Lowest stack saddles? Long seatpost, short leg issue

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  • I generally need a 62.5cm B.B. to top of saddle and the new frame I am building up will only go to around 64cm or so.

    The seatpost is specific to the frame and bulges at the top so will not go further into the seattube (at least they’ll be no slipping?!)

    Bike is a fixed Isaac Efficiency in XS size.

    Current cranks are 170, and I have 165 to go on, so that should allow me to have 5mm extra seatpost length than normal.

    I currently have a romin with carbon rails, will I find another saddle that has up to 10mm lower stack?

    Do I need to look for 155/160 cranks? Which cleat systems have higher stack? Currently on speedplays but could use SPD mtb if higher.

    Any help would be much appreciated!

  • Spice Girl platform shoes

  • You need longer, not shorter cranks.


  • IIRC, @mdcc_tester explained a while back that having shorter cranks doesn't move the saddle up, but moves it down? Something about hip closure angles. I might be getting my wires crossed though?

  • Generally you set saddle height by measuring leg deflection at the most extended point (when the cranks are inline with the seat tube) so for shorter cranks you would normally increase saddle height.

    It does, however, reduce the hip closure angle at the top of the stroke meaning there is potential to lower the back angle also.

  • Yeah, generally shorter cranks = lower saddle.

    You don't want to have to 'reach' any further at the bottom of the pedal stroke. As a result you do not bend your knee at much at the top of the pedal stroke but this can help you get lower at the front without closing your hip angle too much.

  • At the bottom of the pedal stroke, it’s going to be shorter distance from the top of saddle with a shorter crank surely?

    The reach would be longer at the top of the rotation, but that’s not the issue as opening up hip angle isn’t such a problem?

    I’m pretty sure my bike fitter suggested putting up saddle 5mm if I changed my road bike to 165mm from 170mm, and also may allow me to drop a front spacer.

  • Parts bin build up for reference.
    The frame is the smallest they make it, just the seatpost will not bulges out.

    Just measured my Selle slr, and it seems to have a stack of about 35mm, compared to the romin on there at the moment at around 42.

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  • Also need to find washers or lower diameter track nuts for the front wheel as the lawyer tabs/lips foul the tracknuts I have at the moment.

  • Yeah surely leg deflection at pedal low point has to take precedence over hip closure angle at high point?

    In an ideal world you'd be setting up both seat height and crank length together (and probably a host of other things at the same time) but in reality you'd set by leg deflection at low point and hip closure would be a bit of a side effect of the crank length you're using.

    @Acliff is that the convertible tt/'track' one? If so, my only experience of them is that they have a horrendously low bottom bracket height so fitting cranks from a kid's bike might be your only hope of being able to turn corners.

  • Oops you posted that photo while I was typing, that looks exactly like the one that is the only bike we've ever turned away from the velodrome.

    The pedals were almost hitting the bankings in the straights!

  • the lawyer tabs/lips foul the tracknuts

    File them off.

  • It’s supposed to be more for fixed TTing than vélodrome use I think.

  • This doesn’t look safe....

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  • Calm down, it's not an inverse shim...

  • Do not want. Get shorter bolts for sure

  • I generally need a 62.5cm B.B. to top of saddle and the new frame I am building up will only go to around 64cm

    Then get a different frame.

  • Got a closer pic of the saddle mount?
    You might be able to unbond the alloy clamp from the carbon post, chop and then bond it back in...

  • Yeah, you are totally correct, I was mixing up your situation with higher/lower saddle. Basically, in your case, shorter cranks will help you.

  • I’m thinking that will be the overall outcome, but the frame was cheap and was XS sizing, with the frame measurements being within my normal fit.

    Didn’t know that the seatpost wouldn’t go down any more....

  • Lowest stack saddle I’ve ever come across is the Tune Komm vor

  • It’s worse than it looks, basically a gooch hole punch.

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  • Lowest stack saddle I’ve ever broken...

  • Ha - after a lie down on ice at 40kph it’s a sure thing!

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Lowest stack saddles? Long seatpost, short leg issue

Posted by Avatar for Acliff @Acliff