unstable steering at high speed: tarmac

Hi guys, recently i purchased a XR650R and i found that past 100 Km/h the steering becomes uncontrolable, not an up-down shaking but a side to side move that leads almost to lose control of the bike so i have to slow down. This is a scary issue.

 

I believed unbalanced wheels could lead to shaking but not this way. Tyres are set to 30 and i use knob tyres even in the tarmac. Im a light guy (135 lb) and i dont know if that could be the cause. the rear tyre is worn to a 70% and front is new but the issue comes from before i replaced it. i Know there are steering dampers but i guess it is not an issue to be expected so hard at 100Km/h.

 

best

 

 

 

 

100 KmH is around 60 MPH, too fast for MX knobbies on pavement. As for pressure, do you mean 30 PSI or 30 KPA? 30 KPA is way too low. If you’re wanting to regularly ride pavement on your XR, try dual sport tires with around 25 to 28 PSI.

Edited by Mike38

get DOT approved knobbies. it helps. also, see if your rims are all trued. a rim that isnt true will give you a good death wobble. lastly i would get them ballenced.

When you do develop steering oscillation, remember to press forward with both palms on the grips. That helps to dampen out the shake.

Better/newer tires helps too.

ALL!!!! above answers are completely wrong!!!! Before I even opened the thread, I figured you probably had an XR. Knobbies on the road have NOTHING to do with it. Doesn't matter if they are DOT or not. That weave is pretty common on XRs.  My XR 250 would weave like a bugger on hard packed gravel roads. On the pavement it was fine at 70mph with dot knobbies. My KTM 525 doesn't have a hint of it on the gravel, or the pavement at any speed, and it's on non DOT rubber. Try dropping your forks in your triple clamps. Have you ever set the sag on your bike? It may be riding too high in the back, and causing too sharp a steering angle. Also make damned sure your wheel bearings are all good, and your rear axle aligned properly

I've only owned mine a few months and haven't run it with knobbies so take my 2 cents accordingly. I geared mine up and ran it to Mexico, North Dakota and then back home to the northwest and ran 70 mph plus a lot on pavement and gravel and have never experienced any significant wobble.  It certainly bounces around as you tailgate a semi truck at freeway speeds  but that happens on all bikes to some degree.

 

I had a dot knobbie come off quickly twice at 60 mph on the rear of my xr400 and it was pretty intense/scary/dangerous,  these days I run more street oriented rubber or the Pirrelli mt 43 trials type for the most part.

 

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Hi guys, but the wobble is not specific to the knobbies, few days ago i had a semi street oriented front tyre and i had the same issue. the front knobbie is new i have installed iton saturday and it is DOT approved and is set to 30 PSI, i guess i could lower that number to 28. 

 

I used to have a XR250 and i changed its front and rear geometry many times and never had this issue.  I need some advice to set the right sag. Im about to balance both wheels, check again wheel bearings but i know they are well, recently when i purchased the bike it was 2 inches low in the triple clamps then i discovered the thing, but then the bike was set to its natural geometry and the same wobbling arises. Thats true when i push down on the handlebars the damn thing goes away but i can not safely ride this way.

 

Could my light weight help worsen the situation? i want to reduce this to a minimum before even trying a steering dampener

Edited by killabyte

Check that your wheels aren't out of true and that the rear isn't crooked (don't trust the alignment marks, use a tape measure from the axle to the swingarm pivot)

 

Also look over your frame for signs of damage.

The expert in wheels said that they should be somewhat oval so im going there to try to fix this homicide attempt , ill tell you then.

ALL!!!! above answers are completely wrong!!!!

Trying to make friends? Or perhaps you are just an ass, in addition to being a buffoon.

Sheesh. I see that this is a common way for you to enter a dialogue here. Maybe you should head elsewhere so you don't feel like you have to call everyone idiots while actually making a fool of yourself making incorrect statements. There is a reason why you think we are "all completely wrong", and its not because you have a farkin clue.

The expert in wheels said that they should be somewhat oval so im going there to try to fix this homicide attempt , ill tell you then.

 

:applause: ,,Somewhat oval...must be taking the p%&*,, :jawdrop: ,,Wouldn't be much good if they were square.. :)

 

Depends on lots of things the high speed wobble,,state of tires,,state of windage,,,,state of flapping front guard,,state of bearings ,,state of forks and oil in them,,state of wheel roundness/balance..True if the bike was lower you may not get as much..Tall bikes get the wobble on at times..part of XRs and there age..Same as old humans,,they get the wobble on as well as they get older.. :lol:

Edited by Horri

One thing that can induce a bit of wobble at high speed is the front mudguard (fender in usa speak?) This flimsy plastic twists one way, then back again. This tuns into an occilation and a front end wobble. 

I took my fender off for a test and did a high speed run and the front end was a lot smoother.

However, putting on USD forks transformed the stablity of the bike 

Check wheel/steering head/swingarm bearings wheels true set sag. On my XR730L with MT21s 122mph onroad no problem!

swing arm bushes caused a twinshock XR500 of mine to wander. Took a while to figure that out.

ALL!!!! above answers are completely wrong!!!! Before I even opened the thread, I figured you probably had an XR. Knobbies on the road have NOTHING to do with it. Doesn't matter if they are DOT or not. That weave is pretty common on XRs.  My XR 250 would weave like a bugger on hard packed gravel roads. On the pavement it was fine at 70mph with dot knobbies. My KTM 525 doesn't have a hint of it on the gravel, or the pavement at any speed, and it's on non DOT rubber. Try dropping your forks in your triple clamps. Have you ever set the sag on your bike? It may be riding too high in the back, and causing too sharp a steering angle. Also make damned sure your wheel bearings are all good, and your rear axle aligned properly

717 has it right - set the sag and drop the forks in the triples - Got mine from a guy that wieghed probally 60lbs more than me - the xr650r had serious head shake starting around 60 mph - you couldn't ride thru it - I set the sag and dropped the forks (top level with the triple) and that cleared up the head shake

Hi guys after full balancing and check of both wheels i found the scary steering to de decreased about 20% i believe i will have to start checking one by one bearings, forks and all my XR650R parts in order to fix this issue. Im a light guy just about 130 pounds, do you think that my lightweight could be a possible cause of it?

 

 

best

do you think that my lightweight could be a possible cause of it?

 

I ride my xr650l on the highway almost daily. I do find that leaning forward slightly, hugging the gas tank and pressing a little down and into the grips keeps the front more stable at higher speeds. I weigh about 175lb. The faster I go, the tighter the tuck and firmer the hold/press down on the grips. Kind of using your arms as a steering damper.

When you accelerate, the front end rises slightly(or the rear slightly lowers, or both). Add to that any lift you may be getting from the wind coming at you. Being light weight, you would probably notice it more.Try to make your bike and yourself as aerodynamic as possible. Definitely have a look at the rims and bearings first. You could even add a few pounds to increase stablity. I've got a pizza and beer diet that works wonders...  ;)

Hi Motoburn, it is just that i used to do the same in my XR250 and i could get to 120 km/h stable without an issue so there could be something wrong with my 650. How fast can you go safely in yours?

Lots of things can cause head shake. It sounds as if most of the bases are covered.

But, go about it systematically. One thing at a time.

Personally I would take the front fender off first. Its a big floppy wind catcher and known to cause steering issues.

As for tires, I ran my mt21 rear and death wing front up to over highway speeds without nary a problem. I have had my mt-90's up to 90 or so without a problem, but I do have the stiffer, more aerodynamic, crf fender on mine.

As for dropping the forks and setting the sag, all good ideas. Understand though dropping the forks and increasing rear sag have the opposite effect (and decreasing rear sag the same as dropping the forks), doing both is just lowering your bike A simple way to test this is to change your seating position while riding. Sit over the tank and see if it gets better or worse, or sit back on the seat and see if help or hurts the situation. If one helps or hurts then that's a good indication of the problem.

Hand guards and windscreens can cause a problem too.

One last thought. Rear wheel alignment can cause weird handling issues. Check to make sure the adjusters are equal at least, better is to truly measure the alignment of the rear wheel.

Bent handlebars can cause strange handling as well. If they are twisted to one side it can cause weird airflow.

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