Conversion 26 to 650B - Jamis Dakota

[bdu...@gmail.com]

Had trouble finding the right frame with a horizontal top tube but got hold of this nice Jamis Dakota - probably 1990 - in Tange triple butted tubing.

Build in a 2x7S guise

Nearly full Shimano XT M730 and a nice Nitto bullmoose

Tektro cantilevers CR72 are Ok ( in the back - its Ok but just)  to compensate the heightened rim.

Bruno 

Paris, France

[David Hays]

Nicely done Bruno.

David Hays

Buffalo, New York USA

On Aug 1, 2021, at 12:51 PM, bdu...@gmail.com <bdu...@gmail.com> wrote:

Had trouble finding the right frame with a horizontal top tube but got hold of this nice Jamis Dakota - probably 1990 - in Tange triple butted tubing.

Build in a 2x7S guise

Nearly full Shimano XT M730 and a nice Nitto bullmoose

Tektro cantilevers CR72 are Ok ( in the back - its Ok but just)  to compensate the heightened rim.

<20210801_154407sml.jpg>

<20210801_154456sml.jpg>

Bruno 

Paris, France

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<20210801_154407sml.jpg><20210801_154456sml.jpg>

[rcnute]

Wow, that bike is clean!  The bullmoose bars are a nice touch.

Ryan

[bdu...@gmail.com]

Thanks 

I have been waiting 15 years to find a nice frame to put them on !

and as I have been bitten by the 650B bug, its my third 26 to 650B conversion ....

found some nice 650B Super Champion NOS rims to build the wheels on black LX hubs and use my M730 parts for  the build

Bruno

[Pat Smith]

That looks great. Jamis makes a solid bike and they seem to fly under the radar. I'm in the process of doing both a flat bar and 650b conversion on my Jamis Aurora Elite touring bike (also with a horizontal TT). It could only fit 700 x 32 tires but the fork and stays are wide enough 650b x 42 fit and I'm going to even test out 650b x 48 next. I just got a cheap wheelset to try the 650b but I'm going to build a nice polished dynamo set.

[bdu...@gmail.com]

Just beware of the Bottom Bracket height. I planned to do another conversion on a vintage 700C frame but had to "back out" as it was too "touchy" for the new pedal height and risk of touching the ground in tight curves.

Bruno

[Greg Walton]

The Aurora Elite has a BB drop of 65, so no problemo. Almost like it was designed for 650B!

Greg

Seattle

Sent from mobile

On Aug 3, 2021, at 7:17 AM, bdu...@gmail.com <bdu...@gmail.com> wrote:

Just beware of the Bottom Bracket height. I planned to do another conversion on a vintage 700C frame but had to "back out" as it was too "touchy" for the new pedal height and risk of touching the ground in tight curves.

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[Patrick B. Smith]

Fortunately this bike already had a high BB (is that common for touring bikes?) and I've got 170mm cranks. Only done a few rides with the 42s and so far no issues. If I'm able to fit the 48s I'll be good to go as they are near the same size as 700 x 32.

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[Michael Wong]

If one can resist pedaling in corners, a low bottom bracket will lean really nicely

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[Erik Jansen]

That's a gorgeous build. Perfect bike for the bullmoose bars!

[etorg...@yahoo.com]

Regarding low bb on 700c wheeled bikes.... I have always thought if u can make a 42mm 650b tire fit, then bb will not change.  This comes from the following assumptions:

1.  The 700c bike was running 23mm tires without an issue.  (For older bikes this seems safe)

2.   One can calculate the overall diameter of the wheel in question as 622 plus 2x tire width for 700c and 584 plus 2x tire width for 650b.  Built into this assumption is that the tires height is the same as the width.  (Pretty true )

Using that if you can fit 42 mm 650bs, you are golden.  38mm tires will lower your bb by 4mm.  

Eli

In Albuquerque

[Harry Travis]

Rant:

I don't recall, ever, a complaint that larger frames for riders with presumably longer legs and therefore candidates for 175mm cranks were negligent in not raising bottom brackets.

I don't recall complaints in years of bike reviews about years of standard undersized 700x23 tired putting racey riders of hanging up their pedals driving through turns.

Now, it would be fair to point out that high Q cranks and wide pedals are LESS compatible with 650b conversion. I leave it to the trigonometers to graph the tradeoff in Q (or maximum outside to outside pedal width and crankarm length. 

And, it would be accurate to say that years of longer crankarms + greater average Q of cranks had shrunk the margin for pedaling through turns.  But, Eli is right, especially if your cranks are 165-170 and low Q. 

--

Harry P Travis

14.7.1

On Aug 7, 2021, at 5:04 PM, 'etorg...@yahoo.com' via 650b <65...@googlegroups.com> wrote:

Regarding low bb on 700c wheeled bikes.... I have always thought if u can make a 42mm 650b tire fit, then bb will not change.  This comes from the following assumptions:

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[David Cummings]

That’s a very beautiful build!

Forgive me, but I have to ask why you went from 559 to 584? I have a number of old MTBs in 26 and they ride heavenly with RH Rat Trap Pass or Humptulips Ridges (55-ish mm). It’s got to be the most wonderful ride on gravel I’ve ever had - like a magic carpet. Wide, supple tires don’t slow you down (yes, I’ve drank the Kool aid). I love them so much, I built up my 2015 Elephant NFE with 26” wheels instead of 650b (in 48mm which it was designed for) so I could run RTPs or HTRs (extralights of course ;). 

Just curious,

David in MT

[bdu...@gmail.com]

Hi

I suffer from 650B OCD ;-)

and , this bike is actually more meant to be an "errand bike" more than a gravel bike. Moreover, I find this wheel size more pleasing to the eye in such a frame ( and do not really wish to enter the budget territory of the RTP I am afraid .....) 

Bruno, Paris, France

[David Hays]

I just switched the crank on another of my Mercian 650B conversions because of some pedal strike.

They both could only manage 38mm tires which lowers the BB. They had been running 175 cranks and now 165mm.

All good.

David

Buffalo, New York