Surface blemish or more serious?

[A1anP]

Hi,

I rescued an old steel frame bike (Sun GT10) from being skipped but I'm wondering if there is any point in trying to get it going again. I'm a little worried by some cracks in the paintwork which might indicate possible cracks in the frame, and thus make it unsafe. Here is a photo of the worst area, where the bottom tube joins the head tube...



There are a fair few rust spots on the frame also, but nothing major so that doesn't bother me. I'm happy to ride a rusty bike but not a dangerous rusty bike.

What do you think, am I being over cautious?

[Mike Sales]

That looks to me like the effect of a head on collision which has made the head tube a bit more vertical than it was. Feel underneath the cracked section and you may detect a little bulge. This would confirm my guess. Was the front wheel a bit too close to your toes? If I am right the frame is not worth saving, though the craced paint may not indicate cracked steel.

[A1anP]

Thanks for that Mike. I looked and felt underneath the area in the photo but couldn't find a bulge. However, the quill stem was snapped and the bottom of the threaded part of the fork has a bulge in it where that happened, which could point to an impact. Guess it's not looking too promising

[Valbrona]

That's the crumple zone in the case of head-on impacts.

[Brucey]

I'd suggest that you remove the paint from the area where it is a cracked and inspect carefully. If the frame itself isn't cracked or bent then it may be OK to use; repaint (ideally with a thin layer of light-coloured paint) then just keep an eye on that area so that if it cracks later on you will spot it.

If in any doubt about the fork, replace it. Cracks in the main frame are usually nothing like so dangerous, simply because there are two tubes which must break before you will definitely crash. In the fork steerer this is just one tube and furthermore it is mostly hidden from view, so you may not notice that it is cracked and just about to let go....

cheers

[JohnW]

That looks to me like the effect of a head on collision which has made the head tube a bit more vertical than it was. Feel underneath the cracked section and you may detect a little bulge. This would confirm my guess. Was the front wheel a bit too close to your toes? If I am right the frame is not worth saving, though the craced paint may not indicate cracked steel.

...........I agree with that, and it could be the reason why the frame was being skipped. Personally I'd write it off, but certainly I'd say that a head-on which did that has very likely made the front forks unsafe.

[Vorpal]

I'd suggest that you remove the paint from the area where it is a cracked and inspect carefully. If the frame itself isn't cracked or bent then it may be OK to use; repaint (ideally with a thin layer of light-coloured paint) then just keep an eye on that area so that if it cracks later on you will spot it.

+1 If you are worried about not seeing / feeling cracks, get some dye penetrant (available from welding supply, and some DIY places). Instructions for inspecting with penetrant are readily available on the internet (WikiHow, YouTube, etc.)

[A1anP]

Thanks for all the suggestions. I've filed off the paint at the affected areas on the frame, and all I can see is bright metal, no cracks. That is without any dye penetrant though. So far so good.

As for the forks, I've attached a photo showing the bulged area (and the broken quill stem for comparison). Could that be due to the stem being raised too far up? As long as the replacement stem is anchored below the threaded area, I think I should be OK. Is that right?

[531colin]

Looks to me like the stem was inserted only an inch instead of "to the mark" or 2 1/2 inches...
The steerer is slotted for a headset tab washer.....another stupid idea.....take a bit of the frame that's reasonably OK as it is, and cut a slot in it.....
So some genius inserts the stem so the expanding bit of the stem can spread the steerer where its slotted.....keep tightening the expander, eventually the stem fails at the top of the slots that allow it to "expand".
You probably could get away with inserting a stem setting the "minimum insertion mark" at the bottom of the steerer's slot.....that way the stem is inserted in un-damaged steerer, and if the damaged bit suddenly "lets go" what will happen is you will suddenly lose a proper headset bearing, which is likely to be be survivable, whereas suddenly losing the handlebars will almost certainly result in a face-plant.
Then all you have to overcome is......
bent frame
possible bent forks
dodgy headset thread making adjustment interesting.
I'm afraid I can't see the point, personally....maybe if it was a classic, you had all the original parts, and you wanted to clean it up and put it in a museum, but as a rather ordinary bike, I don't think the ride will repay the work.
You might find its built for 27" wheels, 120mm OLN rear, and stuff like that as well.....maybe even a "Raleigh thread" bottom bracket shell? (probably too recent for that)

[Brucey]

Eyuck....

I agree with Colin's diagnosis; as for the prognosis.... well you have to decide how much you want this particular frame back on the road.

BTW if you wish to salvage the stem (for some reason) I'd suggest trimming the stem to suit a slant-cut wedge piece from another stem, and a proper insertion depth next time round.

cheers

[mig]

what sort of riding would this bike see? only something very gentle and would it get very regular inspections?

if it's 'everyday' riding then i'd put it back in the skip. can you really picture yourself hurtling downhill on it and attempting to carve through that steadily tightening turn at the bottom safely? anchoring on hard when a car cuts across your path?

[A1anP]

The bike is more or less complete so I thought I'd be able to get it back in basic functional mode for about £50 or so. No particular reason for doing it, just a challenge / learning project that fell into my lap. It would probably be used for sedate day trips, I already got myself a cheap (new!) road bike for when I fancy going a bit faster.

Going on the comments, I think I'm going to stow it away in a dark corner of the basement just in case any of the parts might come in useful in the future. I'll keep an eye out for another project though, as I'm enjoying the tinkering, but maybe something a bit less risky looking...