Spinning bolts on CF seat base


I just drilled out my carbon fiber seat base and put all the brand new guts into it for what hopefully will be a nice new air seat.

I have the problem that the back 2 bolts on my bumper just spin. I cant seem to get my hand inside the roach cover with all the stuff in there to get a hex key in there to hold the bolt.

Any tips?


you could always try taking the stuff OUT of the cover, tightening the bolts then putting it back IN. But thats my what i would do. :stuck_out_tongue:

You took Roger an my advice and put a shred of innertube between the rail adapter and the cf base, right? Just a reminder. Also, you could cut some small rubber washers and put those between the bolt heads and the base to add some friction. Then you can re assemble and first tighten the bolts by hand by pulling down and turning so that the bolt head engages the rubber and provides some friction. As the bolt tightens it will eventually develope enough friction to be able to be tightened with a wrench. Least that’s what I’d do. Hope it works or you get some better advice. Later.

You would have to be very talented, because the bumper goes on last, over top of the roach cover. It would be most difficult to tighten something from the inside when it is covered totally. On my airseat, the back bumper is the only thing I haven’t gotten around to putting on yet, I just have a temporary one duct taped on right now. I can imagine it would be tricky to tighten the bolts if they spin, but I think gerblefranklin’s advice about putting innertube in there should do the trick. I have really thick tractor innertube bits underneath and on top of where the bolts for the Rails adapter and Reeder handle touch the CF, and the friction from the rubber allows me to tighten them from underneath without them spinning. Good luck tightening your nuts Checkernuts.

Re: Spinning bolts on CF seat base


See if this helps:



What kind of bolt or fastener are you using?

Would you be able to use a carriage bolt?
Link to a picture and description of a carriage bolt

If you can make the hole in the carbon fiber base square or rectangular you could use a carriage bolt. A carriage bolt has a square shoulder. If you put a carriage bolt in the right size square or rectangular hole it will not spin. I use carriage bolts on my carbon fiber seats. Drill the hole undersized and then use a file to make the hole square for the carriage bolt. 1/4" carriage bolts work well. Since it sounds like you already have the holes in the CF base are the holes small enough that you can use a file to make them square to fit a carriage bolt?

Boy, I missed that one about the rubber up underneath the CF base. I guess that’s what I get for scanning the board in 5 minutes and leaving, when I log in.

When I drilled out my CF base, I filed corners into each hole for the bolt to seat into. So, that others can learn, Chex, can you explain why only the two back nuts are spinning, if possible.

When I bolted the CF base to the rail adapter, I remember that the arch of the CF base put it high above the rail adapter. I used steel washers to make up for the gap, it seems to have held up well with all the hopping practice of the last year, or is this just a time bomb?

Before I go and take off the seat, I wonder how many people have just used the steel washers with out any distruction of the seat base and had years of success?


Re: Re: Spinning bolts on CF seat base

Oops. That’s what I get for trying to post at bedtime with no sleep the night before.

I formed square holes in my CF base as JC has described. It worked well but I didn’t overtighten the bolts for fear of stripping out the square hole. I also put a rubber pad (piece of inner tube) between the bottom of the seatbase and the top of the seatpost. I thought it best to provide some sort of slight padding there to avoid direct metal to CF contact. Don’t know why I did but it seemed like a good idea.


To add to what John Childs said, if you file the square edges in the CF and find that the carriage bolts still spin, or that there really isn’t a good fit, then go back to the hardware store for larger carriage bolts.

Here’s a view of the kind of fit you should have.

upgrade hardware bolt fit (small, trimmed).jpg

There should have been instructions with your CF seat. It is important that when you drill your holes that you use a 6 mm drill not a 1/4 inch one and that you file the holes carefully to create a square. It does not take long but does take some patience.

Anyway back to the problem… you need to put a slot in the top of the coach bolt with a dremmel to then fit a screw driver in to it. That normally deals with it… when I have been mad I have just took a grinder to the bolt but it makes a bit of a mess. :slight_smile:



I just drilled round holes in my seat base. About 5mm I think. I am using some allen head bolts. I shoved my hand under my roach cover and used a allen key to hold the bolts in the front. The ones in the back are a problem because the cover is a tight fit arround the base of the seat.

I may switch over to a carriage bolt if I need to, but I think I may just try to get someone with smaller hands to fit their hand under the cover and hold it with a allen key.

Thanks for the tips. I really wish I knew the carriage bolt info before I spent money on hardware and drilled out my seat. But I think it will probably end up working just fine.