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Message started by Armen on 11/26/19 at 06:02:33

Title: Belt tension with longer shocks
Post by Armen on 11/26/19 at 06:02:33

In order to achieve 'Genre Reassignment Surgery' (cruiser to cafe racer) I had an 18" rear wheel built, and am using longer shocks.
Figured the longer shocks would change the amount of belt slack the bike wanted.
So, I removed the shocks and moved the wheel/swingarm up and down to see where the belt gets tightest. Of course, it's when the front and rear pulleys and the swingarm pivot are in one line. Set the belt tension to almost zero at that point.
Put the shocks back on to see how much slack that translated to. The belt now has one inch/1"/25mm when the shocks are at full extension.
Wondering if that will be an issue?
Only solution I see is to use some sort of spring loaded roller on the underside of the belt. I think Ryca had some sort of thingie like that.
Anyone with long shocks and a belt have any grief? How much slack are you running?
thanks,
-Armen

Title: Re: Belt tension with longer shocks
Post by Ruttly on 11/26/19 at 10:00:11

With rider in full gear at total weight,sitting on the bike uses up a good portion of the slack. I did a chain conversion on the tracker and couldn't live with the slack in the chain and fabbed up a chain tensioner. Sometimes on a twistie road that nastie hairpin turn pops up a little soon and find myself coming in hot and all over both brakes and some minor ripples on road surface I get some rear wheel hop. That weight transfer doesn't help and chain was slapping around under braking, the only wise choice was a chain tensioner.

Title: Re: Belt tension with longer shocks
Post by Ruttly on 11/26/19 at 11:09:28

If you support bike with rear wheel not touching the ground , remove shocks , remove spring from one shock & reinstall. Now you can raise swing arm to where shock is bottomed. Now you have max tension setting and exactly how much slack can be made by bottoming shock. Can you live with the slack ? How much sag at rear shocks with max weight on bike, that's your loaded sag. Getting to a point where you can find a happy medium of adjustment without using a tensioner. The belt has a little give/stretch to it unlike a chain. Belt might be a tad tight unloaded but as soon as you sit on the bike it is no longer tight. Might get a tad tight under some conditions like hard braking or getting airborne ( in my world airborne is fun ). As your swing arm is compressed you get more slack until shock bottoms. Kinda how I found my sweet spot for chain adjustment and where tensioner is needed the most to keep it chain tight. Hope this helps , pretty sure you know more about this than I do.

Title: Re: Belt tension with longer shocks
Post by Gary_in_NJ on 11/26/19 at 11:25:54

I have a lot of experience doing this very same testing...but all with a chain...so I don't know how my experience would help.

I think a chain is more forgiving of slack than a belt. I run about 1.25" of chain slack and all is good.

Title: Re: Belt tension with longer shocks
Post by Ruttly on 11/26/19 at 14:26:05

Chain or belt it the same process finding where it gets tight and where it is slack and dialing it all in. Not too tight or too loose. The reason I made a tensioner is I built the tracker to take daily abuse ,I wanted it to be as versatile as a dual purpose. It eats up twisties,loves a fast dirt fire road & works ok on trails , even cruises at 70 mph & even does TT size jumps with ease. Like I always say "Trackers are for raising hell on two wheels"
Absolutely without a doubt one fun bike to ride !

Title: Re: Belt tension with longer shocks
Post by Dave on 11/26/19 at 17:26:27

I don't know how much travel your shocks have - but here is how I decided to set my belt tension.

I made a strut out of a piece of Oak that was the same length as my shocks when fully compressed, and I put those struts on and set my belt tension to being pretty tight at that point....which will only occur when the shocks are bottomed out. I then put the shocks back on and as expected, the belt was much looser than the "twist 90 degrees with your fingers standard" would make the belt.....I suppose it has an inch of travel and maybe more. When I sit on the bike it tightens up a bit.

I have 12,000 miles on the bike using that method, and I have not had any belt trouble yet.

Title: Re: Belt tension with longer shocks
Post by Armen on 11/26/19 at 18:06:52

Thanks for all the responses. I believe I have the correct info for how much slack I need to run, about 1" with the s/a extended. The question is, will that much slack cause any grief?

Title: Re: Belt tension with longer shocks
Post by Dave on 11/27/19 at 04:48:06

33080512030F141209010C13600 wrote:

I have 12,000 miles on the bike using that method, and I have not had any belt trouble yet.

As I stated earlier......I have not had any problems that I am aware of.

The only time I had any concern was when I was trying your lightened flywheel, and doing some "drag race" 0-60mph runs to get times. I am not a fan of doing full throttle from standing starts, as I believe that is the most stress you can put on the belt drive. I didn't shear off any teeth from the belt - but I really don't like treating my bike in that way.