confused!
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Drunken Master-7thgen Ninja
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confused! ok someone explain this to me. from what i understand, if i am running 15 inch tires, with 65 series thats stock, the spedo is fine. so IF i got 15 inch rims with 50 series tires, then my spedo will be off, AND my rpms in each gear at a certain speed will be off too...so does that mean i just made my gears shorter in a way? so my car will get faster times then with normal tires? just wondering. thanx!
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Rep Power: 288 no...only thing is number of revolutions of the tire....you're making the circumference shorter, the rpms are the crank rpms, not the tire rpms. and yes the speedo will be off, it's not noticable as the speedo is always off anyways. get a gps and you'll get accurate readings of speed.
Last edited by shroomster; May 18, 2006 at 12:35 AM.
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Rep Power: 361 yeah rpms will always read correctly as long as the sensor on the engine is right. The mph is gauged off wheel rpm and thus if you change the circumference it displays an inaccurate number.
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From: Orlando by way of Altoona, PA!!!
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Originally Posted by diskreet
yeah rpms will always read correctly as long as the sensor on the engine is right. The mph is gauged off wheel rpm and thus if you change the circumference it displays an inaccurate number.
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Rep Power: 285 i know its off the tranny on older cars, thats the only thing im familiar with.
the difference in diameter screws everything up. you speedo, and also shift points, if its an auto. i learn this in my truck the hard way
the difference in diameter screws everything up. you speedo, and also shift points, if its an auto. i learn this in my truck the hard way
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Rep Power: 361 output shaft of transmission rpm = wheel rpm.
I was just calling it at the wheels cause its easier to visualize how a difference there makes a difference in the reading.
I was just calling it at the wheels cause its easier to visualize how a difference there makes a difference in the reading.
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Drunken Master-7thgen Ninja
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Rep Power: 336 i have a manual. the big question is, will my rpms be different at different speeds? i think so. so does that mean i effectively can change how long/short a gear is?
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Rep Power: 361 Kinda if you want to look at it like that. But you need a larger change than what you mention in the first post to really see a difference.
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Drunken Master-7thgen Ninja
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Rep Power: 336 yea well, i WAS gonna get like 215/40/15s but i got told it would look stupid, and i decided to do the 50s instead. i mean its a difference alright.
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Originally Posted by dp_yz713
try the 45s . thats what i have
what size tires and wheels??? it makes all the difference... Boobies are the mans tinkertoys
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Rep Power: 285 yah i know it makes a difference, i was on goldlines, 1.75, with 17s and it had no gap. now i have no drop with the same tires on 17s. according to what i read about tire diamteters it decreases by .5". like 50 to 45 is a .5"
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From: Orlando by way of Altoona, PA!!!
Rep Power: 288 50 is still gonns be to much of a wheel gap( i mean all around not just from the bottom of fender to the top of wheel) (this space) <<sides of fender
195/60 or 205/60r15 offer the best meat, width, and wheel well gaping possible...between 1&1/2 and 2 fingers....
195/60 or 205/60r15 offer the best meat, width, and wheel well gaping possible...between 1&1/2 and 2 fingers....
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Drunken Master-7thgen Ninja
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Rep Power: 336 ok im riding stocks 185/65/15s. i have a 2 finger gap all around. and i know that the 65 in that means 65 percent of the 185. which is 120.25 width in MM.
if i get 215/50/15 which is 107.5 so the 50 series will be fine. its like 1cm difference. so 1 finger gap maybe. ill be fine.
if i get 215/50/15 which is 107.5 so the 50 series will be fine. its like 1cm difference. so 1 finger gap maybe. ill be fine.
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Originally Posted by MajinB
ok someone explain this to me. from what i understand, if i am running 15 inch tires, with 65 series thats stock, the spedo is fine. so IF i got 15 inch rims with 50 series tires, then my spedo will be off, AND my rpms in each gear at a certain speed will be off too...so does that mean i just made my gears shorter in a way? so my car will get faster times then with normal tires? just wondering. thanx!
short answer, YES. what you've done is essentially shortend the final gear ratio. its a common pratice among autocrossers and open track drivers. Just be aware that you are sacraficeing a bit of your top speed for better acceleration.
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