston or 2 piston?

[rusty_sojah]

if i'm not mistaken looks like this kit here is 330mm front rotors and 300mm rear rotors z23 upgrade kit.

https://www.rockauto.com/en/moreinfo...9TvZoAV0v0JIud

[rusty_sojah]

after further research it appears i have these M Sport Trim brakes that came stock on a 428i on my 440i with the m package well good to know. thanks for all the assistance ordering a kit now.