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Trek Ishiwata fork failure

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Trek Ishiwata fork failure

Old 06-12-21, 10:49 PM
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Trek Ishiwata fork failure

First of all, I am without a scratch.

My Trek came with the slightly infamous Ishiwata death fork, which I was told not to worry about but maybe keep an eye on. It looks like I did not keep good enough eye.


Cracked on both sides. Looking at the cracks, there's some rust in there on the crack surfaces, so it's probably been there all along. That's good - it means it's not my fault for brazing cantilevers onto it or whatever! I mean, hek, it's nowhere near anything I brazed.

I've put some hard miles on this Trek in the past year since I built it. One thing kept rearing its ugly head, however: violent brake judder! It almost seemed like the brakes had a servo effect, like the fork was flexing enough on braking to cause the brakes to be applied all the more. I changed pads, which made it go away for a little while, but then it came back, worse than before! Another 200 or 300 miles after that, I was riding on a damn sidewalk after a bbq with friends, and testing out the brakes (just for fun, y'know, at low speeds, to try and figure out the judder), and it did a surprise front-wheelie. I thought it was the beer! I put the rear wheel back down, kept riding, but the bike felt funny. This crack is what I found.

@gugie , got any tips on building my first fork? I'm thinking to make it wide, for 48s, because 48s are the new 42s.
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Old 06-12-21, 11:17 PM
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Before the advent of cheaply produced unicrown forks, there were some cast steel fork crowns made for MTBs.... If you could find one of those it would be more than adequately wide enough for a 48mm tire.

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Old 06-12-21, 11:27 PM
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Ugh. Very glad _you_ suffered no damage! I've seen so many photos of those forks cracking, yet it seems like nobody gets hurt. Still, makes me totally question the wisdom of not immediately changing my '82 614 grocery bike death fork. But I hate the idea of having to pay more for a fork than what I paid for the whole frame. And it ain't broke yet...

I've only built one fork, and I'm not a fan. I dislike how hot you need to get the crown and drops vs how thin the tubing is in comparison. It's been done successfully forever, so if you're already comfortable brazing it shouldn't be a problem. But I like the idea of socketed drops/crowns to better equalize the masses that need to be heated.

The "ain't dead yet" fork:

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Old 06-12-21, 11:32 PM
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Originally Posted by scarlson View Post
First of all, I am without a scratch.

My Trek came with the slightly infamous Ishiwata death fork, which I was told not to worry about but maybe keep an eye on. It looks like I did not keep good enough eye.


Cracked on both sides. Looking at the cracks, there's some rust in there on the crack surfaces, so it's probably been there all along. That's good - it means it's not my fault for brazing cantilevers onto it or whatever! I mean, hek, it's nowhere near anything I brazed.

I've put some hard miles on this Trek in the past year since I built it. One thing kept rearing its ugly head, however: violent brake judder! It almost seemed like the brakes had a servo effect, like the fork was flexing enough on braking to cause the brakes to be applied all the more. I changed pads, which made it go away for a little while, but then it came back, worse than before! Another 200 or 300 miles after that, I was riding on a damn sidewalk after a bbq with friends, and testing out the brakes (just for fun, y'know, at low speeds, to try and figure out the judder), and it did a surprise front-wheelie. I thought it was the beer! I put the rear wheel back down, kept riding, but the bike felt funny. This crack is what I found.

@gugie , got any tips on building my first fork? I'm thinking to make it wide, for 48s, because 48s are the new 42s.
That'll buff out.

Building a fork is just like building a frame, but is very different. ;-)

I just built a fork for my Ritchey Breakaway to replace the early 80's looking ultra-beefy mountain bike fork that it came with, then a few weeks later had @SquireBlack over for his first fork building session using the method I learned at UBI 5 years ago. You need to figure out two parameters you want, A-C dimension and trail - which as you know is a derived dimension using head angle, fork offset, wheel diameter and tire size. Framebuilder Supply has a good selection of wide fork crowns. I like the Pacenti MTB fork crown for super wide tires, I used that on my gravel bike build with RTPs on it. They also sells pre-bent fork blades that are fairly good. That relieves you of the need for another jig as well. Since you're not using disc brakes those blades should work just fine.

As for tips, you'll need a fork jig. With your machining abilities (and assuming your access to the school shop is back in business), I'm sure you can make your own out of unobtanium castoffs.

Order of assembly as I learned it:
1. Steerer to fork crown, steerer inserted just proud of the crown. Pin the fork crown to the steerer, hold it upside down, apply filler to the steerer-crown at the "proud" section, use heat to draw it down until you see it coming out at the crown race end.
2. Trim blades at the tapered and curved end for the offset you want.
3. Prep the ends for tab, lug, or plug style
4. Braze dropouts in. You can do this either with a special jig, or just use the fork brazing jig with the blades dry fit into the fork crown. I just use the fork jig i have - the key here is to get the alignment of the dropouts to the blades as good as possible to minimize cold setting them later.
5. Your blades should be too long at this point. Trim the fat end of them a couple of mm's long to achieve the A-C dimension you desire. File them perfectly square to the straight portion of the blades. I use a very small square to check front to back and side to side squareness.
6. With the blades dry fit into the fork crown, insert a test wheel. If it's not centered perfectly, file one side down a bit and retest. Recheck your A-C measurement. If you're within a mm, I'd say you're good to go.
7. Jig up the assembly, braze in the blades upside down.
8. Use H-bars to align dropouts perfectly.

Don't braze on the small bits until the fork is done.

I skipped a ton of small things, but already got the knowledge and chops to figure them out. If not, you've got my email address.

Or, wait until Doug Fattic, Mark Bulgier, or John Thompson chime in and give you the correct way.

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Old 06-13-21, 12:47 AM
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Originally Posted by gugie View Post
That'll buff out.
"It's just a flesh wound"....

A question for JT, was it ever determined was caused so many failures in those Trek Ishiwata forks?

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Old 06-13-21, 05:02 AM
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Glad to hear you're OK. I have a 1980 Trek 412 (Ishiwata main tubes, hi tensile fork and stays) with the same fork crown. I have the frame hanging on a hook because I can't figure out what to do with it. Maybe I need to go to the collective, find a fork, and uglify the bike.
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Old 06-13-21, 06:08 AM
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Originally Posted by bikemig View Post
Glad to hear you're OK. I have a 1980 Trek 412 (Ishiwata main tubes, hi tensile fork and stays) with the same fork crown. I have the frame hanging on a hook because I can't figure out what to do with it. Maybe I need to go to the collective, find a fork, and uglify the bike.
I have an 82 or 83 412 as well.(too lazy to look up the serial number currently) It was made later in the production run. It has an original Tange fork instead of the Ishi one.
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Old 06-13-21, 06:45 AM
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Originally Posted by pcb View Post
I've only built one fork, and I'm not a fan. I dislike how hot you need to get the crown and drops vs how thin the tubing is in comparison. It's been done successfully forever, so if you're already comfortable brazing it shouldn't be a problem. But I like the idea of socketed drops/crowns to better equalize the masses that need to be heated.
You must have used brass (frame builders call it brass but really it is bronze) as brazing material. As long as you get close tolerances, silver works perfectly at lower temperatures (1200º instead of 1600º). I know you know this but just saying again. There are a number of socketed front dropouts available that can be brazed with silver. Some fork crowns are easier for my framebuilding class students to braze than others so when you decide it is time, I can advise. I've got some old framebuilding supplies (steerer and fork crown but not blades) from Miele in Toronto when they went bust that will work well.
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Old 06-13-21, 08:09 AM
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wow thats very unfortunate!
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Old 06-13-21, 08:41 AM
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I have a columbus trek fork I'm not using. You would probably need to replace the steer tube as its from a 54cm frame. Let me know if you are interested. I'm local
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Old 06-13-21, 09:03 AM
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I thought it was only the forks without tangs that were the death forks. Thus I didn't give a second thought to making my 80 414 into my gravel bike. But I'm an old man, riding only flat ground. I have no other options here. I will keep an eye on it.
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Old 06-13-21, 10:34 AM
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Originally Posted by seedsbelize View Post
I thought it was only the forks without tangs that were the death forks. Thus I didn't give a second thought to making my 80 414 into my gravel bike. But I'm an old man, riding only flat ground. I have no other options here. I will keep an eye on it.
This is one of the ones without tangs. The bike is an '82 61x.

Originally Posted by verktyg View Post
Before the advent of cheaply produced unicrown forks, there were some cast steel fork crowns made for MTBs.... If you could find one of those it would be more than adequately wide enough for a 48mm tire.
Right, I rode a Pug Orient Express with a fork crown like that! Great big gothic looking thing, really inspired confidence in the construction.
If I can't find some cool old one, my next thought is as @gugie says, the Pacenti MTB crown. That thing's wider than the tandem crown on my Herse!

Originally Posted by uncleivan View Post
I have a columbus trek fork I'm not using. You would probably need to replace the steer tube as its from a 54cm frame. Let me know if you are interested. I'm local
Ohh, thank you but that's ok. I will keep it in mind but I want to use this as an opportunity to upgrade to wider tires!
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Old 06-13-21, 01:17 PM
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Originally Posted by seypat View Post
I have an 82 or 83 412 as well.(too lazy to look up the serial number currently) It was made later in the production run. It has an original Tange fork instead of the Ishi one.
Interesting. Do you remember offhand if your RD cable stop is on the top ('82-style) or bottom ('83-style) of the chainstay? Asking because I have a 412 with an '82 serial number and '83-style RD cable stop. Fork DOES have extended tangs on the inside of the crown, so it's NOT a death fork. The 022 decal says "double butted tubes forks & stays", but I'm pretty sure I recall seeing Tange on the steerer tube when I had it apart. I wonder if the non-death forks were constructed of a Tange steerer and crown, with 022 blades.
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Old 06-13-21, 01:18 PM
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https://www.bikeforums.net/classic-v...ata-forks.html
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Old 06-13-21, 01:23 PM
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Thank you for this cautionary thread. It does not affect me directly, because none of my forks are from that vintage, but it is always helpful to learn about common failure points in various frames and forks. That looks damn scary to me.

My own record over about 200k km of cycling is three broken frames, two broken (and one cracked) cranks, a broken pedal cage, a broken front hub flange, a few spokes and cables, but fortunately no broken chains, forks, stems, or handlebars.
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Old 06-13-21, 01:43 PM
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Right, I saw that thread! I wish I could still vote in the poll.

Originally Posted by John E View Post
Thank you for this cautionary thread. It does not affect me directly, because none of my forks are from that vintage, but it is always helpful to learn about common failure points in various frames and forks. That looks damn scary to me.

My own record over about 200k km of cycling is three broken frames, two broken (and one cracked) cranks, a broken pedal cage, a broken front hub flange, a few spokes and cables, but fortunately no broken chains, forks, stems, or handlebars.
I've broken a first-gen Phil BB axle, a Campy rear hub flange, two MA3 rims, 10-15 spokes, three Blackburn racks, two frames (one Trek fastback seatstay and one Holdsworthy Claud Butler lower head lug), and this fork. I remain uninjured, which I guess is surprising. I think the VO front minirack, mounted on my brazed-on canti posts, slowed the failure and helped stabilize things when the failure occurred. The bike had been handling rather "lyrically" as my failed Holdsworth/Claud did, I would say, in the 200 miles or so leading up to the failure, in addition to the brake judder. I thought I was just out of shape or slightly delirious from either heat, cold, beer, coffee, mass hole drivers, or bad PhD advisorship. Victim blaming oneself is the Harvard way...

Originally Posted by madpogue View Post
Interesting. Do you remember offhand if your RD cable stop is on the top ('82-style) or bottom ('83-style) of the chainstay? Asking because I have a 412 with an '82 serial number and '83-style RD cable stop. Fork DOES have extended tangs on the inside of the crown, so it's NOT a death fork. The 022 decal says "double butted tubes forks & stays", but I'm pretty sure I recall seeing Tange on the steerer tube when I had it apart. I wonder if the non-death forks were constructed of a Tange steerer and crown, with 022 blades.
Cable guide is on the top. I'm sorry, I said it was an '83 in my earlier post. I've corrected that mistake. It's an '82 613 or 614 through and through, right down to the serial number. I forget if it says anything on my steerer, but I can update this thread when I take the bike apart. On the bright side, it's all "rinko" capable, so I can easily pull the fork. Right now it's just sitting there forlornly while I ride my Ron Cooper or Vitus, I guess!
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Old 06-13-21, 04:50 PM
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82 412 in my garage has a tang-less Ishiwata fork crown.
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Old 06-13-21, 05:12 PM
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There are non-tanged forks that aren't death forks, it's this specific Ishiwata fork model detailed in this post that's the problem.

Originally Posted by seedsbelize View Post
I thought it was only the forks without tangs that were the death forks. Thus I didn't give a second thought to making my 80 414 into my gravel bike. But I'm an old man, riding only flat ground. I have no other options here. I will keep an eye on it.
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Old 06-13-21, 08:55 PM
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Originally Posted by pcb View Post
Ugh. Very glad _you_ suffered no damage! I've seen so many photos of those forks cracking, yet it seems like nobody gets hurt.
Grant would crow about it, at least back in the old days: steel fails gracefully! I do think the VO minirack I had on it helped quite a bit to keep things together as well. As for your bike - examine it carefully! Maybe even put on the brakes and push the bike forward to watch the fork flex. You might be able to see cracks if they open up under flex. Although, I'll say I saw absolutely nothing, and based on examination of the rust in the cracked surfaces, it seems they may have started from the inside and propagated out, so there'd be no way to see anything until they come through.

Originally Posted by gugie View Post
I like the Pacenti MTB fork crown for super wide tires, I used that on my gravel bike build with RTPs on it. They also sells pre-bent fork blades that are fairly good. That relieves you of the need for another jig as well. Since you're not using disc brakes those blades should work just fine.
Thank you so much for the detailed write-up! I really appreciate it.
I have made a fairly ghetto re-raking jig made of plywood. Do you not think I should go full-rando and try out these Jan Heine flexy fork blades? Kaisei Toei Special? I guess they are a different oval and only work with his crowns, but you can smush them down in a vise to make them fit ordinary continental oval crowns if you want a different option. Do you think that's silly? Or maybe the cantilevers will give me brake judder with the flexy blades, all over again?

Also, what do you recommend for a steerer? Columbus splined, or some Jan Heiney Toei stuff (surprisingly cheaper)?

Originally Posted by verktyg View Post
"It's just a flesh wound"....

A question for JT, was it ever determined was caused so many failures in those Trek Ishiwata forks?
JT as in @JohnDThompson ? Would love to get his opinion!
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Old 06-13-21, 09:22 PM
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Why ask why? Trek Forks

Originally Posted by scarlson View Post
JT as in @JohnDThompson ? Would love to get his opinion!
Some time back, I remember John D Thompson addressed the question...

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Old 06-13-21, 09:26 PM
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Originally Posted by scarlson View Post
I have made a fairly ghetto re-raking jig made of plywood. Do you not think I should go full-rando and try out these Jan Heine flexy fork blades? Kaisei Toei Special? I guess they are a different oval and only work with his crowns, but you can smush them down in a vise to make them fit ordinary continental oval crowns if you want a different option. Do you think that's silly? Or maybe the cantilevers will give me brake judder with the flexy blades, all over again?

Also, what do you recommend for a steerer? Columbus splined, or some Jan Heiney Toei stuff (surprisingly cheaper)?
Well, the Framebuilder Supply pre-rakeds have more than enough offset to make a low trail fork. The Toei Specials don't seem to be a whole lot different - longer "narrow" part, perhaps? I don't know, and Jan's website doesn't have full specs, but I think they may not work with the Pacenti MTB fork crown, check into that. If you want to bend your own, have at it!

I don't have an opinion on steerers. I'm not sure they make a difference anybody could feel riding. With bits hard to come by due to supply chain issues, get one that's in stock ;-) I do know that the folks at Norther (when they were around) said the Nova Cycles CrMo steerer was rounder than others they've tried, and they're about $10.

Last fork I made was just about what we're discussing, but with a different fork crown.
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Old 06-13-21, 10:00 PM
  #22  
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I'm giving myself a bit of agida about this.

Easiest/quickest on the 614 would be a Soma Champs Elysees 1" caliper fork. New top headset stack, new stem, so redo/rewrap at least half a bar. $230
Next choice would be the same, but go with the canti fork to minimize fender clearance issues. Same $230, same installation issues.
Interestingly, Soma's same CE fork in 650b is cheaper, $170. But I already have 35-622 f/r, and probably couldn't go much wider than 38-584 w/o dimpling. Change wheels, change brakes, oy gevalt.

Maybe the least actual headache, and for sure cheapest, would be to swap the 614 parts over to the Fuji Touring Series IV frame I've got, but never ridden. Lower trail, more battered/uglier, built for 27" so 700c clearance should be a little better. Only issue there is dealing with the cantis---gotta be vintage/high-profile, because the boss spacing is narrow, and gotta make sure the brake shoes can get a little lower to hit the 700c rims. Some of the vintage cantis don't have great height adjustment ranges.

Or just keep riding the Trek as is, hoping for no failure, or a graceful one if it is to fail.

Originally Posted by scarlson View Post
Grant would crow about it, at least back in the old days: steel fails gracefully! I do think the VO minirack I had on it helped quite a bit to keep things together as well. As for your bike - examine it carefully! Maybe even put on the brakes and push the bike forward to watch the fork flex. You might be able to see cracks if they open up under flex. Although, I'll say I saw absolutely nothing, and based on examination of the rust in the cracked surfaces, it seems they may have started from the inside and propagated out, so there'd be no way to see anything until they come through.
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Old 06-13-21, 10:45 PM
  #23  
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Originally Posted by gugie View Post
Well, the Framebuilder Supply pre-rakeds have more than enough offset to make a low trail fork. The Toei Specials don't seem to be a whole lot different - longer "narrow" part, perhaps? I don't know, and Jan's website doesn't have full specs, but I think they may not work with the Pacenti MTB fork crown, check into that. If you want to bend your own, have at it!

I don't have an opinion on steerers. I'm not sure they make a difference anybody could feel riding. With bits hard to come by due to supply chain issues, get one that's in stock ;-) I do know that the folks at Norther (when they were around) said the Nova Cycles CrMo steerer was rounder than others they've tried, and they're about $10.

Last fork I made was just about what we're discussing, but with a different fork crown.
OK, I guess I was concerned more about getting enough flex. The Toei Special blades are sold on their ability to flex, and are very lightweight indicating a thin wall, but they say they're "best for centerpulls" which I don't know if that translates into "won't work with aggressive braking using cantilevers". Although there are documented cases of these forkblades used with cantilevers. I want the bottom of the fork to be flexible, like my Vitus fork is, to dull the road buzz and because my riding buddy Kevin and I both believe (after testing with and without stiff front racks) that fork flex helps you go faster, but I don't want the top to be so flexible that I get brake judder. I sure know the Trek fork was flexible, and I did like that. Can you see those pre-raked blades flexing much when you ride the bike/brake aggressively?
Edit: I re-read your thread and you say it's noticeably flexier than the original unicrown fork. That's good!

As for fitting the Pacenti fork crown, I think I can massage them into the right oval. From what I've read, all fork blades start out the same diameter, and then they get smushed into some type of oval. And I've read things saying these can be smushed into the other oval shape - at your own risk, of course.
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Old 06-13-21, 11:01 PM
  #24  
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Originally Posted by scarlson View Post
OK, I guess I was concerned more about getting enough flex. The Toei Special blades are sold on their ability to flex, and are very lightweight indicating a thin wall, but they say they're "best for centerpulls" which I don't know if that translates into "won't work with aggressive braking using cantilevers". Although there are documented cases of these forkblades used with cantilevers. I want the bottom of the fork to be flexible, like my Vitus fork is, to dull the road buzz and because my riding buddy Kevin and I both believe (after testing with and without stiff front racks) that fork flex helps you go faster, but I don't want the top to be so flexible that I get brake judder. I sure know the Trek fork was flexible, and I did like that. Can you see those pre-raked blades flexing much when you ride the bike/brake aggressively?
Edit: I re-read your thread and you say it's noticeably flexier than the original unicrown fork. That's good!

As for fitting the Pacenti fork crown, I think I can massage them into the right oval. From what I've read, all fork blades start out the same diameter, and then they get smushed into some type of oval. And I've read things saying these can be smushed into the other oval shape - at your own risk, of course.
Well, just finished nearly 300 miles last week with a goodly amount of gravel. Even with 700c x 35's it handled nicely, and braking was never a problem with the cantilevers. I'm with you on fork flex helping you go faster. I was skimming the top of washboard with no ill effects. I couldn't see the flex, handlebar bag was in the way.

Double check with Jan on using a different crown than what he sells. Norther told me it wouldn't work, and the website doesn't have any info on the oval dims (must be a secret).
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Old 06-14-21, 01:04 AM
  #25  
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Glad to hear no injury sustained, scarlson. I'm happy to offer a full refund on the frame.
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