new address for the "gear calculator"

[Marv S]

new address for the \"gear calculator\"

Easy to use tool to check the effects of different rear gears in the Viper has been moved to

http://chuckware.net/viper/gears.asp

 

[Jack B]

Re: new address for the \"gear calculator\"

Marv:

I have been using the Unitrax calculator prior to seeing this post. I ran some numbers with your calculator and compared them to the Unitrax and there seemed to be a huge difference. I ran 6000 rpm's (25.4") with 3.33's and came up with 144.7 (Unitrax) and 136 Chuck). Where is the error?

 

[J DAWG]

Re: new address for the \"gear calculator\"

I am assuming 25.4 is the stock tire size?

 

[Jack B]

Re: new address for the

J Smith:

In Marv's calculator if you hit the manual button the tire size defaults to 25.4. I measured my pilots and it was almost exact.

 

[Marv S]

Re: new address for the \"gear calculator\"

Good Catch. In theory the unitrax calculator is on but in the real world of Vipers, the chuckware site is the one to use. If you calc out a 335*35*17 tire it should measure 26.23". But go measure that rear tire and it is even LESS than 26". It measures closer to the 25.4" listed in the http://chuckware.net/viper/gears.asp calculator.

I wondered about this 3 years ago and asked a guy who knows wheels & tires, John Purner, why the big difference and his reply was:

tire manufactures prerogative, they should spec higher, but most manufactures just widen the 315 35 mold, hence the less than calculated OD. john

Bottom line, measure the tire, either run a cloth tape around the od/3.14 or just measure the standing diameter because that sidewall won't always calculate out to what the tire really is.

a btw... at HIGH speeds like an open road race silverstate run can cause the tire to narrow a bit and the diameter to get a bit larger.

the reference numbers are: [*]335*35*17 mxx3 tire using 1" = 25.40005mm
[*]335mm/25.40005 = 13.19" (wide)
[*]13.19" * .35 = 4.62 (wide * aspect ratio = sidewall)
[*]4.62" + 4.62" + 17" = 26.23" diameter (sidewall + sidewall + rim)
But it measures way less than even 26"

 

[Jack B]

Re: new address for the \"gear calculator\"

Marv:

I am using the same tire diameters. Believe me I like your calculator better. In support of the Unitrax calculator, the 149-150 mph quarter mile cars are finishing in fourth. That supports the Unitrax calculator. Your calculator would have them in fifth.

 

[Marv S]

Re: new address for the \"gear calculator\"

I really like Unitrax and have heard only good comments on their work but there is a glitch in that gear program and it’s kind of tough to troubleshoot it without seeing their formula..

I’ll walk you through the math and use 25.4" as the tire size:

25.4" tire diameter * pi = 79.7964368" covered each time the tire rotates

79.7964368"/ 3.07 gears = 25.99232469" covered each rotation of the driveshaft

6,000(rpm) * 60(min) * 25.99232469" = 9,357,236 inches per hour

9,357,236 / 12 = 779,770 feet per hour

779,770 / 5280 = 148 miles per hour

I don't know why the Unitrax calculator comes up with 156.98 mph when inputing 6,000 rpm; 25.4" tire; and 3.07 gear.

There is another site with a very nice gear calculator you can work with a bit. It gets the same results as the one at chuckware.net. Check it out at: http://www.f-body.org/gears/

Question: what size tires are the 149-150 mph quarter mile cars running? Are they street tires? But even with street tires you should see over 150 mph in 4th before the cut-off kicks in. I was there several times a few weeks ago.

Also, I’d like to take credit for such a nice Viper gear site, but it was developed by Gary, an owner from the East Coast that used to host it at Orbit. Gary moved it to the Chuckware.net site and I was just giving people a heads-up as they would get a dead link for it at the old Orbit site.

 

[Paolo Castellano]

Re: new address for the \"gear calculator\"

Marv, thanks for the updated link. I have emailed orbit development several times looking for why the old link will not work. It is so tedious to do it by hand. Paolo