Fredo76

I bought a "CR MO" seatpost binder bolt from ebay (mea culpa). When I installed it, it held for my first ride, but after adjusting it once the bolt bound up, gouging up the threads on the bolt end, and my seat lug slot on the other. Getting it out took more force than I usually put on 5mm Allen wrenches, and no wonder:



thread damage



bolt malfunction?

Does anyone have a source for this type of binder bolt that is known to be good? I would need one maybe 18-20 mm inside distance when totally closed/bottomed out, for a 22 mm outside distance on the seat lug tabs. There must have been some slag or something in the nut end to have chewed up the bolt. I'm lucky I didn't round out the hex sides in either end trying to get it out.

Thanks for any insight, or a quality source.

smd4

Doesn’t *look* like you used any grease on the threads…

dedhed

https://problemsolversbike.com/products/binder-bolts

​​​​​​https://framebuildersupply.com/produ...BoC7vcQAvD_BwE

tiger1964 

I keep asking this question, and would really like to know -- stated size of seat post bolt... is that the minimum grip, or the maximum, or...???

dedhed

​​​​​​https://problemsolversbike.com/pages/contact

FBinNY 

Your problem is that it was top short, and only engaged 2 threads when tight.

Select length carefully, being sure to engage at least 6 threads when tight and you'll be fine.

Also, it's best practice to turn the nut rather than the bolt.

Crankycrank

I've used a few different brands, Campy, Sugino, Problem Solvers, etc. and never had any quality or strength issues as long as they were the correct length and not over torqued. Either you were unlucky and got a dud or as mentioned above, it was the wrong length. Any chance the binder was too long for your seat tube and the bolt end was forced into the female hex end which is not large enough for the bolt to pass through?

Andrew R Stewart 

"Perfect Storm"

As others have pointed out: too short a threaded section resulting in too few threads of overlap. No lube on threads. And not yet mentioned is that the lug ear slot that became deformed is a poor anti rotation attempt in many cases and this is a big reason why most of these bolt/nut combos have a hex wrench fitting on both ends. Using two hex wrenches will eliminate the nut from rotating far better then a tiny tab in a coarsely formed slot.

I'll further add that bolt "strength" (most will understand it as tensile strength) is really not the issue here. The bolt shaft didn't fracture, the bolt didn't bend (although bent bolts are very common when the lug ears are deformed from previous over tightening and/or an undersized post is used). If you do want max strength get a M8 bolt and nut, the cool hex headed bike binder bolts are nearly always M6. Andy

alcjphil

My take is the opposite. The bolt is too long resulting in the end of the bolt bottoming out in the nut threads. A couple of extra washers on the bolt end would correct the problem

Fredo76

No grease is my bad, and noted.

Always using two wrenches is a good idea, too. I believe the slot was wrecked by loosening attempts, not the first installation. I could be wrong about that, however.

There were 6 or 7 threads engaged, not just two, and it had not bottommed out. It was the proper size; there were a couple of threads still showing. I think I got a bad one.

Thanks for the sources, dedhed . Anyone else?

And thanks to all who replied.

alcjphil

The threads do not go all the way through the nut section. What I see is the end of the bolt being stripped when it reached the end of the threads in the nut. I would cut off the end of that bolt allowing it to thread in farther

Kontact 

These should bottom out on the shaft step rather than the threads.


Places to buy bike bolts: Bike shops.

smd4

Then cut off the bad threads and give 'er another go! (and use grease this time).

zandoval 

Thanks for the post... Looks like one of those live and learn situations.

Think I'll go check my posts now, what the heck, got nutten else ta do...

alcjphil

There should always be a couple of threads showing between those shoulders

mpetry912 

there are a bunch of ways to handle this. The best is this Richard Sachs seat pinch bolt. RS Seat Lug Bolt + Nut Assembly - Richard Sachs Cycles

I have one (on my RS) and it is ultimate.

HOWEVER here's what I would do in your situation. take the existing "nut" that you have and find an M5 metric bolt that is the right length

I think the problem is that the "cro mo" bolt (the part that stripped) had to be machined down and then turned for threads.

and just because it SAYS Cro-mo on it does not mean that it is. There was a helicopter part scandal years ago that had to do with mismarked / counterfeit bolts.

Get a high quality M5 bolt that is the right length and use that

/markp

Kontact 

I think you missed what I was responding to - if you tighten the bolt all the way into the nut side, the threads won't be damaged because the shoulder stops the threads before they get that deep.

This is separate from how they shouldn't bottom out on a bike.

Kontact 

With all respect, seat binders look like they do for a reason. The slimmer, exposed shaft of a regular bolt is more likely to scratch paint and distort the frame collar.


This is a lot of drama over an $8 part you can buy at any shop.

mpetry912 

here's the setup I have on my Masi GC, last 15 years or so, not the slightest problem, slipping or scratching

my point was that a bolt off Amazon that has "Cro-mo" on it may not be what you think it is.

this bike is over 50 years old and original paint.

/markp

FBinNY 

This too is very possible.

The solution, either way, is to use care in choosing the bolt length, and while installing.

alcjphil

I think that we have looking at this problem from opposite ends

Kontact 

This photo is somewhat illustrative of what I'm talking about. The outer flats of the two ears are no longer parallel - it looks like the right side is angled toward the rear edge. The hole-filling width of the stepped bolt keeps the ear from bending and helps tighten the part closest to the seat post more effectively.

It looks like the top your seat tube is touching, like the post is undersized or the frame stretched.


High quality Problem Solvers brand binder bolt assemblies are $7.49 and probably what you'd find in most bike shops. Why cobble this together when the right hardware is easy to find? I'd rather have questionable quality hardware of the correct dimension than the world's highest quality ill-fitting replacement.

FBinNY 

Perspective only matters when it keeps you from finding answers.

Though we started from opposite directions, we ended in the same place, and that's what counts.

mpetry912 

But life is short. we all pass from this earth. in time the sun will go super nova and contract into a white dwarf. The universe will decay into entropic heat death.

What's wrong with this seat post pinch bolt ?

/markp

FBinNY 

Non parallel ears are very common.

This is not an issue if the bolt is held and only the nut turns. If you turn the bolt when the ears aren't square, it bends back and forth with every turn, and is compromised by that process.