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-   -   Replace bolt seatpost clamp with QR one? (https://www.bikeforums.net/bicycle-mechanics/1128628-replace-bolt-seatpost-clamp-qr-one.html)

taz777 11-21-17 07:50 AM

Replace bolt seatpost clamp with QR one?
 
Apologies if this is considered a dumb question, but I just want to make sure.

The seatpost clamp on my bike is a bit 'roughed up' and could do with replacing. It's a bolt type clamp. The diameter of the seat tube is 34.9mm. Would I be able to replace this seatpost clamp with a 34.9mm QR clamp as a straight swap? Or would I have to buy another bolt-type clamp?

The reason behind my question: I want to colour coordinate some of the bits on my bike and have seen a Hope QR clamp that comes in numerous sizes and colours and has very good reviews.

dsbrantjr 11-21-17 07:56 AM

A QR clamp will make your seat and post easier/quicker for a thief to steal. Or for you to remove to avoid theft.

taz777 11-21-17 08:03 AM


Originally Posted by dsbrantjr (Post 20006677)
A QR clamp will make your seat and post easier/quicker for a thief to steal. Or for you to remove to avoid theft.

That's an interesting view. I hadn't thought of that. However, on a purely technical level, is it just 'plug and play'?

leob1 11-21-17 08:18 AM

As long as it fits, you shouldn't have any problems.

Sy Reene 11-21-17 08:55 AM

Isn't the question as to how you gauge the correct amount of torque that a QR clamp is applying to the seatpost? Not an issue I guess if you have a pretty solid steel/alloy post, but if eg. carbon, is there a risk of crushing the saddle post?

taz777 11-21-17 09:08 AM


Originally Posted by Sy Reene (Post 20006821)
Isn't the question as to how you gauge the correct amount of torque that a QR clamp is applying to the seatpost? Not an issue I guess if you have a pretty solid steel/alloy post, but if eg. carbon, is there a risk of crushing the saddle post?

The frame and seatpost is metal, not carbon. The existing bolt clamp has 5Nm written on it. I'm assuming that QR seatposts would be awfully hard to close if too much pressure is being applied to the seat tube/seatpost.

I'm actually more worried about the seatpost slipping!

Colnago Mixte 11-21-17 09:18 AM

I think QR seatpost clamps definitely slip sometimes. When I use one, I'm constantly raising the seat higher. So either I'm getting taller as I ride, or the thing is slipping, one or the other.

The biggest reason I won't use them is because I hate the inside of my leg hitting the damned QR lever with every other pedal stroke. I'm pretty sure I've gotten bruises doing that, but I know I can still feel the spot the next day. Me no likey.

Besides, how long does it take to grab an allen wrench and loosen the bolt that way? A few seconds more, tops. If you're racing in the penultimate stage of the Tour de France and shooting for a good GC finish, those seconds might matter, but for the rest of us, not so much.

Can't comment on the color coordination issue, that's purely an individual choice.

fietsbob 11-21-17 10:23 AM

some seat post lugs are half threaded, to use a common bolt, some are made to use a special bike seatpost binder bolt ..

Of Course, specific, OP didn't say.. Is the binder bolt part of a separate band, or integrated?

NB: there have been thin 5mm and thick 8 mm seat post QR 'skewers' .



I had to cure a Brompton seat post slipping, I've written about that before..


good luck.





.....

Sy Reene 11-21-17 10:42 AM


Originally Posted by taz777 (Post 20006860)
The frame and seatpost is metal, not carbon. The existing bolt clamp has 5Nm written on it. I'm assuming that QR seatposts would be awfully hard to close if too much pressure is being applied to the seat tube/seatpost.

I'm actually more worried about the seatpost slipping!

To help reduce likelihood of slipping, consider using some assembly paste (eg. Park SAC-1).. though if you're removing and substituting the post a lot, this is obviously a pain, and could lead to obvious scratching of the post if one's not careful (though hopefully below the visible area of the post).

taz777 11-21-17 11:13 AM

I have some assembly paste, two variants: one for carbon and one for non-carbon. I'm not sure what the difference is specifically. I'll check what the bike shop put on the seatpost as it's a new bike. The bike itself is unmarked but the seatpost collar is scratched up quite a bit. It's going to a bike service company later this week who will check the bike over as I've found that online bike shops leave a lot to be desired in terms of bike prep before boxing up the bike and sending it over.

maddog34 11-22-17 11:23 AM


Originally Posted by taz777 (Post 20007171)
I have some assembly paste, two variants: one for carbon and one for non-carbon. I'm not sure what the difference is specifically. I'll check what the bike shop put on the seatpost as it's a new bike. The bike itself is unmarked but the seatpost collar is scratched up quite a bit. It's going to a bike service company later this week who will check the bike over as I've found that online bike shops leave a lot to be desired in terms of bike prep before boxing up the bike and sending it over.

two types of assy. paste....

clamp is scratched up, but bike is new?

sending bike to a shop, but has two types of assy. paste on hand....

online "bike shops" don't uncrate new bikes, then crate them back up.

"I'm assuming that QR seatposts would be awfully hard to close if too much pressure is being applied to the seat tube/seatpost."
seat posts don't "close", and certainly aren't "QR".

red flags waving.... please put the tools down, and step away from the bicycle.

taz777 11-22-17 12:25 PM

@maddog34: here in the UK the online bike shops assemble the bikes, turn the handlebar by 90 degrees and then box them up for shipping. When the customer gets the bike they just have to rotate the handlebar and fit the pedals.

The bike is new but the collar is scratched up - it's as if the hex wrench slipped a couple of times, and as it's black the scratches show easily. I tend to detail all of my bikes and like them looking like new.

It's going to a bike service workshop to have a brake conversion done - the mechanical disc brakes are being replaced with Shimano M7000 SLX hydraulic brakes and RT86 rotors, plus a proper tune-up and adjustment of the bike as online bike shops here perform a very poor assembly of bikes. I've always sent bikes that I've ordered online to this particular bike workshop to have them checked over, aligned and adjusted as required. They have equipment that I don't posses for truing wheels and checking rear mech hanger alignment. The bike workshop I use collect and return the bikes so it's very convenient.

And, yes, I have two different assembly pastes and a host of new/replacement parts to fit to the bike, like a new saddle, mudguards, grips, lights, etc., when it comes back from the workshop. Oh, and a new seatpost clamp!

Apologies for my typo earlier, I meant QR clamps, obviously not QR seatposts! :lol:

Troul 11-22-17 02:58 PM

Being my bicycle came QR already, it did have some slipping issues. Was at a friends place where there relative left behind some poligrip... applied some of the poligrip to the post jfs&g. Never had an issue with it dropping. Also note* I've since had the seat post up/down & out at random times & the post still remains at height from that install.

maddog34 11-22-17 03:43 PM


Originally Posted by Troul (Post 20009896)
Being my bicycle came QR already, it did have some slipping issues. Was at a friends place where there relative left behind some poligrip... applied some of the poligrip to the post jfs&g. Never had an issue with it dropping. Also note* I've since had the seat post up/down & out at random times & the post still remains at height from that install.

which will explain why your seat post keeps showing up in a glass full of water next to your bed!


sorry... just had to share that thought... :-D

Troul 11-22-17 06:19 PM

might explain all the old people with canes shuffling behind as I ride?

sweeks 11-22-17 06:42 PM


Originally Posted by taz777 (Post 20006690)
However, on a purely technical level, is it just 'plug and play'?

A clamp is a clamp. As long as adequate pressure can be developed, they are equivalent.
FWIW, I replaced the Q-R on my Trek mountain bike with a bolt years ago. I don't remember why, except I found a nice titanium seatpost clamp bolt and went for it! :love:
(Saved about a gram! :D)
Steve


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