A question of frame material and suspension

guy72277

Does frame material really make a difference to the feel of a ride if you're riding a full sus? (Hard tail and fixie I can understand) I'm guessing weight is an obvious factor (eg steel Vs carbon), but can all this talk about the stiffness of alu or flexibility of carbon be disregarded with a full sus set-up?

nicklouse

why would you disregard it? no frame wants certain flex, HTs sometimes want some vertical compliance but no frame want any horizontal flex.

guy72277

nicklouse wrote:

why would you disregard it? .

I would have thought you can disregard it because any flexibility or stiffness in the frame (and thus "feel") would be isolated from your feet, hands and arse by the suspension. But now that you mentioned "horizontal" flexibility, I'm questioning my original assumption.....

nicklouse wrote:

....horizontal flex....

Hadn't thought about horizontal flex being much of a factor in the feel. I'm guessing it comes into play mainly when you're pedaling hard uphill, but much less so in the flat or downhill sections. Amirite?

.blitz

My Rize has a burly, motorcycle-style swingarm with carbon seatstays the idea being that the swingarm is stiff enough on its own to take care of up-and-down suspension duties and the seatstays are there simply to actuate the shock.

In practice it is noticeably twangy in a side-to-side direction. Twangy enough to leave tyre marks on the seatstay and swingarm and instigate random brake rub. Sometimes it works to my advantage it has a way of winding itself up and firing out of berms for example but other times it is a proppa slushbox.

If it was my only bike I don't think I'd notice it but it isn't and I do.

guy72277

.blitz wrote:

My Rize has a burly, motorcycle-style swingarm with carbon seatstays. In practice it is noticeably twangy in a side-to-side direction.

Sounds pretty flexy, especially if you're getting tyre marks there! So I get that you really need horizontal stiffness in the rear triangle. Does carbon's flexibility in the main frame triange have any adverse effects to the feel of the ride too? I doubt there are any bikes with an Alu rear and Carbon Front, but what do I know?

.blitz

Carbon can be laid up to give it any amount of compliance/stiffness, it all depends on the application and the cost. Top-end carbon frames are allegedly what you'd expect from a piece of kit that has fine control over every aspect of its construction.

But the seatstays on my Rize are basically just pieces of what is probably bog-basic carbon tube to give it some showroom/spec sheet cred. If there were some aluminium replacements I would swap them out.

IIRC Yeti offer carbon or alu rear triangles for the 575. The aluminium one is by all accounts the better option for the sake of a few grammes.

guy72277

.blitz wrote:

Carbon can be laid up to give it any amount of compliance/stiffness, it all depends on the application and the cost. Top-end carbon frames are allegedly what you'd expect from a piece of kit that has fine control over every aspect of its construction.

But the seatstays on my Rize are basically just pieces of what is probably bog-basic carbon tube to give it some showroom/spec sheet cred. If there were some aluminium replacements I would swap them out.

IIRC Yeti offer carbon or alu rear triangles for the 575. The aluminium one is by all accounts the better option for the sake of a few grammes.

Good to know all this about carbon frames, thanks for the info.

.blitz

Some of it might be incorrect of course

NatoED

look up the salsa el kabong . it will show you how still having some vertical deflection can be helpful as it can push the rear wheel into the ground giving extra traction in climbs . just because you can't feel it doesn't mean it won't help .

kdawg74

My Kona has a scandium frame and after running bikes with both steel and aluminium frames i find it has a good mixture of the feeling you get from them, also had a carbon HT and that was a nice ride strong as hell but with just enough give to take away some trail buzz.

Anonymous

Just something to note, when people, particulrly engineery types talk about the "flexibility" of carbon, they're often not referring to how it flexes, they're insted talking about how it can be worked to suit a myriad of applications.
Just like someone who is flexible in their working hours - it doesn;t mean they do yoga between 9-5.

cooldad

kdawg74 wrote:

My Kona has a scandium frame and after running bikes with both steel and aluminium frames i find it has a good mixture of the feeling you get from them, also had a carbon HT and that was a nice ride strong as hell but with just enough give to take away some trail buzz.

Except scandium frames are really just aluminium with a tiny bit of scandium added which strengthens the welded areas basically. The frame is not made of scandium.

Anonymous

cooldad wrote:

kdawg74 wrote:

My Kona has a scandium frame and after running bikes with both steel and aluminium frames i find it has a good mixture of the feeling you get from them, also had a carbon HT and that was a nice ride strong as hell but with just enough give to take away some trail buzz.

Except scandium frames are really just aluminium with a tiny bit of scandium added which strengthens the welded areas basically. The frame is not made of scandium.

Same is true of lots ot titanium stuff too.

kdawg74

I did think it cant be completely scandium, tried to find some stuff on the mixture level but hard but i did find this which says alot abouts it strength.

scandium was used to reinforce the nosecones of submarine launched ballistic missiles so that they could be fired through the polar ice caps.

NatoED

That's why they are classed as alloys .
Carbon is very much like steel and Ti in it's dampening qualities . I rode a Aluminium framed road bike the other day and couldn't wait to get back on my carbon one .

Carbon really does smooth out the ride on or off road compared with Aluminium . It can cope very well with flexing too (look at the viper soft tail frames ) .

cooldad

From Wiki

The addition of scandium to aluminium limits the excessive grain growth that occurs in the heat-affected zone of welded aluminium components. This has two beneficial effects: the precipitated Al3Sc forms smaller crystals than are formed in other aluminium alloys and the volume of precipitate-free zones that normally exist at the grain boundaries of age-hardening aluminium alloys is reduced. Both of these effects increase the usefulness of the alloy.
The main application of scandium by weight is in aluminium-scandium alloys for minor aerospace industry components. These alloys contain between 0.1% and 0.5% of scandium.

Interestingly:
The production of metallic scandium is in the order of 10 kg per year.
The stable form of scandium is created in supernovas via the r-process.

So your bike has a little bit of supernova in it.

kdawg74

Ha cool one, now that is cool fact for the post ride pub stop.

Shaggy_Dog

A bit of lateral flex isn't a big problem, as another poster mentioned, you kind of load it into corners and it will 'pop' you out of the exit. Torsional flex is an issue though (that's the front and rear axles yawing in different directions) and is a big problem on my HiFi.

With regards to material, I've owned both the alloy and carbon version of the Gary Fisher HiFi and there is a noticeable lack of trail buzz in the carbon version. Suspension only works on medium to large sized bumps on the whole so a bit of high frequency damping in frame material takes away stuff that even low tyre pressure can't eliminate. This is of course very esoteric and not immediately noticeable.

toasty

NatoED wrote:

That's why they are classed as alloys .
Carbon is very much like steel and Ti in it's dampening qualities . I rode a Aluminium framed road bike the other day and couldn't wait to get back on my carbon one .

Carbon really does smooth out the ride on or off road compared with Aluminium . It can cope very well with flexing too (look at the viper soft tail frames ) .

Depends a lot on the bike, my old Stumpjumper HT was as stiff as anything, my Scandal feels quite soft. While the trend is obviously softer steel bikes, it's not always the way, something like the Cove Handjob is pretty stiff (no pun intended :shock: !).