Brakes: F & R ~ ROTORS Questions

[_XS3C_]

Hey folks have questions regarding the ROTORS [X5 '05 4.4i sport]:

F rotors current thickness is - 31mm [the minimum thickness stamped on the F rotors is 28.4mm] difference of 2.6mm.
R rotors current thickness is -20mm [ the minimum thickness stamped on the R rotors is 18.4mm] difference of 1.6mm.


1. Does anyone know the thickness on brand new oem rotors F/ R ?
2. I'm about to change ALL F/R pads - should I change ALL Rotors at that same time, does the above thikness of 2.6mm F and 1.6 mm R is enough to be left for new pairs of F/R brake pads ?
3. How many miles this rotors thickness of 2.6mm F & 1.6mm R down to the minimum will last ...... [ just a wild guess] ? ---- [ sure it all depends from the driving style and so on other factors but still on average .... is it for example 1k or 10k miles ]
4. Currently my X5 does have 70.000 miles any opinions if that are the original rotors or it is on the second, 3rd pairs ?
5. when installing the Rear rotors do they SLIDE over the Ebrake pads with no problems or you will need some tools to fit that E-brake pads ? --- [ or if the Ebrake is NOT applied then it's all ok to install R rotors with no problems].
6. any opinions on drilled or/and slotted rotors on the X5 ? ---- [ they are pretty much the same price as the none drilled non oem rotors ..... so I'm wondering if I should go for drilled ones...[for the look/ performance]] ...


Thanks in advance

[JCL]

Based on the measured thickness, you can reuse those rotors. Now, the other things to check:

Is there a ridge or lip at the outer circumference, that may cause noise?

What is the surface finish like - are they glossy, blue, showing heat spots, etc? Any cracks or lines?

What is the surface condition like - any grooves or other wear that may cause brake pad noise after installing new pads?

While it is perfectly possible to reuse rotors, many times I replace mine simply because I don't want the hassle of doing them again if I get any brake noise with new pads. I know I don't need to, but I do get better braking that way, and I don't consider the cost to be significant. After 70,000 miles, I would figure they don't owe me anything. You may be on the original rotors, or the second set, can't say.

If you do reuse them, bed the pads in, and then see if there is any noise (squealing, squeaking, rough noise on application, etc). If so, you may decide to replace them, or simply to live with it. If they are just fine, then no worries, you are good to go. You will be replacing them next time based on the thickness anyway.

Don't get them machined.

I would only use OE rotors. The ones I got last time had an anti-rust coating, and they performed well. The differences between good and cheap rotors are trueness, and the design of the cooling fins. Cheap rotors will have straight fins, less cooling, and are thus easier to fade. If you look at cheap ebay rotors and OE rotors you will see the difference. Many consider rotors to be simply a commodity, and buy the cheapest. I don't share that opinion.

I would never buy drilled or slotted rotors. They are purely for looks when parked, and have reduced performance (noise, structural integrity, pad life). The rotors that were designed to be drilled were cast that way, they weren't simply blanks drilled afterwards. I figure that brake parts that are at their best when the vehicle isn't moving aren't the best choice.

[Bayerische E53]

^ALL OF THIS.

Well said, JCL.

[pap smear]

I noticed the ridge/lip on my rear driver side rotor could you explain what it's about and if I need to change it or not

[JCL]

Originally Posted by pap smear

I noticed the ridge/lip on my rear driver side rotor could you explain what it's about and if I need to change it or not

The pad doesn't extend to the outer edge of the rotor, so doesn't wear that part. The depth of the lip is how much thinner than original your rotors are. Measure them. If they haven't gone below the minimum thickness, the only problem with the lip is if it causes noise. You mention the driver's side. If they vary side to side then something isn't right, maybe a sticking caliper on that side.

[FSETH]

JCL comes through again.

The only thing I can add is that if you go aftermarket, Centric makes a great rotor. Especially their blanks. Pretty sure they have OE cooling fin design and it seems they put a good amount of effort into the machining process. They also have coated hats that prevent corrosion. I have used them a few times in the past and have been happy with their performance. They are also considerably cheaper than OE.

DRUMS AND ROTORS - Centric Parts

[_XS3C_]

JCL, Thanks
Great info, that did answer pretty much all of my answers.
- btw on ALL 4 rotors the surface finish is smooth, with no cracks or lines or any heat spots and with out any groves. The ridge lip [just by look] is around 1mm or so ...........
- I'm 90% OEM person so not big deal for the drilled rotors besides they will not show at all behind my #132 style rims with that big spokes + I asume extra dust ~ wearing the pads more quickly ...

FSETH, It look's like I'm not going to replace them at that time but will keep in mind the suggestions for the CENTRIC brand. Thanks.

[bcredliner]

Agree with JCL. Change rotors with every pad change. For the reasons already mentioned and OE pads are soft for improved stopping difference and not that thick out of the box. Thinner rotors means they get hotter sooner. The hotter they get the poorer the braking performance.