Sliding down the seat

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Sliding down the seat

Postby bennelong.bicyclist » Mon Mar 08, 2010 6:47 am

Went for a longer ride on my newly-acquired Optima Lynx yesterday - just laps around Sydney's lovely Centennial Park (about a 3.8km circuit with a slight rise and fall) for about 90 minutes non-stop. Didn't fall off, was quite comfortable, certain leg muscles were complaining a bit towards the end, neck was OK, but I found that as I became sweaty, I kept sliding down the seat. This topic has probably been covered before, but does anyone have any suggestions? Velcro on the seat covering? A Ventisit foam seat, or cheaper equivalent? The Optima seat pad seems to be made from a Ventisit-like open foam, but it is covered with a fairly smooth material. I found that I was constantly having to push myself back up the seat with my legs.

Suggestions?

BB
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by BNA » Mon Mar 08, 2010 10:52 am

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Re: Sliding down the seat

Postby njg02 » Mon Mar 08, 2010 10:52 am

I dunno BB. I make occasional adjustments whilst riding but not constantly. I wear normal shorts with a bike shirt. Do you wear knicks? Is your seat pad velcroed or permanently attached to the seat? Is the seat pad sliding? Is it your clothes? I get fairly sweaty but don't slide around. My seat pat is nylon open weave in a few layers. I'm not sure if it is 'ventist'. Maybe once you get out on the street with a few more variables in the riding mix you may find you don't slide as much. Ask the same question on BROL and see how you go.

Regards

Neil
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Re: Sliding down the seat

Postby mikedufty » Mon Mar 08, 2010 11:57 am

oops, didn't notice it was the recumbent section - deleted post
Last edited by mikedufty on Mon Mar 08, 2010 12:18 pm, edited 1 time in total.
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Re: Sliding down the seat

Postby bradwoodbr » Mon Mar 08, 2010 12:16 pm

Can you post a picture of the seat cushion and cover as I am not sure which one you have?

The Lynx has rear suspension, you may get by with a thinner seat cushion than what it came with.
I am very comfortable on my Baron with a two layer Ventisit cushion.

Others may have more info and ideas, but the following has helped me get the best position possible on my Baron.

If you are sliding your boom (pedals) maybe too far away from the seat.
If each pedal stroke pushes you back into the seat, your boom (pedals) maybe too close to the seat.

Suggestions?
Adjust the boom length to bring the Bottom Bracket (BB) and pedals closer to the seat.
How to adjust Boom length.
Have someone assist with the boom. Measure and record starting position of boom (either Bottom Bracket centre to frame or to steering head).
Loosen the boom bolts.
Sit on the bike, wear your riding shoes, place the heel of one foot on its pedal until extended while keeping a bend in the knee (pedal at 3 o'clock position), ease your foot off the pedal and have assistant move the boom in, gently push with the heel on the pedal again extending the leg but keep your knee bend.
Tighten boom and test ride. Make sure the pedal are straight vertically.
Adjust until it feels about right (adjustments of 1 or 2mm make a big difference), then go riding for a few days and readjust accordingly.
If you have any knee strain on these rides you will need to readjust the boom length.
I always stick on tape, measurement marks and record all adjustments. This is so I know what I started with and what adjustment I made.

When you have the correct boom length, then you can adjust handlebar stem length and seat angle, although a big change in seat angle may affect boom length. Then adjust the boom like before.

Hope this helps. Let us know
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Re: Sliding down the seat

Postby Poiter » Mon Mar 08, 2010 6:47 pm

What Brad said..

My optimum position is with my shin bone centred on the dust cap on Crank if that helps.

BTW Ventisit ACS10 is not foam, it's an open weave mesh with internal spirals.
Some say it is too slippery for them.
I don't have a problem with it or with slipping.
Just spent 2 x 9 hours riding in deep rinse cycle over 440km.
Love the way ACS10 drains.

Poit
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Re: Sliding down the seat

Postby bennelong.bicyclist » Mon Mar 08, 2010 7:48 pm

Some shots which sort of show the Optima seat cover. Yeah, I was wearing lycra knicks. Maybe something grippier would help.

Image

Image

Adjusted the boom as described with an assistant, but will move it back in 1cm increments to see it that helps.

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Re: Sliding down the seat

Postby bradwoodbr » Tue Mar 09, 2010 12:20 am

A picture paints a thousand words - so does a digital image.
As well as checking boom length, I suggest you adjust your seat as well.
But change and test only one thing at a time. :)
From the image of your bike, it looks as if your seat is sitting up too much.
I think the seat needs to be reclined.
Try a 45 degree angle to horizontal as a starting point.
It will take time for your neck to strengthen and adjust to a more reclined position.
You can always put extra foam behind your shoulders to straighten up the top of your torso.
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Re: Sliding down the seat

Postby bennelong.bicyclist » Tue Mar 09, 2010 7:15 am

bradwoodbr wrote:A picture paints a thousand words - so does a digital image.
As well as checking boom length, I suggest you adjust your seat as well.
But change and test only one thing at a time. :)
From the image of your bike, it looks as if your seat is sitting up too much.
I think the seat needs to be reclined.
Try a 45 degree angle to horizontal as a starting point.
It will take time for your neck to strengthen and adjust to a more reclined position.
You can always put extra foam behind your shoulders to straighten up the top of your torso.


Yup. I put the seat up to make it easier to ride while I am learning. I'll try your suggestion of reclining it back a bit more and using extra padding to bring my upper back forward a bit while I develop the right neck muscles (and my balance while lying down).

And after that I'll fiddle with the boom length in 1cm, increments, if necessary.

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Re: Sliding down the seat

Postby JulianEdgar » Tue Mar 09, 2010 8:25 am

On my trike, which uses a Greenspeed-based seat shape (but it's a lot wider than a normal Greenspeed), I found that the greatest influence on sliding forward was the shape of the leading part of the seat. I have it it angled upwards slightly, otherwise I tend to get that uncomfortable 'sliding forward' behaviour.
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Re: Sliding down the seat

Postby bennelong.bicyclist » Sun Mar 14, 2010 11:04 am

bradwoodbr wrote:A picture paints a thousand words - so does a digital image.
As well as checking boom length, I suggest you adjust your seat as well.
But change and test only one thing at a time. :)
From the image of your bike, it looks as if your seat is sitting up too much.
I think the seat needs to be reclined. Try a 45 degree angle to horizontal as a starting point.


I put the seat back again to mid-position in its recline range, and the sliding-down-the-seat problem went away completely, and suddenly the boom length felt just right. Rode around Homebush Bay and Bicentennial Park for 90 minutes, very comfortable except for...

bradwoodbr wrote:It will take time for your neck to strengthen and adjust to a more reclined position.
You can always put extra foam behind your shoulders to straighten up the top of your torso.


...my neck, which was killing me towards the end of the ride. I think I really need a headrest - towards the end of the ride, riding with one hand behind the base of my skull to take the strain off my neck muscles resulted in complete comfort - felt like I really could ride all day like that (whereas after two hours on the convention DF bike this morning left me with a sore back and saddle-soreness - so I can see (or feel) the potential for all-day riding comfort on the bent, if I can just fix the neck ache. Interestingly, it was the muscles at the back of my neck that were really aching, not the sternomastoids which are the neck muscles used to hold the head in flexion as required on a bent - perhaps the muscles at the back of the neck still have to work hard to stabilise the head in that position? Anyway, a nice flexy headrest should fix the problem.

I must say that neck pain aside, riding the Optima is a blast.
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Re: Sliding down the seat

Postby bradwoodbr » Sun Mar 14, 2010 9:02 pm

Well done, you have made fantastic progress in a very short time. :) :)
Sore neck
The muscles you describe are the ones that took a while for me to strengthen.
Here is a good off the bike exercise I used to speed up neck muscle strength.
After I did this for a month I did not really need a headrest, but still use it as I think it is a great way to remain comfortable.

1. Put the base of a hand on your forehead. Push against your forehead with your hand and resist with your neck. Feel the muscles you want to strengthen working.
Do a series of 5 per hour or half day - whatever, 5 seconds push, 5 seconds rest.
2. Put the base of a hand on the back of your head and do the same.
Don't overdo it and use a heatpack if necessary to relieve tension.
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