Is there any advantage to gearing like this?

[Knips178]

I have a 14t front and stock rear (38t??) and it pulls good at the bottom, but with my engine buildup I start in second gear and never use 1st. Wouldn't it be smarter to use a 15t front so i start in 1st gear to give me more top end? I'm using it for MX and general backyard messing around. What i'm getting at is, why gear it so low if your not using one of your gears? if i gear it a little higher with stock teeth and have more bottom end in my motor, than i can take off in 1st gear and add more top end.

I know some people run 18" rears and 14t fs and 40t rs(I'll call setup 1), and they like for mx where you need the bottom end power, but they also don't use 1st gear. Unless you have perfect traction where your tire doesn't slip at all, wouldn't a 20" rear tire 15t fs and 38t rs (setup 2) accelerate off the line just as fast as setup 1? I would think that 99% of the time setup 1 would just spin the tires like a 2 stroke while setup 2 would grip and go off the start, assuming they both had the exact same torque and hp.

i'm sure this is way more than anyone cares to read, but it's been knawing on my mind lately.
thnx

[R3Concepts]

I run a 14/38 right now with 18x9.5 tamers, and im looking for a 40T for the arenacross tracks I do. IMO you need to be geared lower for mx, one reason being you start off in a higher gear 2nd or 3rd, next, the closer the ratio the more your bike will stay in the desired RPM range when shifting, yes you will be shifting more, but whats the point of having 5th gear if you dont use it on the track? Also dont ever start out in 1st, big no no, by starting in 2nd you just skipped the possibilty of hitting neutral. And we al know if you hit neutral on the holeshot you just lost the race. If you went to a 15/38 and 20" tires its not going to start as near as good as a 14/38 with 18s, becuase for one you geared up in the front one tooth which makes more of a difference the most think, and you added more rotating mass with the 20s in the back. You will have good top speed but I rarely race a track that is a top speed track. Stay with the 14/38 or 14/40 that way you holeshot the race, then pull 3rd though the corners, faster entry, faster exit= race winner.

[quadmx7]

yep i agree with R3, im running a 14/38 set up right now with 18 holeshot mxr's so in a race i start off in 2nd gear. what the point in using first, it goes by too quick and u get a quicker start in 2nd. blake, this guy i practice with has a 400ex with a few engine mods and he runs a 15/38 set up with 18's on the back and has only got the holeshot from me once. hopefully next week my 426 motor will be here and im going to be running a 14/39 set up for mx and arenacross. plus on most of the tracks i race are really tight coming out of corners and u dont get much time to build up speed and a 15t sproket doesnt help that. i raced a quy once with a sparks 425 kit and he had it geared so low that he did a 3rd gear start and smoked everybody, my cosuin's 440 got him off the gate but half way down the start the 425 passed him.

[KY Woods Rider]

I agree with R3. You need the quad geared for acceleration, not top speed. You're worried about not using 1st gear, but why gear it up to where you never use the higher gears. Unless you're running a very wide open track, you're never going to wind it out in 5th if you're running 15/38 with 18s, and on many small tracks you'll never even get it into 5th. The straight stretches on an MX track aren't that long, so if you gear it up, you've just lost some acceleration capability and you still have gears that aren't being used.

As for the 15/38 and 20s idea, it's not so great. When I ride MX, I ride my woods quad, which has 20s and 15/38 gearing, and it is definitely not the hot set-up for MX. Unless it's muddy where I'll break loose spinning, I have to start in first. Actually, I can pull a start in second if I rev the living crap out of it and release the clutch smoothly, but overall it's much slower than if I just use first and make a shift as the rear wheels go over the gate. By using first though, I can get a good jump as soon as the gate falls, but about half-way down the start straight the higher gearing begins to show itself. As soon as I start pulling through the gears, I lose any advantage I had, because the higher gearing makes it harder for the motor to gain RPM after a shift. Out on the track, there are very few straights that can make use of 4th gear, most straights are taken in 3rd and tight sections are handled by 2nd. So overall, I'm giving up acceleration for some top speed. The problem is that there's nowhere to use all that top speed within the confines of an MX track, so all I've accomplished is a loss of acceleration.

[wilkin250r]

It was said once, but you may have glanced over it.

Rotational inertia is a big deal, more so than linear inertia. Those 20 inch tires have a whole lot more rotational inertia than the 18's, and you lose acceleration because of it.

And more important than any of this is: Find the setup that works best for you. If you're losing time because of shifting, then maybe taller gearing would work better for you. Or vice-versa. Try it and see.

[04'400ex'er]

Buy a 15 tooth front and a 40 tooth rear. try them both at different times to see what you like. That's the only way you will ever find out what your preferance is.

[R3Concepts]

Stock is a 15 so just buy a 40T rear.

[Florida400EX]

How about 18" tires with stock gearing for MX? Or should I also switch to a 14 front?
Thanks!

[R3Concepts]

Stick with the 15/38 stock gearing for long, fast, sweeping cornered mx tracks, then switch to a 14/38 or 14/40 for tight arenacross style tracks. Both will work well with 18s.

[Knips178]

well i have a new set of razr 20" rears that i'm not going to chuck just yet, but i have been running a 14t front gear. for mx on a 40hp 440ex what gearing should i run with my razr's? 14t and 40t? or is it that noticeable that i should be looking to sell my razr and get 18" rears?

[R3Concepts]

I wouldnt run 20s on the mx track, too much mass. Another thing is the bigger the tire the bigger the sidewall, easier to pop off the beads. I would run some sort of 18 if I were you, like a klaw or tamer. They will make that 440 seem huge.

[K_Fulk]

Do you guys with the 14 tooth front and 18's spin of the line? And do you go fullbore out of the gate or are you feathering the clutch? Just wondering.

I run 16/38 with mxr's. I start in 2nd dump the clutch with it pinned and take off. I have some very slight wheelspin off the start and then it just gets on down the track.
When i ran 18 inch tamers and stock gearing and started like that I would just sit there and spin.
Also with the 16 tooth front I stay between 2nd and 4th gear and dont have to shift as much.

I'm just thinking with the lower gearing it wouldn't hook up as easy with the same amount of throttle. Due to the lower gearing turning the tires faster.

[440ex dragger]

A good tire to run if you dont want a sidewall would be an 18" Fast Trekkers, have you seen the side wall on those it is like rim then dirt almost lol. But if you are worried about hitting neutral then just practice more and you will get used to it. I know that this is completely off subject but I ran stock gearing and tires and I would spin like a mofo off the line at the drag track, I guess it is kinda the same though.

[Knips178]

K_fulk basically just summed up what i was wondering. With everything geared so low, i would think that without perfect traction, you would actually lose time due to wheel spin. and really how often you actually perfectly hookup, almost never.

[robman]

I have 20's and run 15-36,perfect gearing on my 426ex for all conditions.I'll prob hafto change the gearing when i get mx tires for racing.

[Chanman420q]

ive been thinking of playing with my gearing too, im running stock gearing on 20''s right now on my track and im having a hell of a hard time doing the ryhthem section because i have to drop from 3rd down to second when i corner, then i cant get the revs up fast enuff to clear the first jump and im just a total mess. i got 18s, and im gunna try that, but i need to wait for my 20'' front tires to get in. ive been thinking abouit getting a 14T or a 39 rear