[d1mitrov]

Hey guys so i have a 2015 335i msport package without msport brakes. I was wondering if the 370mm rotors will fit my current calipers. The rotors i have now are 340mm. Some one told me they are interchangeable just wanted to double check.

[FaRKle!]

The 370mm rotors are only interchangeable in the sense that they mount up to the same holes as the 340mm rotor. Your caliper can't support the 370mm rotor. It would need longer mounting pylons/ears to do so.

[d1mitrov]

yea i didnt think so but a friend of mine was telling me otherwise...

[5mall5nail5]

Originally Posted by d1mitrov

yea i didnt think so but a friend of mine was telling me otherwise...

Think about it - if your caliper, as is, could work with a disc that sticks 15mm further into it then your car would currently have brake pads that overhang the rotor and clamp onto nothing.

I am really not sure why people are confused about the 340/370/380mm rotor thing. The 340mm calipers mount 15mm inward of a 370/380mm caliper. The reason a 370mm caliper can work on 380mm rotors is because 380mm = M3 upright which have longer mounting ears, so they space the 370mm caliper out 10mm by means of where they attach to the strut housing.

[kern417]

Originally Posted by 5mall5nail5

Think about it - if your caliper, as is, could work with a disc that sticks 15mm further into it then your car would currently have brake pads that overhang the rotor and clamp onto nothing.

I am really not sure why people are confused about the 340/370/380mm rotor thing. The 340mm calipers mount 15mm inward of a 370/380mm caliper. The reason a 370mm caliper can work on 380mm rotors is because 380mm = M3 upright which have longer mounting ears, so they space the 370mm caliper out 10mm by means of where they attach to the strut housing.

The width of the contact patch between the disk and the calipers are the same though. All 340mm/370mm/380mm calipers use the same brake pads.

[5mall5nail5]

Originally Posted by kern417

The width of the contact patch between the disk and the calipers are the same though. All 340mm/370mm/380mm calipers use the same brake pads.

Yes that is correct, however moving the pad further from the center of the disc makes for a great amount of torque even though the friction surfaces are the same.

[Genieman]

Originally Posted by 5mall5nail5

Yes that is correct, however moving the pad further from the center of the disc makes for a great amount of torque even though the friction surfaces are the same.

The benefit of increased torque from a larger diameter rotor is probably completely offset by higher speed of disc rotation at larger diameter contact point, coupled with heavier rotational mass of larger rotor being harder to stop. My personal preference would be instead of trying to switch from 340 to 370, would be to find a lighter 340 rotor and better brake pads.

[johnung]

Switching the fronts from 340 to 370 is negligible in terms of braking improvement. It's more for show by using the larger 370mm rotor in front. They both use 4-piston Brembo calipers.
(Note that either the 370mm front rotor or the 345mm rear rotor means an 18" road wheel is required. So if you have 17" wheels, you can't upgrade to either of these unless you are upgrading the size of your road wheels at the same time.)

The brake mod that will give the biggest performance gain is if you switch out the rear 1-piston calipers for Brembo 2-piston calipers on 345x24 rotors. Instead of nose diving during hard braking the car squats on all four wheels very controllably even if you are standing on the brake pedal. It is a huge difference.

Add some stainless steel brake lines (about $106/ set of 4) and Hawk HPS 5.0 pads (about $115 for rears) and the overall improvement from stock braking is dramatic. I've seen the rear (blue) calipers with the 345x24 rotors going for roughly $600 used. Toss any OEM pads that come with them for the Hawk 5.0's. You can change the color of your calipers right on the car by brushing them with G2 Caliper Paint (about $42 at TireRack). (G2USA.com) It's a two part epoxy type coating that evens out when applied at the right temperature range so it looks like it was sprayed on.

Doing these all together is a great brake system modification in terms of bang for the buck! Hope this helps!

[cfm56d7b]

@d1mitrov, could you share more details about your goals? Better visual appearance of brakes? More braking power? Will you take your car to the track?

[johnung]

Originally Posted by Encanto

The 370mm OEM front rotor fits in your current 4-piston front OEM calipers.

Those 4-piston calipers are exactly the same as the M Sport blue 4-piston calipers except the paint.

Please read post#2. The 370mm rotors will NOT work with the gray calipers that came with the 340mm rotors. Those calipers are slightly different. The front calipers that will work with the 370mm rotors are painted either blue, red, yellow or orange.

BMW really confuses things in terms of brakes by using similar terms like "M Sport" to mean different things depending on which model car and whether you are talking about calipers, rotors or pads, or various packages.

Turner Motorsport has some great articles to explain this stuff on their website but they are buried several levels deep and difficult to locate. Google "Turner Motorsports Brake Package Differences" and it will list an article for the 328i and another for the 335i. These are great resources!

[Encanto]

Stand corrected: https://f30.bimmerpost.com/forums/sh...90&postcount=9

Originally Posted by johnung

Please read post#2. The 370mm rotors will NOT work with the gray calipers that came with the 340mm rotors. Those calipers are slightly different. The front calipers that will work with the 370mm rotors are painted either blue, red, yellow or orange.

BMW really confuses things in terms of brakes by using similar terms like "M Sport" to mean different things depending on which model car and whether you are talking about calipers, rotors or pads, or various packages.

Turner Motorsport has some great articles to explain this stuff on their website but they are buried several levels deep and difficult to locate. Google "Turner Motorsports Brake Package Differences" and it will list an article for the 328i and another for the 335i. These are great resources!

[d1mitrov]

Originally Posted by cfm56d7b

@d1mitrov, could you share more details about your goals? Better visual appearance of brakes? More braking power? Will you take your car to the track?

so i was simply going for visual as i like how the bigger rotor fills out the wheel. I was trying to see if the 370mm rotor will fit my current gray non msport calipers. Im not looking to spend $1000+ for the calipers at the moment. I might end up going with these tho they look
https://www.ecstuning.com/b-ecs-part...0/014586ecskt/

[cfm56d7b]

Originally Posted by d1mitrov

so i was simply going for visual as i like how the bigger rotor fills out the wheel. I was trying to see if the 370mm rotor will fit my current gray non msport calipers. Im not looking to spend $1000+ for the calipers at the moment. I might end up going with these tho they look
https://www.ecstuning.com/b-ecs-part...0/014586ecskt/

Bigger rotor without bigger calipers may not be visually perfect. Then again, alternatives can get quite expensive.

If you are interested in learning more, both Brembo and AP Racing make exceptional brakes which provide more braking power than one may ever need.

[johnung]

Originally Posted by d1mitrov

so i was simply going for visual as i like how the bigger rotor fills out the wheel. I was trying to see if the 370mm rotor will fit my current gray non msport calipers. Im not looking to spend $1000+ for the calipers at the moment. I might end up going with these tho they look
https://www.ecstuning.com/b-ecs-part...0/014586ecskt/

Originally Posted by d1mitrov

so i was simply going for visual as i like how the bigger rotor fills out the wheel. I was trying to see if the 370mm rotor will fit my current gray non msport calipers. Im not looking to spend $1000+ for the calipers at the moment. I might end up going with these tho they look
https://www.ecstuning.com/b-ecs-part...0/014586ecskt/

Those rotors do look nice. I was considering them too. I gagged on the price though. I'm skeptical of the weight savings since I saw a weight for the stock rotors that would make the savings roughly half of what they claim.

StopTech has some black hat drilled rotors for half the price. I also recently learned about adamsrotors and r1concepts. Check out rotors on their websites.

If you want to make your brakes "pop", change the color. Check out G2USA.com for their caliper paint. (TireRack $42) it's a 2-part epoxy type paint that brushes on with the car on jack stands. Paint levels out and looks like it was sprayed on. I painted mine black to match the car, added Brembo decals and even painted stock rotor hats silver to get rid of rusty look. Would be easy to change rotor hat color if you wanted a certain look.

The photo is of your same stock front gray caliper painted in G2 Black with a white Brembo decal. (My second color choice was red but I have a stealth theme going with this particular car.) The side of the rotor hat that you see (not top where it is against the road wheel) is painted G2 Silver so it always looks brand new now.

[d1mitrov]

That does look pretty good. Im having a local shop paint all four for $150 tho. I actually got 4 rotors for $400 with pads and sensors from cquence brakes. Theyll look like this

[kern417]

I agree you don't do this upgrade if you want more braking power. Brake pads will be a far better option that will stop better and handle the increased heat better.

I remember in my Volkswagen days, SPM experimented by selling a bbk spacer kit. Basically it spaced out the OEM 1-Piston calipers to accept a larger rotor. They had to stop selling it shortly after due to a lot of fuss about it not really increasing performance.