[Nikhilb2008]

Originally Posted by funda2max

It is almost 20 days since i took delivery and car had clocked 1200Kms. Moreover it was dirty inside out due to monsoon. I gave it for servicing at Kalyani motors in Bannerghatta road (near Honeywell).

Some observations :

1) Engine is smooth and little noisy when compared before servicing.
2) Clutch is tight and i am still feeling some pain in left leg's calf muscle.
3) Braking has improved a lot after tyre upgrade.
4) Ride quality has improved as well.

A Question?

After Tyre upgrade (185/70 R14 Michelin XM1+) FE has dropped considerably. Is it normal?

No. It should be a marginal drop. Not a considerable drop. Could you share your FE figures before and after tyre change?

[funda2max]

Originally Posted by Nikhilb2008

No. It should be a marginal drop. Not a considerable drop. Could you share your FE figures before and after tyre change?

In the first fill (before change) - 18 kmpl
Second fill (After change) - 15 kmpl

Both scenarios have mixed of highway + city driving and top-to-top fueling method. (Diesel was filled at Shell, bangalore)

[Nikhilb2008]

Shouldnt be so much. Maybe the first run had much more highway driving?

[tj123]

Guys drop in FE is inevitable as fatter tyres have more rolling resistance (larger contact surface) and to over come it you naturally burn more fuel.

But a drop from 18 to 15kmpl is quite drastic. Ideally it should not be more than 5-10% of your existing mileage.

Jut recheck your FE figure once again ...may be it might be a calculation error. Else it looks like your service guys have tinkered with some settings ...kindly tell the service guys about this drop in FE and it it fixed.

[gkrishn]

Originally Posted by tj123

... (larger contact surface) ...

contact area should remain same, unless he used a humongous-ly large size.

[Nikhilb2008]

Originally Posted by gkrishn

contact area should remain same, unless he used a humongous-ly large size.

When you upsize your tyres from 165/80 R14 to 185/70 R14, your contact area WILL increase. 100%. No question about that.

There will be a drop in FE, but not so drastic.

[gkrishn]

Originally Posted by Nikhilb2008

When you upsize your tyres from 165/80 R14 to 185/70 R14, your contact area WILL increase. 100%. No question about that.

The length and width will change. But the overall area will remain same. Contact area is a function mass, not tyre size.

[funda2max]

Originally Posted by gkrishn

The length and width will change. But the overall area will remain same. Contact area is a function mass, not tyre size.

It is much wider tyre than the original 165/80, I think contact area also increased in all four wheels. I am not a tyre expert, pardon me for my innocence.

[nurni76]

Originally Posted by funda2max

It is much wider tyre than the original 165/80, I think contact area also increased in all four wheels. I am not a tyre expert, pardon me for my innocence.

Wider tyres are used to enhance grip. This means more contact area and hence more friction thereby reducing FE. But 16% reduction in FE is a little high. I guess drop should be less than 10%. Pls do a recheck of the FE with another FT to FT measurement and reconfirm.

[balajird]

Also, since this change is after the first service, it is also better to check with A.S.S. as to what tuning changes they have done.

[funda2max]

Originally Posted by balajird

Also, since this change is after the first service, it is also better to check with A.S.S. as to what tuning changes they have done.

Actually, the change was half way at 600KMs. Before giving it to service, i filled the tank and checked FE.

[balajird]

oops, sorry, i missed that. As everyone replied there is no way the tyre change is going to cause such a dip in FE, but, please give it a try again and see if by chance it is a human error of calculation, hope that the FE remains in the permissible deviation.

[Nikhilb2008]

Do calculate it again. Waaaay too many people have used XM1+ on Swifts to prove that the mileage cannot drop so much. Must be a calculation error.

Also, if I remember right, the first time oyu checked was on the highway trip from Mangalore to Bangalore.

PS: 175/;65 R14 is a totally wrong size for Ritz. Your ride quality will go down considerably.

[soccer]

FE would most definitely drop. Upgrade from 165 to 185 is an increase of 20 mm more rubber on the tarmac X 4 tyres = 80mm. That much more friction which explains the better Road holding and therefore better stability.

Come on guys, you need to sacrifice a little for a better and safer drive. The manufactures are not fools to give you a 165mm tyres. Its obvious that mileage is the only attraction that would compel one to go for diesel.

Going for a Diesel VDI does not justify its cost, especially when vital features are missing just to make the car affordable. But then, thats my thinking and is open for further debate.

In the meanwhile relish your drive and,

God bless....

[funda2max]

Originally Posted by Nikhilb2008

Do calculate it again. Waaaay too many people have used XM1+ on Swifts to prove that the mileage cannot drop so much. Must be a calculation error.

Also, if I remember right, the first time oyu checked was on the highway trip from Mangalore to Bangalore.

PS: 175/;65 R14 is a totally wrong size for Ritz. Your ride quality will go down considerably.

Yes, that was only for 330KMs. Else, all drives in the first fill were inside city. In my second fill, i drove 50% in highways (NH7) and rest inside city. Let me check again in the third fill.