Fitting 18x10.5+22 squared on E46 M3

[Nate047]

I have roll centre and geometry correction in front and rear (entire trailing arm is offset) putting everything close to factory angles at the lower height, with the exception of the rear lower arm pickup point which has been flipped to keep both rear arms more parallel than factory. It did allow me to run slightly less static camber and slightly less spring rate all around than without it due to the roll centre change and improved anti-squat. 3.8-4* front and 2.8* rear results in relatively even tire temps and tire wear, actually could use a touch more rear camber but I compromise slightly to aid in traction exiting slower corners.

Hey Beau, would you be willing to share some more info about your front roll center adjustment setup? I’ve been trying to look into this and it seems like there aren’t a lot of off the shelf options out there, aside from angle kits.

[Obioban]

I have roll centre and geometry correction in front and rear (entire trailing arm is offset) putting everything close to factory angles at the lower height, with the exception of the rear lower arm pickup point which has been flipped to keep both rear arms more parallel than factory. It did allow me to run slightly less static camber and slightly less spring rate all around than without it due to the roll centre change and improved anti-squat. 3.8-4* front and 2.8* rear results in relatively even tire temps and tire wear, actually could use a touch more rear camber but I compromise slightly to aid in traction exiting slower corners. I don't really know of any fast E36/E46 track cars that don't run at least 4* front camber, certainly the whole B1/B2 Bimmer Challenge field and the SCCA GT2 cars I do calibration on. We'd all love to run less if possible. You of course sacrifice some braking performance, but with the relatively low power level (and therefore speeds entering braking zones) of these cars NA, the benefits in avg cornering speed outweigh the loss in braking performance on most tracks here. On a higher HP car or a track with long straights and critical braking zones this would likely be different.

Don't think I've ever used alignment to "fit" a wheel/tire. For me the process is pick the tire you want to run, match the wheel to that tire, set the geometry and alignment based on testing and data, and do what you need to fenders etc to make that fit. Pretty simple.

Sure there are some compromises to scrub radius and to aero due to the leading edge of the tire, but these are both not trivial to resolve. I decided for me the benefits of the wider tire and its increased thermal mass outweigh the disadvantages. If someone comes out with a custom knuckle with better strut clearance to allow a higher offset wheel I'd probably do it. A friend of mine is fitting E9x-based front suspension to his E46 to allow an 11" higher offset wheel to fit the front but it's turning into a pretty crazy one-off project.

I think what you've listed above is a good description of what's required to make a wheel in the ET2X range "work". Do you think that's what the OP is planning, when he doesn't even have camber plates?

When "normal" people ask if something fits, they mean can they make it not rub. In the case of a 10.5 ET22 wheel, that means they're going to run a detrimental amount of camber to make it not rub.

Ignoring static camber, and the camber curve, that much scrub radius (from just the offsets) gives you bad limit steering behavior, ruined steering feel, bad braking stability, etc. Too much camber makes that braking stability (and rate) worse still.

If you're building a race car, fuck it, make the car feel terrible if it's faster. If you're build a track car or street car, feel, feedback, and predictability matter.

Run something ~ET35 (front) with a ride height that allows the spring perch to be above the tire and you can set camber by surface temps and not redo the entire front end geometry to make it work, AND have a car that's easier to drive/more predictable. And with that spring perch above tire ride height, you're almost certainly high enough that you're in the good camber curve, so you can get away with less static camber.

Unless you're going for real aero, high ride height and "soft" springs (~2x stiffer than stock) are the way to go IMO.

[BBRTuning]

Ultimately decided on going 18x10+25 / 265/35r18 sq. I really believe this to be the optimal setup for E46s that see track/canyon time. Past a 265 width tire I’ve found steering feel begins to drop off…many moons ago I ran 285/30 sq. Never again.

I think what you've listed above is a good description of what's required to make a wheel in the ET2X range "work". Do you think that's what the OP is planning, when he doesn't even have camber plates?

When "normal" people ask if something fits, they mean can they make it not rub. In the case of a 10.5 ET22 wheel, that means they're going to run a detrimental amount of camber to make it not rub.

Ignoring static camber, and the camber curve, that much scrub radius (from just the offsets) gives you bad limit steering behavior, ruined steering feel, bad braking stability, etc. Too much camber makes that braking stability (and rate) worse still.

If you're building a race car, fuck it, make the car feel terrible if it's faster. If you're build a track car or street car, feel, feedback, and predictability matter.

Run something ~ET35 (front) with a ride height that allows the spring perch to be above the tire and you can set camber by surface temps and not redo the entire front end geometry to make it work, AND have a car that's easier to drive/more predictable. And with that spring perch above tire ride height, you're almost certainly high enough that you're in the good camber curve, so you can get away with less static camber.

Unless you're going for real aero, high ride height and "soft" springs (~2x stiffer than stock) are the way to go IMO.

Yeah no real arguments from me there. I still recommend 18x10 + 25 with a 265/35 for most people as it just works and is easy. if you can run a higher offset like +30-35 and make it fit then even better. The 10.5" and 275 is substantially more work that may not be worth it depending on the use case. For me I wanted the taller sidewall of the 275 as the 4.10 rear is a bit too short for Buttonwillow, with the 275 I can just barely stay in 4th. It's that close. Also most of the 200TW we run you get one great hot lap on them, by the end of the 2nd flyer they're getting hot. The larger tire gives you a bit more longevity. I've run 275s on a 10" wheel, sure it works, but for me one of the things I hate more than anything on a car is the feeling of squirm in the tire sidewall and the delay you get on turn-in etc (like an NT01 especially). More noticeable on a heavier car. The 0.5" width makes a difference there for me.

Hey Beau, would you be willing to share some more info about your front roll center adjustment setup? I’ve been trying to look into this and it seems like there aren’t a lot of off the shelf options out there, aside from angle kits.

Yeah I was stuck in the same dilemma forever, couldn't find a solution I liked overall but I ended up with the MRT roll centre/bump steer kit, it keeps the steering ratio factory. I have an SLR race angle kit on my 330i and frankly it's been a mess and plan on removing it soon. Zero issues with the MRT so far and seems really well made, although if anything I'd guess the weak point is the lower arm stud that goes into the knuckle with the increased load it will see due to being extended but this is the nature of the beast. Theirs is quite overbuilt though. A couple of the race shops I work with do something similar but actually weld the stud permanently to the knuckle, theoretically for increased strength. I plan on cycling mine out maybe every other year for peace of mind, I do the same with wheel studs for the same reason anyway.

The rear is essentially a replica of a WTCC setup and is from MK Trackparts in Germany. Bit more work to get that installed and dialed in but does allow you to adjust the rear camber curve and get the whole trailing arm back to a factory angle to gain back the little anti-squat that we lose when lowering the rear, and therefore potentially allow you to run a bit less spring rate. Millway has something similar but it's only the arm pickup points and they don't have something to offset the RTAB higher. I actually have an idea of how to offset the RTAB while running a standard full-size RTAB monoball instead but this setup is working for now.

[Stilt]

Hey Beau, would you be willing to share some more info about your front roll center adjustment setup? I’ve been trying to look into this and it seems like there aren’t a lot of off the shelf options out there, aside from angle kits.

Check out MRT

https://mrtengineering.fi/search?type=product&q=e46

https://mrtengineering.fi/products/bmw-e30-e36-e46-roll-center-bump-steer-angle-kit?_pos=1&_sid=e03661728&_ss=r&variant=40597060911293

https://mrtengineering.fi/products/bmw-e30-e36-e46-roll-center-bump-steer-kit?_pos=5&_sid=e03661728&_ss=r&variant=40596564279485

[bigjae46]

F8X wheels come in less aggressive offsets. I'm looking at an 18x10.5 et34 wheel with a 295/30R18 toyo RR. I'll start out with a pair and if it doesn't work out then I can use the wheels on the E9X M3 with a 12mm spacer.

Normally, wouldn't care about this. Now I am interested because I'll be running NASA TT3 Thought I would be able to squeeze into TT4. Now I'm running against sticky and expensive slicks, hoosiers and Goodyear 3Rs. But a 295/30R18 Toyo RR is $285 a tire. More rubber and $50 less than a 275/40R17? Screw all the feel and stuff...give me some more grip! I could throw on some Hoosiers but I love the challenge of outperforming with inferior tires.

For the track, more camber results in faster times. Period. The E46 lacks front end grip by design. Increasing negative camber is the best solution. The cost is a loss of straight-line braking power. To be fast in an E46, you really need to be trail braking anyway so not much of a tradeoff. You can increase front roll stiffness or front tire pressures which reduces the dynamic camber change but then its plow city into the turns. And that's the real challenge with the E46 - you're trying to overcome an inherent design weakness with significant tradeoffs.

That's the advantage of the E9X chassis - which doesn't have the terminal understeer that E46s have in stock form. Comparing the cars, I run -4.0 on the E46 on NT01s, -2.5 on the E90 M3 on NT01s.

[Nate047]

Yeah I was stuck in the same dilemma forever, couldn't find a solution I liked overall but I ended up with the MRT roll centre/bump steer kit, it keeps the steering ratio factory. I have an SLR race angle kit on my 330i and frankly it's been a mess and plan on removing it soon. Zero issues with the MRT so far and seems really well made, although if anything I'd guess the weak point is the lower arm stud that goes into the knuckle with the increased load it will see due to being extended but this is the nature of the beast. Theirs is quite overbuilt though. A couple of the race shops I work with do something similar but actually weld the stud permanently to the knuckle, theoretically for increased strength. I plan on cycling mine out maybe every other year for peace of mind, I do the same with wheel studs for the same reason anyway.

The rear is essentially a replica of a WTCC setup and is from MK Trackparts in Germany. Bit more work to get that installed and dialed in but does allow you to adjust the rear camber curve and get the whole trailing arm back to a factory angle to gain back the little anti-squat that we lose when lowering the rear, and therefore potentially allow you to run a bit less spring rate. Millway has something similar but it's only the arm pickup points and they don't have something to offset the RTAB higher. I actually have an idea of how to offset the RTAB while running a standard full-size RTAB monoball instead but this setup is working for now.

Awesome, yea I was considering the MRT setup. Pretty straight forward, basically press out and swap out the ball joints right?

I have the Millway rear bushings planned to go in with a whole refresh/build I'm doing, I also was wondering about why they don't offer an offset RTAB like MK. This is what the guy told me. Curious to hear what you think about this:

Hi Nate. Thanks for your reminder.
When a bushing are mounted in the subframe och hub, an eccentric bushing will change the geometry, rollcentre etc.
When a bushing are mounted in the control arm it will only change the length not the position where the bushing pivots.

The bushing always pivot around the bolt. So if you change the RTAB to an eccentric on a E36/E46! Where are the bolt? Exactly on the same spot regardless of how the bushing are designed.

It is common that people make eccentric bushings everywhere without really understand the purpose.

However there is one reason you can have eccentric RTAB. If you want to move the wheelbase for wheel clearance purpose. But then you have to install them 90 degrees difference what most people do.

I hope you understand what I mean. Otherwise let me know.


Best Regards
Samuel Lindkvist
Millway Motorsport

[bigjae46]

Check out MRT

https://mrtengineering.fi/search?type=product&q=e46

https://mrtengineering.fi/products/bmw-e30-e36-e46-roll-center-bump-steer-angle-kit?_pos=1&_sid=e03661728&_ss=r&variant=40597060911293

https://mrtengineering.fi/products/bmw-e30-e36-e46-roll-center-bump-steer-kit?_pos=5&_sid=e03661728&_ss=r&variant=40596564279485

That looks well thought out. I really like the extra mounting for the control arm bushing location!

Maybe I missed it but where is the wheel fitment chart? I run 17s so any roll center correction kit will be a tight fit.

[Stilt]

I think you would just have to measure the distance from the control arm to the barrel and compare it to the new hardware to see if it fits, but I am no expert lol.



Sent from my iPhone using Tapatalk

[bigjae46]

I think you would just have to measure the distance from the control arm to the barrel and compare it to the new hardware to see if it fits, but I am no expert lol.
Sent from my iPhone using Tapatalk

Thanks...I missed the pic in the description. I'm liking this option more after reading the description more closely. Mostly because of the extra reinforcement. I know welding turns off a lot of people but that's a small price to pay. This might become a high priority upgrade!

[Stilt]

Thanks...I missed the pic in the description. I'm liking this option more after reading the description more closely. Mostly because of the extra reinforcement. I know welding turns off a lot of people but that's a small price to pay. This might become a high priority upgrade!

They also have a lot of good info documenting the changes in suspension geometry as you interchange parts, but my brain is not completely woken up in order to understand all of it, lol.

https://mrtengineering.fi/pages/front-suspension-tech

[Stilt]

Awesome, yea I was considering the MRT setup. Pretty straight forward, basically press out and swap out the ball joints right?

I have the Millway rear bushings planned to go in with a whole refresh/build I'm doing, I also was wondering about why they don't offer an offset RTAB like MK. This is what the guy told me. Curious to hear what you think about this:

Hi Nate. Thanks for your reminder.
When a bushing are mounted in the subframe och hub, an eccentric bushing will change the geometry, rollcentre etc.
When a bushing are mounted in the control arm it will only change the length not the position where the bushing pivots.

The bushing always pivot around the bolt. So if you change the RTAB to an eccentric on a E36/E46! Where are the bolt? Exactly on the same spot regardless of how the bushing are designed.

It is common that people make eccentric bushings everywhere without really understand the purpose.

However there is one reason you can have eccentric RTAB. If you want to move the wheelbase for wheel clearance purpose. But then you have to install them 90 degrees difference what most people do.

I hope you understand what I mean. Otherwise let me know.


Best Regards
Samuel Lindkvist
Millway Motorsport

My brain must be cooked because I had to draw out a diagram to comprehend the message from MRT lol.

[cornerbalanced]

Awesome, yea I was considering the MRT setup. Pretty straight forward, basically press out and swap out the ball joints right?

I have the Millway rear bushings planned to go in with a whole refresh/build I'm doing, I also was wondering about why they don't offer an offset RTAB like MK. This is what the guy told me. Curious to hear what you think about this:

Hi Nate. Thanks for your reminder.
When a bushing are mounted in the subframe och hub, an eccentric bushing will change the geometry, rollcentre etc.
When a bushing are mounted in the control arm it will only change the length not the position where the bushing pivots.

The bushing always pivot around the bolt. So if you change the RTAB to an eccentric on a E36/E46! Where are the bolt? Exactly on the same spot regardless of how the bushing are designed.

It is common that people make eccentric bushings everywhere without really understand the purpose.

However there is one reason you can have eccentric RTAB. If you want to move the wheelbase for wheel clearance purpose. But then you have to install them 90 degrees difference what most people do.

I hope you understand what I mean. Otherwise let me know.


Best Regards
Samuel Lindkvist
Millway Motorsport

For the MRT kit I got, it’s simply a tie rod end. You need E9x tie rod inners, you mate to the two together and simply install with the spindle stud.

[Stilt]

For the MRT kit I got, it’s simply a tie rod end. You need E9x tie rod inners, you mate to the two together and simply install with the spindle stud.

Just to give some clarification (for other members) you are referring to the "Bump steer adjustable tie rod kit."

[cornerbalanced]

Just to give some clarification (for other members) you are referring to the "Bump steer adjustable tie rod kit."

Correct—not the other kit that alters steering ratio. If anyone has that kit I’m curious to hear about it. Seems more oriented towards drifters with 30% faster ratio…plus steering rack stops might make it annoying drive in tight areas. Ultimately shied away from it.

[BBRTuning]

Awesome, yea I was considering the MRT setup. Pretty straight forward, basically press out and swap out the ball joints right?

I have the Millway rear bushings planned to go in with a whole refresh/build I'm doing, I also was wondering about why they don't offer an offset RTAB like MK. This is what the guy told me. Curious to hear what you think about this:

Hi Nate. Thanks for your reminder.
When a bushing are mounted in the subframe och hub, an eccentric bushing will change the geometry, rollcentre etc.
When a bushing are mounted in the control arm it will only change the length not the position where the bushing pivots.

The bushing always pivot around the bolt. So if you change the RTAB to an eccentric on a E36/E46! Where are the bolt? Exactly on the same spot regardless of how the bushing are designed.

It is common that people make eccentric bushings everywhere without really understand the purpose.

However there is one reason you can have eccentric RTAB. If you want to move the wheelbase for wheel clearance purpose. But then you have to install them 90 degrees difference what most people do.

I hope you understand what I mean. Otherwise let me know.


Best Regards
Samuel Lindkvist
Millway Motorsport

Mostly straightforward to install, but the RTAB location design allows for some adjustment on install to account for toe adjustment range, so took a couple tries to get everything in the right place to allow for enough toe adjustment during alignment. Also will need to check clearance at full compression, I have adjustable upper and lower rear arms and at full compression the upper arm was pretty close to hitting the knuckle, but it did just clear.

As far as what Millway said, I certainly won't claim to know more than them on this stuff, but I'm having trouble understanding what they mean. The image below is the kit I have, unless I'm missing something it seems pretty clear that if you install the eccentric RTAB as in this picture, the front of the trailing arm will now be positioned higher in the chassis than stock, resulting in a raked angle of the trailing arm toward the rear of the car. Similar to if you were to raise the ride height. The disadvantage of this kit (same with the Millway) is now the spherical bearings are smaller and therefore theoretically will have a shorter service interval. My idea at least for the front location was to instead design a different RTAB mounting bracket where the bolt holes are simply higher in the chassis (maybe multiple holes), allowing you to get the same adjustment but with a factory style RTAB. Just comes down to clearance you have up inside the RTAB pocket.





Below are some pics of the MRT kit, as mentioned it's bump steer and roll centre only with no change to the steering ratio. Threw in CSL knuckles too at the same time.