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...

[noelskii]

Damn, that's no bueno! I've been thinking of pulling the trigger on those rims too...

[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.

[Kostyan]

Originally Posted by 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

is this observation over a single tankful or over a period of time? There are also ton of other factors, but mpg should not drop by 4mpg. I'd have your truck checked out.

[bmrboi2]

What kind of tires are you running. Cheapos Like Nitto, Hankook, Kumho are shit for mileage tires.

[bawareca]

Originally Posted by bmrboi2

Cheapos Like Nitto, Hankook, Kumho are shit for mileage tires.

Yeah, they are all the same, right BTW, Hankook are the sole tire supplier for the DTM, the German racing series closest to F1. And Nitto is manufacturing one of the best, long lasting and affordable amateur racing/track day enthusiast tire.
Tire is either sticky, has a good or excellent grip, and is bad for gas mileage because of the roll resistance. Or it is "plastic" and doesnt have much grip and therefore doesnt hurt the comsumption much. Think Michelin Pilot Sport vs Michelin Energy.
My current Nittos compared to the previous Bridgestone RFT's are:
-less than 50% of the price
-at 7k miles quieter than the Bridgestones at 15k miles(when they were replaced due to wear)
-judging by the wear will last at least 3 times more then the Bridgestones
-may have slightly less dry grip, but it is very hard to determine only by feeling
-have definitely less wet grip
Now the tire installers dont hate me when i show up with new tires