How can you tell if a fork is slightly bent?

[phcollard]

Anxious mind needs your help :)

Sometimes when I look at it that fork seems slightly bent back, sometimes it looks alright. It's driving me nuts a little. I could take it to a local framebuilder but that's an hour drive and I don't have a car. I tried to measure the rake and I found 38mm... but that could be an error from my not-so-scientific-process.

Picture here https://dl.dropbox.com/u/3032014/IMG_0761.jpg

Thanks a lot!

Philippe.

[FlashUNC]

I can see how you're going snowblind staring at that thing.

Maybe another approach, have you pulled the fork and checked for any damage around where the steer tube joins the fork crown?

[phcollard]

I can see how you're going snowblind staring at that thing.

Maybe another approach, have you pulled the fork and checked for any damage around where the steer tube joins the fork crown?

LOL yes sorry for the reflective logos on the sidewalls!

I did not notice anything at the joint but I admit I did not look too close. Plus the crown race was already installed and I did not want to pull it.

[FlashUNC]

I can see your point though. I hold my head one way, fork looks fine. But then, like a Monet or Picasso, I really start to look at it, tilt my head a bit, and something seems off.

But then that could be just because I'm staring at the stupid thing.

[oldpotatoe]

Anxious mind needs your help :)

Sometimes when I look at it that fork seems slightly bent back, sometimes it looks alright. It's driving me nuts a little. I could take it to a local framebuilder but that's an hour drive and I don't have a car. I tried to measure the rake and I found 38mm... but that could be an error from my not-so-scientific-process.

Picture here https://dl.dropbox.com/u/3032014/IMG_0761.jpg

Thanks a lot!

Philippe.

I think you answered your own question...frame builder that has a fork jig.

AND if it is, he can probably straighten it.

I hesitate to say anything BUT it looks a little 'aft' to me. From the pic. I would carefully check to see if there are any bulges right behind the lugs on the top tube and down tube also, bottom part of tubes. ...

May feel them more easily than see them.

[phcollard]

I think you answered your own question...frame builder that has a fork jig.

AND if it is, he can probably straighten it.

I hesitate to say anything BUT it looks a little 'aft' to me. From the pic. I would carefully check to see if there are any bulges right behind the lugs on the top tube and down tube also, bottom part of tubes. ...

May feel them more easily than see them.

Thanks Peter. No bulge behing the lugs!

[phcollard]

By the way, what's the rake supposed to be? 43mm?

[jtakeda]

Looks bent.....

[phcollard]

Looks bent.....

Damn :( :( :(

I built the bike yesterday https://dl.dropbox.com/u/3032014/build.JPG

Looks like I have to remove that fork now...

[EricEstlund]

A small degree of "rear angle bias" may not be a bent fork.

If the fork blades are over raked for a given length and loaded up/ brazed as normal for a given offset, the upper straight section may angle back slightly from the steering axis. You see this fairly regularly with production forks to varied degrees.

That said, fork offset can be tricky to measure (especially in the bike). If you are 5mm off from projected it is likely front-ended.

[phcollard]

Thanks Eric. That's reassuring to read.

I must say I've been looking at pictures of similar Merckx bikes for over an hour and half of them have a fork that also looks slightly aft in the upper straight section.

I told you I was an anxious guy :)

[rodcad]

After crashing my fixed gear, bike rode cockeyed big time. Nothing visible was off per a couple of shops. Took frame to local framebuilder Mark Nobilette who said frame was fine the fork was just jacked. He straightened it and bike rides like a dream again. Try that with your carbon fork....:no:

Stick the fork in a backpack, grab another bike and have yourself a nice ride to your local builder. Be nice if framebuilder could fix on the spot for you.


Good luck!

[phcollard]

After crashing my fixed gear, bike rode cockeyed big time. Nothing visible was off per a couple of shops. Took frame to local framebuilder Mark Nobilette who said frame was fine the fork was just jacked. He straightened it and bike rides like a dream again. Try that with your carbon fork....:no:

Stick the fork in a backpack, grab another bike and have yourself a nice ride to your local builder. Be nice if framebuilder could fix on the spot for you.


Good luck!

Thanks! I love the idea but a ride to the framebuilder is more than a century :D and it's starting to be freezing cold here up north.

I might ship it to a framebuilder in the US, it would cost less than renting a car. But I'll try to ride the bike first if weather permits, see how it handles.

[keevon]

Dissenting opinion: it's an optical illusion. I've noticed this with a lot of curved steel forks, both custom and production.

Stems too: to my eye, a 90* stem never actually looks like a right angle to the head tube. Must have something to do with the change in diameter from the HT to the steerer tube...

At any rate, wouldn't it be really tough to bend a fork straight back like that? The fork would have to bend right at the crown race, which seems highly unlikely. In my experience, a head-on collision either A) bends one or both fork blades out of plane, so the wheel doesn't sit straight, or B) crumples the TT and DT just behind the HT.

If the wheel sits straight and there's no frame damage, I'd say it's fine. But I'm not a framebuilder...

[rodcad]

Thanks! I love the idea but a ride to the framebuilder is more than a century :D and it's starting to be freezing cold here up north.

I might ship it to a framebuilder in the US, it would cost less than renting a car. But I'll try to ride the bike first if weather permits, see how it handles.

You gotta suck it up! ha ha :banana:

[rodcad]

send it all the way here? Im sure Mercian Cycles and plenty of other help is availble "on your side"?

[phcollard]

Dissenting opinion: it's an optical illusion. I've noticed this with a lot of curved steel forks, both custom and production.

Stems too: to my eye, a 90* stem never actually looks like a right angle to the head tube. Must have something to do with the change in diameter from the HT to the steerer tube...

At any rate, wouldn't it be really tough to bend a fork straight back like that? The fork would have to bend right at the crown race, which seems highly unlikely. In my experience, a head-on collision either A) bends one or both fork blades out of plane, so the wheel doesn't sit straight, or B) crumples the TT and DT just behind the HT.

If the wheel sits straight and there's no frame damage, I'd say it's fine. But I'm not a framebuilder...

I like that. I was wandering too if it could be optical illusion. Tonight I'm seeing two friends who both own a Corsa Extra. I'll check their bike - before we empty a bottle(s) of red lol.

The wheel sits indeed straight. Right in the middle at the crown.

I have no experience with front crash but I'm guessing, as you said, that even if the fork was minimaly out of whack the wheel wouldn't be centered.

[phcollard]

send it all the way here? Im sure Mercian Cycles and plenty of other help is availble "on your side"?

US builders do it better :D

Kidding aside it's more than often less expensive to ship something to the USA than within our own country. And it's still cheaper than car rental. But yeah, I could man up and ride 200km in the freezing rain :)

[David Kirk]

So do we know that the rake should be for this fork? Does a properly dished wheel sit centered between the blades. When viewed from above does the fork appear to twist or corkscrew as it goes down to the wheel?

dave

[Chance]

Sometimes when I look at it that fork seems slightly bent back, sometimes it looks alright.

Philippe, if you had not brought it up first there is no way that fork would look unusual enough to me to have noticed on my own. Covering up the bottom of the fork where the rake is, the rest looks straight. Or as straight as any other fork. Rake can have an optical illusion as others have mentioned.

As to rake, measuring fork rake accurately yourself is very difficult. Have had best luck doing it with fork installed on the bike. Your idea to ride the bike first seems like a good one. Good luck.

[youngman]

Philippe,

If you take your picture of this frame with fork and put it in an editor like paint and plot a dissecting line through the center of the headtube and down the fork it looks good to me.

[phcollard]

I wanted to thank you all for the replies and for the reassuring thoughts.

I rode the bike yesterday night to my friend's. Of course it's not like going on a real training ride but the bike seemed to handle fine. From now on unless I'm real lucky it's gonna be too cold/rainy/snowy here in Montreal for a serious ride so I'll have to wait until Spring to be 100% sure, but I guess it's gonna be OK :)

I also checked with my friend's 3 Merckx - all Corsa Extra - and I have the same visual impression that their fork was slightly aft so that must be a Belgian thing.

Thanks again and a great weekend to you all!

Philippe.