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Porous Rims

Old 09-13-2018, 10:41 AM
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Porous Rims

I noticed that 3 of my tires on my '07 Jeep Compass are always getting low. There are no leaks with the tires nor with the beads.

I heard someone tell me I might need new rims because they are deteriorated from corrosion because they are cast aluminum.

When I looked at the inside of the rims, I don't see anything obvious, but was told to immerse the water in a tank and watch for air bubbles.

Before I go trying to find a way to dunk my tires/rims in water, has anyone ever heard of this?
Old 09-13-2018, 12:22 PM
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It's possible that the rims were not cast properly and the castings are porous. If the rims did not have porosity originally, I don't think it can happen later. But, I'm not an expert on this subject.

You did check the valve stem cores?

You don't need to dunk them completely. Just spray some soapy water on the whole tire/wheel combo and inspect carefully.
Old 09-13-2018, 02:01 PM
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I should've added, I had all the valve stems (both core and body) replaced 2 months ago. I noticed when I went to go check the air pressure it was low, and then after a month it was low again. Asked 4 shops in my area, and one of them told me it could be porous rims from the chemical reaction from salt that is on the road.

Whatever it is, I found if I did the math, it is about .22 psi per day. Which after a month is a lot. So whatever the leak is, the leak is small.

So when the one tech said porous rims, I was fascinated. There doesn't seem to be too much info out there on the webs about it either.

I mean its not a huge deal, but it is annoying to have to keep adding a ton of air after a month/month and a half or so. I always check the tire pressures anyways.
Old 09-13-2018, 06:29 PM
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If it were me, I'd go with Roadie's original suggestion of a spray bottle with some liquid soap. It wouldn't be the first time a tire shop installed something incorrectly or maybe a faulty part. If it's leaking, it's coming from somewhere, bubbles will tell the tale.

****** I once knew a stripper named Bubbles.... boy she had a heck of a tail.. but I digress...********
Old 09-13-2018, 08:38 PM
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I had an old Michelin tire on my truck that started leaking through the sidewall. I'm sure it was my fault because I had let the air out down to 20 psig one time and even 15 psig another time while on the beach and drove home 15 miles at that pressure. Anyway, I had to inspect very carefully to see it. It prompted me to buy new tires 6 months before the annual inspection when I was planning to buy them. So, I replaced the 265/70x17 tires with 285/70x17 Firestone all terrain tires that don't need deflating to drive on the beach in any of the softest spots.
Old 09-13-2018, 11:52 PM
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Have your tires checked. Or check them yourself. Until then, there is no use guessing.

You went to 4 shops in your area, and not one of them took your wheels off to check for the leak?

I like dunking the tire in a tank of water, as opposed to the spray bottle with soapy water. But that is just preference. Some people like blondes, I like the Muslims with their hair covered.

Your Jeep Compass is an '07. If manufactured in '06, it is 12 years old. Have it checked out. You may end up replacing wheels and/or tires.

https://www.utires.com/articles/tire...r-slowly-fix//General information /Tire care and maintenance​​ /Tire Safety /Why Your Tire Loses Air Slowly and How to Fix It
  • 03.07.2017
Any tire loses air slowly at the rate of 1-3 psi a month due to osmosis. However, a stronger leak may be the result of the following issues:
  • Wheel elements damage
  • Tire damage
  • Temperature change.

If a has tire deflated more than 25% from the recommended pressure, the likelihood of a tire-related crash increases threefold. Therefore, it’s crucial to know about every leak your tires may have and fix them in time.

Possible Reasons Why a Tire Loses Air Slowly

Wheel Issues

The two main wheel problems due to which a tire loses air slowly are:
  • Poor valve stem.Tire velve stem. Image source: www.peachparts.comValve stems deteriorate and leak air due to the exposure to lots of chemicals on the road. Usually, drivers get a new set along with the new tires. However, if a tire loses air slowly yet over 1-3 psi a month, they may need replacement earlier. Over-tightening valve cores may also be one of the reasons of the leak. The torque should be about 4 inches per pound, so you may need a pre-set wrench.
  • Bent or damaged wheel.
    The wheel may partially lose its perfectly round shape due to corrosion or hitting a road hazard. Also, if corrosion is present at the surface where the tire is mounted, the air loss may be greater. A bent wheel will also contribute to the vibration of the vehicle, which may damage the tire’s bead, contributing to the air leak.
Corroded wheel bead seat.If you see any of these issues, make sure to visit a technician and get a consultation on changing the valve stem or repairing the wheel.

Tire Damage

There are several common tire-related reasons why a tire loses air slowly:
  • Nails.
    They can puncture the tire and cause air to leak at the rate of 2-3 psi a day. A nail may remain in the tire and cause seemingly insignificant air loss. But it still needs to be extracted. If it isn’t the leak could get worse and your tire may need an urgent repair to make sure you don’t get a flat tire.

    Nail in a tire
  • Bead damage.
    Any sealing surface between rubber and metal can cause loss of air. Bead chunking, a small piece of debris between the rim and the tire etc., can open a small window for the air.Damaged tire beadAge also contributes to the seal breaking, as the rubber weakens over the years, losing its elasticity. That’s why it’s so important to know the age of the tire before you buy it.
    Finally, the bead may sit improperly on the rim due to inexperienced technician work, and as a result, the tire loses air slowly.
  • Another damage due to road hazards.
    Driving over a large pothole or a curb may flex the tire sidewalls and make the tire lose air. If there is no damage to the tire-wheel unit, you may just need to re-inflate the tire. However, check for any sidewall bulges, cuts, and punctures. These may indicate an internal or external damage that could contribute to the leak.
When you notice your tire loses air slowly or it’s time for a routine check at a mechanic, make sure to look for all this damage. Some of them, like a small puncture, may be reparable, and the sooner you do it, the better.

Temperature Change

A tire loses about 2% of the air with every 10F drop in temperature. Accordingly, it rises 2% with every 10F rise. So, light passenger cars may lose/gain about 1 psi, while pickups and buses may lose/gain 2 psi. In most part of the US, the difference between day and night temperatures is about 20F. So, if your vehicle spent a night outside in the cold and you find the tires are underinflated in the morning, don’t rush to add pressure. While you drive, the inflation will return to the norm by the afternoon.

Pressure changes according to the temperature because air expands when heated and shrinks when cooled. The amount of air is still the same, so if there is no other damage, keep the pressure as it is.

Locating the Air Leak

If your tire loses air slowly, there are several ways to find the leak:
  • By sound or feel.
    In the easiest cases, you may manage to find the leak by sound or feel. There will be a distinctive hissing sound, intensifying as you get closer to the leak. Touch the tire in that place and feel whether there’s air loss. If the tire is hot, the place with the leak or damage will feel hotter.
  • By using soapy water.
    You can add any soap or 20% detergent into a spray with water and spray the tire and rim edge. Cover the valve stem with the mixture first, then the inside and outside edges of the rim. You can also pour some on the tire sidewalls and tread to see if there’s any damage you might have missed. Bubbles will appear where the leak is present. However, remember that you may need to wait about 5 minutes before you notice the place where your tire loses air slowly.
  • By putting the wheel into water.
    Remove the wheel from the vehicle and put it into water. The leaky part will start to release small bubbles and show itself. The puncture or other damage may be on the other side, so if you don’t see it in 5 minutes, turn the tire over.
Usually, the soapy water method works perfectly even for small punctures. It’s also the easiest and least time consuming, as you don’t have to demount the tire.

Fixing the Issue

If your tire loses air slowly, here are the things you can do:
  • Repair the tire
  • Repair the valve stem
  • Repair and/or restore the rim.
NOTE: Not all damage to the wheel and tire are reparable. Some repairs are temporary, giving you some time to get to the nearest tire shop. But you should never drive with temporary or poor-quality repairs on a daily basis.

Repairing a Tire

You can repair a puncture at a technician workshop or at home. If you want to do it yourself, use tire sealants or a special plug kit.

Using a Sealant

You will need a sealant, an air pump, and a pressure gauge.

Insert the nose of the sealant into the puncture where the tire loses air slowly from, or the valve. Make sure you adjust it so that the sealant is pouring right on the inside surface of the tire. Pour it carefully until you use a whole standard bottle.

It will work as a protective layer inside the tire, so when you pump it up, the pressure will push the mixture into the hole. Thus, it will form a rubber-like plug, repairing your tire.How tire sealant works. Image source: www.grahamwalkercars.ieThere are pre- and post-puncture sealants, so buy the latter if your tire loses air slowly.

NOTE: Make sure you look for propylene glycol sealants. There are also those based on ethylene, which is toxic for humans and may be dangerous for tires after some time.

Using a Plug Kit

A standard tire plug kit.A plug kit consists of a set of plugs, rubber cement, reaming tool, and a plug tool. Also have pliers or another tool ready to take the nail out of the tire. You may need a car jack and a lug wrench if it’s more comfortable for you to repair the tire on a removed wheel. However, you can do it with the wheel on the vehicle.

Firstly, remove the nail from the tire and use a reaming tool to clean the hole and make it fit the plug. Be careful not to make the hole too large, or you can do more damage so your tire loses air slowly or go flat instantly. Then, insert the plug into the plug tool and cover the tip of the tool with a bit of rubber cement. After that, insert the plug into the hole in the tire and pull the tool out of it. Cut the plug that remains on the surface as close to the tread as possible. After it dries, you can pump the tire up and drive safely for some time.

NOTE: Remember that such repairs are suitable only for tread damage. If you fix the sidewall like that, the tire may blow out any moment.

Repairing the Valve Stem

You will need a valve removal tool and a new valve core. You may also need a car jack and a lug wrench to remove the wheel if you find it easier.

Remove the valve core on the wheel where the tire loses air slowly by inserting the removal tool tip into the stem and rotating it counterclockwise. If you see signs of corrosion, make sure to clean the stem before installing a new core. Screw a new core in place and pump the tire up.

NOTE: Make sure to wear protective glasses, as the old core or debris from the stem may hit you.

Repairing and/or Restoring the Rim

If you have a bent wheel, it’s better to go to a mechanic that offers hydraulic assistance. This is one of the newest and most efficient ways to straighten a wheel.

NOTE: Never hammer your aluminum alloy wheels, or they may become totally broken. Aluminum is quite brittle, so more gentle means should be used to fix such rims.

What you can do yourself is clean the wheels from corrosion, as this is one of the reasons why a tire loses air slowly. You will need to remove the wheel from the vehicle and dismount the tire. Then you will need sanding tools, aluminum metallic polish, and wax (optional).

Clean the wheel and degrease it, then remove all the paint and previous finishes. Sand all its parts thoroughly, including the space in between the spokes and inside the lug-nut holes. Use a low-speed sander to clean the center of the rim, and polish it all until it gets shiny again. Let it dry and apply wax if you find it appropriate.

NOTE: This is only one of the methods for cleaning a wheel of signs of corrosion. You can alter it according to your wheel type and manufacturer specifications. You should also wear protective glasses and gloves to ensure safety.

Maintaining Proper Inflation

  • Check routinely.
    Check air pressure in your tires once a week to make sure you know whether any tire loses air slowly but more than the others.
  • Check when cold.
    Make sure you check the tires while they are cold. It’s not mandatory to wait for a lot time for the tires to cool down – 2 hours should be fine. Also make sure the car has been in the shade before you check the pressure.
    If you’ve been driving for over 15 minutes or the car has been in the sun, remove 2 psi to see the real inflation rate.
  • Use a calibrated pressure gauge.
    At some tire stations they calibrate pressure gauges, and you should do it to get the right reading. As a tire loses air slowly, every psi loss is important to notice. Even a new gauge may show about +/- 3 psi, which is quite a lot of change for light passenger cars. Also, choose the most appropriate tire gauge type for you: stick, digital, or dial. You can see their benefits and drawbacks by reading a buying guide.

Searching for Recommended Air Pressure Information

Read your vehicle owner’s manual or look for the information placard on the door jamb. There you will find both the maximum load/inflation and the recommended amount.Image source: bridgestone.com.sgIt’s crucial that the tire load index is the same or exceeds the index you see on the placard. The information on the load index can be found on the sidewall of the tire as a part of its code.


Tire Pressure Monitoring System is present in every vehicle manufactured after 2007. It helps detecting whether any tire loses air slowly and excessively. When pressure goes lower than 25% from the recommended standard, the system warns the driver with a sign.Image source: www.autoserviceprofessional.comUnfortunately, according to a survey, only 58% of drivers can identify the sign. 21% won’t believe their vehicle systems and will continue driving until they can see the damage themselves. Nevertheless, TPMS is a mandatory system approved by NHTSA and a great help for those who use it.

Why Tire Pressure Is Important

Tire pressure influences the following things:
  • Safety.
    About 75% of roadside flat tires happen because of negligence when a tire loses air slowly.
  • Load-carrying capacity.
    A vehicle only can carry the specified load if the tires have enough air in them.
  • Tire lifespan.
    Proper tire pressure prolongs the tire’s life, as if over- or under-inflated, the tire starts to wear irregularly.
  • Fuel consumption.
    Improper tire pressure may increase fuel consumption by about 3%.
Improper pressure will provide less stability for the vehicle and more risk of flats and blowouts. For light passenger cars, the average psi standard is 35, and such tires become dangerous at 28 psi. So, even 5-7 psi makes a difference. Therefore, when one tire loses air slowly but more than the others, it needs attention.
Old 09-14-2018, 07:19 AM
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I know I am sidetracking this thread, but Roadie is in Wilmington NC.

Looks as if Wilmington is just about ground zero for Florence.

Hope you are safe man!
Old 09-14-2018, 08:05 PM
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Looks like a pretty bad storm.

Hope you're doing okay.
Old 09-15-2018, 12:31 AM
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Old 09-15-2018, 10:37 PM
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Thanks for the well wishes. The worst of the storm hit about 6:00am yesterday taking out the power, 98mph with gusts to 115mph. One small pine tried to fall but the next tree caught it. I'll have to remove it and some other bushes and vegetation was damaged but I feel lucky that the damage was minimal. Across the street, a big pine came down but it fell away from the neighbors house. The power was off for 29 hours which really reminded me of how much we depend on our electricity. I did board up the windows and buy a generator to keep the fridge going as well as provide some light and recharge the iphones. The Verizon supported cell phones worked well the whole time with Verizon giving everybody unlimited data for 3 days. The street flooded but no worse than it usually does when a big rain storm comes through. The storm is barely moving and it's still raining off and on with some wind. There were a couple of tornado warnings this evening for an area about 15 miles away. All in all, I'm happy it turned out this well for me.
Old 09-16-2018, 02:51 AM
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ive seen chrome wheels peeling and corroded in the bead area causing issues. if thats the case, and you're lucky you can get the chrome to chip off at the bead and let the tire seal up properly, but usually it means buying new wheels

I've also seen alloy wheels that are on their 3rd or 4th set of tires and there is a serious accumulation of tire install soap along the bead of the wheel, that can be lumpy and cause the tire not to sit perfectly flat and cause a slow leak. Break down the wheel, scrub the wheel clean, and reinstall the tire
Old 09-16-2018, 11:59 AM
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Ding ding, Patman is right on.

I finally found someone that knew what they were doing. The wheel lip had a powdery corrosion (aluminum breaking down) and the bead wasn't creating a good seal against the rim.

They thoroughly washed the inside of the tire and bead, along with the rim with Dawn dish soap and a scrubber. Then got bead sealer and applied a very thin amount.

Hopefully this will fix my issue.

They did say it could've caused a blow out, especially on the steer axle with a bad bead if the sidewall flexed enough.

Good to know, and glad I got it fixed.
Old 09-16-2018, 02:06 PM
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Old 09-16-2018, 05:42 PM
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Good news!

******* I just hate we helped fix a Jeep Compass**********

Old 09-16-2018, 08:12 PM
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Yes you did... haha

In any event, it's a reliable vehicle, just the suspension and brakes are total, absolute garbage design. From working on it many times, there are better designs out there.

When the suspension is OK, it's not a bad vehicle to drive. The engine is amazingly robust and since I have the NVG 5 speed, it's powertrain is practically bulletproof. I mean you ain't gonna win any races, but I can bet my bottom dollar she'll start every single time and get you from point a to point b.

Would I buy another? Nope.

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