Forums » Grassroots Motorsports » 3.7 pound difference per wheel. Noticable difference? 1 2

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  April 7, 2010 11:19 a.m. Techmonkey New Reader

  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.

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  April 7, 2010 11:22 a.m. Raze HalfDork

  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...

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  April 7, 2010 11:23 a.m. Blitzed306 New Reader

  <needs to know.

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  April 7, 2010 11:29 a.m. Techmonkey New Reader

  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. :)

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  April 7, 2010 11:30 a.m. oldsaw Dork

  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.

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  April 7, 2010 11:30 a.m. thatsnowinnebago Dork

  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.

  I'm gonna butta yo bread

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  April 7, 2010 11:31 a.m. joey48442 SuperDork

  YES.

  Joey

  Joey "all you are to me is talking ballast" Blatchford

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  April 7, 2010 11:31 a.m. Techmonkey New Reader

  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

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  April 7, 2010 11:32 a.m. 4cylndrfury SuperDork

  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

  "Simplicity is the ultimate sophistication." - Leonardo DaVinci

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  April 7, 2010 11:32 a.m. Wonkothesane New Reader

  Just for a reference point, on an autocross course adding a 100 lb passenger, I really notice a cornering/handling difference in my Miata (with a stock suspension) and about 1 second for every 100 lbs. So I would notice it..
  

  I doubt a regular driver would, but then, a regular driver doesn't look at wheel weight, do they? :)

  1 Mazda == Good. 4 Mazdas == More Gooder.

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  April 7, 2010 11:34 a.m. John Brown SuperDork

  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

  Internationally known as The Brown Stig

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  April 7, 2010 11:34 a.m. Techmonkey New Reader

  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.

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  April 7, 2010 11:37 a.m. Techmonkey New Reader

  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.

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  April 7, 2010 11:38 a.m. oldsaw Dork

  In reply to Techmonkey:

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

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  April 7, 2010 11:40 a.m. mad_machine SuperDork

  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

  Non-Sequitor Alert!

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  April 7, 2010 11:42 a.m. Techmonkey New Reader

  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. :)

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  April 7, 2010 11:43 a.m. 4cylndrfury SuperDork

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

  quoted for ZOMGTRUUUUTH

  Handle first, then go fast

  "Simplicity is the ultimate sophistication." - Leonardo DaVinci

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  April 7, 2010 12:10 p.m. nderwater Reader

  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 ;)

  Auto photo blog: http://motomania.tumblr.com

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  April 7, 2010 12:22 p.m. bigbens6 New Reader

  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....

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  April 7, 2010 12:32 p.m. Techmonkey New Reader

  @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. :)

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  April 7, 2010 12:42 p.m. maroon92 SuperDork

  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.

  XBL GamerTag: bcbrownell Current Cylinder Count: 47

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  April 7, 2010 12:52 p.m. Clay Reader

  Somebody is trying to get in "Say What"

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  April 7, 2010 12:56 p.m. Raze HalfDork

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

  A sphincter say's what?

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  April 7, 2010 12:58 p.m. John Brown SuperDork

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

  Internationally known as The Brown Stig

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  April 7, 2010 1:00 p.m. miatame Reader

  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.

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