Join Date: Apr 2017
Location: Redmond, WA
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The backstory: I went from a '95 Miata to the 451 ED, and I've debated modding as decreasing the limited range wasn't something I wanted to happen. With the Miata, I kept it mostly stock, primarily adding roll stiffness and shocks with more rebound damping but leaving the stock springs. With a good alignment, I had a nimble, tossable vehicle that was very eager to turn and had very benign and neutral handling behavior.
With the smart, I found that the stability control system as a whole just isn't compatible with driving near the limits of traction. One major problem that can't be solved even by disabling the stability control and ABS is that the regenerative braking gets shut off if the sensors believe a loss of traction is imminent. This occurs at certain times even when there is no loss of grip and not cornering near the limits of tractiion, such as when hitting an apex that is at the crest of a rise. The sudden unweighting causes the car to start freewheeling, which then **causes** a loss of traction as all of a sudden the rear braking just goes away and the car starts to understeer more heavily.
So I've given up on trying to make my smart into a Miata clone, instead concentrating on just making it good at 80% and realizing that above that and there are going to be deficiencies that can't be driven around. With that said, I've only addressed front track width, using 20 mm spacers in the front behind the OEM 155/60-15's, and having my alignment shop loosen and retighten all of the components up front, getting me between -0.4 and -0.5 degrees negative camber at each front wheel while also setting toe at 1/16" or 0.05 degree toe-in at each front wheel, versus the factory spec of 0.25 degrees toe in.
These changes have reduced understeer by about a third, have removed most of the rut/tramlining/wind sensitivity at freeway speeds, and have helped transitional behavior as the front tires just don't grind as much with the wider track and little bit of negative camber. Cornering speeds have gone up about 2-3 MPH in the wet in steady state, maintenance throttle turns that previously could be taken at 30 MPH, so the traction gain is pretty significant. It really is about where I'd want it to be, if I could just further reduce the understeer more, so it just feels more eager to turn.
I don't know that I want to put spacers in the back. The front and rear track are now close enough that cornering feels natural, and I'd hate to get back to the stock track stagger that it had because it felt like the turn vector was just weird, kind of like riding a tricycle almost - this is probably that crabbing that you were talking about. Rear wheels on the front sound like a good idea and that's where I was planning to go, but I'd much rather address rear roll stiffness first, seeing how much more I can get, before adding more grip to the front that may make the understeer feel, feel worse.
Be happy to hear any other suggestions. I've taken my smart to a track driving instructor I know who also has fabrication experience, and he says he can custom make something to get me around -1.5 degrees front negative camber, but it's going to cost a few hundred dollars. A custom rear sway bar would be about the same cost as ordering the one from Europe - roughly $600 to my door. Those, I thought, were the only choices I had until hearing of this bushing upgrade. I'm really interested in finding out more about it before making a tire/rim choice.