getusumws6

iTrader: (9)

went to the track after changing tire sizes from a 26" 275/50/15 to a 28" 275/60/15 mt dr. figuring I would mile an hour a little better and did just the opposite. went from a consistant 11.9x to a 12.3xx and from 114mph to 109mph. i guess its time to change gear ratio in the 9" to a 4.11 or 4.30 (i have a 3.70 btw). alittle disapointed in a way,but gears are cheaper than a new set of mt dr's.

dlove

iTrader: (23)

have you da corrected both runs to use a control to see the real difference.

post the track name/zip/date/time and i will do it if you want

getusumws6

iTrader: (9)

the air was at 3200ish. KCIR 6/4/2008 7pm-9pm , track temp was 101* and the car was dead hooking. played with the suspention for a bit but all the runs were carbon copy of each other. i'm doing some math with my 60's and 330's to see whats up.

dlove

iTrader: (23)

i didnt even notice you are local. kcir is 798' up

what is the date for the other run?

getusumws6

iTrader: (9)

may 10th 2008 same track 10:30 to 11:30 am, the last time i went to the track anyways. and thanks for any insight and help you are providing.

dlove

iTrader: (23)

last night was not good lol

with new tires 28
Density Altitude = 3228 feet ET MPH
Uncorrected 12.3 @ 109
Corrected 11.83 @ 113.2

with old tires 26
Density Altitude = 1187 feet ET MPH
Uncorrected 11.9 @ 114
Corrected 11.75 @ 115.45

so not as bad
what was the 60' times?

camscam02

iTrader: (21)

it doesnt seem that you are trapping to high. and ecsp. with 3.70 gears those 28's are hurting you. If you switch to 4.10's and go back to a 26 inch tire, I think you will knock off alot on your time.

what do you trap and what is your rev limiter set at?

getusumws6

iTrader: (9)

60's were 1.67 all runs, usually they are 1.51x consistant on .410 tree w/.01x r/t's

dlove

iTrader: (23)

so the 26's were 1.51? and just now it went 1.67?

getusumws6

iTrader: (9)

i was trapping 109mph all night. rev is set a 6400rpm. on the 26" tire i would trap 6,000 rpm and now w/ the 28" i trap at 5600rpm (which i had planned on). this winter i was going to do a new cam (trex or ms4) and planned to upgade to a 4.30 gear anyway, but a 4.11 for now. oh so much wasted money lol.

getusumws6

iTrader: (9)

correct, and that was dead hooking everytime.my car ran same 1.67 60's last summer with 10 bolt w/ 3.73, stock tq arm, stock shocks.

dlove

iTrader: (23)

well if the faster run was with a 1.51 and the 28 with a 1.67. that would be the difference.

you might just need more gear like you said to get it out. or look at the suspension and see if it is now maybe bogging some

Villain281H

iTrader: (5)

The 26's were probably better for getting you through the run at near the power point at the end versus the 28's and losing a bit in the rpm range.

Derek

BADSZ28

iTrader: (39)

Yeah I would go 4.11 on the 28s. Anything bigger you will run out of gear if you decide to go faster.

chrs1313

iTrader: (24)

why would you think your mph would go up going from 26s to 28s...

that would be like saying going from 3.73s to 2.73s would increase your MPH it is quiet the opposite...

that is why i didnt wanna have to go to 28s yet cause it is going to knock my mph down...without a gear change

Fred O'Bannion

iTrader: (-1)

just spray the hell out it...that should solve it!

ABA383

iTrader: (1)

Yeah as others have said if you go up in tire diameter you'll need to go numberically up in gear to compensate....I went from 3.73s and 26s to 4.10s and 28s and went from 119.75 to 121.18 with no other changers with very similar track conditions...

--Alan

BADHAWK51

iTrader: (1)

Alan it seems to me that going from 3.73s and 26s to 4.10s and 28s would be a wash but if you picked up 2mph thats awesome. I recently went to the track to test out my combo ran all motor 4000 nitrous converter (tight) 275/60/15 drag radials 28in ran a best of 4 passes 11.4 @ 119 mph 96 1/8 on a 1.731 sixty the car would not leave hard. I just put some 4.10's in and was thinking of running a 26in tire for motor runs then switch to 28's for the spray hoping the car will leave harder on motor and pick up some et and mph. Last resort will be have the stall loosend up a little. The car has all the good suspension stuff.


What you think ?

BADSZ28

iTrader: (39)

Yep. This is the way to go IMO.

BADHAWK51

iTrader: (1)

Thanks, I think so to.