Wheel Size

Ectophile

EnPointe said:

wongataa said:

35har1old said:

TheProfessional said:

Thanks for the comments all

I currently have 20" and I don't think I'll do that ever again. They aren't totally terrible but with two small kids now I'd prefer the comfort of a smaller wheel like suggested with potholes, speed bumps etc. 

Also less bothered about the look now there's two kids car seats in the back and filled with muddy bikes and sand

Might just look down the range and just see about a less attractive trim but a wheel of choice e.g 19"

I'm not even sure the 1" difference would make that much of a noticeable improvement but theoretically should 

 H

Surely a smaller wheel dropping into a small pothole drops further.
As to speed bumps the size of wheel has very little to do with it as the description says it all "speed bump"
Larger wheel more ground clearance 

All cars in a range will have the same outside diameter of tyre.  The wheel size dictates the size of the tyre sidewall.  Smaller wheels means larger sidewalls (to keep the same OD of tyre) which means more comfort.  Smaller wheels are also lighter in general.

The same outside diameter of tyre is kept constant so the speedo reads correctly and the odometer reads correctly.  Manufacturers don't want to have different programming for speedos depending on wheel size.

 this is incorrect 

Have you ever thought of giving useful information, rather than simply saying that people are incorrect?

forgotmyname

wongataa said:

All cars in a range will have the same outside diameter of tyre.  The wheel size dictates the size of the tyre sidewall.  Smaller wheels means larger sidewalls (to keep the same OD of tyre) which means more comfort.  Smaller wheels are also lighter in general.

The same outside diameter of tyre is kept constant so the speedo reads correctly and the odometer reads correctly.  Manufacturers don't want to have different programming for speedos depending on wheel size.

The outside diameter is often very similar due to the bodywork, they dont want to make massive changes to the bodywork, although
arch kits maybe available for wider tyre combinations.

But not all cars have the same outer diameter, sometimes there is no choice but to have a different rolling radius.  I can use a cheap OBDII tool
to change the tyre sizes so that my speedo is accurate between 16" and 19" tyres.

This may apply to all brands but I know VW and Ford have the options available.

Arunmor

daveyjp said:

Arunmor said:

Ganga said:

Why would you want smaller wheels ?

Crikey, I'm more surprised someone asked that question.  20" wheels would be just horrible.

Not if they have 70 profile tyres and that's what matters, not diameter.

Long time since there were such tyres on modern cars.

Sea_Shell

Just as aside, it's a bit strange that wheels and tyres mix their measurements between metric and imperial like they do.

Inches for diameter, but mm for profile and width.   

Mildly_Miffed

Sea_Shell said:

Just as aside, it's a bit strange that wheels and tyres mix their measurements between metric and imperial like they do.

Inches for diameter, but mm for profile and width.   

Profile is % of tread width, not mm.

So 235/60 18 is 235mm tread width, 60% of 235mm = 141mm sidewall height, 18" rim diameter.

Metric rim diameters have been used in the past - Michelin's TRX back in the 80s.
https://www.michelin.co.uk/classic/tyres/michelin-trx#sizes

400ixl

Arunmor said:

daveyjp said:

Arunmor said:

Ganga said:

Why would you want smaller wheels ?

Crikey, I'm more surprised someone asked that question.  20" wheels would be just horrible.

Not if they have 70 profile tyres and that's what matters, not diameter.

Long time since there were such tyres on modern cars.

Not on SUV's it isn't. 70 is quite a common profile on 17's with SUV's.

facade

400ixl said:

Arunmor said:

daveyjp said:

Arunmor said:

Ganga said:

Why would you want smaller wheels ?

Crikey, I'm more surprised someone asked that question.  20" wheels would be just horrible.

Not if they have 70 profile tyres and that's what matters, not diameter.

Long time since there were such tyres on modern cars.

Not on SUV's it isn't. 70 is quite a common profile on 17's with SUV's.

I have 80 profile on mine.  You need them round here, there are pot holes so deep I have to drive round them.

facade

Sea_Shell said:

Just as aside, it's a bit strange that wheels and tyres mix their measurements between metric and imperial like they do.

Inches for diameter, but mm for profile and width.   

Tyres are a minefield of measurements.

Car tyres are measured by the size of the hole in the middle- ish (the rims are made in metric to the nearest equivalent inch size, there is a +/- 2mm tolerance on the rim diameter from nominal anyway and stated as inches- except when they are stated in mm, the only mainstream tyres like that used to be the Dunlop Denovo which had special rims and were metric sizes.

Except of course, when they aren't- "31s" are 31" overall diameter tyres with a 15" hole in the middle.....

Bicycle tyres are measured by the overall diameter of the inflated tyre in inches e.g. 29", 26", 20" - except when they are measured in metric e.g 700c (28"). The rims are all measured in metric to ISO standards- a 700c tyre has a 622mm hole in the middle.....

Sea_Shell

Mildly_Miffed said:

Sea_Shell said:

Just as aside, it's a bit strange that wheels and tyres mix their measurements between metric and imperial like they do.

Inches for diameter, but mm for profile and width.   

Profile is % of tread width, not mm.

So 235/60 18 is 235mm tread width, 60% of 235mm = 141mm sidewall height, 18" rim diameter.

Metric rim diameters have been used in the past - Michelin's TRX back in the 80s.
https://www.michelin.co.uk/classic/tyres/michelin-trx#sizes

I never knew that, about it being a percentage.  😲🤓

I knew a lower number meant less sidewall, but I'd never got a ruler out to check.

Every day's a school day ! 😉