Non-stagger by fitting a pair of Style 87 rear wheels in the front position

[powers1]

Originally Posted by J.Belknap

Hi guys. I've gotten a bunch of PM's regarding the use of 315's on rear wheels (Style 87) on all four corners. So I'll try to cover all of the questions that I've gotten.

OEM E53 Style 87 wheel/tire fitment: Although this has been covered/known to many, here it is for those who are new/didn't know.

5x120 P.C.D.
72.5 Center bore
14x1.5mm Wheel Bolt

OEM Front on left, OEM Rear on right.



Ok, the questions on using OEM rears all around.

Q. What offset is required to fit them?
A. They are a 10.5" width with +30 offset. This size is fixed. Compared to the factory 9.5" wheel with +45 offset, the 10.5" wheel will extend into the fender an additional 2mm, and extend out of the fender an additional 28mm. The BMW part # for this wheel is: 36116753517

Q. Did you go with the same wheel width front to rear?
A. Yes. All four wheels are 10.5" wide.

Q. Is there rubbing?
A. At full steering lock, the outer edge of the 315 (Michelin) tire will "clean" (not rub) the dirt off of the front part of the fender liners. Different tires have different overall widths. The Bridgestone Dueller Sports (non-runflat) that I have on now are slightly wider, but I have not noticed any additional rubbing wear on the front of the fender liners. How often are we at full lock anyhow? And for what duration and speed?

Q. Do I need a spacer up front?
A. No. These wheels fit over the biggest Brembo calipers that we can use. Refer to pictures below.

Q. Do I need fender arches up front?
A. Yes.

Q. Ok, what are the required front fender arch parts?
A. This depends on if you have OEM running boards. I do not have running boards.

Refer to this thread for further running board / fender arch part information

The parts I needed were:

BMW - 51717049867 (Quantity 1) Left front fender flare
BMW - 51717049868 (Quantity 1) Right front fender flare
BMW - 51111944537 (Quantity 20) Plastic rivets
MATCO - PR75 (Quantity 1) Plastic rivet tool

Q. Do I need spacers in the rear?
A. No, but you might want them. I almost said absolutely YES, but it's up to you. This will put more strain on the wheel bearings, but IMHO this needs to be done for compensation to your now 56mm wider front track. Otherwise, I believe (IMHO) that you will feel too much oversteer in the system. The wheel bearings should be checked for play at least twice a year IMHO. Common spacer applications for the rear are 25mm and 30mm. H&R sells hub-centric spacers that come with bolts.

H&R 25mm spacers/bolts - DRA 50757252
H&R 30mm spacers/bolts - DRA 60757252

Q. 25mm or 30mm?? OMG which one?!!??
A. I am using 25mm spacers. Refer to pictures below.

Q. Do I need extended bolts with those spacers?
A. No, they come with bolts to bolt the spacer to hub. You reuse your bolts on the spacer now.

Apply anti-seize between the rotor hat and spacer mating surface
Bolt the spacer to the hub
Torque to 105 ft-lbs
Bolt wheel to spacer
Torque to 105 ft-lbs
Go for a drive.
Take wheels off.
Check spacer bolt torque
Re-install wheels
Go for a drive
Check wheel bolt torque.

Q. Well what if I don't have rear fender arches? Do I need a rear spacer?
A. No, you don't. But, you do need fender arches up front, and for aesthetics/handling, you might want to purchase fender arches/spacers for the rear.

Q. Ok, what parts do I need for the rear fender arches?
A. Did not apply to me. The answer depends on if you have OEM running boards, or aero package. I do not have running boards. I do have the 4.6iS aero package. Refer again to this thread:

Refer again to this thread for further running board / fender arch part information

Q. So with the sandblasting issues that the X5M and X6M have on the lower sides of the body due to debris being launched up from the front tires, do I need front mudflaps?
A. I don't know. I bought front mudflaps, but have not installed them. After 10K miles of this setup, I have not noticed any sandblasting from front tire debris. If I do begin to notice it, I will install the front mudflaps and update the thread.

Refer to this thread for more information/pics of the front mudflaps.

Q. Can I rotate the 315/35/20 tires now?
A. Yes, Rearward-Cross or X-Pattern if tires are not directional. Front-to-Rear if the tires are directional.

Q. Will I feel the extra unsprung mass during acceleration and deceleration?
A. Yes.

Q. So that means less gas mileage?
A. Yes. Although to a negligible degree.

Q. Will the X5 tramline in the ruts of the road more now?
A. Yes.

Q. Will steering be heavier/require more effort?
A. Yes.

Q. Will the X5 hydroplane sooner in the wet?
A. Yes. Be careful. Get used to the new feedback.

Q. Is there less understeer?
A. Yes.

Q. Would you do it all over again?
A. ABSOLUTELY. The traction in the dry and turn-in feel is night and day better (IMHO). Note that my feedback is dependent on more than just slapping the wider front wheels on. The rear spacers balanced F/R track widths. Replacement of front LCA's and swaybar bushings was performed. Alignment was performed. Wheel bearing condition was checked. Don't look over normal maintenance guys, this should come first. If you have non-sport sway bars/struts/springs, your feedback may be different. I'm sure the engineers got it right, and that's why I'm not messing with the "system" further than:

- wider front wheels/tires.
- rear spacers to "maintain" the F/R track width "ratio".

Pictures:











Hope that helps,

- J

Great information.All in one super post,even the flares...Very comprehensive and no doubt will be very useful for anyone contemplating doing the same.
The only thing I dont understand is why you say the front now has a 56mm wider track ,when the fitting on the front of 315+10.5" wheel/tyre combination ,only sticks out 35mm in relation to the rear

[cfmistry]

Originally Posted by powers1

Great information.All in one super post,even the flares...Very comprehensive and no doubt will be very useful for anyone contemplating doing the same.
The only thing I dont understand is why you say the front now has a 56mm wider track ,when the fitting on the front of 315+10.5" wheel/tyre combination ,only sticks out 35mm in relation to the rear

Actually it sticks out 28mm in relation to the rear, but that is per side. 28mmx2 = 56mm which is the increase in overall track up front.

-Cyrus

[powers1]

Originally Posted by cfmistry

Actually it sticks out 28mm in relation to the rear, but that is per side. 28mmx2 = 56mm which is the increase in overall track up front.

-Cyrus

I said it sticks out 35mm because its 20mm for tyre difference and 15mm for offset,and actually ,thats whats it states on the same site that the OP used to get his first graphics!
Wheel / tire size calculator / comparer - RIMSnTIRES.com
Furthermore,the 315s at the front will be 5mm closer to the suspension and NOT 2mm as the OP states..!(Tyre is closer by 20mm but then the offset difference is 15mm out,difference 5mm!)

[J.Belknap]

Originally Posted by powers1

I said it sticks out 35mm because its 20mm for tyre difference and 15mm for offset,and actually ,thats whats it states on the same site that the OP used to get his first graphics!
Wheel / tire size calculator / comparer - RIMSnTIRES.com
Furthermore,the 315s at the front will be 5mm closer to the suspension and NOT 2mm as the OP states..!(Tyre is closer by 20mm but then the offset difference is 15mm out,difference 5mm!)

This is what I used for offset.



It can also be seen in the other diagram.

241mm/2 + 45mm = 9.5" wheel extends 165.5mm past hub surface into fender
267mm/2 + 30mm = 10.5" wheel extends 163.5mm past hub surface into fender

You are correct about the tires sitting further in. 315's are more tire to stuff on a 10.5" than getting 275's on a 9.5" wheel. Good catch. If speedo could be corrected, I'd think about using 305's. At the end of the day, I can safely say that these fit, and with plenty of clearance to the strut.

[powers1]

[QUOTE=J.Belknap;791753]This is what I used for offset.



QUOTE]

Hi Belknap,
Sorry mate,didnt mean to raise doubts on the great stuff you posted here for all to see and its very useful and very nice of you to share.
Everything is also correct .its just me thats "thick"...When I say that the wheel/tyre sticks out 35mm and in by 5mm,I am calculating with tyre ,not just the wheel,since the tyre is wider than the wheel,I thought this is whats relevant!Am I wrong .....

[J.Belknap]

Originally Posted by powers1

Great information.All in one super post,even the flares...Very comprehensive and no doubt will be very useful for anyone contemplating doing the same.
The only thing I dont understand is why you say the front now has a 56mm wider track ,when the fitting on the front of 315+10.5" wheel/tyre combination ,only sticks out 35mm in relation to the rear

powers1, you know what? Something in your post made me second guess myself on how I measured track width. I was measuring the change in outer edges. Gain of 28mm on each front outer edge with the wheel swap. Gain of 25mm on each rear outer edge adding the 25mm spacers. But, I learned today that's not how track width is measured. I should use the centerline of wheel/tire. Because, track width is a variable in the equation to calculate Total Lateral Load Transfer Distribution (TTLTD). Check it out:

http://www.eviltwinmotorsports.com/w...ter-2008.7.pdf

http://www.optimumg.com/OptimumGWebS...Tech_Tip_2.pdf

So, what we started with:

Tw Front - 1566mm
Tw Rear - 1596mm
Ratio TwF/TwR - 98.12%

By adding the wheels up front, front wheels' centerline moves 15mm out on each side. (+45 to +30 offset)

Tw Front - 1596mm
Tw Rear - 1596mm
Ratio TwF/TwR - 100.00%

By adding the rear 25mm spacers, rear wheels' centerline moves 25mm out on each side.

Tw Front - 1596mm
Tw Rear - 1646mm
Ratio TwF/TwR - 96.96%

So I ended with a NET GAIN in the rear track wrt the front track.

The truck is 51/49 weight distribution, but adding me and the tow bar kit, let's say 50/50 for simplicity's sake. So now that the TwF/TwR ratio is lower than when we began, it seems that (and I am oversimplifying this) I have slightly more understeer now. Increasing track width did not increase grip or lateral force, it decreased lateral weight transference. I think that change in force is what I mistook for oversteer.

Since the tires can perform more steady state cornering work when spread farther apart, they saturate at a higher threshold? Am I on the right train of thought here?

Then I have to think about wheelbase to Tw ratio, roll control, camber control, controlling the way the bodyshell moves after hitting the bump AND maximizing tire contact with the ground AND balancing understeer versus oversteer AND controlling toe with regards to suspension movement and braking or bump or impact loads applied to the hub and on and on and on....

This book is awesome, but it makes my head hurt.

Amazon.com: Race Car Vehicle Dynamics (R146) (9781560915263): William F. Milliken, Douglas L. Milliken: Books

If anyone finds an error here, please let me know. The last thing I want is to spread bad info.

- J