|   seatpost length on my xce | piggy
Mar 12, 2003 2:01 PM | | I am patiently waiting for my 19.5 xce. I currently have a thomson 27.2 post on my hardtail. It is 330 in length. Will this be long enough for my new frame. I have about a 32 inseam.
Thanks |
| Do the math... | Tscheezy
Mar 12, 2003 2:31 PM | | Measure the distance from the center of the bb to the top of your post (or saddle rails) on your old bike. The XCE will be 16" center of bb to center of tt on the large. The seat post needs to extend AT LEASTE to the bottom of the top tube for proper insertion. The seat post is officially 13" long (330mm- is that overall length or the distance to the min insertion mark?), the bb to tt distance is 16", giving 29". That seems to be cutting it close- is your saddle 3" high?. Take some measurements and see if it will work. I have the same inseam, the same size XCE, and I use a 410mm post just to be safe.
tscheezy |
| Do the math... | piggy
Mar 12, 2003 2:39 PM | | This is what I get for buying it on sale
29.99 to be exact at supergo |
| Cripes, that is a great price... | Tscheezy
Mar 12, 2003 2:55 PM | | I'll pull mine later and tell you how much insertion I have. It may still work.
tscheezy |
| Cripes, that is a great price... | piggy
Mar 12, 2003 3:18 PM | | Well I have time because the frame is in transit still |
| Shouldn't the crank length be added also? | wfl3
Mar 12, 2003 3:00 PM | | Since the full inseam extension will be at the bottom of the pedal stroke and not at the bb, this should add roughly 3" more to the equation. I think it will still be close. |
| Shouldn't the crank length be added also? | WarrGuru
Mar 12, 2003 3:07 PM | | He's comparing 2 bikes....so if they both have the same length crank arms.....they can be left out of the equation. At least that's the way I read it. |
| measurements & questions | loop
Mar 12, 2003 4:03 PM | | I have a 19.5" XCE with a 330 length Thomson post. Inseam is around 34". I have about 4.5" of post inserted in the frame. This puts the bottom edge of the post just below the top of the TT. About 5.5" of insertion would put it to the bottom of the TT. Min insertion line on the post is about 2.5", so I have about 2" over and above the min insertion of the post in the frame.
Question for Tscheezy - why do you say that the post needs to be inserted as far as the bottom of the TT? I have not heard this before. I thought I was OK by having plenty of margin on the post's min insertion point. |
| My 2 cents | Duckman
Mar 12, 2003 4:44 PM | | Depends on the bike of course, but on some bikes(like my 2 nrs bikes)the tubing is super thin, and the junction of the tt and st is just above the rear suspension pivot arm mnts. This to me is an area of what can be a source of constant and extreme loads if ridden the way the bikes designed to be, and I considered the seat post part of the frame "system" for best results in frame flex and long term durability. Ideally tho, I "like" it to extend past the tt and thru the relatively weak section of the st to be closer or overlap that big long gusset thats welded to the front of the st and the pivot arms mnt at tht top of, and the btm of the shock mnts too. Meaning the section shown between the welds of the tt and mnt below it about 3"s. That big gusset runs along ways down from there. This is why i like my 410mm thomson or maybe a 380mm extralite 30.8-9s instead of my 350mmx27.2 and shim combo with a carbon alien post on the other. Maybe i'm too anal, but ive seen too many frames break over the years.
 |
| Here is the update: | Tscheezy
Mar 12, 2003 5:51 PM | | First, because of the long seat tube extension on the Turners, Dave recomends that the seat post overlap with the juncture of the top tube and seat tube just to be safe. This came up when someone was asking about their RFX a while back. The 2.5" min insert the Thomson recommends is for the integrity of the seat post, not the frame. The frame is supposed to enjoy about 4.5" of insertion, so you have to err on the side of caution and go with Dave's recommendation. This is an extremely conservative recommendation, I'm sure, to go with the rest of the "built like a brick sh!thouse" school of thought.
Here is a pic of my bike showing where the lengths fall out. I have about 7.5" of post showing, that puts 8.5" in the bike. A 330 (13") post would put 5.5" into the bike for me, as loop also said (though his inseam is different):
.jpg)
Note that the 410 extends well below the tt, but if I were on a 330, it would just bisect the middle of the tt (I pulled the post out and measured this stuff). That is assuming it was me on the bike, with my (approximate) 32" inseam. wfl3 was right earlier that my "math" didn't make much sense when I related it back to inseam (not sure what I was thinking there either), but it turned out to be a perfect predictor nonetheless.
I would say a lighter rider like Barny could easily get away with the amount of insertion the 330 would give in this example, I'd feel ok about it even at my weight (maybe), but someone over 200# might want to give their frame every chance at survival possible ;^P
tscheezy |
| well | piggy
Mar 13, 2003 8:59 AM | | Considering I just spent 1200 on the frame I would be an idiot to risk it and run a short seatpost to save 50 bucks. Anybody want a 27.2 330 post? |
| Sure | Miles
Mar 13, 2003 9:29 AM | | Let me know by e-mail what you're asking, and I'm sure we can work something out between us soon to be Turner riders.
Miles |
| what is your email? | piggy
Mar 13, 2003 11:14 AM | | |
| Whoops | Miles
Mar 14, 2003 5:07 AM | | Sorry about that, I had entered it in the e-mail field before but I didn't see it either. Anyway it is miles_ericson at hotmail.com, but with an @ sign and no spaces around it of course (some people seem paranoid about posting their e-mail address in an easy to copy form, so I figured I'd follow suit).
Miles |
| |
