Fitted new tyres (General Grabbers UHP) and lost 2 mpg ?? !!

[wadhurstdaisy]

Just wondering if anyone has had similar experience to me.

I've had four new General Grabbers fitted to my XC90 to replace my worn out Nokian NRVs (23,000 miles). Cost was GBP123 per tyre fitted plus £50 (+vat) for 4-wheel laser alignment.

First inpressions are that they ride softer than the Nokians. I always run my tyres at Eco pressure yet I feel they have more wallow than the Nokians; not excessively so but I now don't feel my teeth being shaken out over every undulation in the road. Tyre pressures have been checked 'cold' with both hand-held and petrol station forcourt gauge.

Noise wise, they are slightly more noisy than my worn out Nokians though I guess that's to be expected.

My main issue is that according to the 'reliable' dashboard fuel consumption has immediately increased with MPG falling by approx 2mpg. Journeys made in the car have remained constant ie 21 mile each way commute on free flowing roads and driving style hasn't changed.

I'm guessing the drop in mpg is due to the tyre sidewall being softer hence the greater wallow already expressed above though both the Grabbers and the NRVs are / were 107 rated. The larger tyre tread blocks probably also play a part.

It's just I don't remember such an impact on mpg when I've changed tyres on any vehicle before.

My XC90 had its 3rd year service performed / MOT with no issues raised. Fuel used is Shell Optimax Diesel and total mileage now 41.5k.

Any shared experiences will be welcome.

Thanks, Dave.

[Jim314]

The OE tyres on my 2004 V70 petrol 2.4L 168 hp non-turbo with 5-spd auto were Michelin MXV4 Plus Energy 195/65-15. With those tires I used to get up to 41 mpgUK on highway trips. When they wore out I switched to Michelin Primacy because that was what the tyre shop had in stock. On the one highway trip since getting the new tires I only got 35mpgUK. The urban mpg was unchanged at about 25 mpgUK.

Of course, these results could be due to other factors than the tyres, but I suspect the tyres.

I just replaced the OE tyres on the rear (Michelin 4x4 Synchrone 235/65-17) on my wife's 2007 XC90 3.2L FWD. It was bought new in April 2007 and had 25.4 kmi when the tyres were replaced. I had not rotated the tyres until recently and had them switched front-to-back same sides, so those on the rear had been on the front for 22 kmi.

I went with the Michelin Energy, despite their high price. I had gone to the tyre store to get a leak fixed in one of the rear tyres (it was a screw in the middle of the tread) and the tire tech suggested I replace the two rear tyres since they had only about 3/32" (2.4 mm) of tread. Since it was my wife's car I didn't feel right squeezing every mm out of the tires like I would if it were mine.

I expect the other two OE tyres to last another 6 kmi and then I'll replace them with the Energy. I have kept records of mpg from the first tank, and then I'll see if the new tyres give higher highway mpg.

[wadhurstdaisy]

Spoke to Main Dealer service manager whilst test driving 'polestar' performance upgrade (see other thread) and he is convinced the cause of the problem is the aggressive tread pattern on the tyres when compared to either nokian nrvs or the oe continentals.

Whilst the tyres are def pure road tyres and not offroad tyres, the tread design is in the shape of 'v' rather than have tread blocks in straight lines as found on the nokians and contis hence his belief it is tread design causing my mpg increase.

[Jim314]

We just took a 1589 mi trip mostly highway in my wife's 2007 XC90 FWD 3.2L I-6.

The four fuel fillups came out as follows:

1. 407.7 mi / 19.9 galUS = 20.5 mpgUS

2. 254.4 mi / 10.509 galUS = 24.2 mpgUS

3. 395.4 mi / 17.961 galUS = 22.0 mpgUS

4. 523.2 mi / 18.57 galUS = 28.2 mpgUS = 33.9 mpgUK

Leg 4 was all highway, speed kept mostly to 65 mph, and the clunky Volvo crossbars had been removed from the longitudinal rails at fillup 3. The overall altitude change on this leg was 5000 ft down to 500 ft.

Overall 1589 mi / 66.9 galUS = 23.7 mpgUS = 28.5 mpgUK

Testing mpg as a function of speed using the computer, the XC90 got ~30 mpgUS at 60 mpg and ~20 mpgUS at 80 mph. The XC90 is much more sensitive to speed than my 2004 V70.

[chf]

Originally Posted by wadhurstdaisy

Spoke to Main Dealer service manager whilst test driving 'polestar' performance upgrade (see other thread) and he is convinced the cause of the problem is the aggressive tread pattern on the tyres when compared to either nokian nrvs or the oe continentals.

Whilst the tyres are def pure road tyres and not offroad tyres, the tread design is in the shape of 'v' rather than have tread blocks in straight lines as found on the nokians and contis hence his belief it is tread design causing my mpg increase.

It might be worthwhile trying to find stats about rolling resistance for the General Grabber vs other tyres. I personally didn't experience any noticable fuel increase when changing from Pirelli scorpio to General Grabber.

Also had a few sets of V pattern tyres (Goodear F1 and Uniroyal rainsport) on my alfa GT and haven't noticed poorer fuel economy.

What sort of tyre pressure are you running on ? It might be worthwhile increasing a bit compared to tread block tyres.