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View Full Version : Need help with tire pressure.I swear read the manual and searched.


eraserhead
02-18-2006, 05:35 PM
Ok, please before you start flaming me, or saying RTFM, I read the manual, searched the posts, looked at the door pillar, it is just too confusing for a car enthusiast wannabe. I have a 2003 335 ci with 225 tires that I got about 2 weeks ago. The car must have been sitting a couple of weeks in the dealer, it was certified so I am assuming the tires should have been checked about a month ago. Now since then, the weather got unusually cold (in Orlando/Fl) and temps went to around 36 F degrees for a week. I got myself a digital pressure reader today and measured the front tires at 26 psi and back around 25.5 psi. The manual suggests 30/35, the posts suggest 34/35 or even higher for sporty driving. I use it to go to work about 25 miles total everyday so from what I understand 34/35 would be sufficient for me. But my real question is: is it possible for tires to fall 5/10 psi in a month? What pressure would be best for an average user? and this one is going to sound real naive but I have never put pressure on any tire, my wife did, how do I put pressure? Please help me, I am dying to go out and put pressures now, although I just drove, and it is dark outside. My wife is thinking I am going too crazy over the car?

Thanks in advance.

chuck92103
02-18-2006, 05:38 PM
You are assuming the dealer set the pressure correctly. No proof of that so don't assume.

Instead, set the pressure to your liking and check again in one month. :thumbup:

govtec
02-18-2006, 05:48 PM
and how long have u been driving? u've never pumped any types of balls before? besides ur own?j/k:rofl: go to a gas station that have air pumps available...step 1)insert correct amount of coinage into machine. step 2)twist tire cap off and insert pump into opening. step 3) press lever and pump air into tire (there should be a mechanical gauge attached to the pump itself to let u know approximately how much psi is currently in ur tire. step 4) pump all 4 tires until it's a little bit overinflated and use ur digital gauge to attain desired psi amounts. step 5) wash ur dirty hands and rejoice

jillyjellyroll
02-18-2006, 06:09 PM
and how long have u been driving? u've never pumped any types of balls before? besides ur own?j/k:rofl: go to a gas station that have air pumps available...step 1)insert correct amount of coinage into machine. step 2)twist tire cap off and insert pump into opening. step 3) press lever and pump air into tire (there should be a mechanical gauge attached to the pump itself to let u know approximately how much psi is currently in ur tire. step 4) pump all 4 tires until it's a little bit overinflated and use ur digital gauge to attain desired psi amounts. step 5) wash ur dirty hands and rejoice

also, when you are inserting the nozzle into the tire stem (i.e. pumping air) make sure you push straight. you should hear the hissing sound within the tire, not the "whoosing" sound indicating that you are losing air...

easiest way to learn is to go out with your wife, and have her demonstrate. then practice!

MMME30W
02-18-2006, 06:22 PM
But my real question is: is it possible for tires to fall 5/10 psi in a month? What pressure would be best for an average user? and this one is going to sound real naive but I have never put pressure on any tire, my wife did, how do I put pressure?



:wave:

First, relax, it is normal to obsess about these cars ;)

Second, to your questions:

1) Sure it is. I did basically the same as you; I didn't check mine for about 2 months and found them 8-12 psi too low in the recent cold snap (I'm in Orlando too, near Oviedo).

2) An average user is typical load up to 4 persons. Lets assume you meant to say 325ci (335?) with 17" 225ZR tires all around. If you check the door jamb, you should find that for typical load you should set them to 32 psi front, 38 psi rear. If you do continuous high-speed driving, or might want the set up a little stiffer, you could do 34 psi front 40 psi rear.

Another thing some folks do is to adjust the handling with tire pressure. If you add say 2 psi to the front, you will generate a bit more grip and thus decrease the understeer. YMMV of course.

3) Filling the tires is not too difficult. You have the gauge, that's good. To check, unscrew the tire valve cover from the stem. Put the gauge squarely on the stem, and press firmly, so no air escapes. Hold briefly, then release and read. This takes a slight knack.

To fill, you can use gas station air hoses, the same principle applies to fill as for checking. Just don't put too much in at one time and overfill. Say 3-4s at a time, until you get an idea of how much air goes in.

Or you can get a foot pump (this is what I have) and use it at home.

Good luck and let us know how it goes!

eraserhead
02-18-2006, 08:08 PM
thanks a lot to everyone, first thing in the morning i will go to a 7-11 and do as explained here. Yeah I meant 325 ci, i know about it that much. It just seems a little hard to believe people I see on the road everyday check tire pressures twice a month like it is suggested. They probably don't. We had to change the tires on our rav4 after 2 years of buying it. I guess not checking tires EVER is why it was that early for a new car.

eraserhead
02-18-2006, 08:11 PM
hey wingspan I am in the altamonte area but I work in the ucf area. I am not liking altamonte too much because of the traffic and the aggressive cops. where you live should be a better place to live I am guessing.

MMME30W
02-18-2006, 08:29 PM
hey wingspan I am in the altamonte area but I work in the ucf area. I am not liking altamonte too much because of the traffic and the aggressive cops. where you live should be a better place to live I am guessing.

:wave:

cwsqbm
02-18-2006, 08:50 PM
It just seems a little hard to believe people I see on the road everyday check tire pressures twice a month like it is suggested..

On my truck, I don't check the pressure but instead do a walk around when getting into the truck. With the high profile tires, its easily to spot a low pressure tire. On my BMW, a tire can be down a bit and still look ok, so I check every couple weeks during driving season, and before long road trips, and four times or more a day at track events.

Pinecone
02-19-2006, 05:53 AM
Some of use have been known to check our tire pressures several times in a DAY, but taht is for track or autocross.

Yes, you should be checking your tires weekly. Tires can lose 1 psi per week under normal circumstances. Older weather increases the psi drop ue to colder air being taking up less volume. Add in any type of leak and you can lose lots of air.

The number one cause of tire failure is low tie pressure. And with a steel belted radial by the time it looks low you are down in the 15 - 20 psi range, which is dangerously low.

If you are obsessing about your car, check the tires at least once a month, preferably weekly.

As for pressure, never run LESS pressure than the door sticker. And I always suggest running the loaded pressure (people and luggage) as you are unlikel y to stop and add pressure if you add load.

An extra 2 -4 psi will actually increae grip so many run a bit higher, but not above the number on the tire sidewall.

One last thing, check and set tires presures COLD. That is with the car not haveing been driven for several hours (at least 3 - 4). Otherwise you will have the actual pressure set too low. If you don't have air at home, check them at home, write down each one. Figure how many psi you need to add to each tire, then drive to the 7-11 or gas station, and check the tires again, add the asmount of air you figured out at home. Which will bring you to a higher pressure than you expect, but that is OK< you are compensating for the hotter tire having incresed pressure, which is OK.

Example, you decide you want to run 40 all around. You check at home and the front show 35 and the rears 37 so you need to add 5 to the fronts and 3 to the rears. You drive to the air suppply. You check them, you find the the fronts are now 38 and the rears 39. So you pump the fronts up to 38 + 5 = 43 and the rears to 39 + 3 = 42. The next morning if you are so obsessive you check them again, they should be 40 all around.

Pinecone
02-19-2006, 05:54 AM
On my truck, I don't check the pressure but instead do a walk around when getting into the truck. With the high profile tires, its easily to spot a low pressure tire. On my BMW, a tire can be down a bit and still look ok, so I check every couple weeks during driving season, and before long road trips, and four times or more a day at track events.

If they are steel belted radials, they wil still not look low until way too low. Think Firestone on Explorers. A lot of their problem was a specified tire pressure of about 26 psi, coupled with people hot checking tire pressure. Yes, some manufacturing defects helped also, but low tire pressure caused a large part of the problem.

The high profile tires on our Jeep Grand Cherokee could be under 18 psi before they "looked" low.

rwebbe
02-20-2006, 09:20 PM
The Contis and Kuhmos used air every 2 weeks. The top of the line Michelins following bedding in on rims use little or no air. I found same to be true on my '97 528. I should add top of the line make a BMW steer and hold road like glue compared to other tires. Sure, 950 bucks for 4 with warranty etc, out the door (Tire Rack) is big stuff, but BMW big car and worth it.;) :)

avalys
02-20-2006, 09:50 PM
On my BMW, a tire can be down a bit and still look ok
That's funny, I've noticed the exact opposite: my tires always look low even when they're properly inflated.

eraserhead
02-20-2006, 11:30 PM
having to check tires cold is so true. I was about to go to a 7-11 after driving on saturday when I read 25.5 psi. The next mornng they were 22-23.5. What a difference.? I just found it hard to match tires exactly in terms of pressure. Is it a big deal if there is a 0.5 or 1 psi difference between tires?

FenPhen
02-21-2006, 12:37 AM
having to check tires cold is so true. I was about to go to a 7-11 after driving on saturday when I read 25.5 psi. The next mornng they were 22-23.5. What a difference.? I just found it hard to match tires exactly in terms of pressure. Is it a big deal if there is a 0.5 or 1 psi difference between tires?Driving around on your tires will warm them up and easily add several psi. Measure them cold, calculate how many psi each wheel needs. At the pump, measure again, and then add the psi you calculated beforehand. Best to overfill a little bit, then check the next morning and bleed air out as necessary to get them just right.