Max Rebo Posted October 2, 2006 Share Posted October 2, 2006 Long post, but please bear with me. I will be buying a set of winter tires (and maybe wheels) for my spec.B soon, and I've been wondering... Is the speedometer on the standard LGT calibrated the same as that on the spec.B? The reason I ask is because of the significant difference in tire sizes between both trim levels. (Significant to me, anyway...) The spec.B has 215/45-18 OE tires, while the standard LGT has 215/45-17, that's a 3.9% difference in diameter. Now, I could just buy 215/45-18 winter tires for my OE wheels, but unless places such as TireRack will have a larger selection within a month or so, there are exactly 2 choices. One is expensive ($195 for Blizzak LM-22s) and the other is cheaper (~$150 for Pirelli Sottozeros). As you can see, the currently selection is "teh suck." I could buy new 17's for the winter and use 215/45-17, but then I don't know if a 3.9% difference in overall gearing is important. What I'd really like is a set of Dunlop M3s or maybe the new 3Ds, which is why I've also considered new 17's, and going to 225/45-17 for the winter. Then I'd likely sell my stock wheels and buy something new next spring. That will likely be 18x7.5 with 225/40-18 tires. I've found that the 225/45-17 and 225/40-18 sizes are ~2.5% shorter than the OE diameter, so the difference (to me) would be more acceptable. In the end, there really isn't a huge selection of any 215/45-xx tire. That just plain sucks. What would you do in this situation? I'm really leaning toward new 17x7.5 wheels and 225/45-17s for the winter and then a new set for summer. This will give me the best and the most options when it comes time for replacement tires. Link to comment Share on other sites More sharing options...
Vimy101 Posted October 2, 2006 Share Posted October 2, 2006 215-50-17 are pretty close to Spec. B OEM tire circumference. This is the set up I'm going to go with for winter on steel wheels. The problem is that I'm having a hell of a time locating 17" steelies. Link to comment Share on other sites More sharing options...
badfish11 Posted October 2, 2006 Share Posted October 2, 2006 What would you do in this situation? I'm really leaning toward new 17x7.5 wheels and 225/45-17s for the winter and then a new set for summer. This will give me the best and the most options when it comes time for replacement tires. Specification Sidewall Radius Diameter Circumference Revs/Mile Difference215/45-18 3.8in 12.8in 25.6in 80.5in 787 0.0%215/50-17 4.2in 12.7in 25.5in 80.0in 792 -0.6% It seems that the 215/50/17 is a near match, only off by .6% http://www.miata.net/garage/tirecalc.html Link to comment Share on other sites More sharing options...
SubiGT Posted October 12, 2006 Share Posted October 12, 2006 My LGT speedo reads low compared to my GPS groundspeed with the stockers. My 18x7.5 with 225/40-18's reads about dead on with GPS. Go figure. Many Shuvs and Zuuls knew what it was to be roasted in the depths of the Slor that day, I can tell you! Link to comment Share on other sites More sharing options...
rougeben83 Posted October 12, 2006 Share Posted October 12, 2006 FYI, most factory speedo calibrations aren't *really* accurate to begin with, so you have some play in choosing your tire sizes depending on what you want (+ rim diameter, tire width, etc.) - I think about +/-5% is probably the most I'd go from the stock wheel diameter. Link to comment Share on other sites More sharing options...
fweasel Posted October 12, 2006 Share Posted October 12, 2006 If I remember correctly, the ECU has a setting for both 18" and 17" wheel sizes, something the dealer programmer could change. Not sure if they would however. ignore him, he'll go away. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.