Funktopus

Just finished a build of a Vitus 979, took it out for its inaugural ride, and found the seat post kept slipping under my weight.

Most Vitus 979s (and most vintage Vitus bikes in general) have a grub screw that secures the seatpost. This one doesn't, it has a traditional clamp.


The slit in the seatpost next to the clamp doesn't get narrower when the clamp is tightened to the max, which I assume means the seat tube isn't constricting at all.

​​​​​​I know that 979s officially take 25mm seatpost, which is what I'm using - but then again officially they also secure the post with a grub screw, which this one doesn't. So it could be a case of trying a 25.4mm seatpost - but I don't have one lying around and I'm reluctant to buy one before I've ruled out this being a clamp issue.

What should I try next? I could try adding more washers to the clamp bolt in order to see if it gives more of a squeeze. I don't have any in the right size hanging around, but I could get some easily enough.

Any and all wisdom thankfully appreciated!

Random Tandem

As an easy way to test if a slightly larger seatpost would solve the problem, you could make a shim from a piece of aluminum from a beer can. I often due this if I have a seatpost that seems just a little too small to get tight.

Will

Funktopus

Thanks, I'll give it a go.

However, I just found this on ebay, the frame and clamp is identical and the post is listed as a 25mm: https://www.ebay.de/itm/114334791983

So might be that sizing is a red herring.

SurferRosa

Sometimes, it's the wrong bolt/nut for the application, and it bottoms out on itself, preventing it to tighten enough for the seatpost.

Funktopus

I think this is it. There was no room for a shim jn there, it's snug as a bug.

How could I figure out the right nut and bolt combo?

smontanaro 

Maybe the little washer on the bolt half is missing?

If it has bottomed out, measure from shoulder-to shoulder. That should give you the maximum length. Find a shorter seat clamp bolt.

Funktopus

So the plot thickens. It turns out that the bolt nut doesn't have a washer, but also appears to be designed that way.

It has a wedge protruding from it that looks like it's designed to stop it from rotating when aligned with a notch. I lined it up with the notch and it did stop the bolt nut half from rotating, and allowed a tighter fit, but still not tight enough to stop the seatpost from slipping.

The bolt nut also can't be removed, even with a tap from the hammer it doesn't want to come out of the frame. So a bit of a conundrum.

Miele Man

When you tighten up the bolt look between the ears to see if the ends of the female and male parts are touching. I've had the odd set that did and I just cut a it off the end of the female part.

Cheers

Random Tandem

Can you fit another washer or two on the nut side, at least just for testing? From your first post I understood that the bolt is tightening some, but not enough to hold the seatpost when you ride - right? If so, it is either the post is too small (not likely if there is no way to get even a small shim in) or the bolt is not tightening (with no seatpost, you should see the gap close, or the bolt is the problem). If the problem is the bolt adding washers at the nut side (where it looks like you already have one washer) should increase the clamping force.

-Will

FBOATSB

I'm curious to know how a seized up bolt that won't come out is even going to tighten up properly. I would be afraid of doing damage to the frame. Please address that issue. Nice, new seat clamp bolts can be easily had. IMO

xiaoman1 

That's the first thing I would check...if the slit in the clamp stays the same when the binder bolt is tightened all the way then it is bottoming out. You may need a short binder bolt.
Best, Ben

ryansu

amazon sells seat post binder botls I had this issue -bolt bottoming out - and ordered the next size down which solved the problem

masi61

Is the threaded ear on the frame that the binder bolt bolts to have an insert or does the threading just go into the metal of the lug itself? If the threaded hole is getting hard to tighten the binder bolt into, could you clean the (metric) threads by chasing the threaded hole with the correct metric tap and some cutting oil?

SurferRosa

Check with your lbs, too. The big one here (Gregg's Green Lake Cycle) has chromoly ones in two different sizes (the longer one usually for use with a cable hanger) for like $2.50/ea.

Funktopus

I confused the nut and bolt in an earlier post. There's a washer on the bolt/male side, but not on the nut/female side. I can't get the nut out for some reason, but if I were to find a longer nut would that have the same effect?

Funktopus

The nut appears to go into the other collar. I'm thinking that a longer bolt may be what's needed, as I can't get the nut out. More threads mean more pull? I'll admit that I'm not sure if that makes mechanical sense.
​​​​​​

Funktopus

This is interesting. Neither ear is threaded, there's a long nut that goes into one ear and a bolt that goes into that nut. The bolt doesn't go as far into the nut as it could. I'm thinking a longer nut might help, but I may wring about that.

FBOATSB

You need a shorter one. The one you have is bottoming out against the shoulder of the male half. You really need a new binder bolt; both halves. Looks like there are corrosion / grunge issues going on in your photo. Remove old, clean, inspect, lubricate, replace.

FBOATSB

Random Tandem

The easiest way to clear this us is for you to post of photo of the part that you can remove. If you can add washers on either side it will increase clamping force (it effectively makes the clamped space wider). If you cannot add washers, you need to reduce the length of the shoulder part of what you can remove. If it is the nut (the female part), getting a shorter nut would work (and if you cannot find a shorter one you may be able to shorten the nut with a grinder). If the only thing you can get out is the bolt (the male side), you either need to add washes or find a bolt with the same thread and a shorter unthreaded shoulder.

I also note that on many bolts for this location one side has a key to prevent it from turning (a little protrusion that fits into a notch in the clamp), perhaps that key has become jammed into the clamp (I have had this happen when they were put in the wrong side). All of these potential complications is why I would try to see if you can get things working with either shims or washers, then at least you know that the post and clamp are going to work, while you try to determine what parts you need to replace.

-Will

Funktopus

I agree, the issue I face with that is that I haven't been able to get the female half out. It nearly gets there, but gets stuck at this point.



I was thinking the longer male half might be a way of preventing an early bottom-out if the female half really is unmovable.

I'll try again tomorrow, I'm not sure why it's not coming completely out. Might be that some grease can coax it out all the way.

Funktopus

Amazing, thank you. Here's a photo of the piece I can remove:


The circled bolt and washer are the what came with the vitus.. The other bolt came from a Reynolds frame I bought for spares. The reynolds bolt actually holds the clamp firmer than the Vitus bolt, but not firm enough.

The key is on the female side, and can clear the frame. It's a mystery as to why the female side can't get free.



​​So it sounds like my best move is to get some washers, as I'm thinking finding a bolt with a shorter unthreaded shoulder is going to be challenging.

madpogue 

The shank of the nut must be bent, if it doesn't slide out. That also may be preventing the bolt from threading all the way in. I think you need to figure out a way to get the nut out.

xiaoman1 

It could be that the key on the bolt is now slightly tweaked into the collar, because of the overtightening of the bolts...try using a flat punch to gently tap it out while twisting the allen wrench..
Do not try to pry it out...it looks like you have already been wrenching pretty hard on it so be careful not to crack the collar.
BTW the collar on the other bolt looks a tad shorter on my monitor, if that's the case that's why it "almost" tightens the post.
GL, Ben

Miele Man

It looks to me as if the ear on t he seatstay that the female part of binder fits into, is damaged. It's also possible that if the male part was tightened such that the shoulder of the male bolt rested tight against the female part, that the hollow end of the female part has been mushroomed enough to prevent easy extraction fro the ear.

When the male part is tightened to the female part you want some space between the male shoulder and the hollow female section. Otherwise you'll not be able to tighten the bolt enough to secure the seatpost.

Cheers