No 18 inch wheel eveyone e-mail ford and scream

Discussion in '2005 - 2009 Specific Tech' started by 2005muzzy, May 20, 2004.

  1. question... how much do you think an upgrade to the 18 inch fanblades would cost, when they become available? im expecting the upgrade to the concept wheels to cost around 400 dollars, so i was wondering how much more yall would think it would cost to upgrade to the 18 fanblades when they become available.
     
  2. I'm surprised no one has mentioned this yet...
    Not only does a larger wheel add more unsprung weight, but it can also rob RWHP (even if the larger wheel weighs less than stock).

    I can't remember all the details, but if you watch Sports Car Revolution, you would know what I'm talking about.

    I think it has something to do with a larger wheel carrying more weight farther from the center of the hub. In other words, it is easier [for the engine] to turn a smaller diameter wheel than a larger one.
     
  3. As luck would have it... the Speed channel is airing that very episode that I was talking about. According to my Dish Network guide, it will be on at 7:30 pm EDT on Tuesday and again on Friday at 10:30 am EDT.
     
  4. Amen! Brother! :nice:
     
  5. exactly. a larger wheel has a hihger rotational inertia.

    anyway...who really gives a damn what it comes with anyway? I wish they would offer the GT with the base mustang wheels, or even a set of staped steel rims w/hubcaps, so I can save a grand or two on the option and put that money torard some aftermarket rims.
     
  6. Wheels are getting too big these days. What ever happened to big ol fat tires? Now the tires are like an inch thick..
     
  7. I know... 15" rims with tall sidewall tires with raised white lettering looks pretty damn cool on old muslce cars, so maybe it iwll look good on the '05 too. Also, with thicker tires, you dont have to worry about destroying your rims on a tiny litle pothole.
     
  8. exactly, you're talking about rotational intertia. you can get the rotational inertia of any rotating object by looking at every little bit of mass and its distance from the axis of rotation, so basically its a calculus calculation. For a hollow cylinder, I=MR^2, for a solid cylinder its 1/2*MR^2, probably the best approximation for a wheel is the hollow cylinder, since most of the mass is at the rim right? anyways, it doesn't matter cause the 1/2 is just a constant factor that cancels out if your comparing two situations.
    You prolly all know F=ma, force equals mass times acceleration. Well its pretty much the same with rotation, torque equals rotational inertia times rotational acceleration. Or rotational accel = torque/inertia. If you increase the radius of the rim from 17 to 18, a factor of 1.06, you increase the inertia by a factor of 1.12 since the inertia is proportional to the square of the radius. That means you decrease your acceleration by a factor of 1.12, since the rotational acceleration is inversely proportional to the inertia. And since the linear acceleration of your car is directly related to the rotational acceleration of your wheels, if you were hittin 60 in five seconds, its gonna take you 5.6 seconds now.
    Of course this is an oversimplification, but it gives you an idea of how big a role the radius of your wheels plays in straight line acceleration.
     
  9. Wow! That's a really good explanation.

    You should have seen Sean Hyland in that episode of Sports Car Revolution...it took him awhile to figure out why they lost RWHP in their Acura car after plus-sizing the wheels
     


  10. just a quick FYI: plus sizing wheels shouldn't have any effect on ride height. the idea is to keep the same overall tire height, but with less sidewall and more rim. cool?

    later
    steve
     
  11. The new mustang will be offered with 18" rims a year after lauch (or possibly earlier) with a set of 255 45R18 tires.

    This has been confirmed numourous times and even in a video of the pony drive (announcer introducing the mustang confirms it).
     
  12. I totally agree. I never understood why there's so much gap. All I could come up with is that drag racers need a huge gap in the back for slicks. :shrug: I recently installed Ford C springs on my Mustang and I thought, yeah, that's better, not too much and not too little. Every once in awhile I'll glance at a Stang that hasn't been lowered at all and I'll think, Jeez, what a difference 1.5" makes...
     
  13. Amen Brother - I work for a tire supplier and can list several considerations that Team Mustang engineers have to grapple with to get 18" wheels and tires into production:

    1. Road loads go up dramatically with 18" wheels and tires. This would require them to re-validate all durability loads into chassis components and body structure.

    2. Weight of 18" wheels and tires may push the car into the next weight class (ETWC). This will require them to re-certify the car for emissions, and fuel economy. This will affect FE labels and CAFE. In addition, it would double the number of prototypes they need to do the certification testing.

    3. TREAD Act starts to go into effect this year and next year most cars will be required to have tire pressure monitoring system (TPMS). This will drive different wheels with unique cross-section and wheel drop to package the TPMS RF sensors. They may have decided not to tool up and 18" wheel and then have to do a new one next year for TPMS.

    4. 18" wheels and tires will have higher rolling resistance which may push the car over gas guzzler threshold.

    5. 18" wheels and tires may require unique suspension, steering, ABS and TCS tunings due to changes in unsprung mass, tractive properties of the tires, etc... Again this will require proper validation and incremental prototypes.

    6. Last but not least, I am told that Mazda 6 and Mustang goes down the same final assembly line at AAI. They may not have enough rack space, tire mounting equipment, tire balancing equipment to handle all combinations of Mazda and current Mustang wheels. Lead time for new assembly tooling may play a role in timing of 18" wheels and tires.

    Other than that it should be a no brainer for them to introduce the 18" wheels and tires and make a killing!
     
  14. Who said "the Mustang ain't supposed to handle good"??? Maybe some on this board, but certainly not I. I'm one saying it should handle even better - with IRS. And I'm not saying what belongs on your Mustang... I said the aftermarket can supply. I said don't screw them all up.
     
  15. You've obviously never been to a track where Lightnings play. They can hold their own.

    FYI
    '04 Lightning weight distribution - 57% Front 43% Rear
    '04 Cobra weight distribution - 57% Front 43% Rear

    From the SVT website.
     
  16. Just to let you guys know, in that little estimation i did about the effect of larger rims on acceleration, i made a big mistake. That kind of a difference in acceleration would be observed if the mass of the car was negligible. Like say the work required to linearly accelerate the car as a whole was nothing compared to the work required to accelerate the spinning of the wheels. So if you were comparing two super lightweight chassis with super lightweight engines, one with 17' wheels and the other with 18', then you'd see something close to that difference in 0-60 times. It wouldn't be too hard to actually figure out the difference for real car though. I'll do it some time later though, i'll post again when i've figured it out.
     
  17. redfireGT, THANK YOU for illustrating the "big picture". The armchair quarterbacking seems to have simmered down to a reasonable level.
     
  18. I had no idea the Cobra's were such great track cars. From what I have heard. They suffer some oil issues when trying endurance racing. I do know that Kenny Brown has a track car. But there are not a lot of Cobra's running road races.
     
  19. Aesthetically, I do like 18's. They look really good on the show cars that have been circulating at the auto shows. That being said, I have the Bullitt's on my current GT and I like the look. I really don't have an issue settling for a 17 inch rim.

    I don't even have an issue with losing 10mm of tire width.

    My problem is the profile. How can they offer this car with a 55 profile tire? That's a pretty big change from the 245/45/17 I have now. I don't get it. If 18's aren't available from the factory, I won't even opt for the 17's.

    I'll drive the car of the lot with steelies and drive right to my local tire shop. :D