Bigger wheels / MPG Drop ?

polod

Hi would any one know if a car came with 15 inch alloys as stanard and you 'upgraded' to 17 inch (genuine) alloys which have a tyre 40mm wider than the orginal 15 inch alloys,

1) Is there any benefit in doing this ?

2) If the car did an average 45 MPG with the stanard 15 inch wheels, How much would it roughly drop by with the bigger wheels ?

cheers for any info

(car has a 1.9 tdi engine)

101sean

No benefit here unless you enjoy a harsher ride, less rubber between you and the potholes :rolleyes:

Wider tyre could mean higher rolling resistance and less mpg.

polod

101sean wrote: »

No benefit here unless you enjoy a harsher ride, less rubber between you and the potholes :rolleyes:

Wider tyre could mean higher rolling resistance and less mpg.

What does higher rolling resistance mean ?

challengemaster

More tyre surface touching the ground throughout one revolution, more friction -> more resistance, meaning more fuel used to overcome that resistance in moving the car

LookBehindYou

http://www.miata.net/garage/tirecalc.html

biko

There's been many discussions about this but no conclusive proof I've seen to mean that bigger wheels would mean less Mpg.
Ease off the accelerator a bit, that's where you save. Also google hypermiling.

Chuck_Norris

polod wrote: »

Hi would any one know if a car came with 15 inch alloys as stanard and you 'upgraded' to 17 inch (genuine) alloys which have a tyre 40mm wider than the orginal 15 inch alloys,

1) Is there any benefit in doing this ?

2) If the car did an average 45 MPG with the stanard 15 inch wheels, How much would it roughly drop by with the bigger wheels ?

cheers for any info

(car has a 1.9 tdi engine)

I've done exactly that recently enough, and haven't noticed a drop off. Well, nothing major anyway. Maybe down to 43/ 44 mpg now.

Same engine, same jump in wheel size.

Nissan doctor

Its the width of the tyres that would effect the mpg much more then the size of the wheel but on normal road cars, the difference would be minimal and could easily be cancelled out by differences in tyres pressure etc. Unless you where going from something like 13inch wheels to 20 inch or something

Large diameter, narrow wheels/tyres would actually be best for ultimate mpg. Being narrow they wouldn't take as much power/torque to get moving and the large diameter equals more rotational momentum stored so less power needed to maintain speed.

vectra

Nothing really to be worried about.
One thing interests me.
What tyres?
I assume it ia a VAG car.
If I am correct are you running 195/65/15 ?
If so
40mm wider is an incorrect size to go for.
you need 225.45.17

I may be on the wrong car there though and wrong original size :pac:

polod

vectra wrote: »

Nothing really to be worried about.
One thing interests me.
What tyres?
I assume it ia a VAG car.
If I am correct are you running 195/65/15 ?
If so
40mm wider is an incorrect size to go for.
you need 225.45.17

I may be on the wrong car there though and wrong original size :pac:

Yep it a VAG alright and yes you are right it was on 195/65/15 and Its on 235/45R17 now ....Im in to minds wheather to put back on the 15s or not

vectra

polod wrote: »

Yep it a VAG alright and yes you are right it was on 195/65/15 and Its on 235/45R17 now ....Im in to minds wheather to put back on the 15s or not

235 is the wrong width.
It should be 225/45/17
OR
235/40/18
What wheels/tyres have you put on?

polod

vectra wrote: »

235 is the wrong width.
It should be 225/45/17
OR
235/40/18
What wheels/tyres have you put on?

Yeah i was thinking they were jeep wheel nearly they are off a 2004 audi a4 (s-line I think) I put them on my golf they look well on it ...I put them on it when i was young and immature ....

vectra

polod wrote: »

Yeah i was thinking they were jeep wheel nearly they are off a 2004 audi a4 (s-line I think) I put them on my golf they look well on it ...I put them on it when i was young and immature ....

Pics??:pac:

Nissan doctor

vectra wrote: »

235 is the wrong width.
It should be 225/45/17
OR
235/40/18
What wheels/tyres have you put on?

235/45/17 is the correct sized used on the a4 wheels.

polod

What do ye think is the narrowest tyre i could put on this wheel ?

dgt

MPG drop? Not really.

Upgraded from 195/50R15 to 205/40R17. The 17s have a bigger rolling radius. In the long run the mpg stayed much the same and in some cases went up (motorway driving at a constant speed for example)

Hope that helps

PaulKK

biko wrote: »

There's been many discussions about this but no conclusive proof I've seen to mean that bigger wheels would mean less Mpg.
Ease off the accelerator a bit, that's where you save. Also google hypermiling.

Think you might be wrong there biko. Larger wheels usually add unsprung weight and has an adverse effect on mpg. I know when i changed my alloys from genuine 16" to genuine 18" my mpg dropped from 48 to 46.

vectra

Nissan doctor wrote: »

235/45/17 is the correct sized used on the a4 wheels.

You are correct.
But it is an incorrect size to replace the original 195/65/15's

polod

vectra wrote: »

You are correct.
But it is an incorrect size to replace the original 195/65/15's

hows that ?

sean1141

is it a mk4 or mk5 golf

polod

its 2004 newer shape one though

vectra

polod wrote: »

hows that ?

Because as I have already said.
195/65/15 exact replacement are 225/45/17

TheUsual

Avoid low profile (thinner) tyres in Ireland.

You will feel EVERY damn pothole and manhole cover when you go over it.
Not to mention speed ramps.

Trust me, the fun side of it wore off quickly for me.
If you drive a lot you are looking at back problems in later years !!

challengemaster

vectra wrote: »

Because as I have already said.
195/65/15 exact replacement are 225/45/17

Thats a brilliantly detailed explanation as to how you arrived at that conclusion, just what we all wanted to know, thanks vectra!

:pac:

vectra

challengemaster wrote: »

Thats a brilliantly detailed explanation as to how you arrived at that conclusion, just what we all wanted to know, thanks vectra!

:pac:

I missed the part where anyone asked for a detailed explanation of howI arrived at the conclusion Answer
But here you go as I am well sure you already know about this

Tyre size Calculator

I also happened to discuss this with my local tyre fitter as I will be fitting a set of 17's to the Toledo which incidentally happen to be fitted with 195/65/5's as well

Nissan doctor

PaulKK wrote: »

Think you might be wrong there biko. Larger wheels usually add unsprung weight and has an adverse effect on mpg.

Unsprung weight on its own has an effect on handling, not mpg.

For mpg, its the weight of the wheel, not the size that can be an issue. 18" good quality lightweight wheels will offer less resistance then cheap heavy 16's.

polod

vectra wrote: »

I missed the part where anyone asked for a detailed explanation of howI arrived at the conclusion Answer
But here you go as I am well sure you already know about this

Tyre size Calculator

I also happened to discuss this with my local tyre fitter as I will be fitting a set of 17's to the Toledo which incidentally happen to be fitted with 195/65/5's as well

Right so what you are saying is they are not right fit for my car because my speedo reads wrong with the 235 tyres and it will read correctly with the 225 tyre .. ?.............tiz very confusing

Nissan doctor

polod wrote: »

Right so what you are saying is they are not right fit for my car because my speedo reads wrong with the 235 tyres and it will read correctly with the 225 tyre .. ?.............tiz very confusing

The difference in speedo reading between using a 225/45/17 and a 235/45/17 would be microscopic.

Car speedo's are not accurate anyway and always read faster then your actually going.

TheUsual

TheUsual wrote: »

Avoid low profile (thinner) tyres in Ireland.

You will feel EVERY damn pothole and manhole cover when you go over it.
Not to mention speed ramps.

Trust me, the fun side of it wore off quickly for me.
If you drive a lot you are looking at back problems in later years !!

I have 225 45 18s and don't find them that bad at all, bit crashy at times but that would be more the stiff suspension.

vectra

polod wrote: »

Right so what you are saying is they are not right fit for my car because my speedo reads wrong with the 235 tyres and it will read correctly with the 225 tyre .. ?.............tiz very confusing

No.
What I am saying is this,
225/45/17 are the recommended size to replace 195/65/15.

Not my suggestion.


Another issue you may find is that in the case of being involved in an accident if the insurance company found you had incorrect size tyres on your car then you could get a nasty shock if they said you are not covered because of this.

Matt Simis

vectra wrote: »

No.
What I am saying is this,
225/45/17 are the recommended size to replace 195/65/15.
Not my suggestion.


Another issue you may find is that in the case of being involved in an accident if the insurance company found you had incorrect size tyres on your car then you could get a nasty shock if they said you are not covered because of this.

Come on now, this is getting pedantic.
Difference between 235-45-17 and 195-65-15 = 8.8mm (1.39%)

While 225-45-17 would be perfect (0.03% difference) this is all pretty insignificant. The 235-45's will ride better on Irish roads and will handle potholes better, making them safer. Hard to see an Insurance issue with this. You also assume that the 195's are some sort of perfect baseline when VAG possibly offered larger diameter tyres that would match up to the 235's diameter.

For the OP, the MPG difference if any wouldnt justify the expense and effort of tyre swapping.

polod

Matt Simis wrote: »

Come on now, this is getting pedantic.
Difference between 235-45-17 and 195-65-15 = 8.8mm (1.39%)

While 225-45-17 would be perfect (0.03% difference) this is all pretty insignificant. The 235-45's will ride better on Irish roads and will handle potholes better, making them safer. Hard to see an Insurance issue with this. You also assume that the 195's are some sort of perfect baseline when VAG possibly offered larger diameter tyres that would match up to the 235's diameter.

For the OP, the MPG difference if any wouldnt justify the expense and effort of tyre swapping.

cheers I changed back to the 195/65/r15 today feels like a new car to car to drive, no whacks when i hit a bump in the road now and cheaper tyres too, I think it was the sensible thing to do

vectra

Matt Simis wrote: »

Come on now, this is getting pedantic.
Difference between 235-45-17 and 195-65-15 = 8.8mm (1.39%)

While 225-45-17 would be perfect (0.03% difference) this is all pretty insignificant. The 235-45's will ride better on Irish roads and will handle potholes better, making them safer. Hard to see an Insurance issue with this. You also assume that the 195's are some sort of perfect baseline when VAG possibly offered larger diameter tyres that would match up to the 235's diameter.

For the OP, the MPG difference if any wouldnt justify the expense and effort of tyre swapping.

I have no idea what you are on but can I have some please ? :pac:

First off,
How do you make out a tyre with 5mm higher sidewall will be safer??
Hit a pothole with any tyre and you can do more than tyre damage.

secondly,
Where did you see me make a statement that I think that 195's are some sort of perfect baseline? 195's are his standard tyre.. What baseline would you use?


Thirdly,
Of course VAG would offer a wider tyre (Which I assume you mean't instead of larger diameter) that would match to a larger diameter, But then again I would also assume that VAG would have this taken into account while designing the car and calculated suitable gearing to match.

Finally,
There was a lot of controversy in the UK last year regarding tyre sizes and insurance companies.
Do you think they would be more lenient over her in these recessionary times?

But hey,
Do I look as though I care?
It is no skin off my nose.
I only stated what the EXACT replacement tyre should be.
I have 225/45/17's on my car and that is how it is staying.
No issue whatsoever with potholes, And I have managed to hit a few.

Matt Simis

I think you are, yet again, flying off the wall and getting weirdly passionate about another hum-drum topic.

Taller sidewall = better impact protection. Wider tyre, better drive-over coverage of potholes. 235/45 have a taller sidewall and are a wider tyre than 225/45. I know nothing about your vague "controversy" in the UK. I do know that most VAG models are offered with like 10 different wheels with different tyre combinations. Its highly possible one of them has an overall diameter the same as the 235.. given we are talking about what amounts to largely insignificant millimeters of difference. This is the "baseline" Im referring to, once the Manufacturer offers a wheel tyre combination in a similar size, that ends your scaremongering insurance tangent.

PS: Stop writing in those freakish and unreadable stanzas!

vectra

Matt Simis wrote: »

I think you are, yet again, flying off the wall and getting weirdly passionate about another hum-drum topic.

Taller sidewall = better impact protection. Wider tyre, better drive-over coverage of potholes. 235/45 have a taller sidewall and are a wider tyre than 225/45. I know nothing about your vague "controversy" in the UK. I do know that most VAG models are offered with like 10 different wheels with different tyre combinations. Its highly possible one of them has an overall diameter the same as the 235.. given we are talking about what amounts to largely insignificant millimeters of difference. This is the "baseline" Im referring to, once the Manufacturer offers a wheel tyre combination in a similar size, that ends your scaremongering insurance tangent.

PS: Stop writing in those freakish and unreadable stanzas!

No,
I will leave that to you.
I was only pointing out that 225/45/17 is a recommended replacement tyre size for his originals,
But hey,
If you say 235 is correct then that's fine by me.
whatever floats your boat.

-Chris-

Alright lads, drop the handbags please.