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Ok to have seat post all the way down (P3)?
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I just purchased a new bike (Cervelo P3) and when attempting to re-create the fit from my previous bike (professionally fit) I run out of room with the seat post. With the seat post all the way down, my seat post stack is off by 1 cm. I raised it up 2 cm (so now 3 cm higher than previously fit bike) to make sure there was a little wiggle room on the bottom.

My main question is : is it ok to have the seat post all the way down? If I hit a bump/ pothole/ railroad track with the post all the way down could I damage my frame?

I could always cut the seat post, but want to avoid that if possible. With my luck it would fray at the base and get stuck in the seat tube over time.
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Re: Ok to have seat post all the way down (P3)? [UMDRunner] [ In reply to ]
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UMDRunner wrote:
I just purchased a new bike (Cervelo P3) and when attempting to re-create the fit from my previous bike (professionally fit) I run out of room with the seat post. With the seat post all the way down, my seat post stack is off by 1 cm. I raised it up 2 cm (so now 3 cm higher than previously fit bike) to make sure there was a little wiggle room on the bottom.

My main question is : is it ok to have the seat post all the way down? If I hit a bump/ pothole/ railroad track with the post all the way down could I damage my frame?

I could always cut the seat post, but want to avoid that if possible. With my luck it would fray at the base and get stuck in the seat tube over time.

so you've got a new bike and you are still 10mm to high in the seat....
do you have the right size frame? I think not.
I know ST is all about stack & reach, but if you can't get your seat in the right position, then all the front end numbers don't mean a can of beans
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Re: Ok to have seat post all the way down (P3)? [Avago] [ In reply to ]
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Not necessarily true. I got a new S3 and a new P3 this year (the brand new black and white one), and the seat posts had to be cut on both. The shop did it during the fitting, so all risk was on them. They didn't seem freaked out at all about it.

Possibly Cervelo used one manufacturing length for all the seat posts of the same type? Either way, don't sweat it - have it cut.
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Re: Ok to have seat post all the way down (P3)? [benfoolery] [ In reply to ]
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IIRC this is it, they only make one Pseries seat post and it needs to be cut.

Maurice
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Re: Ok to have seat post all the way down (P3)? [UMDRunner] [ In reply to ]
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I damaged an S5 frame this way. I bought it used and inspected it on arrival. It was fine. When I put the saddle in and got the bike set up, I was amazed to find that the saddle height was absolutely spot on where I needed it. One less thing to do to build it up.

A year later, I decided to sell it. When the buyer was looking it over, we discovered that the bottom of the seat tube had punched a hole in the rear wheel cutout of the frame. Despite assurances from Cervelo that it wasn't going to make the frame dangerous, I had to offer the buyer a substantial discount.

Trimming a seatpost doesn't begin to approach being rocket science. If you can't handle it, your shop can do it in about 2 minutes.
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Re: Ok to have seat post all the way down (P3)? [UMDRunner] [ In reply to ]
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So with the seat post inserted all the way down, with none of the seatpost sticking up above the seat collar it is still too high? That is a wrong sized bike

OR Is it sticking up because the bottom of the post is hitting the wheel cut out? It's OK to cut a seatpost.


Rodney
TrainingPeaks | Altra Running | RAD Roller
http://www.goinglong.ca
Last edited by: rbuike: Feb 8, 15 17:59
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Re: Ok to have seat post all the way down (P3)? [rbuike] [ In reply to ]
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If cutting the seatpost will fix your problem cut it. Almost every womens roadbike I sold last year i had to cut the post, they spec one length of post, mens and womens and we cut to fit.


Jim

**Note above poster works for a retailer selling bikes and related gear*
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Re: Ok to have seat post all the way down (P3)? [Jim] [ In reply to ]
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Jim wrote:
If cutting the seatpost will fix your problem cut it. Almost every womens roadbike I sold last year i had to cut the post, they spec one length of post, mens and womens and we cut to fit.

I have cut EVERY seat post I have bought since 1991. I have been riding carbon bikes since 1991 (Kestrel 4000) and the seat posts are always too long for my 68 cm saddle height without hitting the cut out...well other than my 1995 softride.
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Re: Ok to have seat post all the way down (P3)? [rbuike] [ In reply to ]
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I can almost guarantee the bike is not too big for me. All my previous bikes have been 55-56cm (ideally 55cm). This bike is 54cm. With limited seat tube space secondary to a relatively high wheel cutout, I feel like the seat tube doesn't have a lot of room to go down. I'm guessing cervelo would rather give too much seat tube than not enough. I still have a very healthy amount of seat post available even when the seat post is all the way down. Check out the below photo, that is my bike with the seat post all the way down.

Back to my question. Is it bad to ride with the seat post all the way down?


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Re: Ok to have seat post all the way down (P3)? [UMDRunner] [ In reply to ]
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Yes, it can be. Also it's bad to ride with your seat too high. Cut it. Use a hacksaw and tape off your cut line. Measure twice, cut once. Or get a shop to do it.
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Re: Ok to have seat post all the way down (P3)? [UMDRunner] [ In reply to ]
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No it is not bad to cut the seatpost. Just make sure you don't cut off too much. Just the minimum necessary to reach the height you want.
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Re: Ok to have seat post all the way down (P3)? [UMDRunner] [ In reply to ]
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Cut it cut it now....before it slams into the cutout if it slips and wrecks your frame
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Re: Ok to have seat post all the way down (P3)? [UMDRunner] [ In reply to ]
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Just go ahead and cut it. That's what we did to my wife's 48cm P3. The reach is about perfect, the stack as well, but to get the seat low enough, we had to cut the post. Took all of 5 minutes, including measuring, re-measuring, masking tape, cutting, filling the edges to get them smooth and putting it back in the frame...

"Suddenly the thought struck me. My floor is someone elses ceiling"-Nils Ferlin
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Re: Ok to have seat post all the way down (P3)? [UMDRunner] [ In reply to ]
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I have a P3, needed to lower the seat about an inch, and the seat post was bottoming out in the frame. So I cut it, and still have plenty of room to go up down if/when needed. This was 3/4 years ago.
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Re: Ok to have seat post all the way down (P3)? [UMDRunner] [ In reply to ]
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UMDRunner wrote:
I can almost guarantee the bike is not too big for me.

You're right, based on the headset spacers, upturned stem and arm rest spacers, I would guess you're frame is too small.

But anyway, just cut the bottom off the seat post so it doesn't hit the inside of the frame. Carbon fibre won't fray, it's actually carbon fibre cloth mixed with resin to make it a solid structure, pretty much like a metal structure. Cutting the post won't cause it to get stuck in the frame. I have cut posts on a few frames just like the other guys other, without a problem. Carbon fibre structures are not some voodoo magic, as long as there's enough post down in the frame it will be fine.
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Re: Ok to have seat post all the way down (P3)? [nickag] [ In reply to ]
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Same thing here. Seatpost is too long. The saddle is about 2 cm too high and I cannot move the seatpost further in because it collides with the wheel cutout. So will need to cut off roughly 3-5 cm.

Considering to replace the stem with a 17 deg stem to get the aerobar lower. The dropped BB on the 2019 P3 (compared to my 2012 P3) and the higher position of the armrests with the new bar plays havoc with the position I am used to. Can anyone tell me how much a 17 deg stem lowers the bar? I have a 90 mm stem installed. Given the shorter reach compared to my 2012 P3 I might even consider a 100mm stem.

Thanks.
Last edited by: Feehliks: Jun 7, 20 5:37
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Re: Ok to have seat post all the way down (P3)? [Feehliks] [ In reply to ]
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length of stem x sin (17) will give you the amount of drop versus a zero degree stem assuming your head tube angle is around 73 degrees (which most are....usually somewhere between 73 and 71 degrees unless you are riding a beach cruiser).
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Re: Ok to have seat post all the way down (P3)? [Feehliks] [ In reply to ]
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It looks like you have a -6° stem on there right now. I'm assuming a head tube angle of 72°

Going to a 90mm -17 will drop you 13mm and lengthen 2mm

Going to a 100mm -17 will drop you 12.5mm and lengthen 11.8mm
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Re: Ok to have seat post all the way down (P3)? [jaretj] [ In reply to ]
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Thanks! 1+ cm is very helpful (angle is 72.5)!
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Re: Ok to have seat post all the way down (P3)? [Feehliks] [ In reply to ]
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Recalculated for head tube angle of 72.5°

Going to a 90mm -17 will drop you 12.5mm and lengthen 1.6mm

Going to a 100mm -17 will drop you 11.8mm and lengthen 11.6mm
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Re: Ok to have seat post all the way down (P3)? [jaretj] [ In reply to ]
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Thanks! Might actually switch to a 3T bar to get this lower!
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