New tyres.

[JockoT]

Today the ScanGauge recorded 50 mpg for my usual longish journey (for me) which normally achieves 60 mpg. It was so bad I checked my wheel centres for a dragging/binding brake, but they were all cold.

[JockoT]

Scotlands roads are just as bad, for the most part.

[JockoT]

Topped up the tank this morning and FE was 51.2 mpg. Not too bad considering I have four new all-weather tyres and I had my "Italian Tune-up" earlier in the tankful. I'll have to monitor my consumption over the next few tanks of fuel and see how it settles. The winter weather won't help.

[luv2spd]

The long term test 2020 Honda Civic Type-R that Car and Driver tested ate up its front tires in 8,900 miles; when they rotated them it lasted 15,000 miles.

I usually burn through a set of rear tires in 15,000 miles, but I buy the stickiest tire there is at a reasonable price. My wheels are staggered, so no chance of rotating them and I have a -1.5 camber angle in the back too. Installing a wider tire helped reduce the tire wear significantly, I would say about 20%.

The Pontiac Grand Prix GXP and the latest Audi RS3 had wider tires front than rear to help with the front wheel grip, maybe the Type-R should have the same to cope with tire wear.

These were my front and rear tires after 15,000 miles. You can see the inside of the rear tire worn out due to the camber angle in the back. Firestone Firehawk Indy 500.

[gregsfc]

Originally Posted by JockoT

Topped up the tank this morning and FE was 51.2 mpg. Not too bad considering I have four new all-weather tyres and I had my "Italian Tune-up" earlier in the tankful. I'll have to monitor my consumption over the next few tanks of fuel and see how it settles. The winter weather won't help.

Something I do when getting new tires mounted is to check and see if they have changed my trip meter/odometer error. I once had a VW Jetta TDI. Replaced tires. Thought that the new tires had allowed for a 2-3 mpg increase per tank on average for months. Only to learn later than the new tires created a 9.5% optimistic trip meter error vs a 4% optimistic error on the first set. I also had this happen on a motorcycle but to a lesser degree, but still, there was not a "real" change in mpg of any kind of significance. I know your post is with respect to grip, but I thought I'd share my experience, since I've noticed it twice in my driving history.

[JockoT]

I find my car is a bit sluggish since I fitted the new tyres and someone suggested that the effective diameter will have increased and may have effectively made my gearing a little bit higher. With a 1246 cc (76 cubes ! ) engine, it doesn't take much.

[Draigflag]

Kinda off topic, but as certain cars have different size wheel options, would a larger diameter wheel, let's say 19" instead of 18", offer fractionally slower performance but fractionally higher mpg? That's what I read once, you'd be splitting hairs trying to tell the difference no doubt...

[trollbait]

If the tire diameter is the same, the larger wheel will hurt fuel economy.
If the tire is bigger, it can help. The helping will be more obvious if the wheel size isn't changed.

[JockoT]

The wheel size hasn't changed, but the tyre is probably a bit bigger with the new enhanced tread. Higher gearing should help fuel efficiency but could make the car feel a bit sluggish and, depending on how it is driven, may reduce fuel efficiency.
I think my reduced mpg is probably due to the tyres being new (recognised in the motor industry as affecting mpg) and the deterioration in the weather with wet roads and cold tarmac. The tyres I have fitted are designed to move more water and moving that water requires energy which has to come from the petrol consumed.

[trollbait]

If the tire size on the side wall is the same, the difference between new, worn, and different models' sizes on final gearing isn't going to be something most people will notice in terms of fuel economy and acceleration. Fuel economy generally gets better as tires wear.

New tires have a higher rolling resistance. I've heard it is because of an interaction between the rubber and mold release.

Different treads can take more energy to move. As could the tire being heavier than the previous. Do the new tires have a higher max pressure? If so they might need the a higher pressure than your past tires. Set to the same pressure as the last ones might mean more sidewall flex.