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      09-24-2009, 02:58 AM   #1
ecksreturns
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Need help in deciding wheel size

Hi guys. I am planning on selling my VMR710's and going for the 'real deal' HRE 20" P40's. The car is lowered on Eibachs. I wanted to go for 305 rear and 275 front tires. I checked Doba_S's page and see that he is running 285 and 255 on the 20" P40's. I just wanted to ask the experts here that whether I will get any rubbing issues? I am interested in retaining the lowering springs but would take them off if any one has faced rubbing issues. I am also upgrading to the 385mm BBK, if that also adds to the equation. I apologize in advance if I did not search properly as I am in a bit of a hurry to find the answers.
Please help me. And thanks for any help/advise.
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      09-24-2009, 09:47 AM   #2
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Anyone?
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      09-24-2009, 08:26 PM   #3
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Well...you're off to a good start.

1) You decided on a wheel style (design)/brand/size *CHECK*
2) You know what size tires you want on the car *CHECK*
3) You incorporated the drop of your suspension into the equation. *CHECK*
4) You want to factor in the caliper clearance for a future BBK *CHECK*

You pretty much covered the primary mitigating factors that can come back to haunt you later on. Good work.

I don't often see this much attention to detail with BMW owners. I have put tire/wheel packages together for a number of local guys. (BMW's and several other brands)

The general public is not always aware of the pitfalls that can arise when you change one part on your car. That can cause you fitment issues if these factors are not accounted for in the pre-purchase phase.

Shopping for new wheels and tires can be a very happy experience...or your worst nightmare. (if you get it wrong)

In almost every case, the tire sizes will largely dictate which wheel width and offset you need to make it work without any issues.

I have always felt, that the wheel offset should NOT be chosen in advance. (pre-determined) That can and usually does get you into trouble.

When you are upgrading to a larger tire/wheel combo, you want to build in some 'flexibility' in case things change. You cannot select a firm offset number, and then 'hope' you can manipulate everything else around it. (to make it work)

I try to tell guys this is pure lunacy.

If you want the largest possible tires that can fit the car...then the offset by definition cannot the most aggressive fitment you can find. Those two things don't work very well...when you have a fixed fender (or wheel liner) sitting there like a brick wall.

The front tire size you chose is totally unrealistic. A 20" 275 tire on the front axle is way too big for our cars, and you'd be rubbing on wheel liners for sure.

I recommend the following P40 wheel widths and offsets for your M3:

255/30/20* - 20 x 9 , +19 offset

*This is the largest 20" tire you can put on the front wheels without getting yourself into trouble. (clearance wise)

305/25/20 - 20 x 10.5 , +24 offset
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      09-25-2009, 12:10 AM   #4
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Quote:
Originally Posted by Lemans_Blue_M View Post
Well...you're off to a good start.

1) You decided on a wheel style (design)/brand/size *CHECK*
2) You know what size tires you want on the car *CHECK*
3) You incorporated the drop of your suspension into the equation. *CHECK*
4) You want to factor in the caliper clearance for a future BBK *CHECK*

You pretty much covered the primary mitigating factors that can come back to haunt you later on. Good work.

I don't often see this much attention to detail with BMW owners. I have put tire/wheel packages together for a number of local guys. (BMW's and several other brands)

The general public is not always aware of the pitfalls that can arise when you change one part on your car. That can cause you fitment issues if these factors are not accounted for in the pre-purchase phase.

Shopping for new wheels and tires can be a very happy experience...or your worst nightmare. (if you get it wrong)

In almost every case, the tire sizes will largely dictate which wheel width and offset you need to make it work without any issues.

I have always felt, that the wheel offset should NOT be chosen in advance. (pre-determined) That can and usually does get you into trouble.

When you are upgrading to a larger tire/wheel combo, you want to build in some 'flexibility' in case things change. You cannot select a firm offset number, and then 'hope' you can manipulate everything else around it. (to make it work)

I try to tell guys this is pure lunacy.

If you want the largest possible tires that can fit the car...then the offset by definition cannot the most aggressive fitment you can find. Those two things don't work very well...when you have a fixed fender (or wheel liner) sitting there like a brick wall.

The front tire size you chose is totally unrealistic. A 20" 275 tire on the front axle is way too big for our cars, and you'd be rubbing on wheel liners for sure.

I recommend the following P40 wheel widths and offsets for your M3:

255/30/20* - 20 x 9 , +19 offset

*This is the largest 20" tire you can put on the front wheels without getting yourself into trouble. (clearance wise)

305/25/20 - 20 x 10.5 , +24 offset


THANK YOU SO MUCH!! I knew I would get some awesome and sound technical advice. I did indeed decide on 255/30/20 front and 305/30/20
rear for the HRE P40's riding on P Zero Nero's. I am also getting the BBK upgrade when the wheel change, so I will definitely post new pics as soon as I get the parts.

As always , LMB gives the best advice!
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      09-25-2009, 07:28 AM   #5
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Quote:
Originally Posted by ecksreturns View Post
THANK YOU SO MUCH!! I knew I would get some awesome and sound technical advice. I did indeed decide on 255/30/20 front and 305/30/20
rear for the HRE P40's riding on P Zero Nero's. I am also getting the BBK upgrade when the wheel change, so I will definitely post new pics as soon as I get the parts.

As always , LMB gives the best advice!
I hope that rear tire size was a typo.

The diameter of a 305/30/19 tire is way too big for our cars (27.2"), especially since you have lowering springs.

The stock rolling diameter for our cars is 26.3".

The 305/25/20 that I recommended, is the correct size for your upsized wheel application. (26.1") It's the closest size to the stock tire diameter. That will give your wheel/tire combo the necessary room to compress without causing a tire rub once the suspension geometry changes. (as you ride over bumps, dips and potholes) You'll rub like crazy if you don't do this...

You should cancel the order for 305/30/20's, and purchase a set of 305/25/20's, since they will not rub on the wheel liners or fender. You do not have enough clearance to accomodate the larger tire in this case.

BTW: Pirelli makes both sizes in the NERO's, so this is an easy fix. (no need to change tire brands)
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      09-25-2009, 07:35 AM   #6
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Thanks again LMB. I was suggested that combo by Ilia@IND. I sent him a link to this convo.
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      09-26-2009, 12:30 PM   #7
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LMB, I need your help again. I read every where that 305 is not a good tire size for the car and that it spoils the balance and will lead to rubbing. Can you recommend the ideal tire sizes for 20" rims ? 255 or 245 fronts? And 30 or 25? And for rear 285 or 295 with 30 diameter only , as 25 will worsen the ride quality on Indian roads.

Also, please note that the only reason I am changing the tire/rim combo is because I wish to install the 380mm all round brakes from Brembo. As recommended by Ilia/Nate , I need to change my 19" V710's as the brakes won't fit. Could you recommend 19 or 20" rims that go well with those brakes?
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      09-26-2009, 01:51 PM   #8
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may i ask why you are going to 20's?? you know it will hurt performance and the ride quality??

also why switch to 20" P40's when you already have the VMR's??? they will be heavier and cost alot alot more. only reason i can see if for a status thing as the VMR's look the same

if you care only about looks and what other people thing then go for it, just wanted to let you know the negatives first

good luck in whatever route you go
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      09-26-2009, 02:06 PM   #9
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Quote:
Originally Posted by H Bomb View Post
may i ask why you are going to 20's?? you know it will hurt performance and the ride quality??

also why switch to 20" P40's when you already have the VMR's??? they will be heavier and cost alot alot more. only reason i can see if for a status thing as the VMR's look the same

if you care only about looks and what other people thing then go for it, just wanted to let you know the negatives first

good luck in whatever route you go
Uh, he just said in the last post that the VMRs won't fit his planned BBK upgrade.
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      09-26-2009, 02:10 PM   #10
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Quote:
Originally Posted by H Bomb View Post
may i ask why you are going to 20's?? you know it will hurt performance and the ride quality??

also why switch to 20" P40's when you already have the VMR's??? they will be heavier and cost alot alot more. only reason i can see if for a status thing as the VMR's look the same

if you care only about looks and what other people thing then go for it, just wanted to let you know the negatives first

good luck in whatever route you go
Quote:
Originally Posted by 808MGuy View Post
Uh, he just said in the last post that the VMRs won't fit his planned BBK upgrade.

Yeah , thats the only reason, otherwise I won't have changed the combo. Also, I don't want the 365mm (which would fit the present setup) cuz I would be spending a good deal on importing the brakes to India, so might as well get the best out there.
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      09-26-2009, 02:37 PM   #11
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half asleep when i read that, my bad.

Quote:
Originally Posted by 808MGuy View Post
Uh, he just said in the last post that the VMRs won't fit his planned BBK upgrade.
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      09-26-2009, 02:39 PM   #12
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yeah didn't see that my bad. so you are gonna have a 385mm on the rear or just the front?? that will be badass. the stock has 380mm up front and 350mm rear right?? what will the new sizes be front and rear??

good luck


Quote:
Originally Posted by ecksreturns View Post
Yeah , thats the only reason, otherwise I won't have changed the combo. Also, I don't want the 365mm (which would fit the present setup) cuz I would be spending a good deal on importing the brakes to India, so might as well get the best out there.
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      09-26-2009, 02:41 PM   #13
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My car is slammed on KW V3's and I'm running Pirelli 305's in the back with HRE P40's and there is absolutely no rubbing at all.
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      09-26-2009, 02:41 PM   #14
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Quote:
Originally Posted by ecksreturns View Post
LMB, I need your help again. I read every where that 305 is not a good tire size for the car and that it spoils the balance and will lead to rubbing. Can you recommend the ideal tire sizes for 20" rims ? 255 or 245 fronts? And 30 or 25? And for rear 285 or 295 with 30 diameter only , as 25 will worsen the ride quality on Indian roads.

Also, please note that the only reason I am changing the tire/rim combo is because I wish to install the 380mm all round brakes from Brembo. As recommended by Ilia/Nate , I need to change my 19" V710's as the brakes won't fit. Could you recommend 19 or 20" rims that go well with those brakes?
The majority of the problems associated with 305's rubbing, are frankly due to poor offset choices made by many multi-piece wheel manufacturers. Yes, it's a huge tire. And it's not one I would ever choose myself. (it makes little sense to me personally)

But this was the size you wanted, so I offered you the best tire size available in a 305 rear.

Many times, the offset of the wheels are usually driven by the size of the lip tsome wheel brands are trying to achieve. That is why the wheel ends up slightly askew from it's ideal position in the wheel well. (but that's separate issue for another time)

When you put such a large tire on a car like the M3, their will certainly be a penalty in regards to performance. I see that you are now second guessing your initial decision to go that wide.

It's good that you have decided to re-examine this NOW...before you end up with a set of tires you didn't really want.

If you want something slightly smaller than the 305's, I would recommend a 295/25/20 tire as an alternative. This size will not rub anywhere if you get the wheels in the offsets I recommended earlier.

The 245/30/20's are a littler smaller as far as tire diameter is concerned, but the section width of that size does not offer you much rim protection against curbing.

Tire sizing is an art, and many times, there is going to be some type of compromise made. (somewhere) When you go away from the stock tires sizes, there are fitment 'gaps' that will force you to choose one path vs. another. (to bridge this gap)

BTW: You seem to think tire sidewall aspect ratios are an 'option' you have to improve the ride quality of the car. You cannot do this if you don't have the fender or inner wheel liner clearance to make that change. You cannot simply upsize the sidewall from a 30 series to a 35 series at will. That will increase the diameter of the tire, and this will lead to rubbing issues.

You cannot always have a perfect result, and it's important that everyone understands this basic truth.
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      09-26-2009, 02:43 PM   #15
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just read this, very good info in that post

Quote:
Originally Posted by Lemans_Blue_M View Post
Well...you're off to a good start.

1) You decided on a wheel style (design)/brand/size *CHECK*
2) You know what size tires you want on the car *CHECK*
3) You incorporated the drop of your suspension into the equation. *CHECK*
4) You want to factor in the caliper clearance for a future BBK *CHECK*

You pretty much covered the primary mitigating factors that can come back to haunt you later on. Good work.

I don't often see this much attention to detail with BMW owners. I have put tire/wheel packages together for a number of local guys. (BMW's and several other brands)

The general public is not always aware of the pitfalls that can arise when you change one part on your car. That can cause you fitment issues if these factors are not accounted for in the pre-purchase phase.

Shopping for new wheels and tires can be a very happy experience...or your worst nightmare. (if you get it wrong)

In almost every case, the tire sizes will largely dictate which wheel width and offset you need to make it work without any issues.

I have always felt, that the wheel offset should NOT be chosen in advance. (pre-determined) That can and usually does get you into trouble.

When you are upgrading to a larger tire/wheel combo, you want to build in some 'flexibility' in case things change. You cannot select a firm offset number, and then 'hope' you can manipulate everything else around it. (to make it work)

I try to tell guys this is pure lunacy.

If you want the largest possible tires that can fit the car...then the offset by definition cannot the most aggressive fitment you can find. Those two things don't work very well...when you have a fixed fender (or wheel liner) sitting there like a brick wall.

The front tire size you chose is totally unrealistic. A 20" 275 tire on the front axle is way too big for our cars, and you'd be rubbing on wheel liners for sure.

I recommend the following P40 wheel widths and offsets for your M3:

255/30/20* - 20 x 9 , +19 offset

*This is the largest 20" tire you can put on the front wheels without getting yourself into trouble. (clearance wise)

305/25/20 - 20 x 10.5 , +24 offset
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      09-26-2009, 03:23 PM   #16
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Quote:
Originally Posted by H Bomb View Post
yeah didn't see that my bad. so you are gonna have a 385mm on the rear or just the front?? that will be badass. the stock has 380mm up front and 350mm rear right?? what will the new sizes be front and rear??

good luck
I'll be going with 380mm(max available) for all four brakes.

Quote:
Originally Posted by Ca$hOnly View Post
My car is slammed on KW V3's and I'm running Pirelli 305's in the back with HRE P40's and there is absolutely no rubbing at all.
Now this confuses me even more. What offsets and tire dimensions are you riding on?

Quote:
Originally Posted by Lemans_Blue_M View Post
The majority of the problems associated with 305's rubbing, are frankly due to poor offset choices made by many multi-piece wheel manufacturers. Yes, it's a huge tire. And it's not one I would ever choose myself. (it makes little sense to me personally)

But this was the size you wanted, so I offered you the best tire size available in a 305 rear.

Many times, the offset of the wheels are usually driven by the size of the lip tsome wheel brands are trying to achieve. That is why the wheel ends up slightly askew from it's ideal position in the wheel well. (but that's separate issue for another time)

When you put such a large tire on a car like the M3, their will certainly be a penalty in regards to performance. I see that you are now second guessing your initial decision to go that wide.

It's good that you have decided to re-examine this NOW...before you end up with a set of tires you didn't really want.

If you want something slightly smaller than the 305's, I would recommend a 295/25/20 tire as an alternative. This size will not rub anywhere if you get the wheels in the offsets I recommended earlier.

The 245/30/20's are a littler smaller as far as tire diameter is concerned, but the section width of that size does not offer you much rim protection against curbing.

Tire sizing is an art, and many times, there is going to be some type of compromise made. (somewhere) When you go away from the stock tires sizes, there are fitment 'gaps' that will force you to choose one path vs. another. (to bridge this gap)

BTW: You seem to think tire sidewall aspect ratios are an 'option' you have to improve the ride quality of the car. You cannot do this if you don't have the fender or inner wheel liner clearance to make that change. You cannot simply upsize the sidewall from a 30 series to a 35 series at will. That will increase the diameter of the tire, and this will lead to rubbing issues.

You cannot always have a perfect result, and it's important that everyone understands this basic truth.

I did not mention upgrading from a 30 to 35 series at all. I meant that I wanted to hang on to the 30 series tire wall , if possible, so as to stick with the present ride quality.
So if I want to run a 295 width, I would have to run it with 25 wall to avoid rubbing, and not a 30?
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      09-26-2009, 03:37 PM   #17
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Quote:
Originally Posted by ecksreturns View Post
I'll be going with 380mm(max available) for all four brakes.



Now this confuses me even more. What offsets and tire dimensions are you riding on?




I did not mention upgrading from a 30 to 35 series at all. I meant that I wanted to hang on to the 30 series tire wall , if possible, so as to stick with the present ride quality.
So if I want to run a 295 width, I would have to run it with 25 wall to avoid rubbing, and not a 30?
I was just using that sidewall comparison as an example.

I understand that you want to increase your ride quality, but you cannot do this when the clearance is not available.

The 30 sidewall puts you over the limit and you will rub. (27.2" tall)

The 25 series sidewall (26.1") is the right size if you don't want to rub.

Like I said before there are fitment gaps, and sometimes you have to pick a tire size that has the least number of compromises.

There are limits to what you can and cannot do with aftermarket tire sizing.

That's just the way it works.
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      09-26-2009, 03:45 PM   #18
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Quote:
Originally Posted by Lemans_Blue_M View Post
I was just using that sidewall comparison as an example.

I understand that you want to increase your ride quality, but you cannot do this when the clearance is not available.

The 30 sidewall puts you over the limit and you will rub. (27.2" tall)

The 25 series sidewall (26.1") is the right size if you don't want to rub.

Like I said before there are fitment gaps, and sometimes you have to pick a tire size that has the least number of compromises.

There are limits to what you can and cannot do with aftermarket tire sizing.

That's just the way it works.
I understand now. So either I choose the 25 wall and then go with the fatter tires of 295 or 305. OR I go with 255/30 front and 285/30 back with 20" rims(as is the tried and tested case with many ppl correct?) and have a safe compromise of ride quality,over all balance of the car and no rubbing issues.

Have I got it right this time?
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      09-26-2009, 04:39 PM   #19
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I understand now. So either I choose the 25 wall and then go with the fatter tires of 295 or 305. OR I go with 255/30 front and 285/30 back with 20" rims(as is the tried and tested case with many ppl correct?) and have a safe compromise of ride quality,over all balance of the car and no rubbing issues.

Have I got it right this time?
Well, the last time I checked...

The Pirelli NERO's weren't available in 285/30/20. (which is on the tall side anyways) You can use the 305/25/20 I recommended in my first post (almost exactly the same rolling diameter as the stock tires), or go with the slightly smaller 295/25/20 if you want. Either size will work, and there will be no rubbing if you select the P40 wheel offsets I recommended.

Many 20" wheel owners select 245/30/20 in the front wheels if the car is lowered 1" or more. (via lowering springs or coilovers)

Due to industry accepted manufacturing tolerances, there is a slight variation in the fender and inner wheel liner clearances on our cars. (all cars actually) That can cause some light rubbing on full steering lock with the front wheels in some cases. The 255/30/20 will work in most cases, and is a better tire fitment overall for a 20x9 front wheel.

It's your call.
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      09-27-2009, 01:24 AM   #20
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Okay , I saw this thread (http://www.m3post.com/forums/showthread.php?t=279354). Can you recommend the offsets/dimensions for running 20" BBS CH-R's on 305 rear and 255 front?

EDIT - Also checked Tire rack. They recommend offset of 24 for all four wheels and recommend 245/30 fronts and 265/30 rear. I assume these are the basic ones needed? Can we go to 255/30 front and 295 or 305 for the rear with a 25/30 wall without any clearance or rubbing, with any tire brand available? Once I have this clear, I can then go ahead with my decision.
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      09-27-2009, 08:54 AM   #21
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Quote:
Originally Posted by ecksreturns View Post
Okay , I saw this thread (http://www.m3post.com/forums/showthread.php?t=279354). Can you recommend the offsets/dimensions for running 20" BBS CH-R's on 305 rear and 255 front?

EDIT - Also checked Tire rack. They recommend offset of 24 for all four wheels and recommend 245/30 fronts and 265/30 rear. I assume these are the basic ones needed? Can we go to 255/30 front and 295 or 305 for the rear with a 25/30 wall without any clearance or rubbing, with any tire brand available? Once I have this clear, I can then go ahead with my decision.
The HRE P40's are available in custom offsets (that you can choose within a given range), while the BBS CH-R's are only available in one fixed offset of +24 front and rear. You don't have the option to change the offset of the wheel itself...but you could add very small 5mm spacers to adjust the offset of the front 20x9 CH-R wheels. That spacer will give you an effective offset of +19 in the front, which is exactly what I recommended in my first post.

It's important to note the CH-R's are flow-formed CAST wheels, while the HRE wheels are 4000 ton forged. So that's not a true apples-to-apples comparison. The CH-R's will also be a few pounds heavier than the P40's (each), but the CH-R's are half the price of the P40's.

The reason the tire recommendations from tire rack are so small, is they are ultra conservative with wheel & tire fitments. (they always have been)

Here is a reality check...

A 265/30/20 rear tire on a 20 x 10.5 wheel is way too small. That narrow tire size would look ridiculous on a wheel that big. Someone screwed up big time on that fitment recommendation. And that's a huge problem in the world of wheel and tire fitments. Tire Rack is a huge company, and you can never be sure who they will dole out that responsibility to within the company. Clearly the person assigned to make the proper tire fitment recommendation in this case is a novice, and/or his recommendation was not double-checked by a supervisor with extensive fitment experience. They simply got that rear tire sizing recommendation wrong.

I have never seen any aftermarket 20x10.5 wheel with a 265/30/20 tire in my entire life. (that's because it's the wrong size )

And that covers hundreds of tire and wheel fitments for European, Japanese and American car and trucks. In the 15 years I have been doing this, I've seen quite a few poor tire & wheel fitment recommendations. (some are outright laughable)

The problem with a company like Tire Rack, is that people naturally assume since they sell this type of product everyday...they MUST know best right?

Wrong.

I abandoned the notion many years ago, that simply because a local shop or internet retailer sells something...that they actually know what they are talking about.

Hands on experience and attention to detail (over a long time period) will make you sharp at this type of thing. Knowing how to properly calculate the clearances you have, and choosing the proper wheel and tire sizes to match those clearances isn't as easy as it looks. There is no formal training available for this type of thing. So you either have to be self-taught, or you learn it from seasoned professional who knows their sh!t. I'm lucky to have a combination of both.

If you go for the BBS CH-R's here is a very solid (risk free) recommendation:

Front: 20 x 9 /w/ 5mm hubcentric spacer for effective an offset of +19mm, 245/30/20 tire.

Rear: 20x10.5 (no spacer required) +24 offset, 295/25/20 tire.

Your wheels or tires will not rub on anything with this configuaration. (guaranteed)

Let me know what you eventually decide to buy.
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      09-27-2009, 09:10 AM   #22
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LBM, would 285/35/19 RE-11's rub in the rear with 19x10 +20?
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