Replacing a rear bike wheel, what do I need to know

200GS is a bit oldschool. :slight_smile: But I found this:

200GS specs are on 59/68. Looks like the rear derailleur came in too varieties, long cage and super-long cage, the former having max sprocket size of 30T and a total capacity of 36T and the latter having a max sprocket size of 32T and a total capacity of 38T. Total capacity is difference in tooth count between smallest cog + small chainring and largest cog + large chainring. So, it looks like you’re exceeding the specified maximum but Shimano is historically conservative with those specs and if it works, it works. You’re probably also exceeding the total capacity spec because you’re probably at 40 with what’s most likely 28/38/48 rings up front, but the consequences of that are just that if you’re in small/small the derailleur doesn’t have enough wrap to keep the chain tight. Since that’s another gear you never use in practice, doesn’t matter much.

The chain tracking slightly beside isn’t a big deal. It just means that the cassette on the new wheel isn’t sitting in quite the same place as the old one relative to the frame dropouts. You can tweak the positioning of the derailleur by turning the barrel adjuster where the cable enters the rear derailleur, or if that doesn’t have enough travel, letting out/taking in a bit of cable where it clamps on the derailleur.

The derailleur should be pretty much fully stretched out in big/big. It’s not like you should ever be in that gear combination anyways.

And finally, if that spec sheet is to be believed, 200GS was freehub/cassette in 7sp configuration and freewheel in 6sp.

Yes, Sheldon was (still is, actually) legendary.

This is all absolutely true.

I’m an outlier, I guess. I can handle a lot mechanically (actually went to motorcycle mechanic school), so that’s not an issue for me. Maybe because of my mechanical background, I find Presta valves fragile and fiddly compared to Schrader valves. That’s all. I get that Presta valves are lighter, and a smaller hole in the rim doesn’t weaken it as much. I just like Schrader valves better. And most pumps are flip/flop these days anyway, so that’s not an issue.

Yeah, that’s an issue. A while back, I needed a new tube for my folding bike. 20-inch wheels, 20x1.5 tires and tubes. I went to my local bike shop, and all he had in the right size was a tube with a Presta valve that’s about 3 inches long. Clearly meant for an aero rim.

But seriously, who needs an aero rim for a 20-inch wheel? Those wheels are for either folding bikes or recumbents. Aero wheels are just silly on those bikes (well, maybe not recumbents, I guess). And a longer valve (especially when installed on a non-aero rim) seem more likely to get damaged.

Anyway, it worked. But ultimately I drilled the rims for Schrader valves.

So I finally got to ride it a very small bit. Like just out the driveway and back…


OK here is the next issue when in that largest rear gear (34), it appears the chain skips a tooth regularly. It appears that the spacing of the chain does not equal the spacing of the gear.

The front cog set is Shimano Biopace SG 28 38 48.

Are they incompatible? Or perhaps chain stretch - the bike is well used and the chain is most likely up there in miles. The front cog says for narrow chain only.

Are you cross-chaining it when this happens ?

Probably a stretched out chain. Nominal length of a chain is precisely 1" per full link. Measure 12 links. If you’re over 12 1/8" inches you’re into replacement territory. If that’s the original chain it could easily be substantially worse. When they get stretched out, they wear in the rear cassette in such a way as to work together, but replacing either part without the other will result in skipping.

Do make sure a new chain is for 7sp drivetrains. A chain meant for a modern 11sp won’t work. 7sp stuff is still commonly available though. 6, 7, and 8sp all take the same width chain. 9-12sp stuff needs progressively narrower chains.

Assuming the rear cassette is 7sp, it’s looking for the same width chain as the front (unless someone has replaced one or more of the front rings with improper pars I guess). None of your stuff is “narrow” by modern standards. Narrow in that context means a 3/32" chain and not a 1/8" chain which is the standard for single-speeds and BMX. Note that 3/32 and 1/8 are nominal widths of the roller (the round bit between the side plates) in this case and not what you’ll measure if you stick a ruler across the width of your chain.

I ordered a chain for 7 speed, and tool for that, and caught a youtube vid on chain sizing, so I think I’m pretty good with that.

Also I did get out on a small ride, staying away from that larger rear cog till this is resolved and it’s turning out to be a nice ride. I am thinking of replacing the rear cantilever brake with a v-brake (which I have). Any reason not to?

No, it happens on the largest rear ring no matter what front cog it’s on.

But I do admit that much of my former biking experience is trail riding and from that I have tended to leave the front in the lowest gear and just use the back, unless I run out of gear and have to shift the front (such as downhill sections). Doing more road/rail trail biking I am gradually learning to use both.

The brazed-on mounts for cantilevers might not be in the same place they’d have to be for V-brakes - measure everything out and see before doing anything irrevocable. Also, the levers are different – they pull different amounts of cable.

I’m not sure what would be improved by replacing the cantilever brakes, anyway – cantilevers should work just fine.

New chain went on and had to adjust the rear derailer, everything is working as it should, even small small or large large. So time for a ride.

My feet can hit the rear brakes, these stick out further then v-brakes. But since different cable lengths are pulled, I’m putting that one on the back burner.

You can find low-profile cantilever brakes that won’t require a lever change. That might solve the foot/brake contact issue.

Clipless pedals ?

If so, this may be fixable with a small adjustment, moving the cleat on the shoes a skosh rearward (which, in turn, shifts the shoe slightly forward relative to the pedal/bike).

Thanks but not ready to make the move to become one with the bike yet, still standard peddles.

Thanks, was trying to use what I have instead of buying more items - however I just used that extra v-brake on my son’s bike. Nice to know the options.