That's a wonderful question but it has nothing to do with how the 2 ramps work. And I would recommend trying to drive a 3000 lb car up a cable even if it is rated at 5000 lbs. The difference between your example and the ramps is yours is designed to fail and the other is designed to work. A better analogy would be 2 dixie cups stacked together will support more weight than one alone.
-jim
Here's the procedure for rotating tires recommended by the book "Auto Upkeep - Basic Car Care":
Put on your safety glasses.
Check the owner?s manual for recommended tire rotation patterns.
Remove wheel covers if applicable. Check the owner?s manual for procedure. Some covers (hubcaps) have locking mechanisms that need to be removed first.
Loosen lug nuts one complete turn with a lug wrench, but no further.
[The Camry manual says to loosen one-half turn (not much of a difference.)]Use jack and jack stands (or an automotive lift) to raise and support the vehicle.
Note the position of each tire.
Remove the lug nuts on each tire.
Remove each tire and move it to the new location according to the owner?s manual recommendations.
Apply anti-seize compound to the wheel stud threads.
[Built_Well's note: The above step sounds counter-intuitive to me. The manual says not to put oil or grease on the wheel's nuts and bolts because it can result in over-tightening with a wrench, and also result in the nuts loosening over time. I believe "wheel stud threads" refers to the wheel's bolts, and you screw the lug nuts onto the bolts. So it doesn't sound right to put anti-seize here. Maybe putting anti-seize on the hub and wheel mounting surfaces is okay, like Ray says, but on the bolts?!] [Here's the exact wording from the manual: "Caution. Never use oil or grease on the bolts or nuts. The nuts may loosen and the wheels may fall off, which could cause a serious accident."]Start all lug nuts by hand. Do not cross-thread nuts.
Spin the nuts on with a lug wrench and snug. Use a star pattern when tightening lug nuts.
[The manual says to "reinstall all the wheel nuts finger-tight" while the car is in the air.]Do not use a pneumatic wrench at this time.
Lower the vehicle /just/ until the tires touch the ground.
[Why not lower the car completely at this point, as recommended by the Camry manual?]Check the owner?s manual or specification?s chart for torque recommendations.
Use a torque wrench or color-coded torque sticks with an impact wrench to tighten the lug nuts on each wheel. When tightening, use a star pattern.
Failure to torque wheels may result in warped brake rotors. Under-torqued wheels may allow the wheel to work loose and come off when driving, causing a hazardous situation.
Completely lower the vehicle.
Recheck all lug nuts with the torque wrench.
Replace wheel covers.
Clean and put away all tools.
A bolt is a threaded shaft with a head to provide a place to tighten. A stud is a bolt without a head.
You should not put anti-seize on the studs.
If the lug nuts are only finger-tight or snug, the wheel may not be seated properly. The Camry's manual assumes that the owner is smart enough to make sure that the wheel is properly seated before lowering.
Well, Anti-seize isn't really a grease per se, it's there to make a rust-resistant film. In My Opinion it's far better that the lugs don't rust solid to the studs, than to possibly back off - you aren't putting any anti-seize on the conical seating/clamping face of the lug nuts, so they should have sufficient friction to stay locked in place.
Use a TINY dab of nickel-based anti-seize on each stud, maybe 1/4 to
1/2 a water drop in size. Fill in two thread notches for 3/16" to 1/4" wide. The stuff goes a long way, if in doubt use less.Trust me, if the lugs do get loose you'll feel a problem long before it gets bad enough to where the wheel will fall off the car.
If I was really paranoid, I would go get some regular hex nuts with the right threads (or some of the special skinny jam nuts if you can find them) and put them on after torquing down the regular lug nuts. But some vehicles would require longer studs, and that won't work on mag wheels with exposed nuts.
That, or get side-drilled lug nuts from an aerospace supply and lace them in position on the wheel with safety wire after torquing.
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Anti-seize compound is not considered to be an oil or grease, even though it may be a petroleum distillate. There are many compounds made from petroleum that are used to remove oil or grease.
Ever since a shop broke a wheel stud trying to get a flat tire off my car in Fla. I have used oil or grease on my wheel studs for easy removal.
Once burned twice shy so to speak~!
In 50 years , I have NEVER ~! and I mean NEVER~!!!!! had a problem with wheels becoming loose after applying grease or oil to the wheel studs..
What it did do ? was make it MUCH easier to remove a wheel when on the road with a flat tire.
This is my personal experience with the use of lubricants on wheel studs.
However , today ? I get the wheels rotated every six months so theres no chance of the studs rusting tight.
I hope the shop fixed the wheel stud free of charge? It sounds like they informed you of their boo-boo, which was honest of them.
Anti-seize contains petroleum distillates, according to the bottle I saw at O'Reilly. It's neat-looking goopy stuff, but I don't think I'll be using it on the hub and inner wheel mounting surfaces or the bolts since it's not mentioned in the Camry manual.
This is what the manual actually says about the hub and inner wheel interface:
"Before putting on wheels, remove any corrosion on the mounting surfaces with a wire brush or such. [The manual actually has a picture showing a rag being used to wipe the hub and wheel surface, not a wire brush--I'll probably stick with a soft rag.] Installation of wheels without good metal-to-metal contact at the mounting surface can cause wheel nuts to loosen and eventually cause a wheel to come off while driving." [Page 274]
Having a wheel come off may be an extreme and unlikely occurence, but I think somebody may have said that a corroded hub-wheel interface could lead to tires that won't stay balanced.
I'm in So Cal so I don't worry about rust much, but if I was in the snow belt I'd give the hubs and the back side of steel wheels a quick shot of High Heat Barbecue Paint when new, and whenever worked on, to keep the wheels from rusting to the hubs.
You don't put on thick paint that could make the rim sit on the hub cockeyed. The paint is going to wear through at the clamping contact points eventually, you want to keep the /other/ areas from rusting.
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Why do you only tighten the lug nuts finger-tight while the car is in the air, and wait until it is lowered to tighten them to their final torque? I always tighten them to their final torques (in a star pattern) while the car is in the air, and I know that when the car is on the lift at the service centre, they do the same.
If the wheel is not in contact with the ground, tightening the lug nuts with a wrench just spins the entire wheel. if you have an impact gun, this is not a problem.
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When it comes to tightening the wheel's lug nuts, the main difference between what the Camry manual recommends and what the book "Auto Upkeep" says concerns when to tighten the nuts completely with a wrench. "Auto Upkeep" says to completely tighten after you lower the wheels so the tires /just/ barely touch the ground but before the car is completely lowered. The Camry manual says to lower the car completely first.
You'd have to read closely to discern the difference.
Oh, thanks. I always put the parking brake on and have the transmission in park, so my wheels don't spin.
That may work in a vehicle with front wheel drive, but for a rear wheel drive vehicle, the front wheels will spin unless you have to have someone inside the vehicle to apply the brakes.
Oh sorry, I was reading this in a Camry newsgroup - all our cars are FWD.
Why should it be free of charge?
The correct reason is that the car cold fall off the jack or stands if you try and tighten it in the air. This is not a problem if the car is on a professional lift.
In either case, it is a safety issue. Do not tighten while the car is in the air.
Mark A., I know it's not safe to tighten lug nuts to their full torque while the car is in the air. That question was asked by "Nobody Important." It was not asked by me.
But I see you didn't attribute the question to him when you quoted him in your earlier message.
Mark A., you're quite a sly little fellow.
To me, the risk of putting the tire on in a cockeyed way because it made contact with the ground crooked exceeds the risk of the car falling on me while I tighten the lug nuts. I block the diagonally opposite wheel and apply the parking brake, and I use a high-quality hydraulic jack with a wide footprint. I also make sure my appendages are not under the car as I work.
Honest men can differ on this point, though.
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Sure, we can differ on this point. I'm just saying that both the Camry manual and "Auto Upkeep" instruct to fully tighten the lug nuts after the car is completely lowered (in the case of the Camry manual) or the tires are lowered to the point of just barely touching the ground (in the case of "Auto Upkeep").
Apparently the "Auto Upkeep" author thinks there's some advantage to fully tightening the wheels while the car is not completely lowered.
I'm not sure what Auto Upkeep's logic is, but both the Camry manual and "Auto Upkeep" instruct not to fully tighten the wheels while the car is way up in the air.
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