Well finally got the 18x8 Evo5's with some 245/40/18 tires on there. the tires weigh around 25lbs a piece and the rim i think is 26lbs. Just tested it with 6.7 0-60 those are some bad numbers, i used to get just below 6 with all stock. I also have an Inejn intake with an A'Pex filter, it might be dirty/old since i bought it at 23K i think and now i have 36K but i also bout it from a previous user that already put 10K on it....

what can i do to gain my seconds back?

-IgS

 

bigger wheels. require more energy to turn.. thus become slower...
unless you get very light rims.. your car is gonna be "slower" than before..

 

OT.. let's say he got 18" or 19" that were the same exact weight as the stock 17". How does weight distribution of the rim & tire affect speed? I remember something about the weight being concentrated in the center of the wheel on stockers. Would that be slower than on bigger size, same weight rims?

 

You have to take into consideration the overall weight of the wheel, the diamter of the wheel, and the weight distribution. It all plays into inertia. The more weight on the outer portions of the wheel the more force it takes to turn the wheel.

 

the biggest factor is having a larger circumference surface area on the wheel that the engine now has to turn, not weight per say.
By getting a larger wheel you have affected the final drive/gear ratio. The engine now needs to spin more revolutions to turn the wheel once.

 

I do believe the weight has a greater effect of damping performance if it located in a further outer radius from the center... e.g. the more mass that is present in outer areas of the wheel, the slower it will be. I'm sure there's some funky math involved in computing the difference (e.g. computing how much of a diff a 25lb 19" wheel makes vs. a 25lb 17" wheel)

 

I agree 100%... just put the stocks back on when you hit the track and just look good when you're on the streets!

 

Should've spent extra for Volks.

 

Of course. You've got more rotational mass to accelerate now. Put 20"s on there and it will be even worse. Yep, the further out from the center point, the more force is required to accelerate the same amount of mass. Think of a lever. If you've got a 2 foot handle on something like a jack it requires a certain amount of force. If you triple its length and you're now 6 feet from the point, you are able to exert 3 times as much force to the jack (although, of course, you'll move the same part on the jack only 1/3 the distance). So, if the weight of two wheels is the same, but one has its weight on the outer rim, and another very close to center, the second one will be less of an issue when trying to spin up the wheel.

 

I think everyone is still caught up on the weight thing because we are assuming the larger wheel is heavier, which if it its the case then inertia plays a larger role.
But since this is not necesarily the case, given a 17'' and a 19'' wheel with the same weight will still make the car feel slow because of simple geometry from the formula
v = w r
where w is the angular velocity (in radians/sec) and r is the distance from the axle.

A simple example is the drag racers, why do you see such a tall tire on top fuel cars? because they need to compensate for the engine power at the starting line, a small tire would roast to pieces.
Why does a larger wheel/tire make your speedometer inacurate? same thing, not because of weight thou.

 

another thing to consider is where you got your 60mph speed from. Was this at the track against a radar ? or off your speedometer? Now that you have a larger diameter rim size, you have thrown the calibration of your speedometer off.

 

That is not necessarily true. As long as the overall diameter of the old and new are the same the speedo should be uneffected.

 

I used to be in the same boat, I had some 18" Konig Tantrum- 27lbs each with some 245-40-18 Potenza Poleposition SO3 (which btw suck) that weight about 25-28lbs, I went from 205-65-15s stock... the car felt really slow. I then got some 300ZX 16" wheels in black and since they where only 16lbs each wheel and like 12lb for a tire the car ripped harder than ever. Friend of mine has some Nismo wheels on his 350Z and we tried them on my Maxima, and the car didn't feel any slower or faster than my current 17" Enkei RPO1- 15lbs each with no tire on them, imported from Japan. So from testing on my car, I came to a result that its the weight that kills your performance basically. I might have lost 2WHP from my stock wheels when runing with the Enkeis, which are now my only wheels for dynoing or driving.

 

well i ot my times from the GTech meter that i have, i know its not 100% acurate but it is still .7 of a second slower then what i had b4 on the same GTech. Wheels and tires end up being the same size in diameter of the tire as stock. New is 245/40/18 versus the 225/50/17. One thing that confuses me is the stock wheels are not that light, they weigh around 24-25 lbs i think, i'm just dissapointed that i noticed such a big decrease in performance......now i need to save up money for exhaust to get my second back

p.s. ill post pics of car tonight

 

I put 18's on my maxima. They weighed 7 pounds less than my 17 stocks. But it will take a little more time to make the wheel do a revolution because it is bigger than the 17's thus making it slower. But, I have mashed my throttle and it still kicks great. Maybe minute loss on my speed. That can be erased with turbo or supercharger when they make it for my 2003.

http://www.cardomain.com/member_page...651_2_full.jpg

 

Contact area with the ground makes a difference also. Generally larger wheels use wider tires - the wider the tires, the bigger the contact area and hence more friction. Hence better grip to the road but also more power required to drive the wheels. You think Lance Armstrong would win tour de france with mountain bike tires?

 

Some tires are much heavier than others- for instance I just removed my Potenza RE040 235-45-17s off the front of my car and repleaced them with 255-40-17 SP9000 Dunlops, and the Dunlops weight 3lbs less than the Potenzas. Wet traction is amazing on the SP9000s and they grip alot better, have good steering response. I tend to drive alot, and when it rains I don't wanna be doing 50MPH in the right lane cause anything above that I hydroplane. I tested the SP9000s under the same conditions- same road at 80MPH and no hydroplaning.

 

isn't a 17 inch tire with 225/50's about the same circumference as a 235/35? wouldn't the lower profile tire kinda make up for the larger diameter of rim?

 

I had the same problem when I went from 17" stock wheels to 18's. Each new wheel and tire mounted and balanced weighed only 1 lb more than stock. I was suprised at the difference that 1 size bigger and 1 lb heavier made. My car felt slower and I even lost about 15 hp on the dyno. There are some threads about it here somewhere. In short, if you want to keep your car fast when upgrading wheels, light weight rims is the answer and don't get any bigger than an 18. Also, tires vary in weights also.

 

another weird thing i had 225/40/18 yoko avs sport on there for 2 days before i put these on (wheels/tires bought from a previous owner) and tha car was much quicker with those... so...i think the wider tires do make the car slower...

 

Think of it this way......

Olympic figure skating.....

The hot girl wearing very little is spinning. She starts with her arms stretched out to each side spinning fairly slow. She brings in her arms to her chest and now is spinning much faster. Her mass did not change did it? Just where that mass was ditributed. More mass in the center = easy to spin. More mass towards the outer edge = harder to spin.

 

Sorry buddy, I need to correct this error...."the bigger the contact area and hence more friction" THIS IS TOTALLY WRONG.....THE SIZE OF AREA HAS NOTHING TO DO WITH FRICTION FORCE........it's a common mistake, physics stuff.....very tricky....

 

Thanx for the correction - after all I do not want to spread "spoiled" knowledge. Perhaps "friction" is the wrong word - but I do beleive the physics professor said something about a positive correlation between the contact area on a wheel with force required to drive it. Can anyone else ellaborate on this one?

 

I havn't got that far yet, can't help with this one .... beyond my little knowledge as i have now..

 

This might be some your problem. The recommended 18" tire size when going up from the stock 17" wheel/tires is 235/40/18. Not 245/40/18. It's not too big of a difference, but your OD is slightly more than stock now.

Am I right guys?