Rain-grooved pavement

[Dwmadsen]

I have a - new to me - R65 and had a near death experience. I was riding the same highway I have been riding for 25 years and when I got to pavement with rain grooves, the bike began to shake uncontrollably. I was going around 60 mph and immediately began slowing down to 50…40…30 mph with the shaking threatening to pitch me into three lanes of traffic. Before I could cross three lanes to get to the shoulder, the pavement switched to non-grooved pavement and the bike was immediately stable. I have ridden various bikes along this stretch of road without ever having issues.

I have new Metzler tires with “C-block” tread pattern. The tires are inflated to 26/28 (front/rear).
The bike has new head tube bearings - no play.

So, my question is has anyone running tires with “C-block” tread experienced violent head shake on rain-grooved tires?

[Bob_Roller]

What model tires do you have??
I would also suggest you increase tire pressures to 32 psi .
Tires with a center groove in the tread seem to have issues with rain grooves .

[Barry]

Agree, the old under seat tyre pressures are too low for modern tyre construction.

On the head bearings, they need to be adjusted a little beyond no play. A touch of pre-load such that the bars will still fall side to side but not so fast that they bang against the stop. This provides a degree of steering damping.

[georgesgiralt]

Hello,
This was my experience back in the days. Now; with recent design tires and gum, the problem is less present or absent.
I second the pressure advice (I'm a metric man so can't vouch for the PSI number) but you need to go past the old pressure advice BMW gave 40 years ago.
I run Michelin tires (Pilot activ and now the Pilot classic) and the groove problem is non existent. It was the same with Heidenau tires beforehand.
Hope this helps.
P.S. : I always fear these grooves and strongly reduce speed when seeing them in front of me. Once bitten.....

[Burt]

Not so much rain grooves but when they are relaying the bitumen and they cut similar grooves into the surface prior to laying the new surface.  Horrible things. 

I'd be looking at 32/36 psi as a starter.  The lower pressures will also affect the handling in other ways. 

[dogshome]

All of the above. Pressures lower than 30 are horrible on wet, white lines. Combined with worn head bearings (or loose or tight) ones makes the experience very uncomfortable. Not a tank slapper, but wakes you up and slows you down in a hurry!

I just replaced head bearings. Adjustment allows the head to fall to each side, not bind or be slow. No free play by grabbing the front axle. Sounds like its mostly tyre pressures in your case. I have an R65 which is technically a slightly quicker steering setup than 80/90/100.

[Barry]

Back in the 70's airheads were known to be fussy about choice of tyres and this used to be discussed in the more enlightened motorcycle press. For stability they needed stiff tyres. My under seat chart lists a choice of 3 different makes and model of tyres to fit as well as the pressures which at 27 psi Front and 26 psi rear seem insanely low by modern standards. For years BMW maintained an ongoing  updated list of which additional tyres had been tested and found acceptable. They were communicated to the dealers by service bulletins and they were not supposed to fit anything else. Even if old tread patterns are still available the tyre construction will be modern and require a minimum of 20% higher pressures and more than that on the rear to work well. 

The other thing I've learned about tyres is that what feels like front end instability on grooved surfaces or white lines can be caused not just by the front tyre but also by the rear.

[Dwmadsen]

I changed the rear tire to an Avon MKII and that helped considerably. I then changed out the front to a BT46 and I’m back to ‘no surprises’. Pretty expensive lesson.

[dogshome]

Thank fo feeding back 


Tyre pressures didn't help? Or didn't you want to risk it!