3.7 pound difference per wheel. Noticable difference?

Just a quick question regarding wheel weights. On a thread on another forum, I was comparing the TRM C1Ms ($99 for a 15x7 13.6 pound wheel) to Enkei RP-F1s ($199 for a 15x7 9.9 pound wheel). My statement had been that that the small difference in wheel weight would not make a noticeable difference to anyone but the most competitive drivers. I was told that is somewhat incorrect and the four pounds would make a difference in ride quality and traction.

So I ask the gurus of performance! Daily driver, autoX car, even HPDE; would there be any type of noticeable difference in ride or traction based on a 3.7 pound difference per wheel? If so, is it the type of thing the average Joe or weekend enthusiast would really notice?

Mark

Edit: Sorry, forgot to mention this is on an NB Miata. I know the car in question is an important part of the equation.

http://en.wikipedia.org/wiki/Unsprung_mass for starters...

For every 7-10lbs lost on any car you gain 1hp for sprung weight,

For unsprung weight (i.e. wheels) the ratio is ~ 1:6, so 15 lbs lost ~ 90 lbs of sprung weight which is something like 9-13 HP increase. The real benefit also the improved grip and wheel follow on rougher surfaces.

Then look at it as a reduction in rotational mass...

I highly doubt you'd notice the gains from the ol' butt dyno, but measured times may show a small gain. You really have to ask yourself, is the extra $$$ worth it?

I can think of plenty of cars I could buy with the extra $400, a tow dolly, repair parts for one of my cars, etc...

<needs to know.

Raze wrote: http://en.wikipedia.org/wiki/Unsprung_mass for starters...

I do understand the basic concept of unsprung weight. I guess I just don't understand the tangible impact of a relatively small amount of weight. Just seemed to me like someone was splitting hairs about the theory and not the actual difference those few pounds would make to the driver.

I'll read up on those links a little later today and see if they can give me more background to figure it out. Thanks. :)

In reply to Techmonkey:

Both points are valid; reduced unsprung weight generally has benefits, even if the bennies are relatively small.

There other factors in play:

How much do the original wheels weigh? What kind of suspension design does the car have? Are tires getting changed also - their weight will have some influence, too.

Really, just how sensitive is the driver to changes in vehicle dynamics? Some people just don't know, or care.

miata.net will tell you that it is a huge, massive, earth shattering difference. Me? I've only two sets of wheels on my miata and one was the 18 lb steelies.

YES.

Joey

thatsnowinnebago wrote: miata.net will tell you that it is a huge, massive, earth shattering difference. Me? I've only two sets of wheels on my miata and one was the 18 lb steelies.

That is exactly where that statement came up! laughs

so ive been told that a rule of thumb is 1lb of wheel weight = 10 lbs of static car weight, so tugging around 14.7extra lbs around the car should be like adding 148 lbs of weight into the cabin...or using 4 wheels that are 3.7 lbs each lighter is like adding 148 lbs of lighness

Miatas in general are very sensitive to wheel weight changes:

Anything under 15lbs will be good. The closer to 10lbs the better. Factory Miata wheels rance between 9lbs and 18lbs.

Reference: http://www.miata.net/faq/wheel_weights.html

oldsaw wrote: In reply to Techmonkey: Both points are valid; reduced unsprung weight generally has benefits, even if the bennies are relatively small. There other factors in play: How much do the original wheels weigh? What kind of suspension design does the car have? Are tires getting changed also - their weight will have some influence, too. Really, just how sensitive is the driver to changes in vehicle dynamics? Some people just don't know, or care.

In this case, it's the exact same car with the only difference being the wheels (C1Ms Vs. RP-F1s). I don't disagree that there is a difference. My thought is that it would be so small in terms of driving dynamics that the average person or weekend dabbler would not ever notice the difference. Even factoring in that the Miata is very sensitive to wheel weight.

4cylndrfury wrote: so ive been told that a rule of thumb is 1lb of wheel weight = 10 lbs of static car weight, so tugging around 14.7extra lbs around the car should be like adding 148 lbs of weight into the cabin...or using 4 wheels that are 3.7 lbs each lighter is like adding 148 lbs of lighness

Ah! Thanks for the info. I understand the basic concepts but didn't have equation or yardstick like that to help me really weigh it out properly. (pun intended) That does give me a better idea of the potential impact it might have.

In reply to Techmonkey:

If the price is a non-issue, I say always err on the side of lightness-is-better.

for 99% of the population... super heavy 20+" dubs are fine and do nothing but make the ride smoother (they pummel the road into submission)

for the rest of us.. lighter is better. We argue the benefits of a solid axle over IRS.. but lighter rims (and tyres) can make just as big a difference.

Lighter is ALWAYS better

oldsaw wrote: In reply to Techmonkey: If the price is a non-issue, I say always err on the side of lightness-is-better.

True. With my budget, I opted for the slightly heavier wheel since it enabled me to get better tires (RE-11s) since I think tire quality will have more impact than weight with my low skill level. :)

Techmonkey wrote: tire quality will have more impact than weight with my low skill level. :)

quoted for ZOMGTRUUUUTH

Handle first, then go fast

When I bought my '99 Miata, it was wearing a set of heavy 17" rims the previous owner had installed. Replacing them with 15" OE wheels saved almost 6# per corner and made a noticeable difference in ride quality and steering response. It was hard to tell if the car was quicker or not because of the turbo ;)

I think you have to look at it in terms of % as well. 3.7lbs on 40lb dubs is like 9% but on 12lb wheels it is 31%... as well 14lbs lost on a 5K truck is different than 14lbs on a go kart. In the end, with the lighter wheels being cheaper, this is a no brainer, there is no down side, while you may not notice that the accelerates quicker by the old butt dyno, it will...

You may not be able to tell that you have better more consistent tire patch contact, you will...

You may not notice that the car has better transitions and cornering grip, it does...

And while none of these may individually blow you away, as Raze said, I'm betting to cumulative sum will show up on the stop watch...

As also stated, what was your previous wheels weight? And tire weight for that matter....

@bigbens6

The cheaper wheels were actually heavier. :)

TRM C1Ms - $99 each and 13.6 pounds Enkei RP-F1s - $199 each and 9.9 pounds

Another good point regarding percentages, BTW. I hadn't thought of that and it does put it in perspective for me.

As for the previous wheel weight, I was running the stock 15x6.5 wheels that came on the 99-00 NBs. About 14 pounds IIRC. I was swapping tires each season and had been running RT-615s (205) on them. Not sure what the overall difference is between the old setup and new. Though I'm not so much concerned about about that as I was trying to figure out if someone was really splitting hairs to say it would make a significant difference between those two wheels with the same car/tire setup. I now see that they had a very valid point. :)

Definitely going to be a noticeable difference....is it worth 400 dollars? maybe not.

The wheel is the part that is furthest out in the rotation so it will have a bigger impact. The flywheel and driveshaft have a pretty big impact as well because of the speeds that they spin. A lighter wheel bye 3.7 pounds a pretty big difference.

Unsprung weight is kind of a big deal, it's apartment smells of rich mahogany, and it has several large leather bound books.

Somebody is trying to get in "Say What"

Clay wrote: Somebody is trying to get in "Say What"

A sphincter say's what?

And if you want him to be published, please make sure you click on the " + " icon at the bottom of his post.

If you're asking the questions I doubt you'll notice. Either wheel is good for a street Miata. I'd say the RP-F1s are well worth it, but then again I wouldn't spent the money either.

Going from 16" SSR to 17" Work to 14" weaves, lightweight wheels do make a noticeable difference.

Even on a car like the E30 that is much heavier.

The most apparent for me was under braking.