Tires: tyres, rim diameter, tire failure

Question
Hello. can you please tell me if we can safely use a 205 55
R15 91v instead of a 205 60 R15 R91. Also is it safe to use 91H instead of 91V. the manufacturers here tell us that the speed rating is the same for both,  but I had read somewhere that 91V is far superior to 91H. Please guide

Answer
Moni,

There's quite a bit of confusion in your question.  The first part is about the size.

A 205/55R15 has a lower load carrying capacity than a 205/60R15 and that increases the risk of a load related tire failure, which sometimes has tragic results.  That alone is enough to say this is not a good move.

But 205/55R15's don't come in 91 Load Index - but 16" 205/55R16's do!  Also 205/60R15 do indeed come in 91 Load Index, but so do 16" 205/60R16!  So there is a problem that I can't figure out.

Which rim diameter do you have?  Further 16" tires do NOT fit on 15" rims and 15" tires do NOT fit on 16".  So if you have that situation, what you've suggested will not work.

Then the speed rating thing.  V speed rating is higher than H - and the tire manufacturers will NOT say they are the same.  I suspect the tire dealers are saying this - and they are wrong.

So let's start with the sizing issue and figure out that issue first!