Last post on Feb 07, 2011 at 4:21 PM
You are in the BMW 3-Series
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BMW 3 Series
#474 of 1398 Re: Is Sports Package Really Necessary? [sanfrannewbie]
Mar 11, 2007 (7:13 am)
Short answer, if you liked the way the car felt without the SP, then you don't need it.
That said, I did the same thing for my first BMW. I drove a 1999 328i sans-SP, liked it, and ordered it. For the first 34 months of my 39 month lease, I loved the car and its handling. Then I swapped my car with another member here at Edmunds for a day and a half, and his car had the SP. I was instantly hooked. A month or two later I went out and ordered the 3ers replacement, a 2002 530i SP to be exact, and I couldn't wait for the least on the 328i to end. It was a good car, but the (relative) lack luster handling was just killing me once I knew what else could be had out there.
#475 of 1398 Tire Pressure Question
Mar 13, 2007 (5:11 pm)
I think I ask this question awhile ago on another forum but didn't get a really good answer; so here it is again.
My 335i has 225 45 R17 all around and the door panel has cold psi as: front 32 rear 38. Can anyone tell me why it's so high for the rear tires recommendations? At tire shops, they normally put in 32 psi all around. I notice they do the same at BMW when I put it in for service. I normally run front 32 rear 35 so wasn't sure why they recommended so high for the rear and the dealer service dept dont' do the recommended.
My x5 all around are 235 65 R17 and it's recommended psi cold is : front 32 rear 39 and I run it the same: 32 and rear 35's.
#476 of 1398 Re: Tire Pressure Question [tcn2k]
Mar 13, 2007 (6:37 pm)
The recommended tire pressures for my FWD Acura TL are 32 all around (same size, F&R). But my 911S carries recommendations of 34/42. I thought that was because the rears are larger/lower profile (295/30 vs. 235/35). However, I was told just today when I had it in for service that, under moderate to hard acceleration, the weight shift to the rear tires is significant. The TL is 60/40 front biased, so the rearward shift tends to equalize the weight balance. But the 911 is 38/62 rear biased and under hard acceleration, goes even further to the rear.
My guess - MBA not an engineer - is that in your 335i, with nearly 50/50 static weight balance, the higher rear tire pressure is to support the rearward weight shift under hard acceleration.
Any engineers care to set me straight?
#477 of 1398 Re: Tire Pressure Question [habitat1]
by kyfdx@Edmunds HOST
Mar 13, 2007 (6:39 pm)
I'm not even close to being an engineer...
But, I think you have it exactly... Also, under cornering loads, the rear tires seem to shoulder the lion's share of keeping the car on the road.. I think that is why the rear tires wear considerably faster than the fronts...
Our '03 325i and 05 330Cic were/are the same way..
#478 of 1398 Re: Tire Pressure Question [kyfdx]
Mar 13, 2007 (6:52 pm)
There are a few possible reasons that I can think of.
One is that higher tire pressure is used at the heavier end of the car - like Habitat's 911.
The other is that lower pressures are used on the tires that "work harder" so that when heated, all pressures equalize.
Tire pressure can also be increased to deliver better fuel economy by decreasing rolling resistance.
Tire pressure can be increased to "idiot-proof" the likelihood of underinflation, which can result in tire failure at speed.
Finally, tweaking tire pressure - front and rear - can change the handling dynamics of the vehicle. For example, increase rear pressure to minimize understeer.
Bottom line? I haven't a clue!
#479 of 1398 Re: Tire Pressure Question [fedlawman]
Mar 14, 2007 (3:25 am)
I really hate to throw this in but on my 330xi, the tire pressure recommendation is the same. Assuming the 40/60 rear bias of the xdrive, this just adds more questions.
Perhaps actualsize or shipo have a clue?
#480 of 1398 Re: Tire Pressure Question [fedlawman]
Mar 14, 2007 (9:16 am)
Based on the fact that the 330xi has the same pressure all around, i *think* the best explanation is that it helps to minimize understeer.
#481 of 1398 Re: Tire Pressure Question [dhanley]
by kyfdx@Edmunds HOST
Mar 14, 2007 (9:48 am)
I don't think he means the recommended pressure is the same all around... I think he means the opposite... That the rear is higher than the front, just the same as the other models...
Yes... I'm psychic..
Mar 14, 2007 (9:49 am)
.. I think suspension tuning (reducing understeer) is part of it..
#483 of 1398 Re: Also... [kyfdx]
Mar 14, 2007 (10:28 am)
Ah, yes, it could mean that too...
I'm still sticking with "reducing understeer".