Any reason why you shouldn't downsize the wheels on a car?

[Panayiotis]

rb5er said:

Vladimir said:

Small wheels, modest tyres (BTCC)

They look to be at least 18 or 19 inch wheels with about a 35 profile tyre, so pretty big wheels and pretty low profile.

The fiesta will have a higher profile as it is a rally car and they race on uneven surfaces.

I think you'' find that the size of the wheels on those cars are probably dictated by the need for large brake discs.

[Herman Toothrot]

When I bought my A6 it had 18" wheels which I assumed were standard, looked like regular Audi fair. However a pot hole later I discovered they were cheap replicas - on to the Internet discovered it should have had 16" Ronals (even with its 'big brakes' the 2.7T had over lesser models)- eBay found a full set at a scrap yard, purchased fitted and wow what an improvement. Quieter, lighter feeling, more comfortable better mpg. Why anyone would want 18" is a mystery.

[rb5er]

Panayiotis said:

I think you'' find that the size of the wheels on those cars are probably dictated by the need for large brake discs.

Yes that is the main reason as well as tyres having less movement.

Either way those are pics of three racing cars with big wheels and low profile tyres so they are hardly like that just for looks.

[kambites]

I'm in the process of buying some smaller (much lighter) wheels for the wife's Octavia for the same reason - the 18 inch OEM wheels are awful things.

[kambites]

rb5er said:

Either way those are pics of three racing cars with big wheels and low profile tyres so they are hardly like that just for looks.

Surely the fact that racing cars have them for practical reasons is precisely the reason that everyone puts them on road cars - they want their road car to look like a racing car even if it makes the car a worse road car. Same reason 17 year-olds stick big plastic body-kits to their cars and cut chunks out of the springs.

[rb5er]

kambites said:

rb5er said:

Either way those are pics of three racing cars with big wheels and low profile tyres so they are hardly like that just for looks.

Surely the fact that racing cars have them for practical reasons is precisely the reason that everyone puts them on road cars - they want their road car to look like a racing car even if it makes the car a worse road car. Same reason 17 year-olds stick big plastic body-kits to their cars and cut chunks out of the springs.

Yes but there are aldo plenty of road cars that require a particular sized wheel for practical reasons too, its not confined to race cars.

[monthefish]

kambites said:

rb5er said:

Either way those are pics of three racing cars with big wheels and low profile tyres so they are hardly like that just for looks.

Surely the fact that racing cars have them for practical reasons is precisely the reason that everyone puts them on road cars - they want their road car to look like a racing car even if it makes the car a worse road car.

That doesn't make any sense.

Racing cars do it for practical reasons but when people do exactly the same thing it's for aethetics?

[Ari]

monthefish said:

That doesn't make any sense.

Racing cars do it for practical reasons but when people do exactly the same thing it's for aethetics?

Yes!

Race cars do it because they need the space for large brakes and because they race on smooth tracks and don't care about the noise.

Hugo upspecs his new SLK to 18 inch rims cos it looks good. He's never going near a track, he drives on normal bumpy roads, and 16's can and do fit over the brakes, and would make his car quieter and more comfortable.

Just aesthetics.

[Marf]

So long as they fit over the brakes, I'd go as small and light as I could, assuming there were suitable tyre choices available in the size you wish to downsize to.

[Ari]

Herman Toothrot said:

When I bought my A6 it had 18" wheels which I assumed were standard, looked like regular Audi fair. However a pot hole later I discovered they were cheap replicas - on to the Internet discovered it should have had 16" Ronals (even with its 'big brakes' the 2.7T had over lesser models)- eBay found a full set at a scrap yard, purchased fitted and wow what an improvement. Quieter, lighter feeling, more comfortable better mpg. Why anyone would want 18" is a mystery.

As I said earlier, I borrowed an A6 when mine was being serviced and it had 18's. Ruined what would have been a lovely quiet smooth cruiser.

The more I think about this the more I think that, unless the dealer can swap the wheels for 16's, the 18's currently on it will probably stop me buying the car. Will try it first though, and hope I'm wrong.

[900T-R]

monthefish said:

smaller wheels --> bigger tyre sidewalls --> less precise handling/more vague steering.

Bigger wheels -> higher unsprung weight -> wheels not following the road as well as they could -> less precise handling
Lower sidewalls -> less compliance -> easier upset by cambers/tramlining etc; less progressive breakaway.

Back in the 1990s when cars went porky, but still came with 13" wheels and 80-section balloon tyres, upsizing by one or two inches would indeed net you that bit of sharpness lost from the lighter-on-their-feet predecessors. Now that even the lowliest rep tends to come with 225/50/17s as standard, I'd always go for the lowest-spec wheel option.

[Ari]

15 inch rims on these if I recall correctly, yet Mr. Rep-Spec has to have 18's on his BMW 318i to handle all that poooowwwwaa! (Or possibly to impress his neighbours)

[kambites]

monthefish said:

That doesn't make any sense.

Racing cars do it for practical reasons but when people do exactly the same thing it's for aethetics?

Why doesn't that make sense?

Road cars and racing cars run in completely different environments and have very different aims. What's good for a racing car is very often not good for a road car but that doesn't stop people doing it to the road car just to make it look like a racing car.

[monthefish]

kambites said:

monthefish said:

That doesn't make any sense.

Racing cars do it for practical reasons but when people do exactly the same thing it's for aethetics?

Why doesn't that make sense?

If someone takes the same action, what information do you have that says they are doing it for a completely different reason?
How do you know the motives of every individual on the road?

[monthefish]

900T-R said:

monthefish said:

smaller wheels --> bigger tyre sidewalls --> less precise handling/more vague steering.

Bigger wheels -> higher unsprung weight -> wheels not following the road as well as they could -> less precise handling
Lower sidewalls -> less compliance -> easier upset by cambers/tramlining etc; less progressive breakaway.

or
Bigger wheels -> lower unsprung weight
(Bigger wheels aren't necesarily heavier)

People are making too many assumptions here, either that or their views are too blinkered.

The OP asked:

"Any reason why you shouldn't downsize the wheels on a car?"

I gave one.

[900T-R]

monthefish said:

How do you know the motives of every individual on the road?

What the roads are like, is pretty much a given. They're a bit different from tracks.

Although the Nordschleife is a bit of an in-betweener.

Ergo: I don't know the motives of every individual, but if they're doing it for anything else than looks, they're misguided.

[kambites]

monthefish said:

If someone takes the same action, what information do you have that says they are doing it for a completely different reason?
How do you know the motives of every individual on the road?

I don't, but I can speak for people I do know and draw a statistically fairly strong conclusion from that. The only people I know who have big wheels and low profile tyres are those who are worried about the wheels "filling the arches properly".

[monthefish]

900T-R said:

Ergo: I don't know the motives of every individual, but if they're doing it for anything else than looks, they're misguided.

Or perhaps prefer the more direct feel?

I hate driving cars with excessively large sidewalls - the wallowy feeling ruins the drive.

But we're going round in circles here.

[niva441]

monthefish said:

or
Bigger wheels -> lower unsprung weight
(Bigger wheels aren't necesarily heavier)

People are making too many assumptions here, either that or their views are too blinkered.

The OP asked:

"Any reason why you shouldn't downsize the wheels on a car?"

I gave one.

Most of the data I've seen shows bigger is heavier, the only exceptions have been smaller diameter changes, certainly not 19"+

[monthefish]

kambites said:

The only people I know who have big wheels and low profile tyres are those who are worried about the wheels "filling the arches properly".

Which, within reason, is a decent enough reason in itself (although I know you disagree).

As I said before, of course there's a limit but the whole wheelsize argument is made up of shades of grey.