Disc Brake Forks

[mickeg]

Is this fork usable on the Nomad MK2? The website separately lists the (non-disc) Nomad MK2 fork with a MK2 designation.

Thank you.  Now I know that I was not the last person to learn that they now make a disc comparable fork.

[mickeg]

650B rims for rim brakes are apparently still available here in France :

http://www.xxcycle.com/rim-ambrosio-keba-650b-silver-confreriale,,en.php

Same model as I got, quoted tyre size 28 to 62 mm, IMO best with about 35 mm but works OK with 50mm.

Thank you for saying "quoted tyre size" instead of repeating the range as fact.  From its ETRTO sizing, that suggests an inner width about 19mm.

I never trust rim manufacturers anymore when they cite a tire width for their rims.   A few examples below:

 - Ryde Andra 30 - Inner width 19mm - Recommended tyre widths: 28 to 62 mm
    https://www.sjscycles.co.uk/rims-tape/rigida-andra-30-26-559-mtb-rim-rohloff-drilling-black-32-hole/?geoc=US

 - Mavic A719 - ETRTO suggests inner width is about 19mm but I measured mine at 20mm - Recommended tyre widths: 28 to 47 mm
    https://shop.mavic.com/en-be/a-719-j24400.html#1028=3283&1035=3501
    I used this rim on my Long Haul Trucker with 37mm tires, now use it on my rando bike with 32mm tires.

 - Velocity Dyad - Inner width 18.6mm - Optimal Tire Width: 25mm - 38mm
    http://www.velocityusa.com/product/rims/dyad-622
    These are going on my new build, initially with 37mm tires.

When all these tires with the 18 to 20 mm inner widths have such varying recommended tire sizes, I think that the marketing departments at those tire companies are in charge of writing specifications.  I can say that my Andra 30 rims are clearly too narrow for a 57mm tire, which is the tire that I usually ride on my Nomad with those rims.  Yet at 57mm, it should work great because Ryde says the rim is good for up to 62 mm.

I prefer the chart near the bottom of this page for determining which tires fit which rims.
http://www.sheldonbrown.com/tire-sizing.html

When I built up my Sherpa, I planned to use tires in the 37 to 50 mm range.  Thus, from that chart I went shopping for a tire that had an inner width of about 21 or 22 mm.  I bought the Salsa Gordo (now discontinued) and I measured that rim at 21 mm.  Great rim, I wish I could still buy them.
http://salsacycles.com/components/archive/category/rims/gordo_26

[George Hetrick]

Thank you.  Now I know that I was not the last person to learn that they now make a disc comparable fork.

Always happy to be of help 

[martinf]

- Ryde Andra 30 - Inner width 19mm - Recommended tyre widths: 28 to 62 mm
    https://www.sjscycles.co.uk/rims-tape/rigida-andra-30-26-559-mtb-rim-rohloff-drilling-black-32-hole

I can say that my Andra 30 rims are clearly too narrow for a 57mm tire, which is the tire that I usually ride on my Nomad with those rims.  Yet at 57mm, it should work great because Ryde says the rim is good for up to 62 mm.

The Andra 30 rims work OK for me with 50mm tyres, but I reckon wider rims would be better for this size of tyre (Andra 40 or similar). But my Andra 30 rims are CSS, so they should last a very long time before I need to replace them.

[mickeg]

- Ryde Andra 30 - Inner width 19mm - Recommended tyre widths: 28 to 62 mm
    https://www.sjscycles.co.uk/rims-tape/rigida-andra-30-26-559-mtb-rim-rohloff-drilling-black-32-hole

I can say that my Andra 30 rims are clearly too narrow for a 57mm tire, which is the tire that I usually ride on my Nomad with those rims.  Yet at 57mm, it should work great because Ryde says the rim is good for up to 62 mm.

The Andra 30 rims work OK for me with 50mm tyres, but I reckon wider rims would be better for this size of tyre (Andra 40 or similar). But my Andra 30 rims are CSS, so they should last a very long time before I need to replace them.

At high pressures the 57mm tires work pretty good on Andra 30 rims, but not at lower pressures.  I had to run much higher pressures in my 57mm Marathon Extreme tires on some very rough roads in Iceland last summer than I wanted to run them at.  After that I started giving serious consideration to replacing my CSS Andra 30 rims too.  But I agree with you, my rims will likely last forever.  And Andra 40 CSS rims are not sold in USA, so I would be looking at very expensive shipping to get a pair of very expensive rims shipped from Europe. 
http://www.ryde.nl/andra-40

Other brand rims are not drilled for Rohloff and are not CSS, so I am less enthusiastic about other rims.  And when I have to pay retail prices for spokes, building up a wheel with different brand and model rims would push the costs even higher.  But if I stayed with Andra series of rims, I think the ERD is close enough that I could re-use my spokes where other rims would likely require a different spoke length.  I build my own wheels, so there is no cost of labor.

When I built up my Nomad, I unfortunately believed the Thorn brochure that said it was a great expedition rim, the photos of the yellow Nomad in that same brochure with Marathon Extreme 57mm tires made me believe that the tire and rim combination would be a good one.  So, instead of researching rims the way I previously did for my Sherpa where I started with my planned tire sizes and then looked for a rim that would work best, I just ordered the Andra 30 rims based on their recommendation.

[Pavel]

I'm pretty tempted by these 650B wheels.  I wonder what it would do to handling if I had 26" in back, and the 650 up front?

[Danneaux]

I wonder what it would do to handling if I had 26" in back, and the 650 up front?

Well...probably nothing if you used a 26x2.0 Dureme up front and a 650x38 Compass/Grand Bois Lierre in the rear -- the outside diameter is essentially the same.

For a more complete discussion of how changes in tire size -- or mixing sizes -- and fork offset/rake can affect handling and effective trail, see my article here:
http://thorncyclesforum.co.uk/index.php?topic=4245.msg19567#msg19567

I have another article on the subject here:
http://thorncyclesforum.co.uk/index.php?topic=3893.msg20016#msg20016

A check on the canti post placement and available brake adjustment on my former Sherpa and current Nomad showed I could run 650B rims if I wished.

Best,

Dan.

[George Hetrick]

Yes it is, the clue is that the mk2 Nomad came in yellow.

I just had my shop fit the fork to my Nomad Mk2, and discovered a couple issues:

• The fender fittings have moved several inches, which means I'll need new stays
• The rack and fender fittings are now M5, rather than the beefier M6 of the original fork. I have no idea if using M5 bolts though M6 sized holes on the rack is an issue. Danneaux?

The rack mounts need the threads chased anyway, so I'll just ask my LBS to solve the issues.
---
edited to fix typo in Danneaux's name

[Danneaux]

Hi George!

The fender fittings have moved several inches, which means I'll need new stays

Simplest and cheapest option here for 'Merkins is a fresh set from Planet Bike. If you get their stays, do yourself a favor and also get their nice stay caps (unless you plan to trim the stays flush) and a full set of their really nice polished stainless drawbolts and 10mm nylock nuts. The lot is available with free shipping in CONUS and is available from this link: http://ecom1.planetbike.com/smallparts.html

The rack and fender fittings are now M5, rather than the beefier M6 of the original fork. I have no idea if using M5 bolts though M6 sized holes on the rack is an issue. Danneaux?

The quick answer: You should have no trouble. Just be sure the rack is pushed down against the bolt shanks (threaded part of the machine screw) before tightening and use thread locking compound.

TLDR: Long, involved answer...

While it is ideal to have the rack hole match the bolt shank's OD to within about 0.1mm oversized, in practice there is little problem. Rack mounting bolts are more likely to break if they are overextended (i.e. if a mudguard stay eye is attached between the rack mount and the dropout) or if the bolts get loose and the rack can fret (work back and forth) or pound outright on the bolt threads. In most cases, it pays to keep the bolt threads on the rack side of the dropout as short as possible. On front racks and eyelets, I will often run my bolts from the inside out, so the head is trapped inside, then use a nylock nut to secure the rack on the outside. This allows the bolt to be removed easily in case it breaks. Andy Blance does the same. I frequently do this also at my seatstay mounts. It is rarely possible to mount a rack this way on the right dropout because of limited clearance between the chain and dropout that would foul the bolt head.

Nearly every rack on the market (I have personally checked almost 30 now) have holes drilled sufficiently large to accept 6mm bolts. Certainly Tubus, Surly, and Thorn racks will accept 5mm or 6mm. My 2011 Thorn Sherpa Mk2 came with frame rack mounting bosses threaded at M5x0.8 and worked fine with Thorn Low-Loader Mk V front and Surly Nice Rack rear racks drilled to accept M6x1.0 bolts.

Ideally, the larger bolts are both stronger and more secure -- they are 16.7% larger in outside diameter. I can feel the difference 6mm fittings make and the difference in stability was measurable in my testing; the more robust mounts resulted in less lateral sway, but I think the core reason is not just the bolt thread side but the larger OD of the mounting boss which offered better bracing.

When I braze my own racks from cromoly tubing, I mill the bottom stanchions from steel billet and use stepped fittings: The through-hole clears the bolt threads with 0.1mm clearance and the allen socket head is recessed into the stanchion on a slight countersink with 0.1mm head clearance. I turn the underside of the bolt heads to match the slight taper of the shallow countersink. It makes for a nice, flush fitting and since the stanchion well is conical, the rack mount self-centers over the bolt head and threads. I also employ solid billet inserts between the rack tubing and stanchion so the joint is effectively lugged internally and has a larger wetted area when I braze it. Makes for a very strong connection. The rear rack I built for my Folder has no problem holding my 78 kg when I stand on when it is mounted to the bike. Photo of its mounting stanchion and recessed bolt below.

All the best,

Dan.

[mickeg]

Agree with Dan, M5 bolts are ok when the rack is drilled for M6 bolts.  I also have several racks that will take M6 bolts, but I use M5 on all bikes except my Nomad which uses M6.  And since you are talking about the fork, that is the front where you likely are not loading it down with 20 kg of weight on each side, making M5 more likely to survive quite well.

Dan mentioned the stay caps, so I thought I would point out another option.  I recently built up a Titanium touring bike (oops, not Thorn, sorry) and within a very short distance of riding the toe overlap meant that I had already knocked the stay cap off of one of my stays.  The only color on the entire bike was two taillight lenses (red) and a headbadge (also red), but everything else was bare metal, black or white.  So, I decided to add a bit of color, instead of black fender stay caps I got red caps for all of my fender stays.  Looked neat enough that I pulled the black ones off of my Nomad and put red on there too.  Both bikes have black fenders.  I like to keep my fender stays long enough that if I put them on a different bike, I have minimal risk that the stays will have been cut too short, thus I always have about 10 to 20 mm of stay sticking out past the fender bracket.  Shipped from Asia, expect it to take several weeks.  Package of 100, so I can keep losing them and have plenty of spares.
https://www.amazon.com/gp/product/B01N9VWPMJ/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

In the event that the above link does not work, or in the event that you try to order from a different country version of Amazon, I pasted some of the description here:

uxcell 3mm Inner Dia Rubber Hose End Cap Screw Thread Protector Cover Red 100pcs
Ships from and sold by uxcell.
    Product Name: Thread Protector Cover; Country of Manufacture: CHINA
    Material: Rubber; Net Weight: 26g
    Package Content: 100(+/-2%) x Thread Protector Cover; Main Color: Red
    Total Size: 16 x 5mm/0.63'' x 0.2''(L*D)
    Inner Dia.: 3mm/0.12''

Photo, you can only see a couple stays in the back of the back fender on the bike closest to the camera.  Ok, with panniers, there is some color, but without any touring gear on the bike it is nearly colorless.

[Danneaux]

Very nice, George (mickeg)! 

Vinyl vacuum caps from the automotive store will also work (I had red ones on my red tandem for awhile but have since switched to different mudguards/fenders that have a black plastic cap joining two co-located stays.

All the best,

Dan.

[George Hetrick]

Thanks to you both! Very thorough, and I shall cease my fretting on this topic.

[George Hetrick]

Just FYI -- I have my Nomad back and it is a thing of beauty. Back to a rigid fork, with fenders and racks all fitted, and disc brakes, so it will stop even in pouring rain 

[Danneaux]

Yay! So glad the results are proving satisfactory for you, George.

How is the ride quality? Have you noticed any difference in front end stiffness/shock absorption from the more rigid disc fork?

Any photos available? Photos are always good, especially those showing mudguard/fender struts with disc mounts. 

Also, what disc calipers did you go for? TRP Spyke/Spyre for added rear rack clearance?

All the best,

Dan.

[George Hetrick]

Dan, this is the setup we discussed back in http://thorncyclesforum.co.uk/index.php?topic=8871.0, where I eventually went for the Hope hydraulic brakes with a suspension fork. As Dave Whittle pointed out, these are low-enough profile to work.

Attached are pics with the new rigid fork, and disc brakes, along with a pic of the rear brake.