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Discussion Starter #1
I keep seeing two different numbers posted for Turning Circle/Radius.

Bernie (dealer) once said something about "door to door" vs "curb to curb" (measuring from the body rather than the wheels) or something like that ?!

Is this one of those wacky measurements or what?

Usually publications list "turning circle", but sometimes they list "turning radius" (which should be circle/2) sometimes they list a value which is clearly the turning circle, but they mislabel it "turning radius".
(for an example check out http://www.toyota.com/mr2/specs/index.html
17.4ft turning circle? I don't think so!)

Now if to hopelessly confuse everyone we have two different values cropping up in different places.

The official site http://www.lexus.com/is/specs.asp
says:
"Turning Circle 34.1 ft"

Autosite.com (which seems to have very good information) http://www.autosite.com/new/datashts/techspec/2270.asp
says:
"Steer Diam.(Curb) 37.4"
"The distance required when turning the car tightly (in feet). The outside front, curb-to-curb measurement is used."

I have seen that 37.4 number posted elsewhere...

So when trying to compare the IS300 to other cars, which number is the one to use?!

BMW 328i/330i is listed as being "34.4ft"... Is IS300 better or worse?

Subaru Impreza 2.5RS is listed as being "33.5ft"... Is IS300 a little worse or a lot worse?
 

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I think Lexus literature gives the GS300's turning radius as 37.1 ft...I would certainly hope the IS's is smaller.
 

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The arc of the wheels (curb to curb)is the lesser of the two figures. The measurement that allows for the body overhangs in space (wall to wall)is the larger one. I think of this like being in an alley between two brick walls and having to turn around. So both figures are correct. The IS300 suspension preloads when you put two people in it and has a pretty low chin so it might do damage if the curbs are the height of the ones here in the DC area. This is a smaller wheelbase than the GS300 and you would assume a tighter circle. I guess they figure everyone will be drifting around the corners(see previous posts)on their way for a burrito. Ironically the Lexus with the tighest turning circle is the LS400.
 

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Shouldn't the turning diameter depends on the distance between the front and back wheel (wheelbase?). It would be logical to assume that the car with the shorter distance from the front to back wheel will have the smaller turning diameter. Isn't the BMW 3 series wheelbase slightly longer than the IS300? If that is true, then the 34.7 ft for the 3 series vs. 34.1 ft for the IS sounds about right.
 

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Discussion Starter #5
I think a major factor in the turning circle is the travel of the steering rack. They must have a limit that they engineer into the system.

My guess is that some factors like
tire wear and pressure on the power steering pump come into play.
 

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Discussion Starter #7
Thats my point... 34.1ft will make a U-turn on a narrow street. 37.4 will get you stuck.
 

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I am going to practice my handbrake turns more often. I usually reserve those for snow. I just heard today that we sold 14 Audi S4's in the last month or so next door at Rockville Porsche Audi. That blew my mind that a niche car was doing so well. This should mean that the IS300 market is very active.
 

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Discussion Starter #10
Bernies comment about handbrake turns wasn't random - he was saying "the indicated turning radius doesn't apply if you slide the rear wheels".

In other words - back to the "bootlegger turns" like Bryan did in the IS300 commercial.

------------------------------------------

Most modern handbrakes don't clamp enough to lock the rear wheels unless you are on snow or ice...
 
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