Advantage of big lower gear

[kinger]

What is the advantage of a larger lower gear? The mtx's come with a 40t lower the trail sleds with a 38t lower, people change out for a 42t lower why? Thanks!

 

[quebecmoutainrider]

if its like a dirt bike..then the more teeth,the more tork,power.less speed.this is why road bikes have less teeth than dirt bikes.this is the way I was taught...hope it was right..lol..or I wasted alot of time tunning my dirt bike. .lol..good thing I was young.Kinger..go spank some M-Zs..

 

[kinger]

Yeah I still dont get it I have 25/42 gearing now and its limiting my top speed to 120mph would like more then that although it gets there QUICK.

 

[kviper]

Generally the bigger gear's will be more efficient due to less wrap for the chain and will run cooler but you still need to come up with the gear ratio that you need or want. Example 23/38 is almost the same ratio as 24/40 but the 24/40 should be more efficient. Splitting hair's but that is the theory. kviper

 

[kinger]

Got it, big gear less spinning for same speed, less friction, more power transmitted.

That equates to 1/10 of 1% of hp increase LOL

I wonder what I'll miss if I go from 25/42 to 25/38? It would add about 25 mph tops speed if the sled will pull it.

 

[kviper]

I don't know that any one has ever put number's to that theory as far as track hp but i would think your chain and gear's would last longer and the chain case would run cooler. I was told by a top oval racer from year's back to use the biggest gear's that you can fit in the case that will give you the mph you are looking for and never put in more gearing than you can pull or use on a given track. Made sense to me. I also have heard of guy's running a 22 tooth top gear and it was showing a lot of wear after like two season's with not a lot of mile's. kviper

 

[mulot30th]

bigger lower gear = LESS tension in chain than going with smaller upper gear.

This is for more reliability.

 

[harryamaha]

I would certainly like to see A lot more imput on this topic. From what I know and understand of the 4 stroke the powerband should be able to handle a wider variety of combinations as compared to a 2-stroke? I had a 81 pantera 5000 was down right scarey on the flat and hard it was that fast but couldn't climb a hill or hardly move in snow because of the way it was geared. I have a friend shocked me last winter with the speed of his venture multi-purpose with just a single gear change and there was no noticable power loss from his opinion.

 

[kinger]

So waht drives a guy to spend $200 on a new lower gear say going from a 38 to a 42t?

The stuff we mentioned is fractions of a gain, seem like its not a value minded mod unless the gearing is really screwed up to start with.

 

[harryamaha]

I keep checking back on this topic but never see any imput? I'm no expert on the topic but it seems to me this is the most neglected one! Should be as simple as a peddle bike with gearing. There is a huge difference with gearing depending on what your looking for. Power versus speed? A gear change can be very substantial for speed or power depending on what you want. If you supercharge and add 50+ HP with no gear change, unless you are strictly after power and not speed would be unreasonable? Is it not reasonable to say more power equals less speed and vice versa?

 

[quebecmoutainrider]

as far as I am concerned..harryamaha...sounds right to me.. .changed my gears because of the S.C. and now shes faster..but still has tons of tork...

 

[Snowman269]

I try to run my chains as straight as possible, less wear, less heat, and more HP to the ground. On many of my snowmobiles, I run 20/40 with a 68 link chain. Almost don't need the chain adjuster it fits so close.

 

[Dreams_of_Apex]

Changing the Sprockets, top or bottom will change your gearing, to get the most out of that, you will need to likely make Clutch changes as well. Think of this in terms of an old 18 Speed Mountain bike, you change the Top (front) if you go smaller, it gets harder to pedal, but your theoretical top speed increases. Change the Back (bottom) to a larger sprocket, and you now also get harder to turn, but faster Top speed.

You don't want to go too drastic, as it will cause too much chain tension/wear, and prematurely fail, but by changing the gearing the you change how easily the motor can turn the track. By Dropping a tooth on the top, or increasing on the bottom, you are decreasing the gearing, making it easier for the engine to spin the track, good for deeper snow, or pulling a load, or a 2 up sled, and should increase corner to corner acceleration. If your going to make your gearing taller (increase top, or decrease bottom) you will make it harder for the engine to spin the track, less acceleration, but should mean more Top speed, IF the engine and clutching has the HP to pull that. I would think if you increase the HP on the machine with Mods you would want to go with taller gearing.

Gearing will only get you so much, likely need to tune Clutch as well if you go too drastic.

My .02 cents

 

[kinger]

After a ton of gear changes I ended up back dead stock 24/38 with my supercharged apex. Good pull everywhere and decent top speed.

 

[SXlover]

I run 20/42 in my Apex Mountain. I also have a Bender 54/42 (I think) helix with Supertip weights in the clutch, turning a 174x2.5x16 camo extreme. In my case the sled was geared down for the right combination of speed and torque for hillclimbing.