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blown04cobra
03-23-2006, 12:04 PM
Thinking of going to 18" wheels. Anyone know if you will lose some horsepower to rear wheels on dyno by increasing the diameter of the tires? Had several conversations with both yes and no answers regarding this. Thanks for any info anyone has.
DNeinstadt
03-23-2006, 12:11 PM
I can't see how you would LOSE power by running different wheels but I'm not a scientist type. :)

power is still output via the driveshaft using the same drivetrain loss, putting it to the ground/dyno may be affected though.

Dan
mackj66
03-23-2006, 12:14 PM
I do know that dyno numbers can fluctuate due to gear changes.

If you are so concerned with "Numbers" than just pick up a crappy pair of 17s for the rear and throw them on there only when you are on the dyno.
Kafn8td
03-23-2006, 12:54 PM
You won't "lose" HP, but 18's are generally heavier, and will change the gear ratio a small amount, which will affect dyno numbers.
yellowgt05
03-23-2006, 01:58 PM
You won't "lose" HP, but 18's are generally heavier, and will change the gear ratio a small amount, which will affect dyno numbers.


?? MY old wheels are 55x17 new 45x18 shoud be the same ratio,same hight ?
Just 1 mph on speedo at 55.
Kafn8td
03-23-2006, 02:00 PM
If it affects the sppedo at all then there is a difference right?
yellowgt05
03-23-2006, 02:14 PM
OK !!!!!!!!!!!!!!! YOU ARE RIGHT
Grenade
03-23-2006, 04:02 PM
The heavier weight will decrease usable HP a little. Weight is thyne enemy. Not easy to notice in a v-8 car however.
cobraboy325
03-24-2006, 05:02 PM
weight to diameter ratio is a huge issue. The bigger the tires the more it will take to get it started something about angular velocity something like that. Talk to the new edge guys on SVTP. they will tell you not to do it to an 01. however with something blown I cant imagine having the the takeoff problems. LOL
CB
thom1301
03-25-2006, 08:33 AM
As for the diameter and gear ratio, don't most people get a thinner tire when moving to a larger wheel to keep the overall diameter consistent?

I'm not sure how much the wheels would affect hp/trq, but I did an article for Modified Mustangs recently where an aluminum driveshaft on an '05 (22 lbs lighter) picked up 10 hp and 16 ft/lbs of torque at 3,400 rpm. Your engine has to accelerate those heavier wheels, which takes more power (or more time for a given amount of power). Plus the larger diameter of the wheel means it will take more centrifugal or centriputal (I forget) force to accelerate, even if the weight were the same (think of twirling a ball on a 6-inch string, then imagine it with a 1 foot string).

That being said, if you like the 18s better, it seems like a fair tradeoff! You could always get an aluminum driveshaft at the same time to help with the tradeoff. :salute:
Kafn8td
03-25-2006, 08:36 AM
Good info Travis! Although not directly related to inertia, here are some weights of what can come out of your car. http://users.adelphia.net/~mustang-92/Weight%20Reduction.htm
Grenade
03-25-2006, 09:45 AM
Very interesting.
thom1301
03-25-2006, 09:56 AM
Physics is cool when it relates to making your car go faster! :shiftin:
Grenade
03-25-2006, 03:01 PM
As for the diameter and gear ratio, don't most people get a thinner tire when moving to a larger wheel to keep the overall diameter consistent?

I'm not sure how much the wheels would affect hp/trq, but I did an article for Modified Mustangs recently where an aluminum driveshaft on an '05 (22 lbs lighter) picked up 10 hp and 16 ft/lbs of torque at 3,400 rpm. Your engine has to accelerate those heavier wheels, which takes more power (or more time for a given amount of power). Plus the larger diameter of the wheel means it will take more centrifugal or centriputal (I forget) force to accelerate, even if the weight were the same (think of twirling a ball on a 6-inch string, then imagine it with a 1 foot string).

That being said, if you like the 18s better, it seems like a fair tradeoff! You could always get an aluminum driveshaft at the same time to help with the tradeoff. :salute:
I just bought an Aluminum D/S. I should be in the 10's now. In the 1000ft. $ 224 Summit. Anything to help my poor little Ram-air 281 Has anybody else seen any dyno #'s, For an aluminum D/S, Vs Stock?10 hp and 16tq seems kinda high
Mark SVT
03-26-2006, 08:09 AM
Physics makes the world go round LOL
mackj66
03-26-2006, 10:33 AM
Physics makes the world go round LOL

nooooo, Bridgestone does. :haha:
Grenade
03-26-2006, 01:10 PM
I just bought an Aluminum D/S. I should be in the 10's now. In the 1000ft. $ 224 Summit. Anything to help my poor little Ram-air 281 Has anybody else seen any dyno #'s, For an aluminum D/S, Vs Stock?10 hp and 16tq seems kinda high
Any opinions on the aluminum vs stock anybody?
Kafn8td
03-26-2006, 06:43 PM
Is the stock Mach mild steel? I figured it would be aluminum.
Grenade
03-26-2006, 07:15 PM
Is the stock Mach mild steel? I figured it would be aluminum.
It's not aluminum. And It has a smaller diameter. I guess the aluminum is lighter and stronger than the stock one. What do factory Terminators have?
Kafn8td
03-26-2006, 07:19 PM
aluminium. I bet that is a decent swap. How much are they now a days?
Grenade
03-26-2006, 07:27 PM
aluminium. I bet that is a decent swap. How much are they now a days?
They used to be real cheap. They went up alot in the last two years. The best I could find was $224 at Summit. Free shipping. After that I'll have to go with a loop. I have one. but I have heard diff times on when they have to be used. I want to run 11's, so I'll prolly need it by then.