PIAA Si-Tech Flat vs Bosch Evolution

We score blades from 1 to 10 overall and on each part using evidence on the page, not impressions. The typical blade in our catalog scores 6 on every part, so scores show how a blade compares with that baseline. Scores of 7 and up are strong, 6.5 to 6.9 are good, 5.5 to 6.4 are middling, and under 5.5 are weak. We do not use store star ratings because they bunch between 4 and 5.

From Reddit, car forums, YouTube, and store reviews, we count praise and complaints on wiping, noise, winter use, fit, and whether blades last six months. Each time a blade's ratio of praise to complaints doubles compared to a typical blade from that same mix of sources, it gains a point and a half, and it loses a point and a half each time it halves. Store reviews must reflect a month of use before counting toward wiping, noise, or winter use, though fit counts right away. Small numbers of reports are pulled toward 6, and topics with differences no greater than chance get counts but no score.

A blade needs at least 15 owner reports or two scored tests to get a score. Published tests count by finish and score, with lab and club tests weighted highest, followed by magazines, and then shops or affiliate sites, while older tests count less. To find the overall score, we weigh tests the most, followed by clean wiping and lifespan, then noise, winter use, and WiperFinder reviews, and finally fit. Parts with more reports carry more weight, and the verdict's first line shows the share of positive owner reports.