Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[pedroMV6]

Had some Kumho KU97W tyres fitted at the back, and what a transformation!
Instant MPG has gone up from around 24 to around 34.

Size is 235/35ZR17.

I had a puncture on Friday, so been on the space saver spare, and today was the first chance I've had to get it in (Hi-Q Moss at Pickering, North Yorkshire on recommendation) for new shoes.
I have no idea what the old tyres were - cheapie things, I know that much - but it seems the money invested in these tyres is gonna pay for itself in only a few weeks!

The car seems a little more stable and sure-footed, but not by a great amount. It's the difference in economy I like!!!

[tunnie]

properly inflated then 

[pedroMV6]

Erm, properly inflated before - until the puncture

[tunnie]

can't have been infated or balanced correctly before, tyre difference cannot make fuel jump 10mpg, maybe 1 or 2, but not 10

[hotel21]

You 100% sure of the tyre size - 235 35 17 ?

If so, then the rolling circumference is 7.31% smaller - 147.64 mm - hence the difference in 'fuel economy'.  Standard size is 235/47/17.

Check the tyre size calculator towards the bottom of the second page...

http://www.carbibles.com/tire_bible_pg2.html

[TheBoy]

You 100% sure of the tyre size - 235 35 17 ?

If so, then the rolling circumference is 7.31% smaller - 147.64 mm - hence the difference in 'fuel economy'.  Standard size is 235/47/17.

Check the tyre size calculator towards the bottom of the second page...

http://www.carbibles.com/tire_bible_pg2.html

*cough* *cough*

[hotel21]

You 100% sure of the tyre size - 235 35 17 ?

If so, then the rolling circumference is 7.31% smaller - 147.64 mm - hence the difference in 'fuel economy'.  Standard size is 235/47/17.

Check the tyre size calculator towards the bottom of the second page...

http://www.carbibles.com/tire_bible_pg2.html

*cough* *cough*

Ok, ok.....  235/45/17 then....   

pedant........     

[pedroMV6]

can't have been infated or balanced correctly before, tyre difference cannot make fuel jump 10mpg, maybe 1 or 2, but not 10

Absolutely true.
Balanced and onflated properly - I do 50-odd miles a day commute on crappy B roads, so would be idiotic not to have them right.

[pedroMV6]

Apologies - tyre size 235/45/17 (typo, checked before posting this time!!!)

Old ones were 35 ratio.

[tunnie]

Apologies - tyre size 235/45/17 (typo, checked before posting this time!!!)

Old ones were 35 ratio.

Always wondered same on mine, offical size is 205 55 16, but i have 205 50 16, which are 20 quid a corner cheaper! 

It must cause some inaccuracy, but not noticable i don't think. MPG on the dash is about 1mpg under what i actually get.

[Del Boy]

Apologies - tyre size 235/45/17 (typo, checked before posting this time!!!)

Old ones were 35 ratio.

Always wondered same on mine, offical size is 205 55 16, but i have 205 50 16, which are 20 quid a corner cheaper! 

It must cause some inaccuracy, but not noticable i don't think. MPG on the dash is about 1mpg under what i actually get.

I thought they had 225/55/16's???

[tunnie]

Apologies - tyre size 235/45/17 (typo, checked before posting this time!!!)

Old ones were 35 ratio.

Always wondered same on mine, offical size is 205 55 16, but i have 205 50 16, which are 20 quid a corner cheaper! 

It must cause some inaccuracy, but not noticable i don't think. MPG on the dash is about 1mpg under what i actually get.

I thought they had 225/55/16's???

Yup your right, ta 

[platty]

Surely if you go from a 35 to a 45 this will give the illusion of an increased economy simply due to the larger circumference? You wont really be any more economical though will you?

[Rockhampton]

I had 205/50 x 16 on the front incorrectly fitted by the previous owner, with the correct 225/55 x 16 tyres on the front. As soon as I changed to the correct front tyres, lots of things got better - the MPG display was better, the ABS did not cut in all the time (it was constantly trying to correct for the speed differential between the axles), and for some reason, the autobox started changing down correctly (whereas before going down a hill was like being on a rollercoaster!). I worked out that the front wheels would have been going around an extra 37 ish times per mile, so it was bound to be having an effect on some controller somewhere!