From our shop, they do, even the £6,000 TT rigs have them (with many odd modification made to fit the seat post).
"Bespoke competition bikes (PBSR r. 3(1)(d))" are outside the rules.
http://ukcyclerules.com/2011/06/08/buying-selling-kit-new-bikes/
@hippy started
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"Bespoke competition bikes (PBSR r. 3(1)(d))" are outside the rules.
http://ukcyclerules.com/2011/06/08/buying-selling-kit-new-bikes/