Triumphrat

Scrambler900 · 09-04-2006

I hope someone can advise me about a vibration issue with my new 2006 Bonneville T100. The bike is currently stock with 1,300 miles total, (except for the oxygen sensor removed), and at speeds over 70 mph, the rear end develops a very noticeable vibration that increases as the bike speeds up. At 80 mph, which this bike should be able to do with no problem, and in my opinion with less vibration, I can feel the seat and particularly the rear end buzz and vibrate a lot. Up to 70 mph, the bike runs smooth with little or no vibration. It's just that going 80 mph or more results in a level of vibration that should not be present with a new bike with new tires, in my opinion.

The rear tire's air pressure is correct at around 32 - 34 psi, and no balancing weights have fallen off the rear rim (assuming Triumph correctly balanced the rear wheel at the factory). Also, the chain tension appears to be OK, and the left and right side rear tire alignment indicators seem to be at an equal setting. There are no broken, loss or missing rear spokes as far as I can tell.

Should I get the rear tire pulled to see if it is balanced correctly? Or perhaps the rim is defective or "out of round"? Perhaps a wheel bearing is bad? I need to adequately describe the problem to my dealer so his mechanics will take the trouble to check it out.

When I bought the bike new, the first 1/2 mile of riding identified a defective front rim (offset weld), as the handlebars shook a lot and the front wheel hopped quite a bit. Fortunately, when I went right back to the dealer, the diagnosed the problem and swapped another new front wheel and rim off another T100.

Any advice would be much appreciated. :???:

[ This message was edited by: Scrambler900 on 2006-09-05 16:36 ]

badrufus · 09-04-2006

I don't know what tires your bike came with, but on my 05 T100, the OEM Metzler MEZ2 rear tire calls for 38 psi. If indeed your rear tire calls for 38 and you've been running it 5 lbs low, the tire could be damaged and dangerous, thus the vibration.

flashmc · 09-04-2006

The last time I was in the dealership the service manager gave me a pressure guage with 36# front, 42# rear printed on it. I remember when I bought my T-100 he also mentioned it then. That is the pressure I try to maintain. I did ask if the 42# was high, as that seemed a bit high to me, but he claimed that for our altitude it is just right.

Robert

amanger · 09-05-2006

I think you should be checking the wheel balance.At the speeds you are talking about,that is the range where the resonance from the rear shocks and an unbalanced wheel will co-incide causing vibration.
I spent 5 years as a front end technican,end fiont end vibrations will nearly always occur below 60 mph and rear above.
The tyre may have been deflated at some stage and rotated on the rim causing it to be out of balance,has it had a flat tyre?
Or it may have just been done late on Friday arvo when the production worker was in a hurry to knock off.

ohiorider · 09-05-2006

Quote:

On 2006-09-05 01:08, amanger wrote:
I think you should be checking the wheel balance.At the speeds you are talking about,that is the range where the resonance from the rear shocks and an unbalanced wheel will co-incide causing vibration.

Amanger - could you elaborate a bit more on the shock resonance/unbalanced rear tire thing? My T100 is fine, but I'm going thru a similar problem on my W650. I'm having a hard time determining whether it is front or rear end.

I just installed new GT501s on the W, and am experiencing vibration anywhere over 60-65 mph.

I tried to isolate it by (a) reaching forward while riding and feeling the lower fork leg .... can't tell if it's road vibes or out of balance. Also reached back and put hand on rear shock spring .... seemed to be pulsating, even at slower speeds.

When I got home, I put bike on center stand, in 5th gear, and ran it up to approx 60mph, with no apparent vibration.

I'm going to try to ck the front wheel balance without pulling the wheel. I will pull the brake caliper, and spin the wheel several times and mark it to see if it stops at the same place, but don't know if the front wheel bearings spin freely enough for this test to be valid.

Shocks are the originals that came on the bike from the factory, with over 50K on them, which could be the problem. I'm ok with the ride, but the shocks are probably worn out, or at least not responding properly to normal small road irregularities.

Any thoughts will be appreciated.

NOTE - the W seems a lot more sensitive to minor wheel and tire irregularities than the T100.

Bob

Normandy · 09-05-2006

Quote:

On 2006-09-04 18:08, badrufus wrote:
I don't know what tires your bike came with, but on my 05 T100, the OEM Metzler MEZ2 rear tire calls for 38 psi. If indeed your rear tire calls for 38 and you've been running it 5 lbs low, the tire could be damaged and dangerous, thus the vibration.

.................................................. ....

I disagree, sorry. I don't think 5 LB low would be a serious problem at all.

amanger · 09-05-2006

All coil springs have a resonance rate.That is they vibrate at a certain rate much like a musical tuning fork.It is only when the wheels are rotating at the same speed as the spring is resonating that you will feel an unbalanced wheel.
I m not sure of the physics behind it all,but front suspension springs resonate at a lower pitch (speed) than rear,which is why you feel an unbalanced front wheel in the 80-100 km/h zone and rear usualy above 110 km/h.
:???:

Scrambler900 · 09-05-2006

Thanks fellas, for this good advice, and I will check out my bike according to each recommendation.

ohiorider · 09-05-2006

Thanks, Amanger,

Bob

Sheepdog · 09-05-2006

Just a couple more suggestions: Check the rear wheel alignment, the tension of the spokes, and the torque on the swingarm pivot. In the old days these were common culprits for bad handling characteristics.