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Sprocket sizes

By Mike Penley,
in DRZ400/E/S/SM

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Apprentice

Mike Penley

Posted
Posted

Hello. 

I've got a 2007 DRZ400S with a combination of 16/39 sprocket sizes. This is my second bike that I'm using mostly off road. Can anyone tell me what the ideal use of a motorcycle is with this set up? 

My thoughts are higher top speed for road use with some downplay of off road in 1st gear. 

 

Cheers, 

 

Mike. 

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Grand Master

76xtdrvr

Posted
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3 minutes ago, Mike Penley said:

Hello. 

I've got a 2007 DRZ400S with a combination of 16/39 sprocket sizes. This is my second bike that I'm using mostly off road. Can anyone tell me what the ideal use of a motorcycle is with this set up? 

My thoughts are higher top speed for road use with some downplay of off road in 1st gear. 

 

Cheers, 

 

Mike. 

It's geared super high, probably to keep the revs down at highway speeds. If it's an engine/carb setup with very few mods, it won't do much good off road. Chances are it would even have a hard time accelerating too well at highway speeds without downshifting.

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Grand Master

Augoose

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No, not cancelling - you are pretty far away from stock.

Here's the speeds for DRZ400S stock (USA) gearing at 15/44...

image.png.92a0dd66960fe99346b381e110637d0b.png

 

And here are the speeds for your current gearing at 16/39, You are certainly geared high for street riding.

image.png.9a4e126ba192ea72f2edd86bf7d7ccc8.png

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dad2u

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1 hour ago, Mike Penley said:

The front is one up on standard & the back is two down. Is there not a bit of cancelling out here? 

?

No...in fact they are both acting to decrease rpm for any given speed: the 16 versus the 15 means that for each revolution of the front sprocket you get 1/15 more chain movement.  On the back, normally the gear has 44 teeth, so the chain has to move 44 links for each revolution of the tire....in your case this is only 39 links.  So your setup gives more chain movement per rpm because of the larger front sprocket, and the rear wheel revolves more times for the same chain movement due to the smaller sprocket.  They are both acting in the same way to reduce rpm at speed.

For off-road I have gone to 14/48 with 112link chain, but found that this was more than needed.  The DRZ has quite a bit of low end grunt, and will be happy at 15/48 in the trees and rocks, yet be able to do 60mph without reving to insane levels.  

I have a second set of wheels for my more street oriented riding, and chose to keep the same chain and countershaft sprocket, so have found that 15/43 will work with the 112 links, and this substantially drops the rpm at highway speeds.  (I don't ride above 60mph much....).

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bumtarder

Posted
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2 hours ago, Mike Penley said:

The front is one up on standard & the back is two down. Is there not a bit of cancelling out here? 

?

You are very confused on your bike's final drive ratio. The front is up one from the standard 15 but the rear is not down two from standard, it is down 5 from the standard 44 on the S model. You are confusing your bike with the SM models' 15/41.

Anyway, there is no cancelling out going on. It doesn't work that way with the gearing specified. Both your front and rear sprockets are going taller than standard to make your bike too high geared for off road use or green laning as you guys call it. This causes a drastic loss of low end torque.

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Grand Master

ss-racing66

Posted
Posted
5 hours ago, Mike Penley said:

Hello. 

I've got a 2007 DRZ400S with a combination of 16/39 sprocket sizes. This is my second bike that I'm using mostly off road. Can anyone tell me what the ideal use of a motorcycle is with this set up? 

My thoughts are higher top speed for road use with some downplay of off road in 1st gear. 

Cheers, 

Mike. 

Land speed records is my guess , that’s super tall gearing 

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Grand Master

Tony Wyp

Posted
Posted (edited)
11 hours ago, Mike Penley said:

Hello. 

I've got a 2007 DRZ400S with a combination of 16/39 sprocket sizes. This is my second bike that I'm using mostly off road. Can anyone tell me what the ideal use of a motorcycle is with this set up? 

My thoughts are higher top speed for road use with some downplay of off road in 1st gear. 

 

Cheers, 

 

Mike. 

I have run 16:39 for over a decade on my SM. It's a touring ratio. 17" wheels.

With an 18" rear wheel, I go down to 15:39.

16:39 is a VERY tall ratio for an S.

Edited by Tony Wyp
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Grand Master

bumtarder

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4 hours ago, Mike Penley said:

My Clymer manual states on both S & SM models a 15/41 set up 

IMG_20210907_075904.jpg

Hence the problem. You have a Clymers. Get a genuine Suzuki factory manual for accuracy. For the record these bikes had the following standard final drives;

E and Kicker----- 14/47 ( 3.36:1 )

S -------  15/44 ( 2.93 :1 )

SM ------ 15/41 ( 2.73 :1 )

 

 

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Grand Master

76xtdrvr

Posted
Posted (edited)
15 minutes ago, Mike Penley said:

Thanks. I've realised that now with all the helpful info I've received. Something as important as sprocket sizes should be correct in a manual. 

I have a Clymer manual for my drz and use it often, including when I tore down and reassembled my top end. No manuals, including OEM are perfect, and I wouldn't consider a wrong sprocket size in a manual all that important. I have an OEM KTM manual with an incorrect SAE size for a piston diameter. Now that is important. (KTM haters are free to reply with comments) ?.

Edited by 76xtdrvr
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Apprentice

Bruce Cameron

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Hi Mike, looks like you have an E by the pic, however that's not important for the purpose of the discussion. The close ratio gear set , read "ratio spacing" limits potential for achieving a low enough first and tall enough top gear for sustained highway/road use. My Australian delivered E came with 14/47 which will climb a wall but screams like a Banshee at anything over 80km'h or so, or at least feels like it is. I went to 15/44, first is tolerable for tight single track, if not ideal and it now sustains 100km/h on road legs to and from without sustaining higher revs than I'm comfortable with. It's really a personal preference thing, type of off road, ability, clutch and throttle control, etc. There's no right or wrong. I can gear it higher still but will start to seriously compromise the first gear, making it too fast/revs too low off road. I live in a Highland area with very challenging terrain off road, "and" also have lengthy freeway commutes to and from local national parks and such, so it's ultimately about arriving at the best compromise. It's simply what works for me, you may find different where you are. Don't overthink it, buy a selection of sprockets and experiment, front sprockets being the cheapest way to achieve this. The added bonus is that you can normally swap them out with enough adjustment in the chain to avoid changing chain length, thereby committing to the change without an easy way to undo if not found to be ideal. The 38 on the rear is, as others have said, considered very tall. Going to say a 41 or 44, and swap out a 14, 15 as desired from there will bring the bike to life, remember it's only a 400cc and it isn't designed to be lugged like a DR650, KTM LC4 or the like. As a guide, you could comfortably sustain 70mph all day with a 15/41 combo, 60mph with 15/44 no worries. For every front tooth equates to 3 teeth on the rear as a rough guide, either up or down doesn't matter, the relationship remains intact. If you have an E model, 15 teeth at the front is about the limit without chewing up the swingarm mounted chainguide, hence my choice of a 15t front. 

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