Thorn Cycles Forum
Technical => General Technical => Topic started by: il padrone on August 07, 2022, 03:57:13 AM
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Hi, been away for a long time. I would value any input about this minor crack in the powdercoat which has appeared right beside the front rack mount on this 2 year old disc-fork (Thorn Nomad Mk2). The bike has had limited use due to COVID lockdowns but has been on a couple of 3-5 week tours in the Australian mountains and outback, carrying 15kg on the front panniers.
Can it be left alone, or should I be looking to get it rebrazed?
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If that was mine, I would be asking Thorn about warranty coverage.
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If that was mine, I would be asking Thorn about warranty coverage.
<nods> I would be doing the same. First move would be to send photos from several angles taken in bright light as clear and well focused as possible so Thorn can fairly evaluate them and advise on next steps.
Speaking as an amateur framebuilder, it appears from this photo this is not superficial to the paint only and there has been some movement between the boss and the fork blade, indicating a fractured braze. This can occur from any number of conditions but best have Thorn examine it to get the final word.
I have rebrazed fractured rack bosses on other makes and they came out successfully so if that is in the works there's a good chance of success, albeit at the cost of some local paint damage requiring touchup or a respray.
Best of luck, Pete; please let us know how you come out.
Best, Dan.
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Agree with the others.
If it is a braze failure, the consequences could be nasty (front rack going into wheel ?).
If it is not possible (or too much hassle) to get the fork reviewed by Thorn under warranty, I would strip all the paint of the area to check the brazing, then probably get the advice of a local framebuilder whether the fork should be repaired or replaced. That's assuming you have a framebuilder reasonably near you.
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Damn! I have a two week tour to Kangaroo Island that I am leading in 6 weeks. No real other bike to ride for such a trip, and a fork return to UK is pretty much out of the question. Hmm...
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Which braze on is it? And why is there a spacer? Also do you have a rack with a rigid over wheel hoop?
Depending on which braze on it is, you may be able to get an additional fitting (Or two) somewhere to support it, Tubus make some clamps (See below), but even something as crude as a couple of jubilee clips will take the weight, just keep an eye on them and protect the paint.. If the spacer isn't strictly necessary, remove it, or at least don't use one any thicker than needed, the spacer simply creates leverage. That's not a criticism, sometimes it's inevitable, an alternative is to use a longer screw from the inside of the fork, then a nut tightened onto it instead of a spacer, leaving you with a threaded stud to attach the rack to. Lastly, if you don't have a rigid hoop on your rack, I thoroughly recommend you upgrade, not only is it a more rigid structure, in the event of a failure it's less likely to be catastrophic.
https://www.tubus.com/en/products/accessories-front-carriers/tubus-product/lm-1-mounting-set-for-forks-without-eyelets
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Damn! I have a two week tour to Kangaroo Island that I am leading in 6 weeks. No real other bike to ride for such a trip, and a fork return to UK is pretty much out of the question. Hmm...
If I was you, I would state that when you contact Thorn, and as Dan suggested, some better photos. Do you have access to a camera with a macro setting?
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Yes, that photo was just a quick shot with the phone cam. I have several much better cameras.
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Which braze on is it? And why is there a spacer? Also do you have a rack with a rigid over wheel hoop?
It is the fork mid-mount for the front rack. The spacer is required because of the width of the rack's double-mount; it is a Tubus Duo, no hoop over the tyre, separate racks each side. I guess that I could move the spacer to the inside of the fork, but this may get tricky with the disc-mount at the bottom. Shall check it out.
https://www.metrocycles.com.au/product/tubus-front-pannier-rack-duo-lowrider/ (https://www.metrocycles.com.au/product/tubus-front-pannier-rack-duo-lowrider/)
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If that is a crack in the metal, I would not use a rack like the Duo. If you fell at speed, the side load stress on the mount might snap it the rest of the way off.
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Better photos. I have emailed SJS Cycles for advice.
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Further to my fork rack-mount. After some discussion with Thorn about the crack, I have passed the fork on to a local trusted frame builder for repairs. After an initial examination he became suspicious that the braze looked to be silver-solder. Knowing this matters a lot for the repair. I have emailed Thorn for confirmation of what attachment media was used on the fork; waiting to hear any response about this. Time is pressing as I am organising a 2-week tour for a group commencing Saturday week, and I really NEED the bike to be right to ride.
Does anybody here have the knowledge to tell me whether a 2018-19 Thorn Nomad Mk2 disc fork has bronze-welded rack mounts, or are they silver-soldered? Can you confirm anything about the brazing media used.
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Pete,
While I cannot speak to the method/media used on Thorn's forks, I can speak as a hobbyist framebuilder who has made and/or modified a lot of frames, racks, and so on over the last 30-odd years.
If the rack boss is stainless, then it is almost certainly brazed using silver-solder. Most brass fillers will not wet the surface of stainless, and if they do they will produce low-quality joints. As I recall, all Nomad bosses are stainless, but this can easily be determined once the boss is off and possibly while it is on (magnet, though some stainless still has some magnetic attraction).
If I were to do the repair, I would heat the boss to remove it so I could clean the base metal of the fork and the boss, then reposition it using some all-thread to align it with the boss on the other side and then solder-braze anew with at least 55% silver content rod.
It will not do to simply heat the joint so new filler can flow; this is something your framebuilder will know.
Hoping this helps.
Best, Dan.
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Thanks for this info, Dan. The Nomad's cable guides are all stainless; not sure about the rack bosses. I will pass your info on to the frame repairer, good point about a magnet to check if
it's stainless.
Cheers, Pete.
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Pete,
I went back through my files and found Thorn indicates the Mk2 rack bosses are indeed stainless (see attached). Of course, this is for the original v-brake fork but I would be very surprised if they were anything different on the disc fork.
As a double-check, the fork rack bosses on my own 2012 Nomad Mk2 are also non-magnetic and don't recognize a magnet.
Good luck on your repair; please let us know how you fare after your return.
Best, Dan.
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Not a failed rack-mount. Yes, a cracked fork-blade :'(
REALLY pissed-off with Thorn right now. Lousy response to my reasonable questions, and quite wrongly accusing me of overloading the fork.
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I really don't have the time to constantly monitor forum threads, thanks Dan for pointing this one out to me.
I have had a quick look through my emails but I'm afraid I can't find my replies without more time than I have currently.
Feel free to publish my replies to your emails.
What I would just explain is the extended guarantee we offered on frame and fork was only if purchased as part of a complete bike, not as in this case. I also didn't mention that this type of failure can be caused as a result of crash damage.
My personal feeling was that the fork blade was ripped not the weld failed but that was just from the photos.
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I was NOT seeking any warranty cover, just information and opinion about repair, via email. What I got instead was a false accusation of “overloading” by use of rear panniers on the front rack, a thing that I never do. Upon asking further about the rack-mount fastening medium there was no reply. We deduced that it was silver solder. A bit of customer-service would go a long way.
Upon comparing the old fork with the 2018 disc-fork it is clear that the rack mounts which have been changed to 5mm instead of 6mm, have a narrower solder-solder join. The crack went through the weld and into the fork. My framebuilder’s comment was that a fork should never crack in that location. It is clear that my use of the Tubus Duo with this now-narrowed mount has caused the failure. As I wish to continue using disc brakes, I plan to get the fork repaired (both sides) with a patch-plate and widened band of silver-solder for the rack-mount.
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It is clear that my use of the Tubus Duo with this now-narrowed mount has caused the failure. As I wish to continue using disc brakes, I plan to get the fork repaired (both sides) with a patch-plate and widened band of silver-solder for the rack-mount.
Is it practical to use a hoop type rack where the hoop over the wheel is used to add some structural integrity to the rack unlike a rack like the Duo (or the Thorn front low rider rack) that will put twisting stress on the fork blade and rack mount if you crash?
If you are having a frame builder work on the fork, any adjustment to the mounts to enable a hoop type fork could be made at that time too.
When I look at sales brochure from when I ordered my Nomad Mk II frame and fork (rim brake) in early 2013, the sales brochure listed the bike weight capacity with this statement: Max Load using Front panniers with 20Kg and Rear panniers, 3Kg bar bag + 3 cages.
I doubt that I have ever loaded the front panniers (25 liter Frontloaders) with my rain gear strapped on top anywhere near 20 kg, and that rating would have been based on a Thorn Rack that is mounted the same way as a Duo.
I have only once weighed my individual panniers during a tour, I did that from curiosity. My front panniers summed to about 10 kg.
I initially tried a Tara on my rim brake fork, but did not like how far the horizontal bar deviated from horizontal. I ended up using a rack without a hoop that is attached similar to a Duo, but now I wonder if that is a bad idea. My fork is now nine years old, warranty ended long ago.
In your case with a fork that is only two years old, I would have assumed it was covered under warranty.
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I could readily get a Tara rack to fit, but as the Thorn fork was designed to suit a Duo, and because I preferred its cleaner look I fitted the Duo. It has run very well for over 9 years of all sorts of rough stuff. There are no different fittings needed for a Tara hoop-style rack; I just would prefer to use the excellent Duo racks that I have bought. They have often carried up to 14kg in total (6-7kg per side).
Thorn give no warranty upon separately purchased frames nor on forks, only on whole bikes.
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Thorn give no warranty upon separately purchased frames nor on forks, only on whole bikes.
I built my Nomad Mk II in early 2013. At that time the sales brochure Issue 20 was what I relied on for my information when I bought my frame on or about 9 Apr 2013. I made the attached graphic from page 23 in their sales brochure.
I have had no reason to file a warranty claim and have no expectation of doing so, but if they would have said to me that I was buying a frame and fork with no warranty, that is a sale that would not have occurred.
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I would have expected a frame to have a warranty even if only bought as a frame. Spa Cycles provide 10 years warranty to the original owner eg https://spacycles.co.uk/m11b0s143p3698/SPA-CYCLES-Titanium-Elan-Mk1-Frameset although there's no corresponding statement for the forks.
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It isn't true that you had no warranty, what RT clearly says is that the extended warranty doesn't apply on framesets, I'd never assumed it did.
For everything purchased in the UK, and the EU, there's a minimum requirement - Any fault appearing in the first six months is considered to have been there from the start. A fault appearing after that, is covered for a reasonable time up to 6 years, depending on the goods, their use and expectation.. It's debatable how long that reasonable time should be on a cycle frameset, but it's usually accepted that any consumer goods not considered disposable should be covered for a minimum of two years.
All warranties rely on a fair amount of goodwill. If the fault is disputed, it's the retailers responsibility to prove it was caused by the consumer if it occurs in the first six months. Any time after that, whether the warranty is statutory or contractual, the position is reversed, it's the consumers responsibility to demonstrate either the fault was there from the outset, or is the result of faulty materials or workmanship. Good luck to anyone who thinks they can do that!
Basically, after six months, unless you have something that formed part of the sales agreement that says otherwise (like unconditional) you're suggesting to the retailer that the fault shouldn't have occurred and hoping they agree with you.
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Thorn give no warranty upon separately purchased frames nor on forks, only on whole bikes.
I built my Nomad Mk II in early 2013. At that time the sales brochure Issue 20 was what I relied on for my information when I bought my frame on or about 9 Apr 2013. I made the attached graphic from page 23 in their sales brochure.
Grrr…. Clearly the fork is not part of that, but it does still leave a bad taste.
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Here's a screenshot from the current brochure, maybe if it wasn't 80 pages long more people would read it properly.
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Finally, after a stint with the old rim-brake Nomad fork (steerer too short, fork crown headlight bolt out-of-line) I have the repaired disc-fork back. All TIG-welded on. It ain't pretty but it sure ain't going to be moving any time soon.
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Brutal but tough.
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That fork should work well for you now.
Finally, after a stint with the old rim-brake Nomad fork (steerer too short, fork crown headlight bolt out-of-line) ...
My headlight mounting hole at the fork crown was also aimed to one side, and with a plastic headlamp mount I could not bend the mount to accommodate it.
But I recalled that a friend had an alignment problem on a frame with something and he fixed it with those spherical washers that come on rim brake pad holders that are designed to adjust alignment. That is how I got mine fixed, see photo.
But I agree with you, it should have been aligned right in the first place.
Later I switched to a B&M light with a metal mount. So, more time spent to get the mount bent just right to compensate.
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For the past 9 years while using the fork I used a set of the same spherical V-brake pad spacers (from cartridge pads) to correct the light aim. Even with a rod-steel headlight bracket I could not bend it to get the aim straight. Since I got the new disc fork I binned these and could not find any more at short notice, so for the past 2 moths I have just put up with it.