is front tire causing tank slappers at high speed?

[ratsnest]

In the spring of 2006 I replaced the original trailwing tires on yelladog,my 2005 drz400,with dunlop d606's(90% dirt/10% street tread pattern).The wet spring limited bike use,but when a dry day came along,I made full use of it. On one of those days I found myself on a long,straight,empty section of suburban street and cranked the dogs throttle open to check out the new tires handling at high(for this bike)speed.All of a sudden,as eighty mph approached,the front end developed a severe headshake and the handlebars started slapping the gas tank most alarmingly!I could not regain control and went down hard.I have recovered from the injuries I sustained and am riding once again,enjoying it as much as ever.But I am concerned about the unusual wear pattern of the front tire.I have owned numerous on/off road thumpers in my 52 years,but have never seen the knobs on a front tire wear quickly and deeply on the front portion of each knobby,yet show very little wear towards the back side of the knobby.

I would appreciate hearing from anyone having experience with,or knowledge of any issues concerning the high speed stability of dunlop d606f tires.

Steve Thuman

member of the broken bone club. : ?

[zRedbullz]

The accident sounds severe. Tankslapping is a nasty moment and even when backing off the throttle or using the brakes, the outcome is made worse (as the level of grip becomes greater)

I've never owned d606f tires, and not that I will purchase one (of course!), but judging by the level of grip, tread pattern (tall knobs) and is designed primarily for desert riding - traveling the speed of eighty mph on tarmac isn't ideal, hence you get headshake.

Next time, if you continue to ride suburban street, you are better of getting lower profile and less agressive patterns to reduce the amount of grip and friction when at a certain speed.

Hope you heal well.

[don87xr600]

I don't think it's the tire. I've gone 93 mph on this tire and I believe Johnny Campbell used this tire at one time, he hits speeds of around 105 mph.

[zRedbullz]

I don't think it's the tire. I've gone 93 mph on this tire and I believe Johnny Campbell used this tire at one time, he hits speeds of around 105 mph.

So do you have any other ideas what the problem might be?

[ratsnest]

appreciate the response.

Steve

[Speedracer42]

It could be the tire, in one sense. It may be a different height than the old tire. The change in geometry could be enough to take weight off the front, especially at high speed and cause headshake. On the dirt and lower speeds geometry changes are not as noticeable. But on the pavement and higher speeds in can be a critical issue. Also your stock shock may bleed off when you are staying on the gas for a long time, causing the back end to squat giving you that same result. Adding compression or even better a revalve would correct that problem.

[thillsam]

I don't think it's the tire. I've gone 93 mph on this tire and I believe Johnny Campbell used this tire at one time, he hits speeds of around 105 mph.

Agreed. I have done the same, over 96mph on that tire per GPS. Low OR very HIGH tire pressures can cause strange knob wear, as well as the ill-handling described, and were most likely the culprit in this case. At those speeds, balance becomes a major issue too, especially on the front. I have watched the Honda A team balance tires down in Baja and it is a carefully respected process...

[Stinson]

Well I dont know about the tank slapper you could have hit something just right, but because you are running 90% dirt tires on the road, they are going to wear at a pretty fast rate on the pavement. Is the unusual wear you see on the rear of each knob? If it is than its from breaking. If its on the front, you must have a 2wd bike! Good luck tracking down the problem. Cya Stinson

[don87xr600]

It's more likely fork springs too soft for your weight.

[Goebz]

Well, I still have the trailwings on my DRZ and 2000 miles is showing uneven wear on even their low knobs.

I have an inducable headshake at high speeds but it has never become violent.After some research, the DRZ forum shows a common "thread" with the DRZ.

A lack of adequate lubrication and less than optinum torque on the steering head allows a hardly noticable vibration causing the uneven wear. It is more pronounced on the 606's and other tires with tall knobs on pavement.

The steering geometry of many "dirt bikes" produces theis problem to a lesser degree than the DRZ as the Zed is a Dual Purpose machine. Not many dirt bikes are street ridden regularly. SM's generally have smoother, smaller diameter tires.

The solution is to clean and repack the steering head bearings anually and tighten the spanner to the proper torque. First tighten the spanner to about 85-90ft lb to "seat" the bearing s and back off until the bars turn without too much drag. .

A rule of thumb test is to put the bike on the stand and gently push the bars to one side. Proper torque will stop the movemrent somewhere before the bars reach lock.

If not proberly lubed and tightened the bearings can prematurely fail.

DRZ400SK4 has nicely documented this procedure with excellent detail.

[ratsnest]

Thanks to all respondants.The tread wear IS probably from heavy front braking, something I do regularly. I'm thinking I need a complete set of wheels, tires, and front brake to swap quickly for on and off roading.

It's always something! And it usually costs money!

[Quino]

may sound stupid but check your tire's beeds are seated properly this will defitatly cause this "had that once before but on a rear"

[dennisthe]

I've had the 606 on my 650r and the front did wear the same way though I don't recall any headshake. I too had mine up to 96 on the highway. Could it have been a mounting issue or did you adjust the forks at the same time...?

I don't use the 606 any longer as it doesn't give my heavy bike the bite it needs in soft to intermediate terrain. Using a 756 right now in the front and gonna try the S12 or the IRC M1