[///Malobus]

5.15

Can you give more detailed information about the parameters and other differences in the braking systems?
Does anyone know the part numbers for the larger calipers (although in the video I did not see any differences in the calipers, but the disks are clearly larger) and discs?

[Perets]

Originally Posted by ///Malobus

5.15

Can you give more detailed information about the parameters and other differences in the braking systems?
Does anyone know the part numbers for the larger calipers (although in the video I did not see any differences in the calipers, but the disks are clearly larger) and discs?

I have 230 with handling package. And front disks are around 350mm, rear 355mm.

[Dinosoar]

Ha, perfect. I've been meaning to pull off rotors and measure, now I don't need to. Thanks (again)! I am surprised the rears are bigger...hell, I'd be surprised if even the same. I think that'd be BMW taking the staggered tire set up just too far, IMO.

[Perets]

Originally Posted by Dinosoar

Ha, perfect. I've been meaning to pull off rotors and measure, now I don't need to. Thanks (again)! I am surprised the rears are bigger...hell, I'd be surprised if even the same. I think that'd be BMW taking the staggered tire set up just too far, IMO.

By honest, I’m not sure about rears, I didn’t take them off. They’re about 350mm +/-5mm. Front ones - 348mm.

[ggggbmw]

Bigger discs in the rear are not that surprising. On the F22, the standard fronts are 340mm, and the rears are 345mm. The rears are a bit thinner (24mm vs 30mm front), so can handle less heat.

The non-stock 'big brake' M-Performance aftermarket option (not what came on the M235/M240), were 370mm. The 4-piston caliper for the M-Perf brake is the same size as the standard brake, but the mounting ears are offset to accommodate the bigger rotor. They could be doing a similar thing with the different rotor sizes on the G42.

I don't have any idea of the actual size on the G42 though. Just starting to monitor these forums for a likely upgrade of my F22.

[Dinosoar]

In my mind, only a 911, maybe mid-engine cars, should have rears that are of a same size as the fronts...but again, I think tire set ups factor in. 911s have huge rear tires compared to their fronts, and they stay flatter under braking too, give that rear axle more braking grip than is usual. The only think I can think of keeping that front smaller is for un-sprung weight. In all front engine cars, and vehicles in general, those fronts do most of the work stopping the car.

I am curious why BMW would put rears on that are bigger in diameter than the fronts. In any case, I ain't changing it, just want to understand it.

[Perets]

Bigger diameter doesn't mean more braking power. And don't forget about dsc, which works by brakes.

[jbazz]

Originally Posted by Dinosoar

I am curious why BMW would put rears on that are bigger in diameter than the fronts. In any case, I ain't changing it, just want to understand it.

Like ggggbmw said it is not that surprising. I have larger diameter rear rotors on my Miata. However there are many factors in brake design besides diameter (rotor mass, thickness, calipers, pads material, master cylinder valving, expected operating temperature range etc. Brakes convert kinetic energy into thermal energy and must dissipate that energy.
Regardless of where the engine is located, even on a motorcycle, weight always transfers to the front on braking, and the fronts are always designed to dissipate more heat. You will probably see that the front rotors, though smaller in diameter are double the thickness and have more mass, to manage the heat and not warp. The fronts have to also deal with more clamping force (friction) from the more powerful calipers. The master cylinder will be be designed to divert more force to the fronts as well. Not sure if that is helpful to you, but its not uncommon at all. I am positive the front rotors are heavier than the rears and that the calipers are also much more powerful. The rear is wider, but thinner as well.

[Dinosoar]

Originally Posted by jbazz

Like ggggbmw said it is not that surprising. I have larger diameter rear rotors on my Miata. However there are many factors in brake design besides diameter (rotor mass, thickness, calipers, pads material, master cylinder valving, expected operating temperature range etc. Brakes convert kinetic energy into thermal energy and must dissipate that energy.
Regardless of where the engine is located, even on a motorcycle, weight always transfers to the front on braking, and the fronts are always designed to dissipate more heat. You will probably see that the front rotors, though smaller in diameter are double the thickness and have more mass, to manage the heat and not warp. The fronts have to also deal with more clamping force (friction) from the more powerful calipers. The master cylinder will be be designed to divert more force to the fronts as well. Not sure if that is helpful to you, but its not uncommon at all. I am positive the front rotors are heavier than the rears and that the calipers are also much more powerful. The rear is wider, but thinner as well.

It's a fine explanation...totally appreciate it. I do disagree that same/bigger rear disks is not uncommon (or common). I think the vast majority of vehicles, including many sports cars have larger rotors up front. Nonetheless, I love new information and ideas, so thanks again.

I the case of our BMWs, I can see the extra force is done via stronger caliper, and the wider rotor handles heat, but a larger diameter is avoided to resist handling liabilities of that un-sprung weight brings. And, to your points, then, the fronts remain much stronger than the back all the same.

[Fidiman]

In the end, do we have any idea of the stock discs diameters versus the "sport" version (ticked as an option or in th ZTK package) ? Same question for the calipers.

I hope BMW doesn't charge us hundred of bucks only for the colour

[C00KIE M0NSTER]

Since the G42 shares the same chassis as the G20 does anyone know if the new M3 and M4 front brakes will bolt on to the G42 hubs?

[conradb58]

Originally Posted by Fidiman

In the end, do we have any idea of the stock discs diameters versus the "sport" version (ticked as an option or in th ZTK package) ? Same question for the calipers.

I hope BMW doesn't charge us hundred of bucks only for the colour

ZTK Package Rotors F 374x36 & R 345x24

[hutchsoclutch]

So does the M240i without ZTK have slightly smaller front rotors? Maybe 355mm? I saw one thread debating whether the calipers themselves were bigger but it may literally just be the mounting point idk…

[danallxt]

Originally Posted by hutchsoclutch

So does the M240i without ZTK have slightly smaller front rotors? Maybe 355mm? I saw one thread debating whether the calipers themselves were bigger but it may literally just be the mounting point idk…

From what i can figure from other posts and following this topic in various posts for months, yes the M240i w/o ZTK option has 348 front and 355mm rear rotors. So yes slightly smaller front rotors. On the other hand i have never had it confirmed if the calipers themselves were larger on the ZTK option...i suspect not but have never seen it confirmed. A number of folks have asked this but i have never seen it positively confirmed. Looking at picts are not a reliable means of determining.

[MPR]

The ZTK rotors and calipers appear larger.

[hutchsoclutch]

That looks pretty definitive to me. The inside edge of the caliper on the ZTK pack looks very straight whereas the standard caliper bows towards the hub and back out towards the ends of the caliper. Otherwise they look like scale versions of each other and very similar in overall design.

[Brett_C_F30_G42]

Originally Posted by MPR

The ZTK rotors and calipers appear larger.

They are bigger. Had a sales advisor tell me straight up. They're better for continued braking compared to the smaller M sport ones but if you want the best brakes get the M Performance Brake Upgrade Kit from BMW. Those are great.

[MPR]

For daily driver people like me I think m perf would be overkill. I'm happy with the slightly larger setup that comes with ZTK.

[conradb58]

I just received my 240 with the "ZTK" package would you like to see anything that will help you ?

[MPR]

If you can remove a front wheel and measure the caliper, that would be ideal. Or measure it somehow with the wheel on the car. Maybe slide a tape measure in and measure tip to tip and snap a picture. We can get someone with a non ZTK to do the same

Thanks for offering!

[ryo-]

so the standard brakes are "M Sport" and the ZTK package is just a slightly larger "M Sport" front brakes? then there is the "M Performance" BBK? tbh, the names are so similar it gets confusing lol

[MPR]

That's how I understand it. Curious to what the differences are between large m sport (ZTK) and m performance.