R12S : Rhythmic tug to the left in the handlebars

[adrianw]

2006 R1200S Ohlins 84K miles.

Hi,

After I got a new tire fitted recently I started to notice a rhythmic tug to the left through the handlebars at low speed while coasting/off the throttle (~10mpg and lower).

As soon you use some throttle it disappears, no issue at higher speed.

The brakes work fine and the bike pulls up straight.

The discs are true (they lie flat on a glass panel) and the callipers were rebuilt about 2000 miles ago with new pistons and pads (by myself so room for error)

With the front wheel in the air and the callipers off the wheel spins freely, with the callipers on you get a little drag but no 'pulse' to the left in either case - so I think it only happens with the front weighted.

I pulled the calipers off and zip tied them to the fork and drove about in a state of great paranoia and it is still there but not as obvious.

The head bearing feels smooth when moving the bars side to side with the front off the ground.

The tire itself looks true as in no bulges, the rims measure true (as in you can spin the wheel full circumference next to a static object nearly touching the rim without any contact-same for the discs and the disc bolts)

I used a Cardiac stethoscope on the wheel bearings and the head bearings - apart from a little creaking from the steering dampder it was clear of any noise.

A mate of mine, who spends a lot of time taking vintage bikes apart (and putting them back togethor) wondered if the steering dampner might be putting a bit of a wobble in the steering at sow speed. He also thought there might be a little play in the head bearing along the axis of the bike when pushing the suspenion up and down. Other than that clear and smooth for normal test of play. He (and me) have no real insights into how telelever or cossack front ends as he put it might go wrong.

I've done ~1000miles with it in this state and it is not changing.

My next step (when it stops bloody raining/sleeting) is to take it out for an hour and then use the thermal camera on the front to see if anything is glowing more than the rest.

Other than that it's a 'keep riding until it gets worse' play until it can be positvely diagnosed.

Any ideas?

Thanks is advance.

Adrian

[wayner]

Recheck tire pressure

I had a valve stem go bad and my new tire was losing air with similar feel

[bykemike]

One of my GS 1150s had a tug (if you will) on the bars as soon as you made the slightest attempt to lean left, which got worse as you leaned left more. It was a rim issue. It had a dent in the left side of the rim. The wheel wouldn't show a wobble side to side but had a slight up and down hop when leaning left.

I was going through Colorado and stopped at Woodys and they fixed it while I waited, very nice of them

[signit98]

At 84K miles, I'd also take a look at the wheel bearings...

[CARacic]

Or its the tire, you have done everything but remount the tire and you will have to remount the tire if you want to put a dial indicator on the rim. while having the tire incompletely seated is also a possibility if closely examining the tire rim interface doesn't reveal any irregularities, then the next step is to remove the tire to examine the rim bead area for any residue, look at he tire too. If the rim is clean, a dial indicator is cheap on the interweb. But call the folks you got the tire from.
good luck

[adrianw]

Hi,

Sorry I forgot to mention that I changed the front wheel bearings about 2000 miles ago. (last year)

I'm going to diconnect the steering dampner for a bit and eliminate that too soon.

Yes the tire I have been wondering about.

I have to wait for the tire fitter to come back from underwater cave diving in Africa first.

Lets hope the crocs don't get im.

Cheers

Adrian