Topic: Gearing with 17” rear wheel

[Johnny340]

So, my 1975 CB750F has 17/47 gearing (520) but with a 17” rim (tire is 160/60ZR17). This is too low gearing imo. I’m going to have a 520 rear sprocket made and wondered if anyone has a good recommendation for rear sprocket size. 40? I like the idea of smaller rear for chain clearance too.
Engine is 836 with big cam and good power.

[Don R]

 I liked 18/47 on my F1. Not sure how tall my 18" tire was though.

[Johnny340]

I'd have to do the math to figure this out. Your ratio is 2.611 and mine is 2.765 but your tire diameter is about 2" bigger.  (My tire is 24.6" diameter and a 120 tire in an 18" is about 26.5".)  Not sure what that 2" would do to the overall ratio.  Any math wizards out there?  Or anyone who has run a 17" rim with a good gear ratio?  I'm at 5500 RPM on the freeway.

[scottly]

How fast are you going at 5500 RPM?

[bryanj]

You need 530 not 520

[slikwilli420]

You need 530 not 520

If you're doing the work already, 520 is a great way to go, plenty strong and lots of great chain options out there. Im running 17s on my race bike and have 17/46 gearing on there right now. Granted, its a race bike so lives above your cruising RPM and makes strong power, but its a good place to start.

[Johnny340]

How fast are you going at 5500 RPM?

5500RPM is about 110km/h or 68mph which is a little high of an RPM to be sitting at imo.

Has anyone run a 40T or 42T with the 17T counter sprocket and a 17" wheel?
I converted to 520 mostly for tire clearance.  Fyi, PBI sprockets is no longer making new sprockets but Rebel Gears is.

[Scootch]

I changed my '70 K0 to 19T front end 43T rear sprockets bcz I found the gearing to be too low. If you want to search for my write-up from earlier this spring. I included the gearing calculator and links to where I purchased the sprockets. I can't link to it now bcz I'm on my phone. You will find the gearing calculator to be very handy...

[Scootch]

Here is the write up I did...
http://forums.sohc4.net/index.php/topic,189718.msg2205328.html#msg2205328

[Johnny340]

Thanks for the link Mark.  I didn't see that when I searched here.  I'll check it out and order a sprocket.

[Alan F.]

Online tools like:
https://www.tacomaworld.com/tirecalc
And:
https://www.gearingcommander.com/

Would probably help with the math.

[Johnny340]

That gearing commander link is amazing!
I got a 41t 520 sprocket made by Rebel Gears and it is way better!  Just right around town and less RPM on the highway.  Plus I have more clearance for the chain both at the front of the swingarm and beside the shock. 
So, anyone searching, the 17/41 with a 17" wheel is perfect for the power of an 836. Slightly taller than the other taller gearing ratio from Honda.

[Don R]

https://www.gearingcommander.com/

[slikwilli420]

That gearing commander link is amazing!
I got a 41t 520 sprocket made by Rebel Gears and it is way better!  Just right around town and less RPM on the highway.  Plus I have more clearance for the chain both at the front of the swingarm and beside the shock. 
So, anyone searching, the 17/41 with a 17" wheel is perfect for the power of an 836. Slightly taller than the other taller gearing ratio from Honda.

Lord that's a tiny rear sprocket. Gotta be difficult to get it to even rev where these engines like to live.