tires not subject to road "giggles"

[Barry]

"to see if the forks are providing the correct ride height."
Which I do not know.  

The whole idea of fork sag is very simple in principle.  When you are going down the road you need to have scope for the forks to absorb bumps by compressing but also you need some suspension movement to allow the forks to extend into holes. The  rule is to have approximately 2/3rds of the fork travel for compression and 1/3 for extension.  This is easy to measure with a zip tie around one stanchion.  You measure the full fork travel and then when you sit on the bike with all normal riding gear this will push the zip tie up the stanchion. When you put the bike back on the centre stand the amount of rider sag can be measured. Anything much less than 30 - 33 % of full travel means you should shorten or remove the pre-load spacers.  

Insufficient rider sag is probably one of the the most common suspension "faults" and is often a consequence of following the stiffer springs are better mania.

[georgesgiralt]

Hello !
Thanks Barry, I'll tie her down as soon as I can !  
I've checked the wheel bearings, front and rear. They are sound and perfect. As far as I can tell, there is no play in front wheel nor in the rear wheel. I user a dial to check for run out and there is "none" (the rims are somewhat marked by 30 years of tire change... So it is difficult to have the dial stay at zero)

[davidpdx]

I am not sure if this adds anything to the discussion but I have had the same problem with my tires wanting to follow any little line in the road. I had a pair of metzeler tires with plenty of tread but they were 10 years old. I just got new metzeler tire and I have noticed that the don't seem to "jump" into any little line like the old ones did. I only have 50 miles or so on the new tire but I actually looked for patches in the road to try them out on and it seems to have made a big difference.  

[Barry]

I have had the same problem with my tires wanting to follow any little line in the road. I had a pair of metzeler tires with plenty of tread but they were 10 years old

I had the same experience with an old but far from worn out rear Metzeler. I thought the effect might have been due to the tire being somewhat squared off with wear mainly in the centre of the tread.  

[Bob_Roller]

What is the date of manufacture of the tires, it's molded into the sidewall .

Should be a 4 digit number, like 0113, which would be a manufacture date of the first week of 2013 .