Bicycle Mechanics - Chain width 3/32". What about external width?

I read somewhere that 3/32" chains may have different external width. Is it possible? If it is, how can I guarantee that I bought the right one? My chain insists on keep rubbing the previous crank on the cog (on 4th gear, it rubs the 3th and so on), as if it was to wide. At some speeds, it tries to jump. Any ideas?

I read somewhere that 3/32" chains may have different external width. Is it possible? If it is, how can I guarantee that I bought the right one? My chain insists on keep rubbing the previous crank on the cog (on 4th gear, it rubs the 3th and so on), as if it was to wide. At some speeds, it tries to jump. Any ideas?

What kind of bike? Chains for modern derailleur bikes will vary in width from about 6.1mm to 7.4mm. Not having the right one will cause exactly the kind of problems that you are describing.

Thank you for you reply.

I have a Cannondale Touring Bike T700.

I changed front and rear derailleur. The back one is exactly the same as the original: Shimano, 8 speeds, going 11 to 32. The front one is different (I bought from a friend that used to give bike maintenance workshops). Before I had a 24/32/42. Now I have a 26/36/46.

I don't know if it's possible, but it also seems to me that the front crank is closer to the bike center than the previous one.

Oh! and I didn't change the number of rings on my chain. (I used the Shimano instructions for chain length and It didn't seem to be necessary).

There are five different chain standards: single speed (most childreds' bikes and new
old single speed adult bikes), 5-6-7spd bikes, semi obsolete and rare in new bikes,
8 spd, 9spd and 10spd. As the number of speeds go up the chain width goes down,
and spacing of the chainwheels and cassette/freewheel cogs decreases. Likewise
the width of the front der cage decreases from 5-6-7, 8-9 and 10spd. If your der
is 9spd and the set up is 8spd you may have rub on that basis. If you changed
BB axles there may be a length variance, and in rare instances (not easy to do with
a triple) the axle may have been put on backwards and shifted the CW. All of these
parameters need to be checked (chain width (8 or 9spd chain), Fr der (8 or 9spd),
BB axle length. Finally appropriate adjustment of the whole system can cause this, the cable tension, position of the F der cage vis a vis the larger chainwheel. I have identical road triples on three bikes and all have different points where the chain rubs on the cage. Steve