Highest gear ratio you've run?

Highest ratio run/ran.


  • Total voters
    43
#1
I just want to hear some experiences with high gear ratio and the other factors that go into play along with them such as:
Weight of mini-bike (or go kart) and operator combined.
Gear ratio.
Size of tires.
estimated top speed
estimated time to get to top speed.

`My personal experienced highest gear ratio so far was on a gokart ,total weight with me on it estimated 220(its very light), and i'm not 100% of the top speed but it was a 4:1 ratio and i'm fairly certain it goes 45mph+ in about 4.5-ish until it slows to a crawl due to the stock cam and 1WD.
`I'm waiting for a live axle to lay down more traction for the .290 cam @ 104lsa and will re-try it cause all it does is spin the tire and slow down acceleration.
``oh..i will be experimenting with 3:1 ratio very soon with a torque converter and custom machined sprocket. I've done 4:1 with a clutch(though it does get hot quick) so i'm more than certain it can be done with a torque converter. 4:1 ratio i haven't had any problems with except at high rpm(meaning 5000+ rpm estimated ) or excessive full throttle acceleration the belt starts to slip. My goal speed will only be around 5k rpm max due to that reason.

So how about you guys using high performance clutches? Do they help get you more RPM and torque at all?
i want to hear if anyone else has tried really high gear ratios and their experience.

i think this topic is something we can all learn from.
\/48 tooth on my drive wheel and 12 tooth Torque converter sprocket\/
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#2
You're not comparing apples to apples. A 4:1 with a TAV doesn't suffer the ill effects that a clutch will because it's reduced by 2.7:1 initially. Plenty of guys run a taller gear in the drag racing world. A clutch will allow more RPM but at 3:1 you'll be very hard on it at start out and part throttle. Even a good disc clutch.
Again it seems you want this to takeoff like a rocket and do 60 mph. For the best all around ride-ability, I suggest sticking with the TAV and yellow spring to get some rpm. Too tall of a gear and you'll be blowing through the belt with the added power. It's only a 30 series.


Sent from my Texas Instruments Speak and Spell...[emoji2]
 
#3
You're not comparing apples to apples. A 4:1 with a TAV doesn't suffer the ill effects that a clutch will because it's reduced by 2.7:1 initially. Plenty of guys run a taller gear in the drag racing world. A clutch will allow more RPM but at 3:1 you'll be very hard on it at start out and part throttle. Even a good disc clutch.
Again it seems you want this to takeoff like a rocket and do 60 mph. For the best all around ride-ability, I suggest sticking with the TAV and yellow spring to get some rpm. Too tall of a gear and you'll be blowing through the belt with the added power. It's only a 30 series.
You are good. i can tell you've been doing this for a loooong while.
Thanks for the shared wisdom! i sure benefit from it.
-- Stay Awesome --
 
#4
So I'm currently on a 12 tooth clutch and 72 rear sprocket.. it tops out on the governor at 27+/- mph..
However it has the stones to pull a wheelie at any speed up to about 24 mph, and from a dead stop you cannot grab a full twist without coming off the back of it.. I'm looking to tame the front wheel a bit..

Is dropping to a 60 in the rear advisable? I'm not worried about gaining the top end, I simply don't want to fry my centrifugal clutch.. and a $15 sprocket is a cheap alternative till I can swing a $120+ TAV..
 
#5
So I'm currently on a 12 tooth clutch and 72 rear sprocket.. it tops out on the governor at 27+/- mph..
However it has the stones to pull a wheelie at any speed up to about 24 mph, and from a dead stop you cannot grab a full twist without coming off the back of it.. I'm looking to tame the front wheel a bit..

Is dropping to a 60 in the rear advisable? I'm not worried about gaining the top end, I simply don't want to fry my centrifugal clutch.. and a $15 sprocket is a cheap alternative till I can swing a $120+ TAV..
cool, haha.
i haven't experimented with torquey gear ratios yet. i just figured since i'm always spinning my wheel on my really light weight gokart with a torque converter i can gear really high (3:1 ). and that's also why i lengthened my kart to avoid wheelies.
i don't know how long a clutch will last on 5:1 ratio but it will work.
 
#6
So I'm currently on a 12 tooth clutch and 72 rear sprocket.. it tops out on the governor at 27+/- mph..
However it has the stones to pull a wheelie at any speed up to about 24 mph, and from a dead stop you cannot grab a full twist without coming off the back of it.. I'm looking to tame the front wheel a bit..

Is dropping to a 60 in the rear advisable? I'm not worried about gaining the top end, I simply don't want to fry my centrifugal clutch.. and a $15 sprocket is a cheap alternative till I can swing a $120+ TAV..
You didn't mention tire size but if you aren't doing a lot of trail riding I think a 60 will be ok.


Sent from my Texas Instruments Speak and Spell...[emoji2]
 
#7
It's an old Cestad/Monkey Wards.. Predator 212 with torque master 12 tooth clutch with the 72 tooth in the rear all riding on the boss 4.10X3.50-6 tires lol.. I'm 230lbs and I have to get up on the bars to keep the front wheel down, and then it's borderline on having enough weight on the rear to keep it from spinning. Just when I think i've found the sweet spot, it will either pick up the front anyways, or spin the rear... It's a blast for me, but way to much for even my oldest to ride currently!
 
#9
With that size tire I'd drop to a 60T.


Sent from my Texas Instruments Speak and Spell...[emoji2]
I do believe I am going to, I just went for a ride around the block, and turning around to the left, I caught the sprocket on a small rock.. -it was enough to kick the back-end a solid foot to the right and jar my right hip trying to keep from high siding it.. The sprocket is almost the same size as the tire.. That alone is a massive selling point for me!
 
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#10
I was going to say you can go up to a 5.30x4.50x6 tire, but I don't think it will help as much as the sprocket change. I had the same trouble with my Hemi on a bike geared 12/72. I did some small bolt on work to it and at 210lbs, it was a handful.


Sent from my Texas Instruments Speak and Spell...[emoji2]
 
#11
Wow. Seems like i'm the only one that has tried a really high ratio so far. Mostly people with 6:1 ratio so far. Maybe i should record a video showing how a 4:1 ratio 1WD kart with torque converter drives?
 
#12
There are 2 ratios, the chain has its own static ratio, and the TC has its own dynamic ratio that changes when the sheaves open/close.
Because the TC changes the effective ratio, you can run a lower gear ratio than a reg centri clutch, because the TC effectively raises and lowers the ratio depending on load.

My jr dragster clutch driver is the same principle but uses weights/rollers/ramps instead of springs and clutch discs or the weight pack of a reg TC. Driven is essentially the same design just beefier.
 
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#13
You can easily hit 60 mph with a 5/1ratio and not have it be a pig out of the hole with a good clutch and a built motor ... from what I have seen a tav will always peak and go flat well before that ... unless you have a set up like massacres that is meant for speed
 
#15
Correct. A simple 30 series just can't handle the rpm. It feels like weak valve springs when it lays over!


Sent from my Texas Instruments Speak and Spell...[emoji2]
 
#17
Correct. A simple 30 series just can't handle the rpm.
i hope my logic is reasonable, correct me if i'm wrong..\/ my logic is based on experience.
Due to the TAV being limited on RPM, i bought a custom 36 tooth driven sprocket to go with my 12 tooth driver. i will say 5k rpm will be the max speed and everything passed that would be the redline for the TAV. For example at higher RPMs the belt will start to slip and the TAV its self will start to get hot and burn the belt.

i expect the .290 cam @104LSA w/ .246 duration to be able to get me up to my desired speed when needed.
Also bought the yellow driven spring and orange driver springs(1500rpm engagement).

When i receive the items i shall post back the results.
added: i hope the predator can idle below 1500rpm.
 
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#18
I have 5 mini's with TC's with ratios between 6-1 and 8-1. I don't understand why you would try to run a 4 to 1 ratio with a 246 @ .050 cam and a tav 30 that has a .9 to 1 overdrive. That cam moves the torque peak quite a bit higher than stock and when the converter goes into overdrive it's too much load for that motor. I have not had the issue of the motor laying over on my bikes and the one with the TAV30 I have no idea of its speed as it only has a tach but I have had it to 6K and it still pulling but I get scared when the get going too fast. That particular bike has a black mamba Jr in it. All Maybe because of my other tc's are salsbury 330's and comet 340's. Maybe your kart as a lot smaller diameter tires than a mini which may allow bit higher ratio to work. What RPM are you at when it tops out?
 

noseoil

Active Member
#20
I'm running an old Baja Warrior with the 19" tires, 50 tooth rear sprocket & 10 tooth on the Tav's driven output side. It would be 5:1 but with the TAV (cheap clone type) it's actually at 4.5:1 when at full speed & in overdrive mode. This ends up being 52 mph, since the engine can't push any more air out of the way with the simple mods I've done & that's all the hp it makes.

I've ordered an 11 tooth for the driven just to see what it does, but I don't expect to see much difference in top speed. The engine is still only making enough hp to move through the wind load, it will be at a different rpm range, but that's really all. The actual final drive will be at 4.09:1 with the 11 tooth sprocket.
 
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