adamant628

Hi
I just picked up a Gitane TdF frame at my local bike co-op. My plan was to build this into a single speed bike for commuting, using spare parts at the shop. I am currently looking for a fork, and from what I'm seeing on eBay and the like, my head tube is quite long. I am wondering if someone can clue me in on some more specific dimensions and measurements that I need to consider when searching for a fork.

I was told that I want a 1" threaded fork with about 240mm spread. This was one guy's assessment after glancing at it at closing time. Unfortunately, the shop is closed for the winter break, so I turn to you folks for some advice.

So yeah, right now I'm looking for a fork, but I will need everything else eventually, so don't limit advice to just the fork.

Also, if anyone has any advice as to a better place to look for parts, please let me know, but keep in mind I am trying to keep this as a budget, used parts build.

Thanks,
Adam

Ex Pres 

You've not exactly selected the best frame for a budget "cast-off" build, unless your co-op can provide a French threaded BB and Headset. Of course, on a budget you could forgo the French fork and go English, but the French forks of that era had a pretty long rake. I'm not sure how much less rake you could go and still handle well.

What size frame? A 240mm steerer would indicate a quite large one.

afilado

I saw a late 60s'early 70s Gitane fork - not TDF but same rake - at co-op today. Looks to be a smallish one and in lovely condition. Orange/red with chrome socks, decals and pinstripes intact. Original headset attached. I've got a French Campy BB but not cheap. Also have a nice used Stronglight headset, production stock from same era.

How long is your frame's head tube?

J

adamant628

They set me up with a 3 piece bottom braket and while one guy was chasing the threads on the left side, he got a little over zealous and 'chased' them on the drive side in the english fashion. So instead of 2 right hand threaded cups, they are left threaded on the drive side. Not ideal, I'm sure, but they seem to be staying tight.

The frame is probably a little big for me, ~64cm (actually exactly 25.25"). (I'm 6'2")

Head tube is exactly 8", or 203mm. With my rudimentary tape measuring, the headtube looks to be slightly larger than 1" at the top and closer to 1" at the bottom (I didn't have the best light when I went out to my shed just now, and my eyes could have been deceiving me). Any insights on that would be great.

I won't pretend that I know what I am doing and exactly what I need at this point. I got this frame because it was pretty much the only road bike frame that they had at the time that was in the ball park for size.

Thanks for the replies so far.

Ex Pres 

203mm HT would equal a 240mm steerer, like you were told. I've seen some $20 200mm forks recently, but not a 240

afilado

That's a big frame.

I'll take a closer look at the co-op fork as soon as possible, holidays permitting.

J

adamant628

Good to know the guy knows what he's talking about! Is that common to add about 35-40mm to the head tube to determine the steerer size? Is that assuming about 40mm of threading? And am I looking for a 1" threaded or something more odd?

It is. I appreciate it!

Grand Bois

I can't quite make sense of post #4, but it's early in the morning and I haven't had my coffee.

You'll make it easier on yourself if you use a non-French fork. A French fork requires a French headset and a French stem, which requires French bars.

French forks generally have a lot of rake, but the one on my Gitane TdF doesn't have so much. Look for one with a shape similar to mine, but with a much longer steerer. It's easy to shorten a steerer and add threads, but it's not practical to lengthen them.

adamant628

Thanks for the advice, I will do that.

What is generally the difference between threaded and unthreaded forks (other than the threading obviously). What I am getting at is, what do you do differently when setting one up, do you need a longer steerer for an unthreaded stem to attach to? Is anything else different?

Oh, and should I be looking for a fork for a 700c wheel, 27" or is it up to me? Any idea what this bike would have had originally?

Grand Bois

You want a fork for a 700c wheel. They're easier to find. All Gitane TdFs originally had 700c tubulars. A 27 X 1 1/4" tire won't fit on mine. It hits the bottom of the fork crown.

adamant628

Any thoughts on this fork on ebay? item#260708794864. It looks to fit all the criteria, but I'm not sure if it is appropriate rake. Also, a bit more than I planned to spend, but it is looking like this might not be the budget build I'd been hoping for.

Grand Bois

It looks good to me. That's a fair price.

adamant628

How would you compare it to this one, also from eBay: 320633044343

I see that the shape is a little different, the 2nd looks to pinch in a bit narrower below the crown, and I can't really tell how much rake it has based on the picture. Also, would the extra 12mm make a difference if I didn't cut it?

Ex Pres 

Me, I like crowns like #1, and avoid unicrowns like #2 where possible. But that's a personal preference.

The extra 12mm may be a good thing, and is easy to cut off. So that's a positive for #2.
Fork #1 @ 34mm stack height for the headset limits your choices. That's on the short end of what's out there. If you have a headset in hand, make sure it'll fit..

adamant628

Thanks, what is your reasoning for disliking unicrowns?

dddd

I can't answer for ExPres, but this "vintage" group is more about appreciation of vintage iron than pure utility in most cases, and so the "period correct" aesthetic would be something akin to the original crowned fork. The most serious collectors here like for every part to be of the same vintage if not true to the bike's original catalog spec and photos. Yes, everything!
Unicrown forks are a wonder of the evolution of design and modern technology applied to steel, good things for sure. But the technology to produce optimised unicrown legs wasn't yet developed when your Gitane was built.
The rake or bend of various fork legs has a lot to do with frame size. Shorter frames typically have a more relaxed head tube angle for better toe-to-tire clearance, and these bikes need more fork leg offset ("rake") to adjust the "trail" dimension for neutral handling. This change in head angles often appears between frame sizes 53 to 55 or so. If you find a fork with a 240mm steerer, it will likely have somewhat less rake than an average fork for a 54cm (or smaller) frame.
I've got a couple of early '70's TDF's, a green 54 and a white 58cm. They ride great!
Note also that it is crime in some circles to cut off the unused derailer hanger. Don't do it!

Ex Pres 

I just prefer either the classic crowns or even sloping crowns. Tigged unicrowns just don't do it for me, but I'm old - just ask my daughter.

adamant628

Unfortunately, I won't be keeping this as an original, but I'll try not to destroy anything.