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Old 04-07-02, 08:49 PM   #1
Bbmoozer
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how to move seat back more

Hello biking enthusiasts.
I've been having some front knee pain, so it was suggested to move my seat back. I used my tools to slide it back as far as I can without slanting it. But I can't go any further. Maybe the bike frame is a tad too small for me then?
Is there something I can attach like some sort of extension to be able to slide it back further?
Sarah
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Old 04-07-02, 08:50 PM   #2
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You may be able to find a backward-curving seat post which is compatible with the inner diameter of your seat tube.
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Old 04-08-02, 05:24 AM   #3
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....But then, you would have to pedal with your feet too far forward. Sounds like the bike is too small for you.
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Old 04-08-02, 05:34 AM   #4
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Do a "knee over pedal spindle" test. With the crank extended 90 degrees forward and your foot positioned normally on the pedal, and you seated normally on the bike, drop a weighted line from just below the little point on your knee.

If your saddle is all the way back, the line should intersect the pedal spindle or be behind it. If it's still forward of the spindle, yes, your frame may be too small.

If you're already using a seatpost with setback (1" setback is about the maximum), you may be done. If your seatpost is the type with the clamp exactly centered on the tube, then maybe a 1" setback post will help. They're common and not expensive.

What's your "cycling inseam" measurement, and how long are your cranks? Occasionally too-long cranks can contribute to some types of knee pain.

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Old 04-08-02, 08:19 AM   #5
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My cycling inseam and cranks????? Help! My normal inseam is about 30. What's a cycling inseam? And what is a crank?
Newbie here.
Thanks, Sarah
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Old 04-08-02, 08:56 AM   #6
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Cranks are the metal bars that spin, with the pedals on the end.
They come in different lengtht, but most bikes have 170mm slapped on for a one-size-fits-all economy.
The cranks spin about the bottom bracket (at the bottom of the frame).
The layback of the saddle from the bottom bracket depends on:
1. The angle of the upright seat-tube of the frame.
2. The layback of the seatpost (which fits inside the seat-tube)
3. The length of saddle rail on the saddle.

Increasing the size of your frame will have no effect on saddle layback, only on the amount of exposed seatpost, which is irrelevant here.

The starting point for good positioning is to have crank length appropraite to your leg length, and the knee joint directly above the pedal when it is at the 3:00 porition. This is a starting point for fine tuning.
If you really do need to move your saddle back further, you can get seatposts with more layback. The clamping mechanism is set further back from the post. NB seatposts come in a variety of diameters, you need one which is a good fit to your seat-tube, or you may damage the frame.
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Old 04-08-02, 09:11 AM   #7
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wow.... pretty intricate stuff here!
Ok..I have a Cannondale Silk Path hibred. If I were to get a seat post that has an angle, any ideas where I can get one that's cheap? (I surfed a bit and they run from 89-150.USD).
Also... can I measure mine and then order one that will fit? In inches or cm?
Also...where on my bike does it say how big it is...19",21" etc... I don't know my frame size. But the bike is only about 3 years old and I was 'fitted' at a pretty reputable bike shop here in town. I'm about 5'4 1/2" tall.
Sarah
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Old 04-08-02, 12:46 PM   #8
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Quote:
Originally posted by Bbmoozer
But the bike is only about 3 years old and I was 'fitted' at a pretty reputable bike shop here in town. I'm about 5'4 1/2" tall.
Sarah
Why not go back to that shop, for starters? One of the things youy buy when you deal with a reputable shop is ongoing support, and fit issues are certainly one area they should be willing to address.

And don't screw around with knee pain. If it persists, have it looked at before it gets worse!

While improper bike fit can certainly cause knee problems (and yes, being too far forward is one potential cause of tendinitis in the front of the knee, and too-long cranks can be another) it's less likely to crop up suddenly unless you've drastically increased your mileage.

You should check the knee-over-pedal-spindle position so you know for sure if this is seriously out of whack. And somewhere on the back (frame side) of the cranks the length should be engraved. Probably a number like 170 or 175. 175mm cranks are probably too long for a 5'4" rider.

Take a look here http://www.coloradocyclist.com/bikefit/ to get an idea of some of the issues affecting bike fit.

Good luck
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Old 04-08-02, 01:13 PM   #9
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thanks Rich... I'll check out that site. And, you are right, swinging by the place where I bought it would be a good idea.
I've been taking spin class for years with no problems on my knees. Most I've ridden my bike at one time was about 18 miles until recently - now with training for a century, I'm putting miles on fast and hard...thus the increased time on this bike.
Sarah
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Old 04-08-02, 01:30 PM   #10
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The Colorado Cyclist site is for athletic cyclists.

A more universal (and IMHO more useful) reading on bike fit is
http://www.peterwhitecycles.com/fitting.htm
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Old 04-08-02, 02:20 PM   #11
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thanks michael... hey, look at that, I am now a 'member' vs. a junior member. When do you become a 'senior member'?
Sarah...gotta get back to work instead printing out all these emails
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Old 04-08-02, 03:01 PM   #12
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Quote:
Originally posted by MichaelW
The Colorado Cyclist site is for athletic cyclists.

A more universal (and IMHO more useful) reading on bike fit is
http://www.peterwhitecycles.com/fitting.htm
I like White's approach in general, aside from his extreme wordiness, but it doesn't really address the OP's issue about knee pain, and it assumes a drop-bar touring bike. I think KOPS is important -- more important than White credits -- to reducing knee stress, and the CC site has a photo showing how to determine this. Worth a thousand words.

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Old 04-09-02, 08:50 AM   #13
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You can get a "laid-back" seatpost for your bike. The posts come in different diameters. You've got a Cannondale, so it's a 27.2 mm diameter.

Thomson makes a seatpost with a lay-back of about 1.5", actually, Cannondale is also making one! Go to the shop where you bought your bike and have them check your measurements and see about possible modifications.

L8R
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Old 04-09-02, 09:13 AM   #14
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This is a pretty interesting link for
bike fitting, goes into saddle height, for aft adjustment etc.
the site is Abicibike
Hope this helps,
Marty
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Old 04-10-02, 08:00 AM   #15
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Sarah,
Go ahead and to the knee over spindle check, but keep in mind that saddle height can affect knee pain, too. Somewhere I read a rule of thumb, but it's like the old "feed a cold, starve a fever" or is it "starve a cold, feed a fever" thing no one can ever remember. Basically it goes pain in front of knee, raise the saddle, pain in back, lower it. But I might have that reversed. Let's see if anyone else has seen this before you take it as gospel. Simply put, your leg should be just slightly bent when the pedal is at the bottom of the stroke. Personally, I haven't noticed knee pain moving the saddle fore and aft. I actually adjust that more for upper body comfort. I DO notice the difference when my saddle height is not right.

AND, remember my other reply on spinning? If you are pushing a gear that's requires too much effort it might cause pain.
FWIW,
Raymond
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Old 05-05-02, 04:53 AM   #16
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Hi,

I had a similar problem. I had moved the seat as far back as possible, but it didn't help me out at all. The bike was just too small for me and I exchanged it for a larger bike (which cost a little more, oh well).
Hope your situation worked out OK.
Brian
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