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#1
Old 10-01-2013, 06:12 PM
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Rusty rotors, what's the best course of action?

Hello Everyone,

I own a beautiful 1984 Mazda RX7 GSL-SE that I lovingly restored before my back breaking accident. Because I have had more important things to contend with I haven't paid the RX7 much mind over the last few years. I have however started it every week to keep the battery charged and to keep the seals from drying out. Lately my Sons have expressed interest in the car and I am getting ready to drive it again. Everything is checking out okay except for the brakes. The entire braking system seems to be in good working order except for rust on the rotor discs. This is of course surface rust from not being driven for so long.

Usually when I see rust on a rotor I would just drive the car and let a few swiped of the pads clear the rust off. In this case I don't think that will do considering the rust is more than a light coating. Now, it isn't bad enough to replace the rotors, but I'm not too sure that it would be healthy for the pads to drive the car. So, what I'm asking is what would be the next reasonable thing to do? I have considered the following:

A: I could pull the rotors off of all four corners and take them down to the local machine shop and have them turned. This will cut the rust off and leave me a nice shiny perfect surface. This would probably be the best solution, but I would rather not go this route because I don't have a lift, so I would have to do two wheels at a time. This would be quite time consuming, but if it's the only way then that's what I'll do.

B: I'm wondering if taking a wire brush to the rotors would be effective. I was thinking about a wire brush wheel attached to a cordless drill. Effectively I would use it to "brush" off the surface rust on the rotor. I wouldn't put any pressure on it, just enough to "dust" off the harder stuff on the surface. I figure that way the pads would take care of any left over rust when the brakes are applied the first few times. This is the route I would prefer to take because it is the simplest and the most cost effective. Just wondering if this is a good idea. I can't see harming the rotor surface providing I don't apply any pressure to the wheel.


So, mechanical types here what say you? Would it be okay to use a wire wheel and skim the rust of the surface of the rotors or should I pull the rotors and have them turned to give a brand new surface?
#2
Old 10-01-2013, 07:06 PM
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As always, it depends.

If the rust is just superficial, letting the pads scrub the rotors clean will suffice. Just take your time, perhaps in the far reaches of a parking lot for 5 minutes of progressively harder braking.

If the rust is eating deeper into the rotor, you'll have to pull them and have them turned. PITA, I know, but you don't want big pits in the rotor.

Pull one wheel, hit the rotor with steel brush on your drill and see how much that helps. If there are no, or some tiny pits, normal braking should clean them up.

Otherwise, invest a Saturday with trips to the machine shop.

Then again, why not upgrade to some new high-performance rotors? It's only money!
#3
Old 10-01-2013, 07:49 PM
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I would just try driving it. Not in stop and go traffic, mind you, but take a leisurely cruise around the neighborhood and see how it turns out. I bet the rust will take care of itself and if it doesn't you really don't have anything to lose.

If you machine or replace the rotors you should replace the pads anyway IMO as they're inexpensive and you already have everything apart. It's like always replacing the throw out bearing when you replace a clutch, or replacing the timing belt/chain if you take the head off. You're in there, the labor's done, do it 100%.
#4
Old 10-01-2013, 08:16 PM
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Quote:
Originally Posted by ducati View Post

Then again, why not upgrade to some new high-performance rotors? It's only money!
Great idea except that I use the car to autocross and upgrading the rotors would bump me out of the stock class. No new shiny holes rotors for me. That's why the boys are so interested in the car now. They are old enough to be able to ride along during the autocross runs. And quite frankly I really miss taking the car out to the track on the weekend. For those of you who don't know what autocross is, visit the SCCA's website and you'll have more fun for little money than you ever dreamed possible.

I think that I'll try hitting the rotor surface with a steel brush to loosen the rust and take her around the block a time or two. If that doesn't work as expected I'll pull the Titus, have them machined and throw in a new set of pads. I just wanted to make due that there want something obviously wrong with my wire brush plan.
#5
Old 10-01-2013, 11:14 PM
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While I can't say I have a specific reason to be wary of using a steel brush, I'd be much more comfortable using a Flex-Hone. Google on flex hone for rotors for more info.

Note that it's twenty times easier to do this with the rotors off.
#6
Old 10-01-2013, 11:31 PM
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regular rotors are $25 apiece. If it were me I'd drive it and see what happens. chances are the old ones are warped a little anyway and now is a good time to change them out.
#7
Old 10-01-2013, 11:32 PM
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Quote:
Originally Posted by Gary T View Post
While I can't say I have a specific reason to be wary of using a steel brush, I'd be much more comfortable using a Flex-Hone. Google on flex hone for rotors for more info.

Note that it's twenty times easier to do this with the rotors off.
Thanks for the tip. I agree and plan on removing the rotors to do this. Removing them is the easy par. I live a good thirty Mikes from the nearest machine shop, so I'm trying to find a solution that won't involve 120 miles of driving to get the rotors machined. Maybe for Christmas I'll ask Santa for A rotor lathe!
#8
Old 10-01-2013, 11:39 PM
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Argggggggggggg foiled by auto correct again. When will I ever learn that preview is my friend. Sorry for the gibberish that's my last post. par = part and Mike = miles. Why yes I am an idiot.
#9
Old 10-02-2013, 08:55 AM
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I'd do this in the following order.

1. Just drive it. Gently at first. If the rust goes away after a few good stops no problem.

2. If it's still there, have the discs machined.

3. The discs may be too thin to machine. In that case get new rotors. Spend the extra money go get good rotors. The cheaper rotors are often made of inferior materials and warp rather quickly.

4. In either case 3 or 4 get new pads. If the old pads aren't perfectly smooth, it won't take long to cut into the resurfaced or new rotors.

5. Forget about the wire brush. If #1 won't remove it, I doubt that the wire brush will do much better.

Another thought: You said your sons are interested in the RX-7 (as they should be)? Make them do the work! Make them earn the right to drive it. Heck I had my youngest daughter working on cars with me at 10 YO and she's a mechanical engineer now.
#10
Old 10-02-2013, 10:43 AM
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Quote:
Originally Posted by obbn View Post
Thanks for the tip. I agree and plan on removing the rotors to do this. Removing them is the easy par. I live a good thirty Mikes from the nearest machine shop, so I'm trying to find a solution that won't involve 120 miles of driving to get the rotors machined. Maybe for Christmas I'll ask Santa for A rotor lathe!
Do you live near an auto parts store? Most of them have a rotor and drum lathe and will turn them for a nominal fee.
#11
Old 10-02-2013, 12:03 PM
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Originally Posted by bump View Post
Most of them have a rotor and drum lathe and will turn them for a nominal fee.
It seems that many rotors are made just above the minimum acceptable thickness, so they rarely can be turned without making them too thin. But a car from 1984 may pre-date that problem.

I tend to agree with the "just drive it" advice. This will probably yield acceptable results, provided you're not seeking perfection. If it doesn't, you're into new rotors & pads (of whatever quality/price you find attractive).
#12
Old 10-02-2013, 06:10 PM
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Quote:
Originally Posted by JerrySTL View Post
Another thought: You said your sons are interested in the RX-7 (as they should be)? Make them do the work! Make them earn the right to drive it. Heck I had my youngest daughter working on cars with me at 10 YO and she's a mechanical engineer now.
I'm right with you on this one. The boys have gotten to be pretty good "wrenches" over the last few years, despite being only 10 and 11. I have a serious back injury that prevents me from doing a lot when it comes to the cars, even though I enjoy it so much. So, I provide the knowledge and the boys provide the labor. They are learning so much and it is amazing to see them, even at their age, come up with a solution or identify a problem when we are working on the cars.

Our daughter is going to be driving soon, so my wife and I searched for a car for her. I found a 1988 Nissan 300zx with a perfect body and interior that the owner could get running. I paid him $700 for it, brought it to the workshop and the boys and I had her running in no time at all. I told them that the same will apply to them when it comes time for their car as well. (And no, I'm not suggesting that girls can't work on cars too. I was hoping that my daughter would show some interest, but getting her fingers greasy isn't her cup of tea)

It is important to me that I raise my boys to be men and men that are able to do things for themselves, not having to rely on someone else or pay to have everything done. Sometimes they don't like me very much because they have done everything from work on cars to re-roof the workshop. However you can see the pride in their faces when they tell their friends "I did that"!


Quote:
Originally Posted by bump View Post
Do you live near an auto parts store? Most of them have a rotor and drum lathe and will turn them for a nominal fee.
That's the only problem that I'm facing. We live in the middle of nowhere (just as we like it!) and the nearest machine shop that can turn the rotors is about 30 miles away. Since I can only do one side or one end at a time it would require about 120 miles round trip to turn the rotors. So, if I could do it without turning them it would be preferable.


Quote:
Originally Posted by Xema View Post
It seems that many rotors are made just above the minimum acceptable thickness, so they rarely can be turned without making them too thin. But a car from 1984 may pre-date that problem.

I tend to agree with the "just drive it" advice. This will probably yield acceptable results, provided you're not seeking perfection. If it doesn't, you're into new rotors & pads (of whatever quality/price you find attractive).
In this case the rotors that are on the car have never been turned, so I can safely assume that have at least one turning session in them. I don't mind using the pads to clear the rust, the reservation I have is I know that the pads are fairly new with only a few hundred miles on them. I didn't want to damage the pad surface grinding the rust off.


In the end, this is my fault. While I started the car on a weekly basis, I didn't drive it. The reason I didn't is that the car is setup for autocross and has Momo racing seats in it. While recovering from my back surgeries there was no way that I was able to get in and out of the racing seats. I can now (well, I know I can at least get in. Getting out should be interesting!) I'm actually kinda embarrassed at the state of the brakes as I have always been on top of my vehicle maintenance. The absolute worst thing you can do with any type of machinery is to let it set.
#13
Old 10-03-2013, 03:56 AM
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Quote:
Originally Posted by obbn View Post
In this case the rotors that are on the car have never been turned, so I can safely assume that have at least one turning session in them. I don't mind using the pads to clear the rust, the reservation I have is I know that the pads are fairly new with only a few hundred miles on them. I didn't want to damage the pad surface grinding the rust off.
How many miles on the rotors? I ran my current car to 180K on the original rotors and they were.... eaten alive. I knew they were warped but good lord I had never seen such utter destruction ofa rotors. I don't turn them because it means there is less metal to deal with the heat and are going to warp faster. Replacing them is one less problem down the road.

You've got a nice car worthy of a little TLC.
#14
Old 10-03-2013, 11:43 AM
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Quote:
Originally Posted by Magiver View Post
How many miles on the rotors? I ran my current car to 180K on the original rotors and they were.... eaten alive. I knew they were warped but good lord I had never seen such utter destruction ofa rotors. I don't turn them because it means there is less metal to deal with the heat and are going to warp faster. Replacing them is one less problem down the road.

You've got a nice car worthy of a little TLC.
Very little, I'm sure it's under 1,000 miles. After I restored the car (I replaced the rotors at that time) the car was only used for the occasional autocross event or occasional weekend drive to promote the business I had (I sold automotive aftermarket parts). The rotors are in good condition except for the surface rust from dis-use.
#15
Old 10-03-2013, 12:24 PM
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You really don't need to replace the rotors. You really don't need to replace the pads. I don't think the rust, even if it's copious amounts as surface rust goes, will harm the pads, but if there's any question the pads can be dressed with coarse sandpaper.

I still think the best course is to use a Flex-Hone.
#16
Old 10-03-2013, 01:17 PM
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Originally Posted by obbn View Post
Very little, I'm sure it's under 1,000 miles. After I restored the car (I replaced the rotors at that time) the car was only used for the occasional autocross event or occasional weekend drive to promote the business I had (I sold automotive aftermarket parts). The rotors are in good condition except for the surface rust from dis-use.
OK, then what Gary T said. Knock the rust off with a flex hone if you're worried it will grunge up the pads.
#17
Old 10-04-2013, 01:45 PM
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Usually far cheaper to just replace than turn rotors. Call for an estimate, then once you've got up off the floor from laughing, call the auto parts store.

Nissan rotors: $19
Estimate for turning them: Starting at $59
#18
Old 10-04-2013, 01:54 PM
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Rotor and hub from NAPA: $35
#19
Old 10-04-2013, 02:28 PM
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Wow, I'm really surprised at the cost of turning rotors. Quite a bit considering it's practically a hands off job once the rotor has been placed on the lathe. When I had my own business selling auto parts I sponsored a race car. The owner of that car was a mechanic and anytime I needed anything like this I would just drop it off at his shop and pick it up when done. I guess I lost track of the cost of things!
#20
Old 10-04-2013, 06:06 PM
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Originally Posted by obbn View Post
That's the only problem that I'm facing. We live in the middle of nowhere (just as we like it!) and the nearest machine shop that can turn the rotors is about 30 miles away. Since I can only do one side or one end at a time it would require about 120 miles round trip to turn the rotors. So, if I could do it without turning them it would be preferable.
Do you have any jack stands?
#21
Old 10-04-2013, 06:53 PM
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Prices vary, obviously, but the last time I got rotors turned it was $28 for a pair. This was at a repair shop in Long Beach, California about two years ago.
#22
Old 10-04-2013, 11:32 PM
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Originally Posted by Gatopescado View Post
Usually far cheaper to just replace than turn rotors. Call for an estimate, then once you've got up off the floor from laughing, call the auto parts store.

Nissan rotors: $19
Estimate for turning them: Starting at $59
No, occasionally cheaper, and by no means far cheaper, to replace rotors than to turn them. You have quoted the price for a rather inexpensive rotor and compared it to what I would call a ridiculously high price for turning one. I've gotta wonder what's behind that $59 quote -- sure doesn't sound right to me.

Quote:
Originally Posted by brad_d View Post
Prices vary, obviously, but the last time I got rotors turned it was $28 for a pair. This was at a repair shop in Long Beach, California about two years ago.
This is about the norm in my experience.
#23
Old 10-05-2013, 06:39 PM
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I'll throw in my opinion that you are overthinking a little. Taking me years to understand this in my anal paranoia. Drive it and it will scrub off the rust by itself. It has low miles since you last had it apart and wasn't parked in a puddle in the weeds behind a barn or anything.

Wouldn't take it off a trailer and autocross it right away, but a nice drive around the block and I'll bet it's all good. Then autocross away! Yeah way too much damn fun, first time I did it was in a Ford F-150 stock pick up. Just went to see a friend and they said all are welcome. He has a photo of me with a rear tire off the ground, wheeeeeeeeee! Life is short, run what you brung.
#24
Old 10-05-2013, 10:29 PM
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Originally Posted by Gary T View Post
No, occasionally cheaper, and by no means far cheaper, to replace rotors than to turn them. You have quoted the price for a rather inexpensive rotor and compared it to what I would call a ridiculously high price for turning one. I've gotta wonder what's behind that $59 quote -- sure doesn't sound right to me.

This is about the norm in my experience.
What's $28 a pair X 2 equal? $56. I think the quote is for all 4 rotors turned.

Last edited by Magiver; 10-05-2013 at 10:29 PM.
#25
Old 10-06-2013, 02:58 PM
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Originally Posted by Gatopescado View Post
Usually far cheaper to just replace than turn rotors. Call for an estimate, then once you've got up off the floor from laughing, call the auto parts store.

Nissan rotors: $19
Estimate for turning them: Starting at $59
Quote:
Originally Posted by Magiver View Post
What's $28 a pair X 2 equal? $56. I think the quote is for all 4 rotors turned.
So then is $19 the cost for four rotors?

If the $19 vs. $59 comparison isn't for a like number of parts/machining operations, it's rather meaningless.
#26
Old 10-07-2013, 12:01 AM
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Originally Posted by Gary T View Post
So then is $19 the cost for four rotors?

If the $19 vs. $59 comparison isn't for a like number of parts/machining operations, it's rather meaningless.
No I'm suggesting the person who got a quote up-thread mistook the price of turning 4 rotors for the price of turning 1 rotor. I base this on what was posted for the cost of 2 rotors.

Last edited by Magiver; 10-07-2013 at 12:02 AM.
#27
Old 10-07-2013, 11:23 AM
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Rusty rotors, what's the best course of action?

http://i28.photobucket.com/albums/c236/dash13/RTbna.jpg

Evaporust. $20 for a jug at the auto parts store. Pull all 4 rotors and dump them in a bucket with 50/50 evaporust and water overnight.

I have a 40 year old Harley Davidson. I have to do this kind of thing a lot. That's my gas tank before and after.

Last edited by Sgt. J; 10-07-2013 at 11:24 AM.
#28
Old 10-07-2013, 12:40 PM
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Originally Posted by Sgt. J View Post
http://i28.photobucket.com/albums/c236/dash13/RTbna.jpg

Evaporust. $20 for a jug at the auto parts store. Pull all 4 rotors and dump them in a bucket with 50/50 evaporust and water overnight.

I have a 40 year old Harley Davidson. I have to do this kind of thing a lot. That's my gas tank before and after.
Have you done this with your brake rotor? Does it affect your stopping distance after using it?
#29
Old 10-07-2013, 01:22 PM
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Quote:
Originally Posted by ZenBeam View Post
Have you done this with your brake rotor? Does it affect your stopping distance after using it?
Yep. Can't say for sure as I didn't do any known distance stopping tests, etc before and after, but just from riding it doesn't seem to have made any difference. I had a cracked rear rotor so I pulled it off and got an old rusty POS from a guy I know who had a box of crap sitting in the shed. Soaked it, cleaned it up, and threw it on. Been riding on it for over 2 years. Even though it's not scientific, I would probably notice if the stopping power was affected as I only have one brake on that motorcycle. I don't run a front brake on that bike.
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