Bonneville America Forums Forums Technical Forums General Tech Belt Drive Ratio Math

Okay, I searched around and I understand that the QPD Belt Drive from Brent is a 2.458:1 ratio (59/24) and it's a little smaller than the stock Speedmaster.

My pulleys are trashed. The teeth have been chewed to crap by, I guess, road debris, gravel and such. I'm 99% sure this is where my squeak comes from. They look a lot like this (picture from the website below, not my actual pulley):



I'm talking to the owner of Supermax Belt Drives (http://www.supermax.net/) about fixing the pulleys with their poly overlays but they don't have a 59 tooth overlay. the closest they have is 58 tooth. Since they machine off the teeth and press on the overlay, it can probably still be done, but will this have any kind of significant effect on the final drive ratio? I guess that changes it from 2.458:1 to 2.416:1. I'd actually prefer to go higher rather than lower as I do more long distance travel these days. Might ask him if he can go up to 61 tooth.

What do y'all think? I'm afraid this might be pretty darned expensive to do but by all accounts, and not just from the Supermax website, it will fix it for life. I'm trying to decide if I'm "pot committed" or if I should go back to chain.

FJ, Does the cush drive last any longer with the belt on ? Mine is ducked after only 10K miles, apparently thats normal. I'm not sure of the specifics of the liners for your pulleys but they will react the same way in the long run. I have been looking at the belt drive conversion but at that cost I'm happy to stay with chain, also too, so that I can easily adjust the ratio to settle with one that suits my riding... Would it be so bad to refit chain and auto oiler, allowing you to do the same ? If you're pretty sure the squeaking is coming from the belt drive try a very light oiling in GT85 (PTFE based spray oil), we did last year to an old kwak and it's still good...

My cush drive was due for replacement a while ago. Last year I shimmed it with small squares of inner-tube, not because I'm cheap but because I was tight on time. I've got a new TBS cush drive waiting for it now.

I've tried all kinds of things on the belt to quiet it. They never lasted very long.

That's why I wondered if I'm "pot committed." I've already paid for the belt drive and a couple spare belts. It's probably worth spending a few more hundred to be done with it for the life of the bike.

If your already committed to the belts, and happy with it, then I'd say have a go. Try the liners and see if the poly lasts any longer against the wear.. I suppose at the end of the day it all comes down to long term calculations... What's cheaper over the next 5 years or so. For you it certainly sounds like belt.

wish we had another belt option, that would make problems like this much easier to deal with

Hey John

You only mention the driven pulley.

What is the condition of your drive pulley?

If you want to up the ratio, then get the drive pulley poly coated on a smaller teeth count than present.

I installed this belt drive system and must now check the wear rate, thanks for the tip.

I was thinking that too, if you change the rear, can you change the front to compensate?

In my emails with the owner he said, "I should actually see your pulley to determine if indeed I could over-lay it or have to make a new one."

The portion I bolded is very, very interesting. But I can all but guaranty that it will not be cheaper than the Newspeedmaster/QPD kit. They've pulled the prices off the Supermax website, but I seem to recall from last year that just over-laying a stock pulley costs somewhere around $400.

Just got off the phone with Phil from Supermax. Cool dude. Gave out a flurry of information. This guy's mind operates at a million miles an hour. Aaaaaaanyway...

A stock harley pulley costs $460 to overlay. Building a new pulley from scratch is $600, so it would probably be worth it to just start from scratch. Keep in mind that these things supposedly last virtually forever (and I don't plan to ever sell this bike). He said it would probably be an extra $100 for machining because he's not set up to deal with my pulley but he'd know more once he saw it. So I have to pull one of the side flanges and take some pictures before he gives me a real estimate.

If it was the narrower 8mm setup that came on some Japanese bikes he wouldn't deal with it at all. He says he doesn't even know why people produce pulleys in aluminum anymore, the teeth just don't hold up. And here I was worried about BELT life when I bought this kit. Turns out the pulley wears out faster.

Also I told him about my first belt delaminating and he thinks it was a rubber belt, not a poly (?) belt, since it had a smooth back, not a serrated back like the current one I'm running from Harley. He said the rubber belts fall apart, too. He was amazed that Newspeedmaster/QPD sells the kit so cheap (!). I told him that most Triumph riders are pretty "frugal." He said he still has an old Triumph, I think he said a '52, and he modified the output shaft to take Harley components so he could run a belt drive that way. Then he said the Triumph was too slow for him so he has a stroked out shovelhead.

Oh, we didn't even talk about the front pulley yet.

How many miles on your pulleys?
Also, do you think the delamination of the first belt was due to the tighter radius of the QPD front compared to other belt drives?

I've got at least 25-30k on my belt drive kit. I think the first belt went somewhere between 6-8k. Can't comment on the radius thing except to say that it makes it a real PITA to install.

That's just great,
Now I gotta do a close up inspection of my QPD.

Don't panic people. It could just be me. (but you should definitely keep an eye on it, as you should on anything consumable on your bike, tires, brakes, etc...)

I'm not panicing as much as cabin(houseboat)fevering.
My bike has been in the garage since November.
The longest it's set since I got it in '03.
Got 9 inches of snow on Monday, now it's really cold.
Come on Spring!

Just a bump. I emailed Brent and most of the belt drive kit price is tied up in that rear pulley. I still haven't decided if I'm going back to chain or if I'm going to send the pulley to Supermax for a new overlay. I might put my stock chain back on this year (it's only got about 8k miles on it) and get the pulley done later.

Hrm.

Man, aren't those belt drives wonderful!

No, not the QPD belt drive. But on Saturday I saw a HD rear pulley with 80,000 miles on it and it practically looked new. I don't know if it was steel but I don't think so. Maybe it was a harder alloy.

Brent suggested I talk to Ozzie but he's a d!ck so that's not going to work for me.

The pulley but not the belt and when they break along the road you are stuck. Plus have to take half the bike apart for a belt but not to change a chain. plus you can fix a chain along the road in a couple minutes and be on your way for the rest of the day. Chains tend not to get bad damage from riding on rocks or gravel but a get a little of that between the pulley and belt and same can't be said. I can go on, as you should already know I don't like belt drives. I think you give up too much for the sake of a little smoother operation or quieter operation provided the belt doesn't squeek.

Look, jerky, I know the pros and cons of each, but this isn't the thread. The pros of the belt drive let me down.

Well, I made my decision. I ordered up a ScottOiler system today and will be going back to chain. I should be able to get another 10-15k out of my original chain and sprockets. Anyone want to buy a busted-****** set of belt drive sprockets? I'm sure I'll be able to find someone to buy that unused Predator belt.

Sure hope this works. My QPD rear sprocket sharpened up and sliced 1/3rd of the teeth off the belt(3000 miles), leaving me stranded in the outback of Oz for three days while I organized a chain and sprockets to be flown to me. It took two years for QPD to replace them (warrenty). I then hard anodised the rear sprocket. Still rebuilding the bike at the moment, (watch this space), so don't know if this is a sucess yet

I put my chain and sprockets back on last weekend. I might still have supermax fix my rear pulley but it won't be soon.

On another note, the front belt pulley is steel and looks much better than the rear.