Bad Mileage 4.8i Sport Wheels. PSI Problem?

[macmac80210]

I just purchased a set of the 214 style 20" wheels for my 4.8i e70. Previously, I was averaging 15mpg in the city and 19mpg on the highway. I pressurized them to 37 rear, and 36 front, and am seeing a 5mpg reduction, so now average about 10mpg city and 14mpg highway.

Is pressure to blame for this huge reduction in mileage, or is it just the wheels? EPA spec with them is supposed to be 14/17, so I thought I would end up somewhere pretty close to there. I don't drive with a lead foot, and it's still pretty bad.

Can someone tell me what they usually inflate theirs to, and what your mileage with the 214 style sport rims usually averages?

Thanks a ton

[bawareca]

Judging what others get from their diesels, mine is loosing 2-3 mpg from the 214 wheels, so your results may be correct. I have mine inflated to 32F/34R when not towing.

[macmac80210]

Originally Posted by bawareca

Judging what others get from their diesels, mine is loosing 2-3 mpg from the 214 wheels, so your results may be correct. I have mine inflated to 32F/34R when not towing.

That's really interesting. How does the tire wear come out with those readings? I've read stories of people only getting 14k miles with their 214's and I'm also hoping to avoid that.

[bawareca]

Yeah, this is what i got from my rear Bridgestones with camber set at lowest possible and moderate towing. Now I have Nittos and after 7-8 k miles there is no visible wear at all.

[ard]

wow. cannot understand how tires/wheels can have such a massive impact on MPG. BMW fights for 0.1mpg for CAFE standards...2-3mpg seems impossible.

Tire wear is driven (virtually) ENTIRELY by alignment....anyone concerned with tire life that does not know their TOE numbers is lost...

[bawareca]

Originally Posted by ard

wow. cannot understand how tires/wheels can have such a massive impact on MPG. BMW fights for 0.1mpg for CAFE standards...2-3mpg seems impossible.

My results are not scientific, but I have seen people here report over 500 miles on a full tank. I was never able to get over 450 miles even with soft driving style. My mileage varies very little from city to hwy. Doing 80 on the hwy is where the roll resistance will have most impact so it makes sense.

Originally Posted by ard

Tire wear is driven (virtually) ENTIRELY by alignment....anyone concerned with tire life that does not know their TOE numbers is lost...

My rear Bridgestone RFT weared-out in a heartbeat with minimum camber settings possible(~1.2 degree) and 0 toe. Fronts were wearing on the outside first , which has nothing to do with the toe. You are generally correct, but with these monstrous sizes and run-flat tires the wear factors are different.

[youry]

Originally Posted by bawareca

My results are not scientific, but I have seen people here report over 500 miles on a full tank. I was never able to get over 450 miles even with soft driving style. My mileage varies very little from city to hwy. Doing 80 on the hwy is where the roll resistance will have most impact so it makes sense.

I get 500+ miles per tank(highway), 2012 X35i 56k, still running the original/factory Bridgestone RFT dueler tires (factory 18" wheels)

[macmac80210]

Originally Posted by youry

I get 500+ miles per tank(highway), 2012 X35i 56k, still running the original/factory Bridgestone RFT dueler tires (factory 18" wheels)

Tire size probably makes a huge difference, and you're also running a '12 3.5 and I'm running a '07 4.8.

I am now sitting right around 9.5 MPG after 2 tankfuls and a solid mixed-city commute. I have brand new Bridgestone tires, so I don't think that should be the issue. I have been trying to milk the mileage, but it's just not coming. I think the real issue is increased lb/ft of torque required at startup from 0mph because of the larger wheels. I was coming from a pair of 17" with a winter Bridgestone setup, and it's just frightening to see a 5+ MPG decrease with these things.

Any ideas on who to talk to about shitty mileage? Dealer or some tire place?

[macmac80210]

Originally Posted by ard

wow. cannot understand how tires/wheels can have such a massive impact on MPG. BMW fights for 0.1mpg for CAFE standards...2-3mpg seems impossible.

Tire wear is driven (virtually) ENTIRELY by alignment....anyone concerned with tire life that does not know their TOE numbers is lost...

I cannot understand it either. I think that I'll probably deflate them today, and see how my mileage is on a fresh tank. Right now, I'm running 5PSI over what some are suggesting, so that could be the issue, but I always was under the impression that higher was better for mileage. Maybe that's just old nonsense

[Padgett114]

We went from 19's to 20's with offset on our 2010 35D and didn't really see much of a decrease in MPG, still get great mileage.