Bike fit issues sliding on saddle

Last couple month I observed I am sitting forward on a bike. I thought it was a bike fit issue and did a pro bike fit.
The fitter did the Retul bike fit and measured everything and it technically came ti the same size what I was riding but with his “eye” he said let’s move saddle further and reduce height. So we did. That resulted in inner knee problem so he brought back the saddle. I ride with lesser saddle height now compare to original setting but keep on coming towards the front of saddle. This happens mostly when I am pulling in group rides.

At homes on the trainer I can sit in same position doing 2x20 FTP intervals and don’t feel need to move.

So what exactly I need to correct when I am riding outside? I can produce power no issues but frequently sliding further with or without producing more watts.

Which direction are you sliding when outside?

And to ask the obvious question, have you discussed this with your fitter?

The saddle is level. I am sliding forward towards the nose. Yes I asked this to him many times and during follow up visit too. He has no idea and saying change the saddle. I am not convinced he is right here with change saddle advice as I am having the issue on 2 bikes. He is respected fitter in our area.

OK, you’re moving forward in harder efforts outside, but not inside. Do you have a guess as to why you move forward?

  • Is it to deal with a saddle comfort or positioning issue?
  • Is it about how you feel for pedaling effort in the legs or elsewhere?
  • Is it about how you feel for reach to the bars at that effort?

All we have right now is a symptom & use case (sliding forward outside under higher load), so trying to identify the WHY here is needed to address what other change might be beneficial.

  • I move forward unknowingly. Once I am forward, I feel the saddle chafe and I try to readjust the position a bit.
  • No I dont feel the efforts apart from that chaffing once I am forward.
  • Reach to bars is within limits. That was my first question to fitter. With this fitting as well as from before, I can go aero with my wrists hanging in front of the bar without problem when I am on back of saddle.
    My question to fitter was I don’t always feel the sit bones and his reply was its ok not to fill it.
    The only answer fitter gave me to change the saddle.

That’s a tough one. One key difference to recognize here between inside and outside is the lack or presence of force on your body due to wind resistance. I could see that you pushing the effort into the wind outside, would gravitate towards the forward part of the saddle. This basic action is common from riders with the cliché of “riding the rivet” as a reference to the old riveted saddles.

With respect to the changes, you are lower saddle height than before, and the saddle fore-aft is back to original.

  • When we consider that a lower saddle height (assuming no other changes), will lead the the saddle moving forward about 1/3 the drop distance (due to the inclined seat tube angle), there are two cases to understand where you actually are now vs before the fit.
  1. Dropped saddle and returned saddle to the same exact location in the seat post rails. This results in a lower saddle AND one that is more forward (roughly 1/3 the drop distance). This also means the effective reach may be a bit shorter to the bars (ignoring saddle height impact on the final geometry).

  2. Dropped saddle and kept the saddle fore-aft relationship relative to the bottom bracket, by moving the saddle rearward in the seat post clamp. This is lower saddle with roughly equal reach to the original case.

Oddly enough, neither of those cases make sense to me as to why you’d be sliding forward now vs before the height adjustment. Depending on the saddle height change (not exactly identified above?) could lead to you now sitting with a different pelvic tilt on the saddle. If that is the case, I have seen people that experience a change in comfort and relative position on the same saddle and angle.

Again, none of that explains why you get one issue outside vs not inside though. Sadly, I don’t have a lot of answers or direction. At best, I could see doing a test with moving the saddle forward maybe 5mm and try rides outside and inside.

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I kind of think this sounds perfectly normal. Have you heard the term “on the rivet”?

Maybe riders do this to open up the hip angle as they put out more power?


Geraint Thomas is probably not an ideal example to use… He has to have one of the worst saddle to ass interfaces in the pro peloton, regardless of what kind of power he’s putting out, he’s got more than half of the saddle sticking out behind him. He could probably use some advice from this thread as well… somewhat sarcastic…

Have you watched this video?

There are others but this one talks about symptoms of the saddle position being too far forward or backward. Might give you some ideas.

I have had a problem scooting forward during powerful efforts. For me, it is because I start to lift myself off the saddle as I press hard on the pedals. It could be the front end is a little low.

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