Is it true that RPF1, 15"
ET+41 weight is 9.4 lbs and ET+35 is 9.9 lbs ?

 

I wouldn't think they would be much different.

I have just always seen the 15x7 marked as 9.8 Lbs.

 

The 35mm offset wheels use more metal to space them out further.... The 41mm wheels had been listed as weighing 9.5 lbs until recently. I have seen then listed at 9.8 also. I wonder why they are now saying they weigh more.... I have the 7"x15"-41mm on my car and think they are great... One of the best things you can do to a GD-3 if not the absolute most wonderful thing.

 

Yes, both offset versions are around 9lbs. My friend who used to have an NB Miata had them. We put each one on a scale and they were definitely under 10lbs.

 

Hey Texas, there's a verrrrrry interesting article in this month's Grassroots Motorsports. Apparently they tested RPF1's vs a heavier TRM wheel (with the same tires) on a Spec Miata and found almost no performance improvement. Then they tested a slightly narrower tire vs a wider tire, and found the slightly smaller contact patch made the biggest improvement in handling performance.

Don't get me wrong, I love my RPF1's. I get great handling from them, and I feel like I have so much more "seat of the pants" feel with them over the Honda alloy wheels. But apparently the lighter (and more expensive) wheel doesn't necessarily mean better performance.

 

u should still get better gas mileage, if not any improvement in performance

 

thks fr all answer. It's not only better gas mileage, but break system too.

 

That is interesting.. The part about better performance with narrower tires has been brought up numerous times by Mahout and is something that has always made since to me.. The tires on my car were mounted on the RPF1s when I ordered and received them from TireRack. They are the same size as the stock tires, weigh 15 Lbs each and really aren't performance tires but touring tires of the type that came stock on numerous European sedans.. They would be useless doing auto cross or running hard on much other than asphalt with high content of flint or other course aggregate but that is what most roads I drive on consist of... I have a hard time understanding why the test that you read wouldn't have shown a more noticeable improvement.. I have been messing around with cars, motorcycles and bicycles for a long time and have always found that lowering unsprung weight and rolling resistance improved acceleration, ride, handling, braking and steering response... I made pretty good money building custom light weight wheels when I had my bike shops also... The only thing I can think of based on experience with a BMW motorcycle that had adjustable spring tension and damping on the suspension is that heavier wheels require more tension and damping than lighter wheels and that would cause the lighter wheels to not respond to irregularities in the paved surface if not adjusted for the weight difference... Is there a link to what you read so I could check it out?

 

I've been thinking on getting these rims for a little while paired with Yokohama S-Drives.
It doesn't make sense to me that the light rim wouldn't help performance though. I would expect better revs, better braking, and better mileage at least.
I've seen them 9.5 lbs for 15" at tire rack as well.

 

It's in the June 2011 issue of Grassroots Motorsports. They even cited an old 2003 unscientific test they did where they compared 13.5lb Kosei K1's to 22lb MSW Type 33's on a Miata. They were surprised at the time that the Kosei's only gained .2 seconds a lap (that's only half a percent!).

It's a really interesting read. Maybe it'll be published online, check their website.

 

I already checked the website with no luck but they do have some great articles....

 

.2 seconds can add up to a bit of time over long runs though. Figure a 15 lap hot lapping session, you just made up 3 seconds of time...if one were consistent and I would believe it would be even more time with the more laps you do because of the excess weight. If they are talking just about a 1 lap auto-x and only gaining .2 seconds, well .01 seconds could be what decides a win and 2nd place. When you are very serious about your racing, any improvement in time is WELCOMED when it comes to just swapping 2 parts that do the same thing.

Want even lighter wheels and wallet...CE28N in 15x6.5~7 +48~+42, about 8.1~8.8 lbs a piece.

 

I picked up on JCrimson's old, old wheels (he's kind of a queer for wheels). They are 16"X7" 38mm offset with 195-45-16 tires and are between the RPF1s and stock sport wheels in weight..The shorter, stiffer sidewalls and smaller diameter of the tires weren't as bad as I thought they would be as far as comfort...Taking sweeping curves at speed they were great and the smaller diameter compensated for the weight gain when accelerating.... They really weren't bad at all until I would down shift to pass a mess of slow moving trucks and pulled out while on the throttle... The torque steer was scary as hell... Wide offset wheels and superchargers don't work all that well together, but they looked good. @555sexydrive... I would have never considered how much of a gain that .2 seconds was when compounded by 15 laps... I have looked at the prices for light weight parts in racing catalogs and it blew my mind at how much those guys will spent to save a few ounces.

 

@Texas, If I recall right, you had the RPF01's on your car right? Did you get better mpg? And, how did the car feel overall?

 

Here is a article done by modified magazine testing this theory out. Performance Wheel Test - Modified Magazine Its a good read but in the end there is just to much variance to gauge the true benefit of a lighter wheel (all else being equal). Even with the same tire on the same car you cannot expect the exact same level of grip across all these sets of new tires. You can time the test car doing 10 straight laps on the same setup and come out with a variance of lap times, so how would you know it was only the wheels that caused the slower/faster time? What about the driver gaining experience of the course thus lowering the time? Or what about fatigue affecting lap times? Heat soak? Brake fade? IMO you don't test these things real world because it cant be accurate, simple math says the lighter wheel will help the car in every respect. Buy the lightest wheels for your intended use.


Here is a database of wheel weights to check from if anyone is interested: WheelWeights.net - Database of Wheel Weights

 

first reason that choose RPF1 is a look....second is weight, thks

 

I have RPF1s. Mileage is better in stop and go but less if you are trying to coast while going down hill while off throttle because the reduction of rotating mass.. You can pull hills with less effort so what I do is the opposite of what hypermilers do.. When traffic conditions allow, instead of lifting off of the throttle when going down hill I will accelerate a little when driving on a road on rolling hills one after another so I don't have to use more throttle as soon on the hill I am approaching... I have found that watching the percentage of throttle I am using on either my scan gauge or throttle controller and using the ec5 mode that opens the throttle more slowly than the stock normal setting and using a light foot, has helped with learning how to make the most out of the changes from heavier wheels in regards to gas mileage... There are many ways that the wheels have made driving more enjoyable... The steering is lighter, braking requires less pedal pressure, the ride is improved since the shocks are dampening less unsprung weight, the difference in width and offset along with reduced rotating mass eliminates almost all rear sway when making quick directional changes, there is a larger volume of air in the tires and more aluminum surface to dissipate heat so the tire pressure remains more constant and traction is more consistent, and of course the acceleration and deceleration is is improved considerably.

 

Wow, thanks Texas. Guess I'll def. be getting these rims in the near future, probably with Yokohama S. Drives.