1935 Shelby Seat Post Bolt Issue

[TexWest]

Hello all,

Looking for a bit of help with a seat post and seat post bolt issue. My old Shelby has what I believe to be the original post bolt and there are several problems. My main concern is that the frame doesn’t close far enough to grab the seat post. I’m quite hesitant to crank on the bolt for fear that I’ll damage the frame. Over time it looks as though the tab that typically holds the bolt in place while you tighten is less than effective at keeping the bolt from turning. It appears that folks have attempted through the years to stop this turning by grabbing the now rounded bolt head. With these issues I’m quite happy to remove it and to replace with a similar bolt but the thing will not back out. It seems that this bolt is somehow kept in place by design or it simply has 1 or 2 threads that won’t grab on the way out and therefore it won’t back out. (The bolt isn’t perfectly straight either) Is there anyone out there who’s seen these issues before, please share your experience. I want to just cut the head off this bolt, but not sure if that’s the best way to go. Also, the frame measures right 7/8 but as stated a 13/16 post cannot be tightened. Months ago I tried a shim that should have remedied this and it did not. I was unable to get the post in at all with the 1/16” shim, so I’m not certain what’s going on here. I guess it can simply be chalked up to, this is a 90 year old bike.

 

[Archie Sturmer]

A replacement 5/16"-24 bolt, nut and flat washers might work; but two wrenches might be required to tighten or un-loosen.
To remove a tight bolt, one might hammer it out from the other side, (perhaps with the nut protecting the threads somewhat).

If the seat post clamping area has previously been over-tightened, then one might use an expander type post or stem to widen enough to fit the correct post.
A 5/8" post with two 1/8" shims might fit the 7/8" frame?

 

[bloo]

0.833"/21.15mm seat posts are a thing, although I am not aware if Shelby ever did that. There are people in here who will know.

There is a Wald shim meant to adapt a 13/16" stem to a fork intended for a 7/8" stem. It can be useful to get a 13/16" seat post to fit a 0.833"/21.15mm seat tube, if it turns out that is what you have.

 

[TexWest]

0.833"/21.15mm seat posts are a thing, although I am not aware if Shelby ever did that. There are people in here who will know.

There is a Wald shim meant to adapt a 13/16" stem to a fork intended for a 7/8" stem. It can be useful to get a 13/16" seat post to fit a 0.833"/21.15mm seat tube, if it turns out that is what you have

0.833"/21.15mm seat posts are a thing, although I am not aware if Shelby ever did that. There are people in here who will know.

There is a Wald shim meant to adapt a 13/16" stem to a fork intended for a 7/8" stem. It can be useful to get a 13/16" seat post to fit a 0.833"/21.15mm seat tube, if it turns out that is what you have.

many thanks for the info. I’m looking into this right now

 

[TexWest]

This problem is just getting worse. I tried everything I could to remove this bent seat post bolt before I gave in and cut the head off. My apprehension was warranted as I’m now unable to remove the bolt even without the head. The thing just turns and won’t grab the last couple threads to come all the way free. I’ve never seen a fastener issue like this in all my years working offshore. Things a real head scratcher. I can only imagine there’s a bur or jacked thread inside the frame that I’ll never get at. Any suggestions?

 

[buickmike]

The hacksaw blade dropped right between the stays. So bolt is curved. You cut at the height of the bend . Just to make it interesting; When you get about 3/4 thru , put a socket on it - or attempt to put a drift pin on other side.

 

[buickmike]

Unless the "tooth"under bolt head is still lodged into casting.

 

[TexWest]

A replacement 5/16"-24 bolt, nut and flat washers might work; but two wrenches might be required to tighten or un-loosen.
To remove a tight bolt, one might hammer it out from the other side, (perhaps with the nut protecting the threads somewhat).

If the seat post has previously been over-tightened, then one might use an expander type post or stem to widen enough to fit the correct post.
A 5/8" post with two 1/8" shims might fit the 7/8" frame?

Thank you for the info

 

[TexWest]

Thanks guys for all the tips, pointers, and assistance. I guess sometimes you’re too close to the problem to see what is clearly going on. I took a 5 min break and then realized that my frustration brought my IQ down several points. Obviously this is a shouldered bolt, therefore I was never going to run it clear on the threaded end due to the hole on that side of frame being smaller(catching the unthreaded shoulder). As I suspected there were a couple of jacked threads that were too ugly to pass even with the aid of a jewelers file, so I cut another quarter inch off and it pushed through the head side of the frame. My apologies for my nearsightedness. Your help is always appreciated fellas.

 

[Wolfmac]

Perhaps you can rotate the bolt so that the bend in it favors the contour of the tube then drive it out with a drift punch.

Then determine which shim and post diameter fit appropriately. Here are examples of these shims commonly found on this period of bikes.

This is a relief cut bolt that is sometimes applicable when not using a shim.