Wheel and tyre confusion

[Cobb]

Id play around with www.tirerack.com and look at wheel weights, tire weights an doutside diameters. Thats what I did.

[dmt257]

Well, I can tell you that the more reading I do, the more ambiguous it all seems.

Really, I'm at a loss as to what to do

[samwichse]

You pay multiple times for increased wheel mass. Overcoming good old inertia, but also overcoming rotational inertia. Add in the fact that the larger wheels will also move your mass closer to the outside edge if the wheel for the same mass and you're paying for it triple.

Now put in a wider contact patch for slightly more rolling resistance and more wind resistance and "ouch "goes the fuel economy.

You should see how bad the hit is on a first-gen insight going from 14" to 15" wheels (even with eco tires).

[Cobb]

What I did was shop tires and wheels after selecting my car. Maybe your country has an equivalent website? Knowing my tire size I looked it up and the next sizes up. My goal was to increase the outside diameter to make it taller so the gearing is increased. This way I go faster at lower rpms and get more mpg. Plan B was to get it to the point I could drive in sport mode and maintain mpg, but that didnt happen as I didnt go tall enough.

Tire sizes are this, tire width/tire height and rim diameter. I searched tire sizes for the following for taller tires:

175/85r15
175/80r15
175/75r15
175/70r15

No luck.

I then went wider and started over:

180/85r15
180/80r15
180/75r15
180/70r15

No luck and I repeated. I had to go to 205 to get a taller tire that route. I did however find if I went with 185/65r15 I could get a range of tires and they were about half an inch taller. Someone where recommended going smaller like a 155/85r15, but that was 20 mm narrower x4 and I didnt want to go that skinny.

So, using customer reviews I selected my tires and they were a few lbs lighter than what I had in oem size. I then went for the lightest rims I could afford, lucky 10 lbs each, but not the color I wanted.

Its a bit wide, so rolling fenders to make fit 100% as the new rims are 7 inches wide, stock 5.5 inches.

Luckly with my suv they had 3 sizes larger, so it was easy. That I went from 205/75r15 to 235/75r15 Went up a few inches in diameter, speed o is 5 mph off. Still can maintain mpg and can drive with traffic at 500 lower rpms. 500 rpms = 5 mph. So I cruse at 3000 vs 3500 for 60 mph.

[dmt257]

I've just watched a review for the BMW i8 petrol-electric sportscar.

They went for narrow tires for optimum fuel efficiency.

[Cobb]

dmt257, what are you trying to do? You want a better ride or better gripping? Better gripping is a tire issue, look for a better tire for the condition you have problems. You want it to handle better? Thats a larger wheel. I did both, larger wheel thats ten lbs lighter 1.5 inches wider and a slightly taller and wider tire. by 10mm wider half an inch taller.

185 65 r15

What tire psi are you using? Try going up to sidewall psi or down to door jam psi. Im running 5 less than sidewall psi and it rocks. 40 psi. Slap on some sport springs and it gets better for cornering. The Teins(SP?) are only an inch drop and go for 140 on amazon.

Other than adjusting your tire psi, try a rotation and or balance. I did that to my sidekick and it helped its feel. I also did this at 20k miles on the insight between tire replacements and it helps and yes, the tires needed rebalancing.

[dmt257]

Originally Posted by Cobb

dmt257, what are you trying to do? You want a better ride or better gripping? Better gripping is a tire issue, look for a better tire for the condition you have problems. You want it to handle better? Thats a larger wheel. I did both, larger wheel thats ten lbs lighter 1.5 inches wider and a slightly taller and wider tire. by 10mm wider half an inch taller.

185 65 r15

What tire psi are you using? Try going up to sidewall psi or down to door jam psi. Im running 5 less than sidewall psi and it rocks. 40 psi. Slap on some sport springs and it gets better for cornering. The Teins(SP?) are only an inch drop and go for 140 on amazon.

Other than adjusting your tire psi, try a rotation and or balance. I did that to my sidekick and it helped its feel. I also did this at 20k miles on the insight between tire replacements and it helps and yes, the tires needed rebalancing.

Just looking for economy gains

A 60 US mpg average is almost a given with my current set-up (had car 10 weeks and initial tanks were 15% below what I'm getting now so it'll creep up). I want 65!

I have my tyres at sidewall max. 51 psi and they're 185/55/16.