spankis Posted October 2, 2009 Report Share Posted October 2, 2009 So, this kid on 3si.org is trying to trade his 03 350z for a 98 or 99 3000gt VR-4. He posts a thread about the car he has to trade with tons of pictures, blah blah blah. Well, in the description, it says this: "The car has 79,800 miles.. but the tires are oversized causing the mileage to add up faster then it should.. It probably really only have 59,500 miles on it because of that. Needs to be calibrated." So I posted this: "Beautiful car sir, but as for the mileage discrepancy, oversized tires would actually cause your odometer to underestimate the true distance your car has traveled. This would mean the the car actually has more miles than the odometer indicates. An oversized tire travels more distance in a single rotation than a smaller, stock-sized tire. FYI." He responded with this: "Your wrong about that, the tires cause the speedo to say I'm going faster then I'm actually going. So to go 60mph I have to go 64mph on the digital speedo. Thats adding 4 miles to every 60 miles to my odometer. Ive had a Sheriff come over and test it with his radar gun. Every 60 miles I go 4 miles is added to the car... It can be calibrated, I just haven't done it. anyway, I dont want the thread blown up about that lol." I was reading this thread at around 1am, and I was tired. I figured, hey maybe I'm wrong, so I let it go at that. I noticed the thread again the next day, and thought it through again. I'm still pretty much completely certain that the kid's logic is backwards. I sent him a PM, basically further explaining what I thought to be true in great detail, and linked him to another site explaining the sizing/odometer correlation. I was very polite, never called him a retard or suggested any intentional misleading. I didn't want to shit in his for sale thread or anything. He replied with this: "that link actually shows opposite of what happens with my car. Ive had a sheriff come over and test me speeds, like I stated in my post if my speedo says 64 I'm actually going 60.. so that adds 4 miles every 60 miles. I dont know if its different with digital read speedos, but Ive had it tested. Every time I go by one of those speed checkers on the side of the road, it always shows me going slower. So the case with my car may be different I dont know, but if anyone wants to ride with me and go by a speed indicator they are more then welcome. Thanks for not posting it in the thread tho, id hate to ruin the post with petty arguments :)" ....Yea thanks bud, "petty argument", unless you're the uninformed guy buying your car..... So am I right, or am I wrong here? I should probably just drop it, but whatever. I know how most speedometers and odometers work, and by that logic I believe I'm correct, but does a 350z use some foreign system I'm not familiar with? Long post I know, but if you made it this far you probably have some time to kill Quote Link to comment Share on other sites More sharing options...
oh8sti Posted October 2, 2009 Report Share Posted October 2, 2009 god damn what size tire was he running? fuckin 34"? Kid seems like a doucher, specially drivin a 350z....what a girl car. Quote Link to comment Share on other sites More sharing options...
unfunnyryan Posted October 2, 2009 Report Share Posted October 2, 2009 Edited out: rethinking Quote Link to comment Share on other sites More sharing options...
unfunnyryan Posted October 2, 2009 Report Share Posted October 2, 2009 Your logic is correct. You don't need to increase the wheel diameter very much to increase the circumference a LOT. google turned up this, explains it quite clearly. Your tires are 10% larger than the car thinks. Therefore, you travel 10% more than your car recognizes. This has two effects: Your actual speed is 10% MORE than what your speedometer is reflecting. (When your speedometer reads 60, you are actually traveling 66) 10=11, 40=44, 100=110 etc. Your actual mileage is 10% MORE than what your odometer is reflecting. (When your odometer reads 100 miles, you have actually traveled 110) Quote Link to comment Share on other sites More sharing options...
spankis Posted October 2, 2009 Author Report Share Posted October 2, 2009 god damn what size tire was he running? fuckin 34"? Kid seems like a doucher, specially drivin a 350z....what a girl car. http://i345.photobucket.com/albums/p400/n0gamez/350z/1.jpg They're Axis 19s, not huge, but bigger than stock definitely. Your logic is correct. You don't need to increase the wheel diameter very much to increase the circumference a LOT. google turned up this, explains it quite clearly. Exactly, it just seems obvious. Seems like the kid is a gigantic retard or is intentionally misleading/hiding something. Clearly he's not trying to understand. Quote Link to comment Share on other sites More sharing options...
BloodRed Posted October 2, 2009 Report Share Posted October 2, 2009 Yeah you are correct. I have been dealing with the truck/Jeep world where lifting and bigger tires happen all the time. Quote Link to comment Share on other sites More sharing options...
Tripleskate Posted October 2, 2009 Report Share Posted October 2, 2009 smaller tires = more miles larger tires = less miles Quote Link to comment Share on other sites More sharing options...
copperhead Posted October 2, 2009 Report Share Posted October 2, 2009 Your logic is correct which reminds me, I need to get way bigger tires on the jeep, those miles are adding up WAY too fast Quote Link to comment Share on other sites More sharing options...
Guest tbutera2112 Posted October 2, 2009 Report Share Posted October 2, 2009 (edited) so how many miles would actually be on the car? 90ish? the guy said the car has less miles because of bigger tires...but everyone is saying that bigger tires is more mileage not less...but skinner said he needs bigger tires because his miles are going up too quick...now yall got me confused lol if larger tires = less miles, then the guy selling the z was correct...odo shows 70 and his car has less than that, so where is the argument? Edited October 2, 2009 by tbutera2112 Quote Link to comment Share on other sites More sharing options...
iwashmycar Posted October 2, 2009 Report Share Posted October 2, 2009 lotta low mileage Donks out there Quote Link to comment Share on other sites More sharing options...
spankis Posted October 2, 2009 Author Report Share Posted October 2, 2009 so how many miles would actually be on the car? 90ish? the guy said the car has less miles because of bigger tires...but everyone is saying that bigger tires is more mileage not less...but skinner said he needs bigger tires because his miles are going up too quick...now yall got me confused lol if larger tires = less miles, then the guy selling the z was correct...odo shows 70 and his car has less than that, so where is the argument? Larger tires = less miles shown than actually driven, not less miles driven. One rotation of the axle takes the car noticeably further distance with even a slightly larger tire. The odometer/speedometer don't know the tires on the car are a different size than stock. So, do I send a PM to the mod of the Classifieds forum or drop it? The dude does seem like a real doucher. Quote Link to comment Share on other sites More sharing options...
Guest tbutera2112 Posted October 2, 2009 Report Share Posted October 2, 2009 Larger tires = less miles shown than actually driven, not less miles driven. One rotation of the axle takes the car noticeably further distance with even a slightly larger tire. The odometer/speedometer don't know the tires on the car are a different size than stock. So, do I send a PM to the mod of the Classifieds forum or drop it? The dude does seem like a real doucher. ok thats what i thought...but you all had me confused lol Quote Link to comment Share on other sites More sharing options...
neonkiller Posted October 2, 2009 Report Share Posted October 2, 2009 Tell the kid to grow a dick. Quote Link to comment Share on other sites More sharing options...
bahd-ler Posted October 2, 2009 Report Share Posted October 2, 2009 Tell him to grow titts and then show us. Quote Link to comment Share on other sites More sharing options...
Bam Posted October 2, 2009 Report Share Posted October 2, 2009 Here's a cool link I like to reference... http://www.discounttiredirect.com/direct/brochure/info/tmpInfoTireMath.jsp Just enter in the OEM tire size first, then enter in the tire size he, or you want to run/are running and it'll tell you the difference. Also, just because he has 19" wheels on the car DOES NOT mean if has larger tires on it, the tires should be a lower profile to equal out the larger wheel size. Quote Link to comment Share on other sites More sharing options...
Bam Posted October 2, 2009 Report Share Posted October 2, 2009 Just ask him what size tire he is actually running. Stock 350z's had 225/50/17's on the front, and if he has 19" wheels on it he should be running 245/35/19 tires on the FRONT. If he is running that size, his speedo will read .27mph faster than he is going at 65mph, so not really different. 65mph vs. 64.73mph Quote Link to comment Share on other sites More sharing options...
GonneVille Posted October 2, 2009 Report Share Posted October 2, 2009 Sounds like the little douche has bigger rims, but with tiny little rubber bands on them, so the combo is smaller overall. My tires are one profile size larger than stock, and if I hold 70 on the speedo, I'm actually doing 73 or so. That's not confirmed by radar or anything, but against a stock vehicle over the course of a long drive. Quote Link to comment Share on other sites More sharing options...
copperhead Posted October 2, 2009 Report Share Posted October 2, 2009 so how many miles would actually be on the car? 90ish? the guy said the car has less miles because of bigger tires...but everyone is saying that bigger tires is more mileage not less...but skinner said he needs bigger tires because his miles are going up too quick...now yall got me confused lol if larger tires = less miles, then the guy selling the z was correct...odo shows 70 and his car has less than that, so where is the argument? Take a ping pong ball, and set it beside a basketball. roll them both five feet, and count how many revolutions it takes to travel that distance. Now think - if those were tires on a car, which one is spinning faster, which would in turn spin a speedometer faster? Quote Link to comment Share on other sites More sharing options...
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