▁ ▁At ▁the ▁same ▁time , ▁two - w heel ▁stream lin ers ▁require ▁a ▁way ▁to ▁stay ▁u pr ight ▁when ▁stopped ▁and ▁at ▁very ▁low ▁speed , ▁and ▁are ▁more ▁sensitive ▁to ▁blow ing ▁over ▁in ▁cross - w inds . ▁ ▁These ▁factors ▁limit ▁the ▁use ▁of ▁stream lin ers , ▁despite ▁their ▁aer od ynamic ▁advantage . ▁ ▁The ▁fair ing ▁on ▁a ▁vel om obile ▁sometimes ▁makes ▁it ▁more ▁subject ▁to ▁cross - w inds ▁than ▁a ▁similar ▁un fa ired ▁cycle . ▁ ▁The ▁effect ▁of ▁cross - w inds ▁is ▁complicated ▁because ▁the ▁force ▁of ▁the ▁wind ▁can ▁act ▁as ▁a ▁ste ering ▁force , ▁as - if ▁the ▁r ider ▁had ▁tried ▁to ▁ste er ▁the ▁cycle . ▁ ▁" W ind ▁ste er " ▁can ▁be ▁a ▁safety ▁issue ▁and ▁may ▁also ▁hurt ▁performance , ▁as ▁a ▁ser pent ine ▁path ▁is ▁longer ▁and ▁thus ▁slower ▁than ▁a ▁straight ▁line . ▁ ▁Thus , ▁a ▁design ▁with ▁inferior ▁aer od ynam ics ▁may ▁be ▁better ▁overall . ▁ ▁For ▁example , ▁it ▁is ▁common ▁for ▁time - tri al ▁b icy cles ▁to ▁use ▁a ▁solid ▁disk ▁rear ▁wheel ▁for ▁best ▁aer od ynam ics , ▁and ▁a ▁sp oked ▁front ▁wheel ▁that ▁has ▁worse ▁aer od ynam ics ▁than ▁a ▁disk , ▁but ▁is ▁less ▁likely ▁to ▁ste er ▁the ▁b icy cle ▁in ▁a ▁cross - wind . ▁ ▁Vel om obile ▁fair ings ▁have ▁analog ous ▁concerns , ▁leading ▁to ▁trade