# IsoSpeed too bouncy



## jeff400650 (Mar 29, 2014)

I have a 2013 Domane 5.2 that I really love to ride. It is a 62cm and I am 6'3", 200 lbs.

I bought it new 1.5 years ago and have put 4000 miles on it.

It just has one problem that I'm wondering if anyone else has noticed. It has become apparent to me as I get fitter and ride more, that the flexing seat tube is occilating with my pedaling when my cadence gets faster... at maybe 95 rpm and beyond. I like to spin, and it is getting bothersome. I find myself shifting up, to a slower cadence than I want, to keep the seat tube from wiggling too much.

I see that the new gen Domane SLR has adjustable IsoSpeed. Maybe the flexy post has been an issue, especially for bigger riders?


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## Dry Side (Oct 6, 2012)

I have a Domane 6.9 and average 95 cadence. I am 5'11" 150 lbs. I have not experienced any bounce. The Domane 6.9 does have a seat mast versus a seat post. I demoed a Domane SLR which also has a seat mast and could not feel any difference in the ride from my older 2014 Domane. I rode over as much bumpy terrain as possible. The IsoSpeed adjuster was near the bottom for maximum flex.


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## uncrank (Feb 12, 2012)

*Might be a technique issue*



jeff400650 said:


> It has become apparent to me as I get fitter and ride more, that the flexing seat tube is occilating with my pedaling when my cadence gets faster... at maybe 95 rpm and beyond. Maybe the flexy post has been an issue, especially for bigger riders?


One of the common issues for riders developing higher RPMs for the first time is to maintain a round stroke as opposed to primarily an up and down stroke, at high speed. That's one of the reasons elliptical chainrings come and go Osymetric chainrings: do they work? - Cycling Weekly Back in the old school days of steel Columbus tubing, 5 speed cassettes and stiff as a brick wheels with high flange hubs, it was more noticeable to bounce in the saddle when RPMs exceeded the rider's ability to maintain a smooth stroke. Carbon bikes with wider gearing make it a lot less common. If you have access to a fixie or spin class bike with a weighted flywheel, try spinning at high speed with low resistance and see if you bounce. If you do, working on rounding out your pedal stroke will take away the bounce while letting you maintain the comfort of the softer setting.


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## jeff400650 (Mar 29, 2014)

Oh great... You mean I have to improve myself instead of just getting a new bike. Jeez.

I will say though, that I happily spin along on my steel frame Surly Disc Trucker without bouncy bounce. I like the more solid feel.


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## uncrank (Feb 12, 2012)

*Consult the velominati...*

I won't tell your wife  Hmmm... The more flexy the seat post, the more it will pick up subtle variations in up-down force. If you, for example, push down much harder than you pull up (or don't really pull up at all on the up stroke) you will reinforce the bounce. Since the Surly doesn't flex this way, but is probably engineered with long wheelbase, compliant frame, low flange hub, larger tires, etc. to absorb road shocks --all much more compliant than the equivalent parts on the Domane designed for race sprinting and handling--the parts on the Surly that absorb shock vibrate at different frequencies. The more rigid frame and wheels on the Domane transfer all shock absorption to the seatpost/tube. You might try spinning as fast as you can--say 10 rpm higher than when the bounce starts on the Domane on your Surly and see what happens. Perhaps the other way to look at it is that a smoother spin will enable the upgrade money to go to whatever bike you don't have. Purchasing new bikes should never be limited to having a problem with a current bike. Please see Rule 12 Velominati › The Rules


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