[BulkBen]

Hi Folks,

I hope this is helpful for anyone considering upgrading their brakes, as I am just finishing off this very straightforward and economical conversion. I'm amazed its not more common, given it should deliver similar performance to the GT 8 piston swap, while being 1/4 of the price.

As an intro, I'm a bit of a track junkie, after seeing how well the X3m went after a custom E70 tune (10.5 sec 1/4 mile @ 131mph), I was very keen to take it to the circuit.

While a lot of fun, it was obvious that brakes are a huge limiting factor. Before heading to the track I changed my fluid to Castrol SRF and upgraded my pads to EBC Blue. if you aren't familiar with these in the U.S, they are a decent street / track pad, designed to handle a bit of abuse.

Regardless of these mods, I baked my brakes after about 10 minutes. 700hp and 2000kg does take its toll.
I did manage to keep going through the day doing quick sprints, 1-2 warm up laps followed by 2 laps at full speed, then a full cool down.

Not the easiest way to get a lap time in, but the best I could manage giving the circumstances.

Anyway, I'm due out again in 2 weeks and wanted to ensure my brakes were up to the task. What's the point in dusting young guys in sports cars if you can only handle a few laps at speed?

I looked into the GT 8 piston upgrade, but it seemed very costly. It provides a bigger disk (which is usually good) but it does limit you to a 21 inch wheel, not ideal for many. If you want to read more about that, a few members discuss it here:
https://x3.xbimmers.com/forums/showthread.php?t=1723703

Prices here:
https://www.vividracing.com/brembo-4...153125573.html

It's clear when looking at the stock X3M brakes the discs aren't the issue, it is the tiny caliper / pad combination - which at first glance looks decent.
A 60% increase in swept area from M5 to X3M pads is absolutely massive.

You will see pics below of both pad specs, but please note the actual contact area for each is as follows. See pics of measuring tape of stock X3M pads.

Stock X3M: 92x90mm = 8280mm2

Stock M5: 180x75mm = 13,500mm2

The M5 calipers are 100% bolt on using standard X3m discs, you just have to make sure you get calipers with brackets.

This is essential as the X3M brakes have different brackets, so you can't swap them over.

I paid about $1300 USD for my M5 calipers which had done 2000km, so virtually brand new pads. Best of all they come in BMW blue, matching the rears, so no need to respray anything (which is necessary with the GT kit).

On top of that, I have also made up some brake ducts using 2.5 inch high temp silicone hose. I have added some brackets (which can be sprayed black). At the front they just poke through the standard bumper vents.

They connect to the standard brake heat shields with hose clamps, with holes drilled there for 2.5 inch flanges.

I will be trimming the inside edge where these hoses come out in the wheel well to avoid them fouling the wheels on lock. Regardless, this isn't much of an issue as I plan to remove them for street use.

I have located some track compound pads to suit these and the stock rear calipers, but if push comes to shove I'll try them out first time with stock pads.

I'll update the post once that day happens, I'm heading out this time with Cup 2 tyres (275/35 21 all round) as well as the brake mods so expect to knock a bit off my lap times.

[acce98]

Originally Posted by BulkBen

Hi Folks,

I hope this is helpful for anyone considering upgrading their brakes, as I am just finishing off this very straightforward and economical conversion. I'm amazed its not more common, given it should deliver similar performance to the GT 8 piston swap, while being 1/4 of the price.

As an intro, I'm a bit of a track junkie, after seeing how well the X3m went after a custom E70 tune (10.5 sec 1/4 mile @ 131mph), I was very keen to take it to the circuit.

While a lot of fun, it was obvious that brakes are a huge limiting factor. Before heading to the track I changed my fluid to Castrol SRF and upgraded my pads to EBC Blue. if you aren't familiar with these in the U.S, they are a decent street / track pad, designed to handle a bit of abuse.

Regardless of these mods, I baked my brakes after about 10 minutes. 700hp and 2000kg does take its toll.
I did manage to keep going through the day doing quick sprints, 1-2 warm up laps followed by 2 laps at full speed, then a full cool down.

Not the easiest way to get a lap time in, but the best I could manage giving the circumstances.

Anyway, I'm due out again in 2 weeks and wanted to ensure my brakes were up to the task. What's the point in dusting young guys in sports cars if you can only handle a few laps at speed?

I looked into the GT 8 piston upgrade, but it seemed very costly. It provides a bigger disk (which is usually good) but it does limit you to a 21 inch wheel, not ideal for many. If you want to read more about that, a few members discuss it here:
https://x3.xbimmers.com/forums/showthread.php?t=1723703

Prices here:
https://www.vividracing.com/brembo-4...153125573.html

It's clear when looking at the stock X3M brakes the discs aren't the issue, it is the tiny caliper / pad combination - which at first glance looks decent.
A 60% increase in swept area from M5 to X3M pads is absolutely massive.

You will see pics below of both pad specs, but please note the actual contact area for each is as follows. See pics of measuring tape of stock X3M pads.

Stock X3M: 92x90mm = 8280mm2

Stock M5: 180x75mm = 13,500mm2

The M5 calipers are 100% bolt on using standard X3m discs, you just have to make sure you get calipers with brackets.

This is essential as the X3M brakes have different brackets, so you can't swap them over.

I paid about $1300 USD for my M5 calipers which had done 2000km, so virtually brand new pads. Best of all they come in BMW blue, matching the rears, so no need to respray anything (which is necessary with the GT kit).

On top of that, I have also made up some brake ducts using 2.5 inch high temp silicone hose. I have added some brackets (which can be sprayed black). At the front they just poke through the standard bumper vents.

They connect to the standard brake heat shields with hose clamps, with holes drilled there for 2.5 inch flanges.

I will be trimming the inside edge where these hoses come out in the wheel well to avoid them fouling the wheels on lock. Regardless, this isn't much of an issue as I plan to remove them for street use.

I have located some track compound pads to suit these and the stock rear calipers, but if push comes to shove I'll try them out first time with stock pads.

I'll update the post once that day happens, I'm heading out this time with Cup 2 tyres (275/35 21 all round) as well as the brake mods so expect to knock a bit off my lap times.

I hope you can enjoy them .. Ciao Silvano IT

[MaxGainz]

Nice write-up! Thanks. Pretty damn cheap upgrade

[Ramlimited4500]

I’m assuming they come off a pretty new m5. The carbon disc won’t fit with the m5 calipers 🧐

[tarmactrr]

great job. I believe that's also the same caliper on the X5M as well. Honestly can't believe they didn't just use the M5 caliper on the x3m.

[jwong1024]

Nice write up, i was wondering if there was a cheap oem upgrade for brakes. I am due pretty soon and would love to potentially do this.

Question though for OP. Did this improve your stopping power that significantly? I have to admit this x3mc is more responsive than my macan i swapped out for.

[Kevin_The_Clean1]

This is awesome news & can't wait to do this mod when I have the funds to purchase the style 892 M wheels from the LCI too.

Do you happen to have a part number for those necessary brackets?

[BulkBen]

Hi Guys,

Just answering a few bulk questions here.

I will know in 10 days how much better they work, as I'm back out to the track then. I'm not braking hard enough on the street to notice, but will be on the same track again soon.
Unfortunately I may be on stock pads if my new track pads haven't arrived, but braking should be fine until they get too hot. With any luck the ducting will delay the point at which they overheat too.

Re brackets, I have discussed this with a guy via PM too. Real OEM do not show a seperate part number for the discs and brackets. This leads me to believe BMW may not supply them separately.

I can't say it enough DO NOT buy calipers without brackets thinking you can pick them up later, it is false economy. If buying used, wait for an advert which clearly shows the brackets.
The bracket is small and simple, but having to source them separately or fab them would be a real pain.

There's a few merchants on Ebay selling front and rear calipers, unfortunately I have no experience fitting rear M5 calipers, so can't say whether its also bolt on.

Finally, yep I think the M5 and X5m use the same calipers, so another potential source there.

[MRichmond]

The main limiting factor in stopping power on track is not the stock pistons or discs on an M car, which already are fairly stout. The main limiting factor is tires. If you ever go to an R-compound tire, the stopping power is improved drastically. A "big brake" kit may help avoid fade after a number of laps, but it is unlikely to make nearly the difference that the tire compound will.

[RoWoX3M]

Originally Posted by BulkBen

Hi Guys,

Just answering a few bulk questions here.

I will know in 10 days how much better they work, as I'm back out to the track then. I'm not braking hard enough on the street to notice, but will be on the same track again soon.
Unfortunately I may be on stock pads if my new track pads haven't arrived, but braking should be fine until they get too hot. With any luck the ducting will delay the point at which they overheat too.

Re brackets, I have discussed this with a guy via PM too. Real OEM do not show a seperate part number for the discs and brackets. This leads me to believe BMW may not supply them separately.

I can't say it enough DO NOT buy calipers without brackets thinking you can pick them up later, it is false economy. If buying used, wait for an advert which clearly shows the brackets.
The bracket is small and simple, but having to source them separately or fab them would be a real pain.

There's a few merchants on Ebay selling front and rear calipers, unfortunately I have no experience fitting rear M5 calipers, so can't say whether its also bolt on.

Finally, yep I think the M5 and X5m use the same calipers, so another potential source there.

So the "brackets" are apparently called "adapters" and there's aftermarket availability. Currently not many used f90 m5 front calipers available but the ones that are don't have these adapters for whatever reason.

https://tro-nik.com/product/bmw-g30-...90-all-brakes/

[BulkBen]

Originally Posted by MRichmond

The main limiting factor in stopping power on track is not the stock pistons or discs on an M car, which already are fairly stout. The main limiting factor is tires. If you ever go to an R-compound tire, the stopping power is improved drastically. A "big brake" kit may help avoid fade after a number of laps, but it is unlikely to make nearly the difference that the tire compound will.

I'm moving from a 265 4S to a 275 Cup 2 at the same time, so hopefully pick up a decent gain there.

Regardless having driven cars with road tyres on the track before I was quite alarmed by the X3M's brakes. Maybe it was the sheer weight of the car, and I know I am pointing out the obvious here, but you really feel its weight and size under brakes.

[Kevin_The_Clean1]

Another quick note is that the piston sizes in these M5 calipers were designed to work with the master cylinder in the V8 powered cars. So there may be more pedal effort when this M5 caliper is used on the X3M.

[BulkBen]

Hi Folks,

For people who are interested in this thread I have an update from my second track day, first one after the M5 calipers went on.

Unfortunately I was not able to secure track pads before I headed out, which worried me quite a bit.

I was going from stock calipers and semi track pads (EBC blue) the first time out, to M5 calipers with stock pads, albeit with the benefit of the brake ducts on the second track mission. Both times I ran SRF fluid.

With the stock calipers and track pads the brakes were smoking early, so I really didn't know what to expect this time.

The good news is that the results were amazing. The car has gone from the brakes feeling very marginal and giving up very quickly (even with better pads) to a car which pulls up extremely well, every time. i had total confidence in them and lapped very consistently all day.

While I was only only doing 3 hot laps at full tilt after 2 warm up laps, this was far better than the first time where even 2 hot laps was dicey. Very likely I could have done more.

My car was easily hitting the highest top speed of the day down the back straight (210kph) and I was very confident hitting the anchors at the 120m meter mark every lap and making the next right hander at under 100kph.

I was clearly braking later and harder than a lot of smaller, lighter cars.

I would highly recommend this mod to people, but I need to make clear that the brake ducts are likely a larger contributor than the upgraded calipers. They helped managed heat so well.

In terms of pedal feel, as a fellow poster mentioned I think the pedal effort is now marginally higher. While some would perceive this as a negative on the street I think it added to the feel at the track, where you tend to apply a lot more pressure anyway.

[Kevin_The_Clean1]

@2BulkBen

Nice work here. I was simply worried about the MC (master cylinder size) difference between the V-8 powered M5 vs the inline-6 powered X3 M. It's got to create a difference in pedal effort... just like you mentioned.

The other thing I'm a touch concerned about it the OEM brake pad compound difference. Because now the rear brake pads of the X3 M will be at OEM factory specs (in terms of their compound) but the front brake pad compound will be composed of M5 specs.

So those are my two main concerns. But sounds like you've already worked through them both & they work much better than the stockers did.

Originally Posted by BulkBen

In terms of pedal feel, as a fellow poster mentioned I think the pedal effort is now marginally higher. While some would perceive this as a negative on the street I think it added to the feel at the track, where you tend to apply a lot more pressure anyway.

^^^ What exactly do you mean by this... ?

[BulkBen]

Hi Kevin,

I tend to find big modern brakes a bit touchy at times, so the pedal needing a firmer shove makes this less of an issue.

On the track I noticed a bit more feel, slightly less booster feel, meant better progression in the pedal. We are talking a minor difference though, if you hadn't driven the car before you'd never consider it to require a lot of effort.

The biggest gain was the pedal feeling very consistent all day though, much better than first time out.

[TTR]

if u put 265 on front, it will improve braking as well! 255 front is very small for x3m

[Kevin_The_Clean1]

Originally Posted by BulkBen

Hi Kevin,

I tend to find big modern brakes a bit touchy at times, so the pedal needing a firmer shove makes this less of an issue.

On the track I noticed a bit more feel, slightly less booster feel, meant better progression in the pedal. We are talking a minor difference though, if you hadn't driven the car before you'd never consider it to require a lot of effort.

The biggest gain was the pedal feeling very consistent all day though, much better than first time out.

I see what you're saying. I think with the added volume in additional caliper pistons, it's no wonder this is the case. When I put the F80 front brakes on my E90 335i I ran into this same issue. But read about it & researched it before hand. So I had to also upgrade the E90 335i to the E90 M3 master cylinder at the same time. So again, an inline-6 vs a V-8 powered BMW is going to have different pedal effort to master cylinder application ratios... as seen here. Wish you lived closer so I could feel & experience the pedal effort difference you're speaking about for myself.

[Kevin_The_Clean1]

@BulkBen - Just noticed something. I believe these are the very same front calipers that are on the G80 M3's... If this is correct, we could get them in ever more color choices. But we wold have to match the rears though.

https://g80.bimmerpost.com/forums/sh....php?t=1863065

[BulkBen]

Originally Posted by Kevin_The_Clean1

@BulkBen - Just noticed something. I believe these are the very same front calipers that are on the G80 M3's... If this is correct, we could get them in ever more color choices. But we wold have to match the rears though.

https://g80.bimmerpost.com/forums/sh....php?t=1863065

Yep, very likely the same, look very similar to me.
Being released on the G80 M3 means a much better chance of getting track focussed pads too.

Re pedal effort, the difference really isn't much at all. Some people have commented that my X3 brakes were very touchy before, so now they just feel more like a typical modern car - and not hyper sensitive.

I haven't given it a second thought, apart from when it was pointed out.

[Kevin_The_Clean1]

Originally Posted by BulkBen

Yep, very likely the same, look very similar to me.
Being released on the G80 M3 means a much better chance of getting track focussed pads too.

Re pedal effort, the difference really isn't much at all. Some people have commented that my X3 brakes were very touchy before, so now they just feel more like a typical modern car - and not hyper sensitive.

I haven't given it a second thought, apart from when it was pointed out.

I wonder if StopTech will be making some SS (stainless steel) breaded brake lines for the F97 soon. It sure helped out in other BMW 's that I've had before in terms of provided a touch more firmness in the break pedal feel.

[djhartm69]

I think the stock X3MC brakes are outstanding for track work, given what exactly this vehicle is... a 4600+ lb SAV.

I took my 2021 out while instructing for the regional BMW group at VIR earlier this year. Other than a flush with SRF, the stock brakes performed flawlessly.

Sure, I wasn't braking as hard or as deep as I do in my 2018 Z06 Z07 with AP Racing brakes & slicks, but I was duly impressed & had no problems with fade or modulation after 20+ minute sessions on Full Course (140+ MPH braking zones on the front & back straights). Full is not as hard on the brakes as North or Grand Courses, but still works the brakes very hard.

EBC sent me a set of Yellow comopound front pads off the M5 or M7 (can't remember which) to try, but they are still in the box.

What track & config did you cook the OEM brakes on so quickly?

[Kevin_The_Clean1]

BulkBen Please provide more info on this M5 caliper bracket you're speaking of. Can you post a few photos of what it looks like... ? And can you provide a part number for this... ?

For some reason, even when I look at the the M5 suspension & front nuckles there is no bracket. I want to do this conversion soon & I was able to find some brand new units for only $910 per caliper. So I'm pulling the trigger on this project NOW... !

https://www.realoem.com/bmw/enUS/sho...diagId=34_2548