Carbon v Aluminium

larmurf

hi
Am considering treating myself to a carbon framed bike for an advanced birthday.
I have never ridden one and live in a pretty remote area so little chance of trying one out.
So some advice would be appreciated on the following questions.

Is a carbon frame noticibly more comfortable on a rough road than aluminium?
Do the Zertz inserts on Specialized frames make much of a difference?
Would anyone like to give an opinion on Giant Scr Carbon compared to Specialized
Roubaix or Tarmac for trips of 50 - 100 miles averaging between 15/16 mph?

lm

redddraggon

larmurf wrote:

Is a carbon frame noticibly more comfortable on a rough road than aluminium?

No - it depends what on carbon frame you are comparing to what aluminium frame.

Carbon can be really stiff and unforgiving depending on how the fibres have been laid down - and the alu bike may be really comfortable.

People might say carbon is more comfortable but it isn't - if the fibres have been laid down for comfort though it probably will be.

Carbon fibre is not a wonder material.......

cougie

My Giant Carbon TCR is the plushest ride I've had - better than its Reymlds 853 and Carbon fork predecessor and way better than the Alu TCR.

Time trial bikes will be stiff - its maximum power output they want and you arent on them long.

aracer

It makes no difference to comfort anyway - at least not that any ordinary human can detect. The amount a standard frame deflects vertically is less than 1mm, whilst your tyres flex an order of magnitude more than that. If you want more comfort just get fatter tyres and don't put so much pressure in them.

mrushton

aracer wrote:

It makes no difference to comfort anyway - at least not that any ordinary human can detect. The amount a standard frame deflects vertically is less than 1mm, whilst your tyres flex an order of magnitude more than that. If you want more comfort just get fatter tyres and don't put so much pressure in them.

As the owner of steel,carbon,titanium,ti/carbon and aluminium bikes i can tell you that there IS a difference in the way those materials ride. my last choice for comfort would be aluminium.

redddraggon

mrushton wrote:

As the owner of steel,carbon,titanium,ti/carbon and aluminium bikes i can tell you that there IS a difference in the way those materials ride. my last choice for comfort would be aluminium.

Unless every frame you have is exactly the same (bar it's material) you can't tell what the difference is down to.

Frame design makes more of a difference than the frame material.

aracer

redddraggon wrote:

mrushton wrote:

As the owner of steel,carbon,titanium,ti/carbon and aluminium bikes i can tell you that there IS a difference in the way those materials ride. my last choice for comfort would be aluminium.

Unless every frame you have is exactly the same (bar it's material) you can't tell what the difference is down to.

...and you don't know which one you're riding so you don't know which one is supposed to be stiff and uncomfortable.

redddraggon wrote:

Frame design makes more of a difference than the frame material.

Frame geometry anyway.

In any case a frame can feel different (I'm not claiming that all frames feel the same) without being any more comfortable, since there are noticeable differences in lateral flex.

redddraggon

aracer wrote:

Frame geometry anyway.

What about tube diameters and shapes? Does that not make a difference?

aracer

In theory yes - the vertical frame deflection will vary with different tube diameters and shapes. In practice such differences are undetectable since even the flexiest double diamond frame has far less vertical deflection than tyres, saddle or seatpost.

Frame geometry however - particularly chainstay length - can make a noticeable difference.

cougie

So reddragon - are you saying that you can get an aluminium frame that rides as soft as a carbon frame ? I'm not sure you can ?

Clearly the way you build the frames up will make a big difference - but in most cases - Alu is a pretty harsh ride compared to a carbon frame built up similarly.

I swapped all my bits over from my 853 steel frame with cf forks to the TCR. The difference in ride was amazing - on steel - you feel every grid beneath your wheels. Ride it with carbon and it disappears - so aracer - you are wrong on that. It amazed me - I spent ages just riding through potholes to begin with !

The SCR is designed for sportive riding isnt it - so it should have an element of comfort - check out this review - it seems to back my theory up :

http://www.tredzblog.co.uk/2007/01/giant_scr_c1_bi.html

redddraggon

cougie wrote:

So reddragon - are you saying that you can get an aluminium frame that rides as soft as a carbon frame ? I'm not sure you can ?

Yes you can- but not all frames are equal. Carbon fibre can be made to do what you want through clever use of the fibres - it is more difficult to do the same with aluminium.

Basically the point I'm trying to make is that carbon fibre does not necessarily equal comfort, a lot of carbon "race" bikes will be very harsh some will be compliant - not all carbon frames are designed like the roubaix or synapse frames are.

aracer

So are you telling me cougie that when you ride through potholes you simply don't feel them at all with your carbon frame? Pretty neat trick for such a rigid structure which simply can't be flexing anything like the amount the tyres are, and certainly nowhere near the amount the potholes deflect your wheels (as I mentioned above, typical vertical frame deflection is less than 1mm, even for a multiple bodyweight shock loading).

At least try and turn your brain on - push down on your saddle with your bike standing upright and you not on it and see which parts between the saddle and the ground actually flex.

Anyway - I thought carbon frames were supposed to be stiff and harsh, whilst ti and steel were supposed to be flexy and comfortable :twisted:

cougie

aracer - try it for yourself. I have the carbon bike - are you just talking theory ?

the bike doesnt have to flex - why do you think it does ?

The vibrations that you normally get are much much less on my carbon frame than my steel or alu frame.

Same wheels, same gruppo, different frames - the steel frame - you really feel the buzz of the drains and grids. Try the same on the carbon and its much much less.

cougie

reddragon - I agree - CF doesnt equal comfort automatically - was it an Isaac I read a review of that said its great for stiffness and getting the power down - the downside is that you couldnt ride it for more than 10 miles without being crippled ?

But - it can be built into a very comfy bike - and i dont think you can get near that with alu. Or not on the frames I've seen anyway. Which is fine - not everyone wants that from a frame.

dennisn

I'm going to throw my lot in with the fatter tire, less pressure boys. You want comfort?
Outside of tires, most road bikes don't offer much no matter what the material. Now if you want you can try a suspension seatpost or possibly come up with a road suspension forks. They are made. Where and by whom :?: :?: Or you can pretty
much solve all you're comfort issues and go with a full suspension mtn. bike with
some big ass low pressure fat tires. Road bikes aren't lounge chairs. Never have been,
probably never will be

Dennis Noward

MichaelB2

I upgraded from a LeMond Tourmalet (all alloy & carbon fork) to an Argon 18 Platinum (all carbon).

The Argon is stiffer and just as "comfortable". They have the same tyres (Maxxis Detonator 28C) and the same sadlles, both have alloy bars.

The ARgon is a "sprinters' frame and has huge seat and rear stays.

So, as pointed out earlier, it depends on which alloy frame and which carbon frame you are comparing.

I never really had a problem with my LeMond - the Argon was a treat that came at the right price - ex-demo and 1/2 price

Buy something that fits you well, looks good and is in your budget.

aracer

cougie wrote:

the bike doesnt have to flex - why do you think it does ?

Um, because if it doesn't flex it transmits all the force straight from the dropouts to the seatpost - I don't understand how you think it could do otherwise.

cougie

aracer :

http://www.lemondbikes.com/bikes/road_racing/ac_dc/

Carbon fibre damping ?

Borrow a mates carbon TCR and have a go yourself if you dont believe me.

andrewgturnbull

HI Cougie.

I don't think anyone is doubting that your new frame feels comfier than your old one. What aracer and reddragon are trying to say is that this isn't necessarily down to frame material, but many other design factors.

Personally I've swapped this year from an old trek oclv to a ridley noah, again with the same components - both full carbon frames. The ridley, is very, very stiff and a lot harsher than the trek. Hopefully I'm faster on it though!

Cheers, Andy

aracer

So now you're trying to prove your point with bike company marketing? Not really very impressive given they could say pretty much whatever they liked there and it wouldn't make it true. It's pretty basic physics - if there's no flex there can't be any damping.

What I'm actually trying to say, Andy, is that any comfort is nothing at all to do with the frame (unless the geometry is different) - and that lateral flex (which you can feel the difference between different frames) is often mistaken for comfort (vertical flex).

giant_man

Carbon frames will vary in feel and handling, that's for sure. Don't think one carbon frame is the same as all carbon frames. They're really not. A recent test ride of two carbon frames confirmed this for me.

I don't buy the opinion that the frame material doesn't make for a better ride, I think it does. Imo any carbon frame (which i have been riding for the past five years) on the whole will always feel smoother and ride more forgivingly than an aluminium one. I have two bikes; one carbon and one alloy.

Yes of couse you still feel potholes and bumps, this goes without saying, but on the whole, it gives a more comfortable ride.

wildmoustache

giant mancp wrote:

Carbon frames will vary in feel and handling, that's for sure. Don't think one carbon frame is the same as all carbon frames. They're really not. A recent test ride of two carbon frames confirmed this for me.

I don't buy the opinion that the frame material doesn't make for a better ride, I think it does. Imo any carbon frame (which i have been riding for the past five years) on the whole will always feel smoother and ride more forgivingly than an aluminium one. I have two bikes; one carbon and one alloy.

Yes of couse you still feel potholes and bumps, this goes without saying, but on the whole, it gives a more comfortable ride.

Carbon can be formed into more or less any shape for a bicycle frame ... I suspect is this that allows a carbon frame to be stiff in the right places (BB etc.) and yet flex also in the right places to give comfort.

In any case my Look frame is significantly more comoftable than any alu bike I've ridden (yes ... same pressure tyres, wheels etc.), but also climbs better and feels no more flexy.

Carbon is a great material for making bikes because of this.

Alu is also great because it is cheap, light, and can take a few knocks.

larmurf

Hi

Thanks everybody for your contributions. I figure that I am going to have to try out
a carbon bike and make up my own mind. No one got around to expressing an
opinion on the Zertz inserts that Specialized include on their Roubaix and Tarmac
models.

The following is from a review in Cycling News of the 2005 Specialized S-Works
Tarmac

"Even though I came straight off a 3Al/2.5V titanium frame with relaxed Belgian geometry, the Tarmac's ride was more than noticeably smoother. This was an unexpected but welcome surprise, which belied the drainpipe-sized downtube and enormous bottom bracket shell. I did not experience any kind of discomfort related to the condition of the road surface, period. Indeed there were several moments early on when I had to stop and check my tyre pressure to reassure myself that I did not have a slow leak. No doubt the hourglass-shaped seat stays and total of five Zertz gel inserts are responsible for the amazing ride quality."

lm

wildmoustache

larmurf wrote:

Hi

Thanks everybody for your contributions. I figure that I am going to have to try out
a carbon bike and make up my own mind. No one got around to expressing an
opinion on the Zertz inserts that Specialized include on their Roubaix and Tarmac
models.

The following is from a review in Cycling News of the 2005 Specialized S-Works
Tarmac

"Even though I came straight off a 3Al/2.5V titanium frame with relaxed Belgian geometry, the Tarmac's ride was more than noticeably smoother. This was an unexpected but welcome surprise, which belied the drainpipe-sized downtube and enormous bottom bracket shell. I did not experience any kind of discomfort related to the condition of the road surface, period. Indeed there were several moments early on when I had to stop and check my tyre pressure to reassure myself that I did not have a slow leak. No doubt the hourglass-shaped seat stays and total of five Zertz gel inserts are responsible for the amazing ride quality."

lm

I dont like the look of the zertz at all and they get dirty and end up looking crap.

I had one in a seatpost once and took it out and didn't notice any difference without it ... bike was a bit lighter though

Tarmac SL2 has a better image than the Roubaix IMO which is a bit of an old man's bike (will get flamed for this!!)

cougie

aracer - have you ridden a carbon frame ?

aracer

Been riding one for over 10 years, and currently own 4 carbon bikes - and?

If you won't believe me, how about Sheldon?
http://www.sheldonbrown.com/frame-materials.html#ride

giant_man

aracer wrote:

Been riding one for over 10 years, and currently own 4 carbon bikes - and?

If you won't believe me, how about Sheldon?
http://www.sheldonbrown.com/frame-materials.html#ride

This is one person's take on the subject, and I don't totally agree with his findings. Some of this comments do make sense, though.

aracer

Well, me and him make 2. I'm sure I could find plenty more also - just thought we trusted and believed Sheldon round here.

The question though, is how and why exactly are we wrong?

cougie

Four carbon bikes and you say you cant detect any difference in comfort ? What are they ?

giant_man

It's all in the ride imo. I wonder how many carbon frames SB actually rode? As I have said before carbon does vary in feel from frame to frame anyway, christ you have four carbon bikes yourself, you must know this.

djaeggi

It's pretty basic physics - if there's no flex there can't be any damping.

What I'm actually trying to say, Andy, is that any comfort is nothing at all to do with the frame (unless the geometry is different) - and that lateral flex (which you can feel the difference between different frames) is often mistaken for comfort (vertical flex).

aracer,

Some of your points are partially valid, but your appeal to "basic physics" and subsequent argument is simply wrong! The physics is more subtle than that, and I speak as both an engineer and a rider of 13 years (currently riding both alu & carbon bikes).

The valid points:

1. Tyres - yes, these filter out a large amount of road vibration, and particularly affect the high amplitude shocks you get.

2. Frame vs material - true, vertical stiffness/comfort is a function of overall frame design rather than just the material.

However, your assertion that the "frame doesn't flex" is pure and simple wrong. A frame does flex! That's why, for example, two bikes with different geometry but same tubes can feel compeletely different (e.g. longer seat/chain stays are very effective shock absorbers) - that's Sheldon's argument exactly. You have to accept this, surely?

Just because frame flex is of the order millimeters doesn't mean that this is not significant. Ever sat in a room with, say, a washing machine running downstairs and felt the vibrations? How much is the floor/chair moving vertically? Much less than a millimeter!!!!

Further, when different materials flex they absorb energy, and they absorb energy in different amounts and across different parts of the frequency spectrum. Similarly, different tube geometries do different things. Don't believe me? Pick up a couple of different tubes. Ping them by flicking them with your finger. Notice two things. First, they sound different - this is down to their different frequency response. Second, the sound dies out after some seconds - this is energy absorbtion in action.

Let's get back to the bike. Take the wheels out of the equation, they effectively act as 2 chuffing great filters removing a fair chunk of the vibration. So, frame comfort is an issue of how axle loads are transmitted to sit bones. For a given geometry, change the material and the frequency response of your bum to given axle load inputs *will* vary. That's basic physics!!! That's why a bike with the same wheels different frame will and does feel different, because they flex and respond in different ways. And when I say frame, I mean geometry and material combined, there's no getting away from this.

But it's deeper than that. The point about frame materials is that it places different constraints on the detailed frame design. Why do alu frames use much thicker tubing than steel bikes? Because if they didn't, they'd fall apart! Why can some aluminium bikes end up quite stiff? Aluminium is actually more flexible than steel as a material, but it's because you're forced to use different tubes when you build an alu bike. In other words, you can't change the material without changing the detailed design. When people debate "materials" in frame design, it's a surrogate for debating "the design constraints in conjunction with the material property". What's interesting about carbon is that a lot of the traditional constraints regarding tubing thickness/profile have been removed so it's possible to build carbon frames with a whole range of characteristics.

Same thing with tennis rackets. Every played tennis? You can change the character of a racket quite considerably by fiddling with string material/tension, but the frame has quite a large impact on the feel of a racket. Two different frames of same nominal stiffness can play very very differently (one racket can feel dead, the other alive and responsive), and this is all down to the differing frequency responses and damping. It's subtle, but the human body is remarkably perceptive and can detect and respond to very small changes.

Same with bikes.

In short - frame subjective comfort is direct function of frame vertical stiffness and frequency response, which is a function of both geometry *and* material, and these two aren't independent.

In other words, every bike is different, you can't judge comfort just by looking at material.

Dan