Tyre Widths: Front - 225 , Rear - 265 OK?

[dsdfan]

My tyres are currently 225/40 18 in front and 255/35 18 in the rear, which are the standard staggered stock sizes for the E90.

Can I increase the rear tyre width to 265 (or even 275) but keep the front width at 225? Or must the front width also be increased?

My rims are 18 x 8.5 in front and 18 x 9.5 in the rear.

Thanks for your advice.

 

[Herman]

Re: Tyre Widths: Front - 225 , Rear - 265 OK?

I'd recommend you to up the front tire width to 235 minimum...
My rear is the same as ur stock... But front is 235/40/18....

 

[Ahbengdriver]

Re: Tyre Widths: Front - 225 , Rear - 265 OK?

there is a reason why BMW maintains 3cm difference on all their cars.

 

[dsdfan]

Re: Tyre Widths: Front - 225 , Rear - 265 OK?

Thanks Herman. Could you advise about the advantages to having wider front tyres? I was under the impression that narrower front tyres will provide more responsive steering.

ABD, do you know the reason for the 3 cm difference for staggered?

Thanks

 

[Bernie66]

Re: Tyre Widths: Front - 225 , Rear - 265 OK?

I wanted to know the reasons too..

Thks in advance.

 

[TripleM]

Re: Tyre Widths: Front - 225 , Rear - 265 OK?

wider in the front reduces understeering
so if u widen the rear only, ur u/s gets worse and bmw cars hv inherent u/s to begin with from factory set ups.

from experience 235/265 or 245/265 are good set ups.

 

[dsdfan]

Re: Tyre Widths: Front - 225 , Rear - 265 OK?

Thanks TripleM for sharing that useful info.

wider in the front reduces understeering
so if u widen the rear only, ur u/s gets worse and bmw cars hv inherent u/s to begin with from factory set ups.

from experience 235/265 or 245/265 are good set ups.

 

[Bernie66]

Re: Tyre Widths: Front - 225 , Rear - 265 OK?

wider in the front reduces understeering
so if u widen the rear only, ur u/s gets worse and bmw cars hv inherent u/s to begin with from factory set ups.

from experience 235/265 or 245/265 are good set ups.

Thks for clarification but i have another question to ask, mine currently 18 incher and using 225/255 staggered. Can i used 235 front and maintain 255 back? Cos I do not really wanna increase the rear overall diameter too much as our rides are RWD(higer fc, slower pickup & speedo inaccuracy too much).

Thks..

 

[jinooi]

Re: Tyre Widths: Front - 225 , Rear - 265 OK?

increasing the width of the tyre is what you are talking about here. it doesn't affect the diameter at all - hence it will not affect your speedo reading.

with regards to the FC and pickup, 1cm wider will not make a huge difference. i'd be more concerned about the increase in price of tyre...

Thks for clarification but i have another question to ask, mine currently 18 incher and using 225/255 staggered. Can i used 235 front and maintain 255 back? Cos I do not really wanna increase the rear overall diameter too much as our rides are RWD(higer fc, slower pickup & speedo inaccuracy too much).

Thks..

 

[Bernie66]

Re: Tyre Widths: Front - 225 , Rear - 265 OK?

increasing the width of the tyre is what you are talking about here. it doesn't affect the diameter at all - hence it will not affect your speedo reading.

with regards to the FC and pickup, 1cm wider will not make a huge difference. i'd be more concerned about the increase in price of tyre...

Erm, in actual fact increasing the width of the tyre will indeed increase the entire diameter. It is becos the width of the tyre is 1 of the factor while calculating the sidewall actual height.

You can try this and look at the OD difference: Tire size calculator

I will think that having a wider thus thicker front tyre will reduce the gap of the tyre to the body making it look more swee. It shld also flush with the body better. However, I do not know the pros and cons in and handling characteristic.

Thks..

 

[jinooi]

Re: Tyre Widths: Front - 225 , Rear - 265 OK?

dude, i know what i'm talking about...

notice that when the width of the tyre increases, the height / aspect ratio decreases?

this is to make sure that your rolling circumference remains the same, and doesn't screw up your speedo reading.

and contrary to what you think, having a thicker front tyre will not make your car look any different, because the rolling circumference of the tyre will still be the same... unless you keep the aspect ratio, which will screw up a lot of things, e.g. the way your car handles...

Erm, in actual fact increasing the width of the tyre will indeed increase the entire diameter. It is becos the width of the tyre is 1 of the factor while calculating the sidewall actual height.

You can try this and look at the OD difference: Tire size calculator

I will think that having a wider thus thicker front tyre will reduce the gap of the tyre to the body making it look more swee. It shld also flush with the body better. However, I do not know the pros and cons in and handling characteristic.

Thks..

 

[Bernie66]

Re: Tyre Widths: Front - 225 , Rear - 265 OK?

Perhaps a misunderstanding.. hehe

To be clearer, can I know will there be a difference in rolling diameter/circumference for the 2 different setup?

225/40/18"
235/40/18"

Cos honestly, I seen too many tire calculator and writeups that they have different rolling diameter/circumference.

 

[Ahbengdriver]

Re: Tyre Widths: Front - 225 , Rear - 265 OK?

I want to add on the cuntfusion.

If BMW 335 comes with 225/255 tyres, and with 306bhp. Then I kay-kiang add a 3rd turbo and becomes 400 to 450bhp, and even more kay kiang increase to 235/265, is this a clever or stupid kay kiang idea. Steering feel affected?

 

[jinooi]

Re: Tyre Widths: Front - 225 , Rear - 265 OK?

yes, there will be a difference.

225 / 40 - sidewall height - 90

235 / 40 - sidewall height - 94

the difference will be around 4mm at the radius, or 8mm in diameter, so the rolling circumference will be marginally different.

from calculation, the rolling circumference will increase by about 2.5cm for every revolution of the wheel.

Perhaps a misunderstanding.. hehe

To be clearer, can I know will there be a difference in rolling diameter/circumference for the 2 different setup?

225/40/18"
235/40/18"

Cos honestly, I seen too many tire calculator and writeups that they have different rolling diameter/circumference.

 

[kenntona]

Re: Tyre Widths: Front - 225 , Rear - 265 OK?

Interesting views, but take a look at any tyres and see the following characteristics:

Example Michelin PS2

225/35R19 Weight 21 lbs Diameter 25.2 inches Rev/mile 824
235/35R19 Weight 22 lbs Diameter 25.5 inches Rev/mile 817
245/35R19 Weight 23 lbs Diameter 25.8 inches Rev/mile 807

Observations:

(1) The wider the tyre, the heavier it is - intuitively. You gain lateral grip in return, as per contact patch advocates. This is assuming all things are equal, including load factors, pressure.....

(2) Because of the aspect ratio constant at 35, the wider the tyre, the larger is the diameter.

(3) For every 10,000 kms, the 245 width rotates 106,250 revolutions less than the 225. That's about 130 miles - negligible?

 

[jinooi]

Re: Tyre Widths: Front - 225 , Rear - 265 OK?

which also means that 225 will wear out faster, all other things being equal?

(3) For every 10,000 kms, the 245 width rotates 106,250 revolutions less than the 225. That's about 130 miles - negligible?

 

[kenntona]

Re: Tyre Widths: Front - 225 , Rear - 265 OK?

which also means that 225 will wear out faster, all other things being equal?

I would supposed so, all things being equal, owing to the diameter.

 

[Ahbengdriver]

Re: Tyre Widths: Front - 225 , Rear - 265 OK?

CCB now I cuntfused further

 

[sunrise]

Re: Tyre Widths: Front - 225 , Rear - 265 OK?

235/40/18 is 1.3% more in rolling diameter compared to 225/40/18. The "40" is the aspect ratio and does not change,. Google "wheel calculator" and there are many on the internet, such as this Tire size calculator.

 

[Bernie66]

Re: Tyre Widths: Front - 225 , Rear - 265 OK?

yes, there will be a difference.

225 / 40 - sidewall height - 90

235 / 40 - sidewall height - 94

the difference will be around 4mm at the radius, or 8mm in diameter, so the rolling circumference will be marginally different.

from calculation, the rolling circumference will increase by about 2.5cm for every revolution of the wheel.

So bro jinooi,

Thats exactly wat i'm trying to put across cos u mentioned it doesn't affect the diameter at all which puzzled me.. As mentioned previously and asking the pros here 2nd time,

(Thks for clarification but i have another question to ask, mine currently 18 incher and using 225/255 staggered. Can i used 235 front and maintain 255 back? Cos I do not really wanna increase the rear overall diameter too much as our rides are RWD(higer fc, slower pickup & speedo inaccuracy too much).

Thks..)

Thks..