diagnosing "diving" (?) problem

[Anonymous]

Need some help (again) from the list,

Started out to just change the tires. . . Yesterday I finally got back on the road after getting everything back together (tire change, balanced tires, changed sprockets and chain, aligned wheels) and experienced a very noticeable hobby-horseing while riding that wasn't present before the long down-time. The front end goes up and down while riding.

Fork problem? Diagnostic test?

Tips appreciated,

Seth

[Anonymous]

If it was fine before you made then changes.. you may have a tire out of round.. yes it's rare. or your tube may be twisted in the tire. (if you have a tube..) Balance tires yourself.. or shop.. Just a thought.. others probably know more than me... Good luck.

[Anonymous]

Thanks. I mounted the tires (and installed new tubes at the time) myself but then took them to a shop to have them balanced. Perhaps I'll pull the front one and try a crude balance test here. I wasn't sure that wheel balance could cause the fore and aft pitching I was experiencing. Perhaps if the wheel is out of round....?

Seth

[kz]

Tires have something called uniformity that means that the "stiffness" of the tire is different around the tire.

"A square wheel can be balanced, but a square wheel will not give a smooth ride."

I know that this can be a problem at car tires, don't know if MC-tires have the same problems, due to a motorcycle is not so heavy.

If you are unlucky to get a tire with a uniformity out of tolerance, it feels like an unbalance but it is NOT possible to balance by normal balancing, the only way to correct it is to use a device that measures the uniformity and match the uniformity to the run out of the rim. It is NOT possible to correct the tire.

Normally for us deadly people, we just change the tire or/and the rim. 8O

The tire industry normally measures the uniformity and after that classifies them into first, second and third class, the best class is delivered to the car manufacturer because they have machines to measure if the tolerance is to big, the second class goes to the authorized dealers and the third class goes to gas stations etc.

You can also see the link below, explains the matter in a better English... :roll: :

http://www.hunter.com/pub/product/balancer/4127t.htm

Has anybody had problems with tire uniformity on a GS?

[Anonymous]

to me diving means that when you pull the brake lever the front end goes down toward the pavement and then gradually returns as you come ot a stop-if it is a pulsing movement and its the tire, it will occur when you are moving slowly without the brake being apliedand who knows what when you are going faster. If ot occurs when you are coming to a stop while applying pressure to the brake lever and it disapears if you momentatily let the lever go then a rotor is out of true.

[Anonymous]

to me diving means that when you pull the brake lever the front end goes down toward the pavement and then gradually returns as you come ot a stop-if it is a pulsing movement and its the tire, it will occur when you are moving slowly without the brake being aplied and who knows what when you are going faster. If it occurs when you are coming to a stop while applying pressure to the brake lever and it disapears if you momentarily let the lever go then a rotor is out of true.

[kz]

to me diving means that when you pull the brake lever the front end goes down toward the pavement and then gradually returns as you come ot a stop-if it is a pulsing movement and its the tire, it will occur when you are moving slowly without the brake being apliedand who knows what when you are going faster. If ot occurs when you are coming to a stop while applying pressure to the brake lever and it disapears if you momentatily let the lever go then a rotor is out of true.

Agree

[Anonymous]

"diving" clarified

OK, point taken about what connotation goes with "diving." I was (still am?) struggling to describe what I was experiencing. Let's try again:

30 mph (didn't try other speeds), going straight ahead, no turning, no braking---and the bike is "pitching" back and forth. By pitching, I mean that first it "dives" forward (as IF the front brake had been applied) and then it rocks back toward the rear and then the cycle repeats. So, I also called it "hobby-horsing" (think of the motion of the old childhood rocking horses).

How do I tell if the rim is out of round as opposed to out of balance?

Thanks for the feedback to date,

Seth

[Anonymous]

i think you are having a caliper problem--or are your front disks rusted- did you remove the disks when you were working on the front wheel???--Put the bike on the centerstand and rotate the front wheel--you should feel the dragging--see if you possible put the speedo drive back on improperly--it has to be something obvious. a binding bearing--strange noises etc etc--look look look listen listen listen

[Don Lobacz]

It sounds to me like your bead did not seat all the way (the lip of the tire did not come all the way out to the edge of the rim). Put the bike on the centerstand and spin the back tire, and then jack up the front and spin the front. One of them should have a huge in and out motion where the bead is not seated.

[Anonymous]

Sethm,
I recently took my front wheel off for some cleaning and maintenance. After putting it all together and taking it for a test spin, I immediately noticed a wobble and hesitation. I put the bike on the centerstand and realized that the wheel went on crooked. Of coarse the rotor rubbed on the pads, just enough to make it feel as though I was lightly applying brakes on and off. I had somehow put it back on unevenly. I took it apart, put it back together again, and it fixed the problem. Hope it helps.

[Anonymous]

Update

OK, thanks everyone. Followed Scotty's advice and just tried looking closely. . . (duhhh):

With the bike on the center stand, front wheel free to spin, I can see a low spot as I rotate the tire. Closer inspection reveals that the tire (bead) is not uniformly "seated" (don't know if that is the correct term) to the same depth. After work, I'll try deflating the tire and seeing if I can get it to seat uniformly. Is there any procedure I should know about (but obviously don't)?

Seth

[Anonymous]

Seth,
I had the exact same experience with a rear tire on my 1100. Didn't realise the problem till I got up to about 35-40mph.
No real trick to getting it seated correctly. Just deflate it, unseat the bead all the way round on that side, wipe the bead with soapy water, remove the valve core, inflate the tire using an air compresser until the bead pops into place (keep it under about 50psi or there could be trouble), let it deflate, then reinstall valve core. Now you can fill it back up to recommended pressure.
Good luck,
Axel