saddle geometry


New Member
Jun 29, 2022
got a new saddle today. A Bontrager (trek).
It's more comfy than the San Marco I had, but I still feel like I should be further back on the saddle. I'm slipping forward a bit.
Is that a function of saddle height, front/back or tilt, or perhaps all 3?
If you're slipping forward, you're either tilted forward or your saddle is too far back. Or your stem is too long.
I slid the seat forward a bit. It's not tilted. Same stem I've been riding for a decade, not that that necessarily means anything.
Perhaps another bit forward.
Your position is usually determined by leg clearance. Your legs have to fit in front of the wings. When a saddle is too wide for a person, they may end up TOO much in the front.

Nevertheless anyone might end up further in the front than they might expect, so long as they sit with a forward (anterior) tilted pelvis (such as 75 degrees). On many saddles, the only way to fully utilize the platform in the back is to ride with backward (posterior) pelvis tilt. The pelvis position on the saddle does not change objectively, but the part that is low and touching the saddle changes: It's either ramus (front of pelvis) or tuberosity (back of plevis). In the worst case it would be the pubic bone (most frontal part). With a neutrally tilted pelvis (say 85 degree), the tuberosity just touches the frontal marginal zone of the t-shaped wing. But with posterior pelvis tilt (say 95 degree), the tuberosity may move a bit deeper into the wing.

Btw: Pelvis tlt degrees are counter-intuitively labeled like this: upright is 90, horizontally forward is zero.

Some saddles have a ramp in the back and demand that you ride in very tilted pelvis position, sitting fully on that ramp. If you just refuse to go into this angle, you may end up in front of it, with upright pelvis. But then the saddle will be noticably too narrow for you. Unless your saddle was designed or a much bigger person.
Your pelvis tilt is determined by the handle bar position but also individual habits of how you relate torso and pelvis, for example bloating, indigestion, bodyfat, gall stones, enlarged spleen or liver will inspire ppl to maintain anterior pelvis tilt relative to the torso. When the handlebar forces the torso into a forward angle, the pelvis will then be extremely angled, on the ramus (its okay) or possibly on the pubic bone (trouble). That means pressure is in the middle (may be okay on some v-shaped saddles) of the saddle or on the nose (bad).
You can also roll the handle bars back a bit. And or slide the brake levers back some on the bars.
Making it easier to reach the hoods. If you ride on the hoods often this makes it more comfortable and an easier reach overall.
Unless you're racing and want the aero advantage.
I also would slide the saddle along the rails to a more fore position.
Another idea get a seatpost with ZERO setback. This will also move the saddle up a bit.
thanks both for your input.
the 1st saddle I got was too wide. Got a different (both Trek/Bontrager). The 2nd is narrower but lacks the gel. Much less slipping but still bothers my inner pelvic bones.
Neither have a ramp at the back. Trek store has ordered me another version of the 2nd saddle with a gel pad for old boomers like me.
I'm reluctant to tilt up the saddle as my junk is already uncomfy.

I will try to rotate the handlebars up a touch. Not racing. Casual 10 to 15 in the park.

Though I've been riding this CAAD9 stock for a decade, I'm wondering if aging (back) and saddle change might be looking for a headtube adjust, as my palms are numbing a bit at the end of 10mi.

I was also looking at a Giant Fleet SL saddle that the friend what sold me the CAAD uses and likes a lot. He's much more a rider than I, riding centuries regularly.

I wish there was a decent shop nearly by that didn't charge $300 for saddle geometry fit. There are no more knowledgeable M&P bike shops around here. Seems more biz than enthusiast. Especially after pandemic.
I ended up trying a couple saddles based on seat bone measurement. But coming from a 125 to a 175, then a 165 was making things worse.
Long story short, a couple of stem changes I ended up at 145mm Bontrager with the OEM stem, 7º or whatever it is. So far so good.
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