Frame Flex

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12/13/2017 10:25 AM

How hard is it to determine frame flex with frames made of the same material? I consistently hear keefer, vital and various other test riders talk about frame flex during shootouts. I can distinctly feel a difference in suspension clickers, valving and bar flex, but don’t think I would be able to isolate frame flex specifically. What kind of numbers are we talking about here? I know rake angles change on frames over time but can you really feel damping in your frame?

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12/13/2017 10:27 AM

If youre a world class athlete yes. I went from a streel frame to an alum and didnt even notice anything like that

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2009 Kawasaki KX450F
2009 Kawasaki KX250F
2002 Suzuki GSXR 600

12/13/2017 12:04 PM

No

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12/13/2017 12:07 PM
Edited Date/Time: 12/13/2017 12:09 PM

Frame flex no, but it took me a whole 5 seconds to notice the KTM450 is WAY lighter than my YZ450 laughing

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12/13/2017 12:37 PM

You can feel frame flex but most don't know what they are feeling. Some think it's suspension being too harsh/soft or bar flex or even tires. A good test rider will weed out those items like suspension, bar, tire and then go after the chassis and how it feels.

If you want to feel how sensitive a frame can be (for example) 2017/2018 CRF450R. Change the torque settings by 10-15% on all of the motor mounts and swingarm pivot. Ride the bike stock then reduce the torque settings and ride the bike again (don't change any other settings) feel the difference.

It is all about flex flex and flex. Triple clamps flex and clamp pinch bolt torque settings can change how a bike flexes. Axles flex, everything has to flex a little. Some factory bikes don't run Ti axles because they might not flex enough, or some run them because they don't flex - just depends.

A good test rider can isolate each item and deduce in the end if the flex is suspension related or a frame that has too much or not enough flex and feels harsh. OEM's have spent a lot of time with the latest bikes to allow the frames to be stiffer rotational - yet flex over a greater span front to back so they don't feel harsh.

If a frame is too soft they can feel mushy or twist and store energy and then when they flex back it does all sorts of stuff to the chassis like swapping or not tracking straight. Slower vet riders like a frame that flexes, that is why the YZ450F has been such a popular bike, fast pros did not like the flex.

The average rider does not do enough or any testing, they ride a bike, make basic changes they read somewhere or they just send their suspension off and think the shop has all of the answers. Testing and setting up a bike can be a battle. There is a fine line between a decent bike and an awesome bike and the only cost is testing and a log book to track what works and does not work.

Every rider can feel flex, most just think because the wheels are the only things moving up and down, that is all they are feeling, not always true.

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12/13/2017 12:45 PM
Edited Date/Time: 12/13/2017 12:46 PM

PracticeChamp141 wrote:

How hard is it to determine frame flex with frames made of the same material? I consistently hear keefer, vital and various other test riders talk about frame flex during shootouts. I can distinctly feel a difference in suspension clickers, valving and bar flex, but don’t think I would be able to isolate frame flex specifically. What kind of numbers are we talking about here? I know rake angles change on frames over time but can you really feel damping in your frame?

I would bet a lot of the guys who talk about frame flex in these shootouts would not be able to pass the Pepsi challenge. I.E. if you lined up 5 identical looking bikes with different, but known, flex characteristics and asked them to filled out an accurate report on each. Unless you are riding a bunch of similar frames back to back, I am doubting us normals can ever notice.

Also, just because someone is fast on a bike does not mean, in the slightest, that they can feel subtle changes. Corner speed does not equal set up ability.

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Tomac and/or Anderson for 2020.....

12/13/2017 12:48 PM

I personally can't feel a thing.

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12/13/2017 12:53 PM

smrscott wrote:

You can feel frame flex but most don't know what they are feeling. Some think it's suspension being too harsh/soft or bar flex or even tires. A good test rider will weed out those items like suspension, bar, tire and then go after the chassis and how it feels.

If you want to feel how sensitive a frame can be (for example) 2017/2018 CRF450R. Change the torque settings by 10-15% on all of the motor mounts and swingarm pivot. Ride the bike stock then reduce the torque settings and ride the bike again (don't change any other settings) feel the difference.

It is all about flex flex and flex. Triple clamps flex and clamp pinch bolt torque settings can change how a bike flexes. Axles flex, everything has to flex a little. Some factory bikes don't run Ti axles because they might not flex enough, or some run them because they don't flex - just depends.

A good test rider can isolate each item and deduce in the end if the flex is suspension related or a frame that has too much or not enough flex and feels harsh. OEM's have spent a lot of time with the latest bikes to allow the frames to be stiffer rotational - yet flex over a greater span front to back so they don't feel harsh.

If a frame is too soft they can feel mushy or twist and store energy and then when they flex back it does all sorts of stuff to the chassis like swapping or not tracking straight. Slower vet riders like a frame that flexes, that is why the YZ450F has been such a popular bike, fast pros did not like the flex.

The average rider does not do enough or any testing, they ride a bike, make basic changes they read somewhere or they just send their suspension off and think the shop has all of the answers. Testing and setting up a bike can be a battle. There is a fine line between a decent bike and an awesome bike and the only cost is testing and a log book to track what works and does not work.

Every rider can feel flex, most just think because the wheels are the only things moving up and down, that is all they are feeling, not always true.

Never deviate from the OEMs recommended torques. 10-15% seems minor, but it's not.



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12/13/2017 1:07 PM

PracticeChamp141 wrote:

How hard is it to determine frame flex with frames made of the same material? I consistently hear keefer, vital and various other test riders talk about frame flex during shootouts. I can distinctly feel a difference in suspension clickers, valving and bar flex, but don’t think I would be able to isolate frame flex specifically. What kind of numbers are we talking about here? I know rake angles change on frames over time but can you really feel damping in your frame?

BobPA wrote:

I would bet a lot of the guys who talk about frame flex in these shootouts would not be able to pass the Pepsi challenge. I.E. if you lined up 5 identical looking bikes with different, but known, flex characteristics and asked them to filled out an accurate report on each. Unless you are riding a bunch of similar frames back to back, I am doubting us normals can ever notice.

Also, just because someone is fast on a bike does not mean, in the slightest, that they can feel subtle changes. Corner speed does not equal set up ability.

I agree. Magazines talking about frame flex is even more rediculous than the claim that every other bike needs a new linkage

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12/13/2017 1:42 PM

Had a bloke on here tell me just the other day that he can feel frame flex after 5 or so hours on the bike ermm laughing

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12/13/2017 1:48 PM
Edited Date/Time: 12/13/2017 1:50 PM

144rider wrote:

Had a bloke on here tell me just the other day that he can feel frame flex after 5 or so hours on the bike ermm laughing

(Quote: RCMXracing)

Anyone who knows anything about steel frames is that they feel different after breaking them in, 5hrs or so. They feel better to me, don’t stay rigid like Aluminum. Factory riders are picky AF. Only thing that’s gone soft is your noodle.

http://www.vitalmx.com/forums/Moto-Related,20/Another-snapt-KTM-frame,1330488?exclusive_forum_user=false&page=4

laughing laughing laughing

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12/13/2017 2:29 PM

PracticeChamp141 wrote:

How hard is it to determine frame flex with frames made of the same material? I consistently hear keefer, vital and various other test riders talk about frame flex during shootouts. I can distinctly feel a difference in suspension clickers, valving and bar flex, but don’t think I would be able to isolate frame flex specifically. What kind of numbers are we talking about here? I know rake angles change on frames over time but can you really feel damping in your frame?

BobPA wrote:

I would bet a lot of the guys who talk about frame flex in these shootouts would not be able to pass the Pepsi challenge. I.E. if you lined up 5 identical looking bikes with different, but known, flex characteristics and asked them to filled out an accurate report on each. Unless you are riding a bunch of similar frames back to back, I am doubting us normals can ever notice.

Also, just because someone is fast on a bike does not mean, in the slightest, that they can feel subtle changes. Corner speed does not equal set up ability.

Dude I can barely tell the difference in intermediate and hard pack tires!

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12/13/2017 3:12 PM

If you want to feel the difference compare any steel frame bike to a 1997 CR250.

I guarantee you will know which bike has less frame flex. Then you will have a better understanding of how frame flex affects handling.

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You kids get off my lawn!

2013 KTM450 Factory Edition
Projects......lots of projects!

12/13/2017 6:27 PM

I can tell on my MTB but not so much a mx bike

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12/13/2017 7:15 PM

kkawboy14 wrote:

Dude I can barely tell the difference in intermediate and hard pack tires!

I’m with you bro.
(Doesn’t stop me buying a Ti bolt for my clutch perch!)

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12/13/2017 7:45 PM

DavetheVintageGuy wrote:

If you want to feel the difference compare any steel frame bike to a 1997 CR250.

I guarantee you will know which bike has less frame flex. Then you will have a better understanding of how frame flex affects handling.

You beat me to it. After owning 97, 01 Cr250's in comparison to 02-07 models there is a noticeable difference. The 1st gen AF 97-99 & 2nd gen AF 00-01 are rigid vs. the 3rd gen AF 02-07's. I'm not a pro rider, but the rigidity of the AF is felt as well as the handling characteristics.

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Speak softly and carry a big stick.

12/13/2017 8:55 PM

Oh yeah.. I can totally feel a frame clapped out after 5 hrs. That's the aluminum ones. Only 3 hrs on a KTM and it's unrideable, especially in the whoops. But it really depends on how much rust patina is on the inside of the tubes. So maybe only 2 hrs in florida but more like 4 in Minnesota. Need a scope to look inside to be sure. Solid mounted skid plates are the worst. Drop 4-5 positions each moto with one. I even have to have my rad shroud and sidepanel bolts torqued to spec. 1-2 in/lb's off and the bike is a sloppy mess or harsh as an old nun in catholic school. Most important is exhaust mounts or carb boot clamps. Most important part to torque. Think about it, they tie the chassis and engine together.

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Powerband in every gear !

12/13/2017 9:04 PM

BobPA wrote:

I would bet a lot of the guys who talk about frame flex in these shootouts would not be able to pass the Pepsi challenge. I.E. if you lined up 5 identical looking bikes with different, but known, flex characteristics and asked them to filled out an accurate report on each. Unless you are riding a bunch of similar frames back to back, I am doubting us normals can ever notice.

Also, just because someone is fast on a bike does not mean, in the slightest, that they can feel subtle changes. Corner speed does not equal set up ability.

I'm slow as shit, and only OK at setting up my suspension but I can feel the difference in between bike frames. Particularly aluminum to steel.

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12/14/2017 3:54 AM

colintrax wrote:

I'm slow as shit, and only OK at setting up my suspension but I can feel the difference in between bike frames. Particularly aluminum to steel.

Same for me. I've ridden my 08 RM250 and 15 RMZ450 back to back on the same track and the difference between the 2 is noticeable, particularly on the really harsh square edge hits. The aluminum frame definitely transfers more to the rider.

I've also experimented and noticed a difference (could be placebo effect) with removing one of the upper engine frame mount bolts on both sides of my RMZ. This in theory allows the engine/ frame mount to pivot, as it is now held on with 2 opposing bolts as opposed to 3 in a triangle pattern.

I guess it all depends how in tune you are with your bike and also how fussy you are in terms of comfort and set up.

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@russ_69

12/14/2017 6:33 AM

PracticeChamp141 wrote:

How hard is it to determine frame flex with frames made of the same material? I consistently hear keefer, vital and various other test riders talk about frame flex during shootouts. I can distinctly feel a difference in suspension clickers, valving and bar flex, but don’t think I would be able to isolate frame flex specifically. What kind of numbers are we talking about here? I know rake angles change on frames over time but can you really feel damping in your frame?

BobPA wrote:

I would bet a lot of the guys who talk about frame flex in these shootouts would not be able to pass the Pepsi challenge. I.E. if you lined up 5 identical looking bikes with different, but known, flex characteristics and asked them to filled out an accurate report on each. Unless you are riding a bunch of similar frames back to back, I am doubting us normals can ever notice.

Also, just because someone is fast on a bike does not mean, in the slightest, that they can feel subtle changes. Corner speed does not equal set up ability.

Bruce372 wrote:

I agree. Magazines talking about frame flex is even more rediculous than the claim that every other bike needs a new linkage

Haha that is so accurate! grin The "go to" upgrade for the magazines is in probably 70% of the cases a lowering linkage.

Every. Single. Year.

I wonder why the manufacturers are so stubborn with the high riding linkage arms....whistling whistling

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12/14/2017 6:39 AM

BobPA wrote:

I would bet a lot of the guys who talk about frame flex in these shootouts would not be able to pass the Pepsi challenge. I.E. if you lined up 5 identical looking bikes with different, but known, flex characteristics and asked them to filled out an accurate report on each. Unless you are riding a bunch of similar frames back to back, I am doubting us normals can ever notice.

Also, just because someone is fast on a bike does not mean, in the slightest, that they can feel subtle changes. Corner speed does not equal set up ability.

Bruce372 wrote:

I agree. Magazines talking about frame flex is even more rediculous than the claim that every other bike needs a new linkage

Motofinne wrote:

Haha that is so accurate! grin The "go to" upgrade for the magazines is in probably 70% of the cases a lowering linkage.

Every. Single. Year.

I wonder why the manufacturers are so stubborn with the high riding linkage arms....whistling whistling

Dont forget triple clamp offsets from ride engineering

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2009 Kawasaki KX450F
2009 Kawasaki KX250F
2002 Suzuki GSXR 600

12/14/2017 9:04 AM

BobPA wrote:

I would bet a lot of the guys who talk about frame flex in these shootouts would not be able to pass the Pepsi challenge. I.E. if you lined up 5 identical looking bikes with different, but known, flex characteristics and asked them to filled out an accurate report on each. Unless you are riding a bunch of similar frames back to back, I am doubting us normals can ever notice.

Also, just because someone is fast on a bike does not mean, in the slightest, that they can feel subtle changes. Corner speed does not equal set up ability.

kkawboy14 wrote:

Dude I can barely tell the difference in intermediate and hard pack tires!

skypig wrote:

I’m with you bro.
(Doesn’t stop me buying a Ti bolt for my clutch perch!)

Agreed!

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12/14/2017 2:33 PM
Edited Date/Time: 12/14/2017 2:33 PM

DavetheVintageGuy wrote:

If you want to feel the difference compare any steel frame bike to a 1997 CR250.

I guarantee you will know which bike has less frame flex. Then you will have a better understanding of how frame flex affects handling.

H4L wrote:

You beat me to it. After owning 97, 01 Cr250's in comparison to 02-07 models there is a noticeable difference. The 1st gen AF 97-99 & 2nd gen AF 00-01 are rigid vs. the 3rd gen AF 02-07's. I'm not a pro rider, but the rigidity of the AF is felt as well as the handling characteristics.

I agree, rode the 2001 CR 125 for a year and then rode my friend's 98 RM 125. Felt like i was ice skating. Very loose feeling compared to the rigid CR.

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12/14/2017 2:48 PM

Taking two different brands of bikes is like comparing apples and oranges. Comparing a two stroke to a 4 stroke is like comparing oranges and cabbages.
Sorry guys!

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