have a standard Megane diesel with the original 13" steel wheels
fitted.

have some 14" alloys, will fitting these have any negative effect
on economy?

what if I went up to 15"?

cheers

In message , Paul
writes
have a standard Megane diesel with the original 13" steel wheels
fitted.

have some 14" alloys, will fitting these have any negative effect
on economy?

what if I went up to 15"?

cheers


If you lower the aspect ratio of the tyres then there will be minimal
change to the rolling radius. If you don't change the aspect ratio then
there will be negative effects of gearing and speedo reading.

More info he- http://www.carbibles.com/tyre_bible.html
--
Paul Giverin

My Photos:- www.pbase.com/vendee

Paul Giverin wrote in message
...
In message ,
Paul writes
have a standard Megane diesel with the original 13" steel
wheels
fitted.
have some 14" alloys, will fitting these have any negative
effect
on economy?

what if I went up to 15"?

If you lower the aspect ratio of the tyres then there will be
minimal change to the rolling radius. If you don't change the
aspect ratio then there will be negative effects of gearing and
speedo reading.

More info he- http://www.carbibles.com/tyre_bible.html

Cheers Paul, particularly for the link.

In article ,
Paul wrote:
have a standard Megane diesel with the original 13" steel wheels
fitted.

have some 14" alloys, will fitting these have any negative effect
on economy?

what if I went up to 15"?

If you fitted larger wheels and pro rata tyres you'd raise the gearing.
Generally this results in better economy. But difficult to check because
the odometer would now give an incorrect reading.

--
*Happiness is seeing your mother-in-law on a milk carton

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote in message
...
In article ,
Paul wrote:
have a standard Megane diesel with the original 13" steel
wheels
fitted.

have some 14" alloys, will fitting these have any negative
effect
on economy?

what if I went up to 15"?

If you fitted larger wheels and pro rata tyres you'd raise the
gearing.
Generally this results in better economy. But difficult to
check because
the odometer would now give an incorrect reading.

Thanks Dave, you set me thinking. The last time I changed some
wheels on a car, I went from 13" to 15" and it was the first time
since I had owned the car that the speedo reading tallied with my
satnav, previously the car was always showing about 4mph faster.

As my Megane speedo shows a similar difference, can I expect the
same result?

Thanks,

Paul wrote:
Dave Plowman (News) wrote in message
...
In article ,
Paul wrote:
have a standard Megane diesel with the original 13" steel
wheels
fitted.
have some 14" alloys, will fitting these have any negative
effect
on economy?
what if I went up to 15"?
If you fitted larger wheels and pro rata tyres you'd raise the
gearing.
Generally this results in better economy. But difficult to
check because
the odometer would now give an incorrect reading.

Thanks Dave, you set me thinking. The last time I changed some
wheels on a car, I went from 13" to 15" and it was the first time
since I had owned the car that the speedo reading tallied with my
satnav, previously the car was always showing about 4mph faster.

I've used my Tomtom in several cars and it never agrees with the MPH.
The car always reads 2-3 MPH faster. I'll bet the Tomtom is correct.

In article ,
Paul wrote:
Thanks Dave, you set me thinking. The last time I changed some
wheels on a car, I went from 13" to 15" and it was the first time
since I had owned the car that the speedo reading tallied with my
satnav, previously the car was always showing about 4mph faster.

As my Megane speedo shows a similar difference, can I expect the
same result?

Be easy enough to work out if you can find out the rolling radius of the
various wheel tyre combinations.

--
*White with a hint of M42*

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...
In article ,
Paul wrote:
Thanks Dave, you set me thinking. The last time I changed some
wheels on a car, I went from 13" to 15" and it was the first time
since I had owned the car that the speedo reading tallied with my
satnav, previously the car was always showing about 4mph faster.

As my Megane speedo shows a similar difference, can I expect the
same result?

Be easy enough to work out if you can find out the rolling radius of the
various wheel tyre combinations.

even if the speedo reads correctly after fitting different wheels the
mileometer won't read right.

On Fri, 29 Jan 2010 22:46:39 +0000, Mrcheerful wrote:

[...]

even if the speedo reads correctly after fitting different wheels the
mileometer won't read right.

It won't read the same, but surely it may be closer to reality?

Chris

--
Remove prejudice to reply.

"Chris Whelan" wrote in message
...
On Fri, 29 Jan 2010 22:46:39 +0000, Mrcheerful wrote:

[...]

even if the speedo reads correctly after fitting different wheels the
mileometer won't read right.

It won't read the same, but surely it may be closer to reality?


The mileometer is usually quite accurate because it is directly pulse or
cable driven, whereas the average analogue speedo has a flappy needle which
is safely adjusted to overread. so putting big wheels on will often make
the speedo closer but put the (previously accurate) mileometer out.