An experienced frame builder had a look at my steel softail and seemed cautiously/respectfully dubious of the design concept. He said it'd make more sense with titanium, but even then, he wasn't convinced ie. the bending / stress at the chain stay/seat stay joint would eventually give way, or the chain stay/bb joint would stress out.
So ... is a softail concept a flawed design or is it simple genius (I'm sold on them from a ride perspective and low maintainence, more interested in the engineering / technical design view)?
As i understand it, steel and ti can both flex a certain mount without any long term failure - this is why they are generally short travel.
That makes sense, but will the flexing cause 'movement stress' where the seat and chain stays are brazed together, and then these ultimately fail?
Nah, I wouldn't worry! Not that much different to things like Yetis or Cannondales with flattened stays designed to flex. Had you cut the bridge out of your seat stays and stuck in a shock I may be worried, but not when it's designed.
njee20 - MemberNah, I wouldn't worry! Not that much different to things like Yetis or Cannondales with flattened stays designed to flex. Had you cut the bridge out of your seat stays and stuck in a shock I may be worried, but not when it's designed.
I imagine its a ritchey or similar - so then it WILL have a shock in there 🙂
madness! the sky is falling!
Yep - it's got a 'shock'
couple of pics - first is steel frame with a v simple spring/elastomer 1" shock, second is ti, with a slightly more sophisticated air 1/5" travel.
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Didn't someone make an aluminium soft tail? Anyway being a frame builder doesn't make you a stress analyst does it.. Hopefully someone has doen their sums and it'll all work out.
Steel:
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Titanium:
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there was also a company that did an alu one (name escapes me), which was less encouraging
Theres also the Scalpel, but this is more a pivotless full sus rather than a softail:
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The new Cannondale Flash is different again - it uses a flexing seatpost (cleverly layered carbon) to provide about 40mm of 'travel'
forgot about the globals!
The Global is a truly lovely ride. The rear 'shock' is pretty active/lively compared to the Dekerf/Moots style which is more of a 'soaking up' gentle action. Wonder if more bounce and liveliness can cause more fatigue/stress?
Not sure on the engineering side of things but surely Castellano deserves a mention?
Saw one years ago and thought thats gonna snap...
Surley they must have tested the frame before selling it right?
Moots YBB is on my "wants" list. I always reckoned it was THE ideal bike for bike-packing. I'd have to get the custom-fitted rack mounts too though
soft tails should have the same sort of bb design as this [img] 
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Mines aluminium (scandium) and I'm a right lard arse and it hasn't broken yet - I have to say I'm not considering it a "life time frame" though.
I Can't afford a ti softtail at the moment but as soon as I can that is what will replace it. I think Lynskey wanted about $4K dollars to build what I wanted !
Its a Salsa Dos niner by the way and for long distance stuff I can't think of a better bike (also bought as a "bike packing" bike - now all i need is the time to go bike packing!)
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Not sure on the engineering side of things but surely Castellano deserves a mention?
Perhaps the most engineered bike ever? Does it qualify as a 'soft-tail'? 5" of rear travel and not a pivot in sight! 8)
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I wonder why Ibis didn't continue that design?
Expensive as **** to make? Castellano still makes them to order (custom), something like USD$6000 I think?? 😯
So if you have a bike with a metal spring in the shock, is that a design fail? Steel has been bent back and forth elastically since it was invented.
Done properly, a softtail is fine. Even in aluminium, you just need to understand the material properties and the stress in your design and together they'll tell you roughly how long it'll last (aircraft wings bend a lot, and they're aluminium) - and it's not like a bike is ridden constantly for 100 years.
It may give way eventually, it may not. But if you have to ride a million miles over rocks to break it, it'll do you and its next owner just fine.
The scalpel is a proven design - flex is in the bonded carbon chainstays though, rather than steel or Ti. Terrific bike, but so XC race orientated that it will always have a limited market.
I can't speak to the engineering myself, but have read that having the flex embedded and localised into an ultra-stiff aluminium frame is the best approach for a softtail that you want to have some sort of predictable rear-sus performance. Just a second-hand opinion from reading frame-designers arguing on MTB review. That Moots posted upthread is a thing of beauty, but it looks the type of bike I'd take out with my wife and kid for a pootle. Wouldn't fancy it at all for more serious stuff.
psychle - are you still pushing that bow-ti around - afraid of getting it dirty ?
I think you should loan it out for others to stroke. 😉
Does it qualify as a 'soft-tail'? 5" of rear travel and not a pivot in sight!
[b]psychle[/b] that is a truely lovely Bow-Ti & I enjoyed reading your deliberations on whether to buy & successive follow on posts. Castellano still makes a soft tail - a Fango with 1.25" rear travel, similar to the long gone Ibis Ripley/Silk Ti. Often contemplated the idea but as you state quite a financial commitment. Anyway, hope you are enjoying that beaut that deserves its place in MTB history.
psychle - are you still pushing that bow-ti around - afraid of getting it dirty ?
Almost completed it's 'rebuild' with some slightly less rare/expensive bits (avid ultimate brakes, fox F80 fork, Crossmax SL rims, middleburn RS7 cranks, Push'd RP23 shock and a lovely 90mm Ti Ibis stem with Titec Ti flat bar)
Should all be complete and ready to ride in time for the STW Leith Hill ride, fingers crossed! Shall post pics once she's back together, promise. 😛
tis black magic I tell thee!
<warm fuzzy moment>
'Sounds great, look forward to seeing 'photos. Bow-Ti s are peerless.
taka - Membersoft tails should have the same sort of bb design as this
Why?
More weight, no added benefits, plus the pivot means no real pedal-feedback, which can mean a bobby ride.
Salsa Dos Niner
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currently $399 [url= http://goldenbikeshop.com/ ]here[/url] - for the 29er/softail curious.