cynic-al - MemberI don't buy it that ti is slower - W*nkstrong winning the Tour on one surely disproves this "theory"?
when did he win the tour on Ti ? (excluding the TT litespeed bike he was always on carbon, even before the Madone.)
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anc - Member
Lance won is 1999 tour TT'ing on a Trek branded Litespeed. Used to be quite common but much less so now, as the big bike brands put a lot of money into developing there TT and road bikes in wind tunnels etc.
Trek didnt have at TT bike and he will have done 3 stages max on that bike (if prologue, 2 if not).
Not sure you can attribute his win to a Ti bike given he was on carbon 95% of the time.
Oh aye fair enough I didn't read it proper.
He did win some TTs though? by more than 1%? 😉
given how much misplaced hype there is about ti frames. I mean even njee who should know better mentions "comfy" in relation to them (when the perception that makes people think "comfy" is actually just "flexy"). We've covered the bit about ti frames breaking sooner than carbon haven't we?
I did say that a 'comfy' ti frame is rather 'flexy' (in that you can't make it both as you can carbon) - I remember trying both an old Merlin Extralite and a Litespeed Ghisallo, when you stood to sprint it felt like the back would overtake the front. Horrible. Would never buy one!
Forks and rear stays are laid up specifically to flex more in the vertical plain that horizontal.
We're clearly back to bicycles breaking known laws of physics here. The stays might flex in isolation - built up into a rear triangle it just doesn't happen. Do the numbers.
leggyblonde - specific model, and which bits are flexing in which direction to achieve that?
aracer - Member
We're clearly back to bicycles breaking known laws of physics here. The stays might flex in isolation - built up into a rear triangle it just doesn't happen.
My carbon roadbike has straight chainstays but curved seat stays.
This is for one purpose and one purpose only: to allow the chainstays to flex on the vertical plain.
to allow the chainstays to flex on the vertical plain
Except they don't. Good for marketing though.
[i]My carbon roadbike has straight chainstays but curved seat stays.
This is for one purpose and one purpose only:[/i] to differentiate my frame from all the other carbon frames out there.
One more point to make and i am done.
Bike choice depends on type of rider. The traditional frame is stiffer than an aero frame.
You wont get climbers off of a standard frameset as they love the stiffer traditional frames. Aero frames are good for designed application but even in the pro peleton its hard to say what the real world savings are.
aracer, you're on to a loser here.
Cannondale Flash, Synapse, super X and others use the SAVE micro suspension system:
[url= http://www.cannondale.com/gbr/bikes/mountain/hardtail/flash ] flash [/url]
There are plenty of tests and reviews out there confirming that the system works.
We're clearly back to bicycles breaking known laws of physics here. The stays might flex in isolation - built up into a rear triangle it just doesn't happen. Do the numbers.
wrong again, triangulation doesn't totally eliminate flex. I could do the numbers given the correct material properties, it's part of my day job 🙂
There are plenty of tests and reviews out there confirming that the system works.
Linky with measurements rather than rider perception please. The link you gave just has a load of marketing stuff.
I could do the numbers given the correct material properties, it's part of my day job
Go on then - I'll allow the use of generic material properties off wikipedia.
Everyone move along now, there's nothing to see here. Aracer knows better than everyone. 🙄
[i]Everyone move along now, there's nothing to see here. I've run out of talent.[/i]
Fixed.
How can the frame flex? What is doing the transmission?
The tyre?
The inner tube?
The rim?
The spokes?
How is the pressure to flex an essentially rigid structure being transmitted?
...and why doesn't the paint crack?
[url= http://www.cannondale.com/gbr/bikes/road/performance-road/synapse ]Cannondale[/url]
Having in the past had an alloy Synapse I was very surprised how comfy it was.
Go on then - I'll allow the use of generic material properties off wikipedia.
hahahahaha! I'm not sure that you understand. The whole point of modifying composite layups is that the member properties aren't generic and homogeneous. Carbon members can be constructed so that E varies according to direction and can be specified quite precisely by the designer ie less stiff vertically in the case of SAVE. Manufacturers use this ability to do away with chainstay pivots on short travel XC frames.
I could create a rear stay arrangement analysis model using flattened oval sections of any material which would show that a rear end can indeed flex vertically more than it does horizontally. HOwever, as it wouldn't be exactly the same as an existing bike you wouldn't believe me I fear.
and as I'm on a silly mission...
...and why doesn't the paint crack?
it does, which is why early versions of the short travel XC frames mentioned above were un-painted and un-laquered.
could create a rear stay arrangement analysis model using flattened oval sections of any material which would show that a rear end can indeed flex vertically more than it does horizontally.
Just out of interest, and not taking sides, but how much more does it flex vertically? And is that detectable to the average bum sitting on a saddle?
You appear to be talking about short travel XC frames. the discussion is about flex in a rigid rear triangle.
Bring the goalposts back, please.
..and explain how in such a system, the chainstay is able to compress along its upper length and extend along its lower length, which it would have to do if there was flex in a vertical direction in the seatstays.
...and explain how this magical property is detected by the rider using that most perceptive of parts, the buttocks, already isolated by a seat, a seatpost, and the rest of the frame.
5 psi less in the rear tyre would appear to give far more suspension effect....
cannondale scalpel - no lower pivot 100mm of travel.
you cant tell me that yo get 100mm of lateral movement?
.and explain how in such a system, the chainstay is able to compress along its upper length and extend along its lower length, which it would have to do if there was flex in a vertical direction in the seatstays
there is vertical flex in the whole system, not just the chainstay. standard beam theory innit, seeing as people love wikipedia on here: [url] http://en.wikipedia.org/wiki/Euler-Bernoulli_beam_equation [/url]
...and explain how this magical property is detected by the rider using that most perceptive of parts, the buttocks, already isolated by a seat, a seatpost, and the rest of the frame
do an allday ride on a hardtail with a thomson seatpost and then repeat with a use alien carbon, you might be surprised at how sensitive buttocks are.
not with a 140psi 22c tub as used by pros5 psi less in the rear tyre would appear to give far more suspension effect....
Bigman, I'm not saying that if I rode a Venge I'd be keeping up with Cav, just that even tiny speed benefits can mean the difference between 1st and 2nd. Hence if everything else was equal (skinsuits etc) the rider with a Venge would be slightly faster than a guy on a litespeed.
Presuming you were racing continually into a headwind. You 'may' be using 37.675 watts keeping your sail-like aero frame steady in a side wind.
Easy to win the TdF without winning a stage. Well, in my 'mind' anyway....
cannondale scalpel - no lower pivot 100mm of travel.you cant tell me that yo get 100mm of lateral movement?
Well to be fair the Scalpel does have a shock and other pivots allowing the 100mm of vertical travel.....
[i]not with a 140psi 22c tub as used by pros[/i]
Most pros wouldn't use a pressure of 140 psi, just so you know...
[i]there is vertical flex in the whole system, not just the chainstay[/i]
So now the whole lot is flexing? ( goalposts on wheels...)
By how much?
The fixed points are the BB and the seatstay-toptube-seat-tube junction?
As for the difference between a carbon seatpost and a metal one; sure, easy to believe and observe, but we aren't talking about that are we?
Two mtb things from earlier in the thread...
IIRC - Chris Chance of Fat Chance fame, never wanted to build a Ti bike as he viewed it as too flexy and inferior to steel in bike frames
Actually his FAT City Cycles crew, went on to build a titanium mtb frame , mine (no.13) was made sometime in 1993. It rode loveley until it cracked, suspect he was trying to overcome the issues decribed above about being too flexy etc!
Bontrager too, had a titanium frame in their line-up in the first years of the partnership with Trek in the mid-late 90s. Used too ride one of these as well, got it autographed by KB at a race once (much to the amusement of my mates) wish I'd asked him more about back it then...especially as that too developed a cracked weld eventually. Quite interested in seeing if Enigma can do some repair work on 'em.
Repairability of Carbon versus Ti? not an issue for sponsored riders, but something I'd add into the equation of which is 'best' for an given application
Crikey, they will start a race on smooth roads with 140psi, over 7 hours the pressure of high end tubs will drop at least 20 psi. You can test this yourself if you don't believe me.
So now the whole lot is flexing? ( goalposts on wheels...)
I've always said that the whole thing flexes. For that system to flex, both elements have to flex. I've been arguing that carbon can flex significantly more in one direction than another. For the purposes of that argument whether I'm talking about singlestays, whole rear ends or sus frames is irrelevant and you know that. In jabbering about moving goal-posts you are doing just that.
By how much?
read my earlier posts, cannondale claim a few mm on their flash but I can't analyse that. I'm sure some german mags have or will test it.
As for the difference between a carbon seatpost and a metal one; sure, easy to believe and observe, but we aren't talking about that are we?
you claimed buttocks can't detect a small amount of movement, I've come up with an analogy that shows that they can. seat post flex must also be of the order of a few mm at most.
You've not explained how the force to cause this 'few mm' can be transmitted from the ground to the frame.
I think that the vertical flex in the rear triangle of rigid frames is massively overstated and is to all intents and purposes undetectable in the complex system that is tyre/tube/rim/spokes/hub/bearings.
It's even less detectable in a system that then assumes that you can detect it using your bum which is isolated by shorts/saddle/seatpost/frame.
You are suggesting it exists and is detectable; if you can show me how, I'd be glad to change my view.
(..and no, really you wouldn't use 140 psi. Maybe in a velodrome...)
I know guys who have raced at 180psi.
using that most perceptive of parts, the buttocks
😆
crikey - Member
I think that the vertical flex in the rear triangle of rigid frames is massively overstated and is to all intents and purposes undetectable in the complex system that is tyre/tube/rim/spokes/hub/bearings.It's even less detectable in a system that then assumes that you can detect it using your bum which is isolated by shorts/saddle/seatpost/frame.
If this is the case, why the hell would people use Ti? (apart from weight of course).
It's well documented, indeed it has been mentioned by the argumentative naysayers earlier in this thread that Ti makes for a nice, comfortable riding bike due to its inherent flexibility.
What I and Leggyblonde have been saying is that you can enjoy similar benefits with carbon, but you can also virtually eliminate sideways deflection at the bottom bracket, without the significant weight penalty that you would need to create the same effect with a Ti, aluminium or steel frame!
If you've ever ridden a good carbon roadbike, you'll understand that fantastic feeling of the wheels chattering over rough surfaces, but the bike absorbing the vibration and giving you a smooth ride.
We're not talking about 5" of rear travel, we're talking about 1 or 2mm - enough to soak up a lot of vibration.
cannondale claim a few mm on their flash but I can't analyse that. I'm sure some german mags have or will test it
earlier
There are plenty of tests and reviews out there confirming that the system works.
Backpedalling?
I could create a rear stay arrangement analysis model using flattened oval sections of any material which would show that a rear end can indeed flex vertically more than it does horizontally. HOwever, as it wouldn't be exactly the same as an existing bike you wouldn't believe me I fear.
It would be very helpful at advancing the argument, so why not if it's bread and butter for you? Better than just claiming it's all to do with anisotropic properties of carbon composite (all very well, but that doesn't get round basic structural issues).
which is why early versions of the short travel XC frames mentioned above were un-painted and un-laquered.
The fact the bikes we're discussing are painted would suggest that's an argument for mine and crikey's side 😉
The fact the bikes we're discussing are painted would suggest that's an argument for mine and crikey's side
Erm... Paints and lacquers can flex you know. 🙄
Otherwise, the paint would crack on the flexy 653 roadbike frame I have...
If this is the case, why the hell would people use Ti? (apart from weight of course).
Why the hell would people use curved seatstays (you do realise that's [url= http://www.classiclightweights.co.uk/bikes/v-hetchins.html ]not a new thing[/url])? Why the hell would people use fancy cut out lugs?
It's well documented, indeed it has been mentioned by the argumentative naysayers earlier in this thread that Ti makes for a nice, comfortable riding bike due to its inherent flexibility
It's well documented that people [b]think[/b] ti makes for a nice comfy bike. It's also well documented that you can measure the lateral flex on one. I'm happy to accept that people can tell the difference between a ti frame and something stiffer due to the latter fact, and convinced the former perception is also due to that. If you're talking about a standard straight tubed ti bike like plenty out there people commend for their comfy ride, the mathematical analysis is easy using standard mechanical equations (I've got an excel spreadsheet somewhere where I also did resonant frequency analysis) and shows the vertical flex in the frame is miniscule.
[i]Erm... Paints and lacquers can flex you know[/i]
I'm fully aware of this; the fork dropouts on my Scott Addict have paint cracks where the dropout is bonded into the fork. I'm happy that it is evidence of flex occurring between the two bits, and the paint/lacquer not being as flexible.
[i]we're talking about 1 or 2mm - enough to soak up a lot of vibration.[/i]
Ok, so now we're getting something approaching [i]how much[/i] flex.
Now explain how the force required to flex a rigid triangular structure can be;
a) Transmitted, given that in this particular system there is a big squishy tyre, some actually quite bendy spokes, and a rim held in place by said spokes. If we are not getting pinch punctures all the time, this would suggest that the force required to flex the frame is less than the tyre pressure? Even at 140 psi, this seems a tiny wee bit too little?
b) Isolated using only your bum (see above for the reasons why I think this unlikely) as the measuring device?
[i]the bike absorbing the vibration and giving you a smooth ride[/i]
I agree with some of this bit, but I don't agree with the rear triangle being any kind of vertically flexible structure, and definitively not in the context of that oft missed location, the real world.
Erm... Paints and lacquers can flex you know.
I really don't want to get dragged into this pointless argument, but...
If you look at alot of the lugged carbon frames, (which is most) you will see that the paint often does crack over time as the tubes move and the paint doesn't.
I did have a think and the last continental pro team i can think of to use Ti road stage frames was Z and they were also running TVT's as well. I know there have been teams such as Saturn that have used Ti more recently but they are second division teams.
Something else to throw in the mix is that the UCI has rules, and these rules do impact on what you can do when designing the frame.
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Sorry Crickey the phrase "force is transmitted" doesn't sound very clear
If the up force from the road didn't reach the riders but then surely they'd just end up as a heap in the road
when the rear wheel hits a bump the tyre will deflect, that reduces the force transmitted as it increases the time for the rider to gain the necessary upward velocity to get over the bump.Any extra flex from spokes frame or seat post will reduce the force as well
In the days of steel versus alloy on mountain bikes I was a vertical compliance skeptic. But on a road bike with thin high pressure tyres it seems plausible. Apparently beding of the top tube allows the rear traingle to rotate forwards slightly. Thats why some bikes have a highly ovalised top tube just in front of the seat post
Is that your Hetchins, mrmo? Nice!
standard beam theory innit
euler bernoulli double pwning there!
Read most of this thread,a lot of it is utter dross.
Carbon V Titanium. Carbon wins in every circumstance, comfort, longevetity, strength, stifness and speed.
I always wanted a titanium bike, bought a Litespeed Vortex about 4 years ago, the last model to be made, most expensive diamond style tubing,rode by Robbie McKewen (Sprinter)so it was a beast, not the flimsy Ghisallo model.
Worst purchase I ever made, it flexed like mad, so bad it changed gear by itself when you stood up giving it full gas. It looked the business and i still think its the best looking bike and most fabulously engineered thing I have ever owned. So dissapointed.
Bought a carbon Scott Addict (Ford Escort Bike) right after I got rid of the Litespeed and it was unbelivable, rode so much better, went round corners on rails, super stiff and comfy and miles faster on the flat and up hill. Also alot lighter.
I have had a few road bikes and MTB's to say the least and do about 10 hrs a week on the bike minimum, palmares is OK too 😉
Still got the Scott, titanium has had its day. Carbon is super strong and durable, not seen many carbon frames break in crashes in races on and off road.
Close thread. 😀
aracer, no, not my Hetchins, just making a point, there is a hell of alot of crap spouted about bikes. Look at the curly stays, look at the extended lugs. There are reasons, but to be honest mostly they look good.
Same for Ti bikes, they aren't the best they have alot of downsides, but they can look good, but if i was looking to replace my roadbike would i buy a Ti frame, no. Either stick with a steel frame or go Carbon. Ti is lost, expensive and not the best performing material.
And to all those that still think Ti must be best because Lance road a Litespeed in a timetrial well over a decade ago, I think he will have been more interested in the weight and geometry of the Blade rather than the handling characteristics of Titanium.
TT bikes rarely need to climb or sprint to the same extent as a day-to-day race bike, so ti's shortcomings won't have been such a problem.
I'm sure he enjoyed the comfy ride though... 😉
[img] 
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[url]
this video, 3.24 - watch that if you want to see a carbon frame flex vertically by design
Well found IanPV! I fear that Aracer still won't believe it - it's all just marketing hype, you understand... 😉
PS, what a dude Spartacus is!
I've got to completely agree with LeggyBlonde and kingkongsfinger. Carbon is a far superior material to build a bike with than Ti - if done properly.
I've had carbon road bikes since the early nineties. My first carbon road bike was a Alan carbon. Alu lugs and carbon tubes. It flexed like hell and got terrible speed whabbles. Horrible.
After a few carbon bikes in between I have carbon bike with O/S headset, beefy bottom bracket and it's a 900g frame. I have no worries about it busting - it may do - but I've seen plenty of Ti frames bust too. In fact in the last few years as carbon manufacture has got better you hear much less about breakages.
Ti frames IMHO are only good for smaller sizes. 56cm and above they are too flexy for racing. I have a friend who bought a Litespeed Vortex (supposed to be siff) in a 58cm frame. You could hold the saddle and move the stem laterally. Horrible.
Some carbon race frames are going below 700g and this means Pro's can ride with power meter cranks and stiff bars/stems and still be on the UCI wieght limit.
Carbon - best material for racing bikes.
And to all those that still think Ti must be best because Lance road a Litespeed in a timetrial well over a decade ago, I think he will have been more interested in the weight and geometry of the Blade rather than the handling characteristics of Titanium.
The reason was Trek didn't do TT bikes then and they wanted a US brand they/he new to work with.
My point about Lance and the Litespeed was about companies using frames/products other than their own, not that Ti was better faster or whatever... 😉
Firmly in the carbon is better camp here 😉
King Fabu !!
Beaten to it by ianpv after reading all the posts!!..... 👿
aracer - MemberWe're clearly back to bicycles breaking known laws of physics here. The stays might flex in isolation - built up into a rear triangle it just doesn't happen. Do the numbers.
Aracer, would you prefer tea or coffee to wash those words down? 😆
Is the rear triangle flexing in the video? The main triangle is. (Only had a very quick look, I'm at work, so maybe I need to look closer.)
It's fixed at the BB and the machine is flexing the front triangle/steerer tube. The seat tube in turn moves backwards causing the seat stays to flex.
I would imagine they have a similar way to demonstrate upward movement of the chain stays.
But triangles don't flex, do they... 🙄
This video should clear up any confusion... 😉
Not really relevant but whilst we are looking at frame destruction