Front sprocket change
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Cruiser
Joined: Apr 2012
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From: Seymour Indiana
I don't know what my complete gearing is or how to go about figuring it up? . I can count the rear tommorrow not sure about the others or what I need info you need? I'd like to know myself as this softail rock-n-rolls now!
Last edited by SteveB1971; Oct 13, 2014 at 07:28 PM.
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From: indiana
I did check this today with my gps my primary drive is 45 front 71 rear 1.57778:1 my final drive is 32 front 65 rear 2.03125:1 so my overall is 3.20486:1 tire size is 250/40-18 according to the numbers I should be at 84mph at 3500 rpm and what I got was 83.2mph at 3500 rpm I think that's close enough maybe my tach was off a little
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From: LA
Jeez, and to think in the old days we used to calculate it by counting the street light posts as we rode by going ... one crocodile, two crocodile, three crocodile. Now everyone carries military grade, satellite controlled 1,000ths of a second technology in their pocket ...
Thanks, that was interesting.
Steve, I'm guessing everything else in your bike is just stock, so it's just the rear pulley which may or may not have been changed.
Let us know how the high speed run feels or where the vibes kick in.
Thanks, that was interesting.
Steve, I'm guessing everything else in your bike is just stock, so it's just the rear pulley which may or may not have been changed.
Let us know how the high speed run feels or where the vibes kick in.
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Cruiser
Joined: Apr 2012
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From: Seymour Indiana
66 or 67 on the rear pully.. First time I counted I got 67 second time I got 66..Is that stock for a 1993 fatboy? I'm going out to count again ...
Last edited by SteveB1971; Oct 14, 2014 at 10:37 AM.
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From: LA
With a 25T Compensating Sprocket.
37707-98A clutch is, what, 36T?
So you have ...
21T to 36T, then 32T to 66T
... and hit a sweet spot?
Overall Drive Ratio = 3.53? (3.53 to 1)
I think I have 3.75 due to a 70T rear pulley and am a little concerned it's just too much. It'll do for the application in question but I worried it will revving too fast at hiway speed.
On paper it says,
3.15 @ 70 mph = 2900-2950 rpm
3.37 @ 70 mph = 3100-3150 rpm
3.75 @ 70 mph = 3450-3500 rpm, therefore 80 @ 4000 rpm, 85 @ 4250 rpm.
Not a typical H-D experience but right on maximum torque.
Last edited by Dun Roamin; Oct 14, 2014 at 06:06 PM.
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Cruiser
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From: Seymour Indiana
Are you meaning mine set up for maximum torque? You meaning I'll have a hard time finding a sweet spot with my gearing? I'm ignorant on what the numbers mean
Last edited by SteveB1971; Oct 14, 2014 at 01:47 PM.
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Cruiser
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From: Seymour Indiana
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From: LA
Yes, there were 66T sprockets, e.g. the 40221-07 on the Dynas or 40217-07 on the Touring.
How wide is your belt, Steve? 1", 1 1/8", 1 1/2"?
No, I was being positive, you've found a sweet spot amongst the gearing options that suits your bike and the way and speeds you ride.
I don't know because I am not a pro and was not involved at the time your bike was made but according to the parts catalogue, it suggests someone may have changed your rear pulley to change it from a 70T to a 66T ... which would mean to be slower acceleration, but to run at lower RPMs at high speeds. Some folks like that.
You've made it more torquey.
The 21T to 36T, then 32T to 66T relates to number of teeth (T).
The ratios are the turns of cogs or pulley, e.g. 3.53 turns of the drive shaft would turn 1 turn at the other end. The higher the number the more torque or pull it would have (but the quicker it would run out of breath). If you make it too high, it will accelerate off the line quickly, or pull a heavy weight like a sidecar, but not go high speed.
It might be worth you counting the number of teeth on your belt in case it ever breaks and you need to replace it. Best way is damp some white Tippex or a paint spot on it and count it from there.
How wide is your belt, Steve? 1", 1 1/8", 1 1/2"?
I don't know because I am not a pro and was not involved at the time your bike was made but according to the parts catalogue, it suggests someone may have changed your rear pulley to change it from a 70T to a 66T ... which would mean to be slower acceleration, but to run at lower RPMs at high speeds. Some folks like that.
You've made it more torquey.
The 21T to 36T, then 32T to 66T relates to number of teeth (T).
The ratios are the turns of cogs or pulley, e.g. 3.53 turns of the drive shaft would turn 1 turn at the other end. The higher the number the more torque or pull it would have (but the quicker it would run out of breath). If you make it too high, it will accelerate off the line quickly, or pull a heavy weight like a sidecar, but not go high speed.
It might be worth you counting the number of teeth on your belt in case it ever breaks and you need to replace it. Best way is damp some white Tippex or a paint spot on it and count it from there.
Last edited by Dun Roamin; Oct 14, 2014 at 05:46 PM.
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From: Bedford UK
Actually quite the opposite! If all else is unchanged, then replacing a 70T rear pulley with a 66T reduces torque at the rear wheel to 66/70 = 94% of stock gearing. It also reduces rpm at any given road speed to the same amount, so 3,000rpm will become 2,828rpm.