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Handling, single back tube vs twin spar frame flex SM ?

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  I am curious if anybody running your motards hard can tell a good bit of difference between the way a single down tube back frame handles compared to the twin spar for fast SM riding.

 

   I always liked the flex of the old school design single back frame for off road riding because the flex but I am a amateur maybe B level, I am wondering if the road style twin spar frames with less flex really work a good bit better road going for motard.

 

    Thanks for any input.

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I had a '03 CRF450R that I raced SM and also raced a Husaberg 550 with a steel frame.  I didn't notice a lot of difference in flex, but the CRF seemed a little more solid.  The Berg turned better, but it also had a 16.5 front.  I liked the way the CRF felt with tall bars and forward adjustable clamps, as I am 6'6".  I also ran the forks up about 1/4" in the clamps for more steering.

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I am 6foot4 and did not like the CRF 450 03 for off road riding because how stiff it was but for road motard if set up right it is about as good as gets for a big goof such as myself ? I bought a 05 CRF 450 and the ergos and bike was to small and uncomfortable for me even though on paper it is a much better bike.

I want to build a 80 HP Liger CR500 CRF 450 Street Legal Tard and before I do this I need opinions from tall guys who have run these on the streets. I want a good slider bike chasses.

It is a lot of work to build a bike like this.

Thanks for helping me.

Edited by Whipitnow

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I personally like my KTM much better than My RMZ.  I have a lot more front end feel on the KTM.  On my rmz I had to run Bridgestone soft slick cause other tires would just let go.  I wont say it was just the frame difference but i feel like the single back bone frame helps.

 

The SM guys over seas race every bike but they also have endless changes they can make to wheel base and offset on their bikes.  I also know HMC  used to brace their KTM frames...

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I personally like my KTM much better than My RMZ.  I have a lot more front end feel on the KTM.  On my rmz I had to run Bridgestone soft slick cause other tires would just let go.  I wont say it was just the frame difference but i feel like the single back bone frame helps.

 

The SM guys over seas race every bike but they also have endless changes they can make to wheel base and offset on their bikes.  I also know HMC  used to brace their KTM frames...

Thanks that is helpful, I think because the earlier CRF was a slower geometry chasses it may have a more connected print with the street up front? If KTM braced the frames for street use that tells me why street bikes have a cradle frame? to eliminate the head stay from flexing in corners?

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Thanks that is helpful, I think because the earlier CRF was a slower geometry chasses it may have a more connected print with the street up front? If KTM braced the frames for street use that tells me why street bikes have a cradle frame? to eliminate the head stay from flexing in corners?

 

no not for the street.  the race teams modified the stock SMR frame from what i understand to make it stiffer.  maybe cause they were pushing a good deal more HP through I dont know.  KTM didnt make a street legal SM until their bigger bikes like the690smc.  Lots of guys take the exc models and convert them though.  the 500exc is a very popular conversion.

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 I wonder where they braced it?  I know a street bike uses a twin spar for a reason?

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swing arm area and back bone area.  This is something i pulled from SMJ.

 

"Yeah, looks like an 04 frame with an 05 swingarm. The 2005 was the oval tube frame and the HMC frame had an exhaust mount on each side for the dual exhaust, the lower left subframe mount was higher to accomodate the carbon airbox, the peg mounts were raised, there were two extra braces added in the neck area by the coil mount, as well as the cross tube between the lower frame rails. I think some of those bikes were also running a third oil pump but not sure? I dont know much about the internals but im sure those motors were badass! The triple clamps look like the wide ones and HMC's offsets were in the 8.5 to 12.5mm range. Good luck on your search!"

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swing arm area and back bone area.  This is something i pulled from SMJ.

 

"Yeah, looks like an 04 frame with an 05 swingarm. The 2005 was the oval tube frame and the HMC frame had an exhaust mount on each side for the dual exhaust, the lower left subframe mount was higher to accomodate the carbon airbox, the peg mounts were raised, there were two extra braces added in the neck area by the coil mount, as well as the cross tube between the lower frame rails. I think some of those bikes were also running a third oil pump but not sure? I dont know much about the internals but im sure those motors were badass! The triple clamps look like the wide ones and HMC's offsets were in the 8.5 to 12.5mm range. Good luck on your search!"

You gave me a lot of info thanks, they want a stiffer frame for fast road going pushing the chasses in the corners. The thing I heard about some of the aluminum bikes was they were know in certain instances to drop right out from under you in corners but this was a conversation with a guy who like the single tube steel better and motarded a steel CR 500..

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You gave me a lot of info thanks, they want a stiffer frame for fast road going pushing the chasses in the corners. The thing I heard about some of the aluminum bikes was they were know in certain instances to drop right out from under you in corners but this was a conversation with a guy who like the single tube steel better and motarded a steel CR 500..

 

 

For whatever its worth here are 2 of my lowsides.  Both were with a set of GoldenTyre slicks,  The old style that was known to have issues.  But there was little to no warning.  Im sure a lot of it is "user error" cause that bike was real jumpy on/off throttle but on other tires i didnt have that problem.

 

 

here is the full speed session.  the comment shows you the time where both lowsides happen.  6:30 and 11 something.

 

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Thank you , I really appreciate it. So your KTM is better about that? I wonder if the steering was more relaxed if it would help. You go pretty good and you are right 80 horses for that is to much.

Again thanks. I think for a 80 horse motard a Bigger CRF chasses 1st gen may be welcome or maybe even a bigger framed bike?

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If they are bracing it they are taking the flex out, I wonder if the reason is the steering is to tight and wheel base to short? I need to talk to a chasses expert and do some reading. Thanks again ALOT!

So your KTM gives better feed back so you know when you are getting in trouble and can correct in time before the bike just slides out?

I will give some cornering up for a better slider, the bike I want to build is more point and shoot even if it is not as good. A Hooligan special for a Wanna Be.

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If they are bracing it they are taking the flex out, I wonder if the reason is the steering is to tight and wheel base to short? I need to talk to a chasses expert and do some reading. Thanks again ALOT!

So your KTM gives better feed back so you know when you are getting in trouble and can correct in time before the bike just slides out?

I will give some cornering up for a better slider, the bike I want to build is more point and shoot even if it is not as good. A Hooligan special for a Wanna Be.

 

 

There are some important differences in setup i should mention.  The rmz had a 17 front, ktm has a 16.5 front.  RMZ suspension was setup for SM, the KTM is still MX.

 

I was never able to get rid of the front end chatter and lack of feel on the RMZ.  I was getting ready to get a set of offset clamps and throw my 16.5 front rim on when i just decided to go KTM.  And my first track day on the KTM solidified the deal and I sold the RMZ.  I was, without pushing even 75% of what i did on the rmz, 1 sec a lap faster on a 40s a lap track.  On the RMZ with any tires other than Bridgestone the bike would drop out from under me like in the slowmo videos.  With the Bridgestones i was able to get the front end to slide and chatter but hold.  The other tires I tried on it all had very hard carcass where the bridgestone was very soft.  Thats the only thing i can think is that the tire would actually comply a lot more.  not really something you can get with a street tire. 

 

I think geometry and chassis flex play a big role, but i think the power characteristics of the RMZ didnt help.  It was very on/off low in the rpms which upsets the chassis mid turn.  I played around with dragging the front brake a little in turns, being in a higher gear etc. The KTM is very smooth with more power but it doesnt hit hard like a 2 stroke. 

 

The CR500two stroke goes into the ktm chassis very easily and that might be a good option for you?  I think any of the SXF chassis 07+ would be good options.  I know the 250sxf is a popular choice.  Also you can still buy a 700cc two stroke made by ktm.  Maico Intimidator 700...

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Yaa thanks a million, Yaa a KTM CR 5 look pretty cool. Does KTM still come with street title?

I am going to research chasses setup so I do not build a turd. A CR 5 for this is probably a big turd but a high HP 2 smoker would be fun.

It was fun watching you go at it.

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I have experience with YZ's  03-05 back cone steel frame, 06-09 backbone aluminum frame and 10-14 perimeter aluminum frame.  All set up with similar wheels and clamp offsets.  The 03-05 steel frame was very forgiving and did nothing wrong.  The 06-09 felt more precise but was also more sensitive to suspension settings.  It could be very harsh if the suspension was off a few clicks.  My current bike an 11 is super precise and provides great front end feedback.  It is also very sensitive to suspension.  It can go from great to bad with just a few clicks.

 

My preference is the precision of the aluminum frames but only if you are going to put in the time to get the suspension right.

 

I also like to run the suspension slightly "softer" with the aluminum frame.

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I have experience with YZ's  03-05 back cone steel frame, 06-09 backbone aluminum frame and 10-14 perimeter aluminum frame.  All set up with similar wheels and clamp offsets.  The 03-05 steel frame was very forgiving and did nothing wrong.  The 06-09 felt more precise but was also more sensitive to suspension settings.  It could be very harsh if the suspension was off a few clicks.  My current bike an 11 is super precise and provides great front end feedback.  It is also very sensitive to suspension.  It can go from great to bad with just a few clicks.

 

My preference is the precision of the aluminum frames but only if you are going to put in the time to get the suspension right.

 

I also like to run the suspension slightly "softer" with the aluminum frame.

So basically the new frames designs are better but are more fatiguing as far as stiffness goes, I think the old CHROMO were not as precise but for the long haul were easier to ride. This came to me through the grape vine about 10 yeara ago from a inside old school source in the California motor head circles that the pros preferred the steel better because they could moto longer on steel without fatigue setting in.

The real reason the manufactures went to aluminum was because it was cheaper to make the frames and they do look so cool. The pros would take steel if they could get them that was the inside info.

Edited by Whipitnow

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So basically the new frames designs are better but are more fatiguing as far as stiffness goes, I think the old CHROMO were not as precise but for the long haul were easier to ride. This came to me through the grape vine about 10 yeara ago from a inside old school source in the California motor head circles that the pros preferred the steel better because they could moto longer on steel without fatigue setting in.

The real reason the manufactures went to aluminum was because it was cheaper to make the frames and they do look so cool. The pros would take steel if they could get them that was the inside info.

I don't know about that.  Everything is a tradeoff.  The KTM steel frames seem plenty stiff. I think design has as much to do with it as material.  I think it is a general consensus that most of the early aluminum frames were to stiff.  I don't think that is an issue any longer.

 

I bet if you took a young hot shoe that has only ridden aluminum frames and put them on a 90's generation steel frame they would not be singing its praises.

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I don't know about that.  Everything is a tradeoff.  The KTM steel frames seem plenty stiff. I think design has as much to do with it as material.  I think it is a general consensus that most of the early aluminum frames were to stiff.  I don't think that is an issue any longer.

 

I bet if you took a young hot shoe that has only ridden aluminum frames and put them on a 90's generation steel frame they would not be singing its praises.

 

http://twostrokemotocross.com/2008/10/mxa-shootout-crf450-versus-cr500/

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So you post an article that basically says if a CR500 had a modern chassis it would be competitive?  I don't get it.

 

I had an early 90's CR500.   I actually thought it was an easy bike to ride for a novice.  Power was controllable chassis was decent.  Great bike.  I have also ridden aluminum frame 500 conversions.  I like them too but more for the ergonomics than the material of the frame.

 

I also have a bit of time on Modern KTM's which I would consider state of the art for Steel frame construction.  They feel a bit weird to me.  Can not pin point it but it is not really a performance issue.  Just subjective.  Fortunately we have choices. 

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So you post an article that basically says if a CR500 had a modern chassis it would be competitive?  I don't get it.

 

I had an early 90's CR500.   I actually thought it was an easy bike to ride for a novice.  Power was controllable chassis was decent.  Great bike.  I have also ridden aluminum frame 500 conversions.  I like them too but more for the ergonomics than the material of the frame.

 

I also have a bit of time on Modern KTM's which I would consider state of the art for Steel frame construction.  They feel a bit weird to me.  Can not pin point it but it is not really a performance issue.  Just subjective.  Fortunately we have choices. 

 

 

I just posted it as a reference.  Of course they are talking dirt and not supermoto.  I dont like the ktm PDS setups but the bikes with linkage i think handle really well.  Were the ktms that you rode the PDS rear setup?  The difference between them to me is noticeable.  Of course I have ridden them back to back on the same course BUT it was my 250 and my 450 so they were different in more than that.

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