11-12-2013, 11:53 PM | #1 |
Drives: A White Car Join Date: Dec 2012
Location: Canada
Posts: 342
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Wheel / Tire Size and Gearing Question
I'm not super experienced with running a wheel / tire combo that results in a different size than stock, but when I saw the Z/28 come out on those 19s I knew I wanted something like that, now I recognize I won't be able to run a 305 in the front as the fenders aren't wide enough, but I was looking at running a 35 aspect ratio tire on 19s and was wondering if by changing my gearing this would correct for the fact the overall wheel / tire diameter would be so much smaller? Or am I completely looking in the wrong place? Any feedback would be very much appreciated, thank you!
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11-13-2013, 11:21 PM | #2 |
Quit being a pu$$y
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Smaller tire will give you more gearing. More gearing is better for our fat cars.
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11-14-2013, 09:49 PM | #3 |
Drives: A White Car Join Date: Dec 2012
Location: Canada
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Thanks, I see you went with 30 aspect ratio on 18s and then 40s on 18s, except with less wide tires, do you think 30 all around with 285 up front and 305 or 315 in the rear will work well? Or should I go 35 / 30 front to rear?
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"From ABS shudder that came on surprisingly early in the lousy brake pedal's travel to a looser rear end than Kim Kardashian"
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11-14-2013, 10:24 PM | #4 |
Drives: 2012 1SS Black with white rally str Join Date: Jul 2011
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I am running 19X10 with 285/40 all the way around. The tire is only about 3/4 of an inch shorter than stock, but the wheel/tire weighs about 12 lbs less per wheel and that makes the car quicker. I love the setup with the taller sidewall too.
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11-14-2013, 11:22 PM | #5 |
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I think you may be making the same mistake that a lot of people make. The aspect ratio is not a size but a ratio. It is a percentage of the tire's width. So a 35 series 315 tire is the same height as a 40 series 275 tire. Honestly I am not a fan of staggered set ups for street use. I also like to run the absolute lightest set up. My 18x10 with 285/40 all the way around are 50 lbs lighter than stock.
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11-15-2013, 01:22 PM | #6 |
Drives: 2011 Camaro SS L99 Join Date: Jan 2012
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Here's my take on it, which may be wrong, since I've been wrong before. The diameter of the tire has nothing to do with gearing or torque. The only thing that can change the gearing of a driveline are the ratios of the transmission gears and rear end gear. What is changed by varying the tire diameter is the pounds of thrust where the rubber meets the road. An example would be a car that makes 400 ft-lbs of torque at the rear axle with a 24" diameter tire. Since you have a 1 foot moment arm you end up with 400 lbs of thrust. If you shorten or lengthen that moment arm the thrust will go up or down proportionately. If your tire diameter is too small you run the risk of more thrust than the friction of the surfaces can hold and you get wheel spin. This can be overcome by a larger diameter tire to lower thrust or a wider tire to increase the friction surface. Of course, each track and day is going to vary in friction factor, and ideally you want to look for a combination that dead hooks in all situations. There are a lot of other factors, such as percentage of rubber contacting the track (i.e. a treaded tire vs a slick), rubber compound, sidewall height and stiffness, etc, which come into play. That's way it's a lot of of trial and error to find the right combo for your car. IMHO, from a physics standpoint, the notion that tire diameter changes gearing/torque is not accurate.
Last edited by jbrown13; 11-15-2013 at 01:36 PM. |
11-15-2013, 01:39 PM | #7 |
Drives: 11 Seconds or Faster Join Date: May 2012
Location: Arvada, Colorado
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Diameter changes effective gearing, and physics backs that up.
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11-15-2013, 09:15 PM | #8 |
Drives: 2011 Camaro SS L99 Join Date: Jan 2012
Location: Perry, GA
Posts: 553
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The key word in your statement is effective, which is subjective, which physics does not back up. Show me the textbook and formula backing up your statement. You can't change gearing without changing gears, just not possible in the real world. The only thing that tire diameter affects (not effects) is thrust. Does thrust change what your mind senses, yes, but it is not a gear change. If this is true why are so many people changing out their rear gears and why aren't purpose built drag cars running tiny wheels?
Here are a couple of links re rear (drive) tire/wheel diameter changes: http://www.hipermath.com/cars/rear_tire_diameter http://books.google.com/books?id=NNW...matics&f=false http://www.nightrider.com/biketech/c...mulas_page.htm |
11-16-2013, 12:34 AM | #9 | |
Drives: A White Car Join Date: Dec 2012
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Quote:
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"From ABS shudder that came on surprisingly early in the lousy brake pedal's travel to a looser rear end than Kim Kardashian"
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11-16-2013, 12:47 PM | #10 | ||
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Quote:
Quote:
The 29" tire car would be going about 180 mph and the 26" tire car would be going about 162 mph. This is the same effect as swapping from a 3.42 gear to a 3.80 gear
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11-16-2013, 04:35 PM | #11 | |
Drives: 2011 Camaro SS L99 Join Date: Jan 2012
Location: Perry, GA
Posts: 553
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