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Old 2017-02-03, 08:32 PM   #1
Cousin Itt
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Seat post extended past seat tube question

Is there any problem or concern with having a seatpost extend past the end of the seat tube as long as it does not touch the tire?
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Old 2017-02-03, 08:42 PM   #2
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No.
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Old 2017-02-03, 08:57 PM   #3
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If you got lots of mud on the tyre it could foul I suppose. But I rode mine for months like that.
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Old 2017-02-03, 10:11 PM   #4
Cousin Itt
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Excellent! I don't ride in the mud so that shouldn't be an issue at all. Thank you both for the replies!
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Old 2017-03-03, 06:34 AM   #5
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If your clamp slipped and the post could drop down far enough to touch the tire, you could have a rather sudden UPD along with a wrecked tire.

I cut a short piece of PVC pipe to slide over the post (between the clamp and the seat) so the post can not go any lower than the lowest position I use.
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Old 2017-03-03, 12:26 PM   #6
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Originally Posted by Vital Wombat View Post
If your clamp slipped and the post could drop down far enough to touch the tire, you could have a rather sudden UPD along with a wrecked tire.
In theory that's an issue however high the seatpost is.

Seatpost on my son's unicycle sticks out of the bottom of the seattube and is about as low as it can get without hitting the tyre - I preferred not to cut down the post as he will get bigger and need it raising higher.
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Old 2017-03-03, 12:44 PM   #7
Eric aus Chemnitz
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Quote:
Originally Posted by Vital Wombat View Post
If your clamp slipped and the post could drop down far enough to touch the tire, you could have a rather sudden UPD along with a wrecked tire.
Before the post drops it'll start to turn and then you recognize it has to be re tightened.
I've never heard of a dropping seat post. Is this really an issue?
I mean, why letting a seat post become so loose that it can even drop and the preventing it from hitting the tire?
Why not tightening the seat post clamp properly and so preventing it from coming loose?
Since I use double bolt clamps on all of my unicycles I never ever had to re tighten a seat post clamp or even had a turning seat post.
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Old 2017-03-03, 09:10 PM   #8
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Quote:
Originally Posted by Eric aus Chemnitz View Post
Since I use double bolt clamps on all of my unicycles I never ever had to re tighten a seat post clamp or even had a turning seat post.
I'm actually glad you bring this up. So the double clamp seemed to be a good answer to more holding power, however, after trying a few different clamps over the years, I have come to the conclusion that double bolts do indeed hold better, but a pivot bolt adds a LOT more holding power. Essentially this allows the bolt to have no sheer forces on it by tightening it. If you drill straight into the clamp, the bolt essentially bends as you tighten it more and more. Salsa lip-lock and thompson seat post clamps are good examples of single bolt clamps that have just as much, if not more, holding power than a double bolt clamp. If you want the absolute most grab, with the least amount of wrenching down, impact makes fantastic clamps that are double bolt AND have 2 separate pivot bolts. I think these are the best of the best right now, and wish I had them on more of my wheels. I apologize for the return of my MS paint skills, but I think it illustrates the point alright. Basically that cylinder (the circle on the right side looking from the top) is the only part that's threaded. Anyway, if you ever have trouble getting your seatpost tight enough, now you know what to look for. : )
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Old 2017-03-03, 10:01 PM   #9
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Quote:
Originally Posted by juggleaddict View Post
I'm actually glad you bring this up. So the double clamp seemed to be a good answer to more holding power, however, after trying a few different clamps over the years, I have come to the conclusion that double bolts do indeed hold better, but a pivot bolt adds a LOT more holding power. Essentially this allows the bolt to have no sheer forces on it by tightening it. If you drill straight into the clamp, the bolt essentially bends as you tighten it more and more. Salsa lip-lock and thompson seat post clamps are good examples of single bolt clamps that have just as much, if not more, holding power than a double bolt clamp. If you want the absolute most grab, with the least amount of wrenching down, impact makes fantastic clamps that are double bolt AND have 2 separate pivot bolts. I think these are the best of the best right now, and wish I had them on more of my wheels. I apologize for the return of my MS paint skills, but I think it illustrates the point alright. Basically that cylinder (the circle on the right side looking from the top) is the only part that's threaded. Anyway, if you ever have trouble getting your seatpost tight enough, now you know what to look for. : )
I never thought of that, but it makes sense. Your diagram is actually pretty good, especially using MS paint, and it illustrates your point very well. As cheap as a seatpost clamp is, a pivot bolt sounds like a no-brainer. I usually use double-bolt seatpost clamps that work pretty well, but even with those the saddle may twist on a particularly bad UPD. I'll definitely be looking for pivot bolts when I buy my next seatpost clamp. Thanks!
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Old 2017-03-04, 10:39 AM   #10
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Quote:
Originally Posted by Bradford View Post
I'll definitely be looking for pivot bolts when I buy my next seatpost clamp. Thanks!
There you go, they're not even more expensive than the other brands:
http://www.unicycle.com/impact-doubl...t-clamp-black/
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Old 2017-03-04, 12:49 PM   #11
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Quote:
Originally Posted by Eric aus Chemnitz View Post
Before the post drops it'll start to turn and then you recognize it has to be re tightened.
I've never heard of a dropping seat post. Is this really an issue?
I mean, why letting a seat post become so loose that it can even drop and the preventing it from hitting the tire?
Why not tightening the seat post clamp properly and so preventing it from coming loose?
Since I use double bolt clamps on all of my unicycles I never ever had to re tighten a seat post clamp or even had a turning seat post.
I've had clamp bolts fail (snapped, not worked loose) on bikes a few times.
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Old 2017-03-04, 04:19 PM   #12
Bradford
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Originally Posted by pierrox View Post
There you go, they're not even more expensive than the other brands:
http://www.unicycle.com/impact-doubl...t-clamp-black/
Does that comparison include the cost of shipping? Even still, it's one of the cheapest parts you can buy for a unicycle and totally worth it (and I think it looks cool, too!)
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Old 2017-03-04, 08:47 PM   #13
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Originally Posted by Vital Wombat View Post
I've had clamp bolts fail (snapped, not worked loose) on bikes a few times.
But then that would cause a problem anyway, unless the seatpost was so short that it couldn't protrude even at its lowest? Which unless you had a very tall frame tube would be almost anyone who is taller than me.
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Old 2017-03-04, 10:27 PM   #14
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But then that would cause a problem anyway, unless the seatpost was so short that it couldn't protrude even at its lowest? Which unless you had a very tall frame tube would be almost anyone who is taller than me.
Yes, which is why I added a piece of PVC pipe to physically stop it dropping. It is dirt cheap, and only took me 2 minutes.

Belts and braces.
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