I'm siding with vog here. Do not compose hashes¹. You may not think it's relevant that it degrades the security of your site, but nobody knows what consequences it will bring, so how could you know?
Impose your size limitation as a clear password rule. That means, write on your site that passwords must not exceed the 55, 255 or whatever characters, send back an error if the user tries to create a larger password.
1 - And completely avoid weaker hashes in general, it's not like a percent or two increase in CPU usage will have a greater impact on your bottom than having to adapt your software after it's out.
Impose your size limitation as a clear password rule. That means, write on your site that passwords must not exceed the 55, 255 or whatever characters, send back an error if the user tries to create a larger password.
1 - And completely avoid weaker hashes in general, it's not like a percent or two increase in CPU usage will have a greater impact on your bottom than having to adapt your software after it's out.