[Closed] Steel bikes going against the curve

I wonder if Dirt had any Strange 29ers in for testing at the same time?

I was thinking these might be the closest thing to the Starling in ride feel - rather than the Cotic being comparable just because it's steel.

Though Cotic were talking up the flex in their bike as a positive in a recent email IIRC.

You also need to consider that lateral flex and movement also influence comfort, as well as handling, grip, and the intensity and frequency of impacts that make it further up the structure and to the rider, whether that movement comes from tyres, frame, bars whatever, the point being that even 'vertical' input forces are not totally vertical in the dynamic system that is a bike and rider being ridden, leant and moved in the way it does.

If lateral flex allows some component of the impact/input force to be absorbed or deflected than it lessens or diverts the remaining forces and can have a profound impact on feel, handling and comfort, you certainly mustn't think of it in such a rigid 2-dimensional way as vertical=comfort, lateral=other

It's also wrong to think that because tyres are big and squishy that they absorb forces to the point of them not making it through the the frame, it doesn't work like that in real life. Sure they have a BIG impact on all aspects of handling and comfort, but forces will still be transferred, tyres are not a perfect suspension, and the frame and all attached contact points are then 'in play' as well.

As others have said, the vertical flex in frame is actually pretty small and irrelevant compared to the other aspects, it's there for sure, but not to the degree some people think, and a bike is rarely vertical, even in a straight line there is leaning and such going on, but throw in a corner, a camber, a root, rocks, anything 'real life' and it's a different matter entirely, and that's where other aspects of flex and stiffness really start to come into play.

None of this is specific to a particualr material by the way, but the application of the material and how it's all strung together.

Is the Starling CEN-tested?
Wouldn't surprise me at all if avoiding CEN produced a better steel bike.

Edit: Good discussion at the time here:
http://singletrackworld.com/forum/topic/cen-safety-regulations-and-the-demise-of-the-steel-hardtail

It's also wrong to think that because tyres are big and squishy that they absorb forces to the point of them not making it through the the frame

I think there's only one person trying to argue this, and he'll probably claim that he wasn't.

In all the chat about vertical/lateral flex & compliance, nobody's mentioned the materials' different damping abilities have they? That's a big advantage for carbon or steel vs aluminium IMO. Less unwanted feedback = less distraction = possibly riding faster.

chakaping - Member

In all the chat about ... nobody's mentioned the materials' different damping abilities have they?

there might be a good reason for that.

kayak23 - Member

I think it's the slight self-steer on a fatbike Northwind. I had it with the wrists on my Wazoo, then less so on the Dune. Did you not change tyres near the time too?

Nah, tbh it was so night and day it could only be the bar- I was getting hammered going down a single descent, swapped bar, next ride soloed the glentress seven without so much as a twinge.

I added a bottle cage at th same time so it could be that 😉 But no other changes.

I added a bottle cage at th same time so it could be that

Aha! it was definitely that, you altered the resonant frequency of the frame and stopped the vibrations, to be honest you could have done the same by sticky-taping 3 2pence coins under the BB shell and saved the cost of that bottle cage.

.. even 'vertical' input forces are not totally vertical in the dynamic system that is a bike and rider being ridden, leant and moved in the way it does.

FEA for an average steel MTB frame under a high forward load at the front axle (part of an ISO test) shows top and down tube centres deflecting 3mm or so and a head tube moving enough to give clear movement at the front axle. You can see it happening when a frame is tested. That's a large load to apply but we're quite capable of perceiving fairly small changes in how load or shock is felt, so although most of what we feel or describe as 'vertical compliance' is probably lateral twist and seat post flex, frames will vary in feel due to vertical flex.

[quote=chakaping ]

It's also wrong to think that because tyres are big and squishy that they absorb forces to the point of them not making it through the the frame

I presume this was aimed at me - go on then, where have I made such an assertion? Though I'm impressed at your attempt to disparage any clarification from me before I've even made it 🙄 Maybe you should try and understand better exactly what it is I'm saying.

The point is that the amount the tyres deflect compared to the amount the frame deflects is so large as to make the frame deflection essentially irrelevant. Of course that doesn't mean that forces don't make it through the tyres (and straight through the frame).

BTW you have to have deflection to get damping - it doesn't really matter how much material damping there is in an essentially rigid structure.

The point is that the amount the tyres deflect compared to the amount the frame deflects is so large as to make the frame deflection essentially irrelevant.

Damping .. frames deflect for sure but steel and ti make good springs so I'd assume damping is minimal to zero, carbon fibre has some damping properties apparently (or the resin does) but I have no idea whether it's really enough to help swing the decision on what material to use. It can't be that much otherwise we wouldn't have 'Zertz' inserts .. !

Jonesy's test of the Starling Murmur was against some top level bikes, Trek Slash, YT Jeffsy, Cotic 29er and others.

I think overall he just loved the ride feel and the times were consistently quicker.

Is steel the right material for bikes, maybe. Luckily (for bike manufacturers) the problem is so complex and difficult to get definitve answers for, that it will fuel interest and debate for years to come.

The motorbike track test with 3 different stiffness swingarms(mentioned in an earlier post) is a good example. Laps are timed to small margins and riders can consistently put those times in. The variation between tracks are not massive. This allows some difference between swingarm effect to be quantified.

To try to replicate this test with offroad bicycle with so many other variables is nearly impossible. Hence opinion and debate rule.

Personally I belive my Starlings are great because they have a solid silent ride character and are simple to ride. Riding a bike down a technical tracks is quite a brain intensive activity (in my case anyway). A rider that can concentrate and relax will be a quick rider. If your distracted by noise and quirky riding characteristics, your gonna be rubbish!

The difference in the ride feel the first time I had a go on the Ti was astounding- I'd been a sceptic until that point. It there's nice little trail int eh woods nearby that rewards being able to hold a line across roots on an off camber section- at the time I couldn't keep up with him down there, swapped bikes and suddenly it reversed. The bike somehow hugged the trail and hovered over it- I actually checked he wasn't running the tyres insanely soft but they were a good 5psi harder than mine.

Anyway- frame stiffness, in my experience, can make a difference. Not sure if you can say for better or worse without a specific case in mind.

I had a Mk I Ti Switchback which was a fabulous bike to ride - it reminded me of a really old school steel frame. It was awesome but was stolen.

I replaced it with a second gen version which is also brilliant but has lost some of the magic feel of the previous one. It's a lot stiffer because the of fancy chainstay yoke and the tubes being thicker to cope with the internal routing. I really, really like it but don't love it like I did the previous one.

I think overall he just loved the ride feel and the times were consistently quicker.

The point is that the amount the tyres deflect compared to the amount the frame deflects is so large as to make the frame deflection essentially irrelevant.

I disagree.

Tyres have a big impact, but they do not render the flex in a frame irrelevant.

I've back-to-backed enough bikes down familiar trails, often with the same wheels/tyres to feel the differences in flex characteristics of the frames (not material, the frame), often more than jsut feel, you cna visibly see the flex in some circumstances, if the tyres where acting as you say then this would not be the case.

I've got two Cotics which are a great example of this, built with identical components, the same geometry, and essentially the exact same back end, the only differences being the diameter of the seattube that the back ends join to, and the tubeset on the front end of one of them being much lighter, they ride very very differently, one is a lot flexier, and a lot more comfy and less fatiguing, and it's very much down to the frame and not overshadowed by tyre deflection.

Break it down to it's most basic => force acts on tyre, some* of that force is transmitted through the system of tyre/wheel/axle/fork etc. and then on to frame, of which there is no dispute**, it happens. Regardless of how big or soft your hypothetical tyre is, there is a remaining force that gets to the frame.

If you keep the force and the wheels/tyre combo constant in this scenario you still have force 'X' getting to the frame, then how the frame/system responds to that force [b]IS[/b] relevant***.

The tyres can and do play a massive part in how much force is trasmitted, and to a big degree in what direction it acts, but they do not have such an impact as to render frame flex irrelevant in either handling, feel or comfort.

All of this discussion is also skipping over the fact that input forces come from the rider as well as the terrain. Flex in a frame or bicycle system isn't just important when considering inputs from below, its important when considering inputs from above, and how the frame reacts to your pulling, pushing, twisting and thumping great muscley body acting upon it, a bit of give and or flex between contact points can make a big difference in how your body fatigues when working hard, and sometimes it can be worth sacrificing a bit of efficiency in power transmission for a bit of comfort and feel, especially if you prefer it.

*how much, and in what direction is complicated and dependant on the dynamics of the situation.

** there is not really some magic value below which the tyres absorb it all and nothing gets further through the system, there is always transmission, and under normal circumstances it is significant.

*** I know we are discussing MTB here but this is so much more relevant on the road where it's a lot easier to swap wheels between bikes and feel the difference in handling comfort and 'feel' between very stiff frames and flexier ones while keeping other variables constant.

I disagree.

Tyres have a big impact, but they do not render the flex in a frame irrelevant.

I've back-to-backed enough bikes down familiar trails, often with the same wheels/tyres to feel the differences in flex characteristics of the frames (not material, the frame), often more than jsut feel, you cna visibly see the flex in some circumstances, if the tyres where acting as you say then this would not be the case.

Break it down to it's most basic => force acts on tyre, some* of that force is transmitted through the system of tyre/wheel/axle/fork etc. and then on to frame, of which there is no dispute**, it happens. Regardless of how big or soft your hypothetical tyre is, there is a remaining force that gets to the frame.

If you keep the force and the wheels/tyre combo constant in this scenario you still have force 'X' getting to the frame, then how the frame/system responds to that force IS relevant.

The tyres can and do play a massive part in how much force, and to a big degree in what direction it acts, but they do not have such an impact as to render frame flex irrelevant in either handling, feel or comfort.

All of this discussion is also skipping over the fact that input forces come from the rider as well as the terrain. Flex in a frame or bicycle system isn't just important when considering inputs from below, its important when considering inputs from above, and how the frame reacts to your pulling, pushing, twisting and thumping great muscley body acting upon it, a bit of give and or flex between contact points can make a big difference in how your body fatigues when working hard, and sometimes it can be worth sacrificing a bit of efficiency in power transmission for a bit of comfort and feel.

*how much, and in what direction is complicated and dependant on the dynamics of the situation.

** there is not really some magic value below which the tyres absorb it all and nothing gets further through the system, there is always transmission, and under normal circumstances it is significant.

POSTED 1 MINUTE AGO # REPORT-POST

Heres an eye opener for you someone who is fast on a bike is ****ing fast on a bike...end of

Must admit, I really love the look of the Starling.

In regards to KTMs steel trellis frames, I heard they stuck with these at its easier and cheaper for non factory race teams and KTM (who dont have R&D budget of Japanese teams) to get the flex right.

You can either reweld or weld up a steel trellis frame with slightly different tubing, alu frames require new casts etc.

tldr; but this thread is making me want to replace my trek budget alu 26" ht for commuting with a 26" cotic bfe and still use it for commuting. Can't imagine commuting on any bike that I couldn't just have a bit of fun chucking around when the impulse strikes (ie most days). I want a cotic bfe. I want a cotic bfe. I want a cotic bfe. I want a cotic bfe. I want a cotic bfe. I want a cotic bfe. I want a cotic bfe. Just try talking me out of it.

Just one question, will I be allowed a 48-36-26 triple on the front of it?

Heres an eye opener for you someone who is fast on a bike is **** fast on a bike...end of

eh? has anyone said different? I was disagreeing with the assertion that tyre deflection is so great as to render frame flex irrelevant the the way a bike handles and feels.

but yes, fast people gonna be fast, no disagreement there.

[quote=amedias ]you cna visibly see the flex in some circumstances, if the tyres where acting as you say then this would not be the case.

Well you sure as heck aren't going to see vertical frame flex, so you must be talking about some other sort of flex!

As I've made clear all along, there are significant differences in lateral flex and twist between different frames (though frame material can't be used to define what and how much on its own, it's more down to design). Which makes a significant difference to how frames feel, and even if none of that is down to differences in absorption of bumps it's easy for the subconscious brain to assume it is.

Of course the tyres don't absorb all the force and some (most?) gets through to the frame, I don't think that has ever been in dispute (it does sometimes seem in such discussions that people want to argue with points which aren't being made*). It's simply that the ratio of deflection in a vertical direction between the tyres and the frame is >20:1, probably >50:1 at which point the deflection in the frame is essentially irrelevant to the total deflection.

*edit:

[quote=amedias ] I was disagreeing with the assertion that tyre deflection is so great as to render frame flex irrelevant the the way a bike handles and feels.

Now you see I don't think anybody has ever made that assertion

Taking this from my link earlier, the deflection in either direction is almost identical. Accepting this, placing in the real world with forces coming from above, below and (HT) from the front as the forks get knocked back before riding over obstacles, its quite clear to me that being able to adjust material dia, thickness and 'shape' i.e. butted tubes etc. will make a difference to handling. Its the same as laying carbon up in different ways in different areas. Re. steel, the clever bit is having the correct tube for the job in the correct geometry and its that that makes the frame come alive I think.

Torsional Stiffness of the Rear Triangle: This test applied pressure to the frame’s rear triangle side-to-side and measured how far the frame deflected in inches (moved) under a set pressure. The lower the number, the stiffer the bike is side to side, the less flex it will have, and the more direct the rider’s power will be transmitted to the drive train.

• Cannondale CAAD 3 Oversized Aluminum: .038”
• Softride Rocket R1 Aluminum: .039”
• Serotta Legend Ti OS: Oversized Butted Titanium down tube and chain stays: .045”
• Marinoni Lugged Butted Reynolds Chromoly: .045”
• Trek OCLV 110 Carbon: .052”
• Klein Quantum Pro Oversized Aluminum: .054”
• Seven Axiom Butted Titanium: .057”
• Kestrel KM40 Carbon: .060”
• Generic Welded Butted Chromoly Frame: .066”
• Litespeed Tuscany Production Titanium Frame: .074”

Vertical Frame Compliance: This test was conducted in a similar fashion to the torsional stiffness test, but it measured vertical deflection in inches. The numbers directly relate to a frame’s comfort and ability to absorb vibration. In this case, the higher the number, the more flexible, compliant and comfortable a frame’s rear triangle will be up and down.

• Softride Rocket R1 Aluminum: 1.4”
• Litespeed Tuscany Production Titanium Frame: .064”
• Generic Butted Chromoly Frame: .061”
• Kestrel KM40 Carbon: .060”
• Seven Axiom Butted Titanium: .057”
• Serotta Legend Ti OS – Oversized Butted Titanium down tube and chain stays: .054”
• Marinoni Lugged Butted Reynolds Chromoly: .052”
• Trek OCLV 110 Carbon: .052”
• Klein Quantum Pro Oversized Aluminum: .052”
• Cannondale CAAD 3 Oversized Aluminum: .049”

As I've made clear all along .... + it does sometimes seem in such discussions that people want to argue with points which aren't being made

I think this is another one of those times were both sides are not explaining themselves as well as they think they are. 😀

And the more we discuss the more that becomes clear, as I'm not talking about vertical flex either, in all my posts I've been referring to flex in general, mostly lateral*, and how that impacts on what traditionally some people have attributed to vertical compliance when in fact it isn't.

* refer back to my point about bikes rarely actually being vertical, so are we talking about 'actual vertical' forces on a leant over bike (therefore having a component acting laterally on the frame), or vertical as in 'forces in plane with the seat tube'

damn the internet, it's a hard place to have a chat sometimes!

Apology accepted 😉 - I did read back through my posts, and can see how it could have been interpreted that I thought there was no lateral flex, so I understand how we end up having arguments despite agreeing!

I'm trying to avoid getting into discussing what happens when a bike is leaned over for cornering as it all gets far too complicated, but will point out that the load is still pretty much straight down through the centre line of the bike as otherwise you'd fall off, and any effect of a bump will act in this direction. In any case we do mostly hit bumps when the bike is upright.

@buckster - there is no suggestion in that test that the loads for both parts were identical - and I'd be extremely surprised if they were, as a bike frame is clearly far stiffer in the vertical direction due to triangulation.

In any case we do mostly hit bumps when the bike is upright.

No we don't.

What happens when the bike is leaned over for cornering is the main point of this discussion. And the torsional flex in that case is from the huge forces applied through the forks to the head tube, the bars to the head tube, the cranks to the bottom bracket and the rear wheel to the rear triangle/suspension.

Like in this review: https://dirtmountainbike.com/bike-reviews/downhill-bikes/devinci-wilson-carbon-vs-aluminium.html

I'm trying to avoid getting into discussing what happens when a bike is leaned over for cornering as it all gets far too complicated, but will point out that the load is still pretty much straight down through the centre line of [i]the bike [/i] the system* as otherwise you'd fall off, and any effect of a bump will act in this direction. In any case we do mostly hit bumps when the bike is upright.

indeed yes it's complicated, hence us lot wittering on! But it gets even more complicated when you consider that even when 'upright' there is a significant component of the force that is no in plane vertically as it's very rare that the bike is actually upright**, there's always dynamic change and leans going on.

On top of that, it gets even more complicate when you remember that the bike is moving [i]forwards [/i]so that even at moderate speeds the majority fo the force is in a fore/aft direction, even the biggest bumps will input more energy in that direction than up down (discounting landings!), so if lateral flex, twist, deflection of any part, be that tyres, frame or otherwise allows for part of the system to absorb that by moving sideways to mitigate that force it has just as big an impact on what gets through to the rider as anything in the up/down plane, it also massively impacts on grip/traction, especially in marginal situations.

I guess it's just trying to dispel this idea (mostly from poor articles and soundbite marketing) that comfort comes only from vertical compliance and that extreme lateral stiffness is key to handling, as ever it is lot more complicated than that in the real world!

* + ** the system being you and the bike, the bike doesn't have to be upright, and rarely acutally is, the load may be down through the centre of the system, but that's not necessarily in plane with the seat tube of the frame.

[quote=chiefgrooveguru ]No we don't.

So how much of a typical trail is straight, and how much is corner?

Though as I wrote before, most of the forces are in the up/down plane anyway, as otherwise you'd fall off.

So how much of a typical trail is straight, and how much is corner?

define typical 😉

I think the point is that even straights aren't straight, nor necessarily upright, I know on my local trails the vast majority is 'a bit bendy' rather than 'a corner', and also has cambers, banks, etc. that mean even when riding them in a [i]straight [/i]line while [i]upright [/i] that there's enough variation to mean your bike* is actually doing neither for most of the time, and significantly enough for the non-vertical components to matter a lot.

So how much of a typical trail is straight, and how much is corner?

I hardly spend any of my descending time going in straight lines with the bike upright. If there is a straight bit on my local trails it invariably has a jump or drop or chute/bombhole or is off-camber.

Although the net forces on a bike have to balance to stop it falling over, it's standard cornering technique to weight your outside foot and inside hand and shift your centre of mass outwards relative to the centre line of the bike. Those forces alone will cause frame torsion, regardles of the forces coming through the tyres.

@buckster - there is no suggestion in that test that the loads for both parts were identical - and I'd be extremely surprised if they were, as a bike frame is clearly far stiffer in the vertical direction due to triangulation.

If you look at this test, different source, same test, substantially similar outcome, it was 47.5lbs I think in both front and read rear 'triangles. The vertical was not tested, I assume as it wouldn't move as much as we would imagine! Thus suggesting that vertical flex only comes in during periods the frame is canted over? Reading through this thread, thinking logically and reading these tests does suggest vertical compliance to be non existent. But, on an MTB, the bike is rarely being ridden bolt upright on pan flat territory.

Looking at that 'fact' alone would suggest that how carbon, alu and steel are affected by pedalling, suspension bumps and frame deflection whilst leant over or swinging from side to side (honking down or uphill) would en masse affect the riders enjoyment and comfort
http://www.sheldonbrown.com/rinard/rinard_frametest.html

[quote=buckster ]If you look at this test, different source, same test, substantially similar outcome, it was 47.5lbs I think in both front and read rear 'triangles. The vertical was not tested, I assume as it wouldn't move as much as we would imagine!

If you read the commentary from Damon Rinard he says "I ignored any vertical loads on the frame, as I believe a traditional diamond frame resists such loads easily due to its truss design in the vertical plane." and he also links [url= https://groups.google.com/forum/#!msg/rec.bicycles.tech/RnALuXhtA2A/9-wg8nFhaM0J ]this interesting piece[/url] from the old rec.bicycles.tech usenet discussion group (it's well worth reading the whole post). I certainly remember discussing all this stuff on there many, many years ago and there's no surprise that I'm saying much the same thing as Rinard and Bob Bundy.

Sure the loads there are the same for both parts of the test - both lateral deflection tests. However the other test you linked does have lateral and vertical deflection parts with similar deflection for both parts, which implies very different loads must have been used.

[quote=chiefgrooveguru ]I hardly spend any of my descending time going in straight lines with the bike upright. If there is a straight bit on my local trails it invariably has a jump or drop or chute/bombhole or is off-camber.

So maybe you should have written "no I don't" - though I'm intrigued as whilst I don't really ride downhill, thinking about all of the trails I've ridden, which includes lots of trail centres as well as natural, I can't think of a single trail where the majority isn't straight or close enough to straight that you're not leaning off the side and the bike is very close to upright. I'm sure that the vast majority of the totality of riding is with the bike close to upright.

Thing is when a bike is lent over then the wheels will deflect, so will determine what you feel. Plus I'd be surprised if many people are sitting down when cornering so any 'comfort' of the frame becomes a moot point.

Am I the only person who thinks comfort on a bike outside of key contact points is a bit of a stupid concept anyway? If I wanted comfort I'd take a car or train. On a bike I want maximum efficiency and hence stiff, light bikes (with decent suspension if an mtb) win.

So maybe you should have written "no I don't" - though I'm intrigued as whilst I don't really ride downhill, thinking about all of the trails I've ridden, which includes lots of trail centres as well as natural, I can't think of a single trail where the majority isn't straight or close enough to straight that you're not leaning off the side and the bike is very close to upright. I'm sure that the vast majority of the totality of riding is with the bike close to upright.

If you ride a bit faster you'll find the straight bits turn out to be curves! 😉 Also, longer, slacker and bigger wheeled bikes have to be leant over more to turn than old school bikes.

I have to admit I'm curious where you're referring to because I seem to spend most of my time on the bike going around corners, wherever I go! My local trails are the woodlands of the South Downs but a few weeks ago I was in FoD, Cwmcarn (that does have more straight bits) and BPW.

I'd assumed this thread was about flex in full-sus bikes, following Dirt's Starling review. If that's the case then it's not about comfort, it's about control.

dragon - Member

Am I the only person who thinks comfort on a bike outside of key contact points is a bit of a stupid concept anyway?

no, plenty of other people are wrong too.

😉

FOD is fairly local to me, and I've ridden there a lot. I've no idea about the DH tracks, but Verderers and Freeminers certainly consist mostly of straight bits punctuated by corners - I reckon that even if you look only at the bermy bit at the end of Verderers that's more straight than corner. I'm wondering if this is another perception thing where the impression isn't the reality and a lot of corners leaves people with the impression that you're continuously cornering (strangely enough when I was trying to think of places which might be more continuously cornering I wondered about Cwmcarn, but then it's a long time since I've ridden there!)

Let me get this straight, we started off discussing if steel bikes are becoming more popular among the run of carbon based designs. And via Ducati frames have agreed compliance is non existent in the vertical plane and all mountain bike trails are straight?

Aracer, you said 'close to' upright so this is being a bit pedantic .. but based on how we ride a bike, all of our time riding is cornering to some extent. More so off-road as we're pushed further out of balance by uneven surfaces. So if we're continually generating varying levels of cornering force you could say how much lateral twist a frame has can be a significant part of how we perceive a bike's 'feel' or reaction to input, at a similar level to steering geometry.

Thank you JamesO!

In FoD we were riding the off-piste stuff and finished over at the DH with GBU. When I'm following my quicker mates they're usually swooping about even more than I am - compared to a slower rider corners start earlier and finish later and you're leant that far over that you just pass through vertical before immediately leaning the other way for the next corner.

I don't have any particular dog in this race - both my MTBs are alloy and pretty stiff. I have a cheap steel BMX - stiff. And a steel Brompton - bendy bendy bendy. But I'm an engineer and oversimplification annoys me. My old hardtail was more flexy in a good way - but the forks were more flexy in a bad way!

I have a hypothesis that with full-sus bikes you want stiffness around linkages, bearings and bushes so forks and rear suspension work as designed. You want some lateral give in rims. You want some torsional give in the front triangle between head tube, bottom bracket and rear pivots but not too much - that's the difficult area because you need to feel that when you push and pull the bike around it responds like you expect. But if the bike kicks back too harshly you'll lose some control. You want as much longitudinal stiffness as possible so forks don't judder under braking. Vertical flex is basically irrelevant on a 6" travel full-sus, so it matters not that it's usually triangulated down to negligible.

Down some of the rougher bits on the Cwmcarn DH and at BPW there are definitely moments where you are going in a straight line but the bike is suffering lateral forces from rocks on the ground.

An interesting observation from my part is that at BPW I was quicker on the straighter rougher trails and slower on the bendier smoother ones. My bike is slightly shorter travel than most of my mates' bikes (150F/140R vs 160/170F and 150-165R) but slacker (64 deg HA). But I'm pretty certain the difference was that I'm not bendy enough as individual (working on it!) but I am fairly strong, so I can hold the bike on course through the gnarr but not whip it around tight berms well enough.

I guess some manufacturers have slapped sensors all over a frame and measured the strain as it rattled down a trail. But they probably regard that as valuable and confidential information. It would be interesting data anyhow.

dragon - Member

Am I the only person who thinks comfort on a bike outside of key contact points is a bit of a stupid concept anyway?

TBH I do think it's weird that comfort seems to be such a big topic when talking about materials. I mean, apart from extremes like my wrist-destroying fatbike setup... My mmmbop was stiff/harsh as a mother****** but I never felt any difference in [i]comfort[/i] compared to my noodly doodly Soda. Handling, sure.

Now to be fair, I have a cast iron arse so ymmv but most bikes are pretty much equally comfortable in material terms, to me.

I found comfort on a HT was improved (when standing up too) by fitting some of On One's 'chewy' (flexy) carbon bars.
Much nicer on my wrists.

I do think it's weird that comfort seems to be such a big topic when talking about materials. I mean, apart from extremes like my wrist-destroying fatbike setup... My mmmbop was stiff/harsh as a mother****** but I never felt any difference in comfort compared to my noodly doodly Soda

dragon - Member
Am I the only person who thinks comfort on a bike outside of key contact points is a bit of a stupid concept anyway?

no, plenty of other people are wrong too.

it depends on how, where and how long your ride for though as much as anything.

As a road bike example, I run the same contact points on all my road bikes, they all have the same saddle, same bar tape (well OK one bike is different) and one of either two models of bar across 6 bikes, 3 of them even run the same tyres so theres enough consistency there to say the contact points are fairly constant, but theres enough variation in comfort between them that its noticeable, on anything between 100-150k its enough to make a difference and anything over 200k it makes a big difference to the point that I simply wouldn't use a couple of them*. One of them became noticeably more comfy after a stem swap to a flexier one, but I don't know if you consider the stem part of a key contact point on not, I certainly don't hold onto it while riding...

It's similar on MTB, I run the same saddle and grips on all of them, bars/stems/seatposts vary, on longer rides or on 12 and 24 hour races there's a lot more to comfort than just the bits you touch, but on the vast majority of short rides I can put up with anything for an hour or so and be 'comfortable' (as long as it doesn't grate my palms off or make my bottom bleed)

The thing is comfort isn't just about not initially being in pain as such, but fatigue as well, long term comfort comes not just from the interface with the bits you touch, but how battered, shaken and vibrated the rest of your body gets along the way, all my bikes are comfortable to sit on and ride, but not all of them are still comfortable hours and many miles later when muscles have fatigued and you are struggling to prop yourself up, all that micro trauma and action to the muscles mean it's about more than just sitting on the thing and not saying 'ouch'.

* great example there is one bike that I'm really prone to calf cramp on after about 100-130k, position wise it is set up to the mm the same as another bike that I'm quite happy on for 200 or more, same bars, same tape, same saddle, same pedals, same tyres, even the same cranks actually, it's simply the other differences that mean on one I get vibrated, battered and generally worn out on, the other I don't, it's not as good at getting power to the rear wheel mind and is noticeably slower on short rides, but on long ones it evens out to roughly the same speed as I can work hard for longer, and they're both steel BTW 😉

All this talk of frames and not much about forks.

Surely the long cantilevered bit of the bike is going to have more effect on feel than anything else?

An example is my early model Singular Swift. With the steel fork it was very comfortable, but when I put a carbon fork on - which turned out to be much stiffer - it felt like a completely different bike.

Yep it all makes a difference, I had 35mm Pikes on the front of my HT and swapped them out to 32mm Revs as they were too harsh....ditto the bars, swapped traditional stiff Alu ones out for flexy carbon ones...both changes made the front end much more compliant and comfortable to ride....let's not forget tyres, my current Swalbe setup of Magic Mary front and Nobby Nic rear (both apparently 2.3) feel and look like larger tyres, certainly bigger than Maxxis 2.3 and 2.5 tyres....then you've got seat posts, if your bike is an old school 27.3 size it will flex moor than the 30.9 and 31.6 versions giving the impression of comfort when sat down peddling....wheel flex, the new wide and presumably stiffer rims hitting the market are likely to be stiffer and less compliant than old model narrower rims...etc etc....frame material is just one factor, I've managed to make my big tubed and apparently stiff Alu Dartmoor Hornet more comfortable than any of my previous steel bikes using some of the changes listed above.

All this talk of frames and not much about forks.

Surely the long cantilevered bit of the bike is going to have more effec

Absolutely, although in my mind its part of the frame(set), as ever though the more you dig the further down the rabbit hole you go... 😉

Just moving from a 45mm offset to a 60mm offset version of the same fork on my audax bike made a noticeable difference in both handling and comfort over longer distances.