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Front End Wobble on Deceleration?


RichNDC

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This is me: I can feel the bike settle a bit when I roll off the gas, same feeling when I get on the gas- I can feel the bike trying to pick itself up... This is on stock suspension... 

A Giraffe is slightly faster than a rabbit- I kinda relate the FJ-09 to a giraffe- yea it's "legs" are a bit wobbly but it moves 🙃

2012 wr250f - C-class 30+ age group
2015 fz-07- Hordpower Edition-80whp
2015 fj-09- Graves Exhaust w/Woolich tune by 2WDW @120whp
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4 hours ago, BBB said:

42 psi up front is waaayyyyy too high, that’s  a rear pressure.  Original manual says 36, but I run 33.

I have no idea how long you've been riding, but all 4 of my bikes for the last 20 years have been at 42 psi for the front tire.  I used to run mid 30's psi like the manual says years ago.  I learned from experienced riders long ago that those lower pressures will cause your front tire to scallop more quickly.  You can certainly run whatever tire pressure you like on your bike and that's fine.  It's your money.  Your claim that 42 psi is way too high is fake news.  😀  Your manual says 36 and you run 33?  LOL

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4 hours ago, Clicknow said:

I must say iam not happy about this,are there some GT owners that do NOT have this wobble?

regards graham 

Graham, my bike doesn't have this particular wobble you and others speak of; neither does my bike have a top box nor even a rack. Ain't gonna be putting them on this bike. I like to ride fast and this is a light bike, particularly in the front end, with a very responsive chassis. At freeway speeds (at least out here in the Western US 😁) just loaded side cases is enough to get a pretty good wobble going during high speed passes; I can only imagine a top case would add to the excitement ( not that it's dangerous or anything like that unless you start trying to muscle the bike out of it,eh).

I have  one of those lunch box sized coolers that I use on trips- first time I used it, I stood it tall way up on my passenger seat with some space between it and my rear. Running down the freeway, I could feel this mild Pulse, for lack of a better word, running through the chassis, mild, nothing to disturb the handling, but noticeable to me. Stopped to take a break and I look at the cooler and figure that has to be it, turned on it's side and and up against me. No more pulse. I carried bigger coolers the same on my cruisers in the past and never felt that kind of thing.

 

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With my Yamaha stock side cases and a Givi top case high up on the back, I don't even notice that they're there.  Then again, the Givi top case is much more aerodynamic than a cooler.  I have side cases and a top case on all 4 of my bikes.  3 of us in the family ride and we do a lot of long distance touring.  I can't say that I ever take my hand off of the bars as there's no reason to.  Some of that Givi stuff is pricey, but worth every penny of it.

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No one has mentioned front wheel balance.  Do you know for a fact that the wheel--tire combo is in good balance?  

With the FJ's light steering it doesn't take much imbalance to induce shake.

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1968 Triumph Bonneville 650
1971 Norton Commando Roadster
2002 Harley 1200 Sportster
2003 Honda ST 1300
2016 FJ 09
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@fjrpittsburghyeah, can't go wrong with Givi- though yer gonna pay for it. And yes, I agree this bike really responds to aerodynamics, or the lack there of, whether it be windshields, top boxes or even coolers. Nonetheless, my friend, I'd be pretty damn surprised if your bike didn't "wobble" while executing a triple digit pass around a semi.

Edited by Larz
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6 hours ago, fjrpittsburgh said:

I have no idea how long you've been riding, but all 4 of my bikes for the last 20 years have been at 42 psi for the front tire.  I used to run mid 30's psi like the manual says years ago.  I learned from experienced riders long ago that those lower pressures will cause your front tire to scallop more quickly.  You can certainly run whatever tire pressure you like on your bike and that's fine.  It's your money.  Your claim that 42 psi is way too high is fake news.  😀  Your manual says 36 and you run 33?  LOL

No problem with me. I was just worried you’d mixed rear and front pressures. 👍🏻

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Red 2015 Tracer, UK spec (well, it was until I started messing with it...)

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On 8/1/2019 at 5:59 PM, fjrpittsburgh said:

I have no idea how long you've been riding, but all 4 of my bikes for the last 20 years have been at 42 psi for the front tire.  I used to run mid 30's psi like the manual says years ago.  I learned from experienced riders long ago that those lower pressures will cause your front tire to scallop more quickly.  You can certainly run whatever tire pressure you like on your bike and that's fine.  It's your money.  Your claim that 42 psi is way too high is fake news.  😀  Your manual says 36 and you run 33?  LOL

Yeah, 42 is pretty high for a front tire. Riding at 42psi for a very long time over multiple bikes still doesn't make it any more right. :)

A higher pressure prevents the carcass from flexing as designed, which reduces grip and warm-up time. But yes, you might get better mileage out of the tire, so there's that. I err on the side of performance, personally. I usually run low-30s, even 30psi in the winter. I did get cupping on my PR4s (on my previous FZ09), but they also lasted about 20,000 mi at these pressures.

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20 minutes ago, thejrod said:

Yeah, 42 is pretty high for a front tire. Riding at 42psi for a very long time over multiple bikes still doesn't make it any more right. :)

A higher pressure prevents the carcass from flexing as designed, which reduces grip and warm-up time. But yes, you might get better mileage out of the tire, so there's that. I err on the side of performance, personally. I usually run low-30s, even 30psi in the winter. I did get cupping on my PR4s (on my previous FZ09), but they also lasted about 20,000 mi at these pressures.

Actually it would increase warm up time. No, it doesn't prevent the carcass from flexing as designed... you're not even close to that until you exceed the tire's ratings. Will it flex, yes. As much? No. But, unless you're going to post cold and operating temp pressures there's nothing objective about these statements. Even then folks will debate what an acceptable range is because it's subjective. Running 30 on the street would not work for me. The sidewall would not maintain stiffness. Ymmv.

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4 minutes ago, chitown said:

Actually it would increase warm up time. No, it doesn't prevent the carcass from flexing as designed... you're not even close to that until you exceed the tire's ratings. Unless you're going to post cold and operating temp pressures there's nothing objective about these statements. Even then folks will debate what an acceptable range is because it's subjective. Running 30 on the street would not work for me. The sidewall would not maintain stiffness. Ymmv.

Based on what? Ideally you want about a 4psi increase from cold to hot pressures, but that's running at pace. On the street, it absolutely will hurt your warm-up by running too high a pressure (I phrased that incorrectly above). You're absolutely wrong about the carcass flex - pressure plays a very important role in how the carcass performs, and you contradict yourself in the last sentence. 

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5 minutes ago, thejrod said:

Based on what? Ideally you want about a 4psi increase from cold to hot pressures, but that's running at pace. On the street, it absolutely will hurt your warm-up by running too high a pressure (I phrased that incorrectly above). You're absolutely wrong about the carcass flex - pressure plays a very important role in how the carcass performs, and you contradict yourself in the last sentence. 

Ideally I want a certain percentage difference, not an absolute. But again that is completely subjective and I can show you folks that suggest a range of numbers. Yes, flex will change. You asserted "as designed" and I'm asserting unless you've exceeded the tires ratings you're well within what the engineers designed for. It may not be the flex you desire but saying it's not as designed? What's it designed for? Can you get Michelin to tell you... probably not but you can likely get a Michelin tech at a track day to give you very specific pressure recommendations based on the conditions. 

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TIRES

36 or lower is ok, I never run over that.  tire pressure is temp dependent, +10% from cold 70F

Scalloping is not always evident, internal belt damage, out of round, balance, my front wheel is a BITCH to balance and takes over an ounce not matter what tire.

OTHER

Over or under tensioned steering head bearings; must follow procedure with fish scale and have feel for it.

Do not raise tubes, that increases rake and decreases trail + less high speed stability but loads tire for better turn-in.

F/R alignment

Rotors warped/bent; hard spots & pad build-up causes causes pulsing under braking

I HAVE NOT HAD ANY WOBBLE ISSUES IN 30K MILES ON MY FASTEST RED 15...

 

 

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Thanks for the honesty @chitown.  42 psi in the front tire works incredibly well for me and has for many years.  Everyone I know on the FJR Forum which includes literally thousands of riders from all over the world do the same since it's a proven tire pressure.  To each their own.  I ride more than many.  Definitely a rider and not a poser.  I also own an FZ-07 and a Honda CTX 700 DCT.  Same tire pressure among all bikes.  It just works.  With an FJR, a GT, and an FZ-07 in the stable, we ride a lot of hard, fast miles.

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2 hours ago, fjrpittsburgh said:

42 psi in the front tire works incredibly well for me and has for many years.  Everyone I know on the FJR Forum which includes literally thousands of riders from all over the world do the same since it's a proven tire pressure.  To each their own.

The important thing is finding something that works for you and sticking with it, the internet can give you thousands of different ideas and opinions and even possibly make you start to doubt your decisions.  Go with what you know.

To be fair though, I'm with everyone else on here that has chimed in, I have NEVER heard of anyone actually using 42psi in the rear, and definitely not in the front.  But like I said, if it works for you and the bike isn't behaving oddly because of it, don't change from what works for YOU.

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***2015 Candy Red FJ-09***

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