Looking for input… The math shows that the ratio is the same regardless of the chain spacing. In other words, a 16/56 on a 35 spaced chain with a final ratio of 3.5 is the same 16/56 with a 219 spaced chain? However, I suspect that in action this doesn’t work out. Partially because you can’t get a 219 sprocket that small. Thoughts on this? How do find a comparable ratio in the 2 different spacing?
You’re looking for pitch conversion:
I’ve never seen this before. Thanks for sharing.
Just take ratio times driver. translates easily.
Comparing the teeth counts ratios doesn’t always give you an exact match between #219 vs #35 chains. Using the pitch diameter ratios for the gears in question is more precise. I’ll illustrate for you with examples. A #35 chain with T66 axle and T18 drive sprockets has a calculated gear ratio of 3.667. Similarly, a #219 chain with T77 axle and T21 drive sprockets has a 3.667 ratio. However, the pitch diameter ratio of the #35 sprockets is 3.650 and the #219 pitch diameter ratio is 3.654. It doesn’t sound like a lot but it translates to about 1474 axle RPM on the #35 vs 1472 RPM on the #219 chain (calculated at max HP RPM of 5380 for an LO206). Two karts running straight side by side (at that constant RPM) would have one kart ahead by almost 6 feet every minute. I had to calculate (using a spreadsheet) all the gear ratios and their corresponding pitch diameter ratios. Then I sorted everything using the gear ratios. This way I could compare what the guys running #219 chains were using versus the #35 chain gear ratios I was running. To get an equivalent gear set I would find a matching (or as close to) pitch diameter ratio in a #35 chain sprocket set.
So is a gear ratio and gear ratio apples to apples?
Scenero: (4 Stroke)
If a front driver is say bigger or smaller, but the ultimate gear ratio is the same. Does it make a difference?
In my simple mind, more teeth more torque right!
So if I played with front driver size, but ultimately came out to the right ratio I wanted. Would there be different characteristics?
This topic is relevant to that question:
But a ratio is a ratio. Negligible difference in weight and rolling resistance with bigger be smaller sprockets if the ratio is the same.
No speed there. Take whatever money and mental space you were thinking of using on this topic and put it towards chassis tuning or driving improvements.
@tjkoyen and @fatboy1dh
Thems fightin’ words some places…
You’ll have people tell you that smaller front is more acceleration and bigger front is more top, but it’s all BS. In our class, I know for a fact that any give day there’s at least 3 of the following (15 #35, an 18 #219, a 21 #219, a 19 #219, a 14 #35 and a 16 #35) all running the same lap times and same mph. The only difference between who wins is who screws up the least. Trust me, I tried an 11t and a 12t too with mini gears… No difference.
Your ratio matters, to an extent, but how you get it really doesn’t.
The Venn diagram of people who think the sprocket size matters and people who fight over tiny race cars is one circle.
I was just having a trackside conversation with someone who last year, was in the rear pack. Then this year he is running up front. He was telling me (in his mind) a smaller front driver made alot of difference when coming out of the corners. It just got me thinking as I have a cheat sheet for gear ratios incompassing all the gears I own, and as I was staring at it that when the ratio is a ratio thought crept in. With so many people going to mini gears, I’m just trying to understand what people are doing and why.
Cause seeing this guy come to my home track after not being there for over a year, and pull off the lap times he was doing was impressive.
It wasn’t the gear size that made him faster.
Also remember that we all are in these regional bubbles in karting, so when you say “everyone is going to mini gears” you’re talking about a handful of guys at your local track. Switching to smaller sprockets is not a trend that is happening everywhere, so you have to view some of these things from a wider perspective sometimes.
I’ll tell ya what happened… some guy (who was already fast) switched to a smaller gear set for whatever reason, some other guy noticed it and thought “that’s the magic bullet” and they switched. Pretty soon ol’ Dean and the other guys in the class are looking at everyone else’s sprockets and going “smaller gear must be faster since the fast guys are doing it”. Monkey see monkey do, as is the case with MANY things in karting. Everyone is always looking for the black magic, the voodoo, the silver bullet, but really there isn’t one.
Giving we’ve been running a sprocket-based powertrain since karting’s inception 70 years ago, I have to imagine this avenue was one of the first things guys explored, and if it were faster, everyone would be on smaller gear sets for the last 50 years.
TJ said it perfectly.
For example, the Senior 206 class at my home track was won with a 21 tooth 219 gear. Everyone else was on 18s or 19s. When he told them, everyone was floored. Next thing you know, everyone is on a 21 “because it’s faster”. The truth is he was too lazy to change drivers when he came from another track.
I think this really does come down to track specifics. There are a lot of tracks in the “goldilocks zone” where the gear size makes little difference. In the NW we do have a track or two where it definitely makes a difference, but it’s a very tight track with an uphill out of a tight corner.
IMO this is an acceleration vs speed thing.
Gear ratio is related to speed. (constant speed at a certain rpm)
Sprocket sizing is related to acceleration. (how quick the rpm increases)
The engine is producing a certain amount of torque coming out of a corner (acceleration speed). And the engine is able to spin the smaller sprocket quicker vs a larger sprocket…
If someone can bring me a couple data sets doing a back-to-back comparison between a 10-70 and an 11-77 and undeniably prove that one gear set was appreciably different compared to the other, I will buy you a case of the most expensive beer you want.
Free beer? To the sim laboratory we go!
Before you log your 300 laps testing this, just know that I am only accepting REAL data collected in the real-world.
I know that we are probably living in an advanced simulation and reality is merely an illusion to our small human brains, and the metaverse/virtual reality is likely just as applicable, but for the sake of this argument I want some “REAL” data.
Can I provide runs that show it doesn’t matter one iota and get beer, cause that’s the only way I’ll be getting beer…