Was riding along yesterday when the saddle on my 1988 bike suddenly disappeared beneath me. Fortunately, I reflexively stood up on the pedals when the saddle gave way, or I might have found myself in a very uncomfortable position on top of a naked seat pillar. I pulled over without crashing and walked along the road to gather up:

1) one Brooks B17 saddle, scuffed a bit where it bounced down the road (but still in pretty good condition).
2) the upper and lower seat rail clamps of a 1988 Campagnolo aero seat post (first generation Chorus edition)
3) the failed Campagnolo bolt that normally holds the rail clamps together, and attaches the saddle to the top of the seat post. This single bolt had sheared in the middle, causing the spontaneous loss of saddle.

I found this experience particularly unnerving because it was completely unexpected. I've put thousands of miles on this older bike with no problems since purchasing it used last year on Craigslist. I had made no recent saddle adjustments. I was not carrying any unusual weight on the bike, and had not just hit any large bumps in the road. At 6' 2" and 175 pounds I'm substantially heavier than a typical bike racer, but am not at a weight extreme that would normally have me thinking about shearing or crushing bike parts. Granted the failed bolt was 22 years old and has seen a lot of miles. But I still have several practical questions about both repairing and avoiding this problem in the future?

Is this a common mode of failure for Campy (or other) one bolt seat clamp posts?

If I just get a replacement bolt, what is the strongest type that might minimize chance of similar unwanted surprise in the future? Look only for an original Campy bolt? Find another stainless steel bolt of correct length and thread? Note that the Campy seat clamp design comes with a separate concave washer to help match the head of the bolt to the curve of the saddle clamp (see diagram from 1988 Campy dealer parts catalog, part #3). This minimizes the need to find a special bolt head that matches the underside of the seat clamp. I know Campy sometimes uses special metals or forging methods for either strength or weight. I don't care about weight, but I do now care a lot about strength in this mission critical component!

Should I actually replace more than just the sheared bolt? On disassembling and inspecting the seat post I have noticed several signs of long term wear and stress on other parts. For example, the series of fine serrated ridges that extend across the curved mating surface between the top of the seat pillar (shaded in diagram) and bottom of the lower rail clamp (part #2) have worn nearly flat in some locations along the mating surface. These ridges normally help maintain the angle of the saddle adjustment (nose up or down). Because the ridges have worn with age, more shear stress is probably transmitted to the central seat rail bolt than would be true if fresh mating surfaces were doing a better job on their own helping to hold the seat angle.

Finally, I assume that only the upper seat rail clamp is supposed to have a threaded hole for the key bolt? On my parts, the upper rail clamp (part #1) is clearly threaded. Tightening the bolt works by squeezing the upper clamp tight agains a stack of parts that then includes from top to bottom: upper rail clamp (#1): saddle rails , lower rail clamp (#2) , top of seat pillar, concave washer (#3), head of bolt (#4). By inspection, the central hole in the lower rail clamp (#2) is substantially larger than the threaded hole in the middle of the upper rail clamp (#1), and will not hold the threaded bolt on its own. The bolt broke in the middle of this stack of parts, leaving one half still threaded into the upper rail clamp, and a lower half that fell completely out of the larger hole in the bottom rail clamp.

Thanks for your help and I hope not too many other people get to experience this same surprise when out riding your classic and vintage bikes!
1988CampyChorusSeatPost.png

To find the "correct" Campy bolt you'd probably pay more than it's really worth, as compared to the cost of a completely new seatpost, particularly from a retail source.

I would either:
1. Place a ISO/WTB in that thread, and hope a kind soul responds at a reasonable level, or if no luck
2. Go to your local industrial supply house and buy a high grade (edited) fastener.

And glad you had the presence of mind to avoid an uncomfortable end.

If you want a high strength bolt you don't want stainless. Stainless can't be hardened due to the low carbon content. A stainless bolt is only slightly stronger than a grade 2 steel bolt.

No pun indended?

...yet another reason I avoid 1-bolt seatposts like the plague.

SP
Bend, OR

Atleast the Brooks Saddle had enough common sense to leap away from that broken post! It could have been scared for life.....I shudder when I think about it!

In all seriousness, glad you were not hurt.

OMG! Nightmare scenario, glad you and the Brooks are OK.

Totally intended.

Happened to me on my mountain bike last year. Instinct saved me also. I rode 5 Miles home standing up or sitting on the rack.
That was the worst of it.
Most seat post are M8 x1.25 mm thread and can be replaced easily. My ME friend told me that the strongest bolt is labelled 12.9 and is rated to 175Ksi.
I don't know what those no. mean but he knows his stuff.

happened on a buddy'e mtb. we then took turns riding i back (after removing the post of course). never realized how important a seat was until then

glad you escaped injury

"I found this experience particularly unnerving because it was completely unexpected. I've put thousands of miles on this older bike with no problems since purchasing it used last year on Craigslist."

Well......unexpected? I'm sure it was but thousands of miles, 22 year-old post. I agree it's unusual but everything wears out eventually.

I think if you're feeling unnerved by it you should replace the whole post just for your own peace of mind. There are several similar posts on EBay right now - none particularly cheap though. With good reason: molto bella!

Well, what do you expect when you put a 12 pound saddle on a seat post designed for ordinary loads..........

It's a metric bolt and I'm not sure of the size, but I'm sure you can find one at your local hardware store.... Get yourself a new grade 8 replacement and that will hold up. Your typical seat post come with a 10.9 grade bolt and even a 12.9 does not compare to a grade 8.

https://www.boltdepot.com/fastener-in...ade-Chart.aspx

Thanks, I learned some metallurgy today from several people's informative responses about different types of steel. If I am reading the bolt-grade-chart correctly in your Bolt-Grad-Chart link correctly , a 12.9 grade bolt actually looks somewhat stronger than grade 8 steel (once you convert between megaPascals and pounds per square inch). I'll see what I can find in 12.9 or grade 8 bolts in my local hardware stores. I think the Campy bolt is M8 x 1 threaded with a 6 mm allen key head. According to Velobase, Campy switched to a wider diameter bolt with an 8 mm allen key head in their second generation Chorus seat posts. Shear strength varies with square of bolt diameter, so I assume they were trying to improve the strength of this component as they updated the group in later years.

Yes, the 12.9 is the best choice, but I thought you would have a tough time finding that at a local hardware store but guess what,
I went over to Lowes last night and they have them so it should be no problem finding one. Good Luck.......

Ug! Reminds me of something that happened to me while I was riding my Releigh Pro up Chapel St in New Haven, this would be about 1990.

I went over a minor bump in the road; heard and felt a loud popping sound, immediately followed by the ricochet sound of something hitting the side of the car next to me (a parked one); and felt an elevator-like sensation as my seat post slid down into the frame.

On inspection, it proved the Campy seat post bolt had broken, in half, and the right side part was totally AWOL. I was about half a block from a bike shop, so I just walked in and bought another. Everyone in the shop thought it was pretty funny (self included).

Makes ya kinda think.....the stem and brake calipers have the same single bolt retention system. Maybe it should become practice that when refurbing a 20+ year old bike to replace them before they fail?

Lots of stressed things have bolts that are more than 20 years old (autos, aircraft, engines, bridges, buiildings, etc.) - likely including the last airliner you flew on. Time alone is not the problem. I see no need to worry unless the bolt has been grossly over-torqued. This may be the case with the failed seatpost bolts.

Regarding the question posed by the original poster, I would replace the bolt with a grade 12.9 (equivalent of AN grade 8) or better bolt and never worry about it again.

over-torqued Bingo.

I replaced mine today....

I couldn't find a suitable replacement bolt at local hardware stores. Most M8 bolts in stock were 1.25 mm threaded instead of 1.0 mm fine threaded, hex head instead of allen key, or not the high strength 12.9 grade steel. I did find something that looked suitable on-line: https://www.fastenal.com/web/product...ex?sku=0142067. None of my local Fastenal stores had the part in stock however, a triple whammy from the fine thread/allen key head/12.9 grade requirement.

Fortunately I was also able to find a local bike store that had the original NOS Campagnolo seat rail bolt in their older parts collection. So for $10 I am back up an riding. I'm also ordering the Fastenal version on-line, and will carry it as a spare. Probably not necessary, and I would be delighted if I never have to use it!

This post needs to be recognized for it's hilarity. Well done.

it coulda been career ending

From left to right:
Broken Campy seat bolt,
Replacement Campy seat bolt,
Alternative M8-1.0 mm threaded allen head screw (35 mm, Grade 12.9, Zinc finish. Fastenal item # 0142067).
P1010987.jpg

The Fastenal bolt fits when tested in the 1988 Campagnolo Chorus aero seat post. It is slightly longer than necessary, so protrudes a bit further above the top of the seat rail clamp. I reinstalled the Campy NOS bolt, and am carrying the Fastenal as a backup in the tool pouch on my bike.

Always wanted to use this quote.