Just a thought on the 2007 frame/handling


60 replies to this topic
  • bajamoto

Posted November 29, 2007 - 04:31 PM

#21

[quote name='grayracer513']Once again, you have listed a set of attributes that belong to the suspension components, not the frame.

Weight transfer entering corners is handled by the suspension. The forks may dive as much as 7-8" (from the top) during this maneuver. How much do you think the frame moves?

[QUOTE]

nope, your right. Frame is 100% ridged, no flex at all. :thumbsup:

read this...

http://www.bikeforum...hp/t-24598.html

and this.

http://www.sheldonbr...-materials.html

so you can understand the principles of frame design.

and if you think shock absorb 100% of everything then you have never even ridden a dirt bike... i know after a race i feel like i have been through a dryer.... so i know the frame is transfering energy...

further evidence that the suspension doesn't take all the energy...

http://www.obergspor...ubberMount.html rubber mounts on tripple clamps.

Car frames even have flex, much more actaully due to their design.

http://auto.howstuff...question432.htm but there are sway bars.

frames have flex in them. now i ask you to prove me wrong.

From TW MOTO:

Q: So it was all a matter of Rigidity?

A: Yes, We just couldn't get the fram to flex enough for my liking. WE could have, but it wouldn't have been AMA legal...

...At times it was very frustrating to me, and i just wanted to take a grinder to my head tube to remove some material...

...Yamaha told me i would be very happy with the 08 Bike, because that's what the major model change was...



Even more evidence that bikes have frame flex.

CLASSY CHASSIS

The biggest change KTM made for '05 is the frame tubes. Last year both the 125 and 250SX were so fast that the chassis couldn't keep up with the motors, making the bikes very scary to ride in certain situations. Much of this problem was the flex of the frame, so this year KTM ditched the old school round tubing they've been using since the beginning of time and replaced it with an oval chromoly-steel tubing. The new-generation frame has also been reinforced with countless gussets and welds, making it much tougher and less prone to flexing.

The lateral, tubular design is meant to help front and rear end stability, a big problem on the KTMs of the past. Because the shock is mounted on the side of the frame and not directly in the center of the chassis, the KTM previously had a tendency to swap sideways in the whoops or in very rough situations due to frame flex. (If you ever watched Langston in the whoops at an SX you know what we mean.) This new frame design was developed to combat that problem head-on.


  • Edge316

Posted November 29, 2007 - 09:28 PM

#22

I think this round goes to bajamoto.

  • Edge316

Posted November 29, 2007 - 09:30 PM

#23

grayracer,its o.k to be wrong once in awhile.

  • grayracer513

Posted November 29, 2007 - 10:43 PM

#24

nope, your right. Frame is 100% ridged, no flex at all. :busted:

read this...

I'm not sure what your point was in any of this.

It appears you have mistaken me to have said that car frames don't flex, when of course, they do. Or, at least, the ones you get to buy do. Race car frames are braced and triangulated heavily to reduce the flex. A lot of time and work is put into the suspension to get the camber and caster curves exactly right throughout the entire range of motion, and letting the frame flex destroys that work. But frame flex has nothing to do with anti-roll stabilizer bars. It is correct to say that they are used to counter body roll, but body roll is a product of two things; a high CG, and low spring rates. A discussion of race car suspension with competent builders of cars built for road and paved track racing will reveal that they prefer to use the lightest (weakest) possible anti-roll bars that they can because they interfere with the independent operation of the suspension by tying one front or rear wheel to the other. With the the relatively short travel and high spring rates used in road racing, the need for AR bars is less in any case. But such is not the case with off-road truck and car racing. Watch some film of the Trophy Trucks running fast corners in the Baja. You won't see an AR bar on any of them, exactly because they interfere with the suspension.

So that's one. I have no idea why you posted a link to a set of rubber insulated triple clamps, but if you drop a note to the manufacturer, they will explain to you the difficulty they had in effectively minimizing the transmitted vibration while simultaneously minimizing the flex at the bar ends, which hampers steering precision.

The other links are concerned with bicycles, and I have no idea why you included it, either, but as it happens, I have considerable experience in that field, along with a nationals medal. Bicycle frames flex. Some of them flex a lot, others very little. And here again, the flex has to be controlled to keep it from being a detriment. Touring bikes are generally more flexy because it allows the bike to absorb more road shock. Race bikes have to be stiffer, and the forms of racing that involve more sprinting or climbing need tobe the stiffest of them so that the flex doesn't end up absorbing the energy of the pedal stroke. As far as aluminum is concerned, some of the world's stiffest bikes are aluminum framed, but so are some of the most flexible ones, like the old Alan and Vitus frames. But touring, road racing, and BMX bikes are human powered, and have no suspension, and are not t all directly comparable to motorcycles at all.

And then, you post a comment explaining how stiffening the KTM chassis made it handle better.

I'm still waiting for an explanation of how frame flex helps a bike handle better. :thumbsup:

  • bajamoto

Posted November 29, 2007 - 11:07 PM

#25

And then, you post a comment explaining how stiffening the KTM chassis made it handle better.

I'm still waiting for an explanation of how frame flex helps a bike handle better. :thumbsup:



Well there you go guy...

i didn't have to explain anything. A source did...

You said that flex doesn't affect handling. And i posted 2 specific quotes from sources proving that flex affects handling.

1st was from a Grant Langston interview. In case you are un aware he won this summer.

his quote:

From TW MOTO:

Q: So it was all a matter of Rigidity?

A: Yes, We just couldn't get the fram to flex enough for my liking. WE could have, but it wouldn't have been AMA legal...

...At times it was very frustrating to me, and i just wanted to take a grinder to my head tube to remove some material...

...Yamaha told me i would be very happy with the 08 Bike, because that's what the major model change was...


then i posted another source talking about a frame having too much flex. Both examples show that flex was having an affect on handling. and in both examples changes were made to improve the handling of the bike.

Can't get any more cut or dry then that.

In Conclusion: Frames Flex! If they flex too much they swap out, if they are too stiff they don't turn. examples are 2004 KTM SX 250 too soft, swaps out. 2007 YZ 450F too stiff doesn't turn.

:busted: :busted: :ride: :lol:

God you are one dense MOFO! But i mean that i a nice way because 99.99% you are right. I think we might not even be talking about the same thing here??? Who knows. Probably would have to talk about this in person to make sure.

  • grayracer513

Posted November 29, 2007 - 11:16 PM

#26

Another thought on frame flex. If i planned to do a frame flex measurment that duplicated real life action I would mount the rear tire top and bottom and pull on the bottom of the front.

I have done this on more than one motorcycle. 3 of the frame projects I undertook at the shop I was working at involved complete new road racing frames for 2 Kawasaki triples and one of the first of their 1000cc 4's. The stock triples were absolutely evil in a fast turn with an uneven surface. They both felt like they were hinged in the middle.

To see why, we modified one of our frame jig plates to work like an auto body frame puller. The wheels were not prevented from moving in any direction, but the steering had to be braced to prevent it from falling to the lock under a load, since the bike was standing still. The frame was anchored upright at the top center, and the load was placed on it through as near the CG as we could estimate.

It was pretty incredible to straightedge the wheels and watch the rear change directions as the chassis was compressed under a load pulling 3 degrees off vertical (to simulate leaning inside at speed). The replacement frame I built worked much better than the original.

  • grayracer513

Posted November 29, 2007 - 11:21 PM

#27

You said that flex doesn't affect handling.

Please post any quote you can find in which I said that.

What I have said repeatedly is that frame flex in a motorcycle is inherently a bad thing.

  • bajamoto

Posted November 29, 2007 - 11:24 PM

#28

Please post any quote you can find in which I said that.

What I have said repeatedly is that frame flex in a motorcycle is inherently a bad thing.


okay, i agree with you on that 100% too much flex is bad.

but you have to agree that too stiff is also bad. Or at least to Grant Langston, who i gurantee is a much better rider then you or i.

and go back and read your response to the 1st post. the original poster said that the main difference between the 07 and 08 was frame flex. and that is exactly what Yamaha told Grant Langston. Reduced volume in the head tube area to increase flex...

just going by what i read.

  • grayracer513

Posted November 30, 2007 - 12:21 AM

#29

but you have to agree that too stiff is also bad.

That's precisely what I originally started out disagreeing with, in fact, and I continue to doubt it. On reflection (since I have no solid explanation of the phenomena by anyone to work with), I've moved slightly to the position that I'm willing to consider some benefit may exist to a small, carefully limited amount of longitudinal torsional flex, but I'm still dubious.

As to what Yamaha and Langston have said, first, Langston is a racer, and a good one, but first, he's a Yamaha employee, and is expected to back up what the company says. For another thing, while there are certainly a lot of good racers that are also very good mechanically, some of them are such bricks they have to be threatened with termination if they do anything but ride the bike, and have to have other guys on the team for the sole purpose of testing and evaluating the bikes. I don't know where Grant falls on that curve, so what he says has a limited amount of sway with me.

As to why Yamaha would say that, it's simple marketing, IMO. They're trying to make as big a deal as possible out of what is in fact a bunch of worthwhile and effective, but very subtle refinements, so that the whole thing seems like some kind of a major change to the common man. Most people hear "new steering geometry" and have no reaction to it at all, which is why Honda, who hs made some kind of geometry change in their flagship MX chassis nearly every year since 1991 that I can be fairly sure of, almost never brings it up.

  • 917 rider

Posted November 30, 2007 - 12:44 AM

#30

what about the first alm. framed honda every body knew they were too stiff, so frames in the next years were made to be less stiff or flex?idk my 08 handles great,grey is always right,this was just my thoughts as a read the posts but you have to agree with grey, if it was just flex why the other changes like the forks, imo its all the changes working togather and some marketing,by the way i spent some time on a 06 and thought it handled great,to many people think to much about these reports go jump on there bike and start thinking in the turn my bikes going to push, thats bs you just f-up that turn because you was thinking about it to much and not charging ahead with the only thought of how much i love this sport and trying to smoke everybody around you:ride:

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  • tw557

Posted November 30, 2007 - 05:16 AM

#31

I was just ready to respond but Gray sure hit every exact point I was thinking. I've also road raced for 7 years with frame straightening experience and 15 years 4 wheels racing an setup. All the car talk is just not relative and the bicycle stuff is light on suspension and the pedal torque.
Compared to the Honda aluminum frame change many years ago, suspension is quite incrediably better to cope with the hits instead of the frame now a days.

I just have trouble believing any marketing HYPE. Look how yamaha tried to market how great the motor is this year also.All new headpipe to match new muffler for better low to midrange performance I haven't heard one person agree to this yet.

Well the first company to produce a frame with too much flex with add on plates of gussets to add the desired flex will be the ultimate then. This is how gokart racing works.

In dirt rider I read how they added the 08 motor mounts onan 07 kx from an 08. Then Lewis mention how it feels lighter and more flickable in the air. Come ON!! He does also mention quicker turn in too though.

If Langston really needed more frame flex, Yamaha would have figured out a way to get that for him istead of waiting until the first bike roled off the production line. His bike is just not that much like your off the shelf 08 Yamaha.

  • Polar_Bus

Posted November 30, 2007 - 05:20 AM

#32

Can't we all just have a good cry, and go out in the garage and give our beloved '07 or '08 YZ's a much needed hug? They work so hard to let us have some fun, and all we do is split hairs, and rag the piss out of them.... :thumbsup:

  • bajamoto

Posted November 30, 2007 - 08:33 AM

#33

Oops, yup, forgot that a bunch of old fart bench racers on a message board know more then Yamaha.

Marketing or not, changes were made. There are race proven results that show this.

Not sure what more evidence you need.

In conclusion: changes were made to the head tube area of the frame from 07 to 08 that allow the bike preform better in turns. Yamaha's have always fallen short in the turning dept. now it seems they are working on this problem.

Hopefully Bubba' will be out again next year and Grant can make another go at it.

:thumbsup:

  • JohnnyOfast

Posted November 30, 2007 - 08:47 AM

#34

Haha,

I tried the same logic in another thread and got the same response you just pursued it harder.

http://www.thumperta...hlight=08 frame

From what I have read the rigidity of the frame DOES impact cornering characteristics, it is not just the geometry of the frame. In a logical context it makes sense to me.

  • bajamoto

Posted November 30, 2007 - 09:23 AM

#35

Haha,

I tried the same logic in another thread and got the same response you just pursued it harder.

http://www.thumperta...hlight=08 frame

From what I have read the rigidity of the frame DOES impact cornering characteristics, it is not just the geometry of the frame. In a logical context it makes sense to me.


nah, we are wrong... :thumbsup:

http://www.aluminum....&ContentID=7648

One of the great advantages to working with aluminum, Honda notes, is that designers can add or take away material to add strength or flexibility in specific areas. In the case of the CRF250R, the main spars of its frames are rectangular in cross-section, which permitted Honda engineers more design latitude than that available to round-tube-steel fabricators. That allowed Honda designers to vary the thickness of the top and bottom sections of the box, vis-à-vis the sidewalls, simply by specifying a change in the extrusion dies. This helped make the frame members resistant to up-and-down flex while still allowing side-to-side resilience—both in precise increments.

in case that wasn't enough...

The upgrades to the frame change its “flex characteristics” to create a chassis that feels softer on bump impact and improves cornering over previous designs, Honda says.

  • tw557

Posted November 30, 2007 - 09:48 AM

#36

I do believe alot of this could be very true in road racing even to the average rider. The forces on the frame and suspension are at least double if not triple with 3 times more HP. There you need to flick from full lean to opposite full lean instantly. You need to feel what the tires are doing but also keep the wheels in line as its being thrown around.
As an older fart I guess I have been around way to much marketing hype and gimicks. As a mech. engineer I trust my experiences pretty much. I just have trouble believing at our average rider speeds with flexible spoke wheels with soft sidewall dirt tires and plush suspensions, we would really be able to flex the frame enough to notice. I am intrigued enough to fabricate some thin motor brackets and such to not have the engine support the frame. This should let the frame flex a bit more then just a little head change. I'd just lick to see if it feels alot different. Then again I'm not sure at all what the problem is. Flat hard pack and the whole bike slides, rutted turns and the bike falls in and allows some mid rut correction. I don't have soft and loamy here in PA. Does the Honda actually just turn for me. I just really wish I had the chance to try one. Maybe not if I would then hate the YZ.

  • Edge316

Posted November 30, 2007 - 10:01 AM

#37

I don't understand why some of you people cant get this.Bajamoto has shown more than enough evidence to support that frame flex and how rigid a frame does affect how a motorcycle handles......

  • 917 rider

Posted November 30, 2007 - 10:18 AM

#38

Oops, yup, forgot that a bunch of old fart bench racers on a message board know more then Yamaha.

Marketing or not, changes were made. There are race proven results that show this.

Not sure what more evidence you need.

In conclusion: changes were made to the head tube area of the frame from 07 to 08 that allow the bike preform better in turns. Yamaha's have always fallen short in the turning dept. now it seems they are working on this problem.

Hopefully Bubba' will be out again next year and Grant can make another go at it.

:busted:

you arnt talking about yourself our you?:thumbsup: let me see grant langston first half of the year when bubba and ricky was racing he got 3rd,4 and 5th:naughty: on the 07 after ricky and bubba was not racing he got 1st ,2 and 3rd on the 08:thinking: .remember when ricky took a break came back half way through the year and smoked everyboby by a half lap how was that 08 turning then:confused: ,im sorry he must have switched back to the 07 for that race:busted: .i have a 08 and love it but it really dont fell that much differnt from a 06 its all in your head.bubba would smoke every body on the track with a 1998 yz 400 i wonder how that bike turns:thumbsup:

  • bajamoto

Posted November 30, 2007 - 10:35 AM

#39

you arnt talking about yourself our you?:thumbsup: let me see grant langston first half of the year when bubba and ricky was racing he got 3rd,4 and 5th:naughty: on the 07 after ricky and bubba was not racing he got 1st ,2 and 3rd on the 08:thinking: .remember when ricky took a break came back half way through the year and smoked everyboby by a half lap how was that 08 turning then:confused: ,im sorry he must have switched back to the 07 for that race:busted: .i have a 08 and love it but it really dont fell that much differnt from a 06 its all in your head.bubba would smoke every body on the track with a 1998 yz 400 i wonder how that bike turns:thumbsup:


okay so i read... :busted: 08 :busted: :ride: :lol: 06. :worthy: :goofy: :D Bubba, Ricky. :D :D :lol:

And do you have an 07? no you have an 06 and now an 08.

And what does your ramblings have to do with frame flex?

:cry: :cry: :lol: :lol:

  • tw557

Posted November 30, 2007 - 11:19 AM

#40

I bet a little frame flex is help full when getting kicked sideways in woops and landing from jumps a little side ways. As I look at this logically though the thin spoked wheel has got to flex alot more then a frame. And first the tire will need to flex to almost pulled off the bead to flex the rim. The big problem with a flexing frame is it has no dampening effect. It is like a shock or fork with ONLY springs. The frame is just a big leaf spring with no dampening. So as it flexes one way it will try and flex itself back to the opposite side backand forth till it all energy is dispersed. On a dirtbike excapt KTM all the forces are really being transmitted straight up thru the frame. Other then slamming into a berm with the front tire at possibly Grants speed I see no way the frame will twist flex. But this is only at the very entrance of the turn where the from is hitting the berm sideways. Maybe this is what Grant feels. I promise you, myself and MANY riders at our local races do not blow out the berms with that kind of force.





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