1st Gen. ITA tire/wheel size - Panasport

[cpa7man]

What tire and wheel size combo are most of you running? Please state offset of wheel also.
It seems most are running 13x7 (4" offset)Panasport with 225/50/13 Hoosier's.

Thanks for the input.

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Paul Pineider
ITA 05 (Soudiv)

[Scott Nutter]

Well, maybe the fast guys are running panasports$$. I've run 205/60's (Kumho and BFG) on both the stock wheels and Diamond Racing Wheels, 13x7 (4" offset), currently have a set of the Kumho Ecsta 700 215/50's that I think I ruined by running under-inflated.

What tire/wheel arrangement were you looking at?

[cpa7man]

Originally posted by Scott Nutter:
Well, maybe the fast guys are running panasports$$. I've run 205/60's (Kumho and BFG) on both the stock wheels and Diamond Racing Wheels, 13x7 (4" offset), currently have a set of the Kumho Ecsta 700 215/50's that I think I ruined by running under-inflated.

What tire/wheel arrangement were you looking at?

What tire inflation were you running? I run the stock wheel with Khumo Victoracers now. I'm looking at the Panasport 13x7 with Hoosier (on sale now) 225/50/13. I'm sick of being able to run as fast as any ITA car on the straights and losing seconds in the twisties.

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Paul Pineider
ITA 05 (Soudiv)

[This message has been edited by cpa7man (edited July 16, 2004).]

[mustanghammer]

I am using 13x7 Panasports - not sure of the backspace. They are a good lite weight wheel but they are a pain in the ass when it comes to tire mounting and dismounting. I used to bust tires at race tracks and always hated to see a setup Panasports. I usually service my own tires but when comes to mounting 225/45 Hoosiers I pay someone else to cuss my wheels.

I also have some Diamond 13x7 steel wheels for rain tires. They work okay, are not that much heavier than the Panasports and they are an excellent wheel to service. The negative with the Diamond wheel is that they are not hub-centric wheels and need to balanced using a fixture that locates the wheels by the lug holes. This information is on the Diamond wheels web site.

I have used stock wheels too and tires work better on 7" rims.

Scott



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Scott Peterson
KC Region
IT7 #17

[ddewhurst]

***They work okay, are not that much heavier than the Panasports***

Scott, my 13 x 7 x 4 inch backspace Panasports weigh 9 pounds. What is the weight of your Diamond 13 x 7 ?

Have Fun
David

[pgipson]

I use Panasports and Circle (aluminum) 13x7 with 4" backspacing on my Spec RX7. The steel Circles (Diamonds) that I have seen are quite a bit heavier than than the panasports or the aluminum Circles.

And there is little difference in price between the Panasports and Circle aluminums.

[Scott Nutter]

David my steel Diamond Racing Wheels are 13# each and only cost $60 each.

[cpa7man]

Thanks for the input.

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Paul Pineider
ITA 05 (Soudiv)

[ddewhurst]

Guys, I am aware that the Diamond's are heaver. When you forget about cost & someone says " not that much heavier than the Panasports" I need to say that's just like haveing a ITA car that weighs 44% more or 3427 pounds. I wish I could drive consistantly enough to say tha the 9 pound wheels were part of the equation.

Have Fun ;
David

[lateapex911]

I am with you Dave, wishing my driving would be capable enough to get teh most out of every tweak.

Wheels are an interesting thing. 4 or 5 pounds per wheel less to accelerate and brake is not inconsequential. I know there is software that can model the performance gain on certain cars, (not ours!), but any time we are talking about rotational weight, it is way more important than staic weight. Imagine losing 16 pounds off the flywheel...

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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]

paul, I have a set of panasports with 8 half life hoosiers im going to be selling next month, are you interested? make me an offer

Daryl

[Quickshoe]

Originally posted by ddewhurst:
...that's just like haveing a ITA car that weighs 44% more or 3427 pounds...

You don't really believe that, do you David? If so, you can put some 20# wheels on my car if you'll make your rx7 weigh 4000# and utilize panasports. Deal?


You need to factor in the weight of the entire assembly: wheel, tire, rotor, caliper, pads, bearings, ball joints, lug nuts, valve stem and half the weight of the LCA, brake line, steering arm and one end of the brake duct. The increase of 2-3 pounds of wheel weight isn't as huge as you imply. Yes, it makes a difference.

I had Diamonds when they offered the thin wall spun shell, with a thin center section which was not recommended for road racing, the 13 x 7 with 4" back space weighed less than 10#.

I bought 2 sets of Panasports for the FF, because the tires are extremely light, so the wheel is a bigger factor in the entire equation. The suspension components are light and the rear brakes are inboard.

[This message has been edited by Quickshoe (edited July 20, 2004).]

[ddewhurst]

" not that much heavier than the Panasports"

Quickshoe, strickly talking about difference between 13 pound Diamond & 9 pound Panasport including the thought process form above relative to weight. If 4 pounds don't matter here & there pretty soon the car is a way over weight. That was my only point.

Have Fun
David

[CaptainWho]

As some congressman from (I think) the 1950's once said: A billion here, a billion there. Pretty soon you're talking about _real_ money.

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Doug "Lefty" Franklin
NutDriver Racing

[dyoungre]

One more point which wasn't brought up, with anecdotal evidence: Stiffness. I raced with Diamond wheels, and replaced them with Revolutions. I was able to take almost a full degree of static camber out of the front to get the same temperature profile I had with the steel wheels; Handling, lap times also improved more than I ever imagined with the change. The conclusion that I made from my experience is that the stiffness improvement is as significant as the 16 lb unsprung weight reduction (running a 4.44 gear, that would be about 4 lb flywheel reduction

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Dave Youngren
NER ITA RX7 #61

[Quickshoe]

Originally posted by ddewhurst:
Quickshoe, strickly talking about difference between 13 pound Diamond & 9 pound Panasport including the thought process form above relative to weight. If 4 pounds don't matter here & there pretty soon the car is a way over weight. That was my only point.

Gotcha--agree can't ignore weight everywhere or you will end up with a way overweight car. I crew chief in a series (SCCA Rally Grp 5) where there isn't a minimum weight. Every decision revolves around: how light can you make it, yet still be strong enough vs. how much extra will it cost for how much performance advantage?

[lateapex911]

Originally posted by dyoungre:
..... Stiffness. I raced with Diamond wheels, and replaced them with Revolutions. I was able to take almost a full degree of static camber out of the front to get the same temperature profile I had with the steel wheels; Handling, lap times also improved more than I ever imagined with the change. ....

THAT is interesting, but coming from you (An automotive engineer) it makes a lot of sense...



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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]

[Quickshoe]

Originally posted by dyoungre:
...as significant as the 16 lb unsprung weight reduction (running a 4.44 gear, that would be about 4 lb flywheel reduction

I am not an engineer (which may be obvious in about 1 minute of continued reading). Please give me a 2 cent education on how the 16# unsprung weight reduction translates to a 4 lb flywheel reduction.

It seems to me you utilized the rear gear ratio as a multiplier to calculate the relative energy required to turn the flywheel vs spin the wheels. However, aren't we talking about MOI (not unsprung weight) and have to factor in all the diameters and weight of the entire wheel assembly? Further you are taking mass from the center of the wheel, not the OD which has a smaller effect on the MOI.

Do I have it all wrong?

Great point about the stiffness of the wheels.

[dyoungre]

You are right, quickshoe, that unsprung weight isn't necessarily rotational inertia, and yes, the 'moment of inertia' of any 3D object takes the moment arm into account - but a flywheel and wheel are roughly similar - in fact, the moment of inertia for a wheel may be higher, as there is so much metal out at the rim. In any case, as Jake alluded to, further proof of my occupation would be the poor writing style, as I jumped from one topic to the next within a single sentence.

Wheels are rotating at a speed that is a ratio of your engine speed (which, of course, changes based on what gear you are in). If 4th gear is 1:1, then the rotational speed of your wheels is simply your engine speed divided by your final drive ratio (which in my case is close to 4). Since you have to accelerate all 4 wheels as you accelerate the car, the amount of energy you are putting into wheels would be similar to 16 lbs of rotating mass / speed ratio (4) - or the same as lightening a flywheel by 4 lbs. The comment was meant more to be a friendly 'dig' at Jake.... I'm sorry to have confused you.

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Dave Youngren
NER ITA RX7 #61

[Quickshoe]

Thanks Dave, I am always trying to learn. I posted the questions, risking sounding like I am always quick to pick apart someone's claim to the effectiveness of certain "must have" goodies.

For clarification, regarding the MOI of the wheel I meant that reducing the weight of the rim didn't have a huge affect (effect? I am never sure if I get those correct) on reducing the MOI of the assembly as the wheel is more towards the center. 12# wheel and 25# tire, vs. 9# wheel and 25# tire.