Auto X Gearing for steep terrain - Options and opinions, please.

[elbearo]

TL;DR
Anyone running an Auto X geared for slopes and inclines? What are you running, in what terrain, and how do you like it?

I am finishing one auto X and I'll be starting another in the next couple weeks. I currently have an '83 200S engine in the one that I am finishing up now, and dropping an '85 200M engine into another one that has a tired stock engine. The tired 200X engine will be thrown into another machine, just to get it running until we have an engine rebuild day/weekend.

It seems most of the gearing threads I have come across related to auto Xs are people looking for more top end. I'm going the other direction with mine and wanted to hear from anyone with any experience riding an auto X in different terrain and specifically in steep or mountainous terrain. I'm on acreage in the mountains and other than speed runs up/down the driveway, most riding done on the property is accomplished in 1st gear, sometimes 2nd and almost never in 3rd. This is consistent from a 350X down to an ATC 70. I plan to regear most of these trikes eventually, but I am wanting to finish the auto X projects soon and hope to have my gearing options delivered before I need them.

I plan to pick up some taller gears to swap out if/when we take them on camp adventures and want to cover more ground, but I would guess that these will be run 95% of the time on the property, billy-goating around on side-hills in the mountains. I've got a line on an '83 BR engine with Hi/Lo that is really tempting given our terrain, but probably not happening right away. I'm planning to keep 20"-22" tires on the machines.

Useful input appreciated.

[ps2fixer]

I'd say to try the gearing you have on hand and see how it feels to you. If it is too high, then getting a 1-2 tooth smaller front sprocket would drop the ratio quite a lot and would be semi easy to swap out. The rear could go larger as well but keeping things simple to swap between the two ratios might be a good target. I'd personally stick with the larger tires just for the ground clearance.

[elbearo]

I currently have 11/40 in it now and need to put the nut on the swinger and take the chain slack out before I can run it. I may get to that tonight.
:rolleyes: I should also wait for the brake parts to get here so I have brakes, but ..ain't nobody got time for that!

The stock 12/40 in my 200Xs could already be lower for the hills I'm riding, so I'm not expecting the stuff I have on hand to cut it. I'm never that lucky. I am planning to stick with the taller tires for ground clearance, but it could come down to running what I have on hand. We've got a lot of rocks, logs and all kinds of things that I'd rather not drag the sprocket & chain through.

I'm guessing somewhere in the range of 11 or 12 on the front and 44 - 46 rear will work well. If I can, I want to order all the sprockets for both trikes (possibly 3 trikes = 3 sets) at the same time and would feel better knowing that someone out there was running the same combo in similar terrain and it worked well, before I order anything.

Maybe I haven't been paying enough attention, but I'm not seeing a lot of people riding these on the side of a mountain regularly, so I'm probably just going to have to do some trial and error to find a combo I like. I'm sure the sprockets would get used up eventually, but I have a lot of projects I'm trying to get off the ground and the cost of a set of sprockets could be the difference in getting another trike up and running sooner, rather than later.

Thanks for the input.

[ps2fixer]

Here is another way to look at it to get a ratio to target.

Factory is 12/40 or 3.33 turns of the front for 1 turn of the rear.
11/40 would be 3.63 turns, so around 10% change. If you also put a 44 on the back, that would be another 10% change at 4 turns.

With a sports quad with 28 inch mud tires we were running 11 up front and 52 in the rear, factory was 13 and 40 and 22 inch tires. It didn't really loose a lot on top speed, mainly limited by the revs instead of power output.

[elbearo]

Good explanation, I follow the ratio logic. I also still have some time to figure things out. If I shot from the hip, I had planned to just order a 44 or 46 rear and try it out with the 12 up front. I hoped someone else had done some trial and error riding an auto X in similar conditions, and would chime in. That would give me a better idea of a starting point, that might just work fine for me the first time. We may have a trip coming up soon and I wanted to get bugs worked out where I could if we decided to take them.

The result I am hoping for is something I can throw around on our trails with some speed, that has enough grunt to get up the hills without struggling. I am also hoping the autos will be easy enough to handle for some of our friends that are more novice riders. Our trails are tight with tight turns and switchbacks. It's fun putting around and all, but it's a riot when you can really hit it. The auto X with lower gearing seems a good fit.

[ps2fixer]

Another thing to mention, since it is going to become an auto from a manual so to say, if we look at Toyota trucks, the transmission in the manual is much lower geared than their automatics. My truck's 1st gear is something like 3.96:1 and 2nd gear is around 2.6:1. The same truck/year/engine combo with an automatic the first gear is really close to my manual's 2nd gear. I'd suspect the transmission in the 200x vs 200s are probably really close to the same. Of course this isn't a perfect comparison.

The other thing to point out, if you went with the 11 in the front and 44 in the rear and it still wasn't enough, going from 22 to 20in tires in the back would be another 10% lower geared. 30% is pretty huge.

Just for a visual. Let's assume some of the steep hills you go up makes the engine run at 1500 rpm

0% - 1500
10% - 1650
20% - 1800
30% - 1950

I'd suspect the 10% might do you really well and the 20% probably better, but the 30% probably would be overkill. Same effect on your top speed except the engine can rev out more if it's old top speed was limited to power rather than rev limit. Just to throw some numbers out, I'll guess the auto x's can go around 50mph.

0% - 50
10% - 45
20% - 40
30% - 35