Assuming it's a 40t, thats 50kmh at 90rpm on 42c tyres, I think you'll probably be fine...
I found 40T far too small so sized up to 44T which was much better (granted i have a low cadence). Running 45c Tyres
@Saffronspokes started
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Assuming it's a 40t, thats 50kmh at 90rpm on 42c tyres, I think you'll probably be fine...