Drive Belt Tension Changes When Hot

[Coyote]

90* ? Maybe if your name is Dwayne Johnson. Most of us struggle at 45* LOL.
Ron

[Ohio HD]

had the same experience when adjusting belts, i always adjusted to the loose end of the spec. don't know where i heard or seen it but somewhere i heard that a rule of thumb on the belt is to grab it mid point with your thumb and pointer finger and twist it from vertical to horizontal. it should just rotate 90 degrees with a good amount of effort.

90* ? Maybe if your name is Dwayne Johnson. Most of us struggle at 45* LOL.
Ron

naahhh, it's easy when the belt is way too loose......     

[Coyote]

had the same experience when adjusting belts, i always adjusted to the loose end of the spec. don't know where i heard or seen it but somewhere i heard that a rule of thumb on the belt is to grab it mid point with your thumb and pointer finger and twist it from vertical to horizontal. it should just rotate 90 degrees with a good amount of effort.

90* ? Maybe if your name is Dwayne Johnson. Most of us struggle at 45* LOL.
Ron

naahhh, it's easy when the belt is way too loose......     

Like off the bike completely? lol

[Ohio HD]

had the same experience when adjusting belts, i always adjusted to the loose end of the spec. don't know where i heard or seen it but somewhere i heard that a rule of thumb on the belt is to grab it mid point with your thumb and pointer finger and twist it from vertical to horizontal. it should just rotate 90 degrees with a good amount of effort.

90* ? Maybe if your name is Dwayne Johnson. Most of us struggle at 45* LOL.
Ron

naahhh, it's easy when the belt is way too loose......     

Like off the bike completely? lol

yep!   

[kd]

And for that reason I do the 45 degree test.

[mkd]

YEAH!  MEMORY ISN'T THAT GOOD! 45 is good, 90 is too loose! i'm staying home!

[Xyzzy]

One reason the belt so tight is to eliminate harmonic vibrations in the belt. If you get them it feels like the whole engine is self-destructing. Also, there is less drivetrain slack with a tight belt. HD has been using belts for a long time and you rarely hear of a belt failure and I bet the majority of them are set the way they were from the factory.

[Xyzzy]

Update: I finally bought the HD springy tool (40006-85) to measure belt tension. Using the tool the belt is much tighter than I ever expected. I have no idea how the output shaft bearings can deal with that much tension. But the bike rides smooth and I'm willing to experiment so we'll see what happens. I'm pretty sure my Sportster has its tightest belt position with the shocks fully extended. (The swingarm arc is "above" the imaginary line bisecting the axle, swingarm pivot and output shaft.) Maybe that makes a difference. Anyways, the tool is pretty easy to use and it didn't cost a bunch. YMMV!

[Coyote]

Every one I've worked on was set too loose.

[Norton Commando]

The sprocket diameters grow / expand with heat also.

[kd]

My guess has been a tough 45 also.

[Hossamania]

My guess has been a tough 45 also.

Xyzzy, since setting your belt with the tool, how far can you twist it by hand?
I have used the tough 45° degree method for years, just wondering how close I am.

[Rockout Rocker Products]

Back in '94 my Evo softail developed a squeaking noise on the way home from Sturgis. Couldn't find the source, figured I'd deal with it when I got home. Few days after my return I went to cure the noise but it was gone. 

Oh, that was the year my wife flew to Rapid City to meet me there, & ride home with me.

[Fugawee]

At least it was only a squeak, and not a whine.

[Appowner]

Curiously my other passion, home built aircraft is having a belt discussion on their site right now.  Though they have an advantage since there's no swingarm to change the length on them.  But it strikes me that in general they use more and/or wider belts to drive a propeller at around 2500 rpm than we use for our bikes.  Yet the horse power of both vehicles is in the same general range, up to and including 100 plus hp.  Hpwever from around 100hp and up the belts are dropped in favor of gear reduction.  Sort of like bikes going with shaft drive.

That said, is it safe to say a belt tolerates/requires a tighter setting than a chain?  IOW a chain will better handle being a bit loose.  To a point of course.  But my thought is with the concern expressed for wear on bearings, wheel alignment and such due to the tightness of a belt, wouldn't going back to a chain be better in such a case?  Granted, there are advantages to a belt but in the long run but is it really that much better?  Especially should alignment and bearing issues arise from the belt. 

I for one never minded doing the maint and cleaning involved with a chain.  And intend to switch to one should my belt ever wear out.  But then I also recall when a bike was a very simple and basic mode of transportation.

[smoserx1]

But my thought is with the concern expressed for wear on bearings, wheel alignment and such due to the tightness of a belt, wouldn't going back to a chain be better in such a case?

I have never heard of that being a problem if the belt is properly adjusted.  When my bike was fairly new I marked each axle adjuster nut so I could loosen them for ease of wheel removal, etc. and always put them back the same, thus maintaining tension and alignment.  The belt exhibits a large difference in perceived tension from cold to hot.

[Hossamania]

When adjusted properly and driven normally, even a bit abusively, on a mostly stock motor, a belt and all associated rotating parts will last 100,000 miles. No chain will do that.
The choice of changing to a chain are due to other goals: off road or much dirt road riding, excessive horsepower usually associated with racing, easy gear changes. Longevity is not the normal reason to switch to chain.

[itsafatboy]

Question can someone tell me what the drive belt deflection is on a 2006 softail , the 200mm tire with the skinny drive belt ,  I have this on my 01 fatboy but not sure on how tight to make belt , I have it set at 3/8" 10 pounds pressure on side stand but man it feels tight

Thanks

[louloupa]

On my RK, I have longer shocks than the stock ones. So, to adjust the belt tension, I lift the motorcycle, I unplug the shocks. I lift the wheel to reach the point of maximum tension. It is in this position that I adjust the tension of the belt ( with the HD specification ).As I turn the wheel, I also look for the tightest point.

[JDhog211]

I use 45degree twist deflection and find that a perfect method.
Keep using that HD tool and you’re going to go through bearings.
Trust me