USD forklegs?

17 replies to this topic
  • cat0020

Posted September 19, 2003 - 05:35 AM


Any XR650R owner that have changed their forks to USD (up side down)forks that have comments or ride impressions??
What kind of triple tree are you using with the USD forks?

  • JR650

Posted September 21, 2003 - 09:13 PM


sorry im not much help but ive been wondering the same thing, nice to lose some weight and get better steering, im wondering if i can cannibalize the front end off of a cr250 or 500, clamps might even work. someone out there has to know something. anyone?

  • qadsan

Posted September 21, 2003 - 09:49 PM


Back in March 2000, Dirt Bike featured a XR650R with USD forks. It's my understanding that Honda's Bruce Ogilvie came down on that article and said not to use USD forks on the XR650R because the frame wasn't designed for those types of stresses, which would fatigue it too much after a while.

The bike looked trick and I don't know how much truth there was in this, but you sure haven't seen the top notch riders such as Johnny Campbell, Steve Hengeveld, Tim Staab, Andy Grider, etc, using USD forks when riding their XR650R's and they have plenty of major victories behind them. Even Scott Summers has been racing a XR650R without USD forks and in fact the pictures I've seen of the XR650R he was riding are without his SRC brace installed.

  • XR250rdr

Posted September 22, 2003 - 05:43 AM


The pros may have a beefed up frame though... :)

  • cat0020

Posted September 22, 2003 - 07:08 AM


I wonder what kind of extra stress the frame would have to endure with USD forks?
If there is no difference in attachment from frame to the forklegs, there should not be different stress.. or maybe the USD forks can sustain more stress than the frame under stopping or turning conditions??

:) :D :D

  • qadsan

Posted September 22, 2003 - 09:29 AM


USD forks are more rigid than conventional forks, so they’ll transmit higher loads to the frame, thus fatiguing the frame quicker than with the conventional forks it was designed with. How much quicker is anyone’s guess without doing some real world experiments to back up the theory, but I’m quite happy with my current setup, especially after Rob Barnum revalved my forks & shock. You just don’t see the top pros using USD forks on their XR650R’s and that raises my skepticism about doing this even further. There have been a handful of people who have installed USD forks on their XR650R and I’ve never heard anything bad come from them, but that doesn’t mean too much in the scheme of things, especially for what ‘might’ happen in the future. I had read a post a ways back from someone who said that Honda once featured a XR650R with USD forks in a 2002 Canadian sales brochure that was for the 2001 Paris Dakar race, but I never seen this brochure and don’t know any other details behind it. I’m sure it would look just great and maybe would handle even better, but for how long is anyone’s guess.

Steel (and titanium) frames/structures can be designed & built so that the cyclic loading its subject to will be below its fatigue threshold, but aluminum on the other hand will fatigue at any load and has the worst fatigue strength by far when compared to steel or titanium. Also, aluminum will not give you easy to spot signs of fatigue until it’s too late unless you know exactly what you’re looking for with specialized equipment and it doesn’t propagate cracks like steel does. The farther aluminum flexes, the higher the stress peak will be and the shorter its fatigue life and when combined with enough stress cycles, fatigue in inevitable. Aluminum framed bikes/motorcycles tend to be very stiff, but not because of the material itself. They are designed that way on purpose, because allowing them to flex will significantly reduce their service life and that’s why the XR650R has a much stiffer frame than the XR600.

Please don’t get the wrong idea that our frames are junk and will shortly fatigue, because there are many factors beyond material choice that affect fatigue life such as the tube diameter, wall thickness, butted sections, surface finish, frame geometry, weld quality, component choices, etc, but USD forks will fatigue the XR650R frame quicker than conventional forks will. I just don’t know how much quicker it will fatigue for the average rider, but Honda obviously had some liability concerns and probably came out against this to cover them just incase. I’m quite confident that Honda made a top notch frame for its intended use and I’m not worried about my frame failing anytime soon, especially for the type and amount of riding I’m doing.

  • cat0020

Posted September 22, 2003 - 10:55 AM


Thanks Qadsan for all the insight.

I currently am toying around with the idea, since I have a rolling chassy from a Cannondale X440, I would like to swap the front end of the Cannondale to my XR650R. Those golden colored Ohlins USD forklegs are just too attractive to me, besides the Brembo brake/rotor and the Magura brake lever.. all those goodies I hope to be able to mount onto my XR650R, we'll see how things progress..

  • qadsan

Posted September 22, 2003 - 01:01 PM


I think if I had that kind of stuff in my possession, I'd probably be trying it also because I'm not going to be putting anywhere near the stress on my bike that some people do. If you PM me your email address, I'll email you a copy of that Dirt Bike article that shows a picture of the XR650R with USD forks. It's also available in the Yahoo XR650R group (if you're a member) at the following link:

http://f4.grp.yahoof...inder small.pdf

  • snowblind

Posted September 24, 2003 - 05:14 AM


If I had your setup, I'd be trying to find out how to put the XR motor in the Cannondale roller... :)

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  • cat0020

Posted September 24, 2003 - 07:01 AM


Yeah, I was thinking of the same, but engine dementions doesn't quite match up, Cannondale frame does have alot more room. maybe I can fit a turbo into the thing, too..
how badass would that be!!!

:D :D :D

If I had your setup, I'd be trying to find out how to put the XR motor in the Cannondale roller... :)

  • qadsan

Posted September 24, 2003 - 07:05 AM


maybe I can fit a turbo into the thing, too.. how badass would that be!!!

Here's some pictures to give you some ideas for your turbo project :)


An XR650R engine is a Cannondale roller sounds just awesome, especially a turbo version :D

  • BoZerk

Posted September 24, 2003 - 08:23 AM


That thing is insane!

Did you notice the guy has a cast on his arm? I wonder how he got that. I bet it's a big hit when the turbo boost kicks in.

I'll stick to my uncorked version and putt'n around the's safer. :)

  • cat0020

Posted September 24, 2003 - 11:25 AM


Hey, that's the Ohlin USD forks that I want to put on my XR.. actually, that's the turbo kit I want, too..

Posted Image

  • ill_caper

Posted September 24, 2003 - 03:06 PM


Ju :excuseme:st out of curiousity, why dont you guys just get an atk 700 2smoke or a ktm 525 if you want that much power, or a crf all hooked up...??? Just wondering?

  • JR650

Posted September 24, 2003 - 05:29 PM


very simple, there is no replacement for displacement. the brp is very detuned in stock form, probably capable of 95+hp NA with some fun and more torque than the ktm can ever dream of, the ktm 525 on the other hand is a very high strung bike from the factory with not alot left to give. I would bet that i could get WAY more power out of the 650R than a ktm 525 going all out. The atk is nuts, I want one. BTW, stock the 650R is pretty sad and pathetic, put a couple grand into the motor, i bet there are very few four strokes that could touch it.

  • ill_caper

Posted September 24, 2003 - 06:10 PM


I know. I owned a BRP for two years. I uncorked it bought an Edelbrock carb and tricked it out as much as possible. I loved the bike and it was so easy to ride. I got rid of it though due to seat height( I am 6'5) and the suspension (lack of). Have you tried other bikes? I bought the WR without riding any high performance 4 before and I was pleasantly surprised with the power. The new technology is amazing on these fours. It feels like a 2smoke 250 on the top end but also has tons of torque. Oh well I guess its all up to the individual. I was looking for more of a noticeable powerband hit like a 2smoke so thats why I opted for the WR. Although Ive heard the YZ and CRF have insane powerbands. There is definitely times when I miss the BRP but Im happy with my switch. Too bad I didnt have the money to buy everybike I wanted. That ATK 700 2smoke would be in my garage along with a BRP and my W and a YZ450. I think a CR500 as well.....I love to dream..Happy Riding..Im bored at work...can you tell?? Take care, D :D :) :D

  • JR650

Posted September 25, 2003 - 12:20 PM


i just love the low end snap of the big four strokes, i guess its like you said, all personal preferance. ive had all 2-smokes pretty well before i bought my BRP. i have ridden a ktm mxc450, nice bike, great power but id rather have a 250 2-stroke instead. Actually, because of my recent jumping addiction and my really heavy BRP, i am looking for a friend for it, cr500 bag bike to beat the crap out of and be able to fix without being bikeless. I thought about the CRF, but i heard it actually had a fairly sad powerband in comparison to the yzf, and i still want at least 5 speeds.
each to their own, as long as they ride something.

  • ill_caper

Posted September 25, 2003 - 12:34 PM


Cheers to that....Im gonna try my first turkey run next weekend...Its a race of some sorts but I odnt even really know anything about it..It sounds fun though :)

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