JMortensen Posted March 8, 2010 Share Posted March 8, 2010 I don’t mean proving on paper, I mean real world proof. I agree with some of the specific data that’s been posted, but I don’t think everything is being taken into account. The only results that really mean anything comes when the rubber meets the road – literally. There's always something else that could screw up the experiment. Like the gearing issue on the BMW. Doing it on paper removes the other variables. I'm sure it's possible to quantify the extra torque that is used spinning a set of larger rims up, and also that it is possible to determine in some unit (I guess that would be torque too) how much more braking energy is consumed. Link to comment Share on other sites More sharing options...
B00STDZ Posted March 9, 2010 Share Posted March 9, 2010 What a highly biased load of bologna. Why do people that don’t want to run larger rims feel it’s necessary to continually bag on people that do? Clearly there are some issues regarding larger diameter wheels, but there are some benefits as well. The next thing you know you large wheel haters are going to tell me that large diameter wheels are going to create a block hole that will ultimately kill everyone on the planet. You haven’t even proven that smaller diameter wheels = better performance and you deliberately discount any evidence that doesn’t conform with your expectations. This isn’t a conspiracy and I don’t believe it’s all about big corporate profits. I would like to see real world data that specifically supports the theories about larger diameter wheels causing performance issues such as the experiment that johnc described in an earlier post. By this I mean something realistic like comparing 17s to 18s on the same vehicle. Amen! When real world expirementation are avoided 99% of the time it is not true. But I will say that small rims and bigger sidewalls do have a gripping advantage... for the straight line or drag strip. As for all that sidewall being more useful in high speed autoX.... Prove it. I think this argument is very silly because 18's are NOT THAT BIG! Hahaha. Everyone here acts like we are justifying the performance of 20+" rims! Haha! Link to comment Share on other sites More sharing options...
micky Posted March 9, 2010 Share Posted March 9, 2010 Im building a 240z stroker 3.1L I would like some input to see if running 18"rims is too much for this engine.I wanting to go widebody with 18x12 in the rear 18x10 in front. hi no problems using 18" im using an 18x10 on ZG flares looks awsome Link to comment Share on other sites More sharing options...
Bartman Posted March 10, 2010 Share Posted March 10, 2010 As far as I know no one that’s been posting to this thread is an automotive engineer including myself, and no - understanding PMOI or reading a couple of suspension books doesn’t make you one. I think there’s much more at play here other that just PMOI therefore you can’t just use that argument to prove larger diameter wheels are a detriment to performance. If you don’t think other factors are involved you’re either ignorant or just closed-minded and no amount of evidence contrary to your personal beliefs is ever going to change your perceptions. For those of you that think larger diameter wheels are all about a big conspiracy or just about profits, I can’t help you. Also for those of you that think that members of this site that run or talk about running 18s are going to ruin this site and the whole Z community and prevent the tires you want from being made, I can’t help you either (although an admin can ban me from this site and/or delete any sacrilegious posts regarding wheels larger than 14 inches or so). The reality is that larger diameter wheels are out there and more and more manufacturers are using them for whatever reasons, and more and more people are going to use them on their vehicles when they want to make a change. It’s painfully obvious that some of you are against this trend and that’s your prerogative – but don’t try to disparage everyone else that does it. No one is forcing you to jump in every thread that discusses large diameter wheels. I don’t know for a fact on my vehicle if performance is increased or not, but I would be interested in this information. I had my car on a dyno about a little over a week ago and my torque was down with an increase in horsepower from my previous dyno numbers. Of course there could be other factors other than switching from 17x7s to 18x9.5s, but it could be a significant factor (other potential issues include that two different brand dyno’s, and different atmospheric conditions). How does this translate to real world performance I don’t know, and it probably varies based on straight line performance, drifting, small track, large track, autocross, grocery getting, canyon carving, etc. I think that the only real way to know is to test both combinations in each scenario and then to decipher the data afterwards. Until some data form this type of testing is produced everything else is pure conjecture and most likely heavily tainted based on predefined personal preferences and beliefs. Link to comment Share on other sites More sharing options...
Leon Posted March 10, 2010 Share Posted March 10, 2010 I got my information from an F1 senior engineer. I guess that doesn't count... Link to comment Share on other sites More sharing options...
rags Posted March 10, 2010 Share Posted March 10, 2010 The way I see it is, if your car doesn't have bumpers, marker lights, interior panels, side glass, radio, heat or AC, a passenger seat, or license plates, then by all means read through all 5 pages of this post and comment. But if your car is street legal, the performance that could be sapped from using 18 inch wheels, or any size bigger than 14", is equivalent to a bag of beans. Joe Link to comment Share on other sites More sharing options...
JMortensen Posted March 10, 2010 Share Posted March 10, 2010 The way I see it is, if your car doesn't have bumpers, marker lights, interior panels, side glass, radio, heat or AC, a passenger seat, or license plates, then by all means read through all 5 pages of this post and comment. But if your car is street legal, the performance that could be sapped from using 18 inch wheels, or any size bigger than 14", is equivalent to a bag of beans. I disagree with you Joe. Why bother modifying the car at all if the effect of the modification doesn't matter or isn't worthwhile? Why do people here install light flywheels in their street cars? If you've ever been in a car with one, it CLEARLY matters in that case. Reducing rotating mass makes a difference, even in a street car. Link to comment Share on other sites More sharing options...
Bartman Posted March 10, 2010 Share Posted March 10, 2010 The way I see it is, if your car doesn't have bumpers, marker lights, interior panels, side glass, radio, heat or AC, a passenger seat, or license plates, then by all means read through all 5 pages of this post and comment. But if your car is street legal, the performance that could be sapped from using 18 inch wheels, or any size bigger than 14", is equivalent to a bag of beans. Joe There's even a track car on this site that doesn't have all the items iems you listed...and runs 18s!http://forums.hybridz.org/index.php?/topic/52168-my-new-wheels-arrived/ http://forums.hybridz.org/index.php?/topic/63250-mike-kellys-zcar-project/ Link to comment Share on other sites More sharing options...
rags Posted March 10, 2010 Share Posted March 10, 2010 (edited) Jon, I understand what you are saying but I'm still going to stick to my statement. As you know, I do have a car that I built with weight in mind (yellow one) and agree that rotational mass does effect performance. My yellow car is able to outrun cars with much more hp and I contribute it mostly to unsprung weight. The LS1 car was built totally differently. it has over 400 whp but I am looking for more of a street first track second attitude. I think the 18's fit the bill nicely. I don't think you can just look at modifying our cars for track/performance purposes. That is something that would have never come out of my mouth 10 years ago when I first joined this site but my body has changed and I now know I can't have everything in one 40 year old car. My post was meant to read everyone has an opinion and each opinion has a place. Build an all out track car like yours using 40 year old suspension designed around 14 inch wheels and tires probably isn't the place for rim sizes of +4 inches if you want all out performance. But if you aren't looking for the "best" handling car, want many different wheels and tires to choose from and willing to take some crap from people who don't like them, then maybe larger wheels are for you. Bartman, Mikes car?? By the time that car hits the track there won't be any 18's left. Every new car will be rolling on 28's Joe Edited March 10, 2010 by rags Link to comment Share on other sites More sharing options...
(goldfish) Posted March 10, 2010 Share Posted March 10, 2010 Why does every think just because we say "large wheels hurt your performance" that what we really mean is "your dumb for having large wheels"? The other main factor in "real world" tests other than PMOI is the tire it's self, and that is to hard to make a constant in real world testing. Even in JohnC's test, if they were the same model and brand, they could have different compounds affecting traction. I like to think HybridZ runs on facts. IF you have 18's because you like the look, good. If you have them because that is were the selection of tires you want are, fine. Just call it what it is. Link to comment Share on other sites More sharing options...
Daeron Posted March 11, 2010 Share Posted March 11, 2010 (edited) Why does every think just because we say "large wheels hurt your performance" that what we really mean is "your dumb for having large wheels"? ...... .....I like to think HybridZ runs on facts. IF you have 18's because you like the look, good. If you have them because that is were the selection of tires you want are, fine. Just call it what it is. Initially I posted stating my position on the subject. I made an outrageous error (inadvertently referring to diameter instead of radius) and got my stick buried in the mud here. Like he said, as much as I may whine.. I'm NOT trying to bend over the thumbs of the 18" wheel crowd; I'm just trying to explain where the old school camp is coming from. the thread had divulged into various people talking about why you have to put a body kit, or side skirts, or lower the car, or do whatever, to make the 18s "look right." Someone also came up and made a comment about needing the room for more brakes. jmortensen chimed in with factual information regarding big brake clearance and wheels all the way down to 15" (his point being, there is literally far more acreage underneath an 18 inch wheel than you could possibly neeed to fill with brakes on a Z-car.) After a few more posts mucking about in muddy technical waters, suddenly the people who like our normal-sized rims are defending our turf, and the people who like to put modern rims on the old car are trying to justify it. I'm through posting in this thread*, because it seems like each post I make is taken with too much venom. I'm complaining, yes, but only after having it dragged out to his point. My first post was an off-the-cuff joke about how 19" wheels really complemented a lightened flywheel. I wish I hadn't tried to be a comedian. *Edit: I will continue to read, in the hopes that the discussion will pan out with more good solid data. These things typically do. I guess I forgot to apologize to anyone who's buttons I may have pushed, but please keep context in mind. Edited March 11, 2010 by Daeron Link to comment Share on other sites More sharing options...
Kevin.pk Posted March 11, 2010 Share Posted March 11, 2010 to each his own Link to comment Share on other sites More sharing options...
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