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Is anyone aware of any full-suspension frame designs that don't suffer from chain growth when the suspension is compressed? I had a good time last year on my Scott Spark converted to SS, but it does seem like the Yess tensioner puts a pretty lot of drag on the drivetrain, and it seems to be the only good tensioner for full suspension.

Also, I assume a short-cage derailler would have plenty of movement to allow for the chain growth, so I suppose that would be the next best alternative. I don't really want to give up rear suspension.
 

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Nater is exactly right. I believe the Kona model was an A? Maybe you could look in the archives on Kona's web site. I last looked at that frame about 3 years ago?

But just get the Milk Money. That would be so sweet. Do a search for it in the 29er forum for more details...
 

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I saw a Titus Racer X that was converted to SS. Heck, I have even seen 29 inch Asylums that were SS.
 

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Yep, Kona had two vintages of "A" that had a concentric BB pivot and sliding dropouts. The 2003-2005 and the 2006 which was beefier.

The Kona Bass also had a concentric BB pivot and sliding dropouts but was a pretty hefty frame for dual slalom/DJ use...
 

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ecoast said:
Most URT-- the relationship changes to some extent.
That is not correct. The whole point of a URT (Unified rear triangle) bike is that the drivetrain/chainstays/seatstays are all one piece. That triangle is then mounted to a pivot on the main frame. Remember the Klein Mantra? The below bike is not mine, but I used to ride the same frame. This design will certainly work for a SS, but do you actually want to ride a URT these days?
 

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from wikipedia:

Unified Rear Triangle
The "Unified Rear Triangle" or "URT" for short, keeps the bottom bracket and rear axle directly connected at all times. The pivot is placed between the rear triangle and the front triangle so that the rear axle and bottom bracket move as one piece, and the saddle and handlebars move as another piece. This simple design uses only one pivot, which keeps down the number of moving parts. It can be easily modified into a single-speed, and has the benefit of zero chain growth and consistent front shifting. On the other hand, when the URT rider shifts any weight from the seat to the pedals, he or she is essentially standing on the swingarm, resulting in a massive increase in unsprung weight, and as a result the suspension tends to stop working. Because of this effect, along with persistent suspension bob and a constantly changing saddle-to-pedal distance, the URT design has fallen out of favor in recent years.
 

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ecoast, your wikipedia definition proved bikeny's point.

Also, it's not possible to have a VPP with an EBB-concentric pivot. The foundation of virtual pivot theory is to move the pivot to a point in space in front of the bike.

--Sparty
 

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ecoast said:
from wikipedia:

Unified Rear Triangle
The "Unified Rear Triangle" or "URT" for short, keeps the bottom bracket and rear axle directly connected at all times. The pivot is placed between the rear triangle and the front triangle so that the rear axle and bottom bracket move as one piece, and the saddle and handlebars move as another piece. This simple design uses only one pivot, which keeps down the number of moving parts. It can be easily modified into a single-speed, and has the benefit of zero chain growth and consistent front shifting. On the other hand, when the URT rider shifts any weight from the seat to the pedals, he or she is essentially standing on the swingarm, resulting in a massive increase in unsprung weight, and as a result the suspension tends to stop working. Because of this effect, along with persistent suspension bob and a constantly changing saddle-to-pedal distance, the URT design has fallen out of favor in recent years.
That definition is just what I was trying to explain.

Actually, this part is interesting: "On the other hand, when the URT rider shifts any weight from the seat to the pedals, he or she is essentially standing on the swingarm, resulting in a massive increase in unsprung weight, and as a result the suspension tends to stop working"

That sounds like a good thing on a SS. When you stand up, the suspension stiffens, which is just what you want on a SS to hammer up the hills. The Klein Mantra was certainly plush when seated, with 6" or 7" of travel, and to be honest, I never noticed the saddle to BB distance change. Also, not sure if they were all the same, but my Mantra frame had those funky rear facing dropouts that just might work to tension the chain. Damn, I knew I should have kept that frame! The only negative I noticed with the bike was brake jack, which was a little scary going down the steeps!

If you are interested in a Mantra, check Ebay, as they come up all the time.

Mark
 

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Nater said:
Designs like the Haro Sonix, GT i-Drive, and the Maverick Mono-link work to reduce chain growth, but they don't totally eliminate it.
..well,it is eliminated on the haro.

the center of the bb is the pivot point.

because there is no pivot between the bottom bracket and rear axle, there is no pedal feedback, pedal bob or chain stretch. The rear swingarm is the same structure you would find on a hardtail, so as you climb, pedal energy goes into forward motion instead of being absorbed by bob and frame jack...
 

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The most recent Kona full suspension single speed compatible frame was the Cowan DS. Looks like they have discontinued it again, but there are still some out there:

http://www.cambriabike.com/shopexd.asp?id=50111

Also, besides the Milk Money, there are several 26" wheeled Lenz frames that have concentric pivots that would allow the use of an eccentric rear hub to make them single speed. Since Lenz is a very tiny company, they (he?) might make one with sliding dropouts on request.
 
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