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Most old vintage steel bikes with rust aren't actually worth restoring. What I mean by that is that although lugged steel bikes can be theoretically repaired, you can braze in a new tube or seat stay or chain stay, it usually isn't worth it. I mean that in several senses, in that it isn't worth it financially nor is it close to worth it in terms of what you end up with in the end.

You can pick up a nice aluminum Eddy Merckx frame these days for about $200-300. Although there are thousands of people that have been inculcated into the "steel is real" cult, the reality is that in terms of performance and efficiency a modern aluminum bike or carbon fiber bike is almost incomparable to a vintage steel bike. Fairly, many people disagree. Like the members of car clubs, the population of people riding classic and vintage bicycles is aging, and fairly rapidly. There are many many people that as they age and their flexibility decreases and their bones become more brittle actually reasonably due prefer steel bikes. Vintage steel race bikes with butted tubing like Reynolds 531 can be best understood as an old ladies Cadillac compared to a modern aluminum or carbon fiber racing bike. The difference with cyclists as compared with people who collect vintage cars, is that we still pretend to be performance cyclists when for many of us those days are long past. At best most of us are recreational cyclists, and the idea of actually having the fitness or the form to race competitively is almost absurd. With recreational cyclists there is a very reasonable argument why vintage steel racing bikes are a great "fit" if the bike fits.

Reynolds 531 tubing has been around since the 1930s. Its a legendary tube set in the cycling world. Reynolds 531 debuted in 1935 and its been a favorite of frame builders since. Its easy and cheap to work with and its forgiving of frame building errors. It made what was a comparably light frame set with good riding characteristics, located in context historically. Its nothing compared to a performance Reynolds tube set like heat-treated Reynolds 753, but almost all frame builders failed when attempting to build 753 frames (you had to send in 753 frames back to Reynolds for their certification process), it didn't tolerate sloppy low-skilled builders and you couldn't just "bend" the frame to correct for imprecision on the jig. In fact you can't even cold set a 753 frame to change the rear dropout spacing.

For the modern cyclists, Reynolds 531 bikes are like 60s and 70s sports cars. You can go down and buy a modern Mercedes or BMW four door businessman's coupe that will embarrass almost any Ferrrari, Masarratti, Corvette, etc. of those eras. However, that isn't why you collect and drive those cars, just for their pure performance. The same is true for the vintage bikes. They just don't compare in terms of performance to even vintage aluminum, vintage performance steel bike with Reynolds 753 tube sets, or carbon. However, that is NOT the point. Many of these bikes were built by frame builders or shops that had a real cache and history. Owning a vintage or a classic steel lightweight racing road bike is NOT just about performance, as the paradigm changed with the onset of aluminum and then carbon, but its about what these bikes are, not just how fast they go. It is only an added bonus that as most of us age that the steel frames give us a enjoyable comfort ride as well.

In terms of this being your grandfather's bike, I'd caution you to slow down and do things right. With stripped bolts acquire the right tools like a cheap Speed-out bit set which you can get for less than $20 at Home Depot. If that doesn't work for rusted bolts, and it might not as they are really designed for screws not bolts, you'll need some better extractor tools. However, I agree with the above poster in that the fact that this was your grandfather's custom bike means it should probably be treated as the best bike in your stable.

Whereas just a normal Reynolds 531 bike like a vintage Colnago, Olmo, Cinelli, or Pinarello isn't really going to be worth the cost of replacing rusted/cracked tubes and stays, let alone the cost of a professional repaint, IF the bike matters to you on a personal level, and yours clearly should, then the cost/value calculus goes out the window. I may not understand why someone would spend serious coin repairing and replacing a dime a dozen Colnago 531 bike, when the repaired bike won't be quite either as authentic, or as handling neutral as an undamaged original, not to mention the paint being non-original, but plenty of people make that decision because they want to keep that bike, as its personal to them. I can understand completely restoring a vintage custom that was made for my grandfather, and in my mind such a bike (if it fit me) would necessitate a CycleArt repair and restoration.

I think I'd sell every other vintage component and bicycle I've acquired over the last twenty years to fund such a project if necessary. You can have a Mustang GT, a vintage Model A, or even a kool cat Porsche bathtub but there is just something altogether different about a car that was actually YOUR grandfather's. With bikes, I want you to understand how truly rare it is that bicycles actually fit the son, or the grandson. That never happens. Also, what is even more rare is the fact that your grandfather was actually a cyclist and not just tooling around on some boat anchor stovepipe Schwinn.

There is no amount of money I wouldn't spend to repair and restore that frame. The components, handlebars, and stem I'd keep and hang in my garage, but I'd replace everything with nicer modern stuff.

I say FULLY restore that bike. I mean CycleArt restoration, or send it to Mark Nobilette for the inspection and repair and then get Joe Bell paint. It was your grandfather's bike. Carbon is short-term disposable, but you have something truly special to YOU. Everything else is just a bike, you have YOUR Grandfather's bike. Which is something most of us can only dream of.