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I don't understand why if you are running the same length cranks you would change bb to seat height that much?.Bring the seat forward sure but why change the height?.
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More likely to sit further forward on the saddle.
I guess road bikes are set up for a variety of working postures when riding, riding in the pack, sprinting, and so the saddle height is a compromise.
Raised the seat to about two cm higher than my road bike setup. And this worked ok when using clip-ons. Now I have my TT bike I have started gently modifying one thing at a time on my bike, but more importantly is to keep the flexibility stretches going.
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BarryTas wrote:TLL, my seat was put forward as far as it can so then up 3 cms
No one measures saddle height by how much it protrudes out of the seat tube or from the ground. The reference is either to the centre point of BB axle or pedal at its lowest point. Saddle height relates to hit to heel distance and proportions within, and that's what it needs to relate to.
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Richard.L wrote:I think every time the seat moves up 1cm your saddle moves forward by .5 a cm
guessing from what the LBS told me
If you're measuring up along the post, you'd have to have a 60 deg seat tube for that to be true. On a 78 deg TT seat tube angle that rule is very wrong; the forward adjustment would be 0.2 cm.
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often TT seat heights are higher. very simply the reason being that you tend to sit further forward on the seat meaning you have a different measure point to where you sit. moving the measure point forward increases the angle and decreases the distance to the BB.
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For reference, my inseam is 81.5 cm.
I used to be suggested a distance from bb to saddle about 73 cm. But actually where do you measure it? From the back of your saddle/ nose or middle? At the end I just put the distance from saddle to ground about 97 cm. (with 172.5 mm crank arm). Any suggestion for the formula?
And for TT, it's true if you get forward quite a lot, u need to have a very high saddle position, but for training, I used to get exhausted very fast and tend to get back to the back of the saddle which result the distance from the saddle to the pedals just too high and that made it not efficient. Any advice for this also?
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Jono1006 wrote:Is it bad to have a different seat hight on your road bike compaired to your time trial bike?
Mine is 25mm higher, as the seat comes foward you need to lift it up.
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If your road saddle height is correct and your saddle set back is also correct (tip saddle to centre B/B) then your TT saddle height
will be lower by 5-6mm. The reason is simple if you lower your back angle by 20 deg you extrend your leg length accordingly.
Simply stand with knee slightly bent as per road knee angle on extention, now lean forward and note what happens to your leg length.
Given that you ride (AT) a 44 deg back angle and your TT position is agressive (AT) 20 deg, it is also worth noting that the leg angle on extention and
flextion are both greater when setting up your TT position. Running your saddle to high on either a TT or Road by bewtween 6 and 10mm will result in a 20 to 25 watt reduction is sustainable power during a 40km ITT.
Gary (AT) probikefit did my TT set up and I set my PB, he is in Brisbane
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