Guest lee_240z Posted September 29, 2006 Share Posted September 29, 2006 Just something to get annoyed about... Does having bigger wheels give you more speed. Think about. If the wheels turns at the same rate, a bigger wheel will give you a higher velocity. velocity = w(omega) radius = rad/s But i guess it does depend on traction too. Speaking about traction, what type of tires are best for it? Quote Link to comment Share on other sites More sharing options...
v8dats Posted September 29, 2006 Share Posted September 29, 2006 sticky ones Quote Link to comment Share on other sites More sharing options...
Duke Posted September 29, 2006 Share Posted September 29, 2006 Bigger wheels (taller) is like changing your gearing. You theorhetically have a higher top end as long as your HP can overcome the additional resistance (drag) at speed. Quote Link to comment Share on other sites More sharing options...
Guest Crispy Chicken Posted September 29, 2006 Share Posted September 29, 2006 Just something to get annoyed about... Does having bigger wheels give you more speed. Think about. If the wheels turns at the same rate, a bigger wheel will give you a higher velocity. velocity = w(omega) radius = rad/s But i guess it does depend on traction too. Speaking about traction, what type of tires are best for it? This is true, but you'll have less torque. As the engine becomes more mechanically disadvantaged. Derek Quote Link to comment Share on other sites More sharing options...
Duke Posted September 29, 2006 Share Posted September 29, 2006 where Fd is the force of drag,ρ is the density of the fluid (Note that for the earth's atmosphere, the density can be found using the barometric formula),v is the velocity of the object relative to the fluid,A is the reference area, andCd is the drag coefficient (constant, e.g. 0.25 to 0.45 for a car). Because drag increases with the squared velocity, it means it basically gets harder and harder to go faster. Ie. for each unit increase in the velocity of the vehicle in any given time interval, there is a increase in both the total mass and the velocity of air acting on the car. Thus a nonlinear increasing power curve requirement. On the acceleration side, increased tire diameter means an increase in reciprocating mass, requiring more force to overcome inertia. Quote Link to comment Share on other sites More sharing options...
Guest lee_240z Posted September 29, 2006 Share Posted September 29, 2006 So what is the most ideal size for wheels? Also, I have seen many sport cars with a bigger rear wheel, is this just for looks or can it actually make a difference? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted September 29, 2006 Share Posted September 29, 2006 What are you going to do with the car? If you're drag racing you'll want a larger wheel in the back. If you're just driving on the street, you'll want close to the same or the same size tires front and back. IMHO the 225/50/15 is the perfect size tire for a street Z. Fits under stock fenders with stock suspension and does the job just fine. Get anything wider and you'll start having to roll fenders or go to coilovers, flare the car, etc. Get anything taller and you'll have issues with getting the car low enough to "look right". You'll end up severely compromising the suspension geometry and available travel unless you do some pretty intense modifications to fix these issues. Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted September 29, 2006 Share Posted September 29, 2006 On the acceleration side, increased tire diameter means an increase in reciprocating mass, requiring more force to overcome inertia. Not necessarily. You could go from a 20" wheel with 275/35 tires to say a 15" wheel with 275/60 tires and I guarantee you that the weight of the wheel and tire will be a lot lower with the smaller wheel/taller tire. The diameter would be .4" larger. The car wouldn't have as good steering response, would feel mushier in corners, but would ride a lot better and get better gas mileage in stop and go driving - while accelerating quicker. The reduction in rotational inertia aids in acceleration. Gas mileage improves because (assuming acceleration at the same rate) you don't have your foot in the throttle as much with the smaller wheel. Ride is self explanatory. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted September 29, 2006 Share Posted September 29, 2006 Not necessarily. You could go from a 20" wheel with 275/35 tires to say a 15" wheel with 275/60 tires and I guarantee you that the weight of the wheel and tire will be a lot lower than with the smaller wheel/taller tire. The diameter would be .4" larger. You've got this backwards I think. Rims weigh more than tires. Aluminum weighs more than rubber. Same diameter for same diameter the one with more tire weighs a LOT less, unless you're talking about super high dollar racing magnesium rims. Quote Link to comment Share on other sites More sharing options...
Duke Posted September 30, 2006 Share Posted September 30, 2006 The total weight of the wheel tire combo matters to suspension reponsiveness. (unsprung weight.) Less is better. The distribution of weight in relation to the center of the hub is the reciprocating mass. Closer in is better. This has an effect on acceleration. Dragsters run big ass tires because they have around 9 billion hp and 7 billion foot pounds of torque (well, something like that...) so they can afford it. The taller your tires the more force needs to be put through the system to turns them and overcome the inertia. The drive line needs to be more robust and so forth. Think of a Seesaw, if you shift the weight to the center it takes less force to counter it. (on a seesaw it is gravitational force obviously) That's why you see parents sitting close to the fulcrum (center) of the seesaw with their kids way out on the end. You tire is like a onesided seesaw with the drive force coming from the center. That being said I think the original question was about topend speed, not acceleration, so the short answer is that adding taller tires is like shifting into a higher gear theorhetically a higher top speed if you can overcome the drag. For the record, the polymer carbon combo in most tires isn't terribly less dense than aluminium, Some alloy are heavier, some are lighter. They make low density tire compounds as well, but they wear out faster. The design and appropriateness of the tire rim combo is what is important and that depends on what type of racing, ie side loading vs acceration etc. etc. etc. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted September 30, 2006 Share Posted September 30, 2006 For the record, the polymer carbon combo in most tires isn't terribly less dense than aluminium, Some alloy are heavier, some are lighter. They make low density tire compounds as well, but they wear out faster. The design and appropriateness of the tire rim combo is what is important and that depends on what type of racing, ie side loading vs acceration etc. etc. etc. All I can tell you is I've changed quite a few tires in my life, and the general rule is that the larger the wheel, the heavier the thing is going to be. Ever changed a 20" rim back to back with a 16" rim on a truck? I have, and although they might both have a 29" diameter the the 20" combo is heavier by a good 15-20 lbs. All this plus size stuff is good to a point, but there is a point at which, like you say, the inertia from the weight of the larger wheel is a detriment to the acceleration and handling of the car. Rotational inertia is the worst kind to have, so putting big blingy wheels on a Z is about my least favorite modification. And again, even if the wheels are light, the RIM is larger in diameter, so a 15" wheel and tire combo that weighs 40 lbs will have less inertia than a 18" wheel and tire combo that is the SAME diameter. There's no getting around that. Quote Link to comment Share on other sites More sharing options...
Duke Posted September 30, 2006 Share Posted September 30, 2006 Jmor, My comment on the design and appropriateness of the tire rim combo was in support of your premise that the rim and tire combo with the smaller rim often has less total material, rubber or aluminium. Basically because the structure of the tire is a balloon relying on tensile strength so less material for total defined (controlled) volume. The reason to go for larger rims is for sidewall support and less flex,,,da da da,etc. etc., better handling. Go with a carbon fiber rim and you're golden, as long as your wallet is golden as well. Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted October 1, 2006 Share Posted October 1, 2006 I took out the "than" in my statement, so it now reads correctly - thanks. Got in a hurry. Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted October 1, 2006 Share Posted October 1, 2006 After reading this thread, I've decided to put 10 inch carbon fiber rims on my Z:mrgreen: Just KIDDING... this is good info!! Quote Link to comment Share on other sites More sharing options...
Guest Crispy Chicken Posted October 1, 2006 Share Posted October 1, 2006 I was going to say!! I just ordered some 13 inch wire daytons for my Z. You would have got me beat.. Derek Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted October 1, 2006 Share Posted October 1, 2006 Heh, heh... yeah both in speed AND size:wink: I was going to say!! I just ordered some 13 inch wire daytons for my Z. You would have got me beat.. Derek Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 1, 2006 Share Posted October 1, 2006 Hehe, yeah, Daytons... that's the wrong kind of 13's there Crispy. Don't kid yourself and think that you'd never see a fast Z with 13's on it though... I know that I'm on the losing side of this argument. Always have been. I think I was getting a little defensive early on in this post too, sorry about that Duke and Brad Man. But here's the point I was trying to make: look at the ANGLE of BRAAP's rear control arms, and look at how LOW the body of the car is. Compare that to Terry's car, where he just did this modification: http://forums.hybridz.org/showthread.php?t=114994 just to get the roll center above ground again. Don't get me wrong, Terry is a SMART guy, but he's also the ONLY one that I know of who has gone to the trouble to "fix" the roll center issue caused by running the bigger wheels and lowering the car enough to make it "look right". If you're going to run big wheels and you want your car to be REALLY fast, like on the road course or autox track fast, you're going to need to do a lot of little things to get it there. I've got LOTS of mods to fix roll center on my car which will run 23.5" tall tires on 15" rims. If you just want to slap big wheels on and take pictures and impress your friends with how huge your wheels are, or if you're only concerned about going in a straight line then have at it. Most, nearly all of the guys with the huge wheels just slap them on and run it. It's about looks more than about speed. Nothing looks slower to me than a Z with 10" of ground clearance, no suspension travel, and a wheel well stuffed full of a 60 lb combo of 18" rims with 30 series tires. Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted October 1, 2006 Share Posted October 1, 2006 Heh, heh... I'd like to see that guy TRY to burn-out those tires. Then again... if he can... WATCH OUT:eek: Hehe, yeah, Daytons... Quote Link to comment Share on other sites More sharing options...
Duke Posted October 1, 2006 Share Posted October 1, 2006 Jmor, Great post. It's right on the money about approaching it from a total systems standpoint. That link to Terry's car has really got me thinking. On a related note, a lot of people lower American muscle cars by adding drop spindles. It's a bit of a shortcut for lowering the car or adding taller wheels - hadn't seen that approach in the Z world. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 1, 2006 Share Posted October 1, 2006 A drop spindle would move the spindle closer to the top of the strut. Terry's mod is more like the "bumpsteer" spacers we use in the front. It doesn't change the position of the spindle, only moves the control arm down. There is another guy, JAMIE T, who really did something similar to a drop spindle. I looked and couldn't find the thread with the pics, but he was using Z32 spindles, and he made his own strut housing which the Z32 spindlle bolted onto. Very trick setup, but I seem to remember that he gave up on his project, or at least shelved it long term. Quote Link to comment Share on other sites More sharing options...
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