I'm surprised we haven't seen/heard of someone experimenting with these geometry concepts yet in a more rigorous way. It would only take a few folks with...
I'm surprised we haven't seen/heard of someone experimenting with these geometry concepts yet in a more rigorous way. It would only take a few folks with welders who were bored in lockdown (or a big company with R&D money) to more systematically test this. At a minimum, you could build a rigid or hardtail frame with a concentric BB, sliding dropouts or multiple dropout holes at different heights/lengths/angles (aside: angled sliding/flip-chip dropouts would move two things at once, and seems like a good idea for a bike designed around full 29 and mullet) and a headtube with a reach adjust headset. Then, test times as stated above on straights, bumps, high/low speed, berms, flat corners, etc and compare times.
This actually sounds like something a YouTuber would do, but I wonder if anyone at the big companies has ever tried this to see where they actually want the geometry to be instead of just following industry trends. Minaar mentioned a few years ago that he thought his bike should be longer but that people need time to adapt/accept the change, but do the bike companies know where the limit is? Or maybe the limit does not exist.
You can bet your ass companies do this, but this is what makes the knowhow their secret sauce and their products better. So you won't see it published much. Spec had a headangle/reach mule of a gravel bike, the Enduro mule looked https://ep1.pinkbike.org/p4pb17581909/p4pb17581909.jpg, etc.
Having some welders is one point, they need to know what to weld. And a YouTuber is the exact person who would have the reach and maybe the means to pull it off, if said youtuber isn't sponsored by a brand, but I don't think the ones with the reach and means have the knowhow. And vice-versa.
T do things properly, even with a welder, jigs and material on hand, it would still take a couple thousand euros to throw together a few frames to test things out.
[i][b]Please don't try to argue against basic physics.[/b][/i]
Not arguing with physics but are you sure we are taking all the variables in consideration ? For...
Please don't try to argue against basic physics.
Not arguing with physics but are you sure we are taking all the variables in consideration ? For instance, common practice is to measure tire pressure unloaded right ? Additionally we can agree that for the same tire section, the total air volume will be bigger for a 29 wheel than for a 27.5 wheel. If my physics is not too rusty, air pressure increase exponentially in a given volume and the bigger the volume the more displacement will be needed to end-up at the same pressure. So considering that initial pressure, loading and tire section are kept constant, in order to reach the same loaded pressure the 29er will have to displace more volume (contact patch) more than the smaller wheels. Effect that would be exacerbated by the bigger tire area likely to stretch under pressure increasing even more the space available for the air to spread.
I think the physics arguing was just the usual internet hot headnedness (I know I'm guilty of it way too often, this was one of the cases where it reared up a bit if I'm honest), but you do have a point. Not sure how good it is, but it is true. As for the good part, I'm not sure the change in volume and change in pressure when loaded is large enough to play that much of a role in it all. As in I think setting pressures at room temperature (or so) in the garage and then going out to ride at 0°C or +30°C will have a bigger effect on the change in pressure than sitting on the bike.
Does anyone have some tyrewizes?
And since I'm editing, BRB, I'm going to check it with the schwalbe digital pressure gauge.
EDIT2: back, there is virtually no change or within 0,01 bar. EX511 with a 29x2,5 WT Assegai, EXO, dual compound, sealant and ARD inserted, measured between 1,39 to 1,35 bar, the main cause for pressure changes was loss of air when attaching the gauge. Sitting on the bike or not didn't make a noticeable difference.
JamesR_2026 I don't buy that the increased gyroscopic stability of 29ers would help them absorb square edge bumps better. The only way for a wheel to absorb a square edge bump is for it to get out of the way- the wheel has to change direction to move up and over the bump. Increasing wheel weight and gyroscopic stability, if anything, will make it harder for a bigger and heavier wheel to move up and over a bump. All else being equal, a smaller lighter wheel with less gyroscopic stability will get up and over little bumps better.
But, obviously, all else isn't equal. If you're asking me to ride down a rocky trail in a straight line and I get to choose between 29" wheels, 26" wheels, 24" wheels, or 20" trials tires, it's not a tough choice, even though the 29" wheels are heavy. And the reason why a 29" wheel rolls over bumps in a straight line better than a 20" wheel is because the tire on the 20" wheel is hitting the bumps at a less favorable angle.
A wheel with less rotational inertia will move out oft he way better and be pushed back down by the suspension more easily. Doesn't mean it won't hang up on the obstacle less though, the heavier wheel does have more energy.
I'm not discounting the rotational energy of the bigger, heavier wheels, far from it. I think it's an important factor in the story.
I agree with point above, but i feel the gyro-effect is to easily dismissed. Because a square egded obstacle will not allways be 90 degress angle to your tires, right? So a stability effect would make a difference in feel over a small bump between a smaller and bigger wheel. And this feeling could be attributed to ease of going over rough terrain, no? Bigger obstacles then 2 inches would be picked up by suspension and or the body, maybe Even pressure.,
Sorry for being a pain in the rear(pun intended) here, but i think this should not just be contributed to the bigger/smaller wheel just because it is bigger in diameter, and not account for other factors that are in play here - also because the diameter is bigger, but what that actually means.
I think what makes a mullet better, is that the front and rear are different sizes, but they have different proporties that play a bigger part in the feel then just arch and diameter. Of course it all have a part to play in the feeling, or handling if you will.
1. the wheels have different proporties.
2. the center of these proporties form a line not paralell to the ground. In favour to us going down hill and having some sort of connection a want of being level(maybe? Or something like that)
3. the line that these centers forms arr closer to the point where the mass is connected to the bike, (without raising the bb)
I can't imagine a scenario where the non-horizontal line through the two axles has a role in anything. After all, by that logic, just going down a slope should change things.
And if anything, this sloping line will be lower, while the rider CoG is much higher, so it's further from it, not closer.
That's super cool to see that Specialized was doing actual testing on reach length vs. stem length to see how they affected steering. Always cool to see real test mules to do back to back testing. So much of bicycle geometry conventional wisdom is just guesswork and accidental discoveries. Curious what they discovered. Obviously, they chose to go with longer reach lengths and shorter stems across the whole diverge lineup, but I wonder if they found a "too-short" stem length for road bikes.
Having some welders is one point, they need to know what to weld. And a YouTuber is the exact person who would have the reach and maybe the means to pull it off, if said youtuber isn't sponsored by a brand, but I don't think the ones with the reach and means have the knowhow. And vice-versa.
T do things properly, even with a welder, jigs and material on hand, it would still take a couple thousand euros to throw together a few frames to test things out.
Does anyone have some tyrewizes?
And since I'm editing, BRB, I'm going to check it with the schwalbe digital pressure gauge.
EDIT2: back, there is virtually no change or within 0,01 bar. EX511 with a 29x2,5 WT Assegai, EXO, dual compound, sealant and ARD inserted, measured between 1,39 to 1,35 bar, the main cause for pressure changes was loss of air when attaching the gauge. Sitting on the bike or not didn't make a noticeable difference.
But, obviously, all else isn't equal. If you're asking me to ride down a rocky trail in a straight line and I get to choose between 29" wheels, 26" wheels, 24" wheels, or 20" trials tires, it's not a tough choice, even though the 29" wheels are heavy. And the reason why a 29" wheel rolls over bumps in a straight line better than a 20" wheel is because the tire on the 20" wheel is hitting the bumps at a less favorable angle.
I'm not discounting the rotational energy of the bigger, heavier wheels, far from it. I think it's an important factor in the story.
Sorry for being a pain in the rear(pun intended) here, but i think this should not just be contributed to the bigger/smaller wheel just because it is bigger in diameter, and not account for other factors that are in play here - also because the diameter is bigger, but what that actually means.
I think what makes a mullet better, is that the front and rear are different sizes, but they have different proporties that play a bigger part in the feel then just arch and diameter. Of course it all have a part to play in the feeling, or handling if you will.
1. the wheels have different proporties.
2. the center of these proporties form a line not paralell to the ground. In favour to us going down hill and having some sort of connection a want of being level(maybe? Or something like that)
3. the line that these centers forms arr closer to the point where the mass is connected to the bike, (without raising the bb)
And if anything, this sloping line will be lower, while the rider CoG is much higher, so it's further from it, not closer.
https://bikerumor.com/2020/05/07/first-look-all-new-2021-specialized-di…
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