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caninus xerophilous
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I am considering converting my Quasi-moto into an FS-SS. Anyone riding one or have experience with such?

Any thoughts or advice would be appreciated.
 

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Now with flavor!!
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Chain growth.

You will need a spring loaded tensioner to do this since the virtual pivot is not concentric to the bottom bracket. Not the best bike to use for this purpose. Regardless of your gearing you'll esentially have to use something akin to a derailleur. You can do it but you lose the nice simplicity and quiet ride.

BB concentric frames are the only ones that can leave you chainslap free.

Kona Unit, Cove G-spot, Lenz sport and Rotec frames are the ones to check out.
 

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Orange UFO

Yes I run the above bike with a single speed set up it has a Unified rear Triangle which has the suspension pivot in front of the bottom bracket
the only draw back is that with vertical rear drop's you have to play with cog sizes to get the chain tight enough not to come off, but do get approx 350-500 mile's from a chain before chain stretch make's it throw the chain on the rough stuff, bare in mind it has to appear to be too tight before initial ride with a new chain
cheers Jacobite
 

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caninus xerophilous
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Discussion Starter · #5 ·
Frame choice isn't an option.

kidwoo said:
Chain growth.

You will need a spring loaded tensioner to do this since the virtual pivot is not concentric to the bottom bracket. Not the best bike to use for this purpose. Regardless of your gearing you'll esentially have to use something akin to a derailleur. You can do it but you lose the nice simplicity and quiet ride.

BB concentric frames are the only ones that can leave you chainslap free.

Kona Unit, Cove G-spot, Lenz sport and Rotec frames are the ones to check out.
I understand some of the limitiations of the 4 bar, however I have only that frame to play with.

I usually ride the entire ride in 32 X 30/28 and have singlespeeded once when I knocked off my derailleur which destroyed my chain and cassette. With that gearing in mind how would that transfer to an SS drivetrain?
 

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Mtn Biker Machinist
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the low down

SunDog said:
I understand some of the limitiations of the 4 bar, however I have only that frame to play with.

I usually ride the entire ride in 32 X 30/28 and have singlespeeded once when I knocked off my derailleur which destroyed my chain and cassette. With that gearing in mind how would that transfer to an SS drivetrain?
Take off big and little rings, gather a bunch of cassette spacers, one cog for the rear (from an old cassette) and an old deraileur or paul melvin tensioner. The 32X28 combo seems really spinny unless you are planning on climbing Everest, but gearing is your call. Compress the rear end all the way (let all the air out to simulate bottoming out the shock), and make the chain just long enough to wrap around cog, through the deraileur, and around the front ring. Assemble chain and use high/low screws to adjust deraileur until the chainline is right on. Fill the shock back up, and test it. Enjoy! Post pics and ride report when you finish.
 

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Having tried the Paul Melvin 5-6 years ago I discovered that the spring tension was not enough to prevent enough chain slap to allow the chain to jump several teeth on the rough stuff, so I would suggest useing an old derellier as it will cope with more chain slap from the suspension movement, just adjust it so that it wraps around the rear cog as much as possible ie to at least 6.00 pm position
cheers Jacobite
 

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I'm sticky
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SunDog said:
I am considering converting my Quasi-moto into an FS-SS. Anyone riding one or have experience with such?

Any thoughts or advice would be appreciated.
Go for it. 1 cog frog's advice is pretty spot on. Compress the suspension, size the chain so it is as small as it can be when the susp. is fully compressed, get the chainline straight, and set the limit screws to line the derailleur up with the cog.

I've been riding my FSSS for about 9 months - no problems at all.

Check out this thread for more info:

http://forums.mtbr.com/showthread.php?t=63740

(there might be more if you look up all the threads I've posted to)

Good luck, and ask questions if you get stuck.
 

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What day are we riding?
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I currently ride a Lenzsport. Also have two Schwinn Homegrown FS bikes that are URT frames and are reasonably light.

If you give up on a tensioner you can always sell your frame and excess parts and buy a different one...
 

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frankenbike said:
There is a member named "itsdoable" that has converted a couple URT bikes to SS FS rides. Do a search for his name or look in the photo gallery.
That would be me - I'm a fan of tensionerLESS setups, so that leaves you with URT's, Softtails and concentric swingarms. I've often used a DIY eccentric axle setup, the links on the previous posts show some of the conversions. I have not tried a FS-fixie yet, but I'm sure I'll get around to it.

However, to your original question: Qasi-moto will make a fine FS-SS, but you will have to use a chain tensioner as that bike has a few mm of chain growth through it's suspension cycle. A singulator type device will probably not provide enough range (you might get it to work with a carefull selection of cog & chainring), so you should use a 2-pulley type (Pauls Melvin or Rohloff) or any old derailleur - preferably a short cage. Use as short a chain length as you can get away with (long enough for the suspension to bottom out).

Cheers,

Tom
 

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Now with flavor!!
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singletrack said:
Lance Canfield ran SS in the Red Bull. Uses it for DH racing too. The idler pulley does much to counter chaingrowth.
That's awesome. Since that bike has a pretty significant rearward axle path, if you can do it with a canfield, you can pretty much do it with anything!! :p

Now I'm curious about my bike. I broke a chain at northstar one day and rode an entire run without it. Sooo nice and quiet.

Thanks. You've inspired me. ;)

Do you know what kind of tensioner that is?
 

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kidwoo said:
That's awesome. Since that bike has a pretty significant rearward axle path, if you can do it with a canfield, you can pretty much do it with anything!!
Well, again the idler pulley keeps chaingrowth and pedal feedback to a minimum, or as little as you can get on a loooong travel bike.

I'm purdy sure that the tensioner in that pic is homebrew cnc'd, and uses a MRP roller instead of a a pulley gear.
 

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Now with flavor!!
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singletrack said:
Well, again the idler pulley keeps chaingrowth and pedal feedback to a minimum, or as little as you can get on a loooong travel bike.

I'm purdy sure that the tensioner in that pic is homebrew cnc'd, and uses a MRP roller instead of a a pulley gear.
That's very true. I guess that pulley puts the drive center pretty close to what an instant center or virtual pivot location.

Very cool indeed.
 

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Canfield Bikes
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kidwoo said:
That's very true. I guess that pulley puts the drive center pretty close to what an instant center or virtual pivot location.

Very cool indeed.
Yea the upper pulley wheel removes almost all of the chain stretch. That bike pictured is JD's bike, the machinest at White Brothers so he made his own tensioer. Notice the BMX chain and Profile 28 tooth Imperial, BLING!! I run a 105 road mech and have had the same one on my bike for close to two years with no chain problems. Or adjustments, just had to replace the cable after I smashed it in half.
 

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1 cog frog said:
Take off big and little rings, gather a bunch of cassette spacers, one cog for the rear (from an old cassette) and an old deraileur or paul melvin tensioner. The 32X28 combo seems really spinny unless you are planning on climbing Everest, but gearing is your call. Compress the rear end all the way (let all the air out to simulate bottoming out the shock), and make the chain just long enough to wrap around cog, through the deraileur, and around the front ring. Assemble chain and use high/low screws to adjust deraileur until the chainline is right on. Fill the shock back up, and test it. Enjoy! Post pics and ride report when you finish.
This is spot-on advice. I had a pal from UK that SSed a ProFlex 856. Basically a 3" rear travel frame that is NOT even close to URT. I rode one for a coupla years and can say that there is lots of chain growth and pedal bob. Don't remember his handle here, but I saw some pics of his conversion...XT derailleur sans lower pulley. I really didn't care for the sans lower pulley issue, but he had zero issues with the setup. As long as the chain is long enough to allow for a full compression of the suspension, AND you can keep the chain tensioned and on the cog/ring, there should be no probs. In addition, you can add a DISCO set to fully ensure against throwing the chain. Also, use a Shimano DX cog (or another SS specific cog) to thwart tossing the chain...be anal about your chainline as well!
 
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