Wat are some things to watch out for when looking to purchase a used titanium frame bike besides the obvious- cracks? I'm looking to buy a Litespeed. Thanks

Some of the older titanium road frames are pretty limited in the tire clearance area. If you can live with a road frame that takes a max tire size of 700x25 then there are some deals out there. If you want disc brake or through axle mounting you might have a hard time finding a used titanium frame in your size at a good price.

If memory serves, Litespeed had some quality control issues with rear triangle misalignment. If the rear wheel / dropout / stay combo doesn't look right - say not parallel to the frame line - it's a hard pass.

If it is an older Merlin it might have their own proprietary press-fit “GreaseGuard” bottom bracket. If it has this, you may have to keep the build “old school” & continue running square taper cranks.

Check also for Airborne, Lynskey, Dean, Serotta, Moots, Dedacciai and Independant Fabrication titanium frames,they are well worth it. Check if there are no cracks in the welds and if the rear triangle is aligned

Find a point on the seat tube---if the bike has a split in the to of the seat tube that is good; if not slap on a piece of cloth tape and find the center of the seat tube and mark it. Run a piece of thread from the back of the dropout to the center of the seat tube on both sides. if the thread doesn't reach or goes to far .... sayonara.

(Tip I picked up for cold-setting frames.)

I have steel frames that would not pass some of what is said, they ride beautifully around the block w/o hands on the bars, just ride it, you will know. I got an unrideable Reynolds 753 frame/fork back from a local framebuilder who straightened it on his Marchetti frame table and and it would flunk any string test by a long way and 1,000s of miles later I can ride it around the block w/o hands on bars.

Frame issues are frame issues. As far as I know, titanium bikes don't suffer any frame issues that bikes made of other materials don't. All bikes may crack, all bikes may become misaligned, all bikes might have threading or press fit issues. Metal bikes might bend. Thankfully hidden frame issues are very rare.

One frame issue that ti bikes sometimes have involves seatpost creaking or slippage. If the former owner did poor maintenance or rode it in the rain a lot and failed to use anti-seize, then fitting your seatpost may be a challenge. My titanium frame was made to run a 30.0 seatpost but I was able to put a Delrin sleeve in it for a snug creak-free fit with a Ritchey Flexlogic carbon seatpost. The Delrin sleeve finally cured the creaking & slipping issue where the aluminum sleeves I tried didn’t.

May I suggest that a carbon fiber frame will not become misaligned. It retains its shape from the factory mold.

Carbon monocoque, concur on the above.
Carbon tubed w/ aluminum alloy lugs, can be misaligned.

Trek OCLVs would be my choice and entirely made in the USA and built like a tank.

Almost all of Trek's frames are made in Taiwan today. Compared to the other brands, there isn't much difference.

not sure - did Litespeed have issues on some frames with the head tube / area around head tube at one point ?

check top of seat tube / seat post clamp area ... I’ve seen Litespeed and Merlin frames with damage in this area

In theory yes, but I have never seen any data with frames sitting in a hot or cold garage after 10 years.

At the same time, I can say that measuring head and seat angles of bikes - all materials - will show variations in said angles. Easy to do and much more common with lower end brands that are most likely using open mold frames and just lying about the numbers. Bring a protractor to a bike shop.

Mountain bikes are shocking bad and many of the so called "steep" seat angles are not that steep...

A hot or cold garage isn't going to warp a carbon frame. Carbon fiber composite's thermal stability is very high.

I don't understand how a carbon frame could be made in an open mold. As I understand the process, frame molds are two-part clamshells (i.e., closed). The geometry of a frame made in a such a mold ought to be consistent, as the mold's geometry obviously doesn't change. Unless I'm missing something.

Good suggestions here. I would add that you should give the derailleur hanger a close look.
Most - if not all - titanium builds do not utilize a replaceable hanger.
Also, pay close attention to the fork - typically carbon fiber.
Litespeed frames are incredibly sturdy, so any sort of head-on collision exposes the fork as the weak point.
My '94 Merlin will accept a 28 rear tire; possibly a 32, but I have yet to try.
And, thankfully, it came with a threaded bottom bracket shell. Avoid their pre-'94 pressfit!

If money is tight I can see looking at a used bike but there are some decent new bike deals on Lynskey, for example.

If buying a used bike check out more than the frame. If the wheels are trashed and the drivetrain is worn out your used price might not be so good.
Also, is it going to fit your body and do what you want? The last used bike I bought, titanium, coincidentally, needed different saddle, post, bars, stem, crank, and cassette before I could use it how I wanted.

Open mould is not meant literally. It just means a generic design rather than a custom made mould. A kind of off-the-shelf mould shared by multiple brands.

The last bike I bought, also titanium, needed pretty much everything except the frame, fork, and headset. Everything else was basically worn out. But the frame, once stripped, cleaned, and "polished" with strips of red Scotchbrite, was in excellent condition. And of course - no rust!

I knew what size I wanted long before I bought it, though, having spent a fair amount of time going over the geometry charts in old Litespeed catalogs.

I tend to buy just framesets or bike a whole bike assuming I'm only going to get the frameset and valuing it accordingly. I suppose part of that comes from the expectation that I'm mainly interested in buying classic frames but setting them up with Campagnolo 3x10 speed ergos.

The stuff wasn't worn out on mine, it just wasn't the way I wanted it. I test rode it alongside a cf Ridley. They both felt awful because of the fit. They were pretty close checking with a tape measure but the Seven is custom so no chart.

And the gearing, 52/39 with 12-25, was fine for rides with some climbing but not for mountains when tired. It will be 11 years on that bike this spring.

Open mold does not refer to the manufacturing process but who owns the mold. In the case of open mold, it is a frame that can be sold under many names and guises. Often times, brands like Cinelli, Jamis, Engine 11, Masi, etc, will buy these bikes and stick their names on them. Often, they will use geometry figures that come from what they want, and not necessarily what they got.

As for the point about warping of a frame, my point stands, I have not seen any data for this, so can't say if it can happen or not - for any frame material.

Your point does not withstand the smallest amount of scrutiny. The idea that a hot or cold garage might possibly permanently deform a bicycle frame is just plain silly.

Scrutiny requires examination of data. Do you have data?