When should the brake disc be replaced?

[Gord]

I have a 1999 F-250 Super Duty rear wheel drive and have some slight pulsations and grinding noises when I apply the brakes. I removed the front wheels and there appears to be, at least, some brake pad left but I have not yet removed the caliper to do a close inspection. I did noticed some discoloration of the left front disc and when I spin it, it tends to ‘bind’ slightly in one location. There are no groves or ridges in the disc. The right front appears to be OK.

The question is, should I replace this disc (on the left) and the brake pads? If I replace this disc, should I also replace the disc and pads on the other side? Also, if I replace the disc (or discs) should I replace the wheel bearings or can I use the old wheel bearings in the new discs? The bearings appear to be OK, but I have not removed them to inspect.

Thanks very much in advance,
Gord

Topic

[619DioFan]

I would definently replace the rotors in pairs. make sure your calipers are in good shape and slide well . I would replace the wheel bearings if they are orig since you are in there already.

[college man]

We always do brakes in pairs/sets. Replace both
rotors and brake pads. lube the slide pins.

[Gord]

Thanks very much for the quick replies, this forum/web site is fantastic!!! :cheer:

Perhaps I should have been clearer in my original question… the disc is the type with the integrated hub. It’s not the type that just sits on the wheel studs, the disc, hub and studs are all one piece (well, OK you could replace the studs). That’s why I was asking about replacing the wheel bearings, they come out when you remove the disc.

So it sounds like I should just replace everything… disc, pads and bearings (and the grease seal of course)… better make a shopping list!! May also need to take out a loan, those discs are not cheap!

Thanks again,
Gord

[college man]

Those are expensive rotors/hub.You could have them
machined.as for bearing replacement.You should be able
to repack them with grease and install a new grease seal.

[EricTheCarGuy]

A couple of things come to mind after reading your post. To answer your question you would replace rotors when they are worn beyond their service limits. There is a minimum thickness for the rotors you have, you would measure the thickness of the rotors you have and compare that to the minimum spec. If they are within tolerance they can often be machined which means they can ‘cut’ the rotors true again. In addition to that some shops have an ‘on the car’ brake lathe meaning they don’t even have to remove the rotors from the vehicle to machine them. To be honest this is the best way to machine rotors as it takes up any run out that might be present in the hub assembly. Here’s a video on brake drums but the same thing applies to disc brakes.

Now as to the root cause of the problem you should probably check the caliper slides as well as the caliper operation. It could be that the side that’s ‘sticking’ is hanging up and overheating the brakes. If you don’t address this even after you replace or machine the rotors the problem is sure to return. This video may help you better understand what I’m talking about.

Good luck and keep us posted.

[Gord]

Thanks for the reply and good timing…
Just this weekend I decided to have a closer look at the front brakes to get a better idea what’s going on. I took the calipers off and discovered that one of the pistons (there are 2 per caliper) on the left side is seized, so that caliper will need to be replaced. One of the slide pins on that side was also quite sticky, so I removed both and cleaned and lubed them. The calipers now move freely on the pins, at least.

I’m going to do some looking around and try to find a shop that can machine the rotors. I have not yet measured them but I hope there is enough material left to clean them up. New rotors go for over $100 each so I’m really hoping I don’t have to get new ones.

The ‘shopping list’ so far is one new caliper, new brake pads and new grease seals. (and the machining of the rotors)

That should take care of the front brakes… next on the radar is the rear brakes…

Wish me luck! 😉

[college man]

Good luck. 😉

[Gord]

Well, I finally got a chance to replace the front brakes on the truck so I thought I’d post an update with what I did…

I’m sure those that do this sort of thing for a living will chuckle when I say it took me basically all day, but this is my first real repair so I’m quite proud of myself. Well I came out alive anyway and didn’t brake anything!!! 😛

What I did:
– replaced front brake pads
– had both front rotors machined
– cleaned and repacked wheel bearings
– replaced wheel grease seals
– replaced one brake caliper and bracket

Details:
I started about 9:00 am by removing both rotors and replaced one lug stud. The old one was not broken but it was starting to stretch, kind of strange.
Off to the machine shop to get the rotors turned. I had phoned ahead of time and they said they could do them. Got them into the shop about 11:00 and they were done by 1:00. I discovered when I took the rotors off that the grease seals I had were wrong, so I had to get two different ones. The guy at the machine shop said the rotors were still within tolerance so that was good. I can’t remember exactly but I think he said he took about 10 thousands off one rotor and about 15 thousands off the other. He asked if the truck sits a lot, I said yes, he said he sees that a lot where the imprint of the brake pad shows (rusts) on the rotor.
Got the rotors home and just started to clean and repack the bearings when I discovered I was out of grease!! Another trip back to the parts store!! :angry: Back home to finish the bearings, what a messy job, grease all over the place. Kind of strange that when you want the rotors to be clean, it is the messiest point in the process. When I took the nut off the spindle to remove the rotors I noticed it was finger tight and if I rocked really hard on the rotor I could just hear the clunk back and forth. Keeping in mind Eric’s advise that loose is better that too tight, I re-installed the nut to this same tightness.
Now I had to get the old caliper off. Not too much of a problem and I noticed that the old caliper had copper washers so when I installed the new one, I used the new copper washers they gave me. So far so good.
Now all I had to do was install the new brake pads and put the calipers back on. I put a little more silicone paste on the new caliper slide pins and checked the other but it was OK because I had had it apart a couple of weeks ago and put some lube on it then. Then a bit of anti-seize on the pads where they contact the brackets. The only tricky part was to hold the pads in place while I slipped the caliper back on. Those little springs that hold the pads away from the rotors are surprisingly strong!
All back together and took it out for a test drive… what 6:00??? where did the time go!! :ohmy:

Parts used/price:
Rabestos Disc brake pads part # ATD824C (ceramic) $49.79
SKF oil seal part # 24017 for 2 $42.78
Brake caliper with bracket front left Raybestos part # FRC20960 $85.00
Raybestos lug stud part # 28928B $ 1.00
Machine 2 rotors $70.00

plus grease and lots of rags!!

Summary:
I think it went quite well. Would have been a lot faster if I didn’t have to take the rotors in for machining and didn’t have to go back to the parts store for grease. Only one minor flesh wound on my hand, still have all my fingers!!
And the most important part, the truck stops nice and smooth now with no noise, so the customer is happy.

What next:
When I was tightening up the caliper bracket, I noticed the ball joint is loose. Not sure if I’ll replace that next or replace the rear brakes, they need doing as well.

Thanks so much to everyone on this forum, you gave me the courage to try this. I’m sure I’ll be back to ask even more questions in the future.

Take care!!

[college man]

Your most welcome. Glad everything worked out. 😉
Thanks for the update.

[Author]

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