gearing discussion

[michael brown]

i figure this might be a good topic to stir the pot and get alot of different ideas. i am into dirt drag trucks, go to alot of the DDRA races as well as the local races here in mississippi. one thing i wanna know is this. what are the advantages of running a faster front end in drag racing. i havent seen any advantages so far. i dont know if its because of the setups these trucks run or the track surface. ive never been a fan of overspeeding the front end. but i have always heard expecially from older people that its the only way to build a mud/dirt drag truck. so feel free to give your oppinion... this outta be good

[farmerjake]

If you dont have enough power to get out of control dont worry about over speeding the front end. Ive seen a lot of guys gear the front higher than the back, seems to only help when you have a high hp rig or a short wheelbase. I would also say if the track is more dirt than mud there wont be much forgiveness in the track and it will put more strain on your drivetrain. This should be a good thread.

[michael brown]

yea well the dirt drag track is usually a clay red sand mix with alittle water on it just to make it tacky. and the trucks im talking about are bigblock modified class trucks all the way down to stock class trucks.. the big block trucks are all N/a 540 or smaller engines and all around 900hp or so.. have to weigh 8lbs per CID and stuff like that. i worked on one of the top trucks in the class around here and it runs same gears front and rear.. a couple trucks run faster fronts then rears but they break often and are all over the track. and yes i say again.. im really waitin on the flaming and poo flingin to begin

[TEX]

Originally Posted by michael brown

N/a 540 or smaller engines and all around 900hp or so.. have to weigh 8lbs per CID and stuff like that. i worked on one of the top trucks in the class around here and it runs same gears front and rear..

You mean same effective ratio or actually the same ratio? 99% of the trucks I know with that much power are running smaller front tires in mud drags.

[michael brown]

tex you bring up a good point. and this is what i was trying to see said. having the same effective ratio is what i would want in my truck... the truck i used to help out on had 35x10.5 boggers up front and 35x16 boggers out back.. same ratio in both axles. now if your running a 33 up front and 35s out back having different ratios that would get it back to the same effective ratio would work right. but what im trying to get at is the people, and this is why having mixed ratios in my eyes is wrong, that try to tell me to put a faster speeded front end in a race truck is so the truck "pulls" itself down the track... well this to me makes zero sense. so to correct what im trying to get at... would having the same effective ratio or a faster speeded front end the right way to go. i say if you cant push it across the shop floor with 1 hand then your in trouble...

oh and tex i run on dirt drags, not mud drags so i dont really know alot about the mud drag stuff.

[Brent Foster]

i say if you cant push it across the shop floor with 1 hand then your in trouble...

In my opinion your correct. anytime you get the ratio outside of 2% faster or slower, you rob power. if your allowed to run 4-links and everything is set up right, then the front isn't doing much anymore anyhow. I've always thought running faster in the front is just to keep up with the swelling in the rear tires at high speed.

Why are you not running a bigger tire in the back? are you limited to tire size?

[michael brown]

well we arent limited on tire size. we must run DOT uncut tires though. class only allows us to run ladderbars and coilovers on the rear. but we must retain the factory leaf spring also. so most guys run just the main leaf with a floater and then the ladderbars. the front suspension on the trucks cant really be messed with which really pisses me off. the fast trucks in this class have all switched over to 35/16 boggers in the back with either q78 buckshots up front or the 35x10.5 boggers up front.

[TEX]

Originally Posted by michael brown

oh and tex i run on dirt drags, not mud drags so i dont really know alot about the mud drag stuff.

What you described isn't that much off from what we call mud drags. Maybe a bit more moisture than you described, but no standing water or slop. Typically tilled with a big farm tractor with a disc & then hosed down for better traction. Incidentally, I'd probably run Claws if it was REAL dry.

[michael brown]

yea tex thats basically what it is.. just wet enough to get tacky. what i was meaning about the differences in the dirt drags and mud drags was the basic rules and stuff. but id figure other than the rules it would be close. that and the mud guys need more bite. i have a set of cut 35x13 i think they are 13 inch wide baja claws that i need to finish cutting and then we gonna try them on a 2wd truck. no one around here has tried the claws. ive often wondered what they would do. i donno if they would do good if it was dry and they was uncut though. now if i could cut them, im pretty sure they will bite pretty hard.

but back to the topic.. in the mud do yall guys run the same effective ratios? or do yall overspeed the front?

[TEX]

Most overdrive the front, but not by a ton. It's kind of like Brent said, the 44" rears will grow at least 2" under acceleration, so they really push you around if you don't speed up the front some (for those with the power to make that happen anyway).

[michael brown]

wow.. yall runnin 44s? we only run 35s...... the guys up north in super mod class run 37s and stuff. i know the 35s grow but not nearly like a 44 would. i see what your saying on the over speeding the front so when your flat out on the power the tires are closer to spinnin the same speed. so i guess the old sayin them old rednecks keep tellin me is just as stupid as lift blocks on the front end LOL.

[TEX]

The "typical" Pro Stock setup these days is 44's in back with 28's in front & about 100" of wheelbase

[michael brown]

tex now thats a sight i wanna see.. sadly they dont race around here. haha our fastest trucks are only runnin 4.2s in 300ft and up north the super mods are down in the 3.70s but they dont race down here... i would love to see yall come down here and sling a lil dirt haha

[mustange70]

Couple the rail guys in my area in addition to compensating for the tire growth, say a little bit more helps them steer better in the deeper mud bog type tracks, but they don't overdrive by much (2% like said above, maybe a tad more but not alot.)

[Hillbilly Rockstar]

I have had issues with my truck fish tailin pretty good through a pit, runnin 39.5s and 4.88s. I'm hoping to add 38.5s on the front with 4.56 gears, the front will be turning just slightly faster then the rear which might help out. I can't see it causing much of a problem.

[Hillbilly Deluxe]

With a direct drive/chain drive or what ever would'nt the front tires be turing at the same speed as the rear, in theory growing the same in size as the rear under acceleration?

[Krawler86]

Originally Posted by Hillbilly Deluxe

With a direct drive/chain drive or what ever would'nt the front tires be turing at the same speed as the rear, in theory growing the same in size as the rear under acceleration?

Im assuming the taller tires in the rear grow more than the fronts, especially if running the 44/28s. Though if you had 4 the same, that sounds right.

[TEX]

Originally Posted by Hillbilly Deluxe

With a direct drive/chain drive or what ever would'nt the front tires be turing at the same speed as the rear, in theory growing the same in size as the rear under acceleration?

Assuming matched gearing and matched tires.

[Hillbilly Deluxe]

Yes, all tires the same both gears the same.

[reddwarf]

Originally Posted by TEX

The "typical" Pro Stock setup these days ... 28's in front ...

I saw that the other day and I'm wondering why? Seems like a little bit more tire would be better. Is it the rotating mass I guess?

[TEX]

Yeah, I assume it's to get as much weight (especially rolling weight) off the frontend as possible. These trucks are running really short wheelbases these days (105" where 130" was the norm just a few years ago), and basically functioning more like a 2wd.

[michael brown]

hey tex if they tryin to make em perform like a 2wd then why not just build 2wds? ha

i donno the class rules yall got but we got a "pro et" class in the dirt drags anywhere from a 5.50 to a 4.30 dial in. trucks cars rails and buggys allowed just no forced induction and stuff like that.

this is a truck i built for a guy to race in that class... its gettin a better engine package over the winter

[TEX]

Rules require 4wd.

[nvrsatisfied]

this is something new that my buddies and i have gotten into over the last year. my friend has been leaning toward more and more of the 200ft dirt drags. he is running 38" boggers in all four corners with 456 gears both axles. we are looking into building a whole new chasis and applying some of newer knowledge (hopeing we learned something from this year) threw out the winter. the motor is a BBC and does about 550hp. he has ran some low 5's to high 4's in the dirt drags. now were are not in circuit just hitting up some of the locals, and wishing we were running like the big boys.

my newbie question; should we keep the gears front/rear, keep the backs at 38'' and do the fronts in a 35" for the 200ft dirt drag??? <-- is this with in the 2% range? then be able to change the front tires back to the 38" and be able to do the 200ft mud pit?? or will the 38" rear/35" front work in mud pit also.

we had watch a truck by the name of "SCOOBY DOO" a few weeks back in Kansas (KBL) and that dude was


thanks for the help and great thread....

[michael brown]

if your running on a "dirt" track i wouldnt run that big of a tire. around here the big block modified guys are runnin 900+hp and 35s... but its a tacky dirt deffinatly not mud track