blackinches Posted January 1, 2008 Share Posted January 1, 2008 does switching to 18" wheels affect the odometer of the car? it seems like the larger diameter of the wheels is throwing off the odometer, and shows trips being shorter than they are. does anybody know how much it throws off the odo and if its something that can be fixed? on a side note is the weight listed on tire rack for the oz ultraleggeras of 18.4 lbs accurate for the 18x8? and does anybody know how much they weigh with tires? thanks in advance. Link to comment Share on other sites More sharing options...
ultimakf7 Posted January 1, 2008 Share Posted January 1, 2008 Depends on the actaul tire size. I do know the Spec B rims and stock tire size (215/45/18) is approx. 1" larger than the LGT stock rims (215/45/17). Link to comment Share on other sites More sharing options...
bgray Posted January 1, 2008 Share Posted January 1, 2008 rims have no effect..but ur tire size does Link to comment Share on other sites More sharing options...
blackinches Posted January 1, 2008 Author Share Posted January 1, 2008 if i were using 225/40/18? Link to comment Share on other sites More sharing options...
one69chev Posted January 1, 2008 Share Posted January 1, 2008 2 important factors are the tire's overall diameter and its revolutions per mile. keeping these 2 things as close to stock spec is the best way to eliminate any odometer shenanigans..... Link to comment Share on other sites More sharing options...
bgray Posted January 1, 2008 Share Posted January 1, 2008 this Java based site is a good tool...shows with pictures...so its easy keep overall dimensions within .4" and you will retain mostly stock readings and ABS control Link to comment Share on other sites More sharing options...
Brady Posted January 2, 2008 Share Posted January 2, 2008 True that checking revolutions per mile is the most accurate way to go. The dimensions on a tire really are just sort of a general indication as several of us have noted in the past that some 225 series tires, for example, are more equal than others when it comes to width. So a tire calculator will get you close, but checking revs/mile will tell you for real how much it will change. Link to comment Share on other sites More sharing options...
Devin Posted January 2, 2008 Share Posted January 2, 2008 I did just that.... I calibrated the speedo with my gps. The GPS showed I was 1.5mph slower than the speedo showed. I went to 225/40/18 from my stock 17's on my 05 Leggy. After the switch, the speedo and GPS were both on the money. I know GPS info isn't exact, but I calibrated 60mph for 60 sec and came up with exactly 1 mile on the Odo. Hope that helps! Link to comment Share on other sites More sharing options...
Knight705 Posted January 2, 2008 Share Posted January 2, 2008 I did just that.... I calibrated the speedo with my gps. The GPS showed I was 1.5mph slower than the speedo showed. I went to 225/40/18 from my stock 17's on my 05 Leggy. After the switch, the speedo and GPS were both on the money. I know GPS info isn't exact, but I calibrated 60mph for 60 sec and came up with exactly 1 mile on the Odo. Hope that helps! but aren't the speedo's off by default from factory? like it shows u going faster than u really are? Link to comment Share on other sites More sharing options...
Devin Posted January 2, 2008 Share Posted January 2, 2008 Yeah bro, that was my point! Mine was off by 1.5 mph. Switched to a larger rim/tire size from a smaller rim and it affected my speedo readout that way. Link to comment Share on other sites More sharing options...
Spec B Posted January 2, 2008 Share Posted January 2, 2008 I went from 215/45 18's with stock rims to 225/40 18's with aftermarket rims..speedo is a little fast but I never compared it to the NAVI. Link to comment Share on other sites More sharing options...
sactojesse Posted January 2, 2008 Share Posted January 2, 2008 I did just that.... I calibrated the speedo with my gps. The GPS showed I was 1.5mph slower than the speedo showed. I went to 225/40/18 from my stock 17's on my 05 Leggy. After the switch, the speedo and GPS were both on the money. I know GPS info isn't exact, but I calibrated 60mph for 60 sec and came up with exactly 1 mile on the Odo. Hope that helps! That sounds about right. The rolling diameter of a 225/40R18 is 25.1 inches versus 24.6 inches for the stock 215/45R17s. That's roughly a 2% increase in rolling diameter and a corresponding 2% (1.2 mph) reduction in your speedometer reading at 60 mph. Link to comment Share on other sites More sharing options...
Brady Posted January 3, 2008 Share Posted January 3, 2008 Also agreed. By going to a 225/45/17 I seem to be right on the money too (also about 2%) so I figure going to a 225/50/17 would make the speedometer read slow compared to real speed. Link to comment Share on other sites More sharing options...
sactojesse Posted January 3, 2008 Share Posted January 3, 2008 Also agreed. By going to a 225/45/17 I seem to be right on the money too (also about 5%) so I figure going to a 225/50/17 would make the speedometer read slow compared to real speed. 225/45R17 = 25.0 inches rolling diameter, a 1.6% increase over the 24.6-inch diameter stock 215/45R17s and corresponding 1.6% decrease in speedo reading. 225/50R17= 25.9 inches, a 5% increase in diameter and corresponding 5% decrease in speedo reading. IMO, the best size is 235/40R17, which has a nearly stock 24.4 inch diameter, but it would require 17x8 rims. Link to comment Share on other sites More sharing options...
Brady Posted January 3, 2008 Share Posted January 3, 2008 that was a typo ... I meant to say 2% ... but I used the 10 key on the right and hit the 5 above the 2 ... going to edit now. But for speedo accuracy, the 225/45/17 seems to be the best combo. I've found my speedo to be much more accurate on my summer rubber (225/45/17 RE-050 PP). Link to comment Share on other sites More sharing options...
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