bleui

As a result of moving my saddle rearward (Steve Hogg's point of balance) and wanting to have a more upright position, I also change my stem length from 110mm (-17) that I've been on for about a year to 80mm (-17) hoping to maybe have a similar reach. But after a couple of days in this new position I had two occasions that I need to pull the front brake really hard and on both occasions my rear wheel lifted way off the ground and almost sent me flew over the bar had I not set my cleat tension to very-loose.

Now I don't remember having to brake real hard during my life with the 110mm stem position, but is shortening your stem contribute to this (physics?) or that I'm not just used to the new position?

edit: move the saddle aft position by about 18mm and didn't alter the saddle-to-drop position (105mm)

k_kibbler

a. Saddle further back = more weight over rear wheel = lower chance of going over the bars

b. More upright position = higher center of gravity = higher chance of going over the bars

Without more details of your old and current position, how much further back, how much more upright, A and B are a wash and either you're not used to hard braking or you're not used to your new position, or both. Stem length alone shouldn't directly affect braking.

generalkdi

Saddle placement should not have impact on heavy breaking since wherever your saddle is, you should shift your weight all the way back to keep maximum control of the bike while braking.

So it's either the center of gravity that is a bit higher, or the driver that is not yet used to his new position?

pdedes

user error

RNAV

What you describe shouldn't affect the braking performance.

Spit-balling, though, it's possible your brake cable housing could have had a sharp bend in it (causing increased friction), which could have been alleviated by repositioning the handlebars, resulting in reduced friction. When you apply the same amount of perceived effort, you get more braking action.

To clarify, if you're moving your saddle aft, you're also effectively lengthening the saddle-to-BB distance. Steve Hogg even mentions that when you adjust the saddle fore/aft, you have to then readjust the saddle height to compensate for this. Based on what you wrote above, it sounds like you didn't readjust your saddle height (unless you did, and also made a corresponding handlebar height adjustment to keep the same saddle-to-drop position).

wphamilton

Steve Hoggs makes a lot of sense, except for his notion of setting the seat by crouching balance, and your question relates to why he is wrong. As mentioned earlier you should shift your balance back from the seat during a panic brake. The balance point when braking, when sitting, or when pedaling, is different from the center of gravity while crouching.

A shorter stem does not mechanically make over the bars more likely, except if you change your position and posture as a result of it.

GravelMN

Get your butt back and drop your elbows a bit and your chance of going OTB will be greatly reduced. A more upright position can affect braking dynamics, but if you moved both your seat and handlebar positions back with no other changes, this should shift your center of gravity back without raising it substantially, which should reduce rather than increase the chances of rear wheel lift. Front brake modulation is the more important factor here. Maximum braking effect occurs right at the point where both wheels are still rotating and the back wheel is just starting to lift. Once enough weight comes off the back wheel that it locks you lose braking effect from the rear wheel and gain no additional braking force (which begins conversion to the rotational force that could eventually throw you over the bar) from the front.

hueyhoolihan

standing on the pedals, riding downhill, long stem, light bike, short wheelbase, hard front braking all contribute to a header. not a complete list...