Mild tank slap under heavy braking

[Mattb]

I just started noticing this phenomena; when I have to brake hard, which is infrequently, I notice some side to side wobble from the bars. When the bike was new I probably could have stood the bike on the front wheel with no vibration during deceleration.

I have a new set of BT-23's going on next week and am hoping this solves it, but should I have the mechanic check something else when I take it in?

8800 miles on the current set of tires (BT-20's)

 

[Rich]

Wobble also can come from looseness in the front steering head. This should be checked periodically.

 

[Phil Tarman]

I'd sure have the head bearings checked, and I agree with Christian about checking the fork legs. If you had a loose triple clamp, you might have a wobble. Or worse.

 

[Phil Tarman]

Well, doofus, it's a "knobby-screwy-thingie." What else would it be called?

 

[seagrass]

The wobble you are experiencing could also be caused from an unevenly worn front tire so it may be resolved when the new tyre is fitted.

Seagrass

 

[mikesim]

Hmmmm... it seems to me that if it was looseness in the steering head that it would also be noticeable under other conditions besides braking. Since it appears ONLY when braking, I would have the mechanic check the front rotor for a thickness variation or excessive runout. He can check this with a dial indicator when he has the front wheel off for tire mounting.

Hope this helps!

Mike

 

[Mellow]

The wobble you are experiencing could also be caused from an unevenly worn front tire so it may be resolved when the new tyre is fitted.

Seagrass

That's what I'm thinking.. Approaching 9,000 miles the front is probably cupping some.. when hard on the brake you're transferring the weight from a 40/60 front/rear to more like 90/10 which is another reason why using front brakes is so important and so many on non-linked brake bikes will slide the rear wheel under heavy braking... anyway, that transition of weight is probably magnifying the cupping on the front tires and causing some wig/wag.

That's not to say there may not be other issues, but a new front tire is an easy check.

 

[Argyll]

Front tire wear is almost certainly the issue here. Only if the bike was older would I suggest checking the steering bearings.

I hate the tread pattern of the stock front tires - it seems to contribute to very poor handling characteristics when worn.

 

[Phil Tarman]

doofus?

"Doofus" is a term of endearment. It implies that the person it's used with may not be the sharpest knife in the drawer, the brightest bulb on the tree, that their elevator might not reach the top floor, that the lights may be on but nobody's home....

Hope that gives you an idea of what "doofus" means.

Wiktionary.com defines a doofus as " A person with poor judgment and taste." Rick is neither of those.

 

[Mattb]

Front tire wear is almost certainly the issue here. Only if the bike was older would I suggest checking the steering bearings.

I hate the tread pattern of the stock front tires - it seems to contribute to very poor handling characteristics when worn.

While waiting for the rest of my club to show up this morning, I ran my hand along the surface of the tire and sure enough, it feels uneven - as if each section of tire past the tread pattern is lifted ever-so-slightly.

New tires should be in and on this week and I'll have the mechanic check the entire suspension and steering just in case.

Thanks for all of the helpful comments.

Oh, and by the way, the rest of my club no-showed due to "weather". It was beautiful. Here's my sad/lonely face - all alone at the rally point:

 

[Mattb]

It was the tire. New set of BT-23's were installed today and I am amazed at the difference in feel! The bike seems to want to roll left and right at the slightest press of the bars, but tracks like it's on rails. I am impressed.

Interestingly, the mechanic said that both wheels balanced perfectly without weights. He said he's seen one out of two like that before, but never both wheels.

He also said that new tires are "greasy" and to take it easy a few days.

 

[rcase13]

I have 3000 miles on my front tire and it's cupping. Is this just a charcteristic of this tire or am I braking wrong? I brake the way I was taught in the MRC class. That is I use both brakes.

 

[Phil Tarman]

If you're talking about the OEM BT-020, I think my front cupped pretty badly. But nowhere as badly as the Dunflop K700 that was the OEM tire on the ZG-1000 Kawasaki Concours. It's not your braking technique.