Front wheel wants to tilt or bend to the left under hard braking

[GabrielGoes]

Hey guys this has me stumped. Its a dual disc 77’ GS750. The tire is balanced, brakes work fine, forks arent leaking. This is very strange if i go semi hard on the brakes from any speed, the bike literally feels like its going to wash out and the bike will drop if i dont let off. The entire bike tilts to the left as if i am going to put it on the kick stand, if i let off it goes upright again and i can feel the force is coming from up front. I cant wrap my head around what would cause this. This isnt even an issue with single disc bikes lol does anyone have any ideas? Thanks

[hillsy]

Check your frame / forks / triple clamps for straightness.

[GabrielGoes]

Check your frame / forks / triple clamps for straightness.

Roger that I will update

[NavyDad]

Are both brakes working or is one caliper not operating? Is the wheel installed properly and everything tight? Are the wheel bearings bad and allowing excess play. First thing I would do is get the front end off the ground and check to see if there is any play in the wheel. Get beside the bike and put one hand at the top of the wheel and the other hand at the bottom and see if you can rock the wheel side to side. Moving on up, are the steering head bearings new? Are they adjusted properly new or old? Too tight or too loose will cause strange things to happen.

[GabrielGoes]

Are both brakes working or is one caliper not operating? Is the wheel installed properly and everything tight? Are the wheel bearings bad and allowing excess play. First thing I would do is get the front end off the ground and check to see if there is any play in the wheel. Get beside the bike and put one hand at the top of the wheel and the other hand at the bottom and see if you can rock the wheel side to side. Moving on up, are the steering head bearings new? Are they adjusted properly new or old? Too tight or too loose will cause strange things to happen.

It's a gs1000 front end, brand new head stock bearing top and bottom.

One caliper does seem to be hanging up.

I'll check for play in the wheel tomorrow when it's not freezing out. I don't think there is any.

What also stumps me if one caliper is hanging up how come this effect doesn't happen on all single disc bikes. I do have a feeling it might be the caliper though

[hillsy]

What also stumps me if one caliper is hanging up how come this effect doesn't happen on all single disc bikes. I do have a feeling it might be the caliper though

Your thinking about the brakes being more effective on one side than the other is sound - there should be no effect like the one you are experiencing from the brakes being impaired.

Something like this that is forcing the bike off line is more than likely as issue with the chassis being un-true or possibly a bad wheel bearing (??) that is making the wheel change orientation slightly under braking.

[LAB3]

The suggestion to check for some slop in the front end is a good one, my first guess would be a worn spacer or perhaps a forgotten washer somewhere upon axle/hub reassembly.

[gsrick]

It's a gs1000 front end, brand new head stock bearing top and bottom.

One caliper does seem to be hanging up.

I'll check for play in the wheel tomorrow when it's not freezing out. I don't think there is any.

What also stumps me if one caliper is hanging up how come this effect doesn't happen on all single disc bikes. I do have a feeling it might be the caliper though

Did you install the head bearings? Did you have the problem before? I'm not sure how that would affect the wheel in only one direction, but I have to ask. Is the triple new to you also or just the bearings? Maybe the bearing races aren't seated correctly. I'm just throwing ideas out there. I don't think I've ever had this issue with a bike, that wasn't wrecked. I would think that there has to be an issue with the axle or maybe a weak fork spring but even then unless a pinch bolt is loose......... IDK. I hope you find and post the source of the problem.

[Gorminrider]

forks arent leaking

but check the fork oil level anyways. remove the springs to do this.

[bobgroger]

Another thought is if you have the old rubber brake lines the failure mode is to swell up internally and not release pressure. Had a car that did that once, b!tch to find.

[hjfisk]

My guess is the lower triple clamps are not tight on the tube on the left side. And underbraking situation it is alowing the tube to twist in the triple tree.

[GabrielGoes]

Thanks all it took me a few days but problem is solved: The MAIN culprit I believe was the GS1000 fender hitting my exhaust pipes under braking it was forcing the wheels to turn a bit.
However i am glad i took your guys advice because before it all i checked the front wheel bearings and one of them was absolutely shot and wouldnt spin even if you tried to force it. In the meantime also the headstock bearing was VERY loose and used about 2 and a half whole turns before getting tight (this made the problem of letting go of the handlebars and the violent shaking go away). The forks now have 14 lbs of air in each leg and i put the gs750 fender back on so i dont have the hitting problem neither does the bike dive to the left anymore. So all in all i think it was the big fender getting tucked away in the exhaust forcing the wheel to turn, also it could have been the one bearing up front that was toast. Either way these problems are no longer an issue hope this helps someone in the future. Thanks everyone

[fbody_mike]

Glad you got it figured out. I had a GS450L that the previous owner installed a crash bar on, when under heavy braking the fender would hit the crash bar, so much so that it put a dent in the fender in the shape of the tube. Under emergency braking that bike would not turn at all. When I took the crash bar and moved it up that little problem went away. Even better that you got the head bearing adjusted, tank slappers can be deadly.