[Ducati Scotty]

I found the AM26 had just the slightest, tiniest oscillation on grooved pavement at freeway speeds.  Couldn't even see it, could just barely feel it.  The BT45 doesn't have it.

Scot

[Boots]

Ducati Scotty,

I installd Avon Am26 90/90-19 and 100/90-19

My psi was way too high... 33, 35.

I can wait to see if this will help or not. Right now it's so bloody hot, 93, that I won't go near my bike! Gonna get out there tonight as soon as the sun goes down.

[Ducati Scotty]

Yeah, that's way high.  These are bias ply tires and made for heavy bikes so they're very stiff.  They seem to work well at pressures that seem way too low for a modern sport bike with radials.  I think you'll find it feels better with lower pressures.

Scott

[Boots]

Thanks for the tip Royalista! And the added info Scotty.  Fingers crossed!

[barenekd]

If you go back and look at the tire pressures that were used in the '50s, you will find that they are about what the Enfield requires now! 18F-22R in their very common 3.25 to 3.50 tire sizes. Even though it has a "Modern" engine, It's still basically a 1955 motorcycle and has the same characteristics.
Bare

[Boots]

Ok, tried 27 and 29 and it helped just a little. Went down a little more and it was the same. Afraid to go too much lower and out undue stress on the tube stem. Much less violent oscillation, but still present enough to make me wish I hadn't taken the damn freeway.

This is such a bummer for me. The bike is wonderful, but on this stretch of freeway it really blows. I have to take it or my commute will be more than double which just doesn't work for a teacher who must be on time to open his door in the mornings.

The OEM tires with less air pressure had a slight and manageable wobble that was relatively easy to get used to, or ignore. It is just too pronounced on the AM26s unfortunately.

I'm going to make another post regarding 3.5s up front just to gather a little more intel on the concept.

[Royalista]

Pity it doesn't work to satisfaction.
Definitely not reduce air pressure significantly below indicated because that will unbalance the ride.

As I understand Jartist has real life information on the conditions and your problem is basically caused by poorly designed road surface.
I have no experience on deep and wavy rain grooves. Not yet seen here. I'd try slow and if that doesn't work fast and if that doesn't do it then I'd be in your ball park. 

A wider front will not solve that nor improve performance.

As your problem is specific and localized a common answer is not obvious. Would it be possible to check out other riders using that stretch to find out how they tackle the issue?
It could at least point towards some direction to find a solution. (qualities demanded from tyre, front respective rear; and such).

Will remain interested. If it rains in California it starts to trickle overhere. 

[Bulletman]

Boots, I am running 18 psi front and 24 psi rear, and yesterday's temps here was 107 degrees. Since my C5 Wobble fiasco ( very very very scary ) from about 6 weeks ago, I've been running the above pressures, its been great, I rode all the way to Tahoe and then to Murphy's, Ive not had any problems, its not just the tire pressures that helped the wobble, but it did play a role in the same. I have the Same Avon tires that you now have on your bike.

[GreenMachine]

I don't have a c5 but I would think riding on a groove pavement is a PITA period...Throw in 18" wheels and the mix gets even more interesting...The thing u have to consider is if u implement all the ideas from the board members and nothing fixes it to the degree that you consider safe, you may have to resign yourself to live with it or sell the bike...

[High On Octane]

Grooved pavement sucks on bikes.  Period.  For what it's worth, every bike I've ridden on grooved pavement has been a sketchy ride.  Sometimes white knuckle scary.  My '58 Trailblazer only has a slightly more osculation with a ribbed front tire than my '83 Suzuki with dual sport tires did.  The first few rides on my Suzuki on grooved pavement were quite unnerving.  My friend told me to beware of the grooved pavement, but I didn't realize how unpredictable it really is.  No matter what tire/tire pressures you run, I think you're going to find yourself with the same problem.

I've found that keeping a "motocross" body position on grooved pavement really helps keep the bike stable.  This will not eliminate the osculation, but it help you feel more in control of your bike.
Sit upright on your seat with a slightly aggressive stance, but not to where you're exerting lots of energy to keep in the position.  Next, you need to change how you hold onto the handle bars.  Instead of just casually holding on or giving the bike "the death grip", keep you chest, shoulders and elbows square with your elbows pointing upward and outward.  If were to look at yourself straight in a mirror in this stance, you should see a rectangle formed between your chest, arms and handle bars of the bike.  While in this position, you want to keep elbows solid, BUT NOT LOCKED!  You will find that boxing your arms and chest over the handle bars greatly reduces the opportunity for the bike to want to "walk" where ever it wants.

Notice how even when airborne, the rider keeps the "boxed" position


Boots - Give this technique a try and let me know if it helps you or not.

Scottie

[sparklow]

I still have the original Avon SpeedMasters on my 2011 B5. I don't find them as bad as many on here have and I have done 65/70 mph on the highway for some distance with them. I have them at approx. 28 psi front and 32 psi rear, I weigh 200 lbs. Grooved pavement certainly sucks with bridges being the worst. After reading some of the feedback here I think my next set of tires will be Dunlop K70s!

[Boots]

ScottieJ,

I just tried your technique and it does indeed help me to feel more in control of a squiggly worm. Thank you.

[D the D]

Well, my K70s are better than the OEM rib front tire.  But, they still want to follow grooves to some degree.  It's a matter of finding a comfortable, usually slower, speed for the particular stretch of road.  Some contractors cut diamond pattern diagonal lines weeks before resurfacing blacktop here.  That can be irritatingly bumpy on strait sections but can be plain unsafe in curves.  Lay over in a turn then wiggle your handlebars left and right.   

[High On Octane]

ScottieJ,

I just tried your technique and it does indeed help me to feel more in control of a squiggly worm. Thank you.
TV

No problem!  I'm glad it helps for you.  Honestly, I discovered this technique out of sheer instinct.  It was the first time I really opened up the Indian and the first time I had taken this bike on grooved pavement.  I got up to 70mph real quick and all of a sudden I was all over my lane.  After about a half mile or so my dirt instincts kicked in and my brain started yelling "Posture Up!  Posture Up!"  It immediately turned a scary nightmare into tolerable thrill ride. 

Scottie