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I've noticed the reappearance of elevated chainstays on rigid/HT MTBs, as well as asymmetric chainstays on FS MTBs.
Can anyone highlight any benefits to e-stays in terms of mud clearance, power transfer?
Surely if you shorten the chainstays with an e-stay to reduce the wheelbase for snappier climbing then you are reducing the clearance for mud build up?
How do the bikes deal with the chainline issue if the e-stay is on the drive side? Are there any benefits to it being there instead of the non-drive side?
TIA
I think it is about fat tyres. With plus size tyres and a reasonably short chainstay, there is very little room between the chanring and the tyre knobs (even with a single ring) through which to thread a chainstay. There would be sideways tyre clearance issues. Bent seat tubes deal with the radial clearance, but that is less of an issue generally.
Ok, but what about forces involved?
I am not aware that anyone thinks there are structural advantages to it. Have you heard of any arguments in favour in modern times (I know high chainstays were a fad many years ago) other than easier packaging?
No need to split a chain Easy to fit belt drive clearance for fat tyres with shorter stays. Always seemed to be flexy bitd.
The only advantage that I can see is that you don't need to engineer in a way to fit a Gates belt drive. This only applies to singlespeeds, of course.
Beaten to it.......
Here is something that was brewed in the shed.
This is now my regular commuter with space for fat slicks and mudguards. Photo shows a 2.3 29er tyre with 395mm chainstays.
As you can see, the main advantage is packaging - fat tyre is right alongside and close to the chainring for good chainline and no mud issues. With skinny tyres clearance is HUGE - it was impossible to make it clog when my Mrs used it for CX racing.....
Not noticeably flexy, but one day I'm sure it WILL break (cantilever under lots of bending fatigue loads). I suspect it wouldn't meet the Gates belt drive frame stiffness requirement.
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Cheers Mick.R unsurprisingly your works have popped up whilst I've been doing searches. I'm looking at an e-stay frame for CX racing. Even with the large clearances on the Canyon frame and fork, clogging is still an issue.
I've not considered the curved seat tube yet, instead was looking at normal geometry but with a single stay elevated to provide, or rather remove, the normal catch point at the bottom bracket junction.
With the drawings so far, if I went down to 395mm with the chainstays, the wheelbase would be sub-1000mm. Maybe a bit too whippy.
Hi
So far I've built our CX bikes with a longer front & shorter stem or slacker HA to avoid toe overlap, so that restores handling balance of a short back end. Saying that, I've also been building with a straight seat tube and just sticking with stays around 415mm (laziness rather than curved tube being a major problem).
Also look at Julie Racing Design 29ers etc for straight seat tubes that join ahead of the BB shell to give more tyre clearance (love his work).
My new CX frame is finished and just being filed / tidied. This is a similar no-clog design (I hope). Running a Pace carbon 29er fork for huge front mud clearance. CAD image below.
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Not noticeably flexy, but one day I'm sure it WILL break (cantilever under lots of bending fatigue loads). I suspect it wouldn't meet the Gates belt drive frame stiffness requirement.
I'm not sure it's that bad, as you have still got triangulation from the seat stays, plus you've connected it to the seat tube and down tube, plus you've done a pretty decent job with the (brazed?) fillet joints.
I mean, everything will break one day, but as far as bike frames go, I've seen much worse.
Thanks mick.r. I'd not seen the JRD work. As you say, just stunning. Interesting you are using the pace fork; I'd been looking at 27.5 MTB forks for their clearance.
I'd considered emulating the slacker HA for a longer wheelbase but had got caught up in the rear so far. Interesting use of twin top tube in your design; any rationale behind it?
That frame is already 6 years old, so I guess I mean it will break before a regular rear triangle 🙂
Flex is only noticeable if you swap straight from a big tubed aluminium frame.
If building with a horizontal stay, mine is about as low as you can run without chain rattling at the rear. You could go lower if it ran parallel to the chainline. Down tubes with long butted sections for extra stay joining were hard to find. Columbus does a 35mm one (in regular and long 750mm lengths).
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This is it in no clog CX format.
http://www.whiteflyerphotography.com/events/2014%20Events/Stadt%20Moers%20Cyclo-Cross/Women-Vet/slides/SMCX14-333.html