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DRR Sportsman
Picture of diceman1530
posted
With the M/T tires being so tall is anyone switching to a 4.30 gear. I know they don’t grow like a Hoosier. Most races are 1/8 mile now and I don’t think it would be that much more rpm in a 1/4 mile race. Thanks


Working for the Weekend!!!!
Fordyce Motorsports
 
Posts: 248 | Location: Williamstown, NJ | Registered: November 20, 2009Reply With QuoteReport This Post
DRR S/Pro
Picture of David Covey
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I would think it would depend on power level, also if you are in the sweet spot with a shorter tire then more gear with a taller tire would keep you there..

I've went from 4.30-4.11-3.90 with the bubba's. Still with the 3.90 and now big Bubba. Last weekend it went .981 60' with some additional power to get rid of a little tire shake.

Dave


"It is usually futile to try to talk facts and analysis to people who are enjoying a sense of moral superiority in their ignorance." -Thomas Sowell
 
Posts: 3290 | Location: American By Birth Texan By The Grace Of God  | Registered: April 29, 2004Reply With QuoteReport This Post
DRR Pro
Picture of TORQIN
posted Hide Post
All 3 of my dragsters have 4.30 gears...
 
Posts: 1749 | Location: Houston, Tx. | Registered: November 27, 2008Reply With QuoteReport This Post
DRR Sportsman
Picture of diceman1530
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quote:
Originally posted by TORQIN:
All 3 of my dragsters have 4.30 gears...



What rpm do you run in 1/4 ?


Working for the Weekend!!!!
Fordyce Motorsports
 
Posts: 248 | Location: Williamstown, NJ | Registered: November 20, 2009Reply With QuoteReport This Post
DRR Sportsman
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4.30 gear on both cars with 3190W tires. One running 4.50s and other running 4.80s
 
Posts: 783 | Location: Georgia | Registered: May 09, 2008Reply With QuoteReport This Post
DRR Pro
Picture of Alaskaracer
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4.10's here. 3196 mickeys.


Mark Goulette
Owner/Driver of the Livin' The Dream Racing dragster
www.livinthedreamracing.com
"Speed kills but it's better than going slow!"
Authorized Amsoil Retailer
 
Posts: 1462 | Location: Back home in Alaska! | Registered: February 13, 2011Reply With QuoteReport This Post
DRR Top Comp
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162 mph and down (lower) will cross @ 7000 or down (lower) with 9% converter slip and 10% tire growth 34-35 diameter tire 1/8 mile, these are conservative percentages at 162mph.

I'd be thinking 1.64 low with a 4.56 if I ran 1/8 mile exclusively at around 165-170mph. That would make it hustle when put it in high gear. 6% slip and 10% growth crossing 7300 @170mph. 35

1.64 x 4.56 = 7.47
1.80 x 4.30 = 7.74
1.80 x 4.10 = 7.38

This message has been edited. Last edited by: Mike Rietow,
 
Posts: 9398 | Location: Madeira Beach Fl. | Registered: June 12, 2018Reply With QuoteReport This Post



DRR Trophy
Picture of NC3x58
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quote:
Originally posted by Mike Rietow:
162 mph and down (lower) will cross @ 7000 or down (lower) with 9% converter slip and 10% tire growth 34-35 diameter tire 1/8 mile, these are conservative percentages at 162mph.

I'd be thinking 1.64 low with a 4.56 if I ran 1/8 mile exclusively at around 165-170mph. That would make it hustle when put it in high gear. 6% slip and 10% growth crossing 7300 @170mph. 35

1.64 x 4.56 = 7.47
1.80 x 4.30 = 7.74
1.80 x 4.10 = 7.38


Was just talking about this with a group of buddies.. If you took a car that has a 1.80 first gear PG, 4.30 gear and little bubba tires and switched it to a 1.69 first gear, 4.56 and left the tire the same, using the Wallace calulator for starting line ratio, first gear would essentially be the same (I got 7.74 vs 7.71) and then you would gain more mph in high gear, would make a good 1/8 mile setup for typical bracket dragsters IMO


Nick Craig

1971 Camaro Split Bumper
376ci LS3
 
Posts: 410 | Location: Ohio | Registered: December 28, 2013Reply With QuoteReport This Post
DRR Trophy
Picture of NC3x58
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To the OP, I went from a 33.5/16/15 (M/T 3084S) with non-beadlocks and a 4.10 gear to the Little bubba with beadlocks and 4.30 gear and for the most part lost zero ET. Most of the guys around N.E. Ohio run 4.30 gear in their bracket dragsters, mostly 1/8 anymore.


Nick Craig

1971 Camaro Split Bumper
376ci LS3
 
Posts: 410 | Location: Ohio | Registered: December 28, 2013Reply With QuoteReport This Post
DRR Top Comp
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You can also go 200 mph 1/4 mile crossing 7500 rpm with a 4.30 gear, converter slipping five percent,35" M/T tire growing fifteen percent. I'd have a 1.64 low gear in that instance as well.

This message has been edited. Last edited by: Mike Rietow,
 
Posts: 9398 | Location: Madeira Beach Fl. | Registered: June 12, 2018Reply With QuoteReport This Post
DRR Top Comp
posted Hide Post
quote:
Originally posted by NC3x58:
quote:
Originally posted by Mike Rietow:
162 mph and down (lower) will cross @ 7000 or down (lower) with 9% converter slip and 10% tire growth 34-35 diameter tire 1/8 mile, these are conservative percentages at 162mph.

I'd be thinking 1.64 low with a 4.56 if I ran 1/8 mile exclusively at around 165-170mph. That would make it hustle when put it in high gear. 6% slip and 10% growth crossing 7300 @170mph. 35

1.64 x 4.56 = 7.47
1.80 x 4.30 = 7.74
1.80 x 4.10 = 7.38


Was just talking about this with a group of buddies.. If you took a car that has a 1.80 first gear PG, 4.30 gear and little bubba tires and switched it to a 1.69 first gear, 4.56 and left the tire the same, using the Wallace calulator for starting line ratio, first gear would essentially be the same (I got 7.74 vs 7.71) and then you would gain more mph in high gear, would make a good 1/8 mile setup for typical bracket dragsters IMO



("774") Ratio's get even better if you have the power. Sonnax manufactures a 1.58, TSI a 1.64 low rated at the least, to 2000hp. Less efficient converter early for boost if you have a super charger, in low. More efficient converter less rpm (boost) drop back when you put it in high, it'll hustle. Decelerate better too, more efficient converter closer to one with engine rpm at the stripe, to kill. That's what id be think'n 1/8 or 1/4 super charger, N/A or nitrous. Hitting the brakes at 200 plus mph ain't gonna be a long lasting option, for long at least, I wouldn't imagine. I could be wrong on that though, I suppose.
 
Posts: 9398 | Location: Madeira Beach Fl. | Registered: June 12, 2018Reply With QuoteReport This Post
DRR S/Pro
Picture of Lenny5160
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I've been having this debate for the upcoming season. My car has always had a 4.10 gear and always a 33.5 tire.

I really want to go to a 34.5 or 35 tire, and I want to replace the gear set in the car due to age. I can either stick with the 4.10 and lose about 4% gear ratio, or change to a 4.30 and gain about 1%. This is using 106 and 110 as the respective circumferences, right off the Hoosier spec chart. I'm not sure how real-world measurements and growth will affect it.

I'm really happy with how the car works, but it needs tires and I like the idea of a little more ground clearance and like how the tall tires look.

The car is mostly used for Super Comp on the quarter mile, with just a couple 1/8 mile bracket races per year.


Tony Leonard
 
Posts: 3135 | Location: Inver Grove Heights, MN | Registered: March 18, 2004Reply With QuoteReport This Post
DRR Sportsman
Picture of sc4087
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I've always run 4.30's in my bracket cars. Only car doesn't have 4.30 in it is my T/D car


Mike Greene




 
Posts: 509 | Location: Burleson, TX | Registered: March 23, 2007Reply With QuoteReport This Post
DRR Top Comp
posted Hide Post
quote:
Originally posted by Lenny5160:
I've been having this debate for the upcoming season. My car has always had a 4.10 gear and always a 33.5 tire.

I really want to go to a 34.5 or 35 tire, and I want to replace the gear set in the car due to age. I can either stick with the 4.10 and lose about 4% gear ratio, or change to a 4.30 and gain about 1%. This is using 106 and 110 as the respective circumferences, right off the Hoosier spec chart. I'm not sure how real-world measurements and growth will affect it.

I'm really happy with how the car works, but it needs tires and I like the idea of a little more ground clearance and like how the tall tires look.

The car is mostly used for Super Comp on the quarter mile, with just a couple 1/8 mile bracket races per year.


"Real world growth" There's an equation. Gear,rpm, Mph, converter slip at the stripe and Tire part #, is the input. They grow more than you might think, 10% to 20% depending on the MPH.
 
Posts: 9398 | Location: Madeira Beach Fl. | Registered: June 12, 2018Reply With QuoteReport This Post



DRR S/Pro
Picture of Lenny5160
posted Hide Post
quote:
Originally posted by Mike Rietow:
quote:
Originally posted by Lenny5160:
I've been having this debate for the upcoming season. My car has always had a 4.10 gear and always a 33.5 tire.

I really want to go to a 34.5 or 35 tire, and I want to replace the gear set in the car due to age. I can either stick with the 4.10 and lose about 4% gear ratio, or change to a 4.30 and gain about 1%. This is using 106 and 110 as the respective circumferences, right off the Hoosier spec chart. I'm not sure how real-world measurements and growth will affect it.

I'm really happy with how the car works, but it needs tires and I like the idea of a little more ground clearance and like how the tall tires look.

The car is mostly used for Super Comp on the quarter mile, with just a couple 1/8 mile bracket races per year.


"Real world growth" There's an equation. Gear,rpm, Mph, converter slip at the stripe and Tire part #, is the input. They grow more than you might think, 10% to 20% depending on the MPH.


The growth doesn't really matter unless there is a significant difference in growth between the two different size tires. The bigger concern is probably the actual measured circumference of the 33.5 and 34.5 tires.


Tony Leonard
 
Posts: 3135 | Location: Inver Grove Heights, MN | Registered: March 18, 2004Reply With QuoteReport This Post
DRR Top Comp
posted Hide Post
105.19 vs 108.33

The equation to figure roll out at the stripe, is the more pertinent observed number to know,for performance. No matter the roll out (33.5, 34, 35) sitting on the starting line. A trend more accurately forecasts any given adjustment.

This message has been edited. Last edited by: Mike Rietow,
 
Posts: 9398 | Location: Madeira Beach Fl. | Registered: June 12, 2018Reply With QuoteReport This Post
DRR S/Pro
Picture of Lenny5160
posted Hide Post
quote:
Originally posted by Mike Rietow:
105.19 vs 108.33

The equation to figure roll out at the stripe, is the more pertinent observed number to know,for performance. No matter the roll out (33.5, 34, 35) sitting on the starting line. A trend more accurately forecasts.


Well thanks for doing 3.14 x 33.5 and 34.5, Mr Wizard! Not quite the same as putting a tape around a mounted and pressurized tire.


Tony Leonard
 
Posts: 3135 | Location: Inver Grove Heights, MN | Registered: March 18, 2004Reply With QuoteReport This Post
DRR Top Comp
posted Hide Post
quote:
Originally posted by Lenny5160:
quote:
Originally posted by Mike Rietow:
105.19 vs 108.33

The equation to figure roll out at the stripe, is the more pertinent observed number to know,for performance. No matter the roll out (33.5, 34, 35) sitting on the starting line. A trend more accurately forecasts.


Well thanks for doing 3.14 x 33.5 and 34.5, Mr Wizard! Not quite the same as putting a tape around a mounted and pressurized tire.


You can put a tape around the 33.5's at the stripe with the input. For the purpose of a trend that'll forecast any given adjustment. Or remain "not sure". It don't matter to me either way. If I were you I'd leave it the way it is, If I'm a "wizard" in your eye's for lending a hand, and you're "not sure".

It's not a subjective matter.

This message has been edited. Last edited by: Mike Rietow,
 
Posts: 9398 | Location: Madeira Beach Fl. | Registered: June 12, 2018Reply With QuoteReport This Post
DRR S/Pro
posted Hide Post
Here's the magic formula Big Grin

MPH = (RPM x TD)/GR x 336 Or TD = (MPH x GR x 336)/RPM

where:
MPH = Car's speed at finish line - See time slip! LOL
RPM = driveshaft speed at finish line
TD = Tire Diameter (inches)@ finish line
GR - Gear Ratio
336 = constant to converter units

So you need a data logger to get DS RPM or if you don't have one then you would have to guess at converter slip at the finish line and use engine RPM instead.
So 7000 RPM (engine speed at stripe w/8% slip)
7000/1.08 = 6481.5 DS RPM's
 
Posts: 2125 | Location: Tewksbury, MA,USA | Registered: November 03, 2000Reply With QuoteReport This Post
DRR Sportsman
Picture of 369dragster
posted Hide Post
quote:
Originally posted by diceman1530:


What rpm do you run in 1/4 ?



Ray I have 4:30's in my car and go thru at 7850 in good air going 7.0's


Ken
 
Posts: 319 | Location: Massachusetts | Registered: March 15, 2007Reply With QuoteReport This Post
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