Question for you 4.56 guys

[GrnBullitt08]

The highest speed I have trapped with my car with the 3.73s is 106. Im looking for around 112+

 

[Fast64ranchero]

I went from a best of 12.89 @ 110.12 w/a 1.99 60ft, corrected DA was 4100 feet with 3.73's to:
12.57 @ 110.36 w/a 1.82 60 ft with a corrected DA of 5071, the 4.56's hit the tire way harder, and my stock suspension had trouble planting the tires, so plan on Upper and lower control arms, I added UMI upper and lower CA's and the car hooks way better on the street, our track is close for winter so I'll have to wait till spring to see if the control arms helped the 60 foots.
one thing to keep in mind, 4.56's spin the drive shaft faster, if you have a vib problem, it will only get worse,

 

[tjm73]

I use ( RPM x tire height ) / ( gear ratio x 336 ) = MPH

 

[HEMI LOL]

I dont care about mpgs lol. I just wondered how high it'd spin on the hwy

 

[rojizostang]

with a tall tire, the 4.56's are easily street-able for a daily driver

 

[Mike K]

I'm also doing 4.56 this winter and I'm running a 28.5 tire so I'll be fine as a dd plus I'm working on beating my brothers 12.6 time in his nova

 

[iRoush]

Damn, and I'm worried about a jump to 4.10's from my 3.73s. But I travel 400 miles hwy every weekend.

 

[Mike K]

Yea but I plan on taking road trip from MN to AZ in the spring even with the gears

 

[3vs197]

the 4.56's will do nothing for your trap speed. 3.55 to 4.10's did nothing in trap for me. you et will get better only if you sixty foot drops. if you can launch harder but you will get to the finish line faster but you will not be going any faster.

 

[Fast64ranchero]

I use ( RPM x tire height ) / ( gear ratio x 336 ) = MPH

Same thing 168 X 2 = 336, difference is tire height 1/2 vers whole, both work good...

 

[06whipple]

For accurate numbers here ya go. Assuming 1:1 tranny ratio take rpm divided by rear gear ratio (3.73, 4.1, etc) times loaded tire circumference (5280 times 12 divided by manufacturers revs per mile) divided by 1056 (converts mph to inches per minute) to get mph. To go from mph to rpm take the mph times 1056 divided by loaded tire circumference times gear ratio. If you don't know revs per mile there is a chart on Mickey Thompsons website that gives you revs per mile based on tire height (it's pretty damn close) or you can measure from pavement to center of wheel multiply by 2 multiply by pi (3.14159). If not in 1:1 tranny ratio do this...going from rpm to mph take rpm divided by tranny ratio (3.3, 2.1, 1.3, .675, etc) then rest of formula...going from mph to rpm at the end of the formula you would multiply by the tranny ratio.

 

[GrnBullitt08]

As long as I get there faster....

 

[tjm73]

For accurate numbers here ya go. .....

This brings up a question I've always had. How accurate a number do you really need when calculating rpm vs. gearing vs. tire size?

Even if your rpm estimation is 200 rpm different between different calculating methods will it really matter much in the real world?

 

[06whipple]

This brings up a question I've always had. How accurate a number do you really need when calculating rpm vs. gearing vs. tire size?

Even if your rpm estimation is 200 rpm different between different calculating methods will it really matter much in the real world?

Not sure but I like to be as accurate as possible when calculating something

 

[8306gt]

This brings up a question I've always had. How accurate a number do you really need when calculating rpm vs. gearing vs. tire size?

Even if your rpm estimation is 200 rpm different between different calculating methods will it really matter much in the real world?

It doesn't really matter for daily driving but if you are taking the car to the track it could be the difference in running out of gear or having to change the rpm limiter to a higher rpm than you had planned to run. With my car running 4.30's, I had planned to limit rpm to 6500 (to limit boost) after the blower install, however I was bumping the 6500 limiter thru the traps and had to up it to 7200 to make a clean pass. Keep in mind also that trap speeds on your time slip are an average mph not the max mph you see exiting the traps.

 

[06whipple]

The only part that is important for daily driving is using correct revs per mile so your speedometer reads correct