Steel frame stretch a real concern?

Cadpro18
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Cadpro18 8/26/2016 6:51am
8/26/2016 6:51am
philG wrote:
No, i agree its as valid a check as you can get , and your maths is fine. I just know people who do the same...
No, i agree its as valid a check as you can get , and your maths is fine.

I just know people who do the same and think the frame has gone that much LOL.

We sold adjustable clamps here in the UK to pull in the head angle to get race geometry out of road frames, we built a bike for a guy , he built his van to take the bike, then bought a second bike and fitted his own clamps, couldnt understand why it was shit.. i asked him to bring them both over , the fact that the second bike didnt fit in his van wasnt enough to tip him off that the inserts were in backwards.

I measure for a living , and its easy to get weird numbers if you dont get everything right.
I take a few measurement myself on occasion... sometimes with a tape measure... sometimes with a 6-axis Romer CMM.Wink
Fearo
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Fearo 8/26/2016 9:21am
8/26/2016 9:21am Edited Date/Time 8/26/2016 9:22am
This type of question always brings out both extremes of the vitard spectrum.

A) The guys that overthink these things and tell you your bike will explode of you don't follow their logic
B ) The Trevor Pastrami-type guys that start laughing and just tell you to hold ER wwwiiiiideee open.

In reality your own assumption is probably not far from the truth. Not a concern for people that buy new bikes every 1-3 years but perhaps for older bikes. And if it did stretch out of spec, I would assume the steering would be affected, especially at turn entry, but probably minimal.
philG
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philG 8/26/2016 9:53am
8/26/2016 9:53am
Cadpro18 wrote:
I take a few measurement myself on occasion... sometimes with a tape measure... sometimes with a 6-axis Romer CMM.Wink
We have a Romer for the stuff that just needs to be somewhere near LOL.

I have measured 2 new frames , and swingarms, the difference was scary.
kawasa84
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kawasa84 8/26/2016 12:20pm
8/26/2016 12:20pm
Cadpro18 wrote:
I take a few measurement myself on occasion... sometimes with a tape measure... sometimes with a 6-axis Romer CMM.Wink
philG wrote:
We have a Romer for the stuff that just needs to be somewhere near LOL. I have measured 2 new frames , and swingarms, the difference...
We have a Romer for the stuff that just needs to be somewhere near LOL.

I have measured 2 new frames , and swingarms, the difference was scary.
Zeiss, is the only way to go.

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Steely Dan
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Steely Dan 8/26/2016 12:35pm
8/26/2016 12:35pm
That guy who posts here Rob Andrews was racing the factory CR500 in the early 90s, and said he cased a triple step up somewhere, and stretched the frame to the degree that when they tried to load it back into the truck, it didnt fit. Was too long.
Cadpro18
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Cadpro18 8/26/2016 12:54pm
8/26/2016 12:54pm Edited Date/Time 8/26/2016 2:00pm
Cadpro18 wrote:
I take a few measurement myself on occasion... sometimes with a tape measure... sometimes with a 6-axis Romer CMM.Wink
philG wrote:
We have a Romer for the stuff that just needs to be somewhere near LOL. I have measured 2 new frames , and swingarms, the difference...
We have a Romer for the stuff that just needs to be somewhere near LOL.

I have measured 2 new frames , and swingarms, the difference was scary.
kawasa84 wrote:
Zeiss, is the only way to go.
Portability was a requirement and an accuracy of somewhere near is fine for my application.
TransMotoSport 8/26/2016 1:53pm
8/26/2016 1:53pm
Joko wrote:
After listening to the 8/23/16 Pulpmx show when Steve M talked about how their steel YZ250's frame would stretch 1/4" after its first time out, and...
After listening to the 8/23/16 Pulpmx show when Steve M talked about how their steel YZ250's frame would stretch 1/4" after its first time out, and JT saying it was be a noticeable change in handling, and the new KTM steel frames are changed 5x a season at the pro level makes me wonder if this is a real problem when considering owning a KTM for an extended length of time? I also recall reading RC would go through KX250 frames on a monthly basis. Is the stretch dimension realized from the centerline of the steering head to the centerline of the swingarm pivot? Can it be repaired or reinforced to prevent stretch? Most of us probably couldn't stretch a frame in a season, but maybe after 3+ seasons of use? What is the noticeable change in handling on a stretched frame ... Does it gets too raked out and doesn't turn as sharp?
I used to ride KTM's with pds and the shock was offset to one side, after some hard hits the bike felt like it was crabbing. usually by a week after new. I rode a 2016 350 SXF for a week, sad to say I felt it was crabbing too, rear wheel does not want to follow the front wheel, I have been waiting to see if there was any feedback from pro's that the 2016 has to much flex, but i havent seen anything yet. Anybody else have this feeling with the 2016?
seth505
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seth505 8/26/2016 1:56pm
8/26/2016 1:56pm
philG wrote:
We have a Romer for the stuff that just needs to be somewhere near LOL. I have measured 2 new frames , and swingarms, the difference...
We have a Romer for the stuff that just needs to be somewhere near LOL.

I have measured 2 new frames , and swingarms, the difference was scary.
kawasa84 wrote:
Zeiss, is the only way to go.
Cadpro18 wrote:
Portability was a requirement and an accuracy of somewhere near is fine for my application.
We have close to the biggest CMM in the country that sits on it's own foundation Whistling
philG
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philG 8/26/2016 2:04pm
8/26/2016 2:04pm Edited Date/Time 8/26/2016 3:06pm
philG wrote:
We have a Romer for the stuff that just needs to be somewhere near LOL. I have measured 2 new frames , and swingarms, the difference...
We have a Romer for the stuff that just needs to be somewhere near LOL.

I have measured 2 new frames , and swingarms, the difference was scary.
kawasa84 wrote:
Zeiss, is the only way to go.
Cadpro18 wrote:
Portability was a requirement and an accuracy of somewhere near is fine for my application.
LOL.. Romers are good kit, but not my specialty , im a Revo man, its the Factory Bike of CMM's .. but Zeiss is what hits the numbers.. as long as you can wait for them.

We have an HPO Laser probe on a PMM-C.. they are claiming first term accuracy of 0.3Um

Had a Zeiss with an RDS on it, nice kit, as good as our Leitz

its a shame that knowing exactly what size everything is, doesnt make me faster,or get me laid
colintrax
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colintrax 8/26/2016 7:53pm
8/26/2016 7:53pm
TransMotoSport wrote:
I used to ride KTM's with pds and the shock was offset to one side, after some hard hits the bike felt like it was crabbing...
I used to ride KTM's with pds and the shock was offset to one side, after some hard hits the bike felt like it was crabbing. usually by a week after new. I rode a 2016 350 SXF for a week, sad to say I felt it was crabbing too, rear wheel does not want to follow the front wheel, I have been waiting to see if there was any feedback from pro's that the 2016 has to much flex, but i havent seen anything yet. Anybody else have this feeling with the 2016?
I'd put my money on you adjusting the chain and not getting the rear wheel straight. My KTM is almost 5 years old and she don't crab walk
ratonmacias
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ratonmacias 8/26/2016 10:23pm
8/26/2016 10:23pm
I remember the 90's kx bikes had the footpeg tips pointing down after a few months of riding.
JWACK
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JWACK 8/26/2016 10:27pm
8/26/2016 10:27pm
I bought 2 new rm 250 2 smokers in 2007. I was riding and racing every week. This was the first year they allowed the 2 stroke 250 to compete in the 250 class in the pro am class so I jumped on that wagon.. Well in one year of riding multiple times a week racing hard.. And jumping some stupid shit I stretched both frames to the point that it broke the cylinder head mounts on both bikes.. I Ordered new head stays and had to Waller out the cylinder side for the bolt to fit through.. Maybe I got two lemon frames but it scared me out of jumping fifth gear wide on them!
TransMotoSport 8/27/2016 1:13am
8/27/2016 1:13am
TransMotoSport wrote:
I used to ride KTM's with pds and the shock was offset to one side, after some hard hits the bike felt like it was crabbing...
I used to ride KTM's with pds and the shock was offset to one side, after some hard hits the bike felt like it was crabbing. usually by a week after new. I rode a 2016 350 SXF for a week, sad to say I felt it was crabbing too, rear wheel does not want to follow the front wheel, I have been waiting to see if there was any feedback from pro's that the 2016 has to much flex, but i havent seen anything yet. Anybody else have this feeling with the 2016?
colintrax wrote:
I'd put my money on you adjusting the chain and not getting the rear wheel straight. My KTM is almost 5 years old and she don't...
I'd put my money on you adjusting the chain and not getting the rear wheel straight. My KTM is almost 5 years old and she don't crab walk
Youd think if my feeling was correct others would have complained. Aye. Lol
The rear wheel on the 2016 possibly may have not been straight. It wasnt mine i didnt check.
Markee
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Markee 8/27/2016 4:57am
8/27/2016 4:57am
philG wrote:
The reason guys didn't jump them like that back in the day, was because they knew what would happen .. Metal flexes, and keeping a track...
The reason guys didn't jump them like that back in the day, was because they knew what would happen ..

Metal flexes, and keeping a track of it is it pretty hard , I know when I have scanned bikes in the past , getting good numbers is hard work. Measuring a bare frame is easy , you just need a point of reference that isn't going anywhere, and on a dirt bike , that is hard to do.



The way you measure it can make a huge difference to the perceived results as well

Thats pretty awesome.

I use a FARO laser at work for equipment alignment and would be interesting to see if a frame changes from one season of riding. I have a KTM 2 smoke, 3 years old.

http://www.faro.com/en-us/products/metrology/faro-laser-tracker/overview
ATKpilot99
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ATKpilot99 8/27/2016 6:40am
8/27/2016 6:40am
I just picked up a 1981 RM 125. According to this thread the wheelbase should be about 70 inches.
Dirty Points 8/29/2016 12:43pm
8/29/2016 12:43pm
ATKpilot99 wrote:
I just picked up a 1981 RM 125. According to this thread the wheelbase should be about 70 inches.
If the swingarm bushings are in typical condition for an '81 RM125, it already is, sometimes!
JerseyFresh
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JerseyFresh 8/29/2016 1:27pm
8/29/2016 1:27pm Edited Date/Time 8/29/2016 1:27pm
Gee I brought this up a few months ago about my old RM250 and got told I was a lying trash can and that it was impossible to stretch a frame unless youre a factory pro. Dry

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philG
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philG 8/29/2016 3:01pm
8/29/2016 3:01pm
philG wrote:
The reason guys didn't jump them like that back in the day, was because they knew what would happen .. Metal flexes, and keeping a track...
The reason guys didn't jump them like that back in the day, was because they knew what would happen ..

Metal flexes, and keeping a track of it is it pretty hard , I know when I have scanned bikes in the past , getting good numbers is hard work. Measuring a bare frame is easy , you just need a point of reference that isn't going anywhere, and on a dirt bike , that is hard to do.



The way you measure it can make a huge difference to the perceived results as well

Markee wrote:
Thats pretty awesome. I use a FARO laser at work for equipment alignment and would be interesting to see if a frame changes from one season...
Thats pretty awesome.

I use a FARO laser at work for equipment alignment and would be interesting to see if a frame changes from one season of riding. I have a KTM 2 smoke, 3 years old.

http://www.faro.com/en-us/products/metrology/faro-laser-tracker/overview
Thats a nice peice of kit , we have a Leitz one which is pretty good, working on some aero stuff using laser scanners , gantry mounted robots and the tracker.. very interesting, for sure, but i tend to do the more accurate stuff ,

The picture is just one i use in a presentation, trying to measure a complete bike strapped to a table like that is like herding cats, unless you are scanning it,

Nice to know im not the only measurement nerd on here , its a shame it doesnt help us much with regards to racing.

We are looking at printed parts for a number of customers, its easy enough to make, but validating the printing is a lot of work for our X Ray guy.
BobPA
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BobPA 8/29/2016 3:03pm
8/29/2016 3:03pm
Joko wrote:
After listening to the 8/23/16 Pulpmx show when Steve M talked about how their steel YZ250's frame would stretch 1/4" after its first time out, and...
After listening to the 8/23/16 Pulpmx show when Steve M talked about how their steel YZ250's frame would stretch 1/4" after its first time out, and JT saying it was be a noticeable change in handling, and the new KTM steel frames are changed 5x a season at the pro level makes me wonder if this is a real problem when considering owning a KTM for an extended length of time? I also recall reading RC would go through KX250 frames on a monthly basis. Is the stretch dimension realized from the centerline of the steering head to the centerline of the swingarm pivot? Can it be repaired or reinforced to prevent stretch? Most of us probably couldn't stretch a frame in a season, but maybe after 3+ seasons of use? What is the noticeable change in handling on a stretched frame ... Does it gets too raked out and doesn't turn as sharp?
TransMotoSport wrote:
I used to ride KTM's with pds and the shock was offset to one side, after some hard hits the bike felt like it was crabbing...
I used to ride KTM's with pds and the shock was offset to one side, after some hard hits the bike felt like it was crabbing. usually by a week after new. I rode a 2016 350 SXF for a week, sad to say I felt it was crabbing too, rear wheel does not want to follow the front wheel, I have been waiting to see if there was any feedback from pro's that the 2016 has to much flex, but i havent seen anything yet. Anybody else have this feeling with the 2016?
Your brain is crabbing man.

Straighten your back wheel

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