Bolt for CF base Question

could someone please tell me what size (USA MESURMENTS) carrige bolts i should get for my carbon fiber seatbase?

It doesnt realy matter as long as there kind of close because you will be fileing the holes to the size of the bolt, the holes in the seat post are are wider than the bolts so they can be a little bigger and still be fine and you will probably need to cut the bolts down to length watever because you probably wont find any short enough. I just took one of the bolts strolled into a shop I thought might have them found some that looked simalar and bought them and they were fine, I only needed 2 but I bought all 10 because the ones I found looked better.

1/4 inch you want 16’s and 20’s, I think those are the ones that worked for me.

you only need 2 (I think) of the longer size, the rest should be 16mm or whatever it is.

The original 20 mm Bolts can also be
reused (8 of the 10) but they need to be shortened. The Carbonplate is thinner than the Plastic
base. 2 of the Original Bolts need to be used for the front Handle.
according to udc

Wait I don’t understand. Why can’t you just use all the original bolts from the old plastic based seat?

ones stripped and two of them arn’t carrige bolts…

They are too long. The end of the bolt pops right threw the end of the acorn nut. If you use a locknut the sharp threaded end of the bolt will be exposed.

What was ment tho, is 8 of 10 are carrige bolts and the other two are not. They wont lockinto the CF the way the other 8 will.
(the back two wont work)

It is more convenient if all the bolts under the seat are the same thread size (so they fit the same size nuts). That way you only need one size socket wrench (or nut driver) to tighten the nuts. It’s just a convenience issue so you don’t have to keep two sizes of sockets in your repair/maintenance kit.

Get carriage bolts in various lengths and use the ones that fit best. Use enough washers on each bolt so the bolts don’t push through the ends of the acorn nuts.

Would that change the size of the holes I should drill? (I’ll probably get a CF base soon…)

Yes. You’ll only be able to easily find 1/4" carriage bolts in the US. That’s a different size than the stock bolts on the KH seats. It means the size of the square under the head of the carriage bolt is a different size. So you’ll need a different size hole.

So hold off on drilling holes and filing the holes square till you figure out if you’ll use the stock bolts or 1/4" bolts.

Metric Specialties carries metric carriage bolts. The size you will be looking for will be M6-16 or M6-20. Look in their miscellaneous folder under Carriage Bolt and you can find the listings for the two I specified here. The 16mm are zinc and only cost $0.24 each. The 20mm are stainless and cost $0.72 each. I didn’t see the 16mm in stainless…too bad. M6 bolts are slightly smaller than Imperial 1/4" bolts.

Edit: Be sure to get some M6-1.0 nuts to match if you don’t have them. They even have acorn nuts in stainless for $0.88 each in the folder Nuts, Other. Don’t worry about the washers, 1/4" will do fine.

Metric Specialties, listed above, is in Burbank, CA. They have a line item minimum order of $2.00 and a minimum order of $25.00. This means you will be charged at least $2.00 for each item you order. For example, if you order 5 carriage bolts at $0.24 each, the total is $1.20. But they will charge you $2.00 for these to meet the minimum line item requirement. At the end, you will be charged at least $25.00 for the whole order. If you only want the 5 carriage bolts they’re going to charge you $25.00 for them. I don’t know if this will be cost effective for you or not. It depends on how many of what you order. If you order stainless carriage bolts in a couple of sizes and stainless acorn nuts it might not be so bad. You could by a bunch of extras and sell them to Forrest.

Sounds like a job for UDC to stock seat hardware for the metric sizes that are hard to get in the US. Stocking aluminum hardware as well would be even extra awesome.

The alternative instead of carriage bolts is to use a T-nut inside the seat and then a regular bolt instead of a carriage bolt. Drill a round hole and then cut a slot for one of the tee-nut prongs. Bend the rest of the tee-nut prongs flat. Glue or tape the tee-nut in place inside the seat. That’s the way Max Dingemans from the TCUC made his CF saddles. Made for a slick setup with less hardware hanging down under the seat that can catch your fingers.

Just cut the bolts down to size. put them in the base so you can see where to cut them then take them out and spin a nut on. With a hacksaw cut them to lenght then spin the nut off which will take most of the burs off. Then with a file just clean up the end a little and your done. Its quick and easy to do and it will mean that all your bolts will be the right length with no need for washers.

here we go!!! i got the cf base in, wish me luck!!!

Take some pictures of the process or the final results if you can. There aren’t many pictures showing how the bolts and CV base all fit together.

Don’t worry about being perfect. None of the holes in my CF base are square. Some holes ended up being filed to a rectangle shape (like a slot) to move the hole over because the hole drifted while being drilled. There is plenty of room for slop. The hole just needs to keep the carriage bolt from spinning and for that it only needs two points of good contact (like in a slot). Perfect square holes are not necessary.

there it is, its very nice

here are a few more…

the whole uni

I’m going to use the original bolts, but what do I do about the rear bumper’s bolts?

Shoot. I don’t want to have to buy bolts.