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-   -   Front Fork Dropout Position (https://www.bikeforums.net/general-cycling-discussion/1208427-front-fork-dropout-position.html)

taylorgeo 07-25-20 04:29 AM

Front Fork Dropout Position
 
Why are some dropouts positioned down (towards the ground) and some more forward facing?


2021 Jamis Hudson Series
https://cimg7.ibsrv.net/gimg/bikefor...fd874d0f42.png


2021 Jamis Divide (Hardtail MTB)
https://cimg8.ibsrv.net/gimg/bikefor...8221a6d042.png

Moe Zhoost 07-25-20 06:26 AM

Technical note: Those are not dropouts, they are fork ends. Dropouts are used in the rear to allow removing the wheel without derailing the chain.

To answer your question, I think the angle of the fork end is integrated with the design of the fork to ensure the amount of desired trail.

trailangel 07-25-20 07:43 AM

I call them dropouts.
Has nothing to do with fork offset.
Keeps the wheel from coming out of the forkends when using a disk brake.

rollagain 07-25-20 09:31 AM


Originally Posted by trailangel (Post 21606060)
I call them dropouts.
Has nothing to do with fork offset.
Keeps the wheel from coming out of the forkends when using a disk brake.

Which one does that? They both have discs.

fietsbob 07-25-20 12:02 PM

Physics
 
Torque center of a disc brake wheel shifts from the axle the wheel rotates around,

to the brake pads where they are grabbing the disc, when you apply the brakes. so its less likely to eject a wheel

when the force arc around that axis meets a closed end rather than an open one..

Not done often , but if the disc brake caliper were placed on the front of the right fork blade,

when you apply the brakes, the forces are pushing the wheel axle into the fork tip, not out of it,
as it is on a downward facing opening on most fork tips.


Keep your Front QR Skewer Tight & the Lawyer's Lips fork tips should be sufficient to keep the wheel from being ejected...

also put the QR lever on the side opposite the disc unlike either picture you show.

People have closed the QR lever into the disc, then sued the bike company because they did that..




...

dsaul 07-25-20 12:47 PM

The second example is a correctly oriented dropout slot for a disc brake fork. It prevents the rotational force from the disc rotor from ejecting the axle from the slot under braking. The first example is normal for non-disc forks and is apparently still being used because that's the way it was always done in the past. Its not inherently dangerous with a properly secured QR, but forward facing dropouts are safer.

By the way, I build forks and the term used by all parts manufacturers for the pictured part is "dropout". The slot orientation has nothing to do with the fork axle offset, which is erroneously referred to as "trail" by many in the cycling industry. .

indyfabz 07-25-20 01:04 PM


Originally Posted by dsaul (Post 21606510)
The second example is a correctly oriented dropout slot for a disc brake fork. It prevents the rotational force from the disc rotor from ejecting the axle from the slot under braking. The first example is normal for non-disc forks and is apparently still being used because that's the way it was always done in the past. Its not inherently dangerous with a properly secured QR, but forward facing dropouts are safer.

By the way, I build forks and the term used by all parts manufacturers for the pictured part is "dropout". The slot orientation has nothing to do with the fork axle offset, which is erroneously referred to as "trail" by many in the cycling industry. .

Very informative. Thank you.

shelbyfv 07-25-20 01:21 PM

Another reason disc brake bikes should have thru axles. And I'm sure they will once the manufacturers use up the old QR forks.

unterhausen 07-25-20 01:26 PM

Disc braking forces will tend to remove the wheel with downward facing dropouts. That Jamis must have some fairly robust lawyer lips. Some disc dropouts face forwards quite a bit. Looks weird, but it works.


Originally Posted by Moe Zhoost (Post 21605985)
Technical note: Those are not dropouts, they are fork ends. Dropouts are used in the rear to allow removing the wheel without derailing the chain.

Not in the U.S., maybe in the U.K.

Rear dropouts, fork/front dropouts. Look on any framebuilding supply website.


Originally Posted by shelbyfv (Post 21606568)
Another reason disc brake bikes should have thru axles. And I'm sure they will once the manufacturers use up the old QR forks.

This can't be why Jamis is using QR, all that stuff is made new every year. Jamis is weird though. I suspect it costs a little more to make a decent TA fork because you can just slap something together for QR forks and bend it into shape, whereas TA has to be built better to begin with. Although I have seen some really misaligned TA drops and there isn't much you can do about it. Particularly on the rear of a low-end aluminum Trek.

taylorgeo 07-25-20 03:04 PM


Originally Posted by dsaul (Post 21606510)
The second example is a correctly oriented dropout slot for a disc brake fork. It prevents the rotational force from the disc rotor from ejecting the axle from the slot under braking. The first example is normal for non-disc forks and is apparently still being used because that's the way it was always done in the past. Its not inherently dangerous with a properly secured QR, but forward facing dropouts are safer.

By the way, I build forks and the term used by all parts manufacturers for the pictured part is "dropout". The slot orientation has nothing to do with the fork axle offset, which is erroneously referred to as "trail" by many in the cycling industry. .

Thanks so much for this extremely important information. Learning so much from all of you. Being 350 lbs., do you think I should get thru-axles, or will the forward facing dropouts be sufficient? Will be riding mainly on paved streets, but with a fair amount of potholes.

Looks like I'm staying away from the Jamis Hudson Series with the rigid fork. There's a cheaper model though (with the same fork obviously), but it has RIM BRAKES... Maybe that'll work?

taylorgeo 08-15-20 05:22 PM


Originally Posted by dsaul (Post 21606510)
The second example is a correctly oriented dropout slot for a disc brake fork. It prevents the rotational force from the disc rotor from ejecting the axle from the slot under braking. The first example is normal for non-disc forks and is apparently still being used because that's the way it was always done in the past. Its not inherently dangerous with a properly secured QR, but forward facing dropouts are safer.

By the way, I build forks and the term used by all parts manufacturers for the pictured part is "dropout". The slot orientation has nothing to do with the fork axle offset, which is erroneously referred to as "trail" by many in the cycling industry. .

Thanks for the info! Which suspension forks are more durable, coil or air?

Koyote 08-15-20 05:51 PM


Originally Posted by taylorgeo (Post 21606722)
Thanks so much for this extremely important information. Learning so much from all of you. Being 350 lbs., do you think I should get thru-axles, or will the forward facing dropouts be sufficient? Will be riding mainly on paved streets, but with a fair amount of potholes.

Looks like I'm staying away from the Jamis Hudson Series with the rigid fork. There's a cheaper model though (with the same fork obviously), but it has RIM BRAKES... Maybe that'll work?

Especially with disc brakes, thru-axles are preferable, and perhaps very useful at your weight. With that said, I have one bike with discs and qr levers and have had no problems - though I am <170 lbs.

If you do use quick releases, I suggest that you get a good set of internal cam levers such as those offered by Shimano.


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