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The 5 lug swap truth thread!!!!!!!!!!

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  • atmh
    replied
    moatilliatta - cool man! When I'm through with it I'll give you the full analysis of how the points change and kinematics throughout the range of travel. Might make a good compliment to your track experience.

    I would rather not run camber plates, but I'm also not building a serious track weapon. I'm really only aiming for 225 tires on 16" wheels. The MK60 ABS/DSC plus Megasquirt TCS are both for putting the power down without drama. Plus I'm doing dial-a-boost since honestly I don't want to run the car at full boost most of the time. IMHO it's more fun to drive a lower power car fast, but sometimes you just really want the juice, and it's nice to have both options available.

    As for the need for bigger rear axles... Maybe. Would be cool if there were stronger axles for the stock e30 track width. I don't plan on doing a lot of drag racing or spending a lot of time at full boost, so just replacing them every year or something like that would be a fine plan. Would love to try and find some bigger axles that fit the e30 rear end, but I'm not going for the Z3M stuff based on the prices I see these days. Would probably just design, laser cut and weld my own rear TAs based on the prices I see for Z3M stuff.

    Oh, and with my build if the jacking is too much I'll have to figure something else out, but for starters I'm going to try and do it without cutting, drilling, or welding any of the hard points. On the car I designed the suspension for we had I think 13 degrees of caster, or somethign close to that. The jacking was a lot, and while the car was small and light enough it was OK, it did result in a lot of steering effort. I'm sure it would be too much on an e30 with wide tires and perhaps a lot of scrub radius. The subsequent car had slightly less caster in favor of shorter front view swing arm lengths, I believe (at least that's the advice I gave the guy taking over for me when I left the team). Double wishbone so more ability to tune it than the McPherson strut on the e30.
    Last edited by atmh; 03-11-2022, 03:48 PM.

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  • moatilliatta
    replied
    1. Ignorance is bliss
    2. Ignorance is bliss

    You'll need bigger rear axles.

    I am an Club level racer and have setup many cars at a high Club level for 10+ years. I would be interested in helping or bouncing back and forth ideas on your setup.

    I have complete "Z3M" Setup. I believe the E36 knuckles and uprights are a lot stronger than E30's, less deflection and fatigue. I am still learning the differences of the E36 vs E30 suspension at a higher level. But The caster / Mechanical trail is what the key difference is and probably why the E36 runs less caster and so on. I'm looking forward find in out more.

    I am pretty sure with E36M you're using E36 fitment wheels.

    Bump steer and roll center is your choice of ride high, and many options out there if you want to go low, pick your poison.

    As noted before the Z3M rear runs an inch wider in the back. I'm over half there but my 245/40r17's (17x9et30) fit with rubbing. 1/2 way to go with the hardest the last 20% of getting a proper fitment (Early body).. Standard ops. Its just the convenient tire size with lots of options of compounds.

    There are many 4 lug brake kits, but I'm not to interested in wearing pads diagonal with wilwoods..


    My reason for 5 lug.
    Z3M - rear axles with Big bearings, Passenger side reinforcement hits the gas tank hose... no low hanging fruit there... Bigger rear brakes (E36M)
    E36M front has stronger uprights and knuckles, bigger bearings. Any car with camber plates will eventually crack the towers. Eventually Raised towers custom adj in the future so strut position not a big deal.

    Many good BBK packages around for E36 that have a good balance and pad options.


    End goal sub 2700 street track car, 1/2 cage S54 350WHp. 245's Maybe 275's widebody. Getting 1/2 way there. You'll need 275's if you really want to put down 350+ whp. Separates the Form vs Function.
    If the car cant make it around the track at its HP with out over heating, Blowing up, Breaking axles, Loosing brakes, not putting down traction its not a balanced package. IMO

    But the E36M 5 lug stuff I think has a chance, and it'll take work to optimize, and compromises will be made from and OEM to make work. The recipe is not bolt on, Just have to match the pick up points that the E36 used...

    Racers who optimized their setup rarely post on forums, but can be found at the track. Other parts are just tossed on, Ignorance is bliss. Sure, 9* of caster is fine on E36M 5 lug setup. Sure, people do live on fast food. And, Life goes on. It works.. I WANT BETTER.

    I drove my car around the block in the snow with 12* of caster, you'll learn what weight jacking is and how the rear grip goes away quickly due to it in low traction conditions.










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  • atmh
    replied
    moatilliatta: I'm building my car to have 1.5bar of boost. That's the goal, anyways. Definitely need bigger brakes. Weight will be close to stock e30 weight.

    Ok so I finally took the time to read this whole thread and two things came up for me:
    1. I'm less scared, because I've been getting the 96+ e36 M parts and that seems like it works for people
    2. I'm more scared, because it doesn't sound like anyone, at least not on this thread / publicly sharing their knowledge has done a full analysis of how the suspension geometry is changing with this swap.
    So I'm going to do a full kinematic analysis for my 1984 325e, which may not represent all e30s. I'm not 100% sure on what setup I'll do in the rear, but the current plan of a Z4 hub in the stock trailing arm means the geometry basically isn't changing, except for slightly wider track width, which I'm not particularly concerned about. For what it's worth, I have previous experience setting up, designing, and analyzing race car suspension. I'm no expert by any means, and I've never done a McPherson strut, but it should be fun and fruitful. I will share what I learn once I have "real" answers. I don't know what the "ideal" setup is for an e30, but I know enough to be able to compare a before and after for this swap and identify problem areas or what areas might need setup changes to compensate.

    Here's a quick rundown on what I'm thinking about with the front:
    • There's a lot of spitballing back and forth about caster, but caster isn't nearly as important as the resulting mechanical trail. As far as I can tell nobody is really talking about the spindle placement relative to the kingpin axis, which is also critical to how stable the car feels.
    • It doesn't sound like the e36M setup changes track width, but this is also pretty important to know. Since we're hopefully just bolting this assembly on without adjusting anything (except the lollipop control arm bushing) I'm not sure what's happening to track width and camber.
    • Steering geometry is also a really big deal. Is the steering pickup point in the exact same spot as on an e30? Probably not. How is Ackermann changing? Does the steering arm point still line up well to reduce bump-steer? Do we need to shim the steering rack in any direction? Up, down, front or rear?
    • Does the front roll center move significantly? Do we need different roll bars to compensate? Does it irreversibly mess with the Front/Rear roll balance?
    • Bonus thought: Half the "horror stories" I'm reading are also people running 17" wheels. 225+ width tires. Is there a tire in that size that's close to stock diameter? Is your rubbing issue a geometry issue, or simply that you're trying to run too big of a tire? Do we really want to take a hammer to our wheel wells when the answer might just be to run a tire closer to stock size? Are you willing to sacrifice performance just to have a big wheel and a wide tire?
    • Finally, I don't think there's a "high performance" reason to do a 5-lug swap if that's the ONLY thing we want (in my case, I want bigger brakes and 5-lug is the path I'm planning on taking to get there) but I'll do a quick calculation on wheel forces and lug bolts. Pretty sure even a heavily modified e30 is still light enough that the stock 4-lug is fine. Since I'm only doing this for the brakes, it's really important to know that I'm not unwittingly messing up the geometry in other ways. Bigger brakes with crappy handling is not the end goal.

    If the e36M stuff screws up the geometry in unacceptable ways, then I'll probably just go back to stock suspension bits and use a kit to fit a 5-lug hub on the stock e30 spindle with a caliper relocation bracket. Not my preferred solution, but a better one than messing up suspension geometry.

    If anyone reading this has gone through all the trouble of measuring all the parts and comparing before/after in CAD or some other software package, please let me know! No need to reinvent the suspension if it's already been done.

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  • Northern
    replied
    Originally posted by Whit3 E30 View Post
    Are you seriously driving that around with the strut mount secured by 2 an a half bolts???
    Clearly someone who runs MCS dampers would be the same person to drive their car with the towers hacked up. At least facebook would agree with that idea lmao.


    Re: 96+ m3 Caster -
    I guess we should've probably figured this out long ago, either from looking at late E36M strut mounts, or by looking at what caster E36 guys aim for.
    Plenty of facebook people word vomited E30 caster specs back like that was relevant after replacing the knuckle with one off a different car

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  • moatilliatta
    replied
    What’s your hp goal weight?

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  • atmh
    replied
    OE big brakes and wheels. e36 M3 sized with e38 style 5 wheels, specifically. Would love to be able to run e46 wheel speed sensors since I'm installing the MK60 ABS module.

    Ideally with as close as possible to stock e30 suspension geometry.

    I already have half the kit I need for 5-lug swap, but NBD if I have to change course.

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  • moatilliatta
    replied
    What are your goals?

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  • atmh
    replied
    Mmm, yeah, so even though there's a lot of info out there saying "it works!" the answer may simply be "no, not really".

    I bought a brake relocation kit for the rear to basically keep stock trailing arms and just make space for the bigger rear brakes from an e46 with a Z4 hub, and I opted *not* to do the front that way; I wanted to keep the e36 M stuff as the plan, but with all this added info about trying to get the front to fit, I'm seriously second guessing even that "tried and true" plan.

    Is there not a 5-lug hub that just slips on the front spindle? I hate caliper relocation brackets, but it's seriously starting to seem like the better option...

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  • moatilliatta
    replied
    Don't be so EMO.. Its mocked up for measurement purposes. Take the info as you will. Yes any car with camber plates with untouched towers will probably have cracks with proper track use.
    Last edited by moatilliatta; 03-09-2022, 07:29 PM.

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  • Whit3 E30
    replied
    Originally posted by moatilliatta View Post
    When this thread was popular I never had a chance to build any of this stuff. And now I do,and much better understand of how suspension works. Centered wheel has nothing to do alignment. And the problem is the E36M stuff has more castor trail. So Its a balance of correct suspension points top and lower of strut to offset the extra caster trail.

    I have Z3M Trailing trailing arms, And not sure if I had a set of wacky ones. But in stock form they had major tow out. Others don't seem to really align their car, and not much feed back out there. The larger bearings and stub axles are a plus. But the rear is like an inch wider. that means you'll need 12.5MM to get a matching / wider front track.

    Back to the front.. The wheel is just a pivot point, set the caster and the pickup points now mark them selves. This is how I got down to 7.5* castor from 11.75* with ADJ control arms. Trial and Tribulations can be seen in my build thread.
    96+ M3 Knuckes, MRT DTM style CA with roll center, Vink motorsports, and the camber plate explains itself.
    I'm sorry but that picture shows your horrible destruction of a E30 strut tower. I know strut tower modifications have been around for awhile but that doesn't classify as a good choice IMO. That tower looks like a HUGE weak point now and they weren't the strongest towers to begin with. Are you seriously driving that around with the strut mount secured by 2 an a half bolts??? I would be very very very careful if I were you. This I just my opinion but if you have to decimate a piece of your car to make your idea come to life... idk if it truly should see the light of day. It's not my car an not my money so do what you want to do but that picture brings tears to my eyes cuz I feel the pain of that car 😭😭 (crying faces)

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  • Whit3 E30
    replied
    Originally posted by atmh View Post

    I'm also currently working on this swap, my understanding is as follows:

    The "only" front setup that works with e36 bits is to use 1996+ e36 M (identical to Z3M) stuff. You have to use the control arm, spindle, and the hubs to get the right geometry, and an adjustable caster plate might also be required. You need an "offset" control arm bushing to get the wheel centered in the wheel well properly. If I understand correclty, there's no way to get non-M e36 stuff to work without really messing up the front geometry. I plan on analyzing the front suspension when I do my swap so I can see for real how everything changes with this swap.

    For the rear it seems like there's a lot more options that work. e36 318Ti trailing arms and hubs are a direct swap, I believe. the 4-cyl "narrow body" Z3 TAs also work. The "wide body" Z3 stuff adds too much offset. I believe the Z3M adds less offset (20mm) so you need ET40 wheels in the back, but the rear Z3M TAs are extremely expensive these days, so not worth it IMHO. My original plan was to use Z3M stuff so I could get the beefy halfshafts and bigger brakes, but the TAs are so expensive I'm changing course, and even thinking of abandoning 5-lug swap all together since the benefits are hardly there. There's a guy selling brake relocation brackets to use e46 calipers and rotors, on Z4 hubs. The Z4 apparently is only +2.3mm or something like that (nearly inconsequential additional offset), and this is the new path I'm looking into.

    Doing all the research I've done at this point it really does seem like the smart thing to do is just run an e30 big brake kit, if the goal is bigger brakes. The only tangible benefit from 5-lug swap might be that you can get a vented rear rotor, and I don't really know if that's worth it. Lots of time and $$$ for not much in return.

    Having said all that, I'm going for a sleeper build, so OE brakes and OE wheels are pretty relevant to that overall look, so the e38 Style 5 16" wheels and OEM brakes are strongly preferred for me than an aftermarket big brake kit, which is more or less the only reason I'm still pursuing this. If I didn't care about the OE look I would probably go for a big brake kit and appropriately sized 4-lug wheels and call it a day.
    Ya after i started to see the $$$ pile up just for 5 lugs, I decided to stick with my 91 318is brakes, just get a better rotor and race pads for now. Maybe after a few years of driving and I feel like changing it I'm just going to go to 4 lug e30 big brake kits from massivebrakes or someone like that. I have 16x8.5 et20 so O.E look is out for me lol. I have to roll my fenders to make them work. I'm running a 10mm spacer and I don't want 17s or anything like that so I don't feel or see the need to go to 5 lugs. Plus going 5 lugs adds more unsprung weight which is the opposite of what I want to do.

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  • moatilliatta
    replied
    When this thread was popular I never had a chance to build any of this stuff. And now I do,and much better understand of how suspension works. Centered wheel has nothing to do alignment. And the problem is the E36M stuff has more castor trail. So Its a balance of correct suspension points top and lower of strut to offset the extra caster trail.

    I have Z3M Trailing trailing arms, And not sure if I had a set of wacky ones. But in stock form they had major tow out. Others don't seem to really align their car, and not much feed back out there. The larger bearings and stub axles are a plus. But the rear is like an inch wider. that means you'll need 12.5MM to get a matching / wider front track.

    Back to the front.. The wheel is just a pivot point, set the caster and the pickup points now mark them selves. This is how I got down to 7.5* castor from 11.75* with ADJ control arms. Trial and Tribulations can be seen in my build thread.
    96+ M3 Knuckes, MRT DTM style CA with roll center, Vink motorsports, and the camber plate explains itself.

    Leave a comment:


  • atmh
    replied
    Originally posted by Whit3 E30 View Post
    So I know this is a really really old thread, but I have a question. I have a 1984 318i with the M10B18 and G240. I have put money into the M10 and will eventually need to 5 lug swap it for bigger brakes from a E36(going to boost it, expecting 300+ hp and 200+ Tq). I have already changed the suspension and brakes front and rear, taken from a 1991 318is. So rear subframe, trailing arms, brakes, ect. Front struts and brakes ect. are all from a 1991 318is, then I bought brand new 84' 318i lower control arms. So now that most of the background information is out there, here is my question. To do a 5 lug conversion, could I use 96'+ non-M Z3 front struts and knuckles, brakes , ect. then a adjustable top plate for e30, with stock e30 non-M lower control arms with a offset solid control arm bushing for the front? Then the rear could I use again 96'+ non M Z3 rear hubs n bearings an brakes? (I Don't know if they use the same size bearings as the 91' iS.) Then get a bracket made for the brake calipers on the 91 rear subframe trailing arms. Or should I just take both trailing arms with brakes and stuff still attached and install them on the 91' Is rear subframe? Could this work as a 5 lug conversion???? Please help!! Or tell me what I'm missing from the setup??
    I'm also currently working on this swap, my understanding is as follows:

    The "only" front setup that works with e36 bits is to use 1996+ e36 M (identical to Z3M) stuff. You have to use the control arm, spindle, and the hubs to get the right geometry, and an adjustable caster plate might also be required. You need an "offset" control arm bushing to get the wheel centered in the wheel well properly. If I understand correclty, there's no way to get non-M e36 stuff to work without really messing up the front geometry. I plan on analyzing the front suspension when I do my swap so I can see for real how everything changes with this swap.

    For the rear it seems like there's a lot more options that work. e36 318Ti trailing arms and hubs are a direct swap, I believe. the 4-cyl "narrow body" Z3 TAs also work. The "wide body" Z3 stuff adds too much offset. I believe the Z3M adds less offset (20mm) so you need ET40 wheels in the back, but the rear Z3M TAs are extremely expensive these days, so not worth it IMHO. My original plan was to use Z3M stuff so I could get the beefy halfshafts and bigger brakes, but the TAs are so expensive I'm changing course, and even thinking of abandoning 5-lug swap all together since the benefits are hardly there. There's a guy selling brake relocation brackets to use e46 calipers and rotors, on Z4 hubs. The Z4 apparently is only +2.3mm or something like that (nearly inconsequential additional offset), and this is the new path I'm looking into.

    Doing all the research I've done at this point it really does seem like the smart thing to do is just run an e30 big brake kit, if the goal is bigger brakes. The only tangible benefit from 5-lug swap might be that you can get a vented rear rotor, and I don't really know if that's worth it. Lots of time and $$$ for not much in return.

    Having said all that, I'm going for a sleeper build, so OE brakes and OE wheels are pretty relevant to that overall look, so the e38 Style 5 16" wheels and OEM brakes are strongly preferred for me than an aftermarket big brake kit, which is more or less the only reason I'm still pursuing this. If I didn't care about the OE look I would probably go for a big brake kit and appropriately sized 4-lug wheels and call it a day.

    Leave a comment:


  • Whit3 E30
    replied
    So I know this is a really really old thread, but I have a question. I have a 1984 318i with the M10B18 and G240. I have put money into the M10 and will eventually need to 5 lug swap it for bigger brakes from a E36(going to boost it, expecting 300+ hp and 200+ Tq). I have already changed the suspension and brakes front and rear, taken from a 1991 318is. So rear subframe, trailing arms, brakes, ect. Front struts and brakes ect. are all from a 1991 318is, then I bought brand new 84' 318i lower control arms. So now that most of the background information is out there, here is my question. To do a 5 lug conversion, could I use 96'+ non-M Z3 front struts and knuckles, brakes , ect. then a adjustable top plate for e30, with stock e30 non-M lower control arms with a offset solid control arm bushing for the front? Then the rear could I use again 96'+ non M Z3 rear hubs n bearings an brakes? (I Don't know if they use the same size bearings as the 91' iS.) Then get a bracket made for the brake calipers on the 91 rear subframe trailing arms. Or should I just take both trailing arms with brakes and stuff still attached and install them on the 91' Is rear subframe? Could this work as a 5 lug conversion???? Please help!! Or tell me what I'm missing from the setup??

    Leave a comment:


  • bimmer630
    replied
    Clavin, I actually copied your setup in a way... I definitely read your threads a lot before doing my 5 lug

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