Hammering off rusted rotors

[PoorOwner]

Is this commonly done at professional repair shops and dealerships?
I see Astro made a rotor puller recently but I didn’t think it was a very common tool before.

I asked because I had to swing a 3 lb hammer moderately hard but that is also the same action to remove the hub and part of the race from the wheel bearing with a slide hammer.
Just wondering if this shorten or already damaged the wheel bearing.

 

[Handyandy23]

Hammering a rotor is definitely a common thing. But like anything I think there's a smart way to do it and a stupid way. If you hit around the edge of the top hat part of the rotor in a circular pattern around and around, it will usually loosen it. And that seems to have a lot less of a jarring effect on the hub than beating the other edges of the rotor.

Some rotors also have threaded holes in the top hat to thread a bolt through to drive against the hub and separate the rotor.

Unless you're being a fool I can't see any of this damaging a wheel bearing. If the bearing is already starting to fail / has slop in it, you have to change it, there's no way around that, or worrying about making it worse.

I have that Astro hub and disc puller though and it's very slick, well worth the money.

 

[mrjaw14]

What you could maybe do is take a hammer, use an air hammer if you have one, and hit the rotor on the outer side between the wheel studs where it would contact the hub. This is to break the rust between the rotor and the hub. so that way you're not hammering it off, you're breaking loose what's holding it on. If you're concerned about damaging a wheel bearing that might be less risky.

 

[Locker537]

Hammer on the rotor where it contacts the hub, as mrjaw14 explains.

Then hammer on the rotor braking surface.

You need to get it off. In areas where they salt the road, it can take some serious force.

 

[2ndGearRubber]

Standard operating procedure. Pullers come out for stuff that's seized onto the hub. Living in the rust belt means those little m8 threaded holes are worthless.

Wheel bearing is fine, I cant imagine how much you'd have to wail on one to damage it.

 

[knobby]

It would take a hell of a hit with a 3LB hammer to be near the impact that the wheel bearings take when the car rolls over a pothole at 60MPH. JS.

 

[tonyciambrone]

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

I use a big fricking dead blow most the time. 8LB sledge if not.

Gotta love road salt

 

[L.Cheapo]

I used to use a hammer. Then I got an air hammer. It makes quick work of stubborn drums and rotors.

 

[Sam'sAutoParts]

I do it anytime I do brakes, they are always seized. I’m not sure I would try the bolts on the caliper mounts, with my luck I snap one off and be really SOL. Check out South Main Auto on YouTube. Eric O has to get pretty creative sometimes to remove rotors.


Sent from my iPhone using Tapatalk

 

[mautotech]

I would NEVER hammer on a rotor. I've seen too many bearings damaged from people hammering on them. No reason to risk damaging a bearing when you can use the puller holes or a puller to get it off.

 

[MikeF2316]

I find a pry bar between the caliper mount and rotor, then a good yank and off they come. Sometimes you need to spin the rotor/hub a half turn and repeat.

 

[jsmeece]

This past winter I had to replace the front rotors on my wife's Toyota Rav4. Tired a sledge, they would not budge. Tried a three arm 10 ton puller, that did not work either other than busting pieces of the rotor off. I had to use a propane torch, heated it up and let it cool and two wacks with the sledge and it come off. Sometimes heat helps GREATLY. The rotor was rusted on and salt from winter roads did not help either. The passengers side was the worse to get off.

 

[Basswrangler]

If it needs hammered it needs replaced and hub needs cleaned and inspection

 

[dnschmidt]

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

 

[2ndGearRubber]

I would NEVER hammer on a rotor. I've seen too many bearings damaged from people hammering on them. No reason to risk damaging a bearing when you can use the puller holes or a puller to get it off.

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

I assume you have the same location as dnschmidt?




What's the logic behind hitting a rotor with a 3lb sledge causing wheel bearing failure? Maybe tapered roller bearings? Maybe. But those incorporate the rotor as the bearing housing. Imagine the force at 60mph when the tire hits a highway expansion joint while changing lanes. 3000lb+ car, 20lb+ of unsprung rotational mass, axial load as the bearing travels at an angle across the joint, and is raised upwards by an inch, in a distance of 1 inch, then falls back down.

A 12 inch handled 3lb sledge is nothing.

 

[ericlar80]

Use an air impact hammer, not a regular hammer. They quick, small impulses will break it loose easily. I usually do it near the center of the rotor.

 

[dnschmidt]

2ndGearRubber, You're kidding right? Prior to moving to Phoenix I lived in the Bloomfield section of Pittsburgh for 41 years. The least of your problems is an expansion joint when you've got potholes big enough to swallow a Volkswagen. Expansion joint ha, ha, ha,. Now that was funny. The funniest thing is that on Baum Boulevard, where they have Mercedes, BMW and other high end dealerships the road is worse than any that can be found in any third world country. Take you're brand new Beamer off the lot and break a rim before you drive a mile. God, how I miss Pittsburgh, NOT.

 

[bobcatdan]

My record is four pieces on a F150 rotor.

 

[zendriver]

Spray the stuck area with pb blaster, then whack firmly, circling around the rotor, with a dead blow hammer.

Not that difficult.

 

[Fcvapor05]

If you think you can damage a wheel bearing on any modern car with a 3lb sledge, you should buy a cape and tights and start fighting crime.

 

[seagull369]

Not to offend, but did u look to make sure there isn't a screw holding the rotor on? What I usually do to get a really stuck rotor off is take the caliper and bracket off (hang with wire and out of the way), put wheel back on lugs finger tight, keep wheel off the ground, grab a block of wood 2X4ish about 3 ft long or so, span it between the outer half of rim and end of tire. Get a long *** sledge and aim right at the outer part of rim where tire bead is. If doesn't loosen on 1st blow, spin wheel around 1/4 turn and whack again. Keep repeating until it's breaks loose. Works every time, and never caused any wheel bearing, tire or anything else damage. BTW, doing any kind of prying is a just bad idea. Any hammering on the brake pad area of the rotor (front or back) also a bad idea if you're planning on re-using rotor. You can try hammering on the face of the rotor in between the lugs, also, just make sure you have good aim =).

 

[ItsNemo]

LoL to all those saying they come off easy...pb blaster does nothing, dead blows do nothing, air hammers (even my IR 118) do nothing, even hammering on the hub area isn't the most effective. Pretty well up here, you're using a small sledge on the back of the rotor face and a dozen or more full swing hits to get them off.

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

 

[seagull369]

+1 on the antiseize. If it's an aluminum rim, I usually wire brush the back side of it then add it there, too. Antiseizing CV axle splines is also a great idea,

LoL to all those saying they come off easy...pb blaster does nothing, dead blows do nothing, air hammers (even my IR 118)

Get a CP 717 Zip gun, then get back to me.

 

[ItsNemo]

+1 on the antiseize. If it's an aluminum rim, I usually wire brush the back side of it then add it there, too. Antiseizing CV axle splines is also a great idea,



Get a CP 717 Zip gun, then get back to me.

Come to Canada, then get back to me.

 

[ClappedOutBport]

Not to offend, but did u look to make sure there isn't a screw holding the rotor on? What I usually do to get a really stuck rotor off is take the caliper and bracket off (hang with wire and out of the way), put wheel back on lugs finger tight, keep wheel off the ground, grab a block of wood 2X4ish about 3 ft long or so, span it between the outer half of rim and end of tire. Get a long *** sledge and aim right at the outer part of rim where tire bead is. If doesn't loosen on 1st blow, spin wheel around 1/4 turn and whack again. Keep repeating until it's breaks loose. Works every time, and never caused any wheel bearing, tire or anything else damage. BTW, doing any kind of prying is a just bad idea. Any hammering on the brake pad area of the rotor (front or back) also a bad idea if you're planning on re-using rotor. You can try hammering on the face of the rotor in between the lugs, also, just make sure you have good aim =).

I once had on that was pretty stuck when the others came off easy. I beat the snot out of it, a lot of medium hits, nothing hard, and it finally came. I then realized I forgot to take the screw out. So it's not a bad question.

 

[Super Mech]

Penetrating oil, lots of vibration between the studs from a .404 air hammer. Usually that works but sometimes will still need some hammering from the backside. When that fails I breakout the .498 air hammer and hit it between the studs. Lots of times the vibration is so intense that it backs the wheel studs out of the hub. I’ve done this probably hundreds of times on regular customers cars and I don’t recall any wheel bearing failures within a reasonable amount of time from doing the brake job.

 

[American Locomotive]

What's the logic behind hitting a rotor with a 3lb sledge causing wheel bearing failure? Maybe tapered roller bearings? Maybe. But those incorporate the rotor as the bearing housing. Imagine the force at 60mph when the tire hits a highway expansion joint while changing lanes. 3000lb+ car, 20lb+ of unsprung rotational mass, axial load as the bearing travels at an angle across the joint, and is raised upwards by an inch, in a distance of 1 inch, then falls back down.

A 12 inch handled 3lb sledge is nothing.

It's the same reason why our machine tools can exert thousands of pounds of tool pressure through the spindle without a problem, but you'll instantly destroy the bearings if you hammer hard on the main spindle.

First: Bearings do not enjoy static loads (as in when the bearing is not rotating). It's common for a roller bearing to have 2-3x more dynamic (spinning) load capacity compared to when it's stationary.

Second: Car suspensions are very compliant, sure there's a lot of force, but it's being spread over a large time period. You have the tire, springs, and even the large wheel cushioning everything.

In comparison, a hammering on a rotor delivers all of that energy in a very small area in a very, very short amount of time. Here's a pre-made example I found: If you swing a ~5 pound hammer at 44 MPH into a rotor and it leaves a 1mm dent in the iron, it would have exerted 90,000 pounds of force momentarily into the wheel bearing.

It basically comes down to time. A car hitting a 6" long bump in the road at 60 MPH has ~0.006 seconds for all that energy to do its thing. That hammer is doing everything in .0001 seconds. That pot-hole has 60x the amount of time to do whatever it needs to do, meaning the peak force is much lower.

 

[sberry]

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

 

[DaveInPhilly]

Yep, if the deadblow doesn't do it and you have to break out the metal sledge your ears will ring for the rest of the brake job.

 

[mengel]

I fought this issue on my 81 ****** once. I just hack sawed through the rotor and wedged various items in the cut and it came off easily. The cutting time was trivial.

 

[PMD1966]

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

 

[ItsNemo]

Yep, if the deadblow doesn't do it and you have to break out the metal sledge your ears will ring for the rest of the brake job.

I use hearing protection....muffs are easy to throw on for a few hits.

 

[dsimatt]

BFH on the surface for max leverage in popping it loose, I dont put rotors that rusted back on.

 

[exmaxima1]

Deadblow works for me.

 

[Tonyuk]

Are you replacing the rotor?

If so then i use a decent sized ball peen on the back side, so what if you chip a bit off. Comes off in about 3-5 hits.

If your replacing it then an air hammer on the hat.

 

[plinker]

I've found if you air hammer on the hat and spray some oil around the studs the oil will wick in when the air hammer is rattling it. Just move the air hammer around some so it doesnt hit in one place all the time. Typically pops loose pretty quick. 3lb hammer works well enough too. Antiseize is your friend.

 

[2ndGearRubber]

It's the same reason why our machine tools can exert thousands of pounds of tool pressure through the spindle without a problem, but you'll instantly destroy the bearings if you hammer hard on the main spindle.

First: Bearings do not enjoy static loads (as in when the bearing is not rotating). It's common for a roller bearing to have 2-3x more dynamic (spinning) load capacity compared to when it's stationary.

Second: Car suspensions are very compliant, sure there's a lot of force, but it's being spread over a large time period. You have the tire, springs, and even the large wheel cushioning everything.

In comparison, a hammering on a rotor delivers all of that energy in a very small area in a very, very short amount of time. Here's a pre-made example I found: If you swing a ~5 pound hammer at 44 MPH into a rotor and it leaves a 1mm dent in the iron, it would have exerted 90,000 pounds of force momentarily into the wheel bearing.

It basically comes down to time. A car hitting a 6" long bump in the road at 60 MPH has ~0.006 seconds for all that energy to do its thing. That hammer is doing everything in .0001 seconds. That pot-hole has 60x the amount of time to do whatever it needs to do, meaning the peak force is much lower.

What's the actual peak force on the bearing from the pothole? You listed nothing for that. 90000lbs for a thousandth of a second. Okay, what does that compare to? 5lb hammer is basically twice the weight we are discussing anyways, 3 lb hammer. How long is the handle? That changes force as well. I can buy 45mph, I could throw a baseball like 30 in middle school.

Suspension will do nothing to damp the force from a pothole into the wheel bearing. Tire will be the only thing helping there. That, and very small deformation of the wheel, which transmits the force upward into the bearing via the studs.




No one has ever presented data or tear downs of bearings supposedly damaged by this. It's a forum myth, plenty of silly things get repeated because joe-bobs cousins friends uncle needed a wheel bearing once.

 

[unslow1]

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

I've had to resort to the torch a few times. I've never had that fail.

 

[American Locomotive]

90000lbs for a thousandth of a second. Okay, what does that compare to? 5lb hammer is basically twice the weight we are discussing anyways, 3 lb hammer. How long is the handle? That changes force as well. I can buy 45mph, I could throw a baseball like 30 in middle school.

It's 90,000 pounds for 1/10,000 of a second. It doesn't "need" to compare to anything. It just means that the bearing will experience 90,000 pounds of force being applied to it. If 90,000 static pounds of force can damage the bearing, then 90,000 pounds for 1/10,000 of a second will also damage the bearing. Handle length really has nothing to do with anything in this situation. It's purely momentum and f=ma.

Suspension will do nothing to damp the force from a pothole into the wheel bearing. Tire will be the only thing helping there. That, and very small deformation of the wheel, which transmits the force upward into the bearing via the studs.

The suspension allows the wheel bearing to travel. The more the wheel bearing travels relative to whatever is happening on the road, the less peak force it will experience. There's way too much parameters to estimate the peak force on a car's suspension when it hits a bump.

No one has ever presented data or tear downs of bearings supposedly damaged by this. It's a forum myth, plenty of silly things get repeated because joe-bobs cousins friends uncle needed a wheel bearing once.

Look up bearing brinelling. Brinelling a bearing doesn't mean instant failure - especially a on low speed bearing like a wheel bearing.

 

[2ndGearRubber]

It's 90,000 pounds for 1/10,000 of a second. It doesn't "need" to compare to anything. It just means that the bearing will experience 90,000 pounds of force being applied to it. If 90,000 static pounds of force can damage the bearing, then 90,000 pounds for 1/10,000 of a second will also damage the bearing. Handle length really has nothing to do with anything in this situation. It's purely momentum and f=ma.

The suspension allows the wheel bearing to travel. The more the wheel bearing travels relative to whatever is happening on the road, the less peak force it will experience. There's way too much parameters to estimate the peak force on a car's suspension when it hits a bump.

Look up bearing brinelling. Brinelling a bearing doesn't mean instant failure - especially a on low speed bearing like a wheel bearing.

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. If I'm accelerating the hammer at X feet/sec, and the arc is longer, it will increase the momentum (EDIT: Force) of the hammer. Same theory as the outside of a record spinning faster than the inside - same distance in the same time, it has to be going faster. Maybe the average guy on jack stands can't reach that speed with a 1 foot handle, 3lb sledge?


90k lbs is our hammer hit spec. When the bump-stop bottoms, the effective spring rate is infinite. Stock class auto cross cars with the "stock class" packages from the factory used that trick. Basically ride on the bumpstops, when the bumpstop fully compresses, infinite spring rate for those hoosiers. The average car has what, 350 in/lb springs in the front, max? When the suspension is fully compressed, you have no suspension, all force transfers through the suspension/bearing, and into the strut tower. 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



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. It's like when a politician brags about eliminating a million dollars of "wasteful spending". Impressive number, right? The critical context, omitted of course, is that this is 1% of 1% of the discretionary budget, which is like 30% of the full federal budget. 90k pounds has zero context.