70-tooth rear Pulley swap for 2021 Low Rider S?

[JamesButler]

Is there an OEM or aftermarket 70-tooth rear belt Pulley that can be swapped onto the 2021 Low Rider S - with minor-to-no spacing changes?  Anyone here done this swap? The stock rear pulley is p/n 40325-07 (black). Specs are 66-tooth, 7/8"-wide with a 24mm 134t belt. 

[JamesButler]

More specifically, maybe an '06 Softail rear pulley - p/n 40599-06 (70-tooth) will bolt on to the 2022 Low Rider S to replace the 66-tooth rear pulley p/n 40325-07.  Anyone know if the MoCo changed the pulley bolt pattern from '06 to '07 for the Softail? If my fact-checking is correct then:
-Belt-tooth difference is one-tooth 135 for the '06 p/n and 134 for the '07 p/n.
-Belt width difference seems to be 4mm. 20mm for the thinner '06 and 24mm for the '07.
-Not sure of the difference in pulley width, if any, which I'm guessing would change spacer thickness when bolting it on...

The reason for the swap is to shorten the overall gearing.  Also would swap in an Andrews 31-tooth trans pulley instead of the stock 32-tooth trans pulley to further shorten the overall gearing for @ 260rpm  difference @ 75mph...   

[rigidthumper]

I did a 30 tooth trike pulley and a 68 tooth sportster pulley, and kept the stock belt but it was on an earlier model bike.

[JamesButler]

I did a 30 tooth trike pulley and a 68 tooth sportster pulley, and kept the stock belt but it was on an earlier model bike.

I like it.  What model/year bike?

[rigidthumper]

2007. AFAIK, it has the same bolt pattern as yours, just uses a different thickness belt, and a pinch less offset.

[JamesButler]

2007. AFAIK, it has the same bolt pattern as yours, just uses a different thickness belt, and a pinch less offset.

Great stuff! Thanks for the info. It looks like either the 68-T or 70-tooth rear should work, but I don't think the 30-T trans pulley will work. However, Andrews makes a 31-t trans pulley for the M8, which means the 70/31 combo is the best I can do, and it's fine.  It'll provide about @262 more rpms at 75mph.  Similarly, all things equal, your 68/30 combo choice would provide @ 274 more rpms.  Nearly the same!

[rigidthumper]

The tri glide pulley has been the same since 2011, and the transmissions use the same main drive gear (35122-06A) on all M8 models, so physically it should work. (and the HD unit is only ~$70) May be a difference in offset, or thickness, but it doesn't appear so in the catalogs?

[JamesButler]

The tri glide pulley has been the same since 2011, and the transmissions use the same main drive gear (35122-06A) on all M8 models, so physically it should work. (and the HD unit is only ~$70) May be a difference in offset, or thickness, but it doesn't appear so in the catalogs?

I see your logic.  For $70 it's worth trying it out.  I use a 70/30 on one of my FXRs.  My thought was since Andrews has at least two different 31-T pulleys -one listed specifically for the M8, and the others listed for previous models- then the earlier model 30-T that they list along with the earlier-models 31-T would be non-compatible with the M8. The fact that they don't list a 30 for the M8 seemed odd to me.  Maybe there's no demand for it yet, but maybe as you imply, it's because the MoCo's 30-T is readily available for the M8. 

[rigidthumper]

And the possible offset distance, but I'm not certain (I have spent more at the casino, so...)

[VernDiesel]

I have a Sport Glide that I did a 30 sprocket 70 pulley on. (3.15 final drive ratio) The 30 sprocket from a trike simply had to have the thickness or depth of the sprocket milled down to match that of the one from my Sport Glide. (In order to fit in the narrower softail case cover) Been running them over 20k miles now. For reference 116 HP 6k limiter.

I plan to go back to the original sprocket but keep the 70 tooth pulley. (2.98 final drive ratio) This will be the ideal or the optimum gearing for my performance street riding use. The lower gearing really only makes a practical difference in 1st & 6th gear. Theoretically I can launch harder now but wheel spin is the limiter so. Plus you run out of first gear so quick sometimes its hard to get your foot there and make the shift before hitting the rpm limiter. On the street normal riding you are shifting to 2nd before making your turn from an intersection. Rather annoying. But you can leave a light really nicely from 2nd. Only you have to stop at or find 2nd when you come to a stop instead of automatically dropping to 1st gear.

I live near the intersection of east west and north south Interstates. Practically speaking I ride the interstate a lot. I often run at 80mph. At 80 I am at the meat of the torque curve.  This is fun but revs it more than necessary, eats a little more fuel and cuts your range some. Not a big deal to some just less than ideal to me. 

Top speed. While I still run the Harley Pro Street tuner I have an on off switch for the speedometer.  I can switch it off on the fly so as to have no governor. Everything else works and I can see speed on my phone GPS. With the 30/70 the bike pulls like 5th gear for a 116HP bike in 6th gear. So it pulls like a freight train right up to 140 mph where at 5,800 rpms falling torque meets rising drag (torque) requirement and it stops accelerating. With a little taller gearing I would still have more torque at that same speed to provide a little more top speed. I don't really care about this just thought it worthwhile noting.

Harley now has the softail gearing at a tall 2.79 final drive ratio for emissions & perhaps fuel economy. T Man performance had/has on his site a reference that says to the effect that for most HD engines optimum performance gearing should have about a 2.96 final drive ratio to best keep the engine operating between max torque and maximum HP. A drag only bike gearing often benefits from an even lower final drive ratio if its not strong enough to reach its top hp in the one to one gear. (6th)

[louloupa]

I also have a Sportglide . To shorten the gear ratio, I changed the rear tire from 180-70-16 to 180-60-16. The difference is 6%, it's like a 30 tooth front sprocket, instead the 32 teeth stock .
 I mounted a heritage shock absorber which raises the rear by 1"

[Winston Wolf]

I think the purpose of the tall gearing in the softail is to keep the vibration down.  I just got a new LRST, and I'm skeptical of all day freeway pounding. The vibration over 3k rpms starts to get pretty bad...  10 miles of up and down speed/rpms, and my hands are asleep.

[VernDiesel]

You think the uber tall 2.79 final drive ratio gearing of the newer softails is not for emissions & fuel economy but rather to make it a smoother ride?  But you get numb hands anyway.  Hands butt feet triangle is where ergonomic comfort is determined according to MoCo. Page 160 of the 2020 parts catalog has some description pictures & explanation. Find the right seat hand and peg position and the numbness problem should go away. The right grips might band aid it a bit also. But the 18+ softail chassis and motor counter balancers do a good job of eliminating numbing type vibrations.

If you are tall the MoCo Tallboy seat moves you up and back which really helps. Forward controls also help on a low seat height bike as do floorboards since you let your feet fall to a naturally comfortable position on them instead of moving your feet to a where the peg is. After butt & seat is when I do bars if at all.

For what its worth at 55 years of age I rode over 1,000 miles in one day on my way to Sturgis the other year.  At the end of the day I was tired but not beat sore or numb anywhere and that was on a Sport Glide ie the same softail platform and fore runner if you will to what you have. Also since I'm tall with 36" inseam, like louloupa I raised the rear of the bike which is also what MoCo did on the 2022 LRS-T.