popefelix

I bought an old Motobecane Mirage off Craigslist a couple weeks ago. I recently took it for a ride, had a spill, and managed to bend the front fork (as I discovered when I took it into my LBS for a tune up). So I need to replace said fork. I've removed the fork, and I measured the steerer to be ~5.5", so I'm going to assume that the actual measurement is 140mm. I understand that I'm going to need a new headset (and possibly stem and handlebars) if I go with a non-French threaded fork.

I haven't had any luck finding a French threaded fork with a 140mm steerer on eBay. If I got one with a slightly longer steerer, could I have it cut down? I understand that I don't want to lose the threads. What other things should I be aware of in this process? If I replace the headset, how much of a pain in the ass would it be to install? I got the old headset out with a minimum of difficulty, but I'm reading online how you need a special press to get the bearings into the top tube.

due ruote 

How badly bent? They can often be bent back.

You can DIY the headset using a piece of all-thread with oversized washers and a couple nuts. Go slowly and do one cup at a time.

popefelix

It's bent between the steerer and the crown. Maybe also the blades of the fork.

I'm not sure what you mean here. Can you elaborate?

steve sumner

the oldest LBS in your town will have straightened 100s of forks over the years
take to them first. newer shops only know how to replace things not repair them
removing and installing headset cups does NOT require special tools even tho
it's nice to have and use them. many garage mechanics have tapped out cups
with a drift punch and put them back in with a hammer and block of wood

popefelix

I feel like I could put the bearings back in with my fingers and not have to press at all. It didn't take any effort to get them out. Is that something to be concerned about?

steve sumner

we're not talking about the bearings themselves but the cups they sit in
which are press fitted into the frame. this is only if you need to replace
the whole headset which you do not as long as you replace your French
fork with a French fork

popefelix

OK, I think I understand. I was going to attach a photo, but the forum won't allow it. If you go to https photos.app.goo.gl/cbHkLc1BWwtRKApa7, though, you can see all the photos I have, including the disassembled headset.

madpogue 

Is a Motobecane certain to have French thread headset? I thought their export bikes had English thread.

nlerner

I pulled this fork off of a wrecked curbside Moto. Steerer measures 160mm from crown to top, but there's plenty of threading for it to work with a smaller frame and be trimmed a bit. Chrome is fairly shot, but it's straight and you can have it for the cost of mailing from zip 02446. I believe it's French threaded but can confirm.

popefelix

Thank you so much! Once I get it I'll post a picture after it's installed.

popefelix

Sad to say that nlerner's fork that he sent me would not work with my headset. So my options now are to find another fork or to find another headset, and I think the latter is going to be far easier than the former. How do I get the headset cups off of the top tube?

madpogue 

What does "would not work" mean? What _does_ happen when you try to use it?

popefelix

The headset nuts won't thread on to the steerer tube.

nlerner

Yeah, likely a French/English incompatibility but not clear which is which!

popefelix

I think the original is French, because it has a flat section that goes down the threaded portion. The one you gave me has a small square channel down the middle.

madpogue 

The flat vs channel interface for the lock washer is unrelated to the type of thread. I've seen plenty of "English" threaded forks with flats for the lock washer.

So nlerner sent you a French-threaded fork, correct? That's why I asked the question in post # 8. Others with more experience could answer better, but AFAIK, a French _brand_ of bike does not necessarily mean it's French _threaded_. First thing you should do is try the top race or locknut from your old fork on a "standard" threaded fork. If it fits, you have a lot more options for finding a replacement.

popefelix

Not having ready access to a "standard" threaded fork, I planned on buying a cheap threaded headset from Amazon and trying it on both the old and new forks. That should accomplish the same thing, shouldn't it?

gugie 

Yep, that seems to be the way to go.

camjr

I would still start with a long established bike shop that has experience in older bikes and have them take a shot of "adjusting" the bent fork and build it back for you as the earlier post suggested. I would think that Kansas City would have a couple of shops that could do that work for you.

madpogue 

^^^^ Or if you're going to go to a bike shop, just bring the top race from your existing headset in, and see if it will fit some old non-French headset they have lying around.

randyjawa 

Ebay, all chrome plated and NOS. They are not expensive and available all the time for 27" or 700c wheels. I have been looking myself for a fork for my old Torpado.

JohnDThompson 

If the lower race is in good condition, there's no compelling need to replace anything but the upper parts. If you're lucky, an ISO/English threaded cup will work with the present upper race, so you wouldn't need to do anything beyond trimming the steer tube.

popefelix

So just for ****s and giggles, I measured the thread pitch on my old fork with my calipers. I got 24 tpi. So I don't know what I have going on. I'll know more when this cheapo headset gets here, though. *sigh*

popefelix

Not wanting to wait for Amazon, I decided to go to an LBS - Bike America in Lee's Summit, MO. There i discovered that a headset that would fit would be a Tange-Seiki Passage, which apparently is a JIS headset. This gives some credence to my theory that the original fork is French threaded, and suggests that the replacement fork I got from nlerner is ISO (same TPI as JIS). So why JIS instead of ISO? My crown race ID is 27mm.

popefelix

So I have the headset. Good news! It threads nicely onto my fork. Bad news! It doesn't work exactly the same as my old headset.

My old headset had cups at top and bottom.


The new one has a cup at the bottom, but a cone on top.



This is a problem because the bearing cages don't sit right on top (judging by the different feelings of the old headset and the new) without the cone. Can I jury rig something, or am I going to have to replace the top cup?