Tire size expectations?

[SentraSE-R]

True, most 185-15s weigh 5-6 lbs less than equivalent 205-17s. 15 inch steel OEM wheels weigh as much or more than 17 inch aluminum wheels, though.

while moving you are slinging an additional 40lbs at each wheel or all 4 wheels moving have added 5% to the curb weight.........

you will be buying rotors and pads.......

Not really. Unsprung weight increases inertia and affects handling adversely. That says nothing about how it affects fuel economy, if at all.

[Bill in Houston]

Good find. Looking forward to results and impressions.

[mcrews]

Originally Posted by SentraSE-R

True, most 185-15s weigh 5-6 lbs less than equivalent 205-17s. 15 inch steel OEM wheels weigh as much or more than 17 inch aluminum wheels, though.



Not really. Unsprung weight increases inertia and affects handling adversely. That says nothing about how it affects fuel economy, if at all.

wait, Im confused.
So spending more money on other parts is ok???
Danm, why didnt you say so.........go with 22's.........

you claim that you are using the 'savings' from hypemiling to buy the tires and rims. So are you going to offset the savings from the additional weight to buy brake parts more offten??

You can do what you want, but don't try to claim that the harm doesn't exist. And that the harm has no effect.

On the Q45 site, a common complaint is that the rotors warp and that that is a weak link on the car.
with 235,000 miles, I have never had a warped rotor and I only run factory replacements( which are suppose to be crap). But the guys complaining always seem to be running more weight w/increased rims.

again, your car, go for it. but don't say that there is no evidence of a side effect.

[SentraSE-R]

I'll put ~35 miles on the new tires today. First impression driving 3 miles home yesterday was how soft and quiet the ride was compared to the rock-stiff 44 psi inflated (max sidewall) stock tires. I just checked cold inflation pressure on the new tires. They were at 36-42 psi - with 51 psi max sidewall rating.

There will be a substantial weight penalty. The stock wheel/tire combo weighs 35 lbs per my bathroom scale. The new tires alone weigh 26 lbs, and I obviously don't have 9 lb wheels.

Mark,

Why do you expect I'll have to buy brake parts more often? Why are you assuming I'm doing harm to my car? I'll bet I can easily get 100,000 miles out of a set of brake pads since I so rarely use my brakes to stop.

I've made no claims denying harm or side effects. I'm simply making no assumptions, good or bad, until I do some testing and build some experience driving with the new tires/wheels. You, OTOH, are assuming the worst.

[Bill in Houston]

re: brakes - a larger diameter tire has a longer lever arm to apply torque to the brakes, meaning the brakes have to squeeze harder to get the same amount of stopping force. but with the change you have implemented, it doesn't seem like that big of a difference.

[SentraSE-R]

I weighed my stocker wheel/tire combo, & came up with 35 lbs on my bathroom scale. I replaced the tires just in time, as the fronts were down to less than 2/32" tread depth in the center. I was wrong about tread wear being even after hypermiling 20,000 miles. They were definitely worn more in the center on the two front tires.

Today's drive impressions:

New tire ride @ 51 psi on 50 series tires is about as rough as 44 psi on 60 series tires

Stock (185/60-15) tires showed 60 mph on speedometer and UG when GPS speed was 57 mph.

New (205/50-17) tires initially showed 60 mph on speedometer & GPS when UG was showing 56.5 mph.

After 5.6% distance calibration of UG, new tires now show 60 mph on speedometer, GPS, and UG simultaneously.

Car's odometer readings are now underreporting mileage by 5.6%.

I pulled >60 mpg driving home after distance calibration.