Going from 275radial to 30x9 ?

Tex013 · 07-21-2014, 05:52 PM

thanks for the replies ,
I was looking at either the 18209C06 or 18210C07 tyre
I may not quite get 18211 or 18212 into the stock wheel well
thanks,

Tex

Dave Noll · 07-23-2014, 01:00 AM

Assuming good traction, a change to a 30 inch tall tire would require roughly a 4.4 gear to turn the engine the same RPM, so if you can take a little more RPM a 4.56 gear should work nicely. & be quicker. (depending on your powerband)

Tex013 · 07-24-2014, 05:56 PM

thanks Dave,
funny as it seems I only shift at 6000,trap around 63/6400. not sure of pulling harder with the rods(ly with ARP bolts),peak power on chassis dyno is around 5500 but pulls happily to 6500 never went past here
I did used to run 3.9 gears with the 28"
as to quicker with more gear - car is able to run faster than the class

Tex

Dave Noll · 07-25-2014, 01:32 PM

Well if your peak is 5500 & you figure 5% past peak for a trap then your current gear should be correct. But just putting a taller tire on what you have your 60' will be slower but the motor will be happier in the light's. test, test, test.

Tex013 · 07-25-2014, 11:25 PM

Thanks Dave,
Wiil check with hoosier for age of 30x9 slicks i have
Then off to test

Tex

Tex013 · 08-04-2014, 06:04 PM

Dave ,
just an update . Tested on Saturday .
You were right re gearing it did feel a little soft through the top end .
But the 60 wasn't that much different to talk about .1.542/1.541/1.532/1.543
I was wrong in that I didn't pick up any MPH .
I back to backed the 30x9 against the 275 both Hoosier radials , the 30x9 is several years ,maybe 5 or 6 , old and the 275 about 55 passes and gone after the last pass .
the 30x9 went 6.920/919 @98.71/98.59MPH( 1/8")10.936/942@121.07/120.93MPH . 733/794 DA
the 275 went 6.880/886@99.14/99.30MPH(1/8") 10.881/884@121.85/121.90 MPH. 387/405DA
Car obviously likes a little more gear
thanks again,

Tex

07-21-2014, 05:52 PM	#1
Tex013 Junior Member Join Date: Oct 2012 Location: Sydney , Australia Posts: 97 Likes: 23 Liked 43 Times in 25 Posts	Re: Going from 275radial to 30x9 ? thanks for the replies , I was looking at either the 18209C06 or 18210C07 tyre I may not quite get 18211 or 18212 into the stock wheel well thanks, Tex

07-23-2014, 01:00 AM	#2
Dave Noll Senior Member Join Date: Nov 2007 Location: Div. 6, Eastern, WA Posts: 709 Likes: 2,666 Liked 238 Times in 111 Posts	Re: Going from 275radial to 30x9 ? Assuming good traction, a change to a 30 inch tall tire would require roughly a 4.4 gear to turn the engine the same RPM, so if you can take a little more RPM a 4.56 gear should work nicely. & be quicker. (depending on your powerband) __________________ Dave Noll, EF/S ,?/SA 6526

07-24-2014, 05:56 PM	#3
Tex013 Junior Member Join Date: Oct 2012 Location: Sydney , Australia Posts: 97 Likes: 23 Liked 43 Times in 25 Posts	Re: Going from 275radial to 30x9 ? thanks Dave, funny as it seems I only shift at 6000,trap around 63/6400. not sure of pulling harder with the rods(ly with ARP bolts),peak power on chassis dyno is around 5500 but pulls happily to 6500 never went past here I did used to run 3.9 gears with the 28" as to quicker with more gear - car is able to run faster than the class Tex

07-25-2014, 01:32 PM	#4
Dave Noll Senior Member Join Date: Nov 2007 Location: Div. 6, Eastern, WA Posts: 709 Likes: 2,666 Liked 238 Times in 111 Posts	Re: Going from 275radial to 30x9 ? Well if your peak is 5500 & you figure 5% past peak for a trap then your current gear should be correct. But just putting a taller tire on what you have your 60' will be slower but the motor will be happier in the light's. test, test, test. __________________ Dave Noll, EF/S ,?/SA 6526

07-25-2014, 11:25 PM	#5
Tex013 Junior Member Join Date: Oct 2012 Location: Sydney , Australia Posts: 97 Likes: 23 Liked 43 Times in 25 Posts	Re: Going from 275radial to 30x9 ? Thanks Dave, Wiil check with hoosier for age of 30x9 slicks i have Then off to test Tex

08-04-2014, 06:04 PM	#6
Tex013 Junior Member Join Date: Oct 2012 Location: Sydney , Australia Posts: 97 Likes: 23 Liked 43 Times in 25 Posts	Re: Going from 275radial to 30x9 ? Dave , just an update . Tested on Saturday . You were right re gearing it did feel a little soft through the top end . But the 60 wasn't that much different to talk about .1.542/1.541/1.532/1.543 I was wrong in that I didn't pick up any MPH . I back to backed the 30x9 against the 275 both Hoosier radials , the 30x9 is several years ,maybe 5 or 6 , old and the 275 about 55 passes and gone after the last pass . the 30x9 went 6.920/919 @98.71/98.59MPH( 1/8")10.936/942@121.07/120.93MPH . 733/794 DA the 275 went 6.880/886@99.14/99.30MPH(1/8") 10.881/884@121.85/121.90 MPH. 387/405DA Car obviously likes a little more gear thanks again, Tex