Car lift using suspensions as lift points

[jake jot]

Some car lift service centers want to lift up the car by using the suspensions. I always told them to lift by the pinch weld jack points near the tires. Are there some suspension system where the service center can lift the entire car by via the suspensions. And are there some cars which they can't?

 

[Lnewqban]

Each manufacturer clearly specifies the only points of the chassis where jacks and lifts should be located without inducing damage or permanent deformation of parts.
In order to save fuel and make cars lighter, most of the suspension links are made of conformed sheet metal.
The shapes of those have been designed to stand the normal forces involved in the funcioning of the suspension system, but not much more.
Using those links and pivots to lift a car can bend then, and even slip the jack out of place: not the best idea.

 

[Baluncore]

Rectangular rubber arm pads with a slot to accommodate the lower weld are available that should support a vehicle without causing damage. Such a pad should be more secure than the older style round pads that could rotate while in use.

 

[jake jot]

Rectangular rubber arm pads with a slot to accommodate the lower weld are available that should support a vehicle without causing damage. Such a pad should be more secure than the older style round pads that could rotate while in use.

Most tire shops I visited initially wanted to lift the car by the suspensions. Because they said in some cars, if the suspensions got all the way with the tires hanging in air. It can be damaged and the suspensions need replacements. Is anyone familiar with this phenomenon? What kind of suspensions have these features?

I have a second car and I checked the 7 year old Michelin tires. I saw some brittleness in the rubber as you described in the other thread, I guessed the plasticizers have degraded in the rubber and this can let water in and rust the belts, plies so I plan to have the second car all tires replaced tomorrow as well.

The tires were continuously exposed to the sun since I parked outdoor in open air, so I guess continuous sun exposure can cause tires to be get brittle faster, eh?

 

[Baluncore]

I have a second car and I checked the 7 year old Michelin tires. I saw some brittleness in the rubber as you described in the other thread, I guessed the plasticizers have degraded in the rubber and this can let water in and rust the belts, plies so I plan to have the second car all tires replaced tomorrow as well.

It is cracks in the sidewall that allow water to reach the internal fabric that is the problem. The shallow cracks in the tread rubber may be due to loss of plasticiser and/or steering alignment / cornering.

I cannot afford to replace sets of tires based on predicted service life. It must be based on actual wear or aging since that is use and climate dependent, and it is cold here so tire life can be longer.

 

[jake jot]

It is cracks in the sidewall that allow water to reach the internal fabric that is the problem. The shallow cracks in the tread rubber may be due to loss of plasticiser and/or steering alignment / cornering.

I cannot afford to replace sets of tires based on predicted service life. It must be based on actual wear or aging since that is use and climate dependent, and it is cold here so tire life can be longer.

There are also cracks between the treads. Won't this cause water to reach the internal fabric too? How much thicker is the central portion of a tyre compared to the sidewalls?

 

[Baluncore]

How much thicker is the central portion of a tyre compared to the sidewalls?

Look for something like PR3+8 in small print on the tire. That is 3 ply wall + 8 ply tread.
Or look for mention of steel or polyester. It will depend on national standards.
The load range letter on light-truck tires indicates their ply rating.

 

[jake jot]

Look for something like PR3+8 in small print on the tire. That is 3 ply wall + 8 ply tread.
Or look for mention of steel or polyester. It will depend on national standards.
The load range letter on light-truck tires indicates their ply rating.

This was written in the tire:

Thread plies: 2 polyester
+ 2 steel + 1 Polyamide
Sidewall plies: 2 polyester

So it's 2 ply wall + 5 ply tread

What kind of cracks (and how big) in the tread when the water can rust the steel inside? any photos?

 

[jake jot]

This was written in the tire:

View attachment 295428

Thread plies: 2 polyester
+ 2 steel + 1 Polyamide
Sidewall plies: 2 polyester

So it's 2 ply wall + 5 ply tread

What kind of cracks (and how big) in the tread when the water can rust the steel inside? any photos?

Baluncore, are you saying that all tread separation accidents in the roads occurred due to previous tyre tread area puncture damage and invalid repairs?

And all accidents involving very old tires occurred due to sidewall destruction/degradation and not from tread separations?

Are their car accidents data that prove the above scenerios?

 

[Baluncore]

Baluncore, are you saying that all tread separation accidents in the roads occurred due to previous tyre tread area puncture damage and invalid repairs?

No.

And all accidents involving very old tires occurred due to sidewall destruction/degradation and not from tread separations?

No.

Are their car accidents data that prove the above scenerios?

Not that I know of.

 

[Baluncore]

What kind of cracks (and how big) in the tread when the water can rust the steel inside? any photos?

Where only the surface of the tread is cracked, that is probably due to age and sunlight. The cracking of the tread suggests the rubber has hardened and so will not provide the frictional grip it did when new. They will need to be replaced shortly.

Cracks in the gaps between tread blocks is an indication that the tire needs to be replaced. Older tires that are run with low pressure or high loads will crack around the sidewall. Any crack in a sidewall is dangerous.

 

[Lnewqban]

Most tire shops I visited initially wanted to lift the car by the suspensions. Because they said in some cars, if the suspensions got all the way with the tires hanging in air. It can be damaged and the suspensions need replacements. Is anyone familiar with this phenomenon? What kind of suspensions have these features?
...

What country or region is the location of those tire shops?
I have never heard something like that.

All suspensions have a extension limiter device (mostly inside the shock absorber) which is able to support the weight of the tire and links, as well as the force that the fully extended spring still produces (spring preload).

Please, see:
https://accutuneoffroad.com/articles/spring-preload-matters/

:)

 

[jake jot]

Where only the surface of the tread is cracked, that is probably due to age and sunlight. The cracking of the tread suggests the rubber has hardened and so will not provide the frictional grip it did when new. They will need to be replaced shortly.

Cracks in the gaps between tread blocks is an indication that the tire needs to be replaced. Older tires that are run with low pressure or high loads will crack around the sidewall. Any crack in a sidewall is dangerous.

Look at the cracks besides the threads in the middle portion:

The cracks are besides the threads. What do you call these cracks and what could cause them?

Anyway. I went to the tire shop and decided to change all the 4 tires and I did. This week I just replaced 8 tires with new already (with the other car tyre string plugged improperly).

The tire shop (the country distributor of Dunlop) told me they lift all cars using suspensions, and almost never the pinch welds. So they wanted to lift the car by the suspensions.

I insisted they lift them using the pinch welds (where we use manual car jack).

They then tried but they couldn't because there were many protrusions underneath the car and their lifter could hit the middle portions (red arrow is the pinch weld jack point):

So I let them manually lift each tire and replace them. They said they rarely do this, as they always lift using the suspensions.

While my car tires were being changed. Another car got all 4 tires replaced too. The car was lifted up by using the suspensions as shown above.

I'd like to know. In your place, how do you change all 4 tires? What kind of car lifter do you use?? What kind of lifter is the above or the following (lifter shown in another angle)?

 

[Baluncore]

The cracks are besides the threads. What do you call these cracks and what could cause them?

Age, heat, sunlight, and a little use, but not enough use to wear them out before they perished in the environment. The tread depth gauges are getting close to replacement.

What kind of lifter is the above or the following (lifter shown in another angle)?

The traditional vehicle hoist is designed to lift from under the jacking points. It leaves the area below the vehicle clear for technicians who work on the underside of the vehicle.

Scissor lifts have become more common for changing the height of vehicles. That makes it more convenient for the technician to work on the wheels and brakes.

The scissor lift with a wheel lifter, designed to lift from under the suspension is not suitable for lifting from under the jacking points. It is clearly optimised for wheel and brake work, where the area outside the vehicle is kept clear.

I'd like to know. In your place, how do you change all 4 tires? What kind of car lifter do you use??

I never change all 4 tires in one lift, I change them one at the time. I do some work on light vehicles, so I do have an old 2.5 tonne post hoist that reaches in under the jacking points. Most work uses floor jacks under heavier farm tractors or trucks, which stand under a gantry crane.

 

[jake jot]

Age, heat, sunlight, and a little use, but not enough use to wear them out before they perished in the environment. The tread depth gauges are getting close to replacement.The traditional vehicle hoist is designed to lift from under the jacking points. It leaves the area below the vehicle clear for technicians who work on the underside of the vehicle.

Scissor lifts have become more common for changing the height of vehicles. That makes it more convenient for the technician to work on the wheels and brakes.

The scissor lift with a wheel lifter, designed to lift from under the suspension is not suitable for lifting from under the jacking points. It is clearly optimised for wheel and brake work, where the area outside the vehicle is kept clear.I never change all 4 tires in one lift, I change them one at the time. I do some work on light vehicles, so I do have an old 2.5 tonne post hoist that reaches in under the jacking points. Most work uses floor jacks under heavier farm tractors or trucks, which stand under a gantry crane.

I think I can summarize my question now after reading all about control arms.

The question is whether one can lift the cars via the control arms indicated in red points in the picture.

The tire shops did this to all vehicles, lifting the entire vehicle using 4 points or control arm of each tire. Can someone compute using strength of materials whether the control arm can take the load? My inquiry concerns the Macpherson strut and not the double wishbone which I think can take the load.

 

[Baluncore]

Can someone compute using strength of materials whether the control arm can take the load?

It can take the load. Those calculations were done by the engineers during the design process.

My inquiry concerns the Macpherson strut and not the double wishbone which I think can take the load.

That picture is misleading. The scale is different between the two included diagrams, and the MacPherson strut is deliberately made to look poorly engineered. Do you have a link to the source of that diagram ?

 

[jake jot]

It can take the load. Those calculations were done by the engineers during the design process.That picture is misleading. The scale is different between the two included diagrams, and the MacPherson strut is deliberately made to look poorly engineered. Do you have a link to the source of that diagram ?

My car is exactly similar to this model in the video:

This is the control arm of the Macpherson Strut:

It is as sturdy as the Double Wishbone. But note this mechanics. The weight of the car is supported by the suspension which is supported in the wheel core. The weight of the car is NOT supported by the control arm! So how can the control arm be designed to lift the entire car? Unless you are saying the weight of the car is supported by the control arm, how? This is true for Double Wishbone, but not Macpherson Strut suspension.

from:

 

[Baluncore]

This is the control arm of the Macpherson Strut:

You show the control arm and radius rod as an integrated Y shaped component. At the outboard end there is a ball joint with a taper, and a nut below. That ball joint positions the steering knuckle or hub carrier above.
When supported by the suspension, it is that lower nut surround that must be contacted by the jack. The weight of the vehicle is transferred through the ball to the knuckle, then up through the shock absorber tube and coil spring to the body.

 

[Lnewqban]

 

[jake jot]

You show the control arm and radius rod as an integrated Y shaped component. At the outboard end there is a ball joint with a taper, and a nut below. That ball joint positions the steering knuckle or hub carrier above.
When supported by the suspension, it is that lower nut surround that must be contacted by the jack. The weight of the vehicle is transferred through the ball to the knuckle, then up through the shock absorber tube and coil spring to the body.

So you saying the blue line is continuous from the suspension up to the top of the control arm so it can be lifted below it. Can the tire shop lifting point use A (in red text above)? Because I saw them using their car lift on the bolts themselves such that I saw the car hanging on the 4 bolts. Or must it be in point B (in red text above) only one inch from the bolt?

This is important to note because the tire shop has free service to patch the tire if there is puncture and they love to use the machine to lift the whole car.

By the way, I notice the drive shaft boot is leaking. Based on the picture, how much time it got left? I will bring it to the factory after the Omicron surge is over.

When I told them to manually lift each tire and used my factory spring jack. I noticed the jack seems to be bending at an angle. Is this normal or a bad jack?

Lastly. A friend told me not to use alligator jack perpendicular to the pinch weld because it can bend the pinch weld from the runner below in the unibody design. Is it true? how do you properly position the alligator jack on the pinch weld then?

That's all I need to know for now. Thanks a lot for all the tips.

 

[Lnewqban]

Please, see:
https://www.autozone.com/diy/safety/how-to-jack-up-a-car

 

[Baluncore]

So you saying the blue line is continuous from the suspension up to the top of the control arm so it can be lifted below it. Can the tire shop lifting point use A (in red text above)? Because I saw them using their car lift on the bolts themselves such that I saw the car hanging on the 4 bolts. Or must it be in point B (in red text above) only one inch from the bolt?

The nut-on-bolt should be used since any point closer along the lever arm to the body hinge line will result in the car rising, which will cause the arm angle to become steeper, so increase the chance of the car sliding of the lifting point. Place the jack so the cup on the jack encloses the bolt, so it cannot slide off, and the suspension angle remains the same during the lift.

By the way, I notice the drive shaft boot is leaking. Based on the picture, how much time it got left? I will bring it to the factory after the Omicron surge is over.

The boot covers the CVJ and is filled with special lubricant. Any leak requires cleaning of the CVJ, and replacement of the boot and lube, since if water or dirt enter, the CVJ will wear quickly. Get the boot replaced before driving in wet or dusty conditions.

I noticed the jack seems to be bending at an angle. Is this normal or a bad jack?

It looks like a cheap jack.

Lastly. A friend told me not to use alligator jack perpendicular to the pinch weld because it can bend the pinch weld from the runner below in the unibody design. Is it true? how do you properly position the alligator jack on the pinch weld then?

What you call an “alligator jack” is AKA a “trolley jack”. As you raise the vehicle the trolley jack should roll in, remaining under the lifting point. There should be a slotted rubber block, fitted between the pinch weld and the cup head of the jack.

That's all I need to know for now. Thanks a lot for all the tips.

You appear to live in a black and white version of the world, that to others is actually many shades of grey. In the real world where everything is pragmatic and nothing is certain, do the job safely. The customer is always right, so at worst when you tell the technicians how to do the job, you will pay for and should get what you ask for.

 

[pbuk]

The customer is always right, so at worst when you tell the technicians how to do the job, you will pay for and should get what you ask for.

Not when you are telling them to operate unsafely. If the shop has established that the safe method of work for tyre replacement is to support a lift at appropriate points on all 4 suspensions then they must not do anything else, and certainly not using customer supplied jacking equipment.

Marked jacking points under the pinch weld are provided by manufacturers so that even a fool that thinks they know everything the average driver can safely replace a wheel at the roadside using the cheap provided equipment; in particular this does not require the driver to locate and ensure the jack is securely positioned at a strong point of the suspension which will not change orientation as the vehicle is lifted. That does not mean that pinch weld jacking points are appropriate for use where professional lifting equipment is available for use by a trained operator.