I had a flat changed the other day. The car was in “Park” and the parking brake (i.e.: emergency brake) was engaged. The man loosened the lug nuts without the jack in place, which is typical, and then he jacked up the car and proceeded to change the tire. OK.
But, before releasing the jack, he proceeded to tighten the lug nuts all the way (yes, beyond hand-tight) with the wrench! The tire started turning with him, slightly, at some point as he was cranking down on the lug nuts. He said I should have my brakes checked because the tire shouldn’t be turning with him. However, from past experience, I’ve never seen anyone tighten the lug nuts (beyond hand-tight) BEFORE releasing the jack for this very reason, or so I assumed!
Was his method correct, and likewise is his reasoning correct?
Is this a valid reason to have the brakes checked? - Jinx
It is nearly impossible to know how hard he turned the lug nuts. You are correct that this is not the usual way to change tires.
The parking brake may not be fully on - and even if it was pulled as far as it could go, this could simply mean that the cables are out of adjustment. The cables are not used in normal braking - they’re simply what connects the parking brake handle to your brakes.
On many cars, usually those with rear disc brakes, the parking brake is actually a completely separate brake sharing no components with the regular brakes whatsoever. If that is the case, the test says nothing about your regular brakes.
You haven’t noticed anything else wrong with the brakes, have you?
At best, this “test” may show that the parking brake alone may not be grabbing completely and you shouldn’t leave the car parked on a hill with the transmission in Neutral, something you shouldn’t do anyway. It could also indicate that the guy who did this is either not the sharpest knife in the drawer, or trying to sell you a brake job. I would not worry about the brakes failing because of this.
I was always taught to lower the car before going beyaon hand tight. I wouldn’t say that the brakes need ajustment/ replacement from that but maybe worth a look.
When tightening a lug nut, at least on the Driver’s side, you’re turning the tire “backwards”, as if the car were rolling to the rear. Drum brakes are what’s known as “self energizing”- as in the leverage of the pad as dragged by the drum in the normal direction of rotation, actually adds to the force that presses the pad to the drum.
That same effect also works in reverse- it reduces gripping power while turning in the opposite direction.
This has a considerable effect on the gripping power of the brake- my old shop truck, a '92 454 Chevy Dually, would back up without a care in the world even with the P-brake engaged to the full extent of the pedal travel. But as soon as I threw it in a forward gear, it’d stop dead- no amount of throttle would get it to move.
So basically, assuming it was a Driver’s side rear, and that it has rear drums (not certain but statistically likely) then I’ll further assume that you didn’t stand on the P-brake pedal (or hand lever) with all the force you could muster, so no, no big deal. It wouldn’t take much leverage to manage to turn it while tightening.
If you’re worried though, most places like Midas will do a free brake inspection.
With a non-positive traction differential in a rear wheel drive car, as long as one drive wheel can turn, the driveshaft can keep turning. So, you can jack up one drive wheel in such a car and put it in gear with the engine running and, as long as the one jacked up drive wheel can spin in the air, the car’s not going anywhere.
For the record, yes! It was the driver-side rear tire. It’s a Honda CR-V. Not sure if it’s “posi-traction” or not. The CR-V also has real-time 4 wheel drive which, supposedly, is controlled by a microprocessor. When it detects slippage, the four-wheel drive feature is supposed to engage. However, with the engine off, I don’t know if there’s still some mechanical device still at work here sensing (mechanically) that the jacked-up tire seems to be slipping.
I agree with MadScientistMatt. Satisfy yourself that the parking brake works well. If it does, you’re done. If it doesn’t, it’s not a bad idea to get a professional evaluation.
If the parking brake holds the car against rolling, forwards and backwards, on a steepish hill, I’d say it’s adequate. If it holds in both directions against moderate attempts to drive the car off, it’s working great.
It was more than adequate. The power available to make the truck move was many times the gripping power needed to simply keep it from rolling away. That 454 had gobs of torque- I used to tow a three-axle 17,000-pound gooseneck with it.
I guess I did miswrite that- The truck didn’t back up as if there was ‘no brake at all’, rather it backed up with minimal apparent drag. I tended to forget to release the P-brake until I went to move forward.
On flat, level ground, a typical person can push the truck by hand. The engine has the power to get it to 60 MPH in about fifteen seconds.
The wheel turning in park kind of bugs me though. I’m not familiar with the Honda’s “active traction” 4WD, but in a standard RWD differential, if one tire’s on the ground and the tranny is in “park”, that raised wheel really shouldn’t do anything more that wobble a bit from the slop in the system. Yes, it’d turn if the other tire was off the ground, or if the driveshaft were free to spin (in neutral) but any open, posi or locking diff won’t let it turn if it’s the only wheel “free”.
(On the other hand, if you jacked up one wheel with an “open” diff and then put it in gear, all the power would go to the lifted tire. A Posi would redirect some of the power to the down tire, and a locker would put equal power to both, regardless of traction.)
I wonder if what passes for the “transfer case” in the system uses one of those “viscous couplings” with the electrohydralic fluid… In this case, the normal bias would probably be to the front tires, with the rears engaged for high-traction-demand situations. And so the rear driveshaft could turn slightly, as the fluid wasn’t energized.
And another thing - any time you see a mechanic tightening your lug nuts with an air wrench, car on the jack or off, start looking for another mechanic. Lugnuts should be tightened with a torque wrench to the values in the service manual.
Anal retentive? You tell me the next time you have to change a flat in the rain and the last person to install your wheels was some monkey with an air-wrench set to 200 lb/ft of torque. Been there.
This is especially important on drum-brake cars (older) where excessive torque will distort the drums and cause brake pulsing.
any time you see a mechanic tightening your lug nuts with an air wrench, car on the jack or off, start looking for another mechanic.
That’s a bit extreme. A good mechanic can use an impact wrench properly on steel wheels without overtightening.
It is a problem if the wrench is on a high setting for every car. Most vehicles’ steel wheels can be correctly tightened with the wrench on a low setting. An intelligent mechanic will adjust the impact wrench appropriately for the vehicle at hand.
Alloy wheels should not be tightened with a regular socket on an impact wrench. If a mechanic does this, he’s an ignoramus, and yes, I’d find another mechanic.
The ideal method for tightening alloy wheels is by hand with a torque wrench. Some mechanics use “torque sticks,” which are special torque-limiting sockets (they’re 8-10 inches long, hence the name). There’s some controversy in the trade as to whether they are reliable in applying the correct torque. From what I’ve read, there don’t seem to be problems if the air supply pressure is relatively constant, the correct torque stick is used, and the impact wrench setting is appropriate. Personally, I don’t trust them, but some shops have been using them for years with no known problems. Still, if you request your alloy wheels be hand-torqued, I would expect the shop to comply, and would go elsewhere if they didn’t unless they could satisfy me that they KNOW (not think, KNOW) that they’re achieving the correct tightness with the torque sticks.
What I find amazing is the number of mechs that will use brake scare tactics. Monday I had a flat repaired.
Mechanic: “You’re back brakes are shot!”
me “Huh?” ( I’d replaced the pads last fall)
Mechanic:“Yeah, the disks are all scored and they’re about to fail”
me “Can you show me?”
mechanic takes me to the car which is up on a rack shows me the scoring on the rotor. The rotors were scored slightly when I replaced the brakes this fall, but it was well within spec and I hate to rurn rotors unless they’re actually warped.
me “so, I should replace the pads?”
Mechanic:" Yeah, we can do that for you right here if you like"
me (pulling out a pocket rule and a flashlight)“so, how far down should I let them get?” (Pointing to the 5/8" of pad clearly remaining)
Mechanic:" Well, something has to be wrong, they rotors are scored"
me “I replaced the pads and left the rotors alone, as the amount of scoring is within the max allowed. They’re not warped, they run true, and the little scoring (which was rapidly disapearing anyway) has no effect on braking.”
Mechanic: (acting as if he’s just run across a smartass) “Well, you must know better than an ASE certified mechanic then”
Me (showing the mech my ASE card) “Oh, you mean like this?”
he walks off in a huff and another counterperson takes my cash for the tire repair.
People are such nimrods. What GaryT said is right, test your car, or have a qualified mechanic look at it, and don’t worry about what someone does to try to scare you.
Billy you’re a smart ass. Reminds me of, well, me. I just love doing that. Or handing him my business card that has the name of the car company on it and the title “Technical Training Instructor” and asking which one of us does he think knows more about the subject at hand?
