Warped Rotors

[patrioty3k]

Hello all! Just throwing out my 2cents,don't know if your xc70 has the same suspension as an 850,but last year when my sons' '96 850 started shaking or vibrating, I thought that he needed new rotors.....much to my surprise,it was the control arm bushings on the r/side that were completely worn out....I purchased the whole control arm from FCP Groton,followed the tutorial here on MVS...solved the problem....Thanks....Peace Out!

[zhenya]

Warped rotors have not happened to my 850 since I discovered the cause.

Agreed. Truly warped rotors are extremely rare in modern vehicles. It is typically a high/low spot caused by the above, leaving the car parked wet for some time, etc. Re-bedding the pads often improves the situation greatly.

I would strongly urge you to avoid drilled rotors, which tend to be of sub-par quality, prone to cracking, while offering no advantages whatsoever.

[IVIUSTANG]

Warped rotors have not happened to my 850 since I discovered the cause.

Agreed. Truly warped rotors are extremely rare in modern vehicles. It is typically a high/low spot caused by the above, leaving the car parked wet for some time, etc. Re-bedding the pads often improves the situation greatly.

I would strongly urge you to avoid drilled rotors, which tend to be of sub-par quality, prone to cracking, while offering no advantages whatsoever.

For me, cross drilled rotors are great. Yes you can get low quality parts like you say and yes they can crack. That said, I bought cheap drilled rotors on ebay and have had them for 60,000KM and they still appear perfect with no cracks or pulse etc. My old solid rotors warped under these conditions, my cross drilled have not and they were far cheaper(less than $150 for all 4 wheels including pads.)

- Jesse

[zhenya]

Jesse,

I'm glad to hear that you have had good luck with your drilled rotors. My recommendations are general in that since cross-drilled rotors are drilled after casting, there is a serious risk of premature cracking. Since there are no associated performance benefits, and sometimes (although obviously not always) increased cost, I always suggest that people go for a traditional rotor. I suspect that there was something else going on with your previous rotors such as allowing a high spot to set from parking the vehicle wet or something similar that ultimately turned itself into an uneven rotor surface. Traditional rotors also have the option of being turned for cost savings, although this is an increasingly rare procedure.

[IVIUSTANG]

Your right, most drilling is done after the fact. I think the difference in some drilled rotors is that they are angled at the outsides of the hole to smooth off the corner; the "good" non casted cross drilled also make sure they don't drill through the cooling vanes etc as that is quite bad. Mine were also balanced and the cost was completely worth it, super cheap Chinese steel and casting with Canadian cross drilled on a CNC with balancing. I have no doubt shoddy examples exist.

- Jesse

[peacock]

Glad to see that people have had luck with the cross drilled rotors, i have a hard time finding them for the 16" wheels.
I replaced my rotors with medium quality ones from advanced auto parts about 25000 miles ago and anything above a very slow stop makes the wheel jiggle about 10* back and forth. the same symptoms before i replaced the rotors the first time [and i was doing alot of stopping while going down steep hills so the stopping power was pretty compromised]

i will definitely be considering these for future purpose

[Ozark Lee]

I had my rears turned on the '94 after I got it and replaced the non functioning parking brake shoes. They were good for maybe another 10k miles before they warped again and I bought new cross drilled rotors for the same money as the price of getting the old ones turned. Give or take 75k miles later the cross drilled replacements are still running fine.

...Lee

[polskamafia mjl]

The Zimmerman cross drilled rotors I have, have been amazing so far. If nothing else, they cool much quicker than standard rotors.

[zhenya]

Not in any significant way they don't. Cross drilled rotors provide a cosmetic upgrade only. If they provided a performance benefit they'd be used on race cars, and with very few exceptions they aren't. The drilling significantly reduces the integrity of the rotor and reduces the mass available as a heat sink which tends to outweigh any marginal improvement in air flow.