New wheels/tires have transformed the car

[DavidV]

Originally Posted by bottlerocket

Can you swap tire sensors from your original set of wheels to the new one?

Yep. That's exactly what I did.

** DavidV

[smartbetz]

David,

Looks great. I really think the +1 & +2 wheel sizings look better. They should give you better lateral traction as well.

sb

[DavidV]

Originally Posted by smartbetz

David,

Looks great. I really think the +1 & +2 wheel sizings look better. They should give you better lateral traction as well.

sb

Thanks - ultimately since the aspect ratio is what dictates grip, a +1 or +2 would help if you go wider as a result. The thing is, you can also go wider in a 15" and not run into as much of a weight increase as you might otherwise with a +1 or +2. By staying with a reasonably light 15" I made a concentrated effort to minimize adding unsprung or rotating mass with this set-up.

-- DavidV

[jkirsch]

This is all most interesting, as I have been reading "Smart Thinking" by Tony Lewin, and according to that book, the narrower front wheels were in response to poor handling in the "Elk Test". A Mercedes A-series car rolled over in that test, and the smart folks along with Mercedes freaked, as the CityCoupe was of a similar, but more extreme design. They said that the ESP (then called "TRUST") could not compensate enough, so they widened the track of the rear wheels and narrowed the same (along with the wheels) on the front. They (Mercedes) also added 35 kg to the front end of the car to help the handling. This after the smart engineers had spent considerable effort in lightening the car.

So to hear that handling is better with the wider wheels is fascinating. I'm not doubting it, don't get me wrong - it's just interesting. It makes me wonder what has been changed in the car since that book was written. Perhaps the narrow front tires are a vestigial entity from that era and simply remain for asthetics or convention.

If you get a chance, get a copy of the book. It is a fun read, and quite informative. Amazon has it for $13.57 - hardcover.

Jeff in Atlanta

[RussBarnes]

I now have about 200 miles on my four 185/60-15 Michelins and can make the following report:

* As Randy reported the ride, the feel and the general handling feels better and I have mine at 26#/39#. That is all the plus factors that have been discussed.

* My tires are 1" larger diameter because I wanted optimum ride and had to have Michelins from prior tremendous satisfaction with that brand. I haven't run any OE rears on the front, but I have no doubt that these are even a softer ride since taller and have the Michelin soft sidewalls.

As to any cons:

* When first installed I was dissapointed with the noticable loss of acceleration away from a stop. Not bad when rolling, but dead start it felt like it was lugging unless I gave it a lot of pedal and I don't drive that way. That was fixed when I installed the Doug Thorley exhaust. Not that I like the increased noise, but the added bottom end has solved that and makes it feel like it did with OE tires, plus on the ScanGauge I can already see better mpg.

* I don't have any Elk to test, but I can say I notice a different feel in stopping and slow speed turns. Not bad, just different. Who knows, maybe it will turn over if it sees and Elk (or a Peterbilt in front of it) but I have driven rattle traps that I have constructed before that I know would have been considered "unsafe at any speed", but I try to exercise caution rather than drive over my head.

* These tires are close to hitting the front slashwells, but even with two in over 450# we never scrub, I'd just like a little more clearance. Plenty side to side, just the OD is a little tall.

* When I do mpg calculations I need to multiply calculated figures by 1.04 to get true reading due to difference in tire diameters.

Would I do it again? Yes, in a flash but if I had my druthers - same brand tire, smaller dia (not available yet) and a slightly quieter muffler.

[mmmeat]

Originally Posted by jkirsch

This is all most interesting, as I have been reading "Smart Thinking" by Tony Lewin, and according to that book, the narrower front wheels were in response to poor handling in the "Elk Test". A Mercedes A-series car rolled over in that test, and the smart folks along with Mercedes freaked, as the CityCoupe was of a similar, but more extreme design. They said that the ESP (then called "TRUST") could not compensate enough, so they widened the track of the rear wheels and narrowed the same (along with the wheels) on the front. They (Mercedes) also added 35 kg to the front end of the car to help the handling. This after the smart engineers had spent considerable effort in lightening the car.

I would certainly never claim to be anywhere near as smart as the Mercedes engineering department, nor did I stay at a Holiday Inn Express last night, but ...

Most automotive companies engineer their cars to understeer rather than oversteer for some reason. I guess they'd rather have you drive straight off the cliff rather than turn with the possibility of kicking the rear end out and not dying. It's my understanding that the A-series (?) car had a tendency to oversteer and it transferred the weight abruptly, which caused the car to roll. The A-series also carries it's weight fairly high, which was probably something that contributed to the roll-over state, too.

The Smart - even though it looks tippy - carries it weight much lower, and I don't believe that the wider wheels will do anything that would cause it to grab, shift the weight or flip over without hitting a curb or some other object first.

Back in the bad ol' days, I had a Trihawk, which was a three-wheeled vehicle powered by a Citroen pancake motor. The engineers made the car with two wheels in the front - rather than the rear - because it gave the car a more stable drive, and allowed the driver better control of the vehicle than a tricycle vehicle with one front wheel and two rear ones. The Trihawk also oversteered, and was very easy to drive at freeway speeds.

Personally, I'd rather oversteer than understeer. I should tell the car which way I want it to go, not have the car tell me it's going somewhere else.

Your pal,
Meat.

[jkirsch]

Great info, thanks.

I'm just trying to figure out what has changed since that book was published in 2004. Quite a lot, it appears. I do like the look of the wider front tires/wheels. And Meat, I'm with you, I prefer to command the vehicle, not the other way around.

I do wish there was a similar caliber book to cover the last four years, as there appears to be a gap. Still, the description of the manufacturing process alone is worth the price of the book.

Oh, and they also lowered the seats and the suspension a bit in response to the Elk Test. I'm thinking that it lowered the car 30mm total, but the book is at home, and I'm not, so that number could be off. It wasn't a lot, though.

Jeff

[16d @ 4]

DavidV,

Are you losing any "real world" MPGs due to the larger tiress (ie higher frictional resistance from more contact area).

Sorry for the question; I just want to make sure I don't loose any MPGs as the good MPGs was the reason why I bought this car.

PLease advise, and
Thanks in advance


RE:

Got it; psot 27.

Thank you,

[scirocco16v]

and the cost?

[PeteInLongBeach]

I'm curious how this modification might affect hydroplaning and fuel consumption...

The original set-up was strategically designed to be safe & forgiving for average driver's skills (which probably does not include throttle induced oversteer), and to address any problems related to the original MBZ A-class handling issues.

Regarding understeer vs oversteer: I was once a passenger in a car driven by someone of average skill who hit a patch of wet pavement unexpectedly. This happened while simultaneously going around a sharp corner and over a rise. If the car hadn't been designed with a tendancy for understeer, we would have spun out and over a cliff. Instead, it was predictable, forgiving of any errant driver input, and was easily brought under control.

I'll take understeer any day...