Hammering off rusted rotors

[BarryWells]

heat between studs with a real torch if they don't come with a little hammering.

There ya go.............

 

[theoldwizard1]

Can always do the bolt and nut combo through the caliper bracket if you don't want to hammer.

Watch the above video but here is a snap shot (shorter, fatter bolts would be better).



After 6 or 8 turns on each bolt, losen them, turn the rotor about 1/4 turn and repeat. It will leave a mark on the rotor. E Z !

 

[MikeF2316]

I've always been taught not to hammer on a bearing if you're going to reuse it. Except when you're hammering in the inner race, and the outer race is free, or vice versa. No hammer force through the balls or rollers in other words. That's what pullers are for.

I think there's a major difference in peak forces hammering steel on steel vs. the pounding the wheel bearing gets from a pothole through the tire.

 

[L.Cheapo]

Watch the above video but here is a snap shot (shorter, fatter bolts would be better).



After 6 or 8 turns on each bolt, losen them, turn the rotor about 1/4 turn and repeat. It will leave a mark on the rotor. E Z !

Until you break an ear off the knuckle. Then you get to find out the ball joints are also stuck in the tapers, the suspension bolts are rusted solid, etc.

It does happen.

 

[unslow1]

Until you break an ear off the knuckle. Then you get to find out the ball joints are also stuck in the tapers, the suspension bolts are rusted solid, etc.

It does happen.

That's what I was thinking. There is no way I'm doing that. I've had an ear break off before.

 

[theoldwizard1]

Until you break an ear off the knuckle. Then you get to find out the ball joints are also stuck in the tapers, the suspension bolts are rusted solid, etc.

It does happen.

Then stop being cheap and buy a Astro 78830 Hub and Rotor Puller.

 

[American Locomotive]

If the hammer used for the test had a 2 foot handle, and the typical hammer of that weight has a 1 foot handle, than claiming 90k lbs of force doesnt make sense. It's 90k lbs of force, when the hammer hits. I can get a lot more power with a longer handle, vs. a little handle

My numbers used the speed of the hammer head. The length of the hammer handle is irrelevant. As long as the hammer head achieves the speed I said, it will impart that 90,000 pounds of force into the rotor - no matter if it has a 1" handle or a 100".

A longer hammer handle doesn't necessarily mean more speed of the hammer head. You still need to put that energy into the hammer to swing it, and the human body is only capable of exerting so much energy in a given amount of time.

90k lbs is our hammer hit spec. When the bump-stop bottoms, the effective spring rate is infinite. .... If we ignore the chassis and how it will flex to take impact load, a fully compressed suspension, when receiving more compression force, is equivalent to a metal rod

Bump-stops are still typically compliant rubber. They're very high durometer, but they're still compliant. You also cannot ignore all the "give" the suspension components have, especially in a long duration event like hitting a pothole. When you factor in the give of the tire, the wheel, the suspension bushings, the springs, the bump-stops, etc... you will never see that kind of force in a car suspension in normal driving. If you do, stuff gets ripped off.

90k lbs of force - on a bearing which may be rated to receive 100k every day of its life with no complaints. Without having any information or other specs, 90k lb is a worthless figure. For all we know the bearing sees that every day.

You just have to look up typical tapered rolling bearing specs (granted most new cars don't use tapered roller bearings anymore) to see that no bearing in the typical size for auto applications is rated for 90,000 pounds of load.

The Timken LM12710 is the front wheel bearing for a early 90s F-150:
- For a life span of ~100,000,000 revolutions (this would be 150,000 miles with a 30" tire), the maximum continuous dynamic load is 2250 pounds.
- At 8700 pounds, the life-span gets reduced to 1,000,000 revolutions (15,000 miles).
- The maximum static rating is 7930 pounds.

 

[2ndGearRubber]

So.... that data is irrelevant. Since one would.never hammer off a rotor mounted to a tapered roller bearing hub? Because the rotor and the hub which holds the bearings are the same piece?


A compressed bumpstop is no longer compliant. It has compressed fully, to protect the damper from internally bottoming out. It is now a rigid structure. It cant just compress infinitely.



As I said, ive seen zero evidence of this ever occurring. Plenty of cars hit 150k+ miles with factory wheel bearings and many rotors changed.

 

[JJ99SS]

Whenever I do brakes I coat the entire hub where the rotors sits with anti-seize, next time removing them is certainly easier.

This...

I'm in Texas and stuff just comes off for me. But I still do a light coat of AS as a precaution.

 

[American Locomotive]

So.... that data is irrelevant. Since one would.never hammer off a rotor mounted to a tapered roller bearing hub? Because the rotor and the hub which holds the bearings are the same piece?

It's not irrelevant, it was showing that automotive wheel bearings are not rated for anywhere near 90,000 pounds of force. It was just that particular bearing was very easy to find data on, since vehicles that used tapered roller bearings tend to use standard parts. Modern integrated unit hubs will have similar ratings, but are harder to find information on.

Additionally, many many vehicles have tapered rolling bearings and removable rotors.

A compressed bumpstop is no longer compliant. It has compressed fully, to protect the damper from internally bottoming out. It is now a rigid structure. It cant just compress infinitely.

It will keep compressing until you extrude the rubber out of the sides. Then when the bump-stop bottoms out, you have all of the suspension arms and bushings that will start deflecting. You're neglecting the time aspect of this. It takes time for the suspension to compress. It takes time for that bump-stop to bottom out. It takes time for that wheel to travel over a bump.

The time it takes that stuff to happen is nearly 2 orders of magnitude longer than the impact duration of a sledge into a rotor. The protracted duration of hitting a bump means the peak forces are much much lower.

This is why I can press a shaft out of a pulley with a 10 ton press and the shaft won't get damaged, but if I hammer on it with a 3 pound sledge, the shaft will instantly mushroom. The instantaneous peak force of that hammer blow is orders of magnitude higher than the press.

As I said, ive seen zero evidence of this ever occurring. Plenty of cars hit 150k+ miles with factory wheel bearings and many rotors changed.

...and most cars don't require the rotor to be beaten as hard as you can with a sledge to take them off. How many bearings have you disassembled and checked for brinelling after hammering off a rotor? A bearing that's been damaged by brinelling isn't likely to fail instantly, but it has been compromised and will fail sooner than it would have.

 

[dkroth]

I like Wiha screwdrivers.







.

 

[2ndGearRubber]

It's not irrelevant, it was showing that automotive wheel bearings are not rated for anywhere near 90,000 pounds of force. It was just that particular bearing was very easy to find data on, since vehicles that used tapered roller bearings tend to use standard parts. Modern integrated unit hubs will have similar ratings, but are harder to find information on.

Additionally, many many vehicles have tapered rolling bearings and removable rotors.

It will keep compressing until you extrude the rubber out of the sides. Then when the bump-stop bottoms out, you have all of the suspension arms and bushings that will start deflecting. You're neglecting the time aspect of this. It takes time for the suspension to compress. It takes time for that bump-stop to bottom out. It takes time for that wheel to travel over a bump.

The time it takes that stuff to happen is nearly 2 orders of magnitude longer than the impact duration of a sledge into a rotor. The protracted duration of hitting a bump means the peak forces are much much lower.

This is why I can press a shaft out of a pulley with a 10 ton press and the shaft won't get damaged, but if I hammer on it with a 3 pound sledge, the shaft will instantly mushroom. The instantaneous peak force of that hammer blow is orders of magnitude higher than the press.

...and most cars don't require the rotor to be beaten as hard as you can with a sledge to take them off. How many bearings have you disassembled and checked for brinelling after hammering off a rotor? A bearing that's been damaged by brinelling isn't likely to fail instantly, but it has been compromised and will fail sooner than it would have.

I have wailed on plenty of rotors, as hard as I can, heat/cooling, and air-hammering. This is usually after the puller starts snapping pieces off them. I've used a 10lb sledge with a 3 foot handle.


Never had an issue, ever. The only time I've ever even heard of this as hurting wheel bearings, is on forums. Frankly, I'd be more worried about heat traveling through the spindle and breaking down the grease. Unless we open up a ball bearing hub, and inspect a dozen of them, and mount another dozen to a rotor and hit the rotor, then disassemble them, it's all hearsay.




The vast majority of wheel bearing failures do not occur on vehicles known for either long lasting brakes (infrequent hammering, but more likely to be stuck), or short lived brakes (more frequent hammering, less likely to be stuck). They occur on vehicles known to have crappy wheel bearing specs, leading to more frequent failure. I've put plenty of audi S5/S6 wheel bearings in, with factory rotors still attached. In the absence of hard evidence, and the fact that most automotive wheel bearings last 150,000 miles plus, I do not believe it is relevant. I'm sure there is some effect. In the same way eating bananas increase ones exposure to radiation since they're filled with potassium. Academically, yes. Real world, doubtful.

Unless one has data, it's all conjecture. My data is that I'm not doing enough wheel bearings to imply rotor-hitting has any effect. If there was a large correlation, I'd be pressing bearings all day.





As for suspension compliance, try riding in a drift car with coilovers sitting on the bump stops. You'd swear a pipe would be a better suspension.

 

[theoldwizard1]

Or Big Nasty (tm). There's no match for Big Nasty:

Big Nasty gets DEFEATED ! Another Astro tool to the rescue !!

Not only pulls hubs, but also drums and rotors !

 

[derosa]

I live in Michigan. When working on 4x4 or AWD brakes I use an 8 pound hammer. one hit and they pop off.

Wish my winters were as easy as Michigan's, I used an 8lb hammer for a good hour and had to use the bolt trick at the same time to finally get the front rotors off.

As I said, ive seen zero evidence of this ever occurring. Plenty of cars hit 150k+ miles with factory wheel bearings and many rotors changed.

I'll add to the forum hearsay. My wheels didn't make a sound until after doing the brakes. The pads and rotors needed their first change at 98k miles, within 500 miles of doing the brakes which required repeated blows with an 8lb hammer that left the rotors completely dimpled the front wheel started making some noise. I assumed it was pad rub though resetting the brakes 4 times over the course of the next few thousand miles made no difference. It was only when the wheel bearing was pulled and replaced that the noise disappeared. The balls inside the bearing were noticeably heat damaged and discolored. My online research suggested that a late model Mazda 5 wheel bearing failing before 120k miles was rare as most should make it well past that. Hammering on the rotor would seem to have been the issue.

 

[ovilla]

This is what Chicago winters will do to a 4 year old rotor. Tried an 8 pound sledge, a few cycles of heat (Oxy torch) and water, and a 10 ton 3-arm hydraulic puller. I finally took the knuckle off and used my 20 ton press to push the wheel bearing and rotor out as one piece. New parts went back on easy peasy!

 

[L.Cheapo]

Then stop being cheap and buy a Astro 78830 Hub and Rotor Puller.

You were the one calling the $40 synthetic oil change a "rip off".

With my air hammer I'll have the rotor off, brakes done, and the tire back on before you finish putting your puller together.

 

[Fcvapor05]

It's not irrelevant, it was showing that automotive wheel bearings are not rated for anywhere near 90,000 pounds of force.

Dude just stop. This number you keep throwing around makes no sense. It's a straw man of your own making.

...and most cars don't require the rotor to be beaten as hard as you can with a sledge to take them off. How many bearings have you disassembled and checked for brinelling after hammering off a rotor? A bearing that's been damaged by brinelling isn't likely to fail instantly, but it has been compromised and will fail sooner than it would have.

How many wheel bearings have YOU removed and taken apart to check for brinelling after hammering off a stuck brake rotor?

I'd bet everything I own that the number is zero.

 

[tym]

I also use a good amount of anti-seize on the hub face and that's made it fairly easy to get old rotors off up here in New England.

I also replace rotors whenever I replace pads, so they're never on the car for long.

 

[2ndGearRubber]

Wish my winters were as easy as Michigan's, I used an 8lb hammer for a good hour and had to use the bolt trick at the same time to finally get the front rotors off.


I'll add to the forum hearsay. My wheels didn't make a sound until after doing the brakes. The pads and rotors needed their first change at 98k miles, within 500 miles of doing the brakes which required repeated blows with an 8lb hammer that left the rotors completely dimpled the front wheel started making some noise. I assumed it was pad rub though resetting the brakes 4 times over the course of the next few thousand miles made no difference. It was only when the wheel bearing was pulled and replaced that the noise disappeared. The balls inside the bearing were noticeably heat damaged and discolored. My online research suggested that a late model Mazda 5 wheel bearing failing before 120k miles was rare as most should make it well past that. Hammering on the rotor would seem to have been the issue.

Did you hit both sides with the hammer? Why didn't both front wheel bearing s fail, if you did? Any wheel bearing removed for noise issues is heat damaged and discolored. It's the failure mode, which created the heat. Correlation isn't necessarily causation.

 

[sberry]

Solids like many rears have not so much a problem hammering on them but fronts with webs crack internally.

Not only pulls hubs, but also drums and rotors !

I done hundreds of brakes, do not own one and is still no substitute for a torch. As was noted above usually done before others could get the tools out.

 

[American Locomotive]

Dude just stop. This number you keep throwing around makes no sense. It's a straw man of your own making.

What makes no sense about it? It's f=ma. If your hammer of X mass is going Y velocity, and comes to a complete stop making a dent Z deep, you can easily calculate the force it applied to whatever you hit.

How many wheel bearings have YOU removed and taken apart to check for brinelling after hammering off a stuck brake rotor?

You accuse me of making a straw-man and then your comeback is a tu quoque, attacking me?

I work in industry, we have shelves FILLED with bearings. Everything from plain bushings, ball bearings, thrust bearings, tapered roller bearings to high precision angular contact bearings. Bearings that cost more than what I paid for my car.

I've seen bearings that can handle thousands of pounds of thrust load get destroyed by a single blow from a 16 Oz hammer. I've replaced plenty of bearings others have destroyed by hammering on them - I've replaced bearings I've destroyed myself by hammering on them.

Bearings do not like to be hammered on. Period. The peak force from a 3-pound sledge going full-send is astronomical.

 

[Fcvapor05]

What makes no sense about it? It's f=ma. If your hammer of X mass is going Y velocity, and comes to a complete stop making a dent Z deep, you can easily calculate the force it applied to whatever you hit.

I fully understand the physics, but you're using a velocity you pulled out of a hat, and an impulse time that you can't know, because when you pick those numbers it makes your argument sound really good.

You accuse me of making a straw-man and then your comeback is a tu quoque, attacking me?

I'm not 'attacking' you. It's not personal. You made the exact same appeal in the previous post- it either works for you and for me, or it works for neither of us. You can't have it both ways.

Bearings do not like to be hammered on. Period. The peak force from a 3-pound sledge going full-send is astronomical.

I agree with you fully on this point: "bearings do not like to be hammered on".

But in this particular instance, we're not talking about hammering on a bearing- we're taking about hammering on something that's attached to something else that's then attached to a bearing, while the whole assembly is hanging from some other stuff that's all mounted with compliant mounts. This is not the same as hitting a bearing race with a ball peen hammer.

 

[American Locomotive]

I fully understand the physics, but you're using a velocity you pulled out of a hat, and an impulse time that you can't know, because when you pick those numbers it makes your argument sound really good.

You can determine the impulse time simply by looking at how deep the dent in the rotor is based on the initial starting speed of the hammer. I chose the speed and dent-depth as conservative "real-world" values to give as an EXAMPLE of the sort of forces that can be achieved with a simple hammer. The harder the rotor material, the shorter the impulse duration and the higher the peak forces.

But in this particular instance, we're not talking about hammering on a bearing- we're taking about hammering on something that's attached to something else that's then attached to a bearing, while the whole assembly is hanging from some other stuff that's all mounted with compliant mounts. This is not the same as hitting a bearing race with a ball peen hammer.

The shorter the impulse duration, the less all that compliance matters. It's why things like dead-blow hammers exist. They increase the impulse duration to drop the peak force, while still transferring the same amount of energy into an object. When you slam that 8 pound sledge into a rotor, you're delivering all of that energy in about ~1/10,000 of a second. The peak forces you exert through the rotor, into the wheel hub are enormous.

Bearings are a solid 20% of my job. I deal with them almost every single week. I've replaced bearings that are 2x the size of your average car bearings just because someone beat on a spindle with hammer. We're talking a single bearing capable of handling over 10,000 pounds of load, and there's 4 of them in the spindle! A bearing package that you could literally hang two school buses off of was destroyed by a hammer.

I'm not 'attacking' you. It's not personal. You made the exact same appeal in the previous post- it either works for you and for me, or it works for neither of us. You can't have it both ways.

My argument was that he can't possibly know he's not causing damage without taking them apart. Your counter was how could I be sure that hammering on them is causing damage if I've never taken them apart. You're trying to invalidate my statement by claiming some sort of hypocrisy on my part. What I have, or have not done does not make my statement untrue.

If you want to keep beating on your rotors with a sledge - go ahead. I'll admit I sometimes hit stuck rotors too, but I don't pretend I'm not damaging the bearings. A 16 Oz hammer likely won't hurt them, but a 3 pounder may, and an 8 pound almost certainly is. Wheel bearings are low speed, and it may take a long time for brinelling damage to manifest itself. It could even be tens of thousands of miles. It may mean your wheel bearing only goes 170,000 miles instead of 300,000.

 

[MattT]

What makes no sense about it? It's f=ma. If your hammer of X mass is going Y velocity, and comes to a complete stop making a dent Z deep, you can easily calculate the force it applied to whatever you hit.

You can calculate, or maybe estimate, the peak force at the point of impact. The force lowers the further you get from that point because the mass and elasticity of the assembly reduces the peak deceleration. When you hit the end of a shaft why is it only the end that deforms?

And FWIW I agree that hammering on rotors does carry some risk. But is it really worth taking extra time, or employing equally risky methods such as heat, to avoid it? Hammer size also comes into play here. A few love taps with a 3# engineers hammer isn't likely to hurt anything. If that doesn't work and you start eyeballing the sledge it might be time to stop hammering and try something else.

 

[American Locomotive]

You can calculate, or maybe estimate, the peak force at the point of impact. The force lowers the further you get from that point because the mass and elasticity of the assembly reduces the peak deceleration. When you hit the end of a shaft why is it only the end that deforms?

Very true, and valid points.

And FWIW I agree that hammering on rotors does carry some risk. But is it really worth taking extra time, or employing equally risky methods such as heat, to avoid it? Hammer size also comes into play here. A few love taps with a 3# engineers hammer isn't likely to hurt anything. If that doesn't work and you start eyeballing the sledge it might be time to stop hammering and try something else.

There's always a time and place for a hammer. Some mild tapping with a hammer is fine. If you get to the point where you're denting the rotor, it's time to come up with another approach.

I like using heat. Most wheel bearings already have high temp grease and seals since it's not uncommon for brake rotors to hit 600+ degrees after a panic stop.

 

[Fcvapor05]

You can determine the impulse time simply by looking at how deep the dent in the rotor is based on the initial starting speed of the hammer.

You could if the rotor face was monolithic, which it isn't.

The rotor face is a thin plate. In order to actually calculate what you're trying to calculate, you'd need a lot more information about the rotor which you don't have.

 

[nicks78camaro]

I live in PA, we get plenty of stuck rotors. Just smack the rotor off with a big hammer. If it's really stuck it'll come off in pieces. Then install new rotor and move on.

 

[theoldwizard1]

You were the one calling the $40 synthetic oil change a "rip off".

Which is why I use the two bolts method !

 

[sberry]

I use a big torch tip that heats fast, heat between studs and get it off before it really heat soaks. I almost cant imagine doing much real work on cars without a torch especially in our climate.

 

[PoorOwner]

hey guys.. I was thinking more about this, isn't the bearing inner race clamped by an axle end on the inside and axle nut?

So when the hub is taking some hits (which is pressed into the inner race), the axle nut does help hold the hub and bearing together?

 

[Steve_P]

Whether you hit the rotor from the outside or inside, you're still impacting the bearing - whether it's ball bearings or tapered bearings. I do it too, but there's no free lunch.

 

[arms1970]

I live in Phoenix, what is this rust you speak of?

Cant wait to move out there and never deal with rust and cold again