Front End Wobble on Deceleration?

[skipperT]

FJR’s recommended pressure is 39 psi Front, so 42 isn’t too unreasonable. Others that come to mind are ST1300s, GL1800 wings and Hayabusas. (39-42psi range). 

Like Betoney said, use what works for you. However, I WOULD NOT recommend exceeding the maximum psi listed on the sidewall of the tire!

common theme of all those bikes? Heavy bikes that may “push” a bit while cornering. IMHO..... 

-Skip

Edited August 7, 2019 by skipperT

[chitown]

39 must be something new. My FJR o.m has the typical 36/36 and 36/42 recommendation based on loading. I run 36-40 cold in the FJR depending upon the tire's carcass stiffness. 

I would never recommend anybody start with max pressure from the sidewall but if it's there in writing then you know it's within design parameters and will have some flex. Due to the varied experience of forum readers my suggestion is always start with the manual's recommendation (which is conservative) and experiment +/- in small increments, measure cold vs operating, learn to read tires, find what works for you. 

 

'05 FJR OM:

Edited August 7, 2019 by chitown

[fjrpittsburgh]

Recommended front tire pressure is 36 psi.  The experienced FJR crowd runs 42 to eliminate premature tire scalloping and longer life.  I run 42 psi in the front tires of all my bikes and am pleased with the results.  At 36 psi we found that we were supporting tire manufacturers way too much.  I had my doubts on higher tire pressure also.  I was wrong.  42 psi is just better.  This pressure is measured on a cold tire.

[thejrod]

On 7/30/2019 at 4:39 PM, betoney said:

I completely disagree, I believe it is bike setup.  After reading several members experience, I had to go try for myself today.  I tried at least a dozen times on a level road as well as a downward slope and speeds from 40 to 55mph, maintaining a set speed and then suddenly drop both hands off the bars and coast down to 20-25mph (until I got so slow that I started weaving side to side) and couldn't get it to do anything except decelerate in a straight line. 

No luggage on the bike except a tank bag, no hand guards, aftermarket suspension setup track-side by a suspension tuner, forks raised 5mm in the clamps, half worn tires with 38psi F/R.

You have an FJ though, not a Tracer, if I'm reading your signature correctly... this is a Tracer thread. The chassis was changed a fair amount, and if a slightly worn tire, or pressure off by a mere couple pounds makes that big of a difference in the stability of the bike, then yes I would absolutely say the chassis has a fundamental imbalance to it. But before people get their egos hurt, it's OK - many many bikes have similar imbalances. You have to work around them. 

[duhs10]

3 hours ago, thejrod said:

 You have an FJ though, not a Tracer, if I'm reading your signature correctly... this is a Tracer thread. The chassis was changed a fair amount.

The only change to the chassis was a slightly longer swingarm.  Therefore feedback and advice from FJ owners is relevant. Especially when Tracer owners are reporting the same observations that have been discussed for years.

[betoney]

26 minutes ago, duhs10 said:

The only change to the chassis was a slightly longer swingarm. 

And with the 2" longer swingarm, I would think that the Tracer and GT would be more stable than the shorter wheel based FJ.  Maybe I'm incorrect in my thinking?

[chitown]

24 minutes ago, betoney said:

And with the 2" longer swingarm, I would think that the Tracer and GT would be more stable than the shorter wheel based FJ.  Maybe I'm incorrect in my thinking?

All else being equal, correct. Fwiw rake and trail are the same on the two. 

 

[wordsmith]

1 hour ago, chitown said:

All else being equal, correct. Fwiw rake and trail are the same on the two. 

 

 

1 hour ago, betoney said:

And with the 2" longer swingarm, I would think that the Tracer and GT would be more stable than the shorter wheel based FJ.  Maybe I'm incorrect in my thinking?

The extra stability for touring purposes is what Yamaha has claimed to be the reason behind the extra length.

[thejrod]

2 hours ago, duhs10 said:

The only change to the chassis was a slightly longer swingarm.  Therefore feedback and advice from FJ owners is relevant. Especially when Tracer owners are reporting the same observations that have been discussed for years.

It has different forks and shock too, no? Thought it did - fully adjustable vs only partially...

Regardless, a 2" longer swingarm is a massive change to any chassis. 

[betoney]

2 hours ago, thejrod said:

It has different forks and shock too, no? Thought it did - fully adjustable vs only partially...

The FJ has one "dead" fork leg, no adjustability, spring only.  The new model has hydraulic preload shock adjuster vs manual on the FJ.  Whether the damping and spring rate have been improved or changed is debatable.  In theory, the GT "should" have better suspension up front. 

[duhs10]

3 hours ago, thejrod said:

It has different forks and shock too, no? Thought it did - fully adjustable vs only partially...

Regardless, a 2" longer swingarm is a massive change to any chassis. 

You are correct.

My point is that the 2 bikes are still much much more the same than they are different and experiences of FJ owners are relevant to finding fixes for the Tracer and vice versa.

[wordsmith]

7 hours ago, duhs10 said:

My point is that the 2 bikes are still much much more the same than they are different and experiences of FJ owners are relevant to finding fixes for the Tracer and vice versa.

I find it hard to accept this other than in the broadest sense.   I'd personally be wary of instigating 'fixes' for my GT based on FJR experiences, and vv.   The nearest point of similarity I can find is that both are made by Yamaha.

[duhs10]

1 hour ago, wordsmith said:

I find it hard to accept this other than in the broadest sense.   I'd personally be wary of instigating 'fixes' for my GT based on FJR experiences, and vv.   The nearest point of similarity I can find is that both are made by Yamaha.

FJR and FJ-09 are very different.... I'm comparing the FJ-09/MT-09 Tracer ('15-'17) and Tracer 900/GT ('18-'19). 

[wordsmith]

7 hours ago, duhs10 said:

FJR and FJ-09 are very different.... I'm comparing the FJ-09/MT-09 Tracer ('15-'17) and Tracer 900/GT ('18-'19). 

Precisely - but some of the earlier posts on this refer to the FJR, and I had - wrongly - assumed that this was being carried through in later posts, with the 'FJ' being shorthand for the 'FJR'.   All Yamaha's fault for being so lazy with its model names and designations - too many FJs!!   Thanks...

[2and3cylinders]

On 8/6/2019 at 8:59 PM, betoney said:

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.

OEM specification for the tires for the fjo9 are 36 front 42 rear

There are certain basic laws of physics that must be adhered to with tires despite the Myriad of opinions

Trial and error within a certain range and recording the effects accurately keeping in mind temperature and road conditions is warranted but again interpretation can be subject to opinion  utilizing experience and available empirical data

But again I suspect something other than tire pressure for the instability given the thousands who ride FJ FZ xsr 900 and don't have a problem and don't run higher than 36/42 which supports my supposition

Now there could be a problem with the tire the wheel the brakes the forks the frame swing arm alignment whatever but tire wear and pressure rise based on temperature and road conditions if analyzed properly will likely result in another reason for the instability