How Does Hub Engagement Affect Pedal Kickback? | #AskGMBNTech

Welcome back to another episode of Ask GMBN Tech, where we try to answer all of your complex, scary, niche, and technical questions about mountain bikes and MTB-related tech! - ⏱ Timestamps 👇
00:00 - Intro
00:21 - Does the amount of hub engagement points affect pedal kickback?
04:55 - Thick Tyre and No insert or lighter tyre with insert for Enduro riding?
07:30 - Why Can’t companies just make hubs with higher POI? Can’t you just put a bigger drive ring into the hub?
08:37 - Why is the weight difference not that high between aluminum Vs carbon wheels? I’d like carbon for energy transfer but can’t make up my mind to pay 2k for a similar weight?
11:01 - What are the advantages of building wheels in 2 cross, 3 cross or 4 cross?
12:20 - How to pick tire compound, casing, tread and width for winter? Or does it matter?
13:35 - I would love to see a visual comparison between 2.4/5/6 tyres on various rims to see how this affects the profile of the contact area.

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[gmbntech]

Do you have an MTB-Tech-related question for Doddy or Anna? Use the hashtag #AskGMBNTech with your comment for a chance to be featured on the channel! 👇

[thecakeisalie]

The pedal kickback works the other way too. When climbing, the hub is rotating slow and so when the suspension sags under load, you get a firm platform to pedal and in effect, you prevent the rear suspension from sagging. There's also antisag to take into consideration and if your frame was designed well, this makes it a great climber. It's something super hard to test in a parking lot so make sure you're test riding in real world scenarios!

[Justin-nyun]

In regards to spoke crossings. 2x provides more lateral stiffness, 3x provides more radial/torsional stiffness.

I just had some 29er wheels built which were built 2x and I was expecting 3x, as I thought 3x was standard and strongest.

Nox Composites, Nobl and Enve make 29ers in 2x as standard.

The order which effects rim stiffness is apparently:
The rim stiffness
The number of spokes
The spoke bracing angle
The gauge of the spokes
The lacing pattern

There is little difference in spoke fatigue between them.

[markpeterson]

Brilliant episode Anna! I love the amount of technical knowledge you share in a way that people, well most people, can understand. Thank you for exhibiting ways to understand multifaceted problems in a way that is easy to absorb. Great Job! I hope to see many more episodes from you with your keen knowledge and sensible delivery. Cheers!

[sjaan]

Single pivots are the worst for pedal kickback and brake jack.

[rupedog]

My hub is 3deg..too much really for my bike. I think Hopes 6deg is a good sweet spot.

[jasonduboise]

Live my spank 350 vibracore with Hex 101 pt engagement. Love these wheels. A year and a half clean and grease and check spoke tension now and then. Stiff, burly reliable and the vibration feedback slightly less. I run these in my tail bike and beat them in everything including some street.

[cg]

I had hydra hub with my yeti sb165 …. Bad combo with the suspension on hard descent and braking…
Suspension was way Better with 36 points of dt Swiss

[niclaskarlin]

10:50 Note that those grams are rotating, so you're only able to change spokes and tyre. And hubs perhaps.

[rupedog]

V thorough Anna... Good job of keeping the tech end up while Doody gets over the rona (literally doing the same myself😞😷)

[alainmilot]

Thanks a lot for the detailed answer! You're the best

[gogovitch]

great questions, great answers! 🙌🏽 THX! :)

[oTUFTYo]

I had a big issue with knocking on my trek rail when I put Halo Rims and Hubs on. On techy descents where the shock travel was fair and speeds lower I would get loud knocking through the motor and sounded horrible, Also the rear suspension felt terrible. Took me a while to realise the issue and look into it. I replaced the wheels with Hope less than half the engagement of the Halo and the knocking has all but gone and the feel of the rear suspension is totally different.

[thescandiflick]

#AskGMBNTech Hey Anna & Doddy A subject that I didn't see anyone talk about yet or maybe I just can't find any valuable information around this subject.

Pressure relief valves on forks, As we have seen this little piece technology used by Fox now its been introduced in the new lineup of 2023 Rockshox Forks. Rockshox have just released their upgradable pressure relief valve kit and I have a 2023 Pike Select Debonair+ that doesn't come with the valves but upgradable.

How do they work in a real MTB scenarios ? Is it really worth the upgrade or just any piece of accessory ? Any noticeable change in performance?

Greetings from Denmark

Cheers!

[simonhutchings]

If you’re riding somewhere like chamonix DH casing!

[TheButlerNZ]

I would really like to see a mathematician sit down with a bike that suffers "Pedal Strike" and do the math on what speed the strike would become impossible..
A lot of people I have seen explain Pedal Strike give examples when the rear wheel is not rotataing, so of course a change of chain length would pull the top of the front sprocket back toward the stopped (Fixed position) rear hub/sprockets...
But in the real world, you would NEVER have the rear hub fixed, it would be rotataing forward at the RPM speed of the wheel.

At some point, the speed forward of the top of the rear sprocket will match the rate of 'Pull" on the chain.
(i.e the forward rotating sprocket is always ADDING chain links to the top so a chain strike caused by a reduction of chain links across the top will at some speed, be matched/surpassed...)

Basically... is there a speed you can travel at that adds more links than the hit that subtracts them...
My brain hurts just thinking about it so I'm not up for the math.!

[steezyreezy]

#AskGMBNTech Hi, I would like to ride my eMTB (specced like a bikepark-enduro bike) in a bikepark but without the battery as I do not have to pedal that much. Does the structual integrity allow that? I dont think the battery is a structual part, right?

[tomshort]

#AskGMBNTech Hey Anna and Doddy -- I'm considering a SRAM DUB crankset and was wondering if it will work with my current SRAM GXP bottom bracket. Will it swap right in or might I need a new BB? I can do all this myself because I watch your show!
Always enjoy the info. Cheers

[blusoda]

Am I right in assuming that some racers also use lower engagement hubs as they, (while only slightly) have less friction?

[thim]

I bought an alloy levo frame and wished I would have bought carbon. I can feel the quality difference in weight and dampening.