Wheel weight, tire weight and power...

[GODCHSR]

Kind of wanting to get a general idea of some thoughts on this.

I'm looking and spending some money to buy lighter wheels but I wasn't sure if the cost was justifiable. Will this translate into major gains?

IE: If I swap out the stock flywheel to a Fidanza obviously I gain lost power from parasitic reduction. (crank pulley, driveshaft,etc...)Is the same principal true with wheels? and is the equation (power gained = reduced weight) Whatever that would be.

Also I am wanting to stick with an 18" wheel BUT assuming I went down to a 15 (Weld draglite... ie) would the increased tire size negate the weight loss of the wheel? or is it so minimal that it's worth the wheel reduction?

[simmode1]

I inquired about this a year or so ago. I have 15lbs 16x8.5 wheels and was curious about stepping up to a 18x9.5 that weighed 21lbs.

What I found was that the value of a lightweight wheel really depends on what you're using the car for. If this is for some kind of competition time attack car where fractions of a second really mean something, then by all means, get the lightest wheel you can afford. But... if this is for a street car, obsessively chasing weight savings that you'll never need or even notice is pointless.

On a streetcar, being pleased with the look of your car and the width of your wheels/tires and having good traction is more important, IMO. However, there is a point of a wheel being excessively heavy in my opinion. 25lbs is the heaviest weight wheel I'd consider buying....

But buying lightweight on the cheap is easy thanks to the good sizes the Enkei RPF1's offer. The only problem with RPF1 is that they're so whored out...

[240dx]

I swapped my stock s14 rims for 18x9 Stern St-8 rims. They look so dam good but I do sacrifice a very noticeable power loss at the low end. Top end feel pretty good though when Im flying down the freeway.

[simmode1]

I swapped my stock s14 rims for 18x9 Stern St-8 rims. They look so dam good but I do sacrifice a very noticeable power loss at the low end. Top end feel pretty good though when Im flying down the freeway.

Really? When I went from my s14 SE's to 18x8.5 Z33 anniversary wheels, I didn't feel any loss at all, only more traction...

[sr20power]

I agree with simmode1, it depends on what you using the car for. I also read (I think Dec. issue of DSport mag) they have an article about this very subject, about sprung weight and un-sprung weight. I will butcher the hell out of it if I try to explain it. Check it out online.

[jeff420]

wheel weight affects power, the end. i had some heavy a** 17's on my car when i went to the track once, they KILLED my times. i felt like i was driving a friggen civic.

[sr20power]

Wheel weight affect more than JUST power.

[KAbezon]

The weight of your wheels has nothing to do with power of your engine. The only thing the weight of your wheels effects is the unsprung weight and the power to weight ratio to your car...

The lighter the unsprung weight of your vehicle is (being any weight that is not supported by the suspension, including the wheels tires, brakes, and certain suspension components) the less rotational mass there is, helping to increase acceleration and braking efficiency...making it seem like the car is more powerful, when in reality the cars power is the same, the car is just easier to move

The rule of thumb is for every ONE pound of unsprung weight you reduce, it is equivalent to 10 pounds of sprung weight off the car, so the lighter the wheels, the lighter the car seems compared to the actual curb weight of the vehicle

[jeff420]

no s*** that it wont increase your power, i just figured everyone was smart enough to realize that heavy a** wheels are going to make your car slower

[simmode1]

wheel weight affects power, the end. i had some heavy a** 17's on my car when i went to the track once, they KILLED my times. i felt like i was driving a friggen civic.

Do you have any timeslips comparing speeds before and after these wheels? Just to give a realistic picture of the loss you're referring to. I bet we're talking fractions of seconds here...

See, if you're doing timed competitions, of course things like this will be of higher importance. But if you're just commuting around/ highway cruising/canyon runs who cares? It's not as big of an issue.

[KAbezon]

Do you have any timeslips comparing speeds before and after these wheels? Just to give a realistic picture of the loss you're referring to. I bet we're talking fractions of seconds here...

See, if you're doing timed competitions, of course things like this will be of higher importance. But if you're just commuting around/ highway cruising/canyon runs who cares? It's not as big of an issue.

agreed, unless you have any motorsports in mind, it really doesn't matter a great deal. Getting lighter wheels, may give you enough decrease in unsprung weight to drop maybe a tenth of a second at a drag strip in the end if you go with really lightweight wheels, but it's not the most cost effective form of weight reduction...I would just find wheels you think look nice, and go with that

[jeff420]

if your just cruising duh it doesnt matter, but when races could be lost by fractions of a second it means everything.

dont have any timeslips on hand but yes theres a difference. when you cant spin your tires in second and your car barely accelerates you know your slower. on my first car i got a new set of wheels and my times got worse, like .3 of a second worse. if your just worried about lookin good, who cares.

im more worried about going fast than having big a** wheels. doesnt mean i dont plan on getting some baller a** wheels but thats only after im happy with my setup. once i boost my car and get it painted, then ill go for some baller wheels and not care, ill just up the boost. till then, function over form.

[Razi]

I went from Stock SE wheels to 350z wheels and I felt a little bit of a difference, but I also have a lot more traction.

The weight probably slowed me down a little but that's what my turbo is there for.

[Chris28]

If you get a smaller diameter wheel you will accelerate faster. I think if you were to get a lightweight wide wheel with a small diameter the diameter itself would outweigh the weight of the wheel. No pun intended lol.

[killernoodle]

Wheel weight is not as noticeable as power modifications.

If you pay an extra $1500 to get wheels that are, say, 4 lbs lighter than the ones you have, I doubt you'd notice the difference.

If you took that $1500 and put it towards a power adder, you'd definitely notice a huge difference.

savvy?

[Ajax]

OP, concerning one of the other questions- Tire Rack has the weight of most of the tires they sell (look in the specs section). From there, you can see how much difference there is between tire sizes. Same goes for a lot of their wheels- although their wheel selection kinda sucks for 240s. But at least you can get an idea from actual products.

[simmode1]

once i boost my car and get it painted, then ill go for some baller wheels and not care, ill just up the boost.

The weight probably slowed me down a little but that's what my turbo is there for.

Your car carrying some extra pounds? Add power. Done.

Here's my perspective: Don't worry about trying to have a fast streetable 240 if you're not turbo'd or swapped. A KA that's stock or has a few bolt-ons ain't gonna be fast no matter what. But once you go turbo or swap in a more powerful motor, this weight issue loses importance.
Modified by simmode1 at 5:07 PM 11/17/2009

[GODCHSR]

I'm getting the impression that we are not considering the rear Wheels to be a 'parastic rotational mass'.

This is more than simply unsprung weight, right?

I mean the you don't lgihten the driveshaft to make the 'car' lighter (necessarily). You lighten the driveshaft to make the 'drivetrain' lighter.

So my question, kind of, is there a RWHP/TQ loss from running heavier rear wheels?

[neverlift]

ok godchsr I'll chime in here.

yes going with a lighter wheel will increase your performance. However if you go crazy on the tire size you just killed any real gain you would have made(total weight of rim and tire is more important for your build) IMHO you are gonna be putting down some real arse, do you and wd have any tire rules? if not I would go with a slick on a 15" that way you can play with tire pressure. Traction will be important for you.

[KAbezon]

no...

just like having shorter or taller gear ratios can help either lower E.Ts or help you gain mph, they don't add or take away hp/tq, it just changes how it is applied.

Heavier wheels take more TQ to move at the same rate as a lighter wheel, but it doesn't lower your TQ, it just dictates how much TQ is needed to do the job compared to heavier or lighter wheel. So if you run a lighter wheel the TQ you have, is used for efficiently than if you have a heavier wheel, giving you the impression you have more power/torque

Like I said before your engine will produce the same amount of power regardless of what the rest of the car is doing. Using that power is a different story. The more unsprung weight you shed, the easier it is for that power to be used effectively, and your car to seem faster..

EDIT: In retrospect, you will probably get different dyno outputs depending on the weight of the wheels, so in one aspect, yes wheel weight does net lower hp readings on a dyno graph...but in reality, the more efficiently you put down that power, the better off you will be on a race track, and the more power you will think you have

[GODCHSR]

no...

just like having shorter or taller gear ratios can help either lower E.Ts or help you gain mph, they don't add or take away hp/tq, it just changes how it is applied.

Heavier wheels take more TQ to move at the same rate as a lighter wheel, but it doesn't lower your TQ, it just dictates how much TQ is needed to do the job compared to heavier or lighter wheel. So if you run a lighter wheel the TQ you have, is used for efficiently than if you have a heavier wheel, giving you the impression you have more power/torque

Like I said before your engine will produce the same amount of power regardless of what the rest of the car is doing. Using that power is a different story. The more unsprung weight you shed, the easier it is for that power to be used effectively, and your car to seem faster..

EDIT: In retrospect, you will probably get different dyno outputs depending on the weight of the wheels, so in one aspect, yes wheel weight does net lower hp readings on a dyno graph...but in reality, the more efficiently you put down that power, the better off you will be on a race track, and the more power you will think you have

I totally understand it won't decrease actually engine power but moveable power... see

It's like dynos from using UO pulleys, they show gains even though no real power is 'made'... just freed up.

So I assume the wheel issue is the same.

[GODCHSR]

ok godchsr I'll chime in here.

IMHO you are gonna be putting down some real arse, do you and wd have any tire rules? if not I would go with a slick on a 15" that way you can play with tire pressure. Traction will be important for you.

No rules on tires. I plan on running as wide as needed to 2 step with as much boost as much clutch can handle.

I am looking at 2 sets of wheels... Weld and some super heavy Moetgi.

I can't honestly afford to keep both but the Weld draglites are absolutely ugly as crap and I'd hate to give up style to gain something that 'may or may not' actually affect my 1/4 time

[simmode1]

Weld draglites are absolutely ugly as crap and I'd hate to give up style to gain something that 'may or may not' actually affect my 1/4 time

What size are you wanting to run?

[KAbezon]

Yes, but saving enough weight to gain a little of power to weight isn't going to do anything on a street orientated car. Lets say by getting lighter wheels you save enough unsprung weight to maybe get 3 or 4 more whp on a dyno or even 6 or 7...was the $1500+ for wheels worth it for something your probably not going to notice?

probably not

On a race prepped car, every little amount of weight you shed is useful, ESPECIALLY unsprung weight, so spending tons of money to lighten the car, and get every tiny bit of weight down and power up can mean the difference between winning a competition and looking at the guy who won from the stands

So in the end, will lighter wheels net you some extra numbers on a dyno, yeah, but does it really matter in the end? Is this a daily driver or a track car? I say just find some wheels you like, ones that you think look awesome on the car for street use, and get another set of lighter wheels that don't even have to look good for the track...

[GODCHSR]

What size are you wanting to run?

Weld Draglites 15x8 and 15x3.5

Motegi Touges 18x10 and 18x8

[simmode1]

Weld Draglites 15x8 and 15x3.5

Motegi Touges 18x10 and 18x8

Why not meet in the middle and get 17x10+18 RPF1's as a compromise? I've read that the 15x8 Draglights weigh about 13lbs. The RPF1's weigh 17lbs, but they are wider, only cost about $275 a piece, you can fit more rubber and use them on the street without being ridiculed.

Then when you hit the track, just throw you 15x3.5's on up front and go...

They also have 16x8 RPF1's that only weigh 15lbs and come in both 4x114.3 and 5x114.3.

[duffman1278]

Lighter flywheel will not entirely = more hp and torque. With its lighter weight comes the need for more energy to keep the momentum going on the flywheel as a pose to a heavier one. Factors such as inertia come into factor with lighter tires and flywheel.

Read this, these guys pretty much hit the topic on the spot.

zer...re-hp

[GODCHSR]

Lighter flywheel will not entirely = more hp and torque. With its lighter weight comes the need for more energy to keep the momentum going on the flywheel as a pose to a heavier one. Factors such as inertia come into factor with lighter tires and flywheel.

Read this, these guys pretty much hit the topic on the spot.

zer...re-hp

Thank You honestly but... I am only concerned about getting from point A to point B fast.

A lightweight drivetrain is extremely desireable to me and I was not sure if the wheels acted in the same manner.

I always see drag time slips people post and they'll say things like "On my heavy @$$ 19's..." or such. I just wasn't sure if this was translating into actually bad timeslips or if the effect was unoticeable.

If it's unnoticeable then I choose the nicer looking wheels.

I think this is an age old "Form vs Function" question

[GODCHSR]

Why not meet in the middle and get 17x10+18 RPF1's as a compromise? I've read that the 15x8 Draglights weigh about 13lbs. The RPF1's weigh 17lbs, but they are wider, only cost about $275 a piece, you can fit more rubber and use them on the street without being ridiculed.

Then when you hit the track, just throw you 15x3.5's on up front and go...

They also have 16x8 RPF1's that only weigh 15lbs and come in both 4x114.3 and 5x114.3.

Those are too expensive. I am a deal buster.

$275 each is WAY too much for me. The Motegis I am looking at are $110 a piece and the Welds are like $80 a piece.

So basically I could get both sets for the price of the RPF1s. (nice yes yes yes)

BTW I have plenty of rubber right now anyway. 295 in the back, 275 up front

[simmode1]

Those are too expensive. I am a deal buster.

Damn man... RPF1's are the lightest, cheapest, high quality 'street' wheel on the market. If you can't afford those, thats a problem. $275 is just retail price. Look around, there are bound to be some vendors having Holiday sales. There are deals to be had out there. I think it would be worth it to save a little longer and get something that meets you needs rather than having to switch your wheels every time you want to hit the track.

Plus... if you buy 1 full set of the Motegi Touges and 1 full set of Draglites, you're still gonna have to buy and mount/balance 8 tires. Will you still be coming out on top then? Maybe, if you keep your old rubber and put it on whatever new wheels you want. But you're still gonna have to buy more rubber for your second set.

But hey, sounds like you already got your mind set on what you want to do, so go do it. It's not a bad plan. It's just not what I would do, which is ok since I'm sure we've got different goals and perspectives.

Edit: I didn't really notice your sig before since I was at work and pc's there block sigs, but now I'm at home and can see you're tuning your car to to run 10's in the 1/4. So, like I said earlier, if you're doing timed competitions... lightweight is a weapon of critical importance. It's obvious now that you're not looking for a middle-of-the-road compromise kind of wheel that you can use at the track and on the street. You need that wheel the will give you those fractions of a second. So go ahead and pull the trigger on the Draglights with some big bulging rubber...
Modified by simmode1 at 10:38 AM 11/18/2009