I tried searching but really I don't even know the lingo, are freewheels of the same gear range since the mid 90's all standardized? I'd really love to get my freewheel on my old mtb bike swapped to a 14-34 or similar since getting a t-a-b for my son. my wheelsets are at the not so LBS and was thinking tonight about getting them to put one on and grabbing a new chain too, I would prefer not to sound uninformed when I call tomorrow if at all possible lol.

Brit -Jpn are same thread.. as
LH BB.. fwiw, .. 1.370", ... French, as is their way, in the past, were different .. metric..

now the removing tools vary widely amongst manufacturers..

hehe, I don't plan on doing the work, just going call them and say hey if you have a shimano 14-34 in stock put that on while you have it. ty ty for the info.

Anything but old French bikes take the same "English" freewheel threads and these are by far the most common. Any Shimano, Sun Tour or Sun Race freewheel will fit.

As the others have said 99% or more of the freewheels you're likely to encounter have the same thread. But there are subtle differences between brands that can affect fit.

The chief one is the position of sprockets with respect to the back of the freewheel body (where it meets the hub's shoulder). This difference which may be as much as 2mm can change clearance between the freewheel and spokes on one side, or the frame on the other. It's not a major issue, but might cause you to have to respace the axle to compensate.

blah well they haven't got one in stock, I changed one out 15 years ago I guess I can do it again. I am so not driving 45 mins down there in a week to loose my bike for 2 days again lol, thanks for the info though.

Did .you have them order one from their wholesalers ? . not everything made
is stocked all the time everywhere..

One item not mentioned is the incompatibility between Suntour Ultra freewheels and standard spaced freewheels (including Suntour). The Ultra 6 was designed to use an Ultra chain and fit on a hub and bike with standard 5-speed 120mm spacing. (Standard 6 spacing was 126 mm.) There was also an Ultra 7 that would fit on standard 6 speed spacing.

There's a big problem, if you have an Ultra 6 on a 5 speed hub and try to replace it with 6 speed freewheel with standard spacing.

well the issue is, I have to drive down there, 45 mins if the traffic and weather is nice, today was an hour flat. so tach on 20-25 bucks in gas (because they don't do much same day, they are the only fully operating bike shop in the area, and they cover the college market and stay pretty busy, took 48 hours for 4 wheels to be tensioned and trued) for that, they were charging 30 bucks for a freewheel, plus 10 to put it on, which is ok, but, I can order one and a parker shimano tool for the cost for the part, and not have to spend the gas money, or give up 2 days for 30 mins work... if they had it in stock and the things were there, it would been fine, i didn't really care to spend the extra money since they were there but i surely only bother to make the trip once in a while and I only take my wheels once or twice a year. I have done one before, years back, and I can do one again since its pretty clear they are all the same as far as what I'm doing and I am going from shimano to shimano.

Ultra 6 could be used on standard 6-speed spacing (126 mm). You had to adjust the rear derailleur's high limit screw and use the narrower chain but it did work. "Ultra 7" actually is the standard 7-speed spacing for both freewheels and cassettes.

1st; what is currently on the bike?
if it is a 7 speed freewheel, with Shimano removal tool features (Shimano, Sunrace, other?) everything is easy.
if not, things get trickier.

Removing a freewheel takes a fair amount of strength. I clamp the tool in a heavy bench vice, then put the whole wheel (with tire) on the tool, then TRIPLE check that I am trying to turn it in the correct direction.

Amazon has a large selection of freewheels and cassettes. Personally, I am moving away from the 14-34 to a 13-28 for my commuter. the jump from 34 to 24 teeth is too much. I also currently have a preference for Sunrace freewheels. The last Shimano that I got had the 5th sprocket mis-aligned. I could align the derailleur to work smoothly in 1,2,3,4,6 & 7 or in 5.

I'd be buying tools from the shop...