Profile size change......

[Turismo Todd]

Currently running with "225 50 17" but was wondering if I could drop the profile size down to "45" without affecting any of the electronics like the ABS sensors for example?

Thanks in advance...

[Trevor]

Hi Todd....welcome to the Forum

As long as the rolling diameter is the same all round the car then the ABS will be fine.

Beware of making the car feel every bump in the road and pothole damage with lower profiles

[Turismo Todd]

17 minutes ago, Trevor said:

Hi Todd....welcome to the Forum

As long as the rolling diameter is the same all round the car then the ABS will be fine.

Beware of making the car feel every bump in the road and pothole damage with lower profiles

Hi Trev, thanks for the reply. 

Appreciate that dropping the profile could potentially reduce ride comfort especially with our roads!!!!! however my previous two cars (none Audi's) had 45's or 35's and both were fine.

From a personal prospective I just don't like the look of the 50's and I'm hoping to improve the look with changing to the 45's, again just my personal choice.

Rolling diameter staying the same as is the width.

 

Todd..

[Trevor]

8 minutes ago, Turismo Todd said:

Appreciate that dropping the profile could potentially reduce ride comfort especially with our roads!!!!! however my previous two cars (none Audi's) had 45's or 35's and both were fine.

I recently increased the profile on my BMW Z3 as now I'm over 50 I notice the bumps a lot more, added to that I don't corner so fast so nothing lost there 🙂

[Magnet]

Hello Tod, 

‘Rolling diameter staying the same as is the width’ is incorrect. 

To maintain the rolling diameter ( the outside diameter of the wheel plus the tyre) and reduce the profile, then you must increase the width to ensure the outside diameter remains the same. 

The profile is a % of the tyre width, so changing from 50% to 45% obviously means the tyre width would need to increase from its current 225. 

Kind regards,

Gareth. 

[Turismo Todd]

53 minutes ago, Magnet said:

Hello Tod, 

‘Rolling diameter staying the same as is the width’ is incorrect. 

To maintain the rolling diameter ( the outside diameter of the wheel plus the tyre) and reduce the profile, then you must increase the width to ensure the outside diameter remains the same. 

The profile is a % of the tyre width, so changing from 50% to 45% obviously means the tyre width would need to increase from its current 225. 

Kind regards,

Gareth. 

Hi Gareth,

Excuse my ignorance but I thought rolling diameter was the size of the tyre IE 17in?

I'm looking to change from 225 50 17 to 225 45 17.  

[Magnet]

Hi Todd, 

No apologies needed. 

A 17 inch tyre means it fits on a 17 inch diameter wheel (in caps) - not that the tyre is 17 inch (outside) diameter. The all important consideration is the outside diameter - rolling diameter as Trevor refers to it - of wheel + tyre. This what ‘controls’ the correct indicated road speed etc. 

Now hopefully the logic follows that if you keep the tyre width the same yet reduce the profile (a % of the tyre width) then the outcome is you have reduced the outside dia (Trevor’s rolling diameter) of wheel + tyre, because the ‘height’ of the tyre wall has reduced. 

In effect, you will find that low profile tyres are fitted to larger diameter wheels, thereby maintaining a constant outside diameter. 

To do it properly you should consider 18 inch wheels if you want to move to 45 profile tyres - or as I say increase the width of the tyre - which is seldom practical. 

Question remains:- Why reduce the profile? 

Kind regards,

Gareth.