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1st Mod - Wheels and Tires

4685 Views 11 Replies 9 Participants Last post by  Miss Mercedes
Recently I purchased a previously loved 2013 Pure.
I like the care, it's fun to drive, and a gas at a Parking Lot Autocross (Non-SCCA).

The stock tires were worn out, so I replaced them for safety sake, but the car still pushes on the skid pad and I can't count how many times I've straighten the outer rims after a pothole encounter.

I researched and researched, but few threads shared their backspace info. I did find a chart, but it seemed to me some combos were by racing teams with spacers.

Discount tires can order in rims, but I figured if I did that, I would also order tires and make it a bolt on affair.
There are also companies which make replacement OEM wheels, but want $$ for them.

TireRack sells Alutec Grip 3 wheels in a 15" rim that measure 15X5 (20MM BS) Front and 15X6 (24MM BS) Rear that are a bolt on, no fuss upgrade over the stock steel wheels and at this writing are $110 ea.
They come in 2 tones of grey, and clear everything, no spacers required.

For tires I went with 185X55X15 Front, and 195X45X15 Rear because that's the best I could do with Toyo Proxes.
I got a call from the Tire-Rack Rep about the rears as "Smart Car owners don't order that size", but I wanted the Toyos. If I wanted to go outside that brand I would have chose a 205X55X15 rear instead.

The combo arrived at the door, assembled, and balanced in 2 days. Not too shabby :D

The speedometer read 4.5 mph fast at 60 before, and now it's only 3 mph fast.
MPG is unchanged at 43 combined City/HWY - heavy on the HWY.

Pushing (understeer) is much reduced.
The car actually feels safer then before and on the track. Gone is the "Skipping" and Rocking caused by the fronts bouncing as they skid through the understeer. Truth be told, the nannybots were a lot happier because the transitions were smoother.

Daily driving comfort is about the same. The chassis is pretty stiff, so I don't expect much.
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Most of us with same size front and rear rims run the 195 front and rear.
Have you considered the Brabus wheel/tire combo? Granted if you had problems with bent damaged rims before the Brabus wheels are even more delicate. But the car sticks like glue to the road. 215/35R17's on the rear and 175/55R15's front. Car hunts a bit on deeply rutted roads but tracks nice and straight at highway speeds even passing trucks. Jim's 195 front rear I think is more sane and a lot less prone to damage. Though if for some reason you got some money burning a hole in your pocket!

smart car BRABUS ?Monoblock VII? 16/17" Wheels (set of 4) Online Store - smart car Parts and Accessories
Well as I mentioned I did the research.

As I mentioned, the car needed to commute and race, so road and track manners were important.

With a 175x55x15 the sidewall would be about right, but I would have to stick with all seasons, a steel rim would cost me $120 and I'd have to order tires, order sensors, and have them mounted. I'd be looking at $500. Same deal on a 195x55 on a 5.5 rim, though it appeared there would be a bit of sidewall roll.Though an improvement, not optimal, so I decided to pass. ?

I did try different option packages on Tire Rack but set of Barabus size wheels would have bumped me a class due to the 17" rims. Scratch that. I want to be atleast within a few seconds of my class ?

The rims I spec'd in my post are .5" over stock width, which allowed me to run the tire combo I spec'd.

I'm satisfied, and in the end, that's all that maters. I just figured I'd share what worked for me, and include specs in case anyone else is doing research ?
My 451( well it was going to be but I can't seem to attach the pix.)


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If it is white with a silver tridion and a boat behind it, then I can open the link and it looks good.
Ron, let me make sure I got this right. You ordered a 15X5 and 15X6 Front/Rear rim combo, correct?

I'm still running the stock rims and tires, but found that a 20 mm spacer behind each front rim helped reduce understeer and increased front grip. Don't know if this is allowed under your autocross class, but the 40 mm total helps make up some of the 4" difference in track width between front and rear. The spacers created a bit less dynamic stiffness that I compensated for by running a couple of extra PSI up front, which I could because impact harshness was reduced. I also had my alignment shop loosen all of the front suspension bolts and then tighten them back up using up the tolerances to get me as much negative camber as possible. I ended up with about -0.4 to -0.5 degrees, an improvement over the -0.1 that I had stock. Ultimate grip is up by probably 5-7%, and though it still understeers quite a bit, it's at least tolerable now running 8/10ths or less. Above that and the front tires still get ground to a dust.

I have an ED so running wide tires is going to sacrifice too much range. I'll probably either purchase a couple of identical rear rims or go with four 15X6 rims and run a 175/55 and 185/55 combo, probably having to downsize to a 15 mm spacer up front.
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I just ordered the ALUTEC Grip3 also since it seems that Genius doesn't want to make 15" Smart wheels anymore. I went with a 15x6" square setup with 185/60/15 tires. I understand I run

the risk of some very mild rubbing and the benefit of an improved ride cushion and spot on odometer. I plan to run them around 32psi front and 34psi rear or higher if the added sidewall can afford me some more comfort. Order should be here in a couple days and I should be getting them mounted up within a week or so. =)

OP Ron, it seems as tho the Speedo is running off the front tires then if your speedo error improved cuz it would have gotten worse with those smaller rears if that was the case.
Good choice! I'm running the same rims. I chose the gray. I ordered new tires this year from Discount Tire (Nitto NT450
P 195 /50 R15 81V SL BSW), reading on the forum I kept seeing people noting that they run 195/50 R15's on all 4's. Can you run those even on the staggered rim widths?
Kyle, the specs on the tires you have say they fit a 5.5 to 7" rim, and all measurements of the spec were taken on a 6" rim.
That means the sidewalls my bulge a bit on a rim smaller than 5.5". I guess you'll have to test fit, but if they rub it will most likely be at full left or right steering lock.

I've never been a fan of spacers, I've seen them break off-road... YMMV

I had a great summer racing the Smart and driving it to work! The understeer was much reduced with the tire/wheel combo I used, and was brave enough to put the car in diagnostic mode and really push it without the nanny bots spoiling my fun.

Unfortunately, those tires SUCKED in the winter, so I went back to the cheap stamped aluminum junk stock rims and mounted some Nokian tires, oversized to Passion option size. This proved to be another winning combo and the traction light rarely came on all winter, even on icy hills.

This was interesting: This winter I installed a cheap ScanGauge readout to get RPM.
What I found out is the Car knows how fast it is going, but the Speedo is lying by +5mph at 70mph.
With the Winter Tire/Rim setup, at a Speedo reading of 75mph, the ScanGauge read 70mph, and so did the phones GPS.
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This was interesting: This winter I installed a cheap ScanGauge readout to get RPM.
What I found out is the Car knows how fast it is going, but the Speedo is lying by +5mph at 70mph.
With the Winter Tire/Rim setup, at a Speedo reading of 75mph, the ScanGauge read 70mph, and so did the phones GPS.
Welcome to SCoA. More speedo discussion here ...
I've run 195/50/15 tyres on the standard staggered set of 15 inch Genius Darwin wheels for most if my 451's life. They never rubbed. Speedometer was 5 mph optimistic at highway speed.

I now run 185/60/15 on those same wheels. They rub when you're taking a banked turn fast (clover junction), when leaving/entering sloped parking lots, and sometimes on potholes. There's no real damage to the parts they rub and speedometer is right on the dot, even at highway speed.
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