Special Periodic Award Fun Question, 11-27-2010

Good Day All!

As a Christmas gift to the site, I am donating $100.00 that will be shared with the administration of the site and the “winner” of this Special Fun Question.

The question for this "Special Award" is open for ALL members except for the Administrators (Yes, 72HCODE you can participate in this one). The first person to send a PM to Rocketfoot and me with the correct response will “win” $50, a nice Number 1 Icon, AND a VIP membership ($25 value). If the “winner” is already a VIP member¸ he or she will have a $75 postal money order sent to them. In any case, the additional $25 will be donated to the site (in the "Winner's name) to assist with administrative costs.

The scenario:

You are the PROUD owner of a 1973 Mustang with a 351C 4V, top loader transmission and standard rear end gearing. While you have tried to keep the car “stock”, you recently upgraded to a Competition Cams Roller (#284HR) camshaft and have now decided to upgrade your wheels and tires to 17 inches and BF Goodrich G-Force T/A Drag Radials.

The question is:

What size tires should you purchase to take the best performance advantage (120 MPH top end) for your new camshaft? Your response must include your rationale (or method) used in making the determination.




Since this question requires some specific knowledge and math skills, I believe it has a level of difficulty. With that in mind, I will leave the question "UP" past the 7:00 PM (CST) Monday cutoff when I normally post the results if a correct response is not received by that time. In any case, I will provide periodic updates on this thread until a correct response is received.

Please keep in mind that this is a two-part question with the rationale (or method) used to determine the size of the tires being the most important. A "guess" as to the size of the tires (in and of itself) will not make the cut.

Good Luck!!

BT

Good Day All!

We have received four (4) responses to this Periodic Fun Question and I am amazed as among those were two (TNFASTBK and JORGEM2) with the correct responses. As the first to provide his response, TNFASTBK is the winner.

For the record, this question was designed primarily to assist a hobbyist in making a determination as to what tires to use to meet a specific performance expectation.

To recap, the scenario:

The owner of a 1973 Mustang with a 351C 4V, top loader transmission and standard rear end gearing is attempting to keep the car “stock” but has made an upgrade through a Competition Cams Roller (#284HR). The owner has decided to upgrade wheels and tires to 17 inches and BF Goodrich G-Force T/A Drag Radials.

The question is:

What size tires should be purchased to take the best performance advantage (120 MPH top end) for the new camshaft? Correct response should include rationale (or method) used in making the determination.




There are actually mathematical formulas that will bring one to the “correct” response. In order to provide the correct desired response, one has to first determine the “unknowns” which are:

-What is the maximum RPM of the camshaft involved (5500, per Comp Cams description)

-What is the standard gear ratio of a 1973 351C 4V Mustang with a top loader (3:50)

Armed with this information, we can now utilize a formula for making a determination as to the size of the needed tire. One formula is:

TD=MPH X GR X336 ÷ RPM

This equates to the following:

TD=120 X 3.50 X 336 ÷ 5500 = 25.658

According to BF Goodrich, their 17” G-Force Radial which matches this diameter is the 275/40R.

Of the two correct responses received, TNFASTBK was the first to submit an acceptable response along with an acceptable explanation as to how he arrived at that response. TNFASTBK utilized a slightly different formula, however he arrived at the same conclusion. See Following:

According to the BF Goodrich website they are only offered in 3 sizes 17's


g-Force T/A™ Drag Radial


P225/45R17


P275/40R17


P315/35R17

 


I would go with the P275/40R17

 


Explanation of why:

 


Comp Cam 284hr Max Rpm of 5500


axle ratio of 3.50 standard Axle code A


Top loader 4th gear ratio=1


mph=120

 


TIRE RADIUS = 168 x MPH x GEAR RATIO ÷ RPM

 


168 x 120 x 3.5 / 5500 = 12.82

 


Tire radius X 2 = Diameter

 


12.8 X 2 = 25.66

 


Convert P-Metric Tire to Inch Size


275/40= Diameter of 25.66 width of 10.8267


Unquote




My SINCERE congratulations Roy, as you REALLY outdid yourself on this one!! I will be contacting you via PM relative to your monetary award.

I would also like to commend JORGEM2, HEMIKILLER, and MAIDEN DEARBORN who took valiant “stabs” at the question.

BT

Click to expand...

Congratulations, Roy!

And how about a big round of applause for BT, our knowledgeable and generous quiz master! Thanks for taking the time, effort and occasional financial investment to make this happen!

Congratulations, Roy!

And how about a big round of applause for BT, our knowledgeable and generous quiz master! Thanks for taking the time, effort and occasional financial investment to make this happen!

Click to expand...

YEAH CLAP CLAP CLAP CLAP YOU ARE THE MAN::goodjob::

As one of the responders, I now know what I am up against. Wow, I'm glad you guys are on our side. Great work and keep it up.

i can't compete by the time i log in the contest is over LOL

MAIDEN DEARBORN and 72HCODE,

Believe me, I feel your pain!!

I would have thought this question would have lasted for at least a week or so. As has been said before, we have some very EXPERIENCED people on this site who have expressed REAL interest in the Site's success.

I may have to pull out "all the stops" on future questions ! I will continue to try and consistently post the "Weekly" question at approximately 7:00 PM (EST) on Saturdays.

Thanks again for everyone's participation and interest.

BT

Ha! Got the right answer but didn't show my work...

Feels kinda like school all over again!

Won't happen again!

TN caught me sleeping on the line.

We have received four (4) responses to this Periodic Fun Question and I am amazed as among those were two (TNFASTBK and JORGEM2) with the correct responses. As the first to provide his response, TNFASTBK is the winner.

Nice math

Congrats and a round of applause to everyone who reads these threads. As BT alluded, we've got some very talented and very wise people in this club. Glad to be a part of it.

Doc