Unca_Sam

If anyone has a 1973 Raleigh Supercourse with their original binder bolt, I'd appreciate pictures and the length of the bolt.
TIA

jackbombay

This is from my 1972 super course,

The bolt of course has the single tab to prevent it rotating,


Here is the length of the bolt, 27mm.



And diameter, 7.8mm.



Diameter of the round head of the bolt is 13mm.

Unca_Sam

thanks!
How far apart are the ears on the seat post clamp? Mine are 17.5mm, which makes me wonder if it's a little deformed. I received neither a seatpost, nor a complete bolt!

jackbombay

Mine are at 20mm.

Are the sides of slot in the back of the seat tube parallel to each other? The width of the slot is around 2.5mm or so, so if your ears are at 17.5 your slot is possibly nearly closed at the top?

Unca_Sam

Pinched seatpost binder

No, they were not closed, but were not parallel. My calipers were measuring towards the outside of the tabs, inflating the error.
I expanded the seat tube with several different sizes of steel seatpost. I ended at 26.4, since 26.2 seemed to be the right size, but tighter than I wanted. What size seatpost does yours use?

BFisher

My '73 uses a 26.4 seat post.

Unca_Sam

...i might have more work, then

nlerner

I’ve owned lots of early 70s Super Courses, and seat post sizes have varied from 26.0 to 26.2 to 26.4. Classic Raleigh inconsistency!

Unca_Sam

That's precisely why I didn't know the seatpost size, without starting with one. I have one vote for 26.4 for a 1973 Carlton made supercourse. I can go back to ther co op and pound a 26.6 seatpost in to stretch the clamp back out to 26.4.

nlerner

Well, if you have some vernier calipers, you can measure though if the lug is distorted from over tightening, you might not get an accurate measurement.

Unca_Sam

For those that are following:
Sheldon Brown (bless his soul) created a database with seat tube sizes for various bike models in various years of manufacture. My seat tube is 26.4mm, after cold-setting the lug with well-greased seat posts of increasing diameter, handy at the co-op.

rocks in head 

This was a super helpful thread. I now have a seatpost of the right size and a new binder bolt coming for my '73 Super Course restoration. The seat tube was pinched and out of round, which I will have to cold-set back open a bit. I've got a few smaller posts that I plan on using for the job so that I don't destroy the alloy post that will be going in for real.

Unca_Sam

😉.
It was only possible with the help of others. That and clear subject titles.

bertinjim 

Unca_Sam-

If there's a framebuilder nearby, get him to ream and hone the seat tube to the specific diameter you require. The fit will seem like a miracle as almost all seat tubes go out of round during brazing.

Piff 

While this thread is around, a question. my super course frame (mk. ii) did not come with the binder bolt. I used a recessed brake nut, a few washers, and a regular bolt instead. I tightened it down, not like a gorilla, and the seat post hasn't slipped a bit. The ears/slit look fine. But, does this setup have the potential to improperly bend the ears and slit of the lug? AKA should I fork out the money and source a raleigh binder bolt?

Unca_Sam

I can't give you an answer on that. From what I know, the two surefire ways to screw up your seatpost clamp is to use a post smaller than the design, or to ignore recommended torque values and tightening to the point the ears become ovalized. Plenty of newer bikes use a recessed nut, or are simply tapped to accept the bolt.

Regarding a "Raleigh" binder bolt: as long as it's there same diameter and keyed, any bolt and matching nut will do the trick.