Wheel Balance

[737Captain]

My ST has been standing for awhile, 9 months or so, I took it out a couple of days ago and noticed at 25-35 mph I get a "verticle" oscillation. It feels like I would imagine a flat spot would feel, popular belief is that a bike isn't heavy enough to create a flat spot. What does "out of balance" feel like? How does it manifest itself?

Thanks

Tony

 

[Mellow]

What tires do you have? Yes, a vertical bounce is typically how it would feel but my new Roadsmart front tire did that a few years ago and it was a bad tire.

 

[v8-7]

If you want to take a ride, I have a balancer and weights .

Or you can pick up a balancer at harbor freight .

 

[dduelin]

Tires are constructed to support the weight of the vehicle they are rated for........a tire for a Boeing 737 wouldn't flat spot under the weight of a ST1300 but a motorcycle tire can certainly flat spot if left in one place for a long time. However I would expect the flat spot or resultant oscillation to go away when the tire heats up in the first good ride after layup. Out of balance can manifest itself in vibration or "hop" that gets worse as speed increases. It may be felt through the seat or handlebars or seen when a GPS mount or mirror resonants. I have cars that the vibration came and went in a rhythm as different tire's vibrations passed in and out of synch at highway speeds. Tires can and do go out of balance over the life of the tire but they don't when parked. How was the tire balance when you were last riding the ST1300?

 

[737Captain]

Thanks Joe, I don't remember off the top of my head but they have been fine in the past. I installed pressure sensing caps which are heavier so I'm betting that's what it is.

Stan, if I have time next week I'll run down. I'll PM you. Thanks.

 

[CYYJ]

I installed pressure sensing caps which are heavier so I'm betting that's what it is.

Tony:

I would discount pressure sensing valve caps as the most probable source of the vibration, that is based on my own recent experience. I had a set of new tires installed on my ST 1300 at the beginning of November. I rode 1,000 miles on them and noted that there were no balance problems. I then installed Garmin TPMS sensors and rode another 6,000 miles. I was concerned that these little caps might affect wheel balance, but I did not notice any symptoms of poor wheel balance, and over 90% of my riding was done at high speeds (70 MPH or more).

If you installed metal valve stems at the same time you installed the pressure sensors, the additional weight of the metal stems 'might' be sufficient to cause your balance problems. If you did not install metal valve stems - in other words, if you are running on rubber valve stems with the TPMS sensors installed - that is a dangerous configuration, because the added weight of the sensor will deform the rubber stem at speed and may result in a sudden loss of tire pressure. Plus, the TPMS won't work well, because the sensors use the metal valve stem as an antenna, a function that a rubber stem won't provide.

My guess is that the combination of cool winter weather and a long lay-up has resulted in your tires taking a 'set' - developing sort of a flat spot - as Dave suggested in post #4 above. You could rule that out by taking the bike out for an 'Italian Tune-Up' - going for a ride of half an hour or more at fairly high speed on a nearby expressway. That should be sufficient to warm the rubber up and flex it sufficiently to get things back to normal.

A final thought - you have probably checked this already, but: Tire pressure will decrease as OAT decreases, even if the tire is perfectly sealed. If you checked the pressures during the summer and they were correct, they are likely below spec now, and that could contribute to the problem by causing excessive flex during operation.

Michael

 

[st1300r]

If it really did flat spot (assuming it wasn't on the center stand?) I could see a bit of compression set in the rubber. How low were they when you topped them off before getting back on?
I'd ride it a bit 1st and hope some heat cycles helped get it round before checking the balance. An out or round balanced tire is still gonna feel weird.

If you mean TPMS screw on sensors that might effect balance and I'd want metal valve stems to go with them.
If they're the color indicating screw on caps I'd chuck em and put metal caps with an o-ring on. Doubt they would have any noticeable balance impact.
Either way easy enough to put conventional caps on go for a ride and see if it feels different.

 

[737Captain]

Great information as always from you guys, thank you.

I think they were about 28psi before I topped them off preride. I love the idea of an "Italian Tune-Up"!!!!

I bought the caps that have a colored end that are preset to the required pressure and at the set point are green on the end, as the pressure reduces they turn yellow then red. The idea of breaking off a stem is enough for me to change them as soon as I get home from my trip then do the "Italian Job" with OEM plastic caps.

I'll let you know what transpires.

 

[st1300r]

I think the wisdom of an italian tune up was multiple runs up to red line snapping the butterflies closed and sucking carbon deposits out.
Or a quick thinking mechanic explaining why he took a clients 512bbi for a test drive and beat the pants off it LOL.
Even if there's no wisdom in it, it's still fun

Hopefully whatever lets a poor ST sit unloved for 9mos is fun. If it's flying I think you're ahead of the curve.

 

[CYYJ]

I bought the caps that have a colored end that are preset to the required pressure and at the set point are green on the end, as the pressure reduces they turn yellow then red. The idea of breaking off a stem is enough for me to change them as soon as I get home...

Mark:

What you have (a purely mechanical device) is different that what I was referring to (an electronic transmitter). The Garmin transmitters (description and specs here: Garmin TPMS Transmitter) weigh about 8 grams. If your mechanical valve caps have only a negligible weight difference from a normal valve cap, then perhaps you don't have to worry. But, I've never seen the device you have, so carry out your own due diligence.

Michael

 

[Highrider]

This oscillation sounds like a distortion in the tire, either from sitting or not installed properly.
I don't think any sensor add-on or out-of-balance condition would be detectable at 25 MPH, or to the point where it would be disturbing around that speed.
A 10 gram (1/3 ounce) out-of balance condition would start to be detectable above 60 MPH and a problem over 80 MPH.

 

[737Captain]

St1300r, she's certainly not unloved but had to sit in the company of my Norton and BMW while I had to concentrate on new work duties that of course involved flying. [emoji3]

 

[737Captain]

I'll be home on Sunday morning and go for a decent ride with regular valve caps.