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Comment by paulgb | Hacker News Reader

Here's a reddit comment that I found insightful around the claimed issue with disk breaks in combination with quick release: https://old.reddit.com/r/ebikes/comments/we4fgv/radpower_bei...

It links to this useful diagram: https://ibb.co/HP0HxVV

I'm not a bike expert, but I do notice that in comparison to my bike (which also has QR and disk breaks), the RadRunner 2's dropouts are more downward-facing.

The lawsuit is dubious for a lot of reasons, but the point about quick release is more interesting than I expected.

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I've never had a problem, but I've joked that all of my QR equipped bikes (which all have disc brakes) have "lawyer tabs" for years. Kids bikes have them too.

It goes around the skewer into an additional small hole on the bike with the intent that it will hold if the QR is slightly loose. I don't think it would save you, but it is there.

Check your wheel tightness once in a while, everybody.

I have been cycling sportively (MTB, road) for about two decades. Bounce your bike. Just a couple of bounces on the wheels. It’s just a thing where you would instantly notice any slack on the wheel tension.

Another trick: engage the brakes, one at the time and rock the bike forward and backward, any slop will instantly show up (sometimes in places where you really don't expect it).

You can find a lot of issues really fast by simply looking and listening while picking up and dropping a bike. I've been doing it subconsciously for years.

The issue with the particular quick release that was deemed to be problematic is that it allowed opening so far that it could end up in the brake disc rotor. The 'lawyer tabs' prevent the whole wheel from dropping out if the quick release accidentally activates, they don't prevent the release itself from opening.

Most bikes with vertical dropouts have some kind of retention cutouts, so that if the QR was properly installed (i.e. holds the wheel on when closed), the QR is retained even when fully opened. You need to open it fully, then unscrew the cap a bit to make the nuts on both sides far enough apart to get outside the retention.

I don't know if that is the case on the RadRunner 2, but it's the case on most road bikes with vertical dropouts.

Some bikes made today with front dropouts have an additional horizontal boss added to the dropout to help prevent this pulling out from the dropout when normally tight, but it won't prevent a loose wheel from getting pulled out.

Bikes with rim brakes aren't immune to this either, but disc pads seem in a more optimal place to cause it, ad might grab more quickly ( jerk force).

In every bike I remember having the dropout were facing forward and slightly upward

Correction: slightly downward

I've built a few bicycle frames and it's a known issue among framebuilders that you should point the opening of the front dropouts rearward a bit on disc brake forks. Disc brakes can generate serious torque.

Wouldn’t rearward make the problem worse? If you imagine slamming on the front break, the wheel wants to stay put while the rest of the bike wants to move forward. If the dropouts face rearward and the QR has wiggled loose, there’s nothing to stop it from slipping backwards.

No. The issue is with the torque of the brake pulling the wheel out of the dropout. Changing the angle of the dropout changes this.

Look at figures 3 and 4 on this article: https://cyclingtips.com/2015/10/road-bikes-are-headed-toward...

What is needed is the dropout not aligning with the direction the axle is forced when the brake is applied.

Figure 4 shows the front dropout facing down and forward, not down and back. I agree that down and forward makes more sense in terms of preventing the axle from moving. the middle image in fig 4. says that the axle is moved down and to the rear during braking as the brake pad acts as a pivot point.

If the dropout faces rearward enough it'll still be effective. What needs to happen is the dropout needs to not allow the brake pad to be the pivot point for removal. But a rearward wheel removal path is problematic for other reasons: hitting the downtube during removal, requiring caliper removal to allow the rotor to clear, etc.

When properly locked, QR axels don’t go loose (regardless of brake type). Unless your sending 20ft kickers into rock gardens, QR is fine.

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