Long Tom

Tonight, in a game effort to duplicate setups between two bikes, I ended up attempting the dreaded "Princess and the Pea" maneuver. Wherein, I built up a "pea" out of gaffer's tape*, stuck it to different spots on two bike seats, and tried to use the sit-bones in my ass as a measuring device to establish a seat/crank relationship.

I learned several things. First and foremost, the ass, or at least my ass, is shall we say a blunt instrument. It appears to lack the sort of sensory input required for, say, THIS. My theory is that we humans lack a prehensile ass, but it's just a theory.

At any rate, I failed it establish a reliable "sit bone centerline" by this method, even after building up my pea to almost a tower. And, I actually seem to have injured myself a bit, by trying to grind my sit bone on one side (the right side, since you ask) into a big-ass pea trying to feel it well enough to establish said position.

The whole thing was like a Monty Python skit, and is amusing as all hell in a twisted sort of way, except that I do have a sore right butt cheek. Be careful out there, people.


*gaffers tape is like what you always wished duct tape was. And you'll gasp at the price. Buy a roll anyway. Thank me later.

Bob Dopolina 

How did you not know that that wasn't going to end well?

Long Tom

I guess I just ass-u-me'd my ass was capable of better.

I stand asshamed. Butt I gave it a cheeky effort.

hueyhoolihan

the human a ss is prehensile in a manner of speaking, but it lacks dexterity...

hueyhoolihan

not a good idea to "fix" a post, with questionable content, when someone else's logon name is still presented in the quote. could you fix it again please?

PhotoJoe 

Long Tom - you are soooo right. Gaff tape is the answer to everything. Yes, the price is steep, but I hate removing residue from cables.

hueyhoolihan - you are also right. It's not cool to "fix" a quote making it into "questionable content". So, I gaff taped that post to the inside of the trash can.

Carry on.

Long Tom

Huey, my sincere apology, sir. My bad.

Ok, in the cold light of day here..... how the heck DO you set seat setback to be the same on two bikes that have different seatposts, seats, and of course frame geometry?! Knee over spindle? Not a big fan of that but it's the only way I can see. I had hoped to just locate the center of my sit-bone on each seat then measure from that, but as I said above.... that got real silly. Not that I didn't keep trying. Too long.

I think my main beef with the KOPS measuring method is that it's basically impossible to really know you've got the cranks horizontal, at least working solo, and being just a little off really changes things. But it might be the only dang way to do this.

I don't advise the "pea" method. I actually irritated my sit bone a bit. Not mention irritating Huey and a moderator!

hueyhoolihan

thanks. i appreciate it. it's just that these things can be Googled and it could look bad if it managed to turn up in a court case involving my x-wife, if you know what i mean...

canam73

I don't expect to set bikes with different frames, post and saddles identically. But to get a comfortable start with a new bike I typically run a level up from the CL of the crank on a bike I like the fit on and then measure back to the widest part of the saddle and also set the height that way. From there I adjust as needed by feel.

rpenmanparker 

There are so many good reasons to ride identical saddles on all of one's bikes, and this is just one. If the saddle is the same, nothing else has to be. Just measure the horizontal distance from the tip of the saddle to the perpendicular to the center of the crank spindle (like KOPS but simpler to do). Duplicate this on the other saddle for setback. Then measure from a fixed point on the saddle to the crank spindle for height. When you correct the second saddle for height, reset its horizontal position by moving it forward or back 1/3 the distance of the change in height (Higher saddle means bring it forward 1/3 the amount it was raised. Lower saddle means push it backward 1/3 the amount it was lowered.) Done and done. BUT that is all predicated on identical saddles. Why would you ride anything else?

Long Tom

Well, because my "sports car" bike, the one I'm trying to match the fit on, is a 2014 Roubaix Expert with an expensive carbon fiber/Ti Specialized saddle and very expensive CG-R seatpost. My new bike is a utility bike- will be locked up around town etc.... an expensive saddle/post would just get stolen.

woodcraft

https://www.youtube.com/watch?v=n8a0Qguwa5E

rpenmanparker 

Yes, but Specialized makes the same model saddle in several different grades so all dimensions are the same except weight. And the post doesn't matter with the method I described.

Long Tom

Point conceded, and maybe I'll go that way. For now I'm just gonna use the saddle that came with the bike. We'll see how that goes. Just don't want to head too far down the rabbit hole chasing perfection on this bike (which is painfully ironic, given the thread content, also conceded!)....

gc3

Then perfect fit matters not at all. About the right height, about the right reach, position fore-aft of the bottom bracket that suits you best (please no KOPS), should be good enough for tooling around town on relatively short rides....

Long Tom

Well. Allow me to add to the self-contradictory trainwreck I've got going here by saying, it's a summer utility bike, but winter conditioning bike. For the latter I do want to dupe the fit I have going on my Roubaix (at least the saddle/cranks relationship part) because its working very well for my knees.