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[jetblackone]

Question for you all:

Got the 128i back from the dealer after changing out my winter wheel set and found that the pressures were set to 40 front/45 rear. The factory spec (from the front door jamb plate information) is 32 front/35 rear. Anyone care to comment on the pressures set by the dealer ?

[FedeM]

Originally Posted by jetblackone

Question for you all:

Got the 128i back from the dealer after changing out my winter wheel set and found that the pressures were set to 40 front/45 rear. The factory spec (from the front door jamb plate information) is 32 front/35 rear. Anyone care to comment on the pressures set by the dealer ?

I use 30psi allround... Mi factory spec is about 38f/43r, but I live in Italy...

[Walt White Coupe]

Yea, they are incompetent.

[Tom K.]

Originally Posted by Walt White Coupe

Yea, they are incompetent.

That's what I would have assumed, but after my excellent local tire shop returned my 128i with 35/39 instead of 32/35, I'm going to double check the accuracy of my tire gauge.

Tom

[jetblackone]

Good point Tom. I've been using a USA made pencil guage, which I assumed was accurate. I just ordered a Longacre dial guage and will see what that says once I get my greedy hands on it...

The unanswered question remains: Given that my gauge is accurate (or nearly so), does the dealer know something I don't as to why the tires should be 8 - 10 pounds over the factory specification ? My instinct is to trust the factory, but I'm open to new knowledge...

[FDM68]

I think they are just clueless. I dropped my wife Mini off for a service check at the Bimmer dealership. When I got it back one rear tire was about 12lbs over and the other rear was 16lbs, but incidently the fronts were fine. I was like what the hell??? Got to keep an eye on them. As far as my 1er I have them set to the recommended for vehicles traveling at or above 100.

[Tom K.]

Originally Posted by TrackRat

There's no point in excessive pressure. Dealers don't hire rocket scientists to change tires. 5 psi higher for sustained A-Bahn cruising is fine but for the U.S. there's little need for excessive pressure. It's also possible the dealer's tire gauge is off or the tire changer hung-over... Many dealers are notoriously inept.

Also, it's generally safer to set the tires 5 lbs. over spec rather than 5 lbs. under (assuming the maximim allowable psi is not exceeded). The dealer may be allowing for both a fully loaded and high speed setting. Naturally, there is no substitute for checking it yourself - making certain the tires have cooled down to get an accurate reading.

Tom

[VMRWheels]

Pressures are a bit high. I generally run around 35-36 front and around 38 rear.

-Charles@VMRWheels

[jetblackone]

Charles - what is your rationale for your tire settings ? And are they for a 128 or 135 ?

By the way, I'm aware of the 100mph plus specification, but use the lower (softer) spec for the improved ride quality. Also, I figure a softer tire will provide more rim protection...

[ShortShiftEnvy]

Originally Posted by TrackRat

There's no point in excessive pressure. Dealers don't hire rocket scientists to change tires. 5 psi higher for sustained A-Bahn cruising is fine but for the U.S. there's little need for excessive pressure. It's also possible the dealer's tire gauge is off or the tire changer hung-over... Many dealers are notoriously inept.

Aren't the recommended pressure posted with the Run Flats in mind? So if you swap out to a non-RFT tire shouldn't you put excessive pressure? After all, the car's suspension and balance was fitted with RFTs in mind... no?

Edit: I have no reason to believe the OP isn't running RFT, I'm just introducing a different question.

[davefromfla]

Good question. I tried to find out when I went from RFT to Conti DW's. No reliable info I could find. Running 1 lb. over the stock RFT on all 4 tires. Seems to work well.

[SteDevote]

I'm running nitrogen, courtesy of my dealer...60 miles away. Pressures were high on the rears and correct for the fronts. If they'd been low, I would have had a 120 mile trip to have them adjusted.

[jetblackone]

The manual has different pressures for different tires and speeds. Looks like the dealer gave me the sport suspension tire settings even though I've got the base suspension...

[VMRWheels]

Originally Posted by jetblackone

Charles - what is your rationale for your tire settings ? And are they for a 128 or 135 ?

By the way, I'm aware of the 100mph plus specification, but use the lower (softer) spec for the improved ride quality. Also, I figure a softer tire will provide more rim protection...

I have found that iv experienced the best steering response and rear end rotation with these pressures. Of course, this will all depend on the weather and road conditions you will personally be experiencing. I recommend playing around with it to see what you and your car like.

-Charles@VMRWheels

[SteDevote]

When you think about it, the dealership can't win on this issue. If you take your car in for service, the tires are "warm". There's no way to properly adjust a warm tire. Couple that with inexpensive tire gages and it's always going to come out wrong.

N2 supposedly would eliminate the problem, but you're still left with inexpensive gages.

The system used to put nitrogen in my tires did/does purge each tire three times before the charging system fills the tire. Theoretically, a tire filled with nitrogen will not gain pressure when driven.

Adding air to a tire would theoretically cause the tires to respond unevenly to heat...so they say.

I remain skeptical.

OP, glad you solved your mystery!

[fboutlaw]

On my door there are pressures for if you're running under or over 100 mph. High speeds = higher pressures.

Your current pressures are way too high for daily driving. Go with the spec on the door for under 100mph (probably 36 psi F, 38 psi R).

[Walt White Coupe]

The only benefit to nitrogen is that the molecule is larger than an oxygen molecule. As a result the tire will hold pressure longer with nitrogen than one filled with air that is something like 22% oxygen. Consumer Reports did a study a while back and while I don't remember the exact result it was something like the nitrogen filled tire lost 1.5 lbs less pressure than an air filled tire over a year. The whole thing is a gimmick for gullible people.