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Gearing for Grass Drags

Joined May 2011
700 Posts | 3+
Wisconsin, U.S.
Every summer in my area the surrounding towns all have quad/dirtbike grass drags. basically off road drag racing for a length of somewhere between 200-500 feet on a fairly ideal flat dirt track, any thoughts on if a lower or higher gearing would be preffered? the higher stock gearing i think maybe would be best? stock 15-42 vs woods gearing 15-48 or maybe right in the middle at 16-48? i 'think' it 'feels' faster with the higher gearing and with 600 torque it still revs through the gears quickly and maybe less likely for all out tire spin and also less time spent shifting?

just wondering if anybody has any thoughts on this before i get some beers, buddies, and stop watches for a test day which maybe still will be in order...... :D
 
how many shifts can you get in over 200m ? are you setting off in 1st? when i did a flat track day i was told to set off in 2nd and jsut drop the clutch, digs an nice rut and off you go. So would it be better to find a ratio that works for that based on a short distance.

Pete
 
I have never expermented with 2nd gear starts i guess, i can probably do that with the 15-42 factory gearing, the 15-48 gearing i use for slower stuff would for sure, it gets up quick and is real snappy on a quick burst but it goes through the gears so quick, it seems the factory gearing allows it to do more work in each gear (obviously because its higher) and has enough power it seems to pull just as hard as the lower gearing only for a longer period of time and with less wheel spin. i would think in a 200m drag starting in second with the lower gearing i could be to 5th for sure maybe even in sixth, i guess i have never tried it from stopped, on a measured out course, thats flat with ideal surfaces with either gearing to really know, guess ill never know for sure which ones actually faster till get someone with a stopwatch and measure it out.
 
Bergini said:
Every summer in my area the surrounding towns all have quad/dirtbike grass drags. basically off road drag racing for a length of somewhere between 200-500 feet on a fairly ideal flat dirt track, any thoughts on if a lower or higher gearing would be preffered? the higher stock gearing i think maybe would be best? stock 15-42 vs woods gearing 15-48 or maybe right in the middle at 16-48? i 'think' it 'feels' faster with the higher gearing and with 600 torque it still revs through the gears quickly and maybe less likely for all out tire spin and also less time spent shifting?

just wondering if anybody has any thoughts on this before i get some beers, buddies, and stop watches for a test day which maybe still will be in order...... :D

I'm tempted to say: 'rubbish' but that is too strong a word.

the correct gearing is a gear that picks up grip at the lowest revs without spinning the tyre.

gearing is done as a way introducing the correct BHP to the ground.

so if I wanted to deliver all 35bhp to the ground I would drop the clutch at 10,000rpm.

if I delivered 12bhp and had wheel spin at say 5,000 revs I might change the rear sprocket, take a tooth off so that it was 4,750 revs and less power (say 10bhp) but for the same speed at the tyre.

what you end up with is, like speedway, a bike that grips and slips the correct amount for forward drive. this will depend on conditions at the BEGINNING of the event and will also change as the day goes on as more grip becomes available.

regards

Taffy
 
Taffy said:
I'm tempted to say: 'rubbish' but that is too strong a word.

HA! its all good fun taff, bikes are allowed but its mostly a bunch of half intoxicated rednecks on 'souped' up quads. most of them with no skill other then driving into a bog or in a straight line, winning will get you bragging rights and also determine the size of you pecker (measured in feet of course) and maybe even a cash prize. i really dont care to win the whole thing i would just like to keep at least of couple of them in particular quiet for a year or so...

i dont normally particpate in this kind of thing but i thought maybe it would be fun and theres not a lot to choose from here without a long drive, i am not going to spend any money to win except maybe an already needed tire, but i may as well figure out what gearing would be best for it so at least i dont get embarassed......ill get a practice day together and get it sorted... i set my sag last night and tweaked the clickers back to stock position, i only got a quick ride out today but it even seemed to help combat wheelspin, although it was so far off its no wonder, guess i shoulda set that a while ago im just glad all settings fell into spec with my currect spring weight, and all this time i though i needed to lose 20lbs....
 
now you know why the same old gearing charts piss me off.

sorry if it was over your head.

Taffy
 

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