Swiss, on 14 January 2012 - 09:13 PM, said:

3 pounds is alot for a pro but 99.99% of bike sales are not to pros and of that 99%, 99% of those people will never notice a 3lb difference.

The problem with a dirt bike is that a frame is almost insigificant compared to the weights of everything else.  It might make up 10% of the overall weight of the bike, 5% once you throw a rider on top.  It's weight is carried centrally where it has little effect on handling.  Take a look at what a dirt bike frame really is.  The single backbone frame is pretty much an 18 inch long thin walled steel tube that ties the rear shock upper pivot to the head tube.  The rest of the frame is just there to attach things to.

Instead of paying an extra $1000 for a CF frame, why not spend and extra $500 for titanium springs front and rear that will both reduce the weight of the bike and reduce the weight of the suspension allowing it to be more effective.  How about titanium spokes, carbon fiber hubs, carbon swingarms, etc...  You know, you could probably produce a carbon swingarm inexpensively enough so that if it were to become damaged it would be a throw away item and you just buy a new one.

Edited by 1987CR250R, 15 January 2012 - 02:33 PM.

1987CR250R, on 15 January 2012 - 02:30 PM, said:

100% agree, I could care less about frame weight as they are already pretty light. give me the carbon wheels n hubs,saving unsprung weight is where its at. what is it they say, one pound of unsprung weight is equal to about 7-8 pounds of mass in feel. shed 2-3lb's off the wheels n shock springs n yur talking some major performance gains anyone could feel.

Titanium is lighter than steel but not as light as aluminum.  Carbon Fibre is much lighter than Aluminum but requires more engineering to make it strong in the right places to handle the forces required for a dirt bike .  Carbon fiber is more than up to the task.  the factory bilkes use it now for skid plates, gas tanks, fork guards, areas where sharp impacts with sharp objects are common.  On bicycles they use it for wheel rims now.  It could be used in engine cases as well. There are all kinds of applications.  The reason the big manufacturers don't use it is because they are still selling motorcycles that were engineered many years ago.  The basic technology has progressed at a snails pace for the last three decades.  They simply make lots more money by stamping out the same old stuff with minimal investment in R&D.  Just like Detroit has done with the auto industry.  There are things like interlocking boards of directors and conflicts of interest at play which result in agreements between manufacturers to not progress the technology in order to keep cost down and profits up.  Don't you think there would no longer be all these hugh japanese manufacturers in business if they were truly competing?  Kind of funny that they all stopped making 2 strokes at about the same time.  KTM has been a balancing factor and actually threatened to take over the market because they don't go along with the japanese Cartel.  But the reality is that there just isn't a big enough market right now to bring enough money to the sport to drastictly advance the technology.  Ossa is the one company doing some big things to really advance the technology with their new compact engine, placement of the fuel tank in the front, centrally located radiator with a fan, radical fuel injection, shock on the side, etc.  Now if they would throw a carbon fiber frame at it that would really be something!  http://twostrokemoto...ture-of-enduro/.  I'm still waiting for the bike with an engine that is basically a single cylinder from a formula 1 V8 with a CF frame, Single sided fork and swingarm, ceramic bearings throughout and weighs 180lbs.

Chromoly is probably a much better alternative to Ti, you could make it stronger and lighter than steel, plus its a hell of a lot cheaper than titanium. not sure how heavy it would be compared to aluminum though. and if they made hubs and wheels made of carbon that would definetly provide performance, probably make holeshots unfair. the bike would rev much faster.
come to think of it if they lightened up the rotating mass of the wheels and lighten up suspension, they would need less power to push it the same speed, so they could use smaller engines thus making it even lighter. ill probably never see that in a production bike in my lifetime but its definetly an idea i may pursue

Food for thought.http://www.pinkbike.com/v/243228

Edited by Wetbed0, 23 February 2012 - 06:22 PM.

rubbersdown, on 03 January 2012 - 09:04 PM, said:

He is right.
To get the maximum strenght out of your expensive ti frame you need to tig it in inert atmosphere.
Serious bike mfgs do it NASA does it.
Not doing it would be like..... Welding seamless 4130 frame with oxy acettaline. A waste of money.
I'm just going to weld a trophy truck togeather with my Lincoln 110 over here don't mind me jk.

Weld a ti exhaust pipe normal fine.
Weld a to frame for bmx downhill mtb or road race or mx not in a purge box well, count me out for test riding it.

Wetbed0, on 23 February 2012 - 06:21 PM, said:

That's quite impressive.
I did notice how the carbon fail would hurt more as it seperated and the aluminum deformed.
Now what i didn't expect..... The swing it like a bat at the concrete block wow! I stayed away from carbon down hill bikes for only the fear of chipping and compromising it on a rock!!  That's amazing.

On the screw it till it breaks test you can hear all the popping and crackling on the carbon frame I wonder how many times you could take it up to say 3/4 load untill it fails from fatigue.

The thing is that "carbon fiber" is a term that covers a broadening range of products, just as "plastic" does. There are so many factors that bear on the strength of the finished piece that simply identifying it as CF does not really supply you with a lot of information about what it will put up with.  Some of it is just so much junk, but some of it is really impressively strong.

grayracer513, on 24 February 2012 - 07:56 AM, said:

Ding ding we have a winner! Most of the "carbon fiber" you can currently buy in the MX world (skid plates, waterpump guards, etc) is crap. Same issue seems to exist in the sport bike and import car world. There are a handful of manufacturers making decent parts out there, but they seem to be drowned out in a sea of junk.

KJ790, on 24 February 2012 - 08:32 AM, said:

One of my favorite stories about my son's riding development over the years related to his YZ250F he had when he was 15.  It was equipped when we bought it with CF case guards on both sides, made by either CF Works or Lightspeed.  I don't know which because the PO couldn't remember, having bought some stuff from both companies.

Anyway, at one of our favorite ride spots, there's this rock that lives in a bush next to the trail, just waiting like a troll for you to get too close, and one day, he did.  The impact knocked him off the bike, but did no damage at all to the ignition case guard other than a barely visible scuff mark.  It did, however, break a fairly large chunk off of the rock.

Honduhminiman, on 01 February 2012 - 05:33 AM, said:

i dont understand when people say "cro molly is better then steel", it's just medium carbon steel with 1.25-2.25 % chromium and 1% molybdenum., it is stronger then some grades of steel, but per cubic foot is heavier then steel.

Steel is another one of those words that describes a broad range of things.  "Chrome-moly" is just one of dozens of steel alloys in 5 major groups.  "Steel" just tells you it's an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight.  There are easily over a hundred different steel alloys without counting any of the stainless alloys.  In fact, there are more than a couple variations of just Cr-Mo steels.

What about somthing like the BRITTON (his mumma didn't raise no fool) engine as a stressed member and carbon fiber fittings ?? . shielding the case seems like a pretty small hurdle to jump ?

i didnt say it was better than steel. i said its a better alternative to Ti because of the cost. i think it would be a bit lighter than your average mild steel you find in production bike frames.

whole front end broke off the britton while testing?   granted he fixed it, but at the time it was thought to be well designed

bad-mod, on 25 February 2012 - 04:07 AM, said:

highmarker, on 25 February 2012 - 07:21 AM, said:

Very true . It was a very sad day for him esp as it was not him of his life at stake in the crash.
No true sucess is not without it' s setbacks, As descussed previously one of the main faults amongst others was to do with the planning on the layup of the fiber. It also went on the one of the fastest mould breaking bikes ever "imo". And it was built by a Kiwi in his back yard

+1,  amazing achievement yet to be duplicated.  point being, rather test ride a steel frame than a composite any day, LOL.

My composite project was a 200 hp variEze built with a friend.  He ended up crashing it (survived), we cut it up with a chainsaw and hauled it to the dump. being composite nothing could be trusted, if it had a frame we may have salvaged some of it.

Edited by highmarker, 25 February 2012 - 08:18 AM.

Honduhminiman, on 25 February 2012 - 06:48 AM, said:

production bike steel frames are made of B3 (2.25% chrome) cro-moly anyway...

Ttoks, on 25 February 2012 - 05:56 PM, said:

True. At least for the steel YZ frames from '03 on.