REPRINT FROM OLD HTT: SHORT (3.37 GEARING) VS TALL (3.15 GEARING)??? WHY?

[ClassicRider2002]

DISCLAIMER: THIS IS A REPRINT TOPIC FROM "OLD" HTT

I have saved many great topical discussions as "links" over the years and would hate to see these lost, so I am reprinting this TOPIC here, which may "perhaps" help some.

TOPIC:  SHORT (3.37 GEARING) VS TALL (3.15 GEARING)? ? ? WHY?  04-07-2008

From: fltri2  (Original Message) Sent: 4/7/2008 2:02 PM   Message 1 of 47 in Discussion
I have noticed there are a lot of guys changing their primary gear ratio to 3.37.  I have but one question:
WHY?
Are these guys racing their bikes in the quarter mile?  Are they looking for the quick bar-to-bar hop?  Looking to spend more money on gas?  What I feel is the more torque available the "taller" the gears can be.
So...as an example, if you have a 117ci engine with 120lbs torque @ 2200-up I would go to a 66tooth rear sprocket to lower the revs per mph, not the other way around.

Why do the most powerful drag bikes/cars have but 1 or 2 gears? Why not have 5,6,7, or 8 speeds for the quarter?

The answer is the engine produces enough torque to "pull" the tall gears, rather than shift, rev, shift, rev, shift, rev,etc.
A stock 08 96ci bike cannot "pull" 6th gear adequately, but after a big bore kit and a good set of cams it will pull 6th no problem.
So why not build an engine with a ton of torque, then slow the engine rpm-per-mph down so the fuel mileage goes up and the fun factor does as well, because it's really nice to have a bike with "legs" of power instead of shift, shift, shift, shift.
Just my personal opinion of the primary gear changing going on.   Bob

[ClassicRider2002]

From: Jmorton1011 Sent: 4/7/2008 2:33 PM  Message 2 of 19 in Discussion
I understand what you're saying perfectly & if I had a 145" motor (don't I wish) I wouldn't run stiff gearing either.

I do have about as hot a 95" as you can build & it is definitely a TQ motor, but it is WAY more fun to ride with 3.37 gearing.

By the way, swapping from 3.15 to 3.37 gearing didn not seem to affect my gas mileage at all (with my Woods carb I can get almost 50 mpg if I want to although that never happens because I beat the SH** out of it)

On the other hand, a buddy of mine tried 3.37 gearing in his basically stock 88" Softail standard & said it lowered his mpg so much he swapped it back to stock again........~John
   

From: fltri2 Sent: 4/7/2008 2:40 PM   Message 3 of 19 in Discussion
John,
You are 100% correct when you say a 95" with 3.37 gearing is more "fun" than stock primary gearing, BUT my comment is basically geared towards the Big Inch touring crowd and fuel mileage ($4.00+ per gal coming soon to your neighborhood).
I just returned from a 2500+ mi trip to Arizona and back and got 44mpg @ 90+ mph. I did this test twice over a 175mile range and took just under 4 gals each time.  I imagine mileage would be over 50mpg under 80mph.  I should have qualified my statement(s) for x-country touring, rather than hotrodding.  Bob


From: Jmorton1011 Sent: 4/7/2008 2:53 PM   Message 4 of 19 in Discussion
Well, I'm not a long distance rider as much as I once was (I once years ago rode home non stop 32 hours from Sturgis on a rigid frame to get to work on Monday morning), but I am riding a   Bagger   & even with the gearing I can get good mpg if I want to (I just hardly ever want to)  ~John
   

From: Hillsidecyclecom Sent: 4/7/2008 2:54 PM   Message 5 of 19 in Discussion
The 3.37 ratio was stock on a lot of models over the years.
You can also "step" on the CR a bit more with a geared bike, as it will not load the engine as hard.


From: munkeywithlobo Sent: 4/7/2008 3:10 PM   Message 6 of 19 in Discussion
Bob,
You and I see things the same way...     Lower gearing can help control wheel spin though as the motor can't rev fast enough to break the tire loose. I'd prefer 3.15 and add wider tire if the tire spins.. Bruce


From: SS124FL Sent: 4/7/2008 3:23 PM   Message 7 of 19 in Discussion
Bob......simple why not?

Some people like jack rabbit bikes, some dont. I like it in big inch builds as well as smaller builds. I had 337's in my bike stock, 95,98, 103,117 and 124. Whats wrong with wheel spin...Let face it, some of our speed limits are broken in second gear, so i dont see a need to pull the stock gearing. I just like they way it matched my riding style. If i am planning a big trip, i might switch back, might not...


From: ViennaHog2003 Sent: 4/7/2008 6:10 PM   Message 8 of 19 in Discussion
big motor + tall     gearing makes sense
big motor + short gearing makes fun
 

From: fltri2 Sent: 4/7/2008 6:54 PM   Message 9 of 19 in Discussion
Vienna, 
Couldn't say it better,
Bob
   

From: oldschool Sent: 4/8/2008 9:57 AM  Message 10 of 19 in Discussion
As usual Oldschool goes out on a limb on this as in Bruce and I or on the oppsite sides of it. The other unusal side to this is I'm with Hillside on this...LOL

I have a heavy 124CI FLHT with a lttle too much RUB wrap per the purist, plus I'm not a lightweight either. Too me it's not about trying to make a bar hopper out of bagger, it's what the lower 3.37 gear does for me at in the 55-75 MPH range in 4ht and 5th gear, which is where I spend the most time riding.

My engine is rated by S&S as a 10.8:1 compression engine, the cam I'm using in it is a S&S 640. If you look at the spec on that cam, with it's long duration, lots of overlap, and late intake close, I believe all of you will say this is not a low end rpm cam, at least for most.   

Like Hillside said , the lower gearing's mechanical advantage helps with both the high compression ping issue and I'm betting that it helps with normal riding gas mileage to as for me at least the engine's RPM are more in sweet spot in 4th and 5th gear. Due to the gearings higher mechanical advantage, it takes less throttle opening to maintain speed. Less throttle opening less gas used. 

I also live in area of Tennessee where elevation can go from 200 feet above sea level to over 5000 feet above and a lot of 2500-4500 feet changes and 99% of this type riding within 15 miles of my home and the + 5000 feet is only 45 miles away. In other words not a lot of flat land, but a lot of what some of you see that live east of the big muddy.   

Also most of my riding is on 2 lanes roads with legal speed limits of 45-55 MPH. This is the type riding where the 3.37 really shines with a big motor, by keeping the engine in it's power band or closer to it, in rpm in 4th and 5th where your more likly to lug a bulk cube inch engine at that speed range. 

So Bob, I ask you, what RPM would you say most of these bulk cube engine are truly in their power band and what RPM in either 4th or 5th  will do they need to be at to allow them to accelerate without downshifting and not have a hint of lugging? Don't you think 3.37 gearing just might be a better choice for a heavy bike over taller gearing to help the engine out?  Remember we are talking heavy bikes.

I'll bet you there are very few Baggers, no matter what their massive peak TQ is that can handle WOT rpm below 3200 in 4th or 5th gear without a hint of lugging. At below 3200 RPM even rolling into the throttle too accelarate can be a problem for a lot of these bulk cube engines and require a lot of up shiffting and down shifting when riding terrain like where I live. Riding is so much more fun when you gear the bike to what helps the engine move the load it's saddled with IMO.  I get to spend a little more time enjoying the ride and a little less time downshifting and upshifting to keep the engine in it's power band so I don't lug it. 

Believe me, I spend a lot of time riding in 4th gear as my bulk cube engine with the aid of 3.37 gearing is very, very happy to haul my Lard A$$ at 55 MPH in it. Y'all can run 5th gear if you want to and wear that piece of crap metal shift lever HD sells now out or take your bottom end out if you ride my style of roads....LOL   

My vote is to each his own. Run what you feel is best for your bike and riding style and enviroment and to Hell with what someone else thinks is best for you.   If you want to understand a mans thinking, then take a walk in his shoes or in this case a ride... 
   

From: hotbo Sent: 4/8/2008 10:49 AM   Message 11 of 19 in Discussion
i changed my 99 fxwg with a 95 inch motor to 3.37 recently made very little difference as far as rpm i can tell.i can really tell it thru the gears though much quicker imo.i ran 80 plus on the interestate 2 weekends ago in the rain for 200 miles i got 43-44mph not bad in my opinion.  Didnt act like it was to low for me in anyway.  travis


From: rokinrider Sent: 4/8/2008 1:56 PM   Message 12 of 19 in Discussion
What is stock gearing on an 00 FLHT? ? ? Just curious 


From: surf10011 Sent: 4/8/2008 1:59 PM   Message 13 of 19 in Discussion
Dumb question,
3.15    3.37
Which one's high or tall, which one's low or short?


From: kdietz Sent: 4/8/2008 2:01 PM   Message 14 of 19 in Discussion
3.15......tall........high
3.37......short.....low


From: Neckball Sent: 4/8/2008 2:09 PM   Message 15 of 19 in Discussion
I am 100% certain that 3.37 final gearing was the stock gearing for the MM EFI baggers from 1999-2001.  The carbed Baggers were running 3.15 final gearing from 1999-2001.  From 2002-2006 all baggers were running 3.15 final gearing.  That's why it's an easy change, it's done with OEM parts. Great results with minimal expense, time or labor.


From: Road-King03 Sent: 4/8/2008 2:10 PM   Message 16 of 19 in Discussion
What is stock gearing on an 00 FLHT? ? ?

3:37 if it's injected, 3:15 for carbs.
Rick
 

From: surf10011 Sent: 4/8/2008 2:12 PM   Message 17 of 19 in Discussion
Was it changed in the primary or the final drive?

     
From: Road-King03 Sent: 4/8/2008 5:54 PM   Message 18 of 19 in Discussion
Was it changed in the primary or the final drive?

Primary, with Compensating Sprocket and Clutch Shell Basket/Ring Gear.
Short/Low Gearing 24T Compensating Sprocket  37T Clutch Shell Basket/Ring Gear  OEM For 1999-2001 MM EFI Baggers
Tall/High Gearing    25T Compensating Sprocket  36T Clutch Shell Basket/Ring Gear  OEM For 1999-2001 Carbed Baggers
Tall/High Gearing    25T Compensating Sprocket  36T Clutch Shell Basket/Ring Gear  OEM For 2002-2006 For Both Delphi & Carbed Baggers

Rick

     
From: oldschool Sent: 4/8/2008 9:30 PM   Message 19 of 19 in Discussion
Bob,

Botton line I don't knock people for using taller gearing, I only stated my WHY case for it not being my choice. So if you think I'm stupid for having a combination of primary gear and rear sprocket gearing that gives me 3.37 5th and 2.93 6th gear then that's your privelige.   

[ClassicRider2002]

Anything added beyond this point is new information.

Regards,

"Classic"

[ClassicRider2002]

I actually have a excel spread sheet that was provided within a THREAD here at HTT by:
From: Fuzznut5197 Sent: 6/13/2008 7:01 PM
Anyone have any use for this driveline spreadsheet? It was posted here back in 2003, and I thought is was saved somewhere in HTT, but I can't find where.

Hopefully all will be able to down load the EXCEL PROGRAM below next to the "paper clip"

If you plug in your actual gearing (comp sprocket "T"ooth size, clutch shell basket/ring gear "T"ooth size, rear wheel sprocket "T"ooth size, transmission "T"ooth size as well as rear wheel diameter then it will factor RPMS and such which would aid you in determining what level of gearing you might benefit most from........then if you wish to ponder some other options for your comp gear or your clutch shell basket gear or perhaps your secondary gearing which might require a different belt you can see what might create the biggest bang for your buck.....

[NOTE: Please remember that putting your cursor next to the paper clip icon below will allow you to open this EXCEL PROGRAM, if you desire simply choose to save the program to your computer as well]

[attachment removed after 60 days by system]

[ClassicRider2002]

Hello Everyone~~~

Through out all of the "old" THREADS that deal with the 3.37 Gearing Modifcation to our TWIN CAM BIKES I really enjoyed reading them....and after all of the valuable input from everyone whom posted, I eventually did the MODIFCATION to my 2002 RKC.  Like many before me have stated and I must concur, this MODIFICATION has to be ONE OF THE ABSOLUTELY BEST MODIFICATIONS I have done to my "BAGGER", it's such a wonderful "bang" for the buck invested....

Thus I put together a detailed THREAD about the modification, if you are interested in reading about such Simply CLICK, VIEW, & READ the Attached "LINK" below:

3.37 MODIFICATION GEARING INSTRUCTIONS FOR 2002-2006 TWIN CAMS 

I happen to be "ClassicRider" @ V~TWIN FORUM.

The above THREAD which I have provided a "link" for above will address ways of seperating the Clutch Shell Basket/Ring Gear from the Clutch Hub as well as considerations for whether or not changing the Double Angular Bearing is necessary. 

Hopefully it is helpful to some you!

Regards,

"Classic"