Will resurfacing a brake rotor, remove warpage???

Will resurfacing a brake rotor, remove warpage???

I argued with a guy at the local auto parts store. The fact that my pedal and front end pulsates/vibrates when I'm braking says to me that the rotors are pretty warped.
That being the case tells me that resurfacing the disk is not going to "unwarp" the thing.

This guy was adamant that resurfacing would solve the problem.
I know from experience that this isn't true. I had a car that warped the rotors pretty badly. I got them resurfaced and I reinstalled them and the problem was still there.
I then replaced the rotors and the problem disappeared.

What do you guys think?

Thanks,
Manuel

I've had warped rotors turned and the problem was solved; however, I would say that you can't necessarily be assured that it will work. If they are so warped that there isn't enough thinkness to allow truing them, then it certainly wouldn't work. It might be a gamble, but I would give it a try if there was adequate meat on the rotors. Around here they charge about $10 per rotor so I'd compare that with the cost of new ones.

What year is your XJ?

The older XJ rotors are all cast and resurfacing usually trues them up very well. The newer ones are composite, and they warp very easily. Resurfacing makes 'em true, but it doesn't last long. The problem is, the replacements are also composite, and they warp equally fast.

I have a 99 XJ with 4WD, command trac.
3 1/16 overall height disks.

How would a cast disk and a composite disk look different, or do they look the same?

The vibration when braking is annoying.

I have a hard time understanding how resurfacing the disk could get rid of warpage. I figure if the disk warps, the whole disk is slightly curved now. Even if you were to machine it, it should stay warped because the whole thing isn't straight.
The only way in my mind that a disk could pulsate and yet be able to be made flat again would be if there was more material on on part of the disk than another. The machining would then remove the extra material.

Can someone explain how it would be possible for machining to make the disks flat once again. Is it that only the top surface becomes wavy???

Thanks,
Confused Manuel

THe machining is all relative to the mounting point of the rotor. if that part is true and just the friction surface is warped than it can be trued through turning it. But if the runout is too severe, after you turn it there will a good chance that they will be thinner than minimum thickness.

You have a composite rotor in a '99 I believe. The composite is a two piece rotor basically (although you can't seperate them without a really, really big hammer), the rotor surface is cast iron, the hat is sheetmetal.

Cast is 100% cast rotors, not sheet metal, so they're stronger.

Argument with Brake specialist

Well, I went to get my rotors turned at a local place that specializes in only brake parts. These guys have rotors and drums all over the place.

BTW, my 99 XJ had cast discs. They were not composite type.

Well, the guy checked the rotor and said that the rotor was too thin to be turned so they offered me some new ones.

He first came out with a couple that were NOT in a box and he told me they were Raybestos. I couldn't find any Raybestos marking on there,(only numbers) but he said he bought them from a supplier who had them in boxes outdoors and they got rained on which ruined the boxes.(so he was selling them for half price) I measured the height, and they were a little taller than the ones on my XJ so I was hesitant to get them since I couldn't tell what they were. He didn't like that.

Then he offered me some that were supposedly made in China but they were "premium" not the "economy" discs and they were made well.
This guy says he's been in business 20 years so I trusted him. I asked him a lot of questions which he didn't seem to like, he got defensive.

Saturday afternoon I installed the disks and wanted to test drive the XJ. The XJ WOULD NOT MOVE!!
I took off the disks and found the problem. The seating area around the bolts was too thin so when I torqued down the wheel, the disk bottomed on the hub.

I did some research, measured the disks, and concluded that he gave me the wrong part number.
I was pissed.


I went back Sunday morning and told him these were the wrong ones. He got visibly irritated.
I was irritated too since I wasted my Saturday afternoon taking off his disks and putting my old ones back on.

He said that from 84 to 2001 the XJs use the same part number. I even showed him a page from an online catalog showing the part number difference starting in 1999 and that there were 2 overall heights available 3 1/16 and 3 3/16.

He was stubborn and said that it was the same disk even when the sheet shows 2 different part numbers. I got irritated that he was insinuating I didn't put them on right or that I was wrong.

I told him he could take the damn tire off and see for himself that the ones he gave me wouldn't fit.

He went out and looked at my disks. Then he said that I must have an oddball truck or there is something wrong with it. He said the disks on there looked like the ones he gave me. He saw that there wasn't much clearance between the disk and the plate behind the disk, so he finally realized that the ones he gave me wouldn't fit.

He gave me the so called "Raybestos" rotors he had originally offered me. They appeared to be similar in size as the Chinese ones I installed except that the seating area was thicker, so I figure they might fit.

This guy was stubborn though. He tells me that if these don't fit, he'll personally take the wheels off and replace them with Bendix parts.

For all of you with 99+ XJs:
Starting in 99, the XJs are offered with 2 different disk sizes. Don't let anyone tell you different. I looked up several disk rotor manufacturers and they all show 2 different sizes for the 99+ XJs. Prior to 98 there was only 1 part number available.

Wish me luck with the new install. I'll let you guys know how it goes.

Sorry for the long post. I had to vent.

Manuel

They guy said not change? He's full of it. I know that the size of the hub changed between 1989 and 1995 (not sure which year), anyway, an old rotor will NOT fit on a new hub.

Well, the 2nd set of rotors that the guy gave me still didn't fit.
I went back and told him that AND that I wanted a refund.
The guy was really mellow about it this time.
He said that he was going to find out what part number my XJ uses and order some of them to have them in stock. He said he could probably have them tomorrow.
He said he found a blank spot in that catalog for the part number on my 99XJ.

He stuck to his word and said that he would install them for me. I told him I might be back tomorrow, and thanked him.


Obviously I'm not going back there.

I just ordered some Raybestos rotors online.
This saga should be over soon.

Manuel

I was under the impression all later style rotors were the 'composite' type...ie., cast rotor, steel hub portion. However, this small difference in dimensions you speak of could indeed be the difference in the thickness between full cast and composite. Would be good to honestly determine the real scoop!! Judd

From the specs I looked up, the 3 1/16 rotor is an all cast rotor.

The 3 3/16 rotor is a composite rotor.

I'm attaching a couple pictures of the last set of rotors that the guy gave me. These are all cast. These didn't fit either. The center hole was just a tad small.
It looks very similar to the ones I have installed.

Once I get the new rotors, I'll post pictures of the new and old.

Manuel

I to have a 99 Sport and assumed that I had composite rotors. Wrong! I also have the full cast rotors. I pulled the wheels yesterday and did some measuring. They are 3 1/16 tall and the mounting surface is 3/16 thick. The dealer only has the composite rotors available for the 99 even though they do have a cast part number it refers back to the composite. My pads are in good shape and the rotors are worn but still servicable and I have no warpage, yet. Napa has cast rotors for the 99 that are 3 1/16 tall but the mounting surface is thicker. I hope that the rotors you ordered are the correct ones and you will let us know.

I'll let you know.
I ordered them online.(they are Raybestos) I should get them on Tuesday.
Mine measured 3 1/16 also.

The 3 3/16 rotor is available from most of the auto parts stores.
That part number rotor is used from 1995(I believe) up til 2001.

From 1999 to 2001 though, there are 2 part numbers available, one with 3 3/16 height and the new one with 3 1/16 height.


The 3 1/16 rotor though is much harder to find. They were all special order.

Manuel

If you find a decently priced reliable source for the 3 1/16 rotors (preferably full cast)

PLEASE SHARE!!!

I swapped ALL 2001 XJ stuff on to my 89 housing and I'm running the 3 3/16 rotors with 1/8" thick hardened washers behind each stud. I'm a little leery of the setup, but it's been good for about a year and a half with no troubles.

There are actually 3 different rotors used throughout the life of the XJ:

84-90 or 92 (not completely sure where the cutoff was, it either coincided with the c-clip rear end, or the drop of the bendix ABS) were a full cast rotor, 3 3/16" but with a smaller inside diameter than the later rotors (these rotors will NOT fit over the later hubs)

???-mid 99 same as above rotor but with a larger inside diameter. come in both composite and full cast (aftermarket ones seem to be composite)

mid-99-2001 this change is DIRECTLY related to the low pinion housing. The unit bearing is 1/8" shorter in these axles, hence the 1/8" shorter rotor. I would assume that these are identical to TJ rotors.

Perhaps a cross reference to TJ rotors (if the part #s match), and a comparison of the measurements will lead us in the right direction.

if this gets to be too much of a hassle... I'll just cut some spacers out of 1/8" plate and stop worrying about the washers (the washers vary slightly in thickness, really frightens me )

Hey CheapXJ, I have some answers for your questions.

I just go the disks I ordered. They fit perfectly. They are Raybestos PG Plus P/N 76923. These have an overall height of 3 1/16 . They are ALL CAST.

The 1999-2001 XJs came with both the composite rotor and all cast rotor. Theses rotors are not interchangeable.

My dilemma is finally over. I installed these this afternoon. Braking is nice and smooth now.

I've attached a couple pics.

Manuel

Another Pic.

Another pic, showing the seating surface of the rotor. As you can see, both the new and old have the same thickness.

Manuel

It all depends on how much warp is there. When you take metal off by resurfacing it reduces your braking performance. But if you resurface it and the ending surface is thicker than minimum spec (the shop the turns the rotors will know) than you are golden.

Hey, Manuel, where online did you order the Raybestos disks? I have the same problem with my 2001 XJ. What pads will you be using with them?