Under pressure
February 28, 2017 6:32 PM   Subscribe

I've been told that replacing my car's wheels/rims will resolve a frequent low-pressure problem. What does the green think?

I have two relatively new Nokian tires on my 2008 Honda Fit Sport, with original wheels/rims. The newer tires are apparently tubeless. I can probably give more information on the exact tire if needed.

For about a year now, I've had to take the car into the tire dealer every couple of months because of frequent low pressure in one tire. They do something with the rim, put the tire back on, things are good for about a month, and then it starts up again. I'm not sure whether it's the same tire each time or not.

The dealer does this for free, which is great, but I'm sick of going over there so frequently AND I'm sick of seeing the indicator go off every two weeks. One of the service reps told me last time that if I replace the wheels/rims, the problem should go away. He didn't seem that keen on telling me about this, which makes me think it's NOT a sales tactic.

I'm not confident at all that it's not actually a slow leak in one tire.

My next move is to take it into my car dealer to have them look at it: they're good diagnosticians there, but I didn't buy the tires there (not that it matters).

All thoughts/ideas welcome.
posted by Sheydem-tants to Travel & Transportation (13 answers total) 1 user marked this as a favorite
Tires lose pressure over time. There are a bunch of factors in how quickly (temps, driving style, type of tire) but all tires will eventually lose pressure.

If you are losing more in one than the other, then yes, you probably have a slow leak. And it would pay to see if you can get it fixed. If its the same position, but you have rotated your tires (so not the same tire) - then you need to not hit curbs so much.

If your tires really are original, I would recommend replacing them - tires should be replaced about 5 years or at 1/8" tread depth, whichever comes first. If your rims were an issue, you would know it by looking at them.

All of the above having been said, having to check/inflate your tires every few weeks should be a regular thing you do. Every two weeks is too often, but probably 4-6 anyway.
posted by Pogo_Fuzzybutt at 6:45 PM on February 28, 2017

I used to have to add air to my truck's OEM tires about once a month. At 50k I got 4 new tires. Same brand, different line. 25k later and I never have to add air to these tires. I still check every month or two but only add a couple pounds of air maybe every 6 or 9 months now.
posted by LoveHam at 7:01 PM on February 28, 2017

My 2012 Fit's TPMS sensors used to be super sensitive, lighting up every time the temperature dropped by 20 degrees. When it was time to replace them, I bought new tires from Costco, where they use nitrogen to fill them. It hasn't gone off since.
posted by zepheria at 7:05 PM on February 28, 2017

My vehicle had corroded, rusty rims and the same problem with persistent low tire pressure; I carried around a small, lighter-plug powered air pump just in case, and used it regularly. Replacing the rims fixed that.
posted by lathrop at 7:25 PM on February 28, 2017

If your rims are bent or corroded, this will cause your tires to lose pressure faster than they normally would. If it got bad enough you could even run the risk of a tire blowout, which can be dangerous. So it's definitely possible that's what's going on. But your mechanic should be able to actually visually show you where your rim is bent or damaged. Ask them to show you, then you'll know you're not being ripped off.
posted by katyggls at 7:54 PM on February 28, 2017

Just fyi, because it implies you don't know this - all automotive tyres are tubeless. The practice of putting tubes in is long gone for standard passenger tyres.

Now, to your issue - Yes, it is possible that new rims could fix it. The surface of the wheel (a wheel is a rim is a wheel, it's the same thing) that the tyre bead sits on can corrode, which means a non-smooth seal between wheel and tyre, and so air can pass between the two very slowly over time, resulting in a slow puncture. Heat cycles (day to night or just driving the car then it sitting) can accelerate that differential expansion and affect the loss of air.

BUT. Tyres do deflate over time. You should be - as soon as you know you have a tyre inflation issue - be checking these pressures regularly (weekly at least, ideally more often until you know you can afford to wait a whole week). Driving on a poorly inflated tyre is bad for the tyre and bad for roadholding, and you shouldn't be relying on your tyre pressure sensors if you know you have a recurring issue - they may be set low enough to stop damage to the actual tyre or similar, but not sensitive enough to prevent a safety issue with tyre inflation pressures. Unless you have actual tyre pressure monitoring (ie it displays a psi reading for all four wheels somewhere on the dash) the tyre pressure warning should be considered to be a double check - you're supposed to have picked up a problem BEFOFE the sensor goes off. Do not assume that everything is fine if the sensors aren't displaying an issue.

If it is just one tyre/wheel you are having the issue in and they are sure it isn't a slow puncture in the tyre, then replacing one wheel is a perfectly good way of rectifying this. There is no need to replace any wheels that don't have an issue. You can even pick up a second hand wheel if it is in good condition - so breaker's yard/used car parts scrapyard type place.
posted by Brockles at 8:08 PM on February 28, 2017 [7 favorites]

zepheria: "I bought new tires from Costco, where they use nitrogen to fill them. It hasn't gone off since."

Note that it is the replacement of the tire and/or the service to the rim bead surface that fixed the leak not the use of Nitrogen (which is mostly a gimmick unless you have special needs).
posted by Mitheral at 8:23 PM on February 28, 2017 [1 favorite]

Every few months is about the time that tires need to be pumped up. It may be that one of your tires is slightly leaky or that one of the tire pressure systems is slightly more sensitive.

You could buy an air pressure gauge and check the pressures the next time this happens. If all of the tires are within a few PSI then the issue is normal leakage and you should pump the tires up more often.

It could be corrosion on the bead seat of the rim. Normally this only happens with older steel rims that have been exposed to salt.

The next time this happens you could ask the dealer to swap the problem tire from one side to the other. If the problem follows the tire then the fault lies there. Otherwise it is the rim.
posted by pdoege at 8:29 PM on February 28, 2017

not the use of Nitrogen (which is mostly a gimmick unless you have special needs).

Worth repeating for emphasis. There are actually measurable gains from Nitrogen, so it isn't *exactly* snake oil, but these gains are teeny, teeny tiny and effectively invisible in actual benefits to the majority of people with a standard road car and standard usage. It's effectively worthless. It is mainly used to try and make sure people come back to the same tyre shop more (because there are less people with nitrogen than normal compressed air).

Normally this only happens with older steel rims that have been exposed to salt.

Agreed as more common historically, but it also happens with alloy wheels that are produced cheaper as the lacquer or paint can lift and expose a an air path or even expose raw aluminium to corrosion. It isn't an issue with just one type of wheel any more.
posted by Brockles at 8:37 PM on February 28, 2017 [1 favorite]

This is probably not going to apply, but it happened to me, so I am still going to ask.

Are you certain that the new tires are the right size? As listed in the car's manual?

Sometimes car places, possibly even dealerships, will sell a person tires that don't actually fit their car's wheels when they don't have the exact size in stock. Mostly this isn't a huge problem, but before I started to learn about cars I had this happen to me. An actual tire shop deliberately sold me the wrong size tires, rather than tell me that they didn't have my size in stock or send me to one of their other locations that might have had them. The end result was exactly what you are describing. I had one wheel/tire that had a constant slow leak. The tire was fine, but on the one wheel the seal was never quite right no matter how often it was checked or remounted. It was not until 10 years later when I was looking for new tires and had learned a lot more that I realized that the tires I had were the wrong size. The new tires I bought, of the correct original size, do not have this issue. They stay inflated perfectly and evenly. This is on the car's original wheels, which are mag alloy from 1994.

I second Brockles and others, it is important to not drive around on underinflated tires. Correct pressure is safer and feels better to drive on, and saves you money in gas milage and wear on the tires. A small air compressor for filling your own tires is not a lot of money, and it is much simpler to just do at home than having to go to the dealership or even a gas station to fill your tires regularly. The correct pressure should be listed in the manual or on a sticker, probably in the driver's door area.
posted by monopas at 12:46 PM on March 1, 2017

I had this happen with a tire awhile ago, and the shop "ground down / buffed / steel-brushed"* the rim where the tire sits, to remove any corrosion and ensure a tight seal. That took care of it; did not need to purchase a new rim.

*I don't recall the exact term; it was nothing special -- here in the great road-salted North, it was a common procedure.
posted by Bron at 12:52 PM on March 1, 2017

Every driver needs to carry a quality digital tire gauge (the cheap pen-type analog gauges are notoriously inaccurate). You should check your tire pressure (spare included!) regularly. My rule is every 3 fill-ups if I'm around town, and always before and during long road trips. Temperature changes alone can cause pressure to vary by several pounds.

In 35 years of driving I've never heard of tires that don't need air for periods of 6 months or more, as is being described in this thread.

Don't rely on the TPMS. Check your pressures and your fluid levels manually on a routine schedule. Once a month would be the bare minimum, in my opinion.

While you're at it, visually inspect your tread and sidewalls. A blowout is a very scary thing that can kill you or others if it happens at speed or inn bad conditions. Your property inflated and inspected tires are vital to road safety.

What else you gonna do while your gas is pumping?

Also unmentioned so far in answers, proper inflation plays a very significant role in fuel mileage, as well as ride, handling, grip, and braking.
posted by spitbull at 5:26 PM on March 1, 2017

The end result was exactly what you are describing. I had one wheel/tire that had a constant slow leak. The tire was fine, but on the one wheel the seal was never quite right no matter how often it was checked or remounted.

To address this, it is almost certainly completely unrelated to the tyre size being different - its just confirmation bias that the problem went away when the tyres were changed for a different size. It could just as easily gone away with tyres being changed for new ones of the same size. Without more information, the size may not even have been 'wrong' just a different option for the vehicle. Particularly and especially because the other three tyres sealed fine. I suspect that whatever was wrong with the problem wheel was either fixed when the newer, different sized, tyres were put on, or the newer tyres were a different *tyre manufacturer* and so the bead seating profile was slightly different and the problem with the wheel no longer was a factor.

To have an air sealing issue through the wrong sized tyre, the difference would have to be significant and I've never seen a slow leak from that (certainly not on one tyre only) from such a problem, but I have seen tyres unseat from the bead or cause handling issues. There is a sizable range of tyres that can be fitted to the same size wheel.
posted by Brockles at 10:19 PM on March 1, 2017

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