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Old 11-14-2013, 06:44 AM   #12121
poondangle
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suspension gurus

OK suspension people, I need your help. I have a 13. With my riding style and ability, the stock set up worked great. I could make minor adjustments through the range and I was perfectly happy, except for the stock MT21s. So, I put a Pirelli Rally up front, changing to UHD tubes at the same time, and an XCMH on the rear, again with new UHD tube. I changed nothing else. I immediately got a head shake like there was no tomorrow at 60+ MPH. I was away from home when all this happened. I went all the up on the compression and all the way down on the rebound up front, and added maxed rebound out back. I adjusted pressures down to 16 since I'd be offroad. I rode the bike the next day and the headshake was gone. I subsequently that crashed that day (nothing to do with headshake) and haven't been able to ride until last weekend. So, against the better medical advice of my doctor, surgeon, and most importantly, my wife, I pump the tires back up for some pavement riding and off I went. The headshake is back with a vengeance! What do I do next? What am I missing here?
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Old 11-14-2013, 07:06 AM   #12122
dad2bike
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I run XCMH front/rear. I also balance my wheels. No headshake issues.
I suggest balancing your wheels. Both of them.
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Old 11-14-2013, 07:13 AM   #12123
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Originally Posted by dad2bike View Post
I run XCMH front/rear. I also balance my wheels. No headshake issues.
I suggest balancing your wheels. Both of them.
I hate to disagree with you, and I certainly don't want to come across as an a-hole arguing about free advice, but I know deep down in my heart, headshake is not a balance issue, its a geometry issue. I've never balanced a knobby in my life, and I've never had this problem. The bike didn't come with balanced wheels/tires?

I'd drop the forks in the clamps, but honestly, there isn't much room to play with?
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Old 11-14-2013, 07:22 AM   #12124
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Quote:
Originally Posted by poondangle View Post
I hate to disagree with you, and I certainly don't want to come across as an a-hole arguing about free advice, but I know deep down in my heart, headshake is not a balance issue, its a geometry issue. I've never balanced a knobby in my life, and I've never had this problem. The bike didn't come with balanced wheels/tires?

I'd drop the forks in the clamps, but honestly, there isn't much room to play with?
head shake can come from tire selection. I balance my tires when I run road tires and I might put some weights on if I am running rim locks to help take some of the extreme weight bias out of the wheel.

I have bought brand new tires before that were a bad molding and caused significant problems...to the point they were sent back in favor of a new one.


but yes a tire choice can cause or contribute to headshake. I would start by playing with your tire pressure because it is cheap, fast, and easy to do. See if raising or lowering the front/rear pressures causes any change in your head shake problem. Next I would set your front and rear sag.
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Old 11-14-2013, 07:29 AM   #12125
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Quote:
Originally Posted by Seth S View Post
head shake can come from tire selection. I balance my tires when I run road tires and I might put some weights on if I am running rim locks to help take some of the extreme weight bias out of the wheel.

I have bought brand new tires before that were a bad molding and caused significant problems...to the point they were sent back in favor of a new one.


but yes a tire choice can cause or contribute to headshake. I would start by playing with your tire pressure because it is cheap, fast, and easy to do. See if raising or lowering the front/rear pressures causes any change in your head shake problem. Next I would set your front and rear sag.
I'm happy to hear you say that. I've had a sneaky feeling I might have gotten a bad tire. I'm just to cheap to throw away a tire with only 100 miles on it. But I think I might order a new one, and if the problem goes away, then I'll toss the used one. If the problem persists, then I keep tuning the suspension and I have a spare.
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Old 11-14-2013, 07:44 AM   #12126
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Feel free to ship your "bad" tires to me. I'll run them just fine.
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Old 11-14-2013, 07:51 AM   #12127
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Originally Posted by sprouty115 View Post
Yes. When static sag is set properly I have approximately 2 or 3 times the required sag when I sit on the bike. And when I set the loaded sag correctly, I have no static sag at all. Spring is wrong for my weight.
'yer doin' the right stuff, boss.... when you get the right springs/sag geometry, it's probably less than a turn of the collar, 1mm differences, and the handling changes will be very apparent....

i got my spring info from the racetech website, and from brucessuspension.com.... i don't think bruce's has info for the big bikes, the racetech site probably has some recomendations for your bike, but they spec a variable rate spring sometimes, i dunno about your bike, though...i think you have a linkage?.... . you gotta find some trustworthy sources for what kinda rate you need for what kinda weight, and there's alotta blah-blah out there, so the mileage may vary....

that spring rate sets up the chassis geometry, and what it does to the front end when you're ridin'..... the rear end controls the front end to a great degree.... and for me, i've figured alotta handling issues out by ridin' w/a wrench and a screwdriver, and make some changes and see what happens.... too high of a rear end will turn too fast, and too low won't turn for shizzit, so... make fairly big changes so you fukk it up and see what that direction does, and then adjust from there....

guys are complaining of headshake, and if the rear sag is whacked, that is definitely not gonna help........ everytime that rear wheel/shock gets compressed, it changes the front rake and especially the trail... which makes things interesting, to say the least....

i don't think there's a way to get this figured out w/out some experimentation.... but springs are huge, i know that....
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Old 11-14-2013, 08:11 AM   #12128
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Originally Posted by dad2bike View Post
Feel free to ship your "bad" tires to me. I'll run them just fine.

its yours!
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Old 11-14-2013, 08:27 AM   #12129
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Quote:
Originally Posted by poondangle View Post
I'm happy to hear you say that. I've had a sneaky feeling I might have gotten a bad tire. I'm just to cheap to throw away a tire with only 100 miles on it. But I think I might order a new one, and if the problem goes away, then I'll toss the used one. If the problem persists, then I keep tuning the suspension and I have a spare.
You'd order a new $100 tire, before you'd spend $5 balancing it? Really not trying to pick on you, but that makes no sense to me.
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Old 11-14-2013, 09:19 AM   #12130
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Quote:
Originally Posted by dad2bike View Post
Feel free to ship your "bad" tires to me. I'll run them just fine.
doubtful. I bought a set of Pirelli road tires for the 690 a while ago to run Rally Tennessee. I had my local shop install and balance them and i went for a test ride. At 70 mph the vibration was so bad I had a hard time seeing the road and it was getting difficult to hold onto the bars. I came back and indicated the balance was way off...I then tried balancing them myself...got the balance perfect and went for a second test ride. Same problem. We sent the set back and got a new one.
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Old 11-14-2013, 09:20 AM   #12131
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Quote:
Originally Posted by sprouty115 View Post
You'd order a new $100 tire, before you'd spend $5 balancing it? Really not trying to pick on you, but that makes no sense to me.
There is really no point in balancing an offroad tire as you just don't ever notice the imbalance when riding off road. For a road tire it makes sense to balance.
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Old 11-14-2013, 09:21 AM   #12132
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Quote:
Originally Posted by poondangle View Post
I hate to disagree with you, and I certainly don't want to come across as an a-hole arguing about free advice, but I know deep down in my heart, headshake is not a balance issue, its a geometry issue. I've never balanced a knobby in my life, and I've never had this problem. The bike didn't come with balanced wheels/tires?

I'd drop the forks in the clamps, but honestly, there isn't much room to play with?
Yup, the 690 is a supermoto converted into a dual sport. That being said, you can get rid of the headshake by getting your suspension tweaked. It's how I got rid of mine and I never changed the ride height front or back.
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Old 11-14-2013, 10:11 AM   #12133
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Where'd you order the 110?

MM,
I phoned Superplush, told them how fat I was and the general style of use and weight carried, and the guy told me that the 110 was likely the right spring. I then went to my local suspension guy( Kamloops, BC), told him the story and ordered it through him....I will ask where he ordered it from. You are in the USA....call the Superplush guy as he could probably get a spring to you quicker.....

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Old 11-14-2013, 10:15 AM   #12134
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Quote:
Originally Posted by Seth S View Post
doubtful. I bought a set of Pirelli road tires for the 690 a while ago to run Rally Tennessee. I had my local shop install and balance them and i went for a test ride. At 70 mph the vibration was so bad I had a hard time seeing the road and it was getting difficult to hold onto the bars. I came back and indicated the balance was way off...I then tried balancing them myself...got the balance perfect and went for a second test ride. Same problem. We sent the set back and got a new one.
You are welcome to send me your new take offs as well.

Quote:
Originally Posted by Seth S View Post
There is really no point in balancing an offroad tire as you just don't ever notice the imbalance when riding off road. For a road tire it makes sense to balance.
In our area we have a 25-30 mile pavement ride to get to the dirt. Hence the balancing of my dirt tires. With our rocky terraine I run Rimlocks. That itself introduces quite an imbalance. Before I started balancing I could feel and see the oscillations when on the pavement. Balancing costs me next to nothing. I bought the stand at Harbor Freight for $40 and a box of weights for about $25. That will get me through many many tires.
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Old 11-14-2013, 10:30 AM   #12135
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When I ride on pavement I notice whether or not a tire is in balance. I love MotoZ HT for the rear, but my last one was "out of round" (molding flaw most likely w/ a high point undetectable to the eye)....it was very difficult to balance....no fun on pavement and no problem off hard surfaces.

I have never had headshake on the 690 (sag never set, but suspension tuned aside from that) under any conditions....but the unbalanced tire will set up a high-frequency "bumping" with the imperfect circumference/imbalance. These are two different conditions: headshake vs "hopping/bumping".

And just because a bike doesn't have wheels balanced out of the showroom certainly does NOT mean tires don't need balancing. Most tires today are very close to being "balanced" before installation on a rim as production facilities are better ...but some are not (red dot issue).

I have balanced each rim without tires on them (weights under rim strip), so every tire mounting. I check the balance....if it needs weight, I know the tire is not balanced.

That Motoz I had that hopped is 1/3 used and off the bike....a shame because I like to wear them down as much as I can before my friends make fun of me. I am donating a half-dozen half-used front and back tires to an off-road group in Mulege, Baja when I go down next month....these tires are the ones that I have kept for a few years thinking I would remount them in a pinch....and never had.
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