Bike Check – Kirk Pacenti’s Original 650b Mountain Bike


As one of, if not the pioneer in the resurgence of 650b wheeled mountain bikes since their disappearing act in the early days of mountain biking, Kirk Pacenti has been an advocate of the middle sized wheel since 2004. After failing to get any major tire brands on board, he set out to make his own 650b rubber. While the wheel size was initially a hard sell, as you know 650b has arrived in the industry in a big way. Since then Kirk has expanded his offerings from to include 650b tires, wheels, and a number of frame building materials for bikes of all sized wheels.

Check out his original 650b rig he made himself, after the break!



As one of Kirk’s local shops, River City Bicycles in Chattanooga, TN gets the privilege of seeing what Kirk is working on from time to time. Thanks to RCB’s owner, Ronald Driver who shared the pictures with us, we can check out the bike that started a revolution. First shown at NAHBS in 2007, Pacenti set up a raffle to give away the bike in order to raise funds to make more 650b tires (the tires on the bike at the time were hand sewn from 29er tires). But at $100 a ticket, no one entered the raffle so Kirk held onto the bike.

Built as a 19″ Titanium frame, the bike has a 72° HTA/STA, a 24″ top tube, and 17.25″ chain stays. Kirk says he would have liked shorter stays, but since they didn’t have a wheel or tire available to double check the clearances, they gave themselves some extra room. According to Kirk, “The 72° HTA sounds strange by today’s standards, and I probably would not build a frame like that for a customer, but I have been riding this exact  same geometry for 20 years. It works for me, and I like hardtails with razor sharp handling. My other bikes have much slacker HTA’s, and they are probably better ‘all round’ bikes, but this one is a lot of fun.”


The bike was first built with the first ever crop of 650b parts – a White Bros. Magic fork, and Cane Creek wheels that you couldn’t buy. Over the years, the components have been updated with a Manitou Minute fork, prototype Pacenti handlebar, prototype 1x chainring with 9 speed XT group, and Hayes El Camino brakes. Some parts, like the headset, seat post, and saddle are original to the bike.


Things have come a long way for 650b since the bike was first shown in 2007.



Of course the bike now rolls on Pacenti tires and wheels. A Pacenti CL25 wheelset is wrapped in Pacenti Neo-Moto 2.3″ tires.

Thanks to both Ronald and Kirk for helping with the story!


dgaddis - 11/14/13 - 1:05pm

FYI his new website is

Gary Lee Cooper - 11/14/13 - 1:13pm

What about Geoff Apps? 1979 I think it was … for 650b.

Zach Overholt - 11/14/13 - 1:22pm

@Gary Lee, there were a number of 650b bikes before Kirk’s. Referring here to the resurgence of the size.

phil - 11/14/13 - 1:39pm

People can’t seem to commit to cutting down a steerer tube…

mudrock - 11/14/13 - 8:11pm

phil – this bike was to be awarded to the winner of the raffle, so he/she gets to cut the steerer to suit.

Jak0zilla - 11/14/13 - 9:46pm

Measure twice, cut once! It is hard to make the commitment.

Steve M - 11/14/13 - 9:51pm

I have been running a set of 2.3 Neo Motos and love em.

stratosrally - 11/14/13 - 11:59pm

Panaracer made the Pacenti Neo-Moto 2.3 tires that came on my Haro Beasley 1×9. Very good quality tires, long-lasting too. Loving my bike even to the point of keeping its rigid steel forks!

Sam - 11/15/13 - 12:36am

I’m waiting for someone to revive the 27″ 630 ISO wheel/tire size.

WannaBeSTi - 11/15/13 - 9:08am

Kirk changes his stem, handlebar, and his position a lot. He educates himself on how different setups change the characteristics of a bike’s handling.
So, looking at it that way, he’s quite smart NOT to cut his steer.

Dominc - 11/22/13 - 4:20pm

Sam, as somebody who deals with lots of old Raleighs and Peugots, i don’t think ‘revive’ is the right word. Maybe a couple more rim options, so the higher end tourers don’t have to feel like second class citizens i guess.

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