The comment about 15 inch or 16 inch upgrade from as little as 13 is indeed true. given the original car from oem is the standard they built. Power to weights are proprtionate for every generation of automobile in the past several decades ..that magical diameter turns out to be 24 inches or even greater if you have an engine based on work more than a ricer (ie a boxer engine, or a volvo 240 inline, or most cars today it is no problems at all in the 2+ liters). the older inlines and first transverse were very bad proprietary socilaist trgaedies that originally took over my country. The metro may be a total loser going away from thier design like a honda. They made very very bad and tiny engines be economical and that means alot of dainty things like 12 inch tires...
Here is some very useful websites:
Tire size calculator
and after getting measurements go here:
4Lo.com :: Final Gear Ratio, Crawl Ratio, Tire Size Calculators
The old subes with 1781s love the big treads. A 1.8 or less in an inline config is very very sensitive. A metro owner could help alot more with thier own experience.
