Just broke Kalloy Uno seat-post bolt during a ride.....
 

I'm talking about the large Allen-head bolt that helps clamp the seat to the post. I figured these things were nearly bulletproof, but that bastage just snapped in half in the middle of a ride yesterday. (Could be my fault for over torqueing it way back when).
Anyway, I'm hoping to salvage this otherwise solid 400mm post, but the very few possible options im seeing on a replacement screw, dont leave me confident they're the right one. I even hammered out a message directly to Kalloy in Taiwan, but im not expecting a response..
Not sure if someplace like Home Depot would have something suitable.
Any info/recommendations much appreciated.
PS, I already installed an old OEM post I had lying around, so the bike is running again, and then ordered a nearly identical post, but I'd still like to save this one.

if it’s a standard hex-head bolt (ie not some proprietary design), you can almost certainly find a replacement at a decent hardware store or online at, say, McMaster-Carr. I’m assuming that you were able to extract the bit left in the seatpost? Bring it along with you to match the size and thread

My guess is that the broken cap screw is an M8, but it might be an M10. Not sure what the length would be, but a guess is that it will be around 30-40 mm.

Any good hardware store or auto parts store should normally stock them. The thing to be careful about is that you get one with the appropriate strength rating.

​​​​​​If you have the broken screw cap end it may be marked. If not, you might try to locate a grade 12.9 screw. That may have compatibility issues with the alloy post.

Hopefully the manufacturer will tell you the size and grade of screw to use. If they don't, use a 12.9 or 10.9 screw and some anti seize on the screw. Oh, also maybe a torque wrench🤕

+1 DangerousDanR get a good quality bolt of the correct size and length. Plenty of cheap bolts that are not worth your time. Your average hardware store may or may not have what you need.

Make sure you use a torque wrench when installing the new bolts and don't overtorque things. I am pretty sick and tired of the classic "my hands are tuned or calibrated" B.S. Certainly yes after doing something a while your hand will get used to it but a torque wrench will ensure you get it accurate or at least closer to accurate depending on the calibration and other factors. Granted it is a low cost Kalloy post so not carbon or ultralight stuff but still it is helpful to torque properly.

I remember reading that Eddie Merkx carried a spare seat post bolt because he adjusted his seat height so often that they fatigued. It didn't say how he got the stub out.

Many thanks guys, for the solid and prompt replies. Yes, it is a Allen/hex head, and yes, I did retain and remove both halves of the bolt, so hopefully I can at least match the threading.
I'm not knowledgeable on the specifics of metallurgical properties, so I wouldn't know what to ask for. I've seen a couple options on line, that state Kalloy in the ad, but again, their stated info leaves me unsure about its actual compatibility. If they were a piddly $1.50 at Lowes, I'd take a chance, but at $8,plus tax plus shipping, and still unsure that its correct, I'm probably on safer ground just buying a new post for $20-something,delivered (as I just did).
Anyway,thanks again....

Don't know about all, but my local ACE hardware has a very large assortment of loose nut, bolts, washers, etc. In SAE and Metric. Needed a hardened bolt for a lawnmower--found it there! Hopefully, there's an ACE near you with the same great selection.

Had the same thing happen to me 3 miles from home many years ago. Stuffed the saddle in my jersey pocket and rode 3 miles standing - boy was that ever grueling. Had to take a couple of breaks. Went to LBS and they had a replacement and all was good.

Yes, it happens to the best of us. Mine broke in 2013:

https://cimg5.ibsrv.net/gimg/bikefor...c7faf606dc.jpg
https://cimg6.ibsrv.net/gimg/bikefor...27af2c6d80.jpg
Prior to this, I was hearing a creaking noise coming from the seat tube. I thought it might be a loose seat post or saddle, so I tightened the bolts - not knowing I was hastening the failure.

As I recall, it's a M8x1.25 bolt (same diameter & thread as many MTB stem clamp bolts).

Glad you are uninjured - from experience, the feeling of not having your saddle under you anymore can be unnerving.

I would like to know how OP (Brocephus) got home on his ride after the seat bolt snapped. I ask b/c it's possible to ride standing up! (Although that could be fatiguing over a long distance, I suppose.) Or did he bail and call the little woman to pick him up? Or Uber/Lyft?

i was at the top of a hill, so i turned around and coasted back down, then started walking a bit while sticking my thumb out to any passing pickup trucks ( about 70% of the vehicle traffic on this country road).
Then i got bored walking, and started coasting down the hills,and hammering up the other side (while contantly reminding my self to NOT sit down!!)
Finally, (not very long) I got to a 3-way intersection where most traffic slowed and turned, and headed my direction. I figured them going slow,rather than blowing by at 50mph, worked to my advantage. So I stayed put, and removed my helmet and sunglasses, to allow a better look at what a harmless, clean cut all-American i was, and held my thumb out while trying to highlight the damaged bike, and damned if the first truck didn't stop, in under 5 minutes !! It was a guy and his wife,taking their kid to a birthday party, on the road i lived on. It helped that the guy said he'd seen me riding a number of times.
So, no, I didn't call the old lady,or a friggin' Uber, LOL!

​​​​​​https://www.homedepot.com/c/ab/grade...fab90189731df8

"The little woman" meaning what exactly? Why the need to say that?

Yes it is quite possible to ride standing up. I have known people who have done long rides standing it is doable, maybe not as fun but you can make it work.

I usually replace the hardware on my bikes with titanium stuff from Amazon. It’s lighter, the better quality bolts and nuts are better threaded, and I haven’t had any failures. Most bolts on bikes are M5, M6, and M8, with an occasional M7 (like the stem clamp bolt on my Birdy), you just need to choose the correct length.

Nope, not bulletproof. I had one fail a couple of years ago, after ... about 25 years of service. It was on a descent, hit a medium-ish bump and suddenly - hey! what's this wiggly bit between my legs!

A good portion of my weight was on my feet, so no big deal. I managed to find the bits that had fallen to the road, stuffed my saddle down my jersey and rode home standing (only about 2 miles). My LBS drilled out the stub of the bolt and gave me a new one, took about 5 min. and they didn't charge me.

I suppose it's probably a good idea to replace the seat post clamp bolts periodically, but I've no idea if I'll remember in 15-20 years that I have to do so for my current bike (assuming it, and I, survive that long).

If I was replacing "mission critical" fasteners, the last place I would go to is Ti from Amazon. Apart from the occasional blatant counterfeit stuff, Amazon sells at the lowest price point, and that includes fasteners. You're likely getting Ti of unknown provenance and QC. If the fasteners matter (I'm thinking stem- and seat post fasteners, mainly), I'll pay the extra and get them from a legit hardware supplier like McMaster-Carr. High-grade steel fasteners are also stronger then Ti-equivalents, Ti is lighter and has better corrosion resistance, but for small fasteners (again, stem bolts), I'd rather good steel - higher tensile strength and the weight saving of Ti is negligible.

I used to work in a machine shop which manufactured hardware for aircraft engines, and can tell a good piece of hardware from one which is not so good. High quality steel is very strong, but you aren’t going to find high quality steel in Kalloy components. I have occasionally got some bad things from Amazon, and returned it. But, for the most part, the quality is good, and I’ve had nothing to complain about. The hardware is light, well-finished, doesn’t corrode, and is reasonably priced.