padgett Posted March 8, 2011 Share Posted March 8, 2011 Am adding a door to my patio enclosure so I can park a car in there and have a question. The flooring is 18" square ceramic tile on a concrete slab and I am concerned about cracking by driving a 3,600 lb car with 215x65 tires on the front.Am thinking about either 1x12 planks as runners or some HF foam mats.Any opinions ? Different idea ? YWTK.<!-- google_ad_section_end --> Link to comment Share on other sites More sharing options...
Shop Rat Posted March 8, 2011 Share Posted March 8, 2011 Not sure if you have a Harbor Freight near you, but they have the foam squares that interlock like puzzle pieces. If you decide to go that way you could put them down to get the car in and out and take most of them up when it is just sitting. Link to comment Share on other sites More sharing options...
CarlLaFong Posted March 8, 2011 Share Posted March 8, 2011 Four jack stands will keep it off the tile.Put a car on jack stands, on tile, and I guarantee they'll crack....instantly Link to comment Share on other sites More sharing options...
keiser31 Posted March 8, 2011 Share Posted March 8, 2011 (edited) Put a car on jack stands, on tile, and I guarantee they'll crack....instantlyI agree. I also think that as soon as you put a floor jack under the car to lift it, you will crack the tile. As I work in architecture, I might suggest that you paint some decorative pattern on the concrete floor. You could work out a pattern in the floor to be the width of the track of the car and go each way with it so it looks like it was planned. Just about any tile you put on the existing concrete will crack. Edited March 8, 2011 by keiser31 (see edit history) Link to comment Share on other sites More sharing options...
Guest Dr. Strangelove Posted March 8, 2011 Share Posted March 8, 2011 The real question should be, do I have any spare tiles to replace the broken ones?If you want to test the integrity of each 18" tile and the quality of the installation, then drive your 3,600 lb. car on it.I once lived in a home that had a homeowners association. I brought one of my cars in the backyard to wax it in the shade. The starter, on its last legs gave out, so the car remained in the backyard until 9PM or so, until I was able to get a starter then install it. Two days later a letter arrives citing this that and another covenant that I had broken by having that car in the back yard. I hope you don't break your tiles or the rules in your neighborhood... Link to comment Share on other sites More sharing options...
padgett Posted March 8, 2011 Author Share Posted March 8, 2011 Have 32 feet of HF foam pads, just wondering if they will distribute the weight enough. Suspect 1x12 boards as runners would.Have different work areas so no jacking here, just the enclosed patio did not work for a family room (too noisy when rains), now just used for storage, and need one more inside parking place.Do have a few spares but would rather not break in the first place. Link to comment Share on other sites More sharing options...
R Walling Posted March 8, 2011 Share Posted March 8, 2011 Do the math, 3600lbs divided by 4 (tires) divided by 20 (sq in. per tire equals 45lbs per sg inch. A womans spke heel of a 95lb woman exerts aprox. 380lbs per sq in. The limiting weight on a tile on a wooden floor is the amount of flex or bending of the wood. You would not have this with concrete.If the tiles are properly set without voids, I would not think that it would be a problem. The only problem would be if the concrete under it has cracked, then you would then probaly crack one. Link to comment Share on other sites More sharing options...
Barry Wolk Posted March 8, 2011 Share Posted March 8, 2011 My garage has been tiled for 15 years. I've jacked cars up repeatedly without a single failure. Properly set, they should last you for a lifetime. Link to comment Share on other sites More sharing options...
padgett Posted March 8, 2011 Author Share Posted March 8, 2011 Thank you. Have the Harbor Freight pads but am leaning toward 1x12 boards as runners, that would really spread the weight.Didn't mention the uneven weight distribution - 65/35 but also suspect a 215 has a broader contact patch than 20 sq in.Of course the hard part is moving the 20x10x4ft pile of "stuff" that is in the room now...Barry: that looks nice but were those tiles designed for a driveway ? Link to comment Share on other sites More sharing options...
R Walling Posted March 8, 2011 Share Posted March 8, 2011 I think that the boards will be a detrement as they will concentrate the weight to smaller areas of contact than the tires. Link to comment Share on other sites More sharing options...
Barry Wolk Posted March 8, 2011 Share Posted March 8, 2011 I believe the boards would spread out the distribution, but also think they are wholly unnecessary. Link to comment Share on other sites More sharing options...
Guest maudsley Posted March 8, 2011 Share Posted March 8, 2011 The tile itself can handle the weight. The thinset the tike is set in is the area of concern. However if the thinset was less than good, you would probably have some cracked tiles from just walking on them. If you dont have any cracking, I think with it can handle it. Link to comment Share on other sites More sharing options...
Rusty_OToole Posted March 8, 2011 Share Posted March 8, 2011 The boards will distribute the weight better than foam pads. 2X10 better support than 1X12.If it was my house and I was concerned about cracking tiles I would buy some 2X10s to drive up on. Link to comment Share on other sites More sharing options...
trimacar Posted March 8, 2011 Share Posted March 8, 2011 Hi- you don't have to do any math to figure out what pressure your tires would exert on the floor. Whatever the air pressure is in the tire, that's the pressure per square inch on the floor. Link to comment Share on other sites More sharing options...
Barry Wolk Posted March 8, 2011 Share Posted March 8, 2011 Regardless of weight????? Link to comment Share on other sites More sharing options...
Guest Dr. Strangelove Posted March 8, 2011 Share Posted March 8, 2011 Hi- you don't have to do any math to figure out what pressure your tires would exert on the floor. Whatever the air pressure is in the tire, that's the pressure per square inch on the floor.Boeing 747-400, weight: 900,000 lbs., main wheel tire pressure: 200 lbs.If the runway only had to endure 200 lbs per square inch, why are the re-enforced concrete runways poured at 30" to 36" depths then? Link to comment Share on other sites More sharing options...
padgett Posted March 8, 2011 Author Share Posted March 8, 2011 Interesting thought. I used to divide the total weight on the front end of my V-8 Sunbird (in a hard corner all of the weight is on the outside tire, used to carry the inside tire over speed bumps) by the load rating & multiple by max psi. . Came up with something absurd for 1978 - 50 psi. Tried it and found could turn in much harder than before. Link to comment Share on other sites More sharing options...
CarlLaFong Posted March 8, 2011 Share Posted March 8, 2011 Hi- you don't have to do any math to figure out what pressure your tires would exert on the floor. Whatever the air pressure is in the tire, that's the pressure per square inch on the floor.Oh Boy! I'm gonna need a big tub of popcorn for this one. :eek:Weird science indeed. If that is true, deflate the tires to 5 PSI and you"ll have no problem:rolleyes: Link to comment Share on other sites More sharing options...
trimacar Posted March 8, 2011 Share Posted March 8, 2011 It's simple physics. The pressure inside the tire has to match the pressure resting on the surface of the ground, in order to support the weight.The runway, in the case of an airplane, has to be much stronger to handle the shock load of an airplane landing. At the point of touchdown, if it's not a "greaser" landing, there's an abrupt load to the surface of the concrete. The reason that the concrete has to be thick is that concrete can stand a tremendous compressive load, but virtually no tensile load. Thus, pressing down is fine, but if the concrete isn't thick, then it will break due to the horizontal (tensile) load not being supported. I may not be explaining this quite as well as some might.Regardless of the weight of the car, the pressure of the tires on the garage floor will equal the weight of the car, thus the psi inside the tire equals the psi on the outside of the tire (the contact surface). If you add more weight to the car, the tire will deform (flatten) more, or the pressure will rise slightly, or both, but the equilibrium is maintained.Not trying to sound like a know it all, it's just a fact. Link to comment Share on other sites More sharing options...
Barry Wolk Posted March 8, 2011 Share Posted March 8, 2011 So, if you jack your car up, put your hand between the tire and the ground and lower the car onto it, you'll only be supporting 35 pounds of weight?I'd sure like to see a video of you doing that! Link to comment Share on other sites More sharing options...
trimacar Posted March 8, 2011 Share Posted March 8, 2011 No, you'd be supporting 35 pounds of weight per square inch. It would, of course, crush your hand, if your hand was 4 by 5 inches, that's 20 square inches, or 700 pounds.Now, I will say that all my talk of pressure deals with my early cars. If you start adding support structure to the tire (i.e. steel belted radials), the the support added would influence the pressure vs. contact area equation. Link to comment Share on other sites More sharing options...
Barry Wolk Posted March 8, 2011 Share Posted March 8, 2011 Link to comment Share on other sites More sharing options...
trimacar Posted March 8, 2011 Share Posted March 8, 2011 For those of you who wish to read the math behind this equal pressure discussion, here's a link to an older explanation. Note that it states a tire that has a flexible sidewall. Thus, I stand by this on older tires, it would be slightly different on steel belted radials. What holds true regardless of weight or tire type, is that the pressure per square inch of a tire on a garage floor, at rest, equals the weight of the car divided by the square inch contact area of the sum of the four tires.The encyclopædia britannica: a ... - Google Books Link to comment Share on other sites More sharing options...
keiser31 Posted March 8, 2011 Share Posted March 8, 2011 Looks as though I misread the original post. I failed to see that you already have tile down. Sorry about that. Link to comment Share on other sites More sharing options...
CarlLaFong Posted March 9, 2011 Share Posted March 9, 2011 Originally Posted by trimacar Hi- you don't have to do any math to figure out what pressure your tires would exert on the floor. Whatever the air pressure is in the tire, that's the pressure per square inch on the floor.I barely made it out of high school, but this is the goofiest thing that I have heard in a long time. Tell me if I have this correct. If you have, as I said earlier, 5 PSI in your tires, you will exert 5 pounds per square inch on the tile. If you air them up (let's get silly here)to 500 psi, the very same car will exert 500 PSI on the tile. I don't get it. A racing bicycle runs high pressure tires, not sure of the PSI, but let's say its 80. I think you know where this is going. The bikes weigh less than 20 pounds. What if the car has no tire and you're storing in on its rims? What's the pressure on the tile now? Using your scientific principles, it has to be zero Link to comment Share on other sites More sharing options...
Guest Skyking Posted March 9, 2011 Share Posted March 9, 2011 I can't believe there's 25 hits to this thread. Have any of you ever been to a Mall that had a car show?? Tile floors and no cracks. Link to comment Share on other sites More sharing options...
Barry Wolk Posted March 9, 2011 Share Posted March 9, 2011 What holds true regardless of weight or tire type, is that the pressure per square inch of a tire on a garage floor, at rest, equals the weight of the car divided by the square inch contact area of the sum of the four tires.That's not what you stated earlier. Link to comment Share on other sites More sharing options...
CarlLaFong Posted March 9, 2011 Share Posted March 9, 2011 (edited) That's not what you stated earlier.It's simple physics:confused:This would only be true if the car had a perfect 50/50 weight distribution. On most cars, there would be more PSI on the front tires than the rear Edited March 9, 2011 by 58Mustang (see edit history) Link to comment Share on other sites More sharing options...
38Buick 80C Posted March 9, 2011 Share Posted March 9, 2011 Put the car on the tile no boards it will be OK, Most new car dealerships have tiled showrooms thin set with no problems. Yes there could be air pockets under the tile which could cause a crack. If it is that big of a concern take a bolt from the garage and tap the tile. Improperly installed tile will have a hollow sound when tapped. Keep the car off the hollow sounding areas. Link to comment Share on other sites More sharing options...
kevin1221 Posted March 9, 2011 Share Posted March 9, 2011 "Most new car dealerships have tiled showrooms thin set with no problems."I run a new car dealership. The tile in our showroom is 22 years old. We have had no problems with cracking from cars being driven or parked on the tile. Link to comment Share on other sites More sharing options...
trimacar Posted March 9, 2011 Share Posted March 9, 2011 OK, this is my last post on this topic.On the original question, no problem on tile that has been installed correctly on a concrete pad base.On pressure, either you get it our you don't, and I'm not going to argue engineering facts. I reply below in capital letters, not yelling, just answering. When you reduce pressure in tires, they flatten, more square inches at less pressure per square inch. Inflate to high pressures, small footprint, high pressure per square inch.From a reply: If you have, as I said earlier, 5 PSI in your tires, you will exert 5 pounds per square inch on the tile. YES THAT IS CORRECT.If you air them up (let's get silly here)to 500 psi, the very same car will exert 500 PSI on the tile. YES THAT'S CORRECT.I don't get it. A racing bicycle runs high pressure tires, not sure of the PSI, but let's say its 80. I think you know where this is going. The bikes weigh less than 20 pounds. IN THAT CASE, THERE WOULD BE VERY FEW SQUARE INCHES CONTACT SURFACE ON THE GROUND, WHICH IS EXACTLY WHAT HAPPENS.What if the car has no tire and you're storing in on its rims? THAT'S A TOTALLY DIFFERENT SITUATION WITH CONTACT WEIGHT.What's the pressure on the tile now? Using your scientific principles, it has to be zero .Now, on to bigger and better things. Link to comment Share on other sites More sharing options...
padgett Posted March 9, 2011 Author Share Posted March 9, 2011 (edited) Just one loint of natural paw. Inflation psi has nothing to do with the contact patch loading. The tire could be flat and the loading would be the same (just the patch would be larger). In general a tire will begin to lift the car somewhere between 5 and 10 psi and that is where the inflation pressure x contact area matches the load.BTW know malls and dealers put cars and trucks on tile all the time. What I do not know (still) is the difference between commercial (e.g. pavers) and residential tile. Also the original patio underneath was never designed for tile.Think I will go with the HF pads sice I already have them. Edited March 9, 2011 by padgett (see edit history) Link to comment Share on other sites More sharing options...
CarlLaFong Posted March 9, 2011 Share Posted March 9, 2011 (edited) OK, this is my last post on this topic.On the original question, no problem on tile that has been installed correctly on a concrete pad base.On pressure, either you get it our you don't, and I'm not going to argue engineering facts. I reply below in capital letters, not yelling, just answering. When you reduce pressure in tires, they flatten, more square inches at less pressure per square inch. Inflate to high pressures, small footprint, high pressure per square inch.From a reply: If you have, as I said earlier, 5 PSI in your tires, you will exert 5 pounds per square inch on the tile. YES THAT IS CORRECT.If you air them up (let's get silly here)to 500 psi, the very same car will exert 500 PSI on the tile. YES THAT'S CORRECT.I don't get it. A racing bicycle runs high pressure tires, not sure of the PSI, but let's say its 80. I think you know where this is going. The bikes weigh less than 20 pounds. IN THAT CASE, THERE WOULD BE VERY FEW SQUARE INCHES CONTACT SURFACE ON THE GROUND, WHICH IS EXACTLY WHAT HAPPENS.What if the car has no tire and you're storing in on its rims? THAT'S A TOTALLY DIFFERENT SITUATION WITH CONTACT WEIGHT.What's the pressure on the tile now? Using your scientific principles, it has to be zero .Now, on to bigger and better things.You, sir, as as wrong as any person could ever hope to be. I'm glad this is your last post regarding this matter. I also hope you are not involved in education of any sort. To think, and to believe, that you can, essentially, vary the weight of an automobile through the simple expediency of letting some air out of the tires borders on the ridiculous. You're stuck on this contact patch theory. It is nonsense. Again, lower the pressure to 5 PSI. Let us assume that the contact patch for each, semi flattened, tire is now is 6 inches wide by 10 inches long. According to my Captain Midnight Decoder Ring that is 60 square inches per tire Plugging these figures in I come up with 1200 pounds per square inch divided between 4 tires. I don't know what a 59 Caddy, weighs, but lets say it's 4,000 pounds (hey, it's got a couple of fat guys in it). Here's my question...............Wait for it........WHAT HAPPENED TO THE OTHER 2800 POUNDS?????? Edited March 9, 2011 by 58Mustang (see edit history) Link to comment Share on other sites More sharing options...
sambarn Posted March 9, 2011 Share Posted March 9, 2011 So my first thought is to the structure beneath the tile. As a patio was that slab poured as a porch, with a relatively shallow footprint? If you build your house upon the sand..... I would worry that the structure beneath the tile could shift and cause bigger problems than cracking tile, If its anything less than very solid. Link to comment Share on other sites More sharing options...
trimacar Posted March 9, 2011 Share Posted March 9, 2011 I've got to post one more time.John and group, I never, ever, stated that the weight of the car changes. As tire pressure changes, so does the contact area of the tire on the floor, and for a flexible sidewall tire, the pressure in the tire PER SQUARE INCH is equal to the pressure on the floor PER SQUARE INCH. At some point, if pressure decreases inside the tire, the tire can't support the car, the rim touches the inside of the tire and then the rim supports the weight.Here is Boeing's explanation, as it relates to aircraft tires, please read this, it's not my theory, it's a simple statement of physical law.http://www.boeing.com/commercial/airports/faqs/calctirecontactarea.pdf Link to comment Share on other sites More sharing options...
Barry Wolk Posted March 9, 2011 Share Posted March 9, 2011 This was the original statement.Hi- you don't have to do any math to figure out what pressure your tires would exert on the floor. Whatever the air pressure is in the tire, that's the pressure per square inch on the floor. Link to comment Share on other sites More sharing options...
CarlLaFong Posted March 9, 2011 Share Posted March 9, 2011 This was the original statement.And that is the statement that I am addressing. It is, simply, wrong. Period. I did not read Boeings theory. I'm sure it is correct and, also, above my pay grade. I also understand how increasing contact area will spread the weight over a larger area. What I am saying is the original post regarding there being no need for math and the pressure in your tires equaling the pressure on the floor, regardless of the weight of the vehicle is deeply flawed to the point of being absurd. Again, please explain the Cadillac analogy that I posted, based on the original statement, not Boeings, Einsteins or Hawkings formulae. Link to comment Share on other sites More sharing options...
trimacar Posted March 9, 2011 Share Posted March 9, 2011 John, again, it's the pressure per square inch, not the total weight of the car.And yes, as DriveAG points out, there are other factors, but he also states the difference between weight and pressure, two totally different things.But, those factors aside, if there is 35 psi in your tire, then there's 35 psi pressing against the floor of the garage. Weight of the car is not even considered in that. Link to comment Share on other sites More sharing options...
38Buick 80C Posted March 9, 2011 Share Posted March 9, 2011 (edited) John, As a Mechanical Engineer, I'm gonna have to go with trimacar on this one. Hopefully I can simplify it so it makes more sense and I'll try to use your Cadillac example above for my own example.Car Weight = 4000 pounds (lbs)Assume equal weight distribution to all 4 tires = 1000 lbs at each tire.At 40 PSI the tire contact patch (part of the tire physically in contact with the ground) = 25 sq in or a 5" x 5" area. So we have 1000lbs pushing on a 5" x 5" area (or 25 sq inches), so PSI is lbs per square inch, so 1000 lbs pushing again 25 squares inch of area equals 40 lbs per one inch of area just dividing the overall weight by the number of square inches, same as the tire pressure. So for any one inch of sq area under in the contact patch area there is 40 lbs of force against it, but we have 25 sq inches so we have 1000 lbs pushing on 25 sq inches of area.Now lets assume the RF tire only loses air to 30 PSI. In reality we know the car leans to the RF and that tire flattens out so MORE of the tire is in contact with the ground. There is still 1000 lbs at the RF but now the contact patch larger (it will actually be 33.33 sq inches or a little more than 5.75" x 5.75"). So now we have 1000 lbs pushing again 33.33 sq in so 1000 lbs per 33.33 sq inches = 30 lbs per one sq in or same as tire pressure.Now going to the final extreme. Tire is completely flat no PSI. Therefore it might as well not be there so lets assume it is not, it will just be the rim so two very very small contact patches where the rim is touching the ground will support the weight of the car. Still 1000 lbs at the RF but now there are two contact points so 500 lbs per point and the points are pretty small but for easy math lets assume one contact point covers exactly one sq in. of area that means 500 lbs is pushing on one sq in = 500 lbs per sq in. So as tire pressure increases less tire will be touching the ground so that 1000 pounds is distributed over less area and as tire pressure approaches zero more tire will be on the ground distributing that 1000 pounds over more area until the rim touches the ground at tire pressure equals zero and the weight of the car now goes through the rim not the tire.So back to the original question will the tile hold up. Well if the average human weight 200 lbs and wear normal shoes that about 10 sq in of contact area with the ground (5 per foot) so the average human puts 20 lbs per sq in of pressure on tile and double that is not out of the question for with an overweight individual or smaller high heal type shoes. So an average car with 30 PSI in the tires should be fine., but if you are concerned lower the air pressure so that the weight (lbs) at each wheel is distributed over a large surface area thus lowering the pressure (lbs per sq in) on any given point on the tile. Edited March 9, 2011 by 38Buick 80C Addtional comment (see edit history) Link to comment Share on other sites More sharing options...
CarlLaFong Posted March 10, 2011 Share Posted March 10, 2011 This is amazingly close to another argument that I had on another site. The premise was that you can increase the amount of fuel flowing from the tank to the carburetor by increasing the size of the fuel line. This was on a gravity flow system. I said, how can it increase flow if you don't, also, increase the size of the outlet at the bottom of the tank and the inlet at the carb. Sure enough, here comes an engineer with his slide rule, little Xs, Ys, Pi, sines, cosines, algohrithms, and what have you and "proves" me wrong. I asked him, point blank, if I remove the fuel line and allow the gas to run on the ground and then I connect a fire hose to the same outlet, that MORE gas will actually flow. His answer was, get this, "Yes."Now I'm being told that, irrespective of a vehicles weight, it will never load a floor more than the PSI in the tires times the contact patch, or that there is a chart that calculates the patch area for each tire and how much it changes at varying pressures. Here is another quote from Trimacar John, again, it's the pressure per square inch, not the total weight of the car.And yes, as DriveAG points out, there are other factors, but he also states the difference between weight and pressure, two totally different things.But, those factors aside, if there is 35 psi in your tire, then there's 35 psi pressing against the floor of the garage. Weight of the car is not even considered in that.How, in the name of all things holy can the weight of the car NOT be a factor??????????If that is true, then a tire and wheel assembly, inflated to 35 PSI will exert 35 PSI load to the floor sitting there by itself, supporting only the weight of the wheel.To another poster, I do know the difference between the PSI in the tire (pounds per square inch of pressure above normal atmospheric pressure) and the PSI on the floor (weight divided by contact area).I'm not a troll, nor am I trying to incite a riot. I'm a common guy, with (I hope) common sense, and the original statement and, especially, the one that I quoted above just doesn't fly in my little world Link to comment Share on other sites More sharing options...
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