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General Category >> Rubber Side Down! >> You are gearing this final drive wrong
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Message started by Surviving Philly on 11/10/24 at 12:52:00

Title: You are gearing this final drive wrong
Post by Surviving Philly on 11/10/24 at 12:52:00

Alright. Let's get controversial here.

I think our machine performance exactly perfect with shorter gearing. I just did a chain conversion, with a 15t front and 48 rear, giving a ratio of roughly 3.2 over the stock 2.9-3.0.

I can't tell you how good it feels..... My God. I couldn't imagine going for taller gearing. It's not a highway rider in my book, it wants to rip. And rip it does

. https://photos.app.goo.gl/DHneBZTcKT7Sw1eb6

Title: Re: You are gearing this final drive wrong
Post by JOG on 11/10/24 at 13:58:56

That looks great.. I hope you cover the front sprocket.

Title: Re: You are gearing this final drive wrong
Post by ThumperPaul on 11/12/24 at 05:24:14

Brap, Brap, Brap, Brap, Brapppppppppp! I bet it is pretty fun running it up and down the gearbox! Will the engine braking take you from 60-0 in 5th in 120 feet without touching the brake? (Joking exaggeration)

Can you still hit 75mph? Hey, you might even be able to hit the redline in 5th with that setup! I wonder how much gas mileage is impacted.

I think you nailed it with “controversial”. The taller gear camp wanting lower RPMs at highway speed in top gear.

Nice job on the conversion! If you decide you want to tinker with it, you have fairly simple swap options.

Unrelated - how’s the clutch holding up? What does it think about the chain/sprocket conversion?

Title: Re: You are gearing this final drive wrong
Post by Surviving Philly on 11/12/24 at 11:33:49

I can still hit 75 definitely -- I think 80-85 comfortably but I ditched the speedo so I'm basing this off of feel. The most surprising thing is how much torque I have in the higher gears. Stock gearing felt like there wasn't much to give from 4-5th, whereas I am now comfortably switching gears with some OOMF left if I'm caught off guard in a higher gear.

About the clutch it seems totally fine. I've done a couple long hauls since replacing the Barnett kit and so far, so good. I still suspect the Barnett pack was eating that plate, as silly as it sounds. This caltrec kit is presumably Chinese junk but it was about 40 bucks vs $100+ with barnette or stock.

Title: Re: You are gearing this final drive wrong
Post by ThumperPaul on 11/12/24 at 13:44:33

Here’s a pretty cool sprocket calculator that shows the changes in torque and top speed. There are more elaborate calculators, but I like this one for simplicity.

https://sprocketcalculator.com/

The stock belt drive final drive is 68T/23T = 2.96 (as you vaguely noted).

I figured you could still hit 75 (kinda joking). Top speed for stock is pretty well tested around 93-95. I’ve had the S40s I’ve owned up to about 85. That was fast enough before thing’s seemingly might want to vibrate apart. They all still had a little bit left, so 93 seems doable with the right conditions.

Yeah, 4th and 5th is where I’d expect you to notice the most difference. You actually still have some real torque to use with the lower gearing. While the calculator suggests about an 8% reduction in top speed with the lower gearing, I doubt it’s that big a reduction since you can probably get higher rpms in 4th and 5th with the lower gearing. The calculator rather falsely assumes you can hit the redline before lowering the gear ratio.

Title: Re: You are gearing this final drive wrong
Post by ohiomoto on 11/12/24 at 16:54:43

Sounds fun! It might be a perfect match for this motor's limited power.

Title: Re: You are gearing this final drive wrong
Post by zipidachimp on 11/23/24 at 11:32:46

My stock S40 is always searching for 6th gear!
Cheers! 8-)

Title: Re: You are gearing this final drive wrong
Post by Dave on 11/23/24 at 12:31:39

The short gearing may be good in town - but I really do like my tall gearing for the way I ride.

My 50-60mph rides on the country roads are done in 4th gear and I can cruise along without any shifting. On the highway over 60mph I have a 5th gear overdrive......3,500rpm at 60mph and 4,000 rpm at 70mph. My modified engine pulls the taller gearing very well.

Just for kicks I went back to stock gearing last month, and I could not believe how bad it felt. My 50-60mph country road ride was all done in 5th gear and the engine sounded wound up all the time....it just sounded like I was working the engine way too hard!

Title: Re: You are gearing this final drive wrong
Post by ThumperPaul on 11/23/24 at 13:07:17

Philly likes shorter gearing.

Dave likes taller gearing.

DragBikeMike’s hotrod breaks 5-speed gearboxes.

Zipi is constantly searching for 6th gear (me too).

Suzuki tries to please everyone with the middle of the road. No one is happy and it gives us a reason to modify. lol.

Title: Re: You are gearing this final drive wrong
Post by Surviving Philly on 11/25/24 at 12:40:04

Dave I have to agree with you about the Rpms. I sound like I'm riding a weed whacker.

Title: Re: You are gearing this final drive wrong
Post by zevenenergie on 11/26/24 at 01:22:36

I have a squking belt, and the double row ball bearing change already done.
I find the noise is at the expense of my riding pleasure.
So I am thinking about a chain.
Because because I live in an urban area I don't go on the highway much I want to try a lighter transmission given your enthusiastic reaction :)

I think I,ll make a chain protector.

Title: Re: You are gearing this final drive wrong
Post by JOG on 11/26/24 at 17:42:24

Loosen the belt. There are Dry Spray lubricants you can try. I used Gulf canning wax. It got messy. But the squeaking after it got wet was tough.

Title: Re: You are gearing this final drive wrong
Post by Alzuki on 12/02/24 at 17:53:28

Newbie here, trying to nail down some decisions for winter projects for my 2002.

One is about wheels. I have the stock spoked wheels, but the bike also came with a set of GS550 alloys in 16 x 2.5 rear and 19 x 1.85 front. They look good, but there are complications. Brake rotor, tire size on such narrow rims, custom made axle spacers, etc.?

One question was what will the taller rear wheel do to the gearing? The calculator below, which I think I got from another post on this site, has been very helpful for my wheel and tire decisions:

https://www.gearingcommander.com/

Now all I have to do is calculate (interpolate) the gearingcommander results to see if I can figure out from sprocketcalculator (thanks for the link!) what effect my choices have on power and torque.

Title: Re: You are gearing this final drive wrong
Post by zipidachimp on 12/02/24 at 21:59:37

I've got the same rear. 120/90-16 Kenda has proven perfect for me. Remember, this is a 30hp bike!
Cheers! 8-)

Title: Re: You are gearing this final drive wrong
Post by faffi on 12/03/24 at 23:59:23

The clutch that was mentioned have an easier life with shorter gearing. Personally, though, I like loafing engines, not screaming ones. YMMV

Title: Re: You are gearing this final drive wrong
Post by blod on 12/04/24 at 04:47:07

I think I might be missing something here, but what's the point , what's wrong with the belt drive ?

Title: Re: You are gearing this final drive wrong
Post by ohiomoto on 12/04/24 at 18:53:04

You're missing the "gearing" part. That's the point. The OP is sharing their experience with lower gearing.

Title: Re: You are gearing this final drive wrong
Post by faffi on 12/05/24 at 11:41:53

Lower gearing, provided you do not rev the snot out of the engine (often), could perhaps prolong engine life. High loads at low rpm will stress the gears and the cam chain, and lower gearing will/can reduced this to a degree. Still, I think I would opt for a little taller gearing than stock, and just wait until 50 mph to engage top gear under light load, higher speeds if the load is high.

Title: Re: You are gearing this final drive wrong
Post by Surviving Philly on 12/05/24 at 15:04:29

It's just tremendously fun with the shorter gearing. It's a shame is so cold in the city right now... Last two winters were pretty mild this one's killing me.