What's the result of this? Is this problem fixed for 2008 or not?
Here's why I ask: (Please assist if you know.)
I am considering buying a 2008 Eos Komfort for my kids, and the tires on it are worn to the indicators. They are Nexen (vomit!) brand and I wouldn't let my dog drive such a death-shoed vehicle.
I have a set of Goodyear Eagle GTs in my garage that, for long and convoluted reasons, never went on my '93 Honda del sol si, and remain brand new, properly stored, free of dry-rot, and having never touched pavement. I thought I'd shoe the 2008 Eos with these Goodyear Eagles.
Problem here: Tire size needed for stock 16" alloys on 2008 Eos Komfort is: 215/55R16. My Eagles are 205/50R16. A lower profile tire. The charts tell me that the circumference difference is 79.5" vs. 75.6", or almost exactly 5 percent SMALLER new tires in terms of rolling distance.
Thus, if the speedo is exactly correct now, based on the difference, the speedo will read:
20 MPH when the car is actually going 19.1 MPH
30 MPH when the car is actually going 28.6 MPH
40 MPH when the car is actually going 38.1 MPH
50 MPH when the car is actually going 47.6 MPH
60 MPH when the car is actually going 57.2 MPH
70 MPH when the car is actually going 66.7 MPH
80 MPH when the car is actually going 76.2 MPH
90 MPH when the car is actually going 85.7 MPH
Thus, using these smaller tires will cause the car to "think" (and report) that it's traversing 100 miles when it's really only traversing 95 miles. However, if this 2008 EOS Komfort is ALREADY OVER-REPORTING its mileage (and speed) by 3 percent, I've now compounded that by 5 percent more, for a total just a smidge over 8 percent -- a significant difference.
I can see this two ways:
a.) OK, this is fine. My kids will, of course, violate speed limits, as all kids do, but they won't be violating them by as much, since they'll look at the speedometer and it will tell them they're going 8 percent faster than they're really going. They can brag to their friends: "I had that thing up to 90 yesterday on the highway" and really they only hit about 83. Dad feels better. (Sure, mileage racks up faster than actually driven miles, but since I'll keep this thing for them throughout high school and college, until it's dead, I don't really care what the odometer says.)
b.) This is a problem -- anything this far off (8 percent) is damn noticeable and thus they'll ignore the speedo and drive fast anyway. Plus, maybe I'll take out a 3-year/36k mile warranty on this 2008 beastie and then I will want accuracy on the odometer.
This all begs yet ANOTHER question for you:
Tires WEAR and get smaller in diameter/circumference. I wonder how much wear has come off of an 80" circumference tire when it hits the wear marks, and when it hits minimum legal tread (only 1/16th of an inch here in Florida -- that's a shockingly small 1.5mm minimum tread required - Wow!).
I guess I'm going to try to answer this one myself right here and calc as I go: I've read that starting tread depth is 10/32-11/32 of an inch, so the tire tread loses about 1/3rd of an inch over its full life.
That 1/3" of lost radius translates to just over 2" of circumference lost on fully-worn stock tires for the 2008 Eos, dropping C from 79.5" to about 77.3" meaning that my new Goodyear Eagle tires at 75.6" are now only about 2.2 percent off of the size of fully used stock Eos tires.
Now that we consider the normal wear, the difference doesn't seem so big, at least until these smaller new tires wear down to the minimums (but I'd replace them long before then), but if I let them just stay on, then I'm back to 5-8 percent difference, depending on whether or not the 2008 Eos has that same speedometer/odometer problem as the 2007 : underestimating speed and overestimating mileage (i.e., overestimating tire size).
I did the math here mostly in my head (whatever part I didn't get from the tire size charts), but I'm pretty sure it's fairly accurate.
Any thoughts on doing this? Again, I'm thinking of putting 205/50R16s on a 2008 Eos in place of its current, mostly worn 215/55r16 Nexen (junk!) that need to come off anyway.
Opinions welcome. Please read my full post before writing about something I've already covered carefully and in a mathematically correct manner.
2012 Eos Executive, Black Oak Brown, Black Interior, Every Conceivable Option, built for US market.
- (Considering) 2008 Eos Komfort for the kiddies