Why are titanium frames so heavy?

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  • Why are titanium frames so heavy?
  • Nicknoxx
    Member

    If titanium is much stronger/lighter than steel/aluminium why doesn’t titanium feature in very light bikes any more than steel or aluminium frames?

    Premier Icon mboy
    Subscriber

    Flex

    Ti frame makers generally use more material than required for strength reasons alone, in order to stop the frame flexing too much. You could probably make a ti frame strong enough for most people’s riding that came in at well under 3lb, but it would be ridiculously flexy. Beef up wall thicknesses a touch here and there, add 1/2 to 3/4 of a lb to the overall frame weight, and the bike is even stronger, still lighter than the equivalent ally frame and way lighter than a steel, but it’s not ridiculously flexy either now! Look at the Cove Hummer for example, at over 4lb it’s a heavy ti frame, but it’s ridiculously strong, so much so that I’ve seen them abused in such a way that would kill just about any other frame out there instantly. Yet at 4lb its light enough to be built into a lightweight XC bike should you desire.

    I’ve ridden a few ti frames over the years, and never found one I liked particularly, except for the Cove Hummer, as all the others flexed too much. And at 4lb, I’d rather save a whole heap of money and buy something strong enough for my use, and buy steel!

    The stres’ and strain’s in a tube are a bit mor cmpicated than quoting that Ti has the tensile strength of steel and the density of Aly, would have you believe. Mainy because bikes tubes are generaly speeking taking compressive loads of one type or another.

    2 things to note then:
    tensile strength and compressive strength of a material are not related in the slightest. Take the example of stone, you cant make a rope out of it as itstensile stength is minimal, equaly you cant make a building out of kevlar.

    A tubes failiure in compression is not related to either its compressive or tensile strength. It is in fact determined by its stifness.
    F=(1/4)*E*(t/r)
    E= youngs modulous
    t= wall thickess
    r= radius
    That is unless your making it out of something that would fall apart at a lower load (cant think of anything)

    You can build a 3lb steel frame, but they’r lively to say the least

    Haggis
    Member

    Just been doing a wee scan through and found this topic. I like the bit where you say (mboy) you could probably make a Ti frame at under 3lbs but it would be ridiculously flexy. Ti is supposed to be flexy and have that zingy ride about it. Thats the appeal. Check out Lynskey, Seven, IF, Moots, Dekerf as they’ve been building bikes at under 3lbs for years and they do very well at selling their “ridiculously flexy” frames

    Premier Icon wee-al
    Subscriber

    I was in square wheels the other day. They had a shop logo’d Ti frame custom built by pipe dream. IT was less than the price of Hummer frame for the whole bike. Only rode it round the car park but god it felt nice. I’m gonna get it as a present to myself once i’m debt free!

    Premier Icon NZCol
    Subscriber

    I’ve owned a litespeed and now have a serrota. Now, the Litespeed, fair enough it was a unicoi which is a softtail but fook me was it whippy at the rear end – it was fun to ride but quite quite scary on occasion as the front and back wanted to go in different directions. I rode a YBB as well and it was the same. The Serrota while not a softtail has an incredibbly ‘soft’ feel to it while still be as stiff as you like in the BB area so it is stupidly fast to accelerate but still very comfortable. I’d not be keen on something as flexy as the unicoi ever again. My rpevious bikes include an Explosif (853) and an original handjob so i have a few things to compare them to.

    Premier Icon speaker2animals
    Subscriber

    I think one reason might be availability of tube sizes. Also how difficult Ti can be to work. Ally can be hydroformed and oversized relatively easy. A light Ti tube coulb be used if it’s diameter could be increased but this in’t easy/cheap to do.

    Premier Icon njee20
    Subscriber

    Merlin XLMs about 7 years ago were 2.83lbs for a 17.5″, that’s when they were 3/2.5, they probably got lighter when they went to 6/4. They weren’t that flexy either.

    If weight matters, buy carbon.

    GNARGNAR
    Member

    mboy

    Look at the Cove Hummer for example, at over 4lb it’s a heavy ti frame, but it’s ridiculously strong, so much so that I’ve seen them abused in such a way that would kill just about any other frame out there instantly.

    *Actual abuse may be subject to authors imagination and or sense of exaggeration.

    ** “Just about any other frame” may or may not include full suspension frames and over built hardtails.

    Premier Icon mboy
    Subscriber

    Just been doing a wee scan through and found this topic. I like the bit where you say (mboy) you could probably make a Ti frame at under 3lbs but it would be ridiculously flexy. Ti is supposed to be flexy and have that zingy ride about it. Thats the appeal. Check out Lynskey, Seven, IF, Moots, Dekerf as they’ve been building bikes at under 3lbs for years and they do very well at selling their “ridiculously flexy” frames

    Yes and no. Yes a ti frame is supposed to have a lively feel when compared to an ally frame, or even perhaps most steel, but you wouldn’t want to be too flexy as that’s disconcerting to ride.

    I’ve ridden a few ti frames, albeit only a couple of them for anything more than 5 minutes or so. The Airborne Lancaster that I owned for a few months though was 3.4lb (I actually weighed it!) and I certainly didn’t fear for it strength wise. But it was way too lively for me, seemed to just be a flexy mess underneath me! Some people like that, I didn’t. The Cove Hummer I rode for a day was on the other hand much better. That bit more material, and I suppose that more laidback and stable geometry to some extent, made it a much more enjoyable experience.

    The good/bad thing about mountain biking (depending whose point of view your looking at it from) is that pretty much everybody has different ideas about what bike is ideal for them. For me, despite only being about 11 1/2 stone and not particularly powerful, I still find lightweight ti frames too flexy and unnerving to ride (as NZCol says, disconcerting when back end wants to go in a different direction to the front!). The fact that some people love mega lively/springy ti frames, yet some like ridiculously stiff ally ones, or lightweight carbon fibre, or even steel, is testament to our differences in preference!

    Premier Icon mboy
    Subscriber

    *Actual abuse subject to authors imagination and or sense of exaggeration.

    * “Just about any other frame” may or may not include full suspension frames and over built hardtails.

    I’ve seen one (not ridden by me I might add!) dropped to flat from a skinny 15 foot in the air… Yes, fair enough there’s plenty of long travel full sus frames built for this kind of thing, or 7lb plus steel hardtails, but how many 4lb “XC frames” out there could also shrug off this kind of abuse?

    GNARGNAR, are you one of Smee/Glupton’s alternative personalitys? You have ALWAYS got something derogatory to say to pretty much anybody’s comments on this forum from what I’ve seen!

    GNARGNAR
    Member

    mboy –

    I’ve seen one (not ridden by me I might add!) dropped to flat from a skinny 15 foot in the air… Yes, fair enough there’s plenty of long travel full sus frames built for this kind of thing, or 7lb plus steel hardtails, but how many 4lb “XC frames” out there could also shrug off this kind of abuse?

    Well, not to be pedantic but had you just typed ” 4lb xc” earlier it would have made a lot more sense and been a lot less silly. I’d like to see pictures or video of this 15ft drop to flat if you have any. Hardly impossible but bloody stupid on any bike much less an xc hardtail.

    GNARGNAR, are you one of Smee/Glupton’s alternative personalitys? You have ALWAYS got something derogatory to say to pretty much anybody’s comments on this forum from what I’ve seen!

    You really do have a flair for the fantastic don’t you.

    Premier Icon mboy
    Subscriber

    Well, not to be pedantic but had you just typed ” 4lb xc” earlier it would have made a lot more sense and been a lot less silly. I’d like to see pictures or video of this 15ft drop to flat if you have any. Hardly impossible but bloody stupid on any bike much less an xc hardtail.

    True! That it would have done I’ll admit.

    Don’t have pictures or video myself I’m afraid. I’m sure if you ask Jedi of this forum nicely though, he might have some.

    Hardly impossible but bloody stupid? Depends who you are really. For me I’d consider a 5ft drop bloody stupid, but that’s me. I’ve seen people doing closer to 25ft drops on long travel DH/freeride bikes. Not my thing, but horses for courses and all.

    You really do have a flair for the fantastic don’t you.

    Sorry, I was trying to be ironic! Didn’t communicate well. You do however have a penchant for disagreeing with people for little or no reason.

    jedi
    Member

    i rode my hummer off loads of drops but nevr to flat from high up.that’ll be dumb

    Premier Icon NZCol
    Subscriber

    Also – i’ve found ti frames and loaded Bob trailers to be quite an exciting combo !

    GNARGNAR
    Member

    mboy

    Don’t have pictures or video myself I’m afraid. I’m sure if you ask Jedi of this forum nicely though, he might have some.

    Hardly impossible but bloody stupid? Depends who you are really. For me I’d consider a 5ft drop bloody stupid, but that’s me. I’ve seen people doing closer to 25ft drops on long travel DH/freeride bikes. Not my thing, but horses for courses and all.

    The stupidity I was referring to was dropping to flat. Which is pretty pointless.

    Anyway…… Jedi, do you have any pictures of this 15ft drop to flat on a hummer?

    shoefiti
    Member

    Litespeed Ghisello frame is horrible to ride if over 9 stone or can produce any kind of power.

    mike_check
    Member

    Titanium is 60% denser than Aluminium, but more than twice as strong

    note ‘denser’ = greater mass = ‘heavier’

    that’s a simplistic answer for you. more detail has been covered in terms of tensile strength, tubular/wall thickness issues etc etc…

    chopperT
    Member

    Some interesting numbers here: (sorry no linky)

    http://materials.open.ac.uk/bikeframes/bikeframe.htm

    PeterPoddy
    Member

    If titanium is much stronger/lighter than steel/aluminium

    IIRC, titanium (for a given tube size with the same wall thicknesses – i.e. volume) is not as light as aluminium, or as strong as steel, but had a better strength to weight ratio than either of them…..

    Haggis
    Member

    Woah this has grown! i was merely commenting on how mboy seemed to be giving off the impression that a sub 3lbs Ti frame would be ridiculously flexy and therefore inefficient. With the thread title being what it is i had to comment. Especially when someone like Mary McConneloug has ridden and won the US national Champs for 4years running on the same Seven Sola Gold.

    grumm
    Member

    GNARGNAR, are you one of Smee/Glupton’s alternative personalitys? You have ALWAYS got something derogatory to say to pretty much anybody’s comments on this forum from what I’ve seen!

    It’s true, virtually every post you make is about how no-one except you rides anything hardcore enough to ‘justify’ the bike they’ve got.

    It amused me how you made a thread about how everyone should ride hardtails, and then another thread talking about you buying a full suss.

    mudshark
    Member

    Not sure I really understand this…but 953 looks good!

    tubing comparison

    jedi
    Member

    gnargnar, read my fookin post!

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