Effect of rotational mass on power (tire and wheel size and weight)

[SoftBatch]

I have put this up on a few forums and thought I would add it here. I think it is some very helpful info.

If your going to be running SCCA in the FS class then you have to stay with the rim sizes available from the factory.

Dave Schotz, the guy that won FS in '04 ran on bogart race wheels 17x8 on his mach 1 with 275/40/17 Kumho Ecsta V710. Also running this size tire with 3.55 gears would equal 3.76 gearing. This would be great if it were only a track wheel and tire since the speedo could not be recalibrated at least not in the 05 because you cannot change computer settings.http://sccaforums.com/forums/57319/ShowPost.aspx

Stock rims are 21.6lbs if you dropped that to say 14.5 or the SSR Competition 17x8 wheels it would be like adding 25rwtq(at least according to the spread sheet I found for the loss in weight).
This article has the spread sheet look at the updated one. I am trying to add in drive shaft specs on it right now. Does anyone know the stock weight and size of the stock 05 Mustang GT flywheel, and drive shaft?
http://www.mazda6tech.com/Articles/Mainten...id=16&Itemid=50

If you go up to ESP you can run any size wheels you want. When I move up I will be sticking with a 17x9 or 17x10 rim and probably trying to get a set of bogart light racing wheels to add that extra power or at least keep the weight the same.

That mazda6 website has a lot of good info that I couldn't find anywhere else shy of asking a race team.

 

[10thTerminator]

Very Cool

 

[SoftBatch]

After I get another set of wheels I am going to put this to the test and see what power is added.

Another Idea would be to take some 1lbs metalic weights and put them on the wheels (obviously at equal points along the wheel to ensure no vibrations) This would allow someone to find out the differences with out having to buy a new set of wheels.

 

[99COBRA2881]

The rule of thumb that I have heard is that "Removing 1lb of rotational mass is equivalent to removing 6lbs from the vehicle."

Good Post, I need to get rid of these heavy 17X9 cobra R replicas and move to a lighter rim, right now with 275/40 Kumho MXs each wheel/tire combo weighs approx 50lbs on a bathroom scale, I weighed myself and it was accurate. Seems very heavy, anyone else weighed their wheels/tires?

 

[SoftBatch]

The rule of thumb that I have heard is that "Removing 1lb of rotational mass is equivalent to removing 6lbs from the vehicle."

Good Post, I need to get rid of these heavy 17X9 cobra R replicas and move to a lighter rim, right now with 275/40 Kumho MXs each wheel/tire combo weighs approx 50lbs on a bathroom scale, I weighed myself and it was accurate. Seems very heavy, anyone else weighed their wheels/tires?

All sizes being equal as far as wheels and tire go that seems to be the case according to the spreadsheet. I have also hear that from other sources.

Remember Chrome adds a few lbs to the wheel weight too

 

[RAT]

The stock wheel & tire combo on a Mach 1 = 50 lbs.

stock 17x8 wheel = 26 lbs
245/45 Gatorbacks = 24 lbs

My autox tires weight 25 lbs each + the 17x8 wheel 20 lbs = 45 lbs

Thoughs 275 Kumho MX's weight 28 lbs each + 17x9 Cobra R rep's 22 lbs = 50 lbs

The wheels aren't that heavy, it's the tires. I saw some Avon Tech M500's in 245/45/17 size at 28 lbs. Same size as the stock Mustang tires but 4 lbs more per corner. ouch! The M500's may have a little more grip (forward bite) than the Gatorbacks but the weight difference will make you think there's a big difference.

 

[SoftBatch]

I am hoping to get some 15lbs Forged Wheels and some Nitto NT-01s

 

[fastbird86]

I looked up some wheels for my car, WedsSport makes a 17x9 at 17.5 lbs. at about $340, still looking though to see what I can find.

 

[thefrush]

My track wheels/tires are 7 pounds lighter at each corner than my street set-up. Killer. :thumbsup:

 

[Lethalchem]

From my experience with autocross, the cars are already making plenty of power. You talk of adding 25lbs ot torque, etc, but I don't see the need for it. We've already got much more than we can use in a parkinglot. I'm not sure sure the minimal gains of 5 or 10 lbs is really worth all that much. I could be wrong though.

 

[WPGFORDGUY]

From my experience with autocross, the cars are already making plenty of power. You talk of adding 25lbs ot torque, etc, but I don't see the need for it. We've already got much more than we can use in a parkinglot. I'm not sure sure the minimal gains of 5 or 10 lbs is really worth all that much. I could be wrong though.

I agree


Unless your planning on going to Topeka and / or until your driving skill surpasses your car's ability, it's all irrelavant.

I am hoping to get some 15lbs Forged Wheels and some Nitto NT-01s

I'd love to hear what you think of the Nittos, I'll need to replace my V700's aftter Evo School...

 

[SoftBatch]

Lol, I'm going back and forth on the Forged wheels. I may have a sponsorship(very Iffy) for the wheels so that would be the reason I go with them otherwise I am going to get an extra set of stock '05 Wheels.

I will let you know about the Nittos, I'll be using them for the first half of this year for AutoX and then hopefully switching to V710s at the divisional event held in June.

I am going to try to get to a phase 1 and 2 Evo school before then as well as my local clubs driving school.

 

[Lethalchem]

I don't have a lot of experience with race rubber, but I used Nitto 555 RII's for the first time on a road course earlier this year, and simply LOVED them. It was a completely different car. They probably arn't as good as some of the other brands, but they seem to have a little better treadlife.

 

[fastbird86]

I agree


Unless your planning on going to Topeka and / or until your driving skill surpasses your car's ability, it's all irrelavant.

And thats what I plan to do, one day. I am gonna try to make it to the National Tour event in Houston in '06 and would like to be somewhat compedative.

 

[99COBRA2881]

Finally, I'm close to something! Topeka is an hour and a half away from me on I-70. Seems I only get to hear about events that are half the country away. Cant wait to go watch the '06 Runoffs.

Only thing to be weary of with the ultra lightweight rims is that I've heard they can bend easily if you go off track and hit anything. Just check with the rim manufacturer before you buy.