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:
Here's a quick rundown on what I'm thinking about with the front:
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.
Ok so I finally took the time to read this whole thread and two things came up for me:
- I'm less scared, because I've been getting the 96+ e36 M parts and that seems like it works for people
- 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.
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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