Continuing the discussion from Modern Cyclocross Frame vs. Relatively-Retro Pure Road:
Why would a noodle (a flexible bike frame) slow you down? As an Engineer I have some serious problems with this “general” understanding. Could it actually be that a noodle tailored to you would make you faster? Something Jan Heine suggests.
A bike frame flexes, totally true. Some more than others. But is that necessarily a bad thing? Yes it requires your input, but where is that energy going? Some energy is stored into the frame and some is lost (heat) due to damping charactersitics of the material. While moving back to it’s original shape the stored energy can be put into forward motion. See video from GCN below.
From what I’ve found the damping coefficient of metals aren’t high. If one doesn’t deform the material. Thus metals good at storing energy and not good at turning that energy into heat.
Then how would the frame make you faster? I think it has something to do with your power being applied over a broader range. It could even be that the energy you just put into the frame with your left foot is put back into the wheel while your right foot is at it’s dead point. Thus making your pedal efficiency higher.
Jan Heine - better bike frames and “planing”: Triathlon Forum: Slowtwitch Forums
Damping Coefficient - Calculation, Values, FAQ (punchlistzero.com)
Damping capacity - Wikipedia
Documentation of damping capacity of metallic, ceramic and metal-matrix composite materials (utexas.edu)
I recently built a bike with very low “drive train rigidity” but standard levels of torsional rigidity : it has 3mm wide carbon cables where the chainstays should be so the rear end visibly flexes forward when I pedal, while the “down tube” is 60mm diameter so the headtube and seat tubes don’t twist out of plane any more than does a standard frame.
By standard wisdom the lack of drive chain rigidity should mean the bike is a slug. It isn’t.
FWIW the woods I use have the interesting property that the damping factor increases with frequency.
The effects are probably minimal and therefore hard to measure because a metal bike sound enough to be safe under a 100kg+ rider for legal compliance isn’t going to significantly flex under normal pedalling loads.
Between pedals and tires offering minimal resistance, and a steel pipe which is pretty resistant to bending, which is going to absorb nearly all of the force? It might be easier to measure in a situation where there’s a lot of force applied to the cranks (such as climbing out of the saddle on a very steep slope).
However, it is going to be a minimal negative effect because there’s no such thing as a perfect spring and a part of the energy will be lost.
If you want to alter pedal dynamics and perceived problems with deadspots, there are oval chainrings. The evidence of their efficacy is pretty lacking, though.
I don’t know whether they are less efficient, but I have definitely had bikes that flexed enough to be scary in a bunch sprint.
Fascinating topic, I wonder if there is a way to really equate feel for a rider. I always love a super stiff front end as it makes the front end more predictable into turns and provides a solid foundation to press against in a sprint. I put out more watts on a bike with a stiff front end but most of that has to be mental e.g. I feel more comfortable pushing harder since I have a firm thing to push against.
There’s something in this for me as well, a stiff bike just feels faster in the same way that narrow tyres at high pressure do. A bike the feels faster encourages me to then keep putting more effort in. I 100% accept that this is a totally subjective feeling that is not backed up by any kind of proper evidence, heck the evidence would suggest that wider tyres at lower pressures are usually quicker in real world situations.
In the same fashion, a light bike just feels more fun to ride and quicker to accelerate even if the data will prove otherwise.
That’s awesome. Like a reversed SlingShot frame from the 90s.
This is the question I keep asking myself as I get the snot beat out of myself riding my aero bike. I just don’t get the obsession with frame stiffness. I wind up running lower pressures than I would really like on my current bike even with latex tubes + flat-prone Vittoria Corsas to compensate for the lack of vertical compliance. My opinion might be different if I was cranking out 2000 watts. The perfect blend to me would be somewhere between my aero frame and my Ritchey Road Logic, but having said that, I’m not sure that the noodleness of the Road Logic really robs me of power in my not-so-impressive 1200 watt sprints.
There is definitely such a thing as a frame that’s too stiff. I sometimes look at golf, where clubshafts are available in a range of different stiffnesses, and wonder if someone somewhere is missing a trick.
Old Guru’s in custom geo where terrible for this. I almost bought one from a colleague of similar size a while back. Test rode it and it was one of the worst riding bikes I’ve ever ridden (and this is a guy who liked the original Venge Vias). Had a friend who worked for a company that used to sell Gurus and builds his own frames, he was adamant that Guru didn’t really didn’t take into account how different sizes needed different layups, shapes, etc and they just made all the frames the same with longer/shorter tubes, not sure if it’s true but that frame felt awful.
noodle beats rock. pick your favorite beam-like piece of sports equipment. athlete induces elastic travel to load/unload spring, but as significantly for modulation. idk - more ppl are figuring it out. too little travel = brick/rock.
I’d argue the evidence is the exact opposite. Aerodynamically, wider tires are almost strictly worse. There is, afaik, no one seriously arguing against that point.
Rolling resistance is oft cited as the advantage of going wider, but there is no such thing as a free lunch in physics. The advantages in RR (which there still isn’t a test for that is consider scientifically reliable for, which means any claims about RR are still highly speculative) for wider tires only comes from running lower resistances. This is problematic because the lower you go the more watts you lose to hysteresis. It still might be net advantageous, however, on rough surfaces or offroad. The big problem is all claims of superior RR can only be made at the same pressure. When someone says a 36 has better RR than a 25, that is only true at the same tire pressure. This is problematic because nobody would run a 25 at the 40-50psi that the 36 would run optimally. Nor would you run the 36 at the 90psi you would run on the 25. If you inflate the 25 to a more appropriate PSI there is no comparison that the 25 has better RR.
The bike industry has done a couple of tricky things here. First, they tried a few years ago to sell us wider rims and wider tires at lower PSI as more comfortable (very likely true) but turns out that sales pitch doesn’t quite sell to the race oriented roadie market. So they changed to just telling us that wider is actually faster when we know from wind tunnels, track racing, and outdoor TTs that narrower is faster. And $omehow they managed to convince cycling media to accept these unfounded claims hook, line, and sinker. The key point here is this: they went wider first, and then retroactively looked for “science” to justify the decision they’d already made.
The second trick was the switch to hookless. Hookless is only safe at low PSI. Meaning they really cannot sell you a safe 21 or 23 hookless rim. If you run 23 tires on a hookless rim you’d have to run them at low enough tire pressure that it would feel like you’re riding on flats. Hookless requiring low PSI means they need to make them wide enough that low PSI stops becoming a problem and becomes advantageous to the system, hence wider. Why do all this? Money, probably. A $2000 pair of hookless rims probably saves them $50 per pair vs hooked. So yeah, they are selling you wide, slow, hookless rims and laughing behind your back that you accepted the idea that they’re faster. Then again, I’ve seen a lot of “reputable” wheelbuilders on youtube repeat the “gospel” of wide hookless rims so they seem to be drunk on their own kool aid.
If the bike industry can convince you that running a 32 tire at 50psi is faster on a decent paved road than a 25 at 90psi, you’re a sucker and I’m sure the brands will be happy to sell you a $13,000 super bike that’s slower than the models from 5 years ago.
Jesus…here we go again with the insane “bike industry makes us buy things” nonsense.
As someone who worked in the business for over 10 years, I can tell you it is complete nonsense.
Everyone who races knows 25s are usually a Goldilocks width for road and crit racing, very few people above cat 4 lining up on road race days with 28-32mm+ tires at super low pressures and usually when that occurs the course calls for it. Wider widths make a lot of sense when racing or training over subpar roads surfaces and in foul weather condition in the same way having a pickup truck is great when you live in an area with poorly maintained roads. Road hookless is a load of bologna mostly geared towards clueless 50+ guys with beer bellies who buy lightweight titanium water bottle bolts and simpletons who buy any trending ceramic coated headset nonsense.
That being said I think you’re confusing the competitive road cycling industry with an industry that is filled with competent and strategic companies vs what it really is which is actually mostly a cottage industry filled with a mish mosh of companies that throw spaghetti at the wall who can’t make two circular holes in alignment with one another for $5000+
I should have explained in more detail, come ride the poorly maintained British roads as we’re coming into winter, a 28 at 70psi is faster than a 23 at 100psi.
When racing or on the track, yeah narrow and high pressure still rules. The vast majority of my riding isn’t in that scenario though on those well maintained surfaces.
Jeez I’m glad I only have the titanium water bottle bolts and none of the rest…
In theory, a CF frame could be engineered to be torsionally stiff so it doesn’t twist and bend sideways under pedalling loads, but vertically compliant so it doesn’t beat you up, but given many manufacturers struggled making press fit bottom brackets to acceptable dimensions with aligned BB shells, I’m not 100% sure that universally happens as intended. In house, we lucked out and three out of three CF frames are all pretty comfortable and have been trouble free.
As far as tire width, 25mm is pretty much ideal, which doesn’t work optimally with hookless pressures. Even cycling press has started to test the actual speed on normal roads and found 32s to be slower.
Of course normal road highly depends where you live.
^This is it.
People are looking for absolutes and there just aren’t any. On perfect, velvet roads, 23c (or less) will be fastest, but as the roughness increases, so does the ideal size. In a real world/road scenario, 28 is the goldilocks point for most riders, but even then things like rider weight come into play.
Basically, the kind of aerodynamic drag differences being discussed just aren’t relevant for most of us.
Unless you’re routinely riding round at an average of over 35kph then you won’t feel a difference in speed between a 28 and a 32 of the same tyre. It may well exist, but for most of us, it’ll be tiny. The same goes for the wider vs narrower rim argument; at least as far as aero goes, any gain/loss at typical club speeds will be very marginal.
You’d see a bigger difference by shaving your legs and switching to an aero helmet.
If you’re a decent racer, have at it, but if not, just don’t worry about it.
Glad i’m a clueless 50+ so i dont know im being insulted
Can you really tell if a frame is stiff or noodley ? there are so many other factors that can add comfort or make the bike feel flexy under power.
Tires, wheels and how they are built, seat post, seat rails, cranks, bars, stem, any one item could change how a bike feels.
Most bike journalists are nothing more than university graduates that liked riding bikes so worked for bike mags/ websites, when they are spewing bullsh*t about frame stiffness and feel they are just reading the manufactures blurb and regurgitating it.
As for tire size pick what you like they all work at some point in the RR and aero spectrum, personally i’m a 28 on hookless guy, works for me. (oh i’ll run 30’s on the winter bike)
I dont have a problem being marketed to, thats capitalism. the problem is selling me a less safe, slower bike and telling me its actually faster and just as safe when they know its patently untrue.