I finished my wife's SS Pug build today and promptly folded the front fork under hard braking. (Burnishing the brakes and testing for wheel flex under braking.)
I Googled for bent Pugsley forks to see if there is a known problem and came up dry.
The fork has 100mm dropout spacing with the holes for Anything Cages and no cantilever bosses. It folded right at the top of the brake mount/brace and a wrinkle extends to the edge of the bottom Anything Cage hole.
It is unfortunately not clear to me that this is a manufacturing defect rather than a design defect and I'm a little afraid to replace the broken fork with one just like it. I can't help but wonder if a weakness was introduced with that bottom hole so close to the brake brace. It's pretty disconcerting to have folded the fork so easily.
PS. I've never seen a bent fork that wasn't caused by an accident, usually bike vs. car. Have you?
Holy heck! Wow! That totally has to be a manufacture defect. I heard of frame failures at the point of disk brake attachment, which is why they now put on brake brace triangle gussets.
BTW, I released the skewer after to fact to take any load off the hub/rotor. I put the wheel on my truing stand and it's still true. I'm not entirely sure about the rotor but it's straight enough that no damage is obvious.
what size rotor is that. recently i tried to find out max rotor surly recommends for the moony and pugs fork. too big a rotor can put quite a bit of stress on those legs.
Me too. What build is it? I have a packaged Necro 2012 with the first Moonie fork. Aren't the new ones for 2013 offset like the reg Pugs are? Now I worry about my Moonie fork attached to my Necro.
Mine was a custom build with a symmetrical 100mm fork. As far as I know all the prebuilt bikes come with 135mm forks. Not saying, but hoping the problem is limited. It seems like there would be more results for "bent pugsley fork" etc. in Google if it weren't.
I've been using the same fork (new model, 100 mm spacing) with a 180 mm rotor for the last few months without any problems. It weighs 1090 grams so not "extremely heavy", I weigh 165 lbs.
I notice more flex on the Surly fork than on my other steel fork (custom 29'er) so I get a lot more brake rub, but other than that it's been ok so far.
If I were Surly, I'd want that fork back for testing and discovery. No way with a puny 6" rotor that this should ever happen. Thank goodness it was steel. Rather frightening!
I'm 240lbs, using Hayes Nine Carbons with 8" rotors on my Enabler fork with no problems like this, thankfully. However, there is a moderate amount of front flex (noticed on pavement). My real issueis that the brakes howl with light to moderate pressure and cause a reasonance throughtout the front end. More annoying than anything, and I'd like to find a solution.
I'm 240lbs, using Hayes Nine Carbons with 8" rotors on my Enabler fork with no problems like this, thankfully. However, there is a moderate amount of front flex (noticed on pavement). My real issueis that the brakes howl with light to moderate pressure and cause a reasonance throughtout the front end. More annoying than anything, and I'd like to find a solution.
Side note to trailmaker: My Enabler fork did the exact same thing when I switched from BB7 to SLX...Howling and resonance with moderate pressure. Close inspection showed the mounting bosses were a tiny bit skewed--brake wouldn't 'square up' with the rotor, so pads were contacting at an angle. I dressed the bosses on the fork with a file until they appeared visually parallel with the rotor, just a few strokes really. Reattached adapter and now howl is gone. In retrospect the bb7's were unusually noisy as well. Willing to bet that's what's up with yours...
I must say that the last few hours i have been looking at the fork on my Karate Monkey quite a few times.
And i must say it looks a bit flimsy.
I'm starting to wonder how it will hold up to my 265 pounds once it's finished....
I don't think heat treatment would have been the problem. Cr-Mo steel is sometimes heat treated after welding to make it less brittle, but this is only necessary with thick material, not thin bicycle tubing. It looks like those forks are just not strong enough for disk brakes. Maybe the material was mild steel instead of chrome molybdenum alloy steel.
I wouldn't spend too much time analyzing what happened to one fork. Surly forks seem to be pretty robust and you don't hear of failures like this often - in fact I've never seen anything like this with a Surly fork. So it's quite possible there was something unusual going on with this particular fork.
A more common complaint with Surly forks are that they are too stiff and overbuilt.
^^^ Yep, it was done with best intentions. He wasnt coming on with guns blazing pointing blame. Its good to share so others can inspect their forks - who's heading to the local playing fields to brake/break test their Surly forks ???
Yes, sorry for the little thread segue back there, but I have been slightly worried that continued resonance through the fork blades might cause a failure like in the OP. My weight plus the big rotor plus the fact that I ride this thing like a regular trail bike (hard!) gives me some pause. Nothing, yet........
If this thread causes everyone to go out and look at their fork, and now do so on a regular basis, then that is a good thing for us all. It's even good for the manufacturer.
Good point, I guess I should have clarified that better. If there is a widespread issue I'm sure fork owners will hear about it in a more formal manner as it is obviously a serious safety concern! You're right, awareness is good... I've been riding surly forks for almost 10 years and know they design their parts well and overkill. Major ouchie with that carbon fork. wow.
Might it be possible that not having the rotors and shoes bedded in produced more friction than they otherwise would during their normal service life? I tend to agree that this particular fork was defective, but with due respect to the OP, I'd suggest that the bedding-in period may not be the best time to do stoppies.
In any case, I hope it's not the design, because I've just installed two of these; one on my 907 and the other on my daughter's Necro. Neither of us is real hard on the equipment, but I was doing a bit of enthusiastic singletrack riding on mine yesterday. :skep:
So I spent some time the last couple of days doing (or trying to do) "stoppies" on my Pugsly and recording them on my iPhone using various "g force" apps. None of the apps I tried worked perfectly but showed that with the right software the iPhone could be a great little accelerometer/datalogger. When I did my previous calculations on the stresses the fork sees under hard braking I came up with the numbers that about the most I'd trust the Pug's fork to would be around 1/2 g deceleration; and also 1/2 g should yield a stoppie.
The first trials yesterday were a bit of a non-event; it had rained the night before and no matter how hard I tried it the front tire (Nates F/R) would slide before the rear end lifted---both on pavement and on my gravel driveway. (I was able to easily get some stoppies on a couple of my 29ers though) As things dried out the Nate got enough grip and I was able get into the stoppie zone. Here are some of the marks left on the gravel:
The length of the "skid" (from the partially locked front wheel) correlates well with the braking effort to get a stoppie from the 10 mph target speed I was using.
Here's a screen grab from "CMS Lap Timer"; a $0.99 app:
The graph shows 2 "near stoppies"; I didn't hold the entry speed steady for very long so part of the deceleration is occurring from the positive part of the curve---the -.15 g is probably at least twice that. Also the 5.9 MPH speed is from the GPS and is an average over ??? distance (this app is optimized for car racing)
Here's using "gForce"; a free iPhone app:
This shows 5 events; the 2.3 g is an actual stoppie but is showing the shock of the rear end slamming down---not the braking effort. The other numbers (0.4 ~ 0.8 g) are more of what I would expect but probably a bit on the high side.
FWIW my brakes are Avid Juicy Sevens' and a 180mm rotor on the front; not a particularly powerful brake IMHO. I don't remember what the pads are but they're probably organics. The iPhone was "jury-rigged" mounted to the rear rack (why that 2.3 g slam-down reading)
So I spent some time the last couple of days doing (or trying to do) "stoppies" on my Pugsly and recording them on my iPhone using various "g force" apps.
Surly here. Wow, that is a nasty bend. We hope you managed to roll out ok. We are sorry you had this experience with one of our products.
Please work with your LBS to get the fork sent in as soon as possible. It will be covered under warranty. We really need to check it out and see what is going on here. This obviously shouldn't happen, and we will be investigating immediately once we get the fork back.
If anyone else has any problems with any Surly product, ever, please feel free to contact us directly or work with your local bicycle shop. Just send an email to derby(at)surlybikes.com. We value your feedback, and you. Thanks, Surly
Surly here. Wow, that is a nasty bend. We hope you managed to roll out ok. We are sorry you had this experience with one of our products.
Please work with your LBS to get the fork sent in as soon as possible. It will be covered under warranty. We really need to check it out and see what is going on here. This obviously shouldn't happen, and we will be investigating immediately once we get the fork back.
If anyone else has any problems with any Surly product, ever, please feel free to contact us directly or work with your local bicycle shop. Just send an email to derby(at)surlybikes.com. We value your feedback, and you. Thanks, Surly
:thumbsup: This is such a refreshing attitude compared with other companies that give so many problems over warranty claims!:thumbsup:
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