SeatSlip

October 10, 2005 11:14 AM

When riding my bike, why do I tend to slip forward on the saddle? What can I do about it?

I find my butt is most comfortable when perched up on my 'sitz' bones at the back of the saddle. However, I find that as I ride I typically slip forward on to the 'nose' of the saddle rather than sticking back at the rear.

I'm riding a specialized 'split' saddle. It's set to a comfortable horizontal angle (almost level). I've recently switched from a too-small frame to a correct sized one, but the problem's persisted. My saddle height seems right or very close to it. My bars are set a bit low (below saddle height), and ride more 'forward' than upright. Also, the bike is fixed gear, so their ain't no coasting (not sure if that matters or not).

I've read quite a few bike fitting articles, none that I've found addressed this particular issue. You advice is appreciated!

posted by daver to sports, hobbies, & recreation (14 comments total)

Maybe the reach is too long? Have you thought about a shorter and/or higher-rise stem? You might be too stretched out.

As a stop-gap, you might try loosening the seat and sliding it forward a bit on its rails, then re-tightening. If that fixes the problem, you could go for a shorter stem.
posted by killdevil at 11:33 AM on October 10, 2005

The only thing that I came up with after reading your question and more inside is that you might want to try moving the seat forward on the rails under the seat so that the seat itself is closer to where you end up sliding to.

Did that make sense? Or was that only in my head?

You might try to find a local bike shop that can help you adjust your set up so you don't slide around.
posted by fenriq at 11:35 AM on October 10, 2005

Are you sporting drops? This sounds like a reach or a saddle position thing. Try tilting the nose of the saddle up 1-2 degrees. This is much more comfortable for me and may help out. If this is a reach issue, try a moustach bar or bullhorns. This will bring you a bit more upright and the bullhorns will allow you to get far enough forward to skid easily. If you really like your drop bars, try a stem that doesn't drop so much. If you are tall, you may try a riser stem. Usually a bad idea for short to medium folks, but good for tall follks.
posted by jmgorman at 11:47 AM on October 10, 2005

Tilt the front of the saddle up a little. The only downside to doing this is that you'll be putting a little less weight on your hands and a little more weight on your butt. Not really a big problem.
posted by dial-tone at 11:55 AM on October 10, 2005

Don't adjust your reach by moving your saddle forward. That will disturb your pedal stroke. I would start with something easy like tipping the nose of the saddle up a bit. Ideally it should be at the same height as the rear of the saddle. Does yours tip downwards? Saddle angle is almost always the culprit when sliding forward.
posted by caddis at 11:57 AM on October 10, 2005

Go to a bike store that sells high-end racing bikes. Ask them to fit you to your bike. They might charge you for it, or they might not, assuming that you'll come back to them for future business, but they'll have some sort of bike fit system there that they'll be able to dial you in perfectly on (and, if necessary, they'll have parts there to swap in if you need them to fit.)
posted by mendel at 12:05 PM on October 10, 2005

I have the same problem in spin class-and my fit is pert near perfect-so for me it is simply a matter of sliding back-and bending my back at the waist a wee bit.

But I would go be fitted at the bike shop first.
posted by konolia at 12:22 PM on October 10, 2005

This is very possibly a reach issue, as others have said.

Another possibility is that your butt wants to be farther forward relative to the bottom bracket, regardless of reach. You may have heard of the "knee over pedal spindle" (KOPS) saddle-positioning trick--once you get the saddle height right, you slide the saddle fore/aft so that, with your feet in the 9:00 and 3:00 positions, the soft spot just under your kneecap on your forward leg is positioned directly above the pedal spindle. Obviously this doesn't work for everyone, and it's more a rule of thumb than a rigorous biomechanical truth, but it's a thought.

I prefer a very forward saddle position myself--my saddle is all the way forward on the rails.
posted by adamrice at 12:31 PM on October 10, 2005

I once had the same problem, and did what many here are suggesting: I tilted my seat up a couple degrees.

It didn't take much of a tilt, but it greatly improved my ride.
posted by Matt Oneiros at 2:28 PM on October 10, 2005

Or KOPS might be a myth. Some good advice here. Try tilting the nose of the saddle up very slightly. A shorter stem might help, or raising the bars a bit (threadless or quill stem?). A professional fitting can be great, but nobody around here does it for free, unless you buy a bike from them. Then they rebate the fitting fee.
posted by fixedgear at 2:30 PM on October 10, 2005

It's either reach, saddle position, or saddle height, in that order.

Problem #1: Reach -- proper fix is a shorter top-tube. That's hard to adjust. Secondary fix is a new, shorter stem. Tertiary fix, if you can make the adjustment, is a higher stem, but if you're going for race position, that's the wrong answer.

Problem 2: Saddle height. If it is too high, you'll move forward in the saddle as your hips wiggle. If you're clipped in, and your hips are moving as you pedal, your saddle is too high. Too low, and you go off the back of the saddle when your on the hammer.

Problem 3: Nose of the saddle is low. The "ideal" position for the saddle is dead flat, as in "use a bubble level and get it truly flat." The risk of nosing the saddle above level is more pressure in an area of your body that really can't tolerate such. Riders in aerobars often have to drop the nose of the saddle, since they're not flexible enough to run in the aerobars and keep the pressure off the parts that hurt. That's fine when your in the aerobars, but you'll be sliding off otherwise.

Problem 4: The saddle is, in fact, too far back. This almost always happen on people with shorter legs, proportion wise, to their torso. (Reach typically happens to people with long legs and short torsos.) Fix is easy, unless your saddle's already full-forward, in which case, you need an offset saddle post, or a new and smaller, bike, which leads to...

Problem 5: All of the above, known as "The bike's too damn big." If you're on a 58cm frame, and you need a 50cm frame, well, there isn't much that can be done. The typical sign of a grossly oversized frame is you can't stand over the top tube, but with the various non-flat or non-existant top tube frames, that clue-bat has gone away.

Fixes:

1) Get thee to a real bike shop, and get fitted. If you're a racer, get to a racing shop. If you aren't, get to a touring shop. Fitted for racing means high saddle, really low bars, and a flat back. Unless you're a racer and flexible, you won't have a flat back, and this position will be hell. Heck, for racers, it's still uncomfortable, but it's faster, and that's all that counts to them. If that's your thing, though, that's who can get it for you.

Touring guys don't like pain, and don't care as much about speed. They'll fit you in a much more comfortable way.

In both cases, if you wear clipless, bring 'em and ask for them to be fitted as well. In the end, if the bike is workable, they'll make it so. For large problems, you may need parts.

2) Have someone watch you ride. If your hips are wiggling, the saddle needs to come down or forward (or, if you want to maintain the same angles, both.) There are thousands of theories on saddle height, but the only one I know that is dead-certain-true is wiggling hips=too high. What it really means is "your pedal is too far away for your leg to reach, so your whole body has to move to reach it." That's energy that isn't moving your forward. Worse, much of your power comes from muscles pulling on the hips, which are held steady by muscles in the torso. If you hips are dipping, you're throwing away that power.

For newbies, too low is far better than too high, for both "somewhat" and "very." Experienced riders hate too low, because thier legs gripe at not getting full extension, and they feel like they are riding a toy bike when they try to spin. For the record, a saddle that's way too low leads you to sliding off the back of the saddle.

3) Have someone or something hold the bike. Saddle up, clip in, sit at a comfortable angle. Close your eyes, take your hands off the bar, holding yourself up with your back, tap your helmet, and put your hands back. You can open your eyes now.

Did the hands hit the bar? Cool. Did you miss badly? You're reach is very wrong -- if your wrists hit, too short, if your fingertips barely grazed the bar, too long. This isn't a fine test, but it'll detect something that way wrong quickly.

4) If the frame doesn't fit, there's only so much you can do. If you need to ride a 50cm, you can easily fudge a 48 or 52, but a 46 or 54 is going to be tough, and you just aren't riding a 58 in any sort of comfort. Worse, if you don't have a normal proportion between your legs and toros, fitting a frame gets tough. The correct, and expensive, answer is a custom frame, but the usual answer is "fit the legs, fake the reach," since it's much easier to fix a reach problem than a leg problem.
posted by eriko at 5:08 PM on October 10, 2005

For newbies, too low is far better than too high

Too low can be dangerous to your body. A too low saddle will frequently cause pain in the front of your knees. All riders face this malady, but if you have issues with your joints in general, be very careful about getting your saddle too low. Of all of the adjustments on the bike saddle height is the most important by far. Repetitive stress injuries are a bitch to recover from. I would much rather have my saddle too high; at least it won't injure me. It is pretty noticeable anyway. You should be concentrating on making perfect circles with your feet while you pedal, and keeping the rest of your body still. If you detect other movement something is wrong. Having someone watch your hips is easiest, but once you get the hang of things rocking hips are as noticeable as a pebble in your shoe.
posted by caddis at 6:56 PM on October 10, 2005

I always want to play with my saddle tilt, but the seatpost top seems to be 'ridged' or 'indexed'. I have it in the position which is closest to level at the moment, but I'm a bit of a tweak and I wonder if my seatpost is 'different' from the norm.

I shortened my stem by 2cm a couple of years ago. It made steering a little different, but was much more comfortable day-to-day.

I tend to slide fore-aft on my saddle depending on terrain. For long climbs, I slide back. For descents and long pulls in the drops I'm centered or just a bit forward. Perhaps I need to raise the saddle a touch?
posted by Wild_Eep at 8:00 AM on October 11, 2005

I always want to play with my saddle tilt, but the seatpost top seems to be 'ridged' or 'indexed'

You can safely grind (a bench grinder is handy, but a Dremel tool will work) away the ridges and get an infinitely adjustable seatpost tilt. Be sure to make the bolt one grunt tight.
posted by fixedgear at 2:01 PM on October 11, 2005