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

[jinooi]

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

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..

dude what i was talking about was pointing you in the direction that the 1cm incremental doesn't make much of a difference. what makes the difference in the rolling circumference is the aspect ratio.

meaning that if you increase the width, the aspect ratio has to come down, or else your rolling circumference will also increase. This will be the one affecting your speedo, not the width of the tyre.

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..),..

yes you can use 235 for the front. but make sure that you retain the aspect ratio - 235/40. this will help you fill up the wheel arch - less gap.

my answer is directed at you not wanting to change the rears to 265 (and retain your 255 instead). my same reply is that 1cm incremental is not going to affect your FC, pickup, or speedo much even if you do decide to go for 265. cost will be the deciding factor as 265 tyres are going to be more expensive than 255.

hope i've made myself crystal clear

and btw, not sure whether the speedo reading is taken from the front or from the rear. from what i know, RWD doesn't necessarily mean that readings are taken from the rear.

 

[Bernie66]

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

dude what i was talking about was pointing you in the direction that the 1cm incremental doesn't make much of a difference. what makes the difference in the rolling circumference is the aspect ratio.

meaning that if you increase the width, the aspect ratio has to come down, or else your rolling circumference will also increase. This will be the one affecting your speedo, not the width of the tyre..

Thanks for the clarification To be frank(in other forum from my previous rides), many are ignorant to the width of the tyre which will affect the OD of the tyre while maintaining the aspect ratio.

Many tot that they can simply increase the width of the tyre cos wanted better traction or for whatever reason. They simply tot that so long they maintain the same aspect ratio, they are safe to do watever with the width and OD is never affected.

For example, i remember 1 dude actually mentioned he wanted to use 235/45/17" while the correct combi for that car model shld be 215/45/17". He even mentioned that the OD/Rolling circumference is the same thus not affecting speedo diff, pick-up etc. That increase in width will change the entire OD thus affecting many parameters of the car.

yes you can use 235 for the front. but make sure that you retain the aspect ratio - 235/40. this will help you fill up the wheel arch - less gap.

my answer is directed at you not wanting to change the rears to 265 (and retain your 255 instead). my same reply is that 1cm incremental is not going to affect your FC, pickup, or speedo much even if you do decide to go for 265. cost will be the deciding factor as 265 tyres are going to be more expensive than 255.

hope i've made myself crystal clear

and btw, not sure whether the speedo reading is taken from the front or from the rear. from what i know, RWD doesn't necessarily mean that readings are taken from the rear.

Apart from less gap from wheel arch, are there other pros cos I understand many bro here strongly recommend 235/40/18" instead of 225/40/18". I mean, it is apparent that the former will have a smaller wheel gap, less harsh due to thicker rubber height etc but I hope to learn and know more if the wider thus thicker tyre will add to other benefits and handling?

For most if not all japan make vehicle, the VSS (vehicle speed sensor) is in the gearbox. Mostly on the 3rd or 4th gear for a 6 speed gearbox. As for Bimmers, I believe the same apply here cos the method of sensing speed from the wheel or even drivetrain is only meant for 2 wheelers nowadays. Though I strongly believe Bimmer uses the same technology, perhap some1 can check and share..

 

[Shaun]

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

As for Bimmers, I believe the same apply here cos the method of sensing speed from the wheel or even drivetrain is only meant for 2 wheelers nowadays. Though I strongly believe Bimmer uses the same technology, perhap some1 can check and share..

Not true, because in any car with decent EBD, ABS, stability or traction control systems, there's good reason to read individual wheel speed directly.

===

Re: tires, the circumference and tire spring rate difference between the width options, is negligible considering the application. Priority should be handling, but reality is that on public roads you can only really use major changes, which tire widths within the mentioned ranges, are far from.

While it is generally true that a RWD that understeers cannot, without changes to other hardware, use more rear tire grip effectively in the entry and mid portion of a turn - it doesn't always apply at the exit. Really depends on turn type, engine and differential characteristics, and gearing. If you can use the extra rear tire at exit, then everywhere else as long as the driver is disciplined enough to stay at the original limits and not push deeper into ploughing understeer, then the front tires will live just as long as before. Any exit benefit has to be balanced with drag and fuel consumption though.

 

[dsdfan]

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

Hello Bernie66,

I'm no pro, but if you increase your front from 225/40 to 235/40 and keep your rear at 255/35, there will be an even bigger disparity between your front and rear wheel diameters.

As it stands, in a standard Front: 225/40 and Rear 255/35 setup, the rear tyre already looks noticeably smaller and thinner than the front. Increasing to 235/40 for the front will make the tyre thicker, and the rear 255/35 tyre will look thinner in comparison. Is this Ok with you?

I was considering doing the opposite to even up the diameters: Keep the front at 225/40 and increase the rear to 265/35. But as you mentioned, increasing the rear to 265 will affect Fuel consumption and acceleration.

Also, as TripleM advised, increasing rear tyre width will worsen the understeer issue inherent in BMW's. If so, I suppose increasing your fronts to 235 should decrease understeer, correct? Note that Herman, the 2nd poster on this thread, uses a 235 - 255 set up as you are considering.

(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..

 

[Bernie66]

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

Not true, because in any car with decent EBD, ABS, stability or traction control systems, there's good reason to read individual wheel speed directly.
.

But 1 of my previous japan ride (Honda Civic 2.0 to be exact) also comes with EBD, ABS & Traction Control. Its speedo reading is also taken from the gears. Perhaps japan make thus different analogy? I will try to do a search on bimmer as well if time permits..

Anyway its always good to share informations and this is what forums are for..

Hello Bernie66,

I'm no pro, but if you increase your front from 225/40 to 235/40 and keep your rear at 255/35, there will be an even bigger disparity between your front and rear wheel diameters.

As it stands, in a standard Front: 225/40 and Rear 255/35 setup, the rear tyre already looks noticeably smaller and thinner than the front. Increasing to 235/40 for the front will make the tyre thicker, and the rear 255/35 tyre will look thinner in comparison. Is this Ok with you?

I was considering doing the opposite to even up the diameters: Keep the front at 225/40 and increase the rear to 265/35. But as you mentioned, increasing the rear to 265 will affect Fuel consumption and acceleration.

Also, as TripleM advised, increasing rear tyre width will worsen the understeer issue inherent in BMW's. If so, I suppose increasing your fronts to 235 should decrease understeer, correct? Note that Herman, the 2nd poster on this thread, uses a 235 - 255 set up as you are considering.

Good point on the under/over steering effect on the width of the tyre. I do not know if the effect is substantial or minimal. Anyway, I will just continue to use my current setup of 225/40/18 and 255/35/18 cos they are rather new. Will consider and do more search on the feasibility of 235 for front when the time comes..:sneaky:

 

[jinooi]

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

erm guys, i think the understeer will only become a problem if you start pushing your car near the limit, e.g. on the track.

on normal street driving in singapore, you will not encounter a noticeable increase in understeer if you increase your rear tyre width by 1cm.

case in point - take a ruler and see how much 1 cm is. then imagine the difference of tyre contact patch with the road with this increase in 1cm...

how many of you actually take corners at 70+kmh, tyres squealing?

what i'm trying to say is that this is all academic - remember that you are not finetuning your car for the track, where every millimeter and gram counts. the more important consideration is the incremental cost you will face when you increase the width of your tyres - every cm costs money...

 

[Shaun]

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

But 1 of my previous japan ride (Honda Civic 2.0 to be exact) also comes with EBD, ABS & Traction Control. Its speedo reading is also taken from the gears. Perhaps japan make thus different analogy? I will try to do a search on bimmer as well if time permits..

Redundancy does not mean the CUs are not reading the wheel speeds. The wheel speed data is essential to the function of those systems.

Reading from a 5th location might save them the trouble of having to average 2 or 4 wheel speeds to give a fairly accurate road speed, and also save on a low reading (since averaged) if a wheel speed sensor were to fail.

 

[Bernie66]

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

erm guys, i think the understeer will only become a problem if you start pushing your car near the limit, e.g. on the track.

on normal street driving in singapore, you will not encounter a noticeable increase in understeer if you increase your rear tyre width by 1cm.

case in point - take a ruler and see how much 1 cm is. then imagine the difference of tyre contact patch with the road with this increase in 1cm...

how many of you actually take corners at 70+kmh, tyres squealing?

what i'm trying to say is that this is all academic - remember that you are not finetuning your car for the track, where every millimeter and gram counts. the more important consideration is the incremental cost you will face when you increase the width of your tyres - every cm costs money...

My sentiment's exact..

Feasibilty study is a must!!!

 

[SubZero]

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

As it stands, in a standard Front: 225/40 and Rear 255/35 setup, the rear tyre already looks noticeably smaller and thinner than the front. Increasing to 235/40 for the front will make the tyre thicker, and the rear 255/35 tyre will look thinner in comparison. Is this Ok with you?

Tire thickness for 225/40/18 and 255/35/18 are almost identical. 255x.40=90mm and 255x.35=89.25mm so difference in front and rear radius is only 0.75mm which is insignificant. If you want to go 235/40/18 (94mm) for the front then the rear should be 265/35/18 (92.75mm) for a better match as 255/35/18 is too far.

The other issue of mis-matched rolling diameters is DSC would kick in earlier.

 

[Bernie66]

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

Tire thickness for 225/40/18 and 255/35/18 are almost identical. 255x.40=90mm and 255x.35=89.25mm so difference in front and rear radius is only 0.75mm which is insignificant. If you want to go 235/40/18 (94mm) for the front then the rear should be 265/35/18 (92.75mm) for a better match as 255/35/18 is too far.

The other issue of mis-matched rolling diameters is DSC would kick in earlier.

Just curious, if the above mentioned of DSC will kick in earlier, will reseting of tyre in our OBD help? Just a fine thought, dun shoot me hor...

 

[dsdfan]

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

Thanks SubZero. Wonder if my 255's look thinner because they are stretched too thin by the wide 9.5" rims. Hope it's just an optical illusion.

Tire thickness for 225/40/18 and 255/35/18 are almost identical. 255x.40=90mm and 255x.35=89.25mm so difference in front and rear radius is only 0.75mm which is insignificant..

 

[SubZero]

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

Just curious, if the above mentioned of DSC will kick in earlier, will reseting of tyre in our OBD help? Just a fine thought, dun shoot me hor...

Not sure what reseting of tyre in OBD mean...

 

[SubZero]

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

Thanks SubZero. Wonder if my 255's look thinner because they are stretched too thin by the wide 9.5" rims. Hope it's just an optical illusion.

9.5" should be just right for 255's. In fact a 255mm tire is slightly wider than a 9.5" rim which is ok.

 

[steamy-stream]

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

Hi,
If I am running on 8J on my E90 can I do this...

225/40/18 Front
255/35/18 Back

Is 255 too big for 8J rims???

Also if the offset is 40 is that ok!

Thanks...

 

[dsdfan]

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

A 255 tyre requires at least 8.5J rims

Hi,
If I am running on 8J on my E90 can I do this...

225/40/18 Front
255/35/18 Back

Is 255 too big for 8J rims???

Also if the offset is 40 is that ok!

Thanks...