[Dgjo2022X5MC]

Can someone confirm the minimum rotor thickness for the 19” M-Sport rotors please.

Can’t locate on the hat.

I am currently at 34.5mm and need front pads. I believe a resurface will put them under minimums.

[streborx]

Minimum thicknesses are often embossed in the rotor (or is that what you meant by "hat"?).

Check www.realoem.com for the replacement rotor. Minimum thickness is sometimes spec'd there.

[Dgjo2022X5MC]

Originally Posted by streborx

Minimum thicknesses are often embossed in the rotor (or is that what you meant by "hat"?).

Check www.realoem.com for the replacement rotor. Minimum thickness is sometimes spec'd there.

Thanks. Yes, the rotor hat (aluminum part) the cast iron attaches to. It is stamped nice and clear on my F95 rotor, not so much on this one.

[Dandle]

Minimum thickness is 34.4mm, they pretty much reach that on one set of pads.

[Qsilver7]

Originally Posted by Dgjo2022X5MC

Can someone confirm the minimum rotor thickness for the 19” M-Sport rotors please.

Can’t locate on the hat.

I am currently at 34.5mm and need front pads. I believe a resurface will put them under minimums.

From the part database for the front M sport brakes...it says the minimum thickness is 34.4mm for the brake discs (#3 in diagram):

[streborx]

This thread raises an interesting question. I always thought the minimum thickness spec was for machining, not wear. That is, a scored/warped rotor can be machined down to the min thickness, and remounted. But further scoring/warping mandates replacement.

[Dgjo2022X5MC]

I think the rotors are spent at 34.4, regardless how they got there. Be it wear or machining. Mine are ar 35.5 wear, after 45k miles. Machining will put them under. Wife’s car, so mild driving.

[eelnoraa]

Originally Posted by Dgjo2022X5MC

I think the rotors are spent at 34.4, regardless how they got there. Be it wear or machining. Mine are ar 35.5 wear, after 45k miles. Machining will put them under. Wife’s car, so mild driving.

As far as I am ware of, the spec is spell out more for head capacity related aspect, but not structural aspect. The rotor has plenty of strenght at that thickness. It is if you take car to some serious driving, and stress the brake, under that thickness, warpage or other deformation "can" happen. It is more of they test to that thickness and meet the requirement.

[TheACN]

Ok the big questions is; how much does it cost to get both the pads and the rotors replaced?

Upon visual inspection mine will be due soon (pad sensor hasn’t been touched yet). Interestingly rears seem worse than the fronts. I’m at 51k miles on my 2022.

[Dgjo2022X5MC]

Rear pads replaced at about 40k miles and rotors resurfaced. They said fronts were not at replace spec yet (for +1 Maintenance Program).

Not sure what the front rotors cost. I suspect around 350 each.

[Qsilver7]

Originally Posted by TheACN

Ok the big questions is; how much does it cost to get both the pads and the rotors replaced?

Upon visual inspection mine will be due soon (pad sensor hasn’t been touched yet). Interestingly rears seem worse than the fronts. I’m at 51k miles on my 2022.

I don't think your model year qualifies for BMW Value Service pricing yet...but for the f15 X5...you can see the various prices below from a screen shot from the BMW Value Service website. Just enter your zip code and select the participating BMW dealerships in that area...then enter your vehicle info. If you don't qualify, you can always call your local dealer's service dept and ask: https://bmwusaservice.com/valueservice

[Alan l.]

Make sure the gauge you are using isn't getting caught on the lip of the worn rotor giving you an inaccurate reading. I had to find a particular one where the contact point was raised slightly to avoid this on my X5M which i can feel has a sizable lip at the edge of the rotor

This is the tool I bought from amazon


As for minimum thickness and how it impacts the system I found this from the Brembo site.

Minimum brake rotor thickness

The correct operation of a vehicle’s braking system depends on various factors.
During maintenance work, a lot of attention is paid to brake pad wear but often neglecting to check the thickness of the rotors. Although entirely incorrect, it is common belief that the brake rotor is not subjected to wear. In actual fact, the same phenomenon responsible for brake pad wear leads to wear to the brake rotor as well.

The rotor wear limit is specified, as thickness below this specification will not guarantee the correct braking efficiency. This is a fundamental parameter and should be kept in mind during routine checks.

What are the consequences of using a rotor that is excessively worn?

Reduced thickness reduces the heat dissipation capacity of the rotor and its mechanical strength, triggering a series of critical faults and failures, such as:

the formation of thermal cracks on the braking surface, due to the rise in temperature and the reduction in the resistance thickness
deformation of the brake rotor, resulting in vibrations and noise
increased pedal travel, caused by reduction of thickness of the braking surface. In extreme cases, this can also lead to loss of tightness on the part of the caliper piston, with the risk of the pads themselves coming out of their seat or seizing.


In addition to the above problems, the use of a worn rotor could lead to the onset of another extremely dangerous phenomena, which could be generated in particular in conditions of heavy-duty vehicle use. These two issues are vapour lock and fading.
The high rotor temperature caused by a large number of braking actions - which is typical on a mountain trail - could generate the formation of vapour lock: in other words, the rise to above 200°C in the temperature of the braking fluid.
The fluid overheating generates air bubbles inside the circuit, air bubbles are compressible, which leads to no deceleration when pressing the brake pedal, despite being pressed all the way down.

The phenomenon of fading is also tied to the rise in temperatures, due to the reduction in the rotor thickness and the heavy-duty use of the vehicle. This rise in temperature reduces the friction coefficient between the brake pad and the brake rotor, with the ensuing increased braking distance.

[streborx]

Originally Posted by Alan l.

Make sure the gauge you are using isn't getting caught on the lip of the worn rotor giving you an inaccurate reading. I had to find a particular one where the contact point was raised slightly to avoid this on my X5M which i can feel has a sizable lip at the edge of the rotor
[/I][/b]

I was searching for additional definition of "minimum thickness" also, and found this same Brembo information, but it still fails to nail down what this min thick specification means.

Obviously, if your rotors are still above min thick and there's no unusual wear, there's no need to replace them. If the rotor thickness is less than min thick, then they should be replaced.

If your rotors have scoring or warp, and machining can resurface them and remain at or above min thick, then the rotors are good for use with one more new set of pads.

Is anyone's understanding of this different? I'll ask the auto store machinist that does rotor resurfacing next time I stop by.

[Dgjo2022X5MC]

I think my thickness gauge has a recess that would allow the lip of a rotor to not interfere like the one posted, but will check.

I wonder how much material is removed with resurfacing a rotor?

[eelnoraa]

Originally Posted by streborx

I was searching for additional definition of "minimum thickness" also, and found this same Brembo information, but it still fails to nail down what this min thick specification means.

Obviously, if your rotors are still above min thick and there's no unusual wear, there's no need to replace them. If the rotor thickness is less than min thick, then they should be replaced.

If your rotors have scoring or warp, and machining can resurface them and remain at or above min thick, then the rotors are good for use with one more new set of pads.

Is anyone's understanding of this different? I'll ask the auto store machinist that does rotor resurfacing next time I stop by.

I found the skill set to do rotor resurfacing is disappearing. It is expansive and job may not done right. When later happens, it will be endless debug for vibration. At least for my e39/46/82, i found replacing the rotor is as cost effective as resurfacing. Rotor cost for these cars are also low tho. These cars are old, plenty of after good quality market option. When my 45e gets to that point, I will see what is the best way.

[eelnoraa]

Originally Posted by Alan l.

Make sure the gauge you are using isn't getting caught on the lip of the worn rotor giving you an inaccurate reading. I had to find a particular one where the contact point was raised slightly to avoid this on my X5M which i can feel has a sizable lip at the edge of the rotor

This is the tool I bought from amazon


As for minimum thickness and how it impacts the system I found this from the Brembo site.

[b][I]Minimum brake rotor thickness

The correct operation of a vehicle’s braking system depends on various factors.
During maintenance work, a lot of attention is paid to brake pad wear but often neglecting to check the thickness of the rotors. Although entirely incorrect, it is common belief that the brake rotor is not subjected to wear. In actual fact, the same phenomenon responsible for brake pad wear leads to wear to the brake rotor as well.

The rotor wear limit is specified, as thickness below this specification will not guarantee the correct braking efficiency. This is a fundamental parameter and should be kept in mind during routine checks.

What are the consequences of using a rotor that is excessively worn?

Reduced thickness reduces the heat dissipation capacity of the rotor and its mechanical strength, triggering a series of critical faults and failures, such as:

the formation of thermal cracks on the braking surface, due to the rise in temperature and the reduction in the resistance thickness
deformation of the brake rotor, resulting in vibrations [...]

Yes I agree to this as well. It is thermal capacity and lack of qualification when thickness bellow criteria. It does not necessarily means there will be an issue.

I have done plenty of pad swap with same rotor myself. Such as before and after each auto sport event, I will swap to high temp pads, then back to factory pads. So effectively I am using more than one set of pads per rotor. I haven’t measure rotor thickness for a while, from the look, they are still very thick. Next time I do brake bleed, I need to remember to measure rotor thickness

[streborx]

I had the chance to stop by a local O'Reilly's earlier this week and ask about rotor resurfacing. Here's a brief summary.

1. A take-off rotor that measures at or less than minimum thickness is a throw-away.

2. Resurfacing down to the minimum thickness is permitted, and the rotors can then be re-mounted with a new set of pads.

3. If resurfacing down to minimum thickness doesn't completely refinish the surface, replacement is recommended.

4. Warp is the biggest problem -- machining to minimum thickness might not remove the warp or completely refinish the surface. Replacement is necessary.

5. Cost is $25 per rotor. Machining is done on-site using a specialty rotor machining lathe. Turn-around time is usually no more than a day; maybe same day during the week.

The replacement cost of the rotors on my Jeep is $75 each, so even these warrant machining at $25 if minimum thickness spec can be maintained.

[eelnoraa]

Originally Posted by streborx

I had the chance to stop by a local O'Reilly's earlier this week and ask about rotor resurfacing. Here's a brief summary.

1. A take-off rotor that measures at or less than minimum thickness is a throw-away.

2. Resurfacing down to the minimum thickness is permitted, and the rotors can then be re-mounted with a new set of pads.

3. If resurfacing down to minimum thickness doesn't completely refinish the surface, replacement is recommended.

4. Warp is the biggest problem — machining to minimum thickness might not remove the warp or completely refinish the surface. Replacement is necessary.

5. Cost is $25 per rotor. Machining is done on-site using a specialty rotor machining lathe. Turn-around time is usually no more than a day; maybe same day during the week.

The replacement cost of the rotors on my Jeep is $75 each, so even these warrant machining at $25 if minimum thickness spec can be maintained.

I have done it a few times at my local OReiley. They used to be called Kragen. There is a good chance Oreilwy doesn’t do it right too. After a couple of day or a week, need to take rotor back to them for more work. It is the time and hassle. But assuming the specific local OReiley know what they are doing, resurfacing is just fine.

[Dgjo2022X5MC]

What does everyone think about being declined for brake service coverage on rotors for the following reason: rotors not eligible at 34.42mm.

IMO the spec is 34.4, not 34.4X. Not trying to get anything for free as I paid for ultimate +1 and brakes are squealing like a stuck pig every stop.

[eelnoraa]

Originally Posted by Dgjo2022X5MC

What does everyone think about being declined for brake service coverage on rotors for the following reason: rotors not eligible at 34.42mm.

IMO the spec is 34.4, not 34.4X. Not trying to get anything for free as I paid for ultimate +1 and brakes are squealing like a stuck pig every stop.

Damn. This is crazy. So these days, when money is on bmw or whoever provide the ultimate maintenance package, rotors don’t need to be replaced with pad. But when the money is on you, rotors always needs be replaced with pads regardless of thickness

[Dgjo2022X5MC]

Originally Posted by eelnoraa

Damn. This is crazy. So these days, when money is on bmw or whoever provide the ultimate maintenance package, rotors don’t need to be replaced with pad. But when the money is on you, rotors always needs be replaced with pads regardless of thickness

It’s even worse. So the pads are at 4mm and they won’t replace pads until under that. And even if rotors are at minimum, they won’t replace unless pads are being replaced first. Jesus. I should have kept the 2k I spent on the ultimate +1 and just paid for brakes myself. I have a headache, and I haven’t even explained how they wanted 170 for the brake inspection!
Service Manager made a good call waiving as I flat out said I wasn’t paying that.

This all feels disingenuous from BMW as they really don’t explain all this when you buy the maintenance plan in advance. They are in complete control. It’s like managed healthcare I supposed. If the need doesn’t fit some guideline, you are out of luck. I won’t buy these in the future and just ‘self insure’.

[eelnoraa]

Originally Posted by Dgjo2022X5MC

It’s even worse. So the pads are at 4mm and they won’t replace pads until under that. And even if rotors are at minimum, they won’t replace unless pads are being replaced first. Jesus. I should have kept the 2k I spent on the ultimate +1 and just paid for brakes myself. I have a headache, and I haven’t even explained how they wanted 170 for the brake inspection!
Service Manager made a good call waiving as I flat out said I wasn’t paying that. .

Did brake sensor trip? If not, may I ask why you thinking inspection or even replacement are needed?