Best bang for your buck 15" rim size

hks_kansei · Postby **hks_kansei** » Fri May 06, 2016 4:42 pm

Actually, if you want to move to the 15inch wheel for the easier availability of decent 15in tyres vs 14s, the cheapest option would probably be OEM NB8A wheels.

15x6 fairly light, and usually dirt cheap.
Happily takes a 195/50/15 and means that you have an easier tyre selection than the 14s until you decide to go for larger wheels/tyres (in which case the above 15x7 and 8 options are best)

sailaholic · Postby **sailaholic** » Sat May 07, 2016 10:35 am

manga_blue wrote:Recommended rim width by every R-spec manufacturer is 15x6.5 for 205/50R15, with an approved rim width range of 5.5 to 7.5. But, hey, what would they know?

A rare situation but I'll have to disagree with you here Manga. The "6.5" is the rim width used when taking all the other tire measurements. Changing the rim width also changes (slightly) the dimensions of the tire, as such all manufacturers note the rim width they generated the rest of the data with. This is almost always the middle of the size range.

I have never seen a manufacturer explicitly say a "prime" rim width, only a recommended range. Happy to be shown otherwise.

I will agree that 8" is outside the recommended range for a 205/50/15 by all / most manufacturers but the 949 testing was pretty conclusive the 8" is the fastest rim for 205.

All that said, I completely agree bang for buck you'll get some pretty awesome stiff/strong/light rims for a good price in the 6.5" odd range that that would likely be a better bang for buck option the a cheap 8" wide boat anchor.

greenMachine · Postby **greenMachine** » Sat May 07, 2016 2:12 pm

sailaholic wrote:
manga_blue wrote:Recommended rim width by every R-spec manufacturer is 15x6.5 for 205/50R15, with an approved rim width range of 5.5 to 7.5. But, hey, what would they know?

I will agree that 8" is outside the recommended range for a 205/50/15 by all / most manufacturers but the 949 testing was pretty conclusive the 8" is the fastest rim for 205.

Do you have a source for that testing? What tyres were used?

FWIW, Leven's motorsport guy recommended 7s for a 205/50x15 AO50 R-spec in M compound. This in response to the specific question 'best wheel rim width for that tyre'.

:mrgreen:

sailaholic · Postby **sailaholic** » Sat May 07, 2016 2:37 pm

Details were Miata.net or Miata turbo I forget which posted by 949 racing. The would have star spec or above style tires.

Sent from my iPhone using Tapatalk

Muzdaman · Postby **Muzdaman** » Sat May 07, 2016 3:33 pm

The manufacturers recommended rim width has nothing to do with what is fastest.

From Emilio at 949.

949Racing wrote:
Suspense wrote:What does significant mean though? So a 205 on an 8" rim is 'faster' than a 205 on a 7.5", which is 'faster' than a 205 on a 7", which is 'faster' than a 205 on a 6.5", but I'm curious what sort of difference we're actually talking about with the same driver and car. So holding everything equal, including tyre, but changing the rim width.

Everything else being equal, 2:00 course, about 1s going from 6.5" to 8" with a race compound tire. 225/45, similarly gain about 1.2s going from 8 to 9". Precise gain depends on course, driver, setup and what not but the gains are significant and repeatable. Look no further than your favorite high end sports car to see wheels as wide as the tread as OEM equipment. It's not ground breaking tech or anything, just something new to the insular Miata community. Here in the US, the community has already accepted 8's and moved onto 9's. It helps that we have a better, and less expensive selection of 225/45's to choose from.

original thread,
viewtopic.php?f=30&t=54435&start=30

lightyear · Postby **lightyear** » Sat May 07, 2016 10:02 pm

If you have stock NA6 power, 15x7 with 195 is enough. Without changing wheels and tyres on the day to a different size there is no way of knowing what is faster. I personally like 15x9's and 225/45's. Always try to go a slightly wider rim than the tyre. Stiffness is slightly more important than outright low weight.

PeterB · Postby **PeterB** » Fri May 13, 2016 6:50 pm

What class are you intending to compete in ? This may determine the maximum rim size allowed in a class you want to run in, as sometimes lesser classes may limit you to say +1" diameter and +1" width.

I ran 205x50x15s S and R-spec tyres on 15x6.5" and 15x7" rims and they felt fine on a NA6. I ran 225x45x15 on 15x8" rims on Fanta (NA6 race car) and they also felt very good.
'

Jeo · Postby **Jeo** » Fri May 13, 2016 8:29 pm

Redondo wrote:i am still a novice and need to get track time first.

Best bang for buck? Ignore mods. Go drive.

Once you're even close to what other people can do with a stock car, then start tinkering. You'll save move money than you could possibly imagine.

greenMachine · Postby **greenMachine** » Fri May 13, 2016 10:41 pm

Jeo wrote:
Redondo wrote:i am still a novice and need to get track time first.

Best bang for buck? Ignore mods. Go drive.

Once you're even close to what other people can do with a stock car, then start tinkering. You'll save move money than you could possibly imagine.

Quoted for truth.

As a self-confessed novice, by definition you do not know what you are doing - yet. Get some seat time, get your skills up and when you are reaching the limits there, then it is time to shift those limits up a notch or two.

Those limits are surprisingly high in a stock car when it is well dríven and well maintained. Guran (Bryan) had some fabulous times in his stock NA, because he worked on improving the nut holding the steering wheel, and learnt not just how to drive fast, but what was important to get right on the car if you want to go fast in a stock NA.

:mrgreen:

zossy1 · Postby **zossy1** » Sat May 14, 2016 9:32 am

I've tested 225/50/15 A050s on 8s, 9s and 10s.

The bigger you go, the faster you go. The difference in speed and car feel is palpable. YMMV, but I doubt it.

Alex 2550 · Postby **Alex 2550** » Sat May 14, 2016 2:00 pm

what Jeo said but to add to the can of worms........

I'm keeping in mind that its a standard low powered NA6 (that isn't a bad thing at all), the main track is wakefield and you are looking for best bang for buck so i assume no turbo ect in the near future.
maybe what needs to be asked is what do you have fitted now and have you found the limits of that setup?
I would go 15x6.5-15x7 (whatever you find light weight at right price) wrapped in 195-50. They will be plenty of grip for you at Wakefield. The straight from memory is just shy of 900m (please correct me if i'm wrong its been a few years since i have dríven there, thats including the small "turn one" kink).
So with that and with turn 10s (final turn) shape, your car and depending on your ability i think the speed you carry through turn 2 will be fine on the grip of 15x6.5-15x7 with 195s this will be the best bang for buck as you have asked and keep sprung weight down as your NA6 will notice weight here.
From there fit an LSD for grip and stability, i havent dríven wakefield in any car without an LSD or AWD but i imagine the inner wheel on turn 8 might spin a little without one but this is speculation for me.
If after that, extended track time and wearing the 195 tyres out you can always fit 205 on a 6.5-7 inch wide rim to go to the next level but more money and overkill at this stage.
For most people the 195 will give you years of driver development and make you a better driver, Keep in mind you will always be able to sell 15x7 if you decide down the track to go for more power and need more width in rim.
whatever you decide i wish you all the best with your times and don't forget HAVE FUN!!!