It would seem a logical conclusion that, Yes the belts do stretch and wear. That's why its a service item to test and adjust belt tension at regular intervals. That's why there is an adjustment system as they stretch over time the wheel needs to be moved back as need to bring tension back into spec, just like chains....kind of hoping now you don't go into some long dissertation on how belts and chains are different....its just a generalization for example.

 

did just a bit of research via Google, and the question of whether a motorcycle final drive belt stretches with odometer miles is still unanswered!

But, I found this article on a helicopter maintenance site, which is not where you would normally look, but it turns out that Gates makes drive belts for both helicopters and Harley-Davidsons!

See:

http://www.epi-eng.com/rotorway_heli...elt_issues.htm

This article is very informative, especially on the issue of pre-tension, why it is vitally important, and how it differs considerably based upon the expected peak loads, average loads, and the expected duration of each.

But, even this rather informative article does not really answer the question of whether a drive belt stretches with odometer miles. And knowing that is pretty important in order to know if a 70T pulley will actually fit onto a 32T front and stock belt length.

Yes, there is certainly RUBBER wear on a belt, which requires some compensatory adjustments, but the inner longitudinal belts of an HD drive belt are KEVLAR, which I have alway thought, perhaps correctly or incorrectly, does NOT stretch. It can only BREAK when a point load is created via a pebble or other hard small object getting kicked up and trapped between the pulley and the belt.

Oh, and here is another quote froma different article on belt drives:

"Because the swingarm and drive pulleys are at different distances from the rear axle on motorcycles, producing unequal radii when the bike’s suspension deflects, belts and chains both need some play to accommodate the variation in length.".

So, now, I am totally confused about how much "give" you need in a belt drive, and how much that changes as the miles accumulate . . .

Jim G

 

Belts do stretch but not like you'd think with a chain- it's more like initial stretch under applied load. We're talking about a bit over 1/16" and that's it. The belt will never stretch more than that. Unlike a chain which continues to stretch until replacement time. The dynamics and adjustment of a belt drive system vs a chain drive system are vastly different, and should generally never be compared to each other in mechanical terms.

Here's some interesting facts- Anyone can call Gates and talk to a tech, and get similar data:

In the first few hours of operation under load (on a Harley, Helicopter, whatever) the new belt takes a small permanent stretch which has the effect of reducing the preload on the pulleys. So the preload values from factory for a new belt are set higher than for a used belt, in order that the correct preload remains after the new belt stretches.

The belt preload (specific amount of belt deflection at 10lbs) Harley specifies is recommended by Gates since they developed the belt specially for HD (The tooth and pulley profiles Harley uses were also developed by Gates to match the belt). This adjustment is a preload value based on the typical "cruise load" HP produced by the motor, since that is the predominant HP loading the belt sees most of the time. It's pretty low, less than 30hp IIRC.

While the designed amount of HD belt preload is mainly for low-hp cruising, it is also able to tolerate occasional WOT (high HP to belt) without needing to have the belt preload changed for high-HP operation. This is why many performance shops recommend running the belt tighter on high-HP builds where the main goal is all out speed.

So as this relates to the 70T pulley install on the Breakout, that extra 1/16"+ of permanent stretch on the belt after a few hours of riding a new bike could make the difference between fitting and not fitting the 70t with the 32 stock front pulley. Either you can get your axle through the swingarm slot or you can't. If you can get it through, then adjust preload tension and done.

But also recall I didn't think the 70t would fit with the stock 32T front pulley because my math said I needed 15/16" of room on the rear axle slot, and as a member already demonstrated, only 7/8" is needed.

 

Changing directions for a moment...


What's my best option for luggage? I plan on getting the rack on the back of the sissy bar, and the one on my Sporty actually does pretty well for how small it is if I use the bungee efficiently. Plan on taking a few weekend trips with the lady this year, and I'll be fine with a couple shirts and an extra pair of jeans, but she... yeah that may be an issue with a single bag on a sissy bar rack. What are my options?

 

Staying at a Hotel ?

Mail a box of clothing changes to the (reserved) Hotel ahead of time and have the Hotel mail the "dirty stuff" box back to your home as you check out refreshed. One of those "If it fits, it ships" boxes is great for doing this.

 

^ That's pretty smart, thanks.


Mk23's are nice as hell, I carry another one of their pistols for work. Just felt like saying that ha

 

Glad to help bro, its a borrowed idea though, . MK23 is too big for any practical use but HK makes excellent pistols for sure. I had a USP tactical but sold it (safe getting full). I'm a 1911 fanboy but would own USP's all day long !

 

Well guys I had the itch and went to the dealer over the weekend and ended up trading in the BO. So I have some bolt-on parts I will be removing and putting up for sale here on the forums. Most notably I have the tall sissy bar from a fat boy stretched to fit the BO fender. It was a nice looking yet functional set up for the BO. Look in the FS section pretty soon for everything.

 

zz - good luck with your new scoot- it's all about enjoying what you ride.

So I just picked up a clean used stock 46mm TB on ebay- $40 shipped. going to have that bored / ported to 50 or 51mm for $100 then slap in a set of larger 4.9 SE injectors.

 

Evening All,

Also if anyone is interested I just upgraded my 103 to the stage IV pro race kit meaning I have all the stock parts, TB etc and the SE edge cut black cone heavy breather from the stage I kit for sale like cheap. Also I just order a Thunderbike chin fairing for my breakout and lo and behold...they shipped me 2 of them. So if anyone is interested in that with mounting hardware also let me know! Oh it's for ABS models.

Tex