air seat questions

I will be soon getting a cf miyata seatbase and cover. What is the general consensus as to the best filling for said seat parts. A 12 inch tube and the miyata foam, or a larger tube doubled up? If it’s the doubled up tube what size should I use?

Try it both ways and see which way you like best.

With the single layer air pillow with Miyata foam on top a 16 inch tube will do the trick as in my airseat gallery

With the double layer dogbone air pillow a 20" tube fits.

Play around and see what’s most comfy for you.

The double layer dogbone will be softer and more squishy. But it will feel like an old waterbed and you may have problems keeping the seat from getting lopsided. The single layer with foam on top will be a bit more firm, but will feel more solid like a normal seat. The choice of foam has a big impact on how the seat feels.

I just built an airseat for a friend. Unfortunately, sent 9 individual bolts, not the “u” shaped bolts that I have on my old CF Seat. Also these bolts are all flat and round and smooth on the head of the bolt - nothing to grab onto when you are ready to tighten the bolts.

With the “u” shaped bolts, you can tighten them from the underside with the seat fully assembled. The bolts will not spin.

Are these"u" shaped bolts available? Or, should I just go to a hardware store and get something more workable? Any ideas?


The “U” shaped bolts you got were from the old “Made in Japan” Miyata seats. Can’t get that hardware any more. The new Miyata (or Torker) seats have all straight bolts.

What you got from are probably carriage bolts. With the carriage bolts you drill an undersized hole and then use a small file to file the hole square so it fits the square shoulder of the carriage bolt. A carriage bolt in a square hole will not spin.

See this thread: seat base instructions for more info on drilling the holes.

Joe, I used carriage bolts on my CF job and they worked great. This is the way to go. As JC notes, you need to get a needle file to turn your round drill holes into square holes that will hold the carriage bolts. Two recommendations when you do this:

  1. Wear one of those paper cone masks you can get at hardware stores. Otherwise you’ll get miner’s lung as you file away.

  2. The drill hole doesn’t need to be all that much smaller than the bolt size. I probably could have gone one size bigger on the drill bit, and as a result I had a lot of unnecessary filing to do. Maybe find a non-critical part of the seat and experiment. I think the smallest step down in bit size from the size of your bolt should do the trick. JC…thoughts on that one?

As long as the drilled hole isn’t too big it will be OK. The closer you can drill the hole to the final size, the less filing you’ll have to do. It would be a bad thing to drill the hole too big.

I don’t know what the ideal drill bit size would be for a 1/4" carriage bolt. I don’t have a 1/4" bolt handy to measure to find out.

Picking the right drill bit size is one area where I would measure and double-check twice (or thrice) before drilling that first hole.

It needn’t be part of the seat :stuck_out_tongue: , anything will do, wood is not recommended as it will have an apparent size smaller :angry: than the hole in, say aluminum (which is good, easily available, cheap). Start with 1/4 and go down in 1/64th increments or numbered bits if you have them - I use my drill index for a starting point on such things.

If you have a caliper, measure the sides of the square section nearest the head (it’s tapered), as it isn’t the threaded section you’re cutting the hole for. Also, keep in mind that it’s tapered while you’re fileing, for a better fit - it should be a just snug fit for max strength.

Yup - they sent me carriage bolts.

Too late. I made the seat during East coast Muni weekend in a rush so that BillyTheMountain would have a seat. I drilled the holes so that most of the bolts were tight at the square area. However a few were spinning. I’ll try some bolts with a hex head, or phillips head so I can tighten them better. Obviously I’ll need to remove the seat cover/tube, but it’ll work.

The seat did last a four hour ride, but obviously needs improvement to be durable.

Thanks for letting me know about the extinct u bolts - at least I’ll stop wondering if they can be found.

Also good to know how to do it right, even if too late!

Does anyone happen to have a pattern for the dogbone airpillow or should I just make my own?


Although the u-shaped bolts are no longer used you can easily fabricate a resonable alternative. Using threaded rod (available from most hardware stores) you can cut and bend you own. Be careful when bending the rod as it may be prone to break at the bend.

I’ve done this with my last (chinese made) Miyata saddle and it’s holding up fine. With this setup it is impossible for the bolt to spin.

For more details on this see:


A couple of other fixes for the oversize hole problem:

Buy an epoxy kit( 5 minute, or JB Weld, etc.). Apply some car wax or a very light film of Vaseline to the bolt threads, square shank, and underside of the head to act as a release agent. Mix the epoxy and apply a small amount on the underside of each bolt head, put the bolt in the hole and put a piece of tape over it and leave the base sitting upside-down to cure. The epoxy will mold around the square and keep the bolts from spinning, but they can still be removed. It will hold better if you chamfer(bevel) the sides of the hole a little first.


Have someone weld small bars or rods between the bolt heads. Very easy (for a weldor) and works great.


I saw somewhere in the gallery what I thought was a pretty clever method of stopping bolts from spinning. The clever mperson in question cut a notch into the end of the bolt. This allows you to use a standard screwdriver to keep the bolt still while you use an open wrench to turn the nut.

Simple but it worked.

Maybe someone could get a run of custom square u-bolts from

Or perhaps there’s something standard that would fit.

Although I guess it’s a metric one that’s used on unicycle seats.


The ones we use arent quite like that as the arch in the back would probably be too large. Ours are right angles.