Andym

I want to install tires from Costco they won't allow anything taller than stock 195/60/15.
I've had 205/65/15 since last time and I wanted 195/70/15 which is taller and also cheaper and it does better mpg on highway at lower RPM.
I need long lasting 80,000miles good lower cost tire that will last, I do full time Ubereats on my Honda Civic 2005 lx, only car I have had since 0miles.
I was also worried if taller tires might damage the transmission? Hi and Thanks a bunch you people

FRSam

Use a tire size calculator. Anything within 3% is fine. Costco will install anything within 3% of the stock tire size, which is 195/60/15.
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https://tiresize.com/tyre-size-calculator/

Run your tire size through that, and it'll give you a variety of other sizes you can use.

If you stay within that percentage, your transmission will be fine.

Also, I saw your post on a different thread. Costco will swap tires other than 195/60/15, but they need to be within the spec ratio, which the tires you had on before were not. The 205/65/15 are off by more than 5% and the 195/70/15 are off by more than 6%. For example, Costco will swap a 205/55/15 or a 185/65/15. I brought in a set of 17's and they were more than happy to swap 195/45/17 onto the same car. If anything, you were doing more damage to the transmission on your older tires.

BrotatoChip

Won't really do any damage to the transmission but it would make your speedometer and odometer incorrect if using a size not within ~3% of original.