Symptom of Bent Forks?
#1
08-19-2010, 02:28 PM
Symptom of Bent Forks?
Hi Everyone,
So i've noticed a slight "wobble" when i'm going about 90km-100km/h on my '09. Is this a symptom of bent forks? (just read that it could be over on ADV) It doesn't seem to do it all the time, but it's more often then i've ever felt before...(well twice now out of riding that fast about 10 times this summer)
I ask because earlier this year i hit a tree off road... but the forks didn't hit. the right handlebar hit and my right fairing hit but not even hard enough to break anything (except a cheap hand guard and a reflector)... i was doing about 15-20 km/h by the time i made contact with the tree.
The only other thing i can attribute it to is that over the past year i've lost about 40lbs going to the Gym (went from 230lbs to 190) and i haven't ridden much this summer... so i'm thinking it could have something to do with that but not too sure...
Having only 4000kms on the bike (my first), i'm still a newb.
any suggestions? the forks sure don't look bent but i'm wondering if there is a way to measure properly just to be sure...
EDIT: on second thought, i guess the fork grazed the tree because the reflector that broke is clamped to the fork... but just the orange part came out of the reflector holder so i can't imagine it hit all that hard (hoping anyway)
So i've noticed a slight "wobble" when i'm going about 90km-100km/h on my '09. Is this a symptom of bent forks? (just read that it could be over on ADV) It doesn't seem to do it all the time, but it's more often then i've ever felt before...(well twice now out of riding that fast about 10 times this summer)
I ask because earlier this year i hit a tree off road... but the forks didn't hit. the right handlebar hit and my right fairing hit but not even hard enough to break anything (except a cheap hand guard and a reflector)... i was doing about 15-20 km/h by the time i made contact with the tree.
The only other thing i can attribute it to is that over the past year i've lost about 40lbs going to the Gym (went from 230lbs to 190) and i haven't ridden much this summer... so i'm thinking it could have something to do with that but not too sure...
Having only 4000kms on the bike (my first), i'm still a newb.
any suggestions? the forks sure don't look bent but i'm wondering if there is a way to measure properly just to be sure...
EDIT: on second thought, i guess the fork grazed the tree because the reflector that broke is clamped to the fork... but just the orange part came out of the reflector holder so i can't imagine it hit all that hard (hoping anyway)
Last edited by higgs; 08-19-2010 at 02:49 PM.
#2
08-19-2010, 03:07 PM
Join Date: Mar 2010
Location: South Puget Sound, WA
Posts: 740
It takes a LOT to bend forks. Are you running stock tires? Is the wobble on straights or in curves or always? I recently acquired a slight wobble but it might be temporary. My 2009 is mostly stock and I weigh 165 all dressed up.
#3
08-19-2010, 03:15 PM
If anything the fork alignment probably just twisted in the triple clamps, not bent. It doesn't take to much of a hit for this to happen with the bottom 1 bolt clamp. ez fix
wheel balance can make a difference too if a weight fell off, or they weren't balanced
wheel balance can make a difference too if a weight fell off, or they weren't balanced
#4
08-19-2010, 03:20 PM
tires are trackmasters, I've only noticed going straight, tire pressure is good.
I'm still reading over on ADV so i'm thinking if anything, my forks are tweaked in the triple clamp. I even have a hard time believing that's the case... but it's tough to tell since my (stock) handlebars are bent in all directions haha - ok, maybe not that bad...
never hit the front end other then this graze with the tree... hmmmm
thanks for the reply!
I'm still reading over on ADV so i'm thinking if anything, my forks are tweaked in the triple clamp. I even have a hard time believing that's the case... but it's tough to tell since my (stock) handlebars are bent in all directions haha - ok, maybe not that bad...
never hit the front end other then this graze with the tree... hmmmm
thanks for the reply!
#5
08-19-2010, 08:00 PM
Probably nothing to do with your forks. Many people report a wobble at higher speeds. Do a search on here you should find some conversations on it. Try holding your bars a little more loosely. Holding tightly will sometimes give you a wobble.
Dan
Dan
#6
08-19-2010, 09:36 PM
Join Date: Apr 2010
Location: In North Western Jersey, but from Jackson, WY Originally
Posts: 278
Lots of reason for high speed wobble, bent forks would be so far down the list for me that I wouldn't even acknowledge it unless I had SERIOUS reason for suspect.. like a straight on with a tree at speeds or being hit by a car.
Other more likely considerations (most of which deal with having your suspension reset for sag and pitch)
1. Did you change tires recently? On my old bike I changed tires and the rear I picked was maybe 1/2" taller due to a thicker tread and since I went with different front and rear it wasn't a matched change. Because of this slight change my bike went from liking good firm pressure to steer at any speed over 20mph and being totally stable up to 95mph (not my klx obviously) to being very neutral in balance all the time to the point it was disconcerting and I was getting headshake over 80Mph. (I like it when my steering wants a reasonably firm press to respond, the way it was I felt like I was balancing and managing the bike all the way through a corner.)
2. You lost weight, this changes your sag and pitch, bikes are VERY sensitive to these shifts. Gain weight, change seat position, or get it adjusted. 2 guys 50lbs different in weight can have a totally different handling experience on the same bike especially if they sit in a different spot on the seat. (did you add any bags you didn't mention? also a weight issue with handling)
3. Your fenders. These bike have big plastic, mud deflecting fenders, which are also somewhat flimsy. They are great for mud deflection and absorbing the occasional impact of a brush with a tree or a lay down on rough ground, but at high speeds they catch the wind, flex, and act a little bit like your hand does out the car window and cause some push with shifts. Sometimes cutting the fender down will help minimize this but it's just the nature of having a high off the wheel plastic fender and cutting it down increases the amount of mud that flings up where it will hit you in the face riding at speeds. I suspect this is why BMW does their lower fork mounted fenders that sit in the same position close over the wheel all the time. Funny looking, but more aerodynamically sound for a bike that's more road intended.
4. Something else is twisted or loose, like your rim having a bend, or your tire not being set straight on the rim, or an axle being set off center, having bad bearings, or your rear sway bar having lateral (side to side).
Good luck sorting it out. Bent forks would be somewhere twice as far down my list of concerns even with a bent handlebar. I suggest starting with having someone help you measure your sag and pitch.
Other more likely considerations (most of which deal with having your suspension reset for sag and pitch)
1. Did you change tires recently? On my old bike I changed tires and the rear I picked was maybe 1/2" taller due to a thicker tread and since I went with different front and rear it wasn't a matched change. Because of this slight change my bike went from liking good firm pressure to steer at any speed over 20mph and being totally stable up to 95mph (not my klx obviously) to being very neutral in balance all the time to the point it was disconcerting and I was getting headshake over 80Mph. (I like it when my steering wants a reasonably firm press to respond, the way it was I felt like I was balancing and managing the bike all the way through a corner.)
2. You lost weight, this changes your sag and pitch, bikes are VERY sensitive to these shifts. Gain weight, change seat position, or get it adjusted. 2 guys 50lbs different in weight can have a totally different handling experience on the same bike especially if they sit in a different spot on the seat. (did you add any bags you didn't mention? also a weight issue with handling)
3. Your fenders. These bike have big plastic, mud deflecting fenders, which are also somewhat flimsy. They are great for mud deflection and absorbing the occasional impact of a brush with a tree or a lay down on rough ground, but at high speeds they catch the wind, flex, and act a little bit like your hand does out the car window and cause some push with shifts. Sometimes cutting the fender down will help minimize this but it's just the nature of having a high off the wheel plastic fender and cutting it down increases the amount of mud that flings up where it will hit you in the face riding at speeds. I suspect this is why BMW does their lower fork mounted fenders that sit in the same position close over the wheel all the time. Funny looking, but more aerodynamically sound for a bike that's more road intended.
4. Something else is twisted or loose, like your rim having a bend, or your tire not being set straight on the rim, or an axle being set off center, having bad bearings, or your rear sway bar having lateral (side to side).
Good luck sorting it out. Bent forks would be somewhere twice as far down my list of concerns even with a bent handlebar. I suggest starting with having someone help you measure your sag and pitch.
#9
08-20-2010, 02:50 AM
Soon after buying my '07 I began to wonder about wobble going 75. Took the advice offered here to lighten up a bit on my grip (which is completely counterintuitive) and discovered that the wobble didn't feel as bad.
Make no mistake, these bikes are not the most stable in the world above 70. Duh! You're on a 270lb windsail with a small road contact patch, arms spread out and the wake from semi's yanking on your MX visor......
The neat part is that it will go 70 all the way to the trail head, and then the fun really starts.
Make no mistake, these bikes are not the most stable in the world above 70. Duh! You're on a 270lb windsail with a small road contact patch, arms spread out and the wake from semi's yanking on your MX visor......
The neat part is that it will go 70 all the way to the trail head, and then the fun really starts.
#10
08-20-2010, 03:25 AM
I've had some headshake under hard power up around the 100 kmh+ mark. Just smile and power on.
The geometry is from the early 90s KX250 so wasn't really designed to run at 100 kmh+. Sure is fun in the woods though and spot on IMHO on tight and flowing single track.
You can drop the forks in the triple clamp (fork top flush with the top triple clamp) to add some stability. Adding some fork preload ("tractor coupling" preload mod) or some heavier fork springs will help too. But if it rarely happens then dropping the forks cold be the solution.
The geometry is from the early 90s KX250 so wasn't really designed to run at 100 kmh+. Sure is fun in the woods though and spot on IMHO on tight and flowing single track. You can drop the forks in the triple clamp (fork top flush with the top triple clamp) to add some stability. Adding some fork preload ("tractor coupling" preload mod) or some heavier fork springs will help too. But if it rarely happens then dropping the forks cold be the solution.
