Fork crown for 58 - 62mm fenders

[John Clay]

The widest crown available on the Compass website is 53mm yet the 650b fenders range from 58 to 62mm. How are folks handling that....denting their front fenders (substantially) so that they fit between the fork legs, or is a wider crown available somewhere? I can fabricate a wide, flat plate crown for an upcoming frame, but I'd rather not.

Thanks,
John Clay
Tallahassee, FL

[Alex Wetmore]

Framebuilders might be a better place to ask...

58-60mm isn't so hard.  You can get a variety of sloping CX fork crowns in that width that aren't so pretty, but are light and very functional.  You can also find NOS Pacenti PBP (58mm?) or MTB (72mm?) crowns.  And there is the oversized Nova crown if you want to go wider and are okay with the limited fork blade options.

It would be nice to see more and better options in >60mm crowns, especially now that the Pacenti MTB crown isn't being made any longer.

alex

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From: 65...@googlegroups.com <65...@googlegroups.com> on behalf of John Clay <nice.c...@gmail.com>
Sent: Tuesday, October 18, 2016 7:53:23 AM
To: 650b
Subject: [650B] Fork crown for 58 - 62mm fenders

 

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[Mark Bulgier]

Cinelli made an MTB crown in the '80s that I used a few times, with a fender space of ~67 to 70 mm depending on whether you measure to the tangs or the blades (70 mm if your fender hits below the tangs).  It's heavy and ugly but I machined it down to an acceptable weight and look.   Ceeway sells a knock-off, made by Long Shen or Everest I bet, that seems to be a pretty faithful copy of the Cinelli.  Ceeway says 68.7mm wheel clearance.  This is the Cinelli:

The extra material around the steerer under the main "plate" of the crown is too goofy looking for me, and it requires the fork blades and overall fork height to be longer, in order to get decent clearance under the crown, so I would cut that off. 

I also lathe-turned mine down from the top, increasing the angle of the slope so the extra weight tapers down as you get farther from the steerer -- little to none removed near the steerer. 

On the one in the photo, I built up some brazing material (nickel-silver in this case, high strength and a bit higher melting point than brass so it won't remelt when I braze the blades in.  That allowed me to shape the bottom of the "plate" in a more pleasing way to more or less match the slope on the top.  Look for the nickel-silver in the detail photo below; it's been sandblasted, so it's a subtle color change. You can see the remnants of the steel webs in the original, mostly machined away though some of the web still is there hiding under the nickel-silver.

I assume you could do the same with the knock-off that Ceeway sells.  Maybe too much work, but I know you're a hobbyist so maybe you enjoy finicky custom work like that.

Then there's the Bob Brown crown, a very interesting bit of CNC machining to make a faux-2-plate look.  I bet it's very strong though I have no way of knowing.  It's 73 to 76 mm fender clearance depending on whether you measure to the blades or to the tangs.  See it here: http://bobbrowncycles.blogspot.com/2007/01/theyre-here.html  I got one from him maybe a year ago so hopefully he still has some.

Mark Bulgier
Seattle

[Alex Wetmore]

That crown looks a lot better after your redoing of it Mark.  It always came off to me as seeming pretty wimpy looking though, it's almost like a singleplate crown which seems like the wrong concept for a bike wearing fat tires and probably being ridden on some rough roads.

I forgot about Bob Brown's CNC crown.  It is a cool piece of machining work, I'd love to see how that is fixtured during the CNC ops.

alex

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From: 65...@googlegroups.com <65...@googlegroups.com> on behalf of Mark Bulgier <ma...@bulgier.net>
Sent: Tuesday, October 18, 2016 2:00:47 PM
To: 650b
Subject: [650B] Re: Fork crown for 58 - 62mm fenders

 

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[Chris Cullum]

The wider Toei fork crown fits 58mm Honjo fenders perfectly.

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[Mark Bulgier]

I raced MTB Cross-Country on that crown for a few years, expert class and even a couple races as a "Pro" (my license said Pro but nobody was paying me). I rode it on the Crested-Butte-to-Aspen ride over Pearl Pass, and all the "Gonzo-Abusive" rides in the early Moab Fat Tire Festival, and I rode stuff that everyone else got off and walked.  I was never the fastest guy on the downhills but I did win a couple races, so not too slow.  Even in my racing days I was heavier than most racers, but I didn't "air it out" much -- tried to keep my wheels on the ground.  But you can't ride the big Moab rides without going over some 3 foot dropoffs.

I'll agree this crown is perhaps too light for landing the really big jumps.   Maybe think of it as more for cyclocross type off-roading and touring than what most people think of as MTB these days.  But of course all that Red-Bull, X-Games type stuff is done with long-travel suspension forks, so anyone thinking of a rigid fork is probably not landing huge jumps.

I still have that bike, though I haven't ridden it in a long time.  I think it's strong enough.

-Mark

[John Clay]

Chris,

I'm puzzled. How does a 60mm fender fit into a crown that's supposed to be 53mm between the fork legs?

Thany you all for the tips.

John

[Chris Cullum]

On my MAP Randonneur, the 58mm Honjo fender slides perfectly between the fork blades matched to the Toei fork crown with zero crimping. The fork spacing at the outside of the fender is almost exactly 58mm.

[Mark Bulgier]

I have a pair of Honjo "hammered" 650b fenders that have had a slightly rough life and they measure various widths at different places, but enough of them are in the ~58 mm range that I believe that might be what they were made to.  They are exceedingly easy to "adjust", including accidentally.  Definitely bendable in your bare hands.

I also have the Compass crown and it really does measure 53 right where the blades emerge, but then the blades start to spread out on their way to rendezvous with a 100 mm hub.  The wide part of the fender is some ways down below the crown, so the blades have had time to diverge a bit.

I put some Toei special Kaisei blades in one of those crowns and spaced the bottom ends right for a 100 hub, best as I could estimate where the final cut will be.  My ~58 mm fender didn't slide in completely without touching, it appears to hit at a point where the fork blade width is about 57 mm.

But even if I'm right and there is 1 mm of interference twixt the blades and the fender, that would be very easy to deal with.  I'm going to call it so close to perfect that we might as well call it perfect.  Even if your fenders are 60 mm over most of their length, they'll be easy to squish down to 57 or 58 briefly there at the crown, and you'll never notice.

Long way of saying, I agree with Chris.

-Mark

Chris Cullum wrote:

On my MAP Randonneur, the 58mm Honjo fender slides perfectly between the fork blades matched to the Toei fork crown with zero crimping. The fork spacing at the outside of the fender is almost exactly 58mm.

On Oct 18, 2016 22:33, "John Clay" <nice.c...@gmail.com> wrote:

Chris,

I'm puzzled. How does a 60mm fender fit into a crown that's supposed to be 53mm between the fork legs?

Thany you all for the tips.

John

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[John Clay]

Hi Mark,

Thanks a lot for doing that. My gut didn't expect the fork leg divergence and fender location to make that work. 

I'm eager to finally get around to building a 584 x 42 rig for myself when I get back to Tallahassee (in SF for a bit) and I'd like to use an Imperial crown, hammered Honjo fenders and a set of RAID brakes I have.

John