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#1
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tire pressure- what's the right value for an 02 530i?
Hi:
I've just taken the summer tires 234/45-17Y off my 2002 530i. I now have my Hakapellita 1 215/55-16T tires on. In the manual, and on the door, it tells me to use 33 psi front and 41 psi rear based on "std temperature". The auto shop that I trust, and does BMW and Porches work, told me to use 35 psi, front and rear. My dealer didn't give me a number; they just said follow the book ;( So what do others do? I live in Canada and winter tires are a must. In the summer we get over 30C and in the winter it can be colder than -30C. Thus it's important to check tire pressure at least evert season. Also do others de-rate their tire pressures during colder weather or do you keep the pressure constant regardless of season/temp. Since the current temp is -2C/29F, I used 31f & 39r. There are much lower numbers on the door pillar for non USA/CAN drivers. I don't know why. Please post any updates to this NG. Thank you. - Walter |
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#2
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"Walter" > wrote in message . .. Let's see if we can resolve this "question of ages" once and for all. 1-The only absolute when it comes to tire pressures is the maximum. This is the number stamped on the sidewall by the manufacturer. It should never even be close to what you inflate the tire to, it is just a warning that the tire is not meant to be inflated over that figure. This is the only number that comes into play as far as the tire is concerned. 2-As far as the VEHICLE is concerned, this is where the confusion arises. The manufacturer will indicate recommended pressures for front and rear based on the load of the vehicle. The more people or stuff you put in the car, the higher the number will be. This is only a GOOD STARTING POINT. 3-From the starting point, you may want to increase or decrease the pressure depending on what you are trying to achieve. Comfort, life of the tire, increase or decrease understeer by adjusting either the front or the back tire pressures, etc. I'm not going to go into detail about these objectives, especially altering handling characteristics, because unless you are driving in a manner where you are cognizant of under/oversteer, it probably won't matter enough to you to try and change it. If you are aware of these things, then you should know, or know how to find out, the changes that need to be made to alter the handling to your preference. 4-The whole idea of cold or hot inflation temperatures is also much overdone. Tire pressure will vary according to, ultimately, the temperature of the tire and the air in it. Again, it won't make much difference if you inflate your tire to x lbs. hot or cold, unless you can detect it. Also, unless you are inflating the tire in the Arctic and driving it in Death Valley it won't be critical. The easiest thing to do about this is just inflate the tires to a starting pressure, get them up to operating temperature, then adjust the pressures to achieve your intended result. Note these pressures when warm, then note them when cold, and these will be your desired pressures whether you check them in your driveway when it's been cold all night, or after you are driving for 6 hours and pulling into a gas station. 5-Very important. NEVER NEVER trust the pressures as indicated by gas station pumps. You could guess the pressure just as well by kicking the tire. Buy yourself a nice digital gage and be confident. 6-If all of this sounds too complicate, just use the pressures as indicated on the car door jamb, which are always cold inflated pressures. Ok? |
#3
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"Walter" > wrote in message . .. > Hi: > > I've just taken the summer tires 234/45-17Y off my 2002 530i. I now have > my Hakapellita 1 215/55-16T tires on. > > In the manual, and on the door, it tells me to use 33 psi front and 41 psi > rear based on "std temperature". > > The auto shop that I trust, and does BMW and Porches work, told me to use > 35 psi, front and rear. > > My dealer didn't give me a number; they just said follow the book ;( > > So what do others do? I live in Canada and winter tires are a must. In the > summer we get over 30C and in the winter it can be colder than -30C. Thus > it's important to check tire pressure at least evert season. > > Also do others de-rate their tire pressures during colder weather or do > you keep the pressure constant regardless of season/temp. Since the > current temp is -2C/29F, I used 31f & 39r. There are much lower numbers on > the door pillar for non USA/CAN drivers. I don't know why. > Since the tire pressure will effect the handling of the car and wear of the tires, its best to go by what the car manufacturer says. Go by what's on the inside of your door. Also, check your tire pressure weekly. I've seen coworkers who never check their tires have flats this time of year when the temperature gets real cold compared to when they had them filled up last summer. Kyle. |
#4
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"Kyle and Lori Greene" > wrote in message ... > > >Tire inflation pressures also fluctuate with changes in the outside air >temperature. This occurs at a rate of about 1 psi for every 10°F (plus or >minus). So the tires you set correctly with an 80°F ambient temperature >will be under inflated by 6 psi at 20°F. |
#5
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That's pretty dramatic. Do you think that the calibration stamps at petrol
stations from leading suppliers such as Shell or BP are unreliable? In the UK there is an increasing number of pumps that one can preset on a digital display. Air is pumped in until the set point is reached. Are these also no good? DAS -- For direct contact replace nospam with schmetterling --- "tech27" > wrote in message o.verio.net... [...] > 5-Very important. NEVER NEVER trust the pressures as indicated by gas > station pumps. You could guess the pressure just as well by kicking the > tire. Buy yourself a nice digital gage and be confident. [...] |
#6
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Dori A Schmetterling wrote:
> That's pretty dramatic. Do you think that the calibration stamps at petrol > stations from leading suppliers such as Shell or BP are unreliable? > > In the UK there is an increasing number of pumps that one can preset on a > digital display. Air is pumped in until the set point is reached. > > Are these also no good? > > DAS I personally would not (do not) trust them, since they would vary from station to station. Nor do I suggest checking the air pressure at a gas station anyway (unless you live there) since you will have driven some distance to get there and the tires will no longer be "cold". I always check tire pressure in my own driveway after sitting (at least) overnight. I use the same handheld pressure gauge every time so its absolute accuracy is unimportant. I have a small air compressor (picked up (inexpensively) at a department store many years ago) to adjust the pressure as needed. -Fred W |
#7
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Although I am given a manufacturer's pressure adjustment for warm tyres I
can never tell how warm they really are after 50 miles or 200 miles (presumably there is an equilibration point somewhere). So I always measure cold (the recommended practice, of course) or 'near cold' as I don't think that a short gentle drive makes much difference to the temp. (Or does it?) DAS -- For direct contact replace nospam with schmetterling --- "Fred W" > wrote in message ... > Dori A Schmetterling wrote: >> That's pretty dramatic. Do you think that the calibration stamps at >> petrol stations from leading suppliers such as Shell or BP are >> unreliable? >> >> In the UK there is an increasing number of pumps that one can preset on a >> digital display. Air is pumped in until the set point is reached. >> >> Are these also no good? >> >> DAS > > I personally would not (do not) trust them, since they would vary from > station to station. Nor do I suggest checking the air pressure at a gas > station anyway (unless you live there) since you will have driven some > distance to get there and the tires will no longer be "cold". > > I always check tire pressure in my own driveway after sitting (at least) > overnight. I use the same handheld pressure gauge every time so its > absolute accuracy is unimportant. I have a small air compressor (picked up > (inexpensively) at a department store many years ago) to adjust the > pressure as needed. > > -Fred W > |
#8
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If you are driving from your house to the corner gas station, the tires will
remain cold for the purposes of this discussion. I would put more faith in the digital type of filling hose, but I carry my own tire pressure guage in the car. I happen to own a compressor, so I have the luxury of being able to fill my tires at home if I want, but if I managed to get away from the house and notice I have a low tire, stuffing in 30psi is good enough for the vast majority of people. It is reasonable that all cars take 30psi as the default tire pressure, then as the tires get older, this can be adjusted up or down a few psi to acheive proper treadwear. If you have been driving for 50 miles, then the tire pressure will be raised as a result of the heat build up, but even if you put in 30psi while hot, the tires should remain in the range of 25 ~ 28psi when cold, and this is fine for everybody by racers. My advice is to always put equal amounts of air in both tires on the same axle. In a perfect world, we would put air in all 4 tires at the same time, but in the real world we tend to air one tire only - especially if the weather sucks, our hands are clean and we are on the way to a meeting, our suit is freshly pressed and out of the cleaners, or any number of crappy excuses for doing a half-assed job - but we should always at least do both tires on the same axle. If you put 30psi in the left rear, then also put 30psi in the right rear. Same for the front, whatever you put in the left front, put in the right front as well. If you have the time or inclination to do the other axle, then fine, but always do both ends of the same axle at the very least. Most cars take 30psi both front and rear under the majority of "normal" operation conditions. Sure, there are exceptioins to the rule, but the exceptions are just a few pounds, and over the life of the tire, a few pounds isn't going to make much difference, and if it is, you can see it by looking at the tires and adjusting the air pressure as needed. Tires leak, so overfilling by a pound or two will take care of itself in a couple of weeks. Undefilling causes the tires to wear on the edges (both edges of the same tire), overfilling causes tires to wear in the center. Alignment causes only one edge to wear (one edge on one or more tires), and frequent rapid accelleration causes the rear tires to wear on the inside edge (inside edge of both tires). Mixing improper air pressure with alignment or accelleration styles can influence the wear patterns I described. "Dori A Schmetterling" > wrote in message ... > Although I am given a manufacturer's pressure adjustment for warm tyres I > can never tell how warm they really are after 50 miles or 200 miles > (presumably there is an equilibration point somewhere). > > So I always measure cold (the recommended practice, of course) or 'near > cold' as I don't think that a short gentle drive makes much difference to > the temp. (Or does it?) > > DAS > -- > For direct contact replace nospam with schmetterling > --- > > "Fred W" > wrote in message > ... > > Dori A Schmetterling wrote: > >> That's pretty dramatic. Do you think that the calibration stamps at > >> petrol stations from leading suppliers such as Shell or BP are > >> unreliable? > >> > >> In the UK there is an increasing number of pumps that one can preset on a > >> digital display. Air is pumped in until the set point is reached. > >> > >> Are these also no good? > >> > >> DAS > > > > I personally would not (do not) trust them, since they would vary from > > station to station. Nor do I suggest checking the air pressure at a gas > > station anyway (unless you live there) since you will have driven some > > distance to get there and the tires will no longer be "cold". > > > > I always check tire pressure in my own driveway after sitting (at least) > > overnight. I use the same handheld pressure gauge every time so its > > absolute accuracy is unimportant. I have a small air compressor (picked up > > (inexpensively) at a department store many years ago) to adjust the > > pressure as needed. > > > > -Fred W > > > > |
#9
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No. I've never seen one that is any good, but then all I ever see are the
ones with a stick type reading on the business end of the air hose. I've yet to see a digital display type, but in any case I would still check the pressure with my own guage. "Dori A Schmetterling" > wrote in message ... > That's pretty dramatic. Do you think that the calibration stamps at > petrol stations from leading suppliers such as Shell or BP are unreliable? > > In the UK there is an increasing number of pumps that one can preset on a > digital display. Air is pumped in until the set point is reached. > > Are these also no good? > > DAS > -- > For direct contact replace nospam with schmetterling > --- > > "tech27" > wrote in message > o.verio.net... > [...] > >> 5-Very important. NEVER NEVER trust the pressures as indicated by gas >> station pumps. You could guess the pressure just as well by kicking the >> tire. Buy yourself a nice digital gage and be confident. > [...] > |
#10
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"Jeff Strickland" > wrote in message ... All correct. Just a FYI - for normal driving set the tire pressure when cold. When we track the cars, we inflate to around what we think we will want, then take 3 or 4 laps to heat up the tires to racing temps, then pull in and immediately check and adjust the pressures to what we want to run at given the chassis settings, type of track, etc. |
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