Rocwandrer

The manufacturing quality control that Tirerack finds acceptable is not quite up to my standards. This spoke measured around 1/16" thinner than the the others, and the porosity right on the surface of the back face is not encouraging to me. I'm sure they are basically as safe as other gravity cast wheels of the same weight to size ratio, but I ended up sending it back and getting a set of 6UL 15x9 wheels....


Edit: to their credit, I should mention TR took it back and paid the return shipping, even though they said it wasn't defective, or any worse than any other wheel they sell under the TR Motorsports name.

wannafbody

iTrader: (1)

Will the 15X9 C3M fit an NA without a roll?

240_to_miata

iTrader: (2)

Depends on your suspension. My rear rubbed slightly on flyin miata springs cause they were so soft.

Joe Perez

iTrader: (8)

For me, it's a matter of principal. They waited until 949 did all the hard work and proved that there was a market for a "good" Miata-specific wheel, then cloned the 6UL design and made a cheaper, heavier version with poorer quality control.

The price difference between the C3M and the 6UL is relatively small. The quality difference is somewhat larger.

240_to_miata

iTrader: (2)

IDK about your industry, but this is how the world works. Businesses strive on other companies business principals. I spend many hours doing market research on what my competitors machines are capable of, and how they do what they do. From there I build something better...if it is similar, so be it. If it is patented, we work around it. Even patents are pathetically easy to work around. Guess what, those guys do the same exact thing to us. I agree ethically its not great, but I wouldn't call "copying" a size and offset copying someones "hard work".

Remember the C3M is NOT the 6ul knockoff (the C1 is)...and the C3M is the only one they offer in 9", so the statement of copying the design is false.

The point is, the C3M is a legitimate second option. It is NOT as good of quality, and the cost vs quality might not be comparable to some, but it still works...and its not "copying."

---- THE MIATA IS A "COPY" OF THE LOTUS ELAN CONCEPT... GET OVER IT

/ rant

astroboy

iTrader: (18)

So I just learned something:

XXR Wheels is The Pursuit of Lightweight wheel

I guess they started out with some heavy wheels so they have nowhere to go but up (down) but honestly I never would have guessed that is what they were trying to make.

Savington

iTrader: (31)

No 15x9 will fit without a roll.

Joe Perez

iTrader: (8)

You're right- my bad. I forgot that they changed the cosmetic design slightly when they copied the wider styles of the 6UL.



Yup, couldn't agree more. Great design concept, and one worth resurrecting. If the Mazda version weren't considerably better engineered, and if Lotus hadn't discontinued the Elan 15 years prior to the Miata's release, then I'd consider the Miata to be a cheeky copycat of it, kind of like how I consider the BMW Z3, Honda S2000 and GM Solstice / Sky to be cheeky knockoffs of the Miata.

For all intents and purposes, Mazda invented the the modem lightweight, inexpensive roadster in an era when the concept had been completely forgotten. Lotus, MG, Triumph, etc., had all abandoned the concept a decade or more earlier, and Mazda took a huge risk investing in a design concept for a market which, at the time, wasn't even know to exist.

If 949 had said "fuсk it, we're not interested in this anymore" and closed their doors, and then 15 years later TR had come along and said "Hey, I wonder if anybody might be ingested in a cheap 15x8 / 15x9 wheel these days? Let's invest a lot of money in designing one on the off chance that maybe people will buy it" then I wouldn't feel quite the same degree of annoyance towards them about it.

Sentry

While we're on the topic...

What are some good lightweight tires in say, 205/50R15 or 195/60R14?

Unless you get some heavy *** wheels, the tires will be heavier than them anyway. So I'd like to know what some lighter options for rubber are.

EvoRoadster

iTrader: (1)

Hmmm, thanks for that Exospeed link. I currently am running 15x9 C3M rims with 225-45/15 Hoosier A6s for autox and was going to move up to a 15x10 rim for the A6 in 275-35/15 for the upcoming season.

astroboy

iTrader: (18)

Did they build another track out there yet?

Rocwandrer

If you are interested in ride comfort, light weight tires might be a great way to go.... otherwise, your question sounds wrong. Do people here really believe all this crap about weight being the most important performance factor in wheels and tires?

sixshooter

iTrader: (12)

Most important? No.



Important to acceleration and deceleration, yes it is very important.


Accelerate this stone wheel to 300rpm using 50hp.



Now accelerate this bicycle wheel to 300rpm with 50hp.



Now tell me which one would make it to the end of the longest straightaway first using the same powerplant?


Now, with the stock Miata brakes, bring each one to a stop from 300rpm.

Which one would need to start braking sooner to reach turn-in speed at the end of the straightaway using the stock Miata brakes?



Important? Yes.

Next exercise, imagine two Miatas going over a rough section in the track. One has 80lb wheels and tires on each corner and the other has 10lb wheels and tires on each corner. Let's say there is a 2 inch drop in the pavement that the car encounters in a corner followed by a two inch rise before leveling off (like turn 17 at Sebring). As the car is traveling about 75mph in that turn and the fall and rise occur quickly at that speed, which car's wheels will be able to more quickly respond to the drop and rise without losing contact with the concrete surface.

Which wheel's mass in motion, given the same shocks and springs, will be best able to change direction of motion -from down -to up -to level and maintain the contact patch to concrete connection for the greatest amount of time?

Which car's contact patch is doing a better job helping the car continue to turn through the unevenness of the track surface?

How helpful is a contact patch that is not in contact as often?

Is weight most important? Sometimes.

Is contact patch size most important? Sometimes.


Life is a series of trade offs.

So is racing. A blown big block Chevy would get my car down the straights faster but it wouldn't corner with a Spec Miata. A 18inch wide tire and wheel might stick like bubblegum in the corners but might accelerate more slowly in the straights and decelerate more slowly at the ends of the straights. There is a point of diminishing returns for anything and you have to figure out where that is through calculations and testing.

You are speaking in absolutes and I think that is unwise. It sounds like you are trolling.

Sentry

d

I was more trying to make a point that people will obsess over a pound or two difference between two wheels (like a 6ul vs a XXR or something) while you can gain/lose just as much rotating mass with tire choice and yet there's very little/no data on tire weights.

Edit: For example when I had my turbo Civic one drag slick mounted on one STEEL diamond racing wheel weighed 26lbs combined. I bet any road legal steel belted radial tire on even a super light wheel would weigh more. Just cause the only metal in the slick was the bead, so it was a very light tire.

skidude

iTrader: (3)

I have often wondered the same thing, I just always assumed that the grip and other properties of the tire were more important that the weight.

EvoRoadster

iTrader: (1)

Martin, good to hear from you. No, all we have is the lower Halawa lot at the stadium for autox. I hope all is well.

Daniel

astroboy

iTrader: (18)

Drat. I should be back out to play soon

On topic I found these for the e30's and they don't look too bad, too bad they don't come in 9" wide
http://www.harrisonmotorsports.com/d...4x100-e30.html

Rocwandrer

I did a sample calc a while ago when having a similar discussion on another forum and was surprised to find that, when considering the relative polar moment of inertia of each, where the weight is saved, and the ratios, a pound saved off the flywheel was 12 times as important as a pound saved off a wheel, so 3 times as important as wheel weight. Neither was earthshatteringly important. Don't someone go and quote me on that. it was based on a specific flywheel diameter, wheel mass distribution, gearing, etc.

Exaggerations like that are very useful for explaining "whys". Not so useful for figuring our the order of magnitude of the effects, which was the context of my original response.

If we take the heaviest wheel tire combo anyone on this forum has, and the lightest, and control our experiment for the difference in tire grip, we would find that both are very near equivalent. The reason is that the stock Miata brakes (perhaps with a little bias adjustment) are good enough to lock all 4 wheels at will. Therefore, the only effect the extra weight has is in moving the contact patch load up the load sensitivity curve a hair. If we took the difference in the wheel weight and added it close to the CG of the lighter wheeled car, they would both stop in the same distance.

At any power at which you have enough power to spin the tires at will, the same is true for the weights in acceleration, except we count half of the weight savings, because the front wheels are still driven by the road, the power for that is derived from the engine of the car.

I snipped out your bit on unsprung mass, thought I recommend others who are interested read it, as it explains the concept pretty well. I will say at least a few more things more on this.

1.) You mention contact patch area like it is a function of tire size, with bigger tires having bigger contact patches. That's not actually true. Contact patch area is a strong function of tire pressure, and a weak function of sidewall stiffness. The contact patch area is basically the instantaneous corner load divided by the pressure in a bias ply. In a radial with stiff sidewalls, you can subtract a tiny bit from the slightly higher contact pressure right under the sidewall if the sidewalls are stiff enough. The advantage to wider/narrower and/or bigger/smaller diameter tires is way more complicated than just an increase in area, which you can achieve with a little lower inflation pressure.

2.) Reducing mass when there is no other trade off is always good, but there is almost always a trade off. The easy way of saying that sounds like an absolute. Sometimes it is worth more mass in a wheel just to get more stiffness, so there isn't camber loss occurring in the wheel back bell. I was responding to someone who sounded like he was advocating looking for the lightest tire as a starting point. If there was an RE-11 and a Star Spec both available in similar gearing, and one was lighter than the other, and I thought the lighter one would have just as much grip, I might pick it for being lighter. Probably I would still pick based on something else, like rain performance, or cost. The fact is it isn't like that. If the one that sticks better and costs less and has better gearing is 1 lb heavier, we easily pick the heavier tire if we know what we are doing and we want to go faster. It is almost never a good idea to pick the lightest option, unless we are picking it because it offers something else, and happens to be light. A toyo T1R that is the exact same diameter and tread width but lighter than an R1R is never going to be faster. That was my point. It isn't like there are equivalent options out there that are the same except one is lighter, or options where the other differences are overshadowed by weight. Lighter is better, as long as it doesn't compromise something that matters more, which is often everything else. All this based on timed events, not feel or pride or ride quality or anything subjective.

3.) I pretty much regret saying anything at this point, since my perspective is so far removed from what is average for this forum that I do sound like I am trolling, and I felt obligated to put the effort into a reply, even thought I'm not feeling like it will be well received.

4.) This is right in my area of professional expertise (the practical application of the theoretical side of solid mechanics and energy systems). If we were talking botany, or medicine, or something else I know nothing about, I wouldn't just state things I think like they are facts, because then they probably wouldn't be

Rocwandrer

If it were possible to select this way, the mass lost from the tire would be at least subtly MORE important than the wheel, since it is further from the center. I still wouldn't pick tires based on weight. a bigger diameter tire weighs more, but I wouldn't pick it because it would hurt my gearing. A narrower tire (in the same compound/construction) weighs less, but I wouldn't pick it because it would not be as fast around corners, and by a margin that is much larger than it would help me accelerate and handle bumps.

I started out replying because you said there is no data on tire weight. Most tire manufacturers publish tire weights. Often they have the data on their own individual websites. Tire rack for one compiles all that data neatly for us. You can look up pretty much any tire they carry and in the specs tab it will list the weights of each and every size of that particular tire.

mighty mouse

iTrader: (9)

Make your RM's 15x9? Just saying....