70-80 MPH and over fish tail feeling

[not2shabby]

It has me stumped. My old "73"Kawa Z900 went straight, My "84" Kawa went straight, my Goldwings went straight but they all just handled bad in twisties.

I have cruised at 120mph with this FJR before at 2400 miles on odometer w/original tires and it went straight. I remember it starting fishtailing at about 5000 when the tire was getting flat across the middle. It must be the new Contis.

I will try 40 psi Frt.- 42 psi Rr then, I hope that works, If not, back to Bridgestones.

Thanks all for all the advice. I'll let you know.

When did you install the lowering links?

 

[Ronny]

If you didn't lower the front end too, this could be the problem. I'd try sliding the fork tubes up in the tripples about 5mm and go for a test ride.

Thanks not2, that's where I was going with that comment. Lowering the rear alone changes the steering geometry and makes the bike slightly more unstable.

There are many good tires besides the OEM tire. Do a search on tires, you should find a life time of reading :lol:

I had heard that if you lower the rear that the front should also be lowered. I went with higher air pressure in the front and lowered the tubes 5mm as suggested. I will try it out tomorrow and let you know.

Thank You, Ron

 

[Ronny]

I hate to contradict my friend and mentor Professor ionbeam, but while lowering the rear end will alter the steering angles, that change will actually improve the straight line stability (at the cost of slower steering) . I don't think that the lowering links would be the cause of his wobbling woes unless it also did something negatively to the aerodynamics.

Of course, I could be wrong. It has happened a time or two before.

And to the OP, yeah, 36 is way too low for the front tire. 40 should work fine as long as you haven't already cupped the front due to the low pressure.

Also, you didn't mention, what windshield are you running?

I did go with a taller windshield, I think probably about 2 inches taller. It is made by Yamaha windshield.

 

[Ronny]

It has me stumped. My old "73"Kawa Z900 went straight, My "84" Kawa went straight, my Goldwings went straight but they all just handled bad in twisties.

I have cruised at 120mph with this FJR before at 2400 miles on odometer w/original tires and it went straight. I remember it starting fishtailing at about 5000 when the tire was getting flat across the middle. It must be the new Contis.

I will try 40 psi Frt.- 42 psi Rr then, I hope that works, If not, back to Bridgestones.

Thanks all for all the advice. I'll let you know.

When did you install the lowering links?

I believe around 4000 miles.

 

[RadioHowie]

If you didn't lower the front end too, this could be the problem. I'd try sliding the fork tubes up in the tripples about 5mm and go for a test ride.

Thanks not2, that's where I was going with that comment. Lowering the rear alone changes the steering geometry and makes the bike slightly more unstable.

There are many good tires besides the OEM tire. Do a search on tires, you should find a life time of reading :lol:

I had heard that if you lower the rear that the front should also be lowered. I went with higher air pressure in the front and lowered the tubes 5mm as suggested. I will try it out tomorrow and let you know.

Thank You, Ron

Just out of curiosity, when you say you lowered the tubes by 5mm to match the lowered rear end, did you actually lower the fork tubes in the triple clamp? Or did you lower the triple clamp on the fork tubes?

Ideally, you should RAISE the fork tubes in the triple clamps to match the lowering of the rear. I know it sounds counter-intuitive, but raising the tubes in the clamps lowers the bike in the front to match the lowering in the rear.

 

[Bustanut joker]

If you didn't lower the front end too, this could be the problem. I'd try sliding the fork tubes up in the tripples about 5mm and go for a test ride.

Thanks not2, that's where I was going with that comment. Lowering the rear alone changes the steering geometry and makes the bike slightly more unstable.

There are many good tires besides the OEM tire. Do a search on tires, you should find a life time of reading :lol:

I had heard that if you lower the rear that the front should also be lowered. I went with higher air pressure in the front and lowered the tubes 5mm as suggested. I will try it out tomorrow and let you know.

Thank You, Ron

Just out of curiosity, when you say you lowered the tubes by 5mm to match the lowered rear end, did you actually lower the fork tubes in the triple clamp? Or did you lower the triple clamp on the fork tubes?

Ideally, you should RAISE the fork tubes in the triple clamps to match the lowering of the rear. I know it sounds counter-intuitive, but raising the tubes in the clamps lowers the bike in the front to match the lowering in the rear.

Feckin brilliant puddin'head! Remind me to put you in for a rare forum Gold Star!

:****:

 

[Ronny]

If you didn't lower the front end too, this could be the problem. I'd try sliding the fork tubes up in the tripples about 5mm and go for a test ride.

Thanks not2, that's where I was going with that comment. Lowering the rear alone changes the steering geometry and makes the bike slightly more unstable.

There are many good tires besides the OEM tire. Do a search on tires, you should find a life time of reading :lol:

I had heard that if you lower the rear that the front should also be lowered. I went with higher air pressure in the front and lowered the tubes 5mm as suggested. I will try it out tomorrow and let you know.

Thank You, Ron

Just out of curiosity, when you say you lowered the tubes by 5mm to match the lowered rear end, did you actually lower the fork tubes in the triple clamp? Or did you lower the triple clamp on the fork tubes?

Ideally, you should RAISE the fork tubes in the triple clamps to match the lowering of the rear. I know it sounds counter-intuitive, but raising the tubes in the clamps lowers the bike in the front to match the lowering in the rear.

The fork tubes/caps are the same then, the triple trees are 5mm closer to the ground. I just did this and haven't tested yet. Thank you, Ron

 

[Fred W]

Unfortunately, you've made the cardinal sin of logical troubleshooting. You made two changes at once.

So if your wobbling woes should suddenly no longer be present you won't know if was the steering angle changes or the higher air pressure in the tire that fixed it. I suppose you could just go back one step and lower your tire pressure again and see if it comes back. Or just ride on and be happy...

 

[Ronny]

Unfortunately, you've made the cardinal sin of logical troubleshooting. You made two changes at once.

So if your wobbling woes should suddenly no longer be present you won't know if was the steering angle changes or the higher air pressure in the tire that fixed it. I suppose you could just go back one step and lower your tire pressure again and see if it comes back. Or just ride on and be happy...

I know, but apprently everything that I did should have been done anyway. I just hope it improves the handling without buying new tires.

Thanks For your help.

 

[not2shabby]

So...have you done a test ride yet?

 

[TwoWhldTerror]

As mentioned do check the tire pressures with a known accurate gauge because a low rear tire acts much like what you describe.

How does an average garage mechanic know if a gauge is "accurate"? I do not have a test station and I have to trust the darn tool. How do ya'll check for "accuracy" of your gauge?

 

[RadioHowie]

Darn good question...when is a pound REALLY a pound, or a gallon REALLY a gallon????

 

[Fred W]

As mentioned do check the tire pressures with a known accurate gauge because a low rear tire acts much like what you describe.

How does an average garage mechanic know if a gauge is "accurate"? I do not have a test station and I have to trust the darn tool. How do ya'll check for "accuracy" of your gauge?

Calibration. - All calibration is just the comparing of measurement results from the instrument in question to a known good instrument. If you don't have a known good instrument you can compare several instruments of unknown accuracy and determine the statistic average of these instruments. The only problem with that technique is it takes a large number of sample instruments to determine a reasonably accurate mean, and identify which (if any) are inaccurate outliers.

Or you can just buy an expensive new gauge and hope for the best.

Darn good question...when is a pound REALLY a pound, or a gallon REALLY a gallon????

Which pound (there are a whole bunch of different ones) and which gallon?

 

[ionbeam]

You can improve your odds of having an accurate gauge in several ways. First is to buy a quality bourdon tube gauge with bronze and brass movements. The bourdon tube type of gauge is not affected by humidity, altitude or temperature. This is a representative gauge without brand recommendation. It also has an optional rubber protection ring around the gauge.

Buy a gauge with a 1-1/2 to 2-1/2 diameter or larger, this gives the scale good resolution.

Buy a gauge with an appropriate range. A 0-160 psi gauge is not a good range, look for 0-60 psi scale. The heart of the scale is where it will be most accurate. Most dial gauges will have best accuracy from 25% to 75% of the scale and less accuracy outside this range. A major brand of dial gauges offers this accuracy: A 60 psi tire gauge is accurate to +/- 1.2 psi from 15 to 45 psi and is calibrated to ± 1 psi at 30 psi For home use this is about as good as it gets.

Pencil gauges are sensitive to environmental conditions which can cause a ~15% reading variation from 30°F to 100°F, plus altitude can make this error even greater.

The approximation method that Fred offers is actually good advice. Over the years I have accumulated a large collection of gauges which have quite a range of readings for the same tire. I did have two gauges that read almost the same and were centered in the range that the other gauges produced so I declared these two gauges to be my standard tools. For car racing I bought a high quality, calibrated dial type gauge and I was able to have a lab confirm the accuracy. It turned out to agree with my old 'standard' gauges.

 

[RaYzerman19]

I have managed to amass a collection of electronic gauges (AccuTire mainly), and have a TPM system. They all agree very closely, and have shown me the dial and pencil types have far more variation. I bought a nice one like Alan describes and it was very inaccurate, lab grade recommended and probably too expensive. Electronic is the way to go now IMHO.

 

[FJRBluesman]

Waiting for OP's response to the test ride.

That being said, 36psi is not that low. Higher psi does help with wear/cupping, but this should not wobble at 36psi.

If the bike has done it before, I'd say he has other issues, and the new tires made it worse (blems maybe?). Usually tires do better on asphalt (smoother) than concrete. The rain grooves, etc on concrete roads is nasty. So that also puzzles me (very easy to do).

One other thing I don't recall reading was balancing of the tires. Get them re-balanced if the other things don't work. Some bone head wrench in a hurry may have just quickly slapped on the weights without taking the time to do it right. You weren't that bone head were you?

Good luck let us know what's going on.

 

[Ronny]

Waiting for OP's response to the test ride.

That being said, 36psi is not that low. Higher psi does help with wear/cupping, but this should not wobble at 36psi.

If the bike has done it before, I'd say he has other issues, and the new tires made it worse (blems maybe?). Usually tires do better on asphalt (smoother) than concrete. The rain grooves, etc on concrete roads is nasty. So that also puzzles me (very easy to do).

One other thing I don't recall reading was balancing of the tires. Get them re-balanced if the other things don't work. Some bone head wrench in a hurry may have just quickly slapped on the weights without taking the time to do it right. You weren't that bone head were you?

Good luck let us know what's going on.

The tires were mounted by a very well known tire store. Rain grooves were not on this streach of road. We have a mix of pavement here in Ohio on highways. I noticed that I went from Asphalt (wobbling) to concrete and it seemed to go straight while I was on the concrete. I will evaluate this morning hopefully (raining currently) and report.

BTW, I am a veteran mechanic from the "60's-80's" then Toolmaker to now. I was actually curious as to if there bikes are actually that finicky to a twitch in setup.

I have several guages with a digital Accutire being my favorite.

 

[Fred W]

That being said, 36psi is not that low. Higher psi does help with wear/cupping, but this should not wobble at 36psi.

My thoughts on lower pressures (like 36 psi) are that tires will wear and cup much faster at the elevated temperatures caused by under inflation. Once cupped the tire can cause high speed weaving. Even though it has pretty low miles on it, it may already be too late for this front tire.

So if during the next test phase neither the higher tire pressure nor lowering of the front end changes the symptoms, the next step would be to try a different tire and not run it at a lower pressure.

I was actually curious as to if there bikes are actually that finicky to a twitch in setup.

No. Generally, not. These are pretty rock solid, stable bikes at just about any speed they are capable of.

 

[Ronny]

That being said, 36psi is not that low. Higher psi does help with wear/cupping, but this should not wobble at 36psi.

My thoughts on lower pressures (like 36 psi) are that tires will wear and cup much faster at the elevated temperatures caused by under inflation. Once cupped the tire can cause high speed weaving. Even though it has pretty low miles on it, it may already be too late for this front tire.

So if during the next test phase neither the higher tire pressure nor lowering of the front end changes the symptoms, the next step would be to try a different tire and not run it at a lower pressure.

I was actually curious as to if there bikes are actually that finicky to a twitch in setup.

No. Generally, not. These are pretty rock solid, stable bikes at just about any speed they are capable of.

I replaced the tires as a set. The Bridgestone was cupped badly to warrant replacement of it also. I seem to recall the bike starting to do the fishtailing one day comming from work. It was so slight I didn't know if I was imagining it. It did it a little more again so I thought it maybe the worn spot on the rear. That is why I replaced them. Normally I don't ride too much except at low speeds as a bicycle referee in road races. So I didn't pick up on this problem right away. When I did hit the highway, it was very apparent. I did some inspection, like the front headset, I retorqued it and checked everything else. I also checked all the engine mount bolts since the engine is essentially part of the frame. I only found 1 bolt a little loose.

So what is the concensus of the best tire for these bikes? I sort of thought it was the Conti's Assult 2, which is what I got for it.

This bike is almost like new with a little more than 7000 miles on it. Never down.

 

[donaldb]

.......So what is the concensus of the best tire for these bikes? I sort of thought it was the Conti's Assult 2, which is what I got for it.

This bike is almost like new with a little more than 7000 miles on it. Never down.

Oh Lord...........

you just committed the biggest of cardinal sins. Some serious repent is now in order