[TacosRule!]

Originally Posted by blau3er

The 4 piston caliper pads are tiny in comparison to the 6 pot pads. Its worth noting that the F95 X5M is paired with the same sized piston rear calipers as F97 X3M.

The only variation being that it uses a 380mm rear disc, and as such has a different carrier to suit the larger disc.

The F95 X5M rear calipers / discs bolt onto G2x G3x G1x etc rear hubs - so I see no reason why it won’t be the same story on F97.

This is my reasoning as well.

[TacosRule!]

Originally Posted by Bimma360

Yeah but they aren't so its a moot point.

What are the dimensions of both?

[Bimma360]

Originally Posted by TacosRule!

What are the dimensions of both?

https://x3.xbimmers.com/forums/showthread.php?t=2072977

[TacosRule!]

Originally Posted by Bimma360

https://x3.xbimmers.com/forums/showthread.php?t=2072977

Your table does not show dimensions for the pads.

[Bimma360]

Originally Posted by TacosRule!

Your table does not show dimensions for the pads.

It shows pad height, which is the only relevant measure relating to brake bias.

[95wildtt]

Originally Posted by TacosRule!

Your table does not show dimensions for the pads.

https://x3.xbimmers.com/forums/showp...72&postcount=1

[TacosRule!]

These are the numbers directly from Brembo:

F97

Width 125mm
Thickness 20mm
Height 117mm
WVA number 22392


F95
Width 185mm
Thickness 20mm
Height 106mm
WVA number 22441

wider as expected to fit 2 more pistons, but surprised to see they're 11mm smaller in height.

[TacosRule!]

So, is there a consensus we can all reach?

1) The stock brakes suck
2) an upgrade to the front brakes will be an improvement
3) upgrading fronts to 6 piston will increase rear bias, although marginally

Is the upgrade worth it then? I just measured my pads and I'm at 6mm, the dealer wont replace them until I trigger the light, even though they're squeaky/"grindy" as hell and have deep groves in the rotors.

The UC+ expires at the start of september, I doubt I'll be able to grind down 3mm in 2 months, which means I'm paying for brakes out of pocket, so may as well upgrade.

[Bimma360]

Originally Posted by TacosRule!

These are the numbers directly from Brembo:

F97

Width 125mm
Thickness 20mm
Height 117mm
WVA number 22392


F95
Width 185mm
Thickness 20mm
Height 106mm
WVA number 22441

wider as expected to fit 2 more pistons, but surprised to see they're 11mm smaller in height.

Usually manufactures give the height measurement including the ears of the bad which is worthless for our purposes. You want to find the diagram if it exists. And even then the measurement might include the ears. You need the pad height of the friction material itself. If I have it at 90mm for both it’s probably 90mm then. Also if the rotors for both cars have the same swept area then the pad heights will also be the same.

Come to think of it I am pretty sure the OP shows the f97 pad height and I think Kevin’s thread shows the pad height for the 6 piston.

[TacosRule!]

Originally Posted by Bimma360

Usually manufactures give the height measurement including the ears of the bad which is worthless for our purposes. You want to find the diagram if it exists. And even then the measurement might include the ears. You need the pad height of the friction material itself. If I have it at 90mm for both it’s probably 90mm then. Also if the rotors for both cars have the same swept area then the pad heights will also be the same.

Come to think of it I am pretty sure the OP shows the f97 pad height and I think Kevin’s thread shows the pad height for the 6 piston.

Here's F97
https://www.bremboparts.com/europe/e...e/pad/P_06_106


And F95
https://www.bremboparts.com/europe/e...e/pad/P_06_100

[Kevin_The_Clean1]

The last time I spoke to some of the quote on quote "experts" here I got chastised by a small few & raked over the coals about this not being a true upgrade. LOL But I don't really modify my cars to make others happy. Therefore, feel free to say whatever you need to about this & do all the deep calculations on paper you feel is necessary.

At the end of the day, I've never installed a single component on my M -cars that made them worse performers or worth less. My F97 X3 MC rides on DINAN springs + the corresponding bump stop kit, has been aligned to a razors edge by one of the nation's finest highly specialized shops (they actually test new machines & equipment for the TIRE - RACK), has the DINAN mono-ball kit, has upgraded wider PS4S rubber & has these X5 M (direct plug-n-play) OEM 6-piston Brembos up front to stop the mad machine.

It was a bonkers sleeper before & now it's even better. There's a reason why people with 700-750 HP+ X3M's in other countries that track (not drag race) their X3 M's have this brake setup & other similar modifications. It allows them to drive the SAV harder then ever before while maintaining all the creature comforts of a luxury auto on the road.

With brake pads close to double in size, it's no wonder the amount of friction & bite is increased. Twice the surface area is a substantial gain. You can do all the calculations you need to on paper, do hours of HW & discuss this subject matter in nauseum. Many of those who continue to critique the 6-piston units & yet continue to complain about the 4-piston units at the same time make me laugh. I too want to be extra convinced before I buy things. But some purchases are a clear no brainer in my book. Not only are these 6-piston calipers more rigid (a true mono-block) instead of the two clam-shells bolted together, but they're also 1-2 pound lighter as well. I for one love them & wouldn't ever want to go back.





https://x3.xbimmers.com/forums/showt...+brake+upgrade

[Bimma360]

Originally Posted by TacosRule!

So, is there a consensus we can all reach?

1) The stock brakes suck
2) an upgrade to the front brakes will be an improvement
3) upgrading fronts to 6 piston will increase rear bias, although marginally

Is the upgrade worth it then? I just measured my pads and I'm at 6mm, the dealer wont replace them until I trigger the light, even though they're squeaky/"grindy" as hell and have deep groves in the rotors.

The UC+ expires at the start of september, I doubt I'll be able to grind down 3mm in 2 months, which means I'm paying for brakes out of pocket, so may as well upgrade.

I am just going to say the following and leave it at that. Obviously, everyone can do what they want with their cars and try to justify it however helps them sleep at night.

1) The stock brakes suck - They don't. Not for the street and for the vast majority of people. If you cook your pads regularly, yes they suck. C/D tested the X3M to have the same stopping distance from 70-0 as the M3. You won't out stop an M3 by putting on its front calipers. No the stock brakes are not ideal in ultimate terms.

2) an upgrade to the front brakes will be an improvement - my definition of an upgrade is not gaining something at the expense of potentially making something else worse.

3) upgrading fronts to 6 piston will increase rear bias, although marginally - I don't think anyone in their right mind will call needing a 412mm rotor to restore factory bias as marginal.

My opinion on all of this, removing track cars from the equation, is if you are going to do something do it right. Find the right 405mm rotor from Brembo's BBK catalogue, get custom brackets made, and run the 6 piston calipers. At least then, perhaps the bias may be marginal.

[Bimma360]

Originally Posted by TacosRule!

Here's F97
https://www.bremboparts.com/europe/e...e/pad/P_06_106


And F95
https://www.bremboparts.com/europe/e...e/pad/P_06_100

The diagram on the F97 in the links shows the pad height at 88mm. The diagram includes the F95 includes the ears, so like I said.. useless.

[Bimma360]

Originally Posted by Kevin_The_Clean1

With brake pads close to double in size, it's no wonder the amount of friction & bite is increased.

Imagine, if the sensation you are feeling and describing as the above was a result of decreased pedal travel due to the smaller pistons in the 6 piston calipers.

[TacosRule!]

Originally Posted by Kevin_The_Clean1

The last time I spoke to some of the quote on quote "experts" here I got chastised by a small few & raked over the coals about this not being a true upgrade. LOL But I don't really modify my cars to make others happy. Therefore, feel free to say whatever you need to about this & do all the deep calculations on paper you feel is necessary.

At the end of the day, I've never installed a single component on my M -cars that made them worse performers or worth less. My F97 X3 MC rides on DINAN springs + the corresponding bump stop kit, has been aligned to a razors edge by one of the nation's finest highly specialized shops (they actually test new machines & equipment for the TIRE - RACK), has the DINAN mono-ball kit, has upgraded wider PS4S rubber & has these X5 M (direct plug-n-play) OEM 6-piston Brembos up front to stop the mad machine.

It was a bonkers sleeper before & now it's even better. There's a reason why people with 700-750 HP+ X3M's in other countries that track (not drag race) their X3 M's have this brake setup & other similar modifications. It allows them to drive the SAV harder then ever before while maintaining all the creature comforts of a luxury auto on the road.

With brake pads close to double in size, it's no wonder the amount of friction & bite is increased. Twice the surface area is a substantial gain. You can do all the calculations you need to on paper, do hours of HW & discuss this subject matter in nauseum. Many of those who continue to critique the 6-piston units & yet continue to complain about the 4-piston units at the same time make me laugh. I too want to be extra convinced before I buy things. But some purchases are a clear no brainer in my book. Not only are these 6-piston calipers more rigid (a true mono-block) instead of the two clam-shells bolted together, but they're also 1-2 pound lighter as well. I for one love them & wouldn't ever want to go back.




https://x3.xbimmers.com/forums/showt...+brake+upgrade

I know, I was trying to remain neutral and diplomatic.

[TacosRule!]

Originally Posted by Bimma360

The diagram on the F97 in the links shows the pad height at 88mm. The diagram includes the F95 includes the ears, so like I said.. useless.

[Bimma360]

Originally Posted by TacosRule!

haha its ok I forgive you.

[spucktacular]

We could totally timeshare that! 🍹

If they sold these for 5-8k from the factory, I'd be tempted. Sometimes, I wonder if the brake fading is just the drilled holes catching the edge of the pads. Cross-drilled rotors, am I right? But after a few spirited drives, I think it's more about the pads getting too hot and breaking down over the holes. So, it’s probably a mix of old pads/rotors and the smaller thermal limits of 4-pot pads versus 6-pot.

You're spot on about the rear calipers, especially with how hard they work on AWD cars sliding around. I get that it's because of the electric parking brake, but is it really that hard to design a 2/4 pot rear unit with an electric actuator? Mercedes has an electric drum parking brake in the hub, leaving the calipers to do their thing. Exotics go all out with a second rear caliper just for parking.

But seriously, are the AS4S tires as sweet as they say when driven right? I'm itching to buy a set of 265/40/21 and 275/40/21 AS4Ss for the factory 21" wheels. With 4.2" of sidewall up front and 4.3" in the rear, and a 500 tread-wear rating... I'm so ready for this!

Originally Posted by TacosRule!

Good post, let me clarify a couple of things.


1) the suspension is rough, yes. You want a suspension that breaks your spine, ride on a WRX STI with lowering OE rally suspension. Good luck.
2) I got lucky that I have PS4AS from factory (CPO car), most cars I have seen drop with run flats, those cars ride like craaaaaaap.
3) yes, 4 pistons up front is pathetic. I'd like to add single piston rear is also pathetic
4) Wanna go half and half on this?

https://www.ebay.com/itm/295048804668

[pyo]

In my experience, our SUVs eat thru rear pads before the fronts. I went to a 2 day HPDE at Summit Point on factory pads with 25k+ miles on them. 4 x 20-25min sessions per day, and rear sensors on my 7th ending my time on track. When I got them replaced, my fronts still measured in at 7mm/6mm (outer/inner).

The BMW expert on site told me the rears are way more active at stopping the x3m, pulsating to help with nose dive, etc. (he gets flown out by BMW to test on tracks).

With that all said, I do want to do this upgrade in the future...

[spucktacular]

From first hand experience, I've stopped with ABSOLUTE authority from speeds I shouldn't put in writing! Honestly, I think most would be shocked how hard it actually reacts when you jam on the brakes with maximum pressure. Its shocking and extremely violent... but it only does it, 2-3 times MAX (from 100+mph).. then it starts to moan, and fade, and leave streaks of melted pad material on the disks... etc etc..

The next time you try to have fun, it seems to do it sooner, and as soon as the pads are half way worn.. it does that even stopping with authority from 70mph... just always feels like the brakes are unmatched for the power output and curb weight.

For the record, I've never taken my car to a track. I just enjoy it.. mostly in comfort with occasional sport engine modes

Originally Posted by Potatohead-M2

The braking performance is more than adequate for 98% of drivers. The only real advantage to larger calipers is better heat dissipation for track use. In terms of actual stopping distance there is no real world difference until heat starts to become an issue which won't happen on the street.

I'd love to be able to hear the ins and outs from the engineers as to why certain decisions are made. I'm not convinced it's always about money.

[spucktacular]

So according to F97/F98 technical training docs for our cars (attached), we have a "ATC13" transfer case unit, that is brought over from the G12 (2015+ 7 series). It uses a multiplate clutch to transfer 0:100, or 100:0 between the front-rear axles. When open, the rear axle receives 100% of the torque (hence the MDM or 2WD mode on the F90). I then went deeper and dug up the drivetrain technical manuals on the G12, which does indeed better describe the transfer case unit. It does also mention that the ride is mostly RWD until the front is in demand, but not sure how that fits into the standard and MDM modes.

However, it would appear that mechanically there is no HARD link between front and rear axles, and by design this multiplate clutch transfer case, is designed to allow for different rotational speeds of front and rear axles.. WHICH means.. the 1% rule between front/rear axles.. isn't really a concern?!? Thermal is obviously an issue when the clutch has to handle the offset.. does it make much of a diff between 0.7% <> 1.1% <> 1.4%

I don't claim to know anything here.. just following logic and docs, but it doesn't seem to be a real issue in how the transfer case is designed.. (and it has its own cooling setup no? or is that just the transmission and rear diff?)

Originally Posted by TacosRule!

Almost all M cars have this setup, the M5 has 275/35--285/35 20s, so from factory they have a +1.1% difference in tire diameter. Mine came 255/45-265/45 from factory, that's +1.4%. which is of course bigger than the 1% everyone here professes to adhere to if you don't want your diff to blow up.

So not sure we really have to observe > +/-1% difference.

[Mnfamilyguy2020]

This has become a fairly hot issue that seems to be colored by quite a bit of conformation bias, if you want to make a change/upgrade to your brakes, that's great! Do it!

But, now it looks like someone has flagged Bima360 as propagating SPAM which is not so great in my humble opinion. I have nothing to do w/Bima360 and I see absolutely NO spam coming from him/her. I've clicked "looks ok" on all the pink dialogue boxes that are now attached to his posts....