Tuesday, July 8, 2008

Low Trail 650B Conversion Forks Have Arrived

I received a shipment of these today from Kogswell. The forks have a 1" unthreaded steerer, which can be threaded upon request. The intention is for these forks to be used on road bike conversions to allow 1) low-trail steering geometry 2) wider tires and fenders than stock forks on conversions would likely allow and 3) good fender and rack mounts. The finish is raw. Fork rake is 64mm, which--assuming a 650B-ish wheel diameter of 660mm, yields the following trail measurements.

40mm with a 72 degree headtube angle
37mm with a 72.5 degree headtube angle
34mm with a 73 degree headtube angle
31mm with a 73.5 degree headtube angle
28mm with a 74 degree headtube angle

If you've converted an old road bike to fatter 650B tires but still have high trail steering geometry you're only getting half the joie. With fat tires, a front load, and a low-trail front end you can see what all the Frenchy fuss is about.

For those unfamiliar with the P/R forks, I've included some pictures below. They have double eyelets on the dropouts, mid-fork braze ons for low rider racks, and threaded fender mount underneath the fork crown (very handy), and braze ons on the top of the fork crown for rack Kogswell is developing specifically for the fork. The fork crown affords room for a 50mm fender. I've put both Gran Bois Hetres and Panaracer Fatty Rumpkins under a 50mm fender of this fork. Both fit, the Rumpkin was a little tighter than the Hetre.

Forks are $65. Shipping is $10 to the continental United States. I can have the forks threaded for $40, but I need to know the exact length of the headtube (plus any spacers you plan on using) for the bike the fork is destined for. I also can ship the fork directly to a good powdercoater or painter if you don't have one in your area.

Keep in mind 1" threadless headsets and stems are readily available, so don't dismiss the idea of changing your setup to threadless. The steerer tube on these forks is huge (400mm), so you won't have any problem putting your handlebars wherever you'd like should you decide to go threadless.

For those that can't wait for the Kogswell front racks I haven Nitto M-12's for $60.





19 comments:

Bradford said...

Do the Kogswell 1"forks have enough distance between the dropout and the crown race or brake/fender hole in the crown to be used with a frame originally designed for 27" wheels
with significant clearance ?
(Fuji Delrey circa 1989)

Jim G said...

Hi Anthony,

I think I already know the answer to this, but will these forks accept a Tektro R556 caliper brake with a 650B wheel? Thanks!

Jim G said...

Also, what's the axle to crown measurement? Thanks again!

Phillip said...

Hi Anthony,

Would this be more stable with a front load than the stock fork on my Bleriot?

Phil

Longleaf Bicycles said...

Bradford--I don't understand your question exactly. Are you asking about a clearance issue on the fork with 650B wheels, 27" wheels, or about how the fork might change the geometry of the bike?

Jim--I'll take those measurements tomorrow and get back to you. I've put a Tektro R556 on P/R fork before, so I'd be surprised if that had changed.

Phillip--Simple anser is yes. Longer answer is that your bike has a slack headtube angle that isn't ideal for front loading and will mitigate the low-trailness of the fork. Remind me what size Bleriot you have and I'll tell you what your current trail is and what it would be with one of these forks.

Longleaf Bicycles said...

Jim,

360mm axle to crown, and the Tektro R556's will work.

Phillip said...

Anthony,

51cm Bleriot. Thanks.

Phil

Longleaf Bicycles said...

Phil,

Looks like all sizes of the Bleriot have a 71 degree headtube angle. That gives you 61mm of trail with the standard fork. The P/R conversion fork would lower it roughly 46mm. (Roughly because the fork would probably drop your front end a tiny bit and steepen your headtube angle, further decreasing the trail.)

Anthony

Jim G said...

Anthony, how do we order? Do you accept Paypal? Thanks!

Longleaf Bicycles said...

Jim,

I accept PayPal, Visa and Mastercard (call me) Checks, Money Orders . . . these days I prefer gold as a hedge against the weak dollar but you get the picture. Unthreaded is $75 shipped. Threaded is $115 shipped. Just let me know where to chop it if you'd like it threaded.

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Anonymous said...

Hi, I would like to convert a 80s MTB to a 650B and have question!
Actual axle to crown measurement for the 559 unicrown fork is 393.3mm (15.5 in), and the Kogswell 650B Konversion Fork is 360mm, thats a 33.7mm difference (1.33in), how will it affect handling? theoretically i would have steeper angles!

Jim G said...

Axle to crown-race-seat on these forks is ~375mm. 360mm is the measurement from the axle to the _bottom/underside_ of the crown.

I wouldn't use one of these forks on an MTB. Besides, they're all sold out anyways.

Anonymous said...

...so would it be wise to use drum brakes with the original fork!
Question: Is a 559mm MTB conversion to a 584mm single speed viable?

Jim G said...

"Question: Is a 559mm MTB conversion to a 584mm single speed viable?"

I've seen a few Surly 1x1s set up with 650B wheels, so I'd say yes.

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