warped disc or bent axle?

[gaspy]

Hi Everyone,

I'm a mechanical and riding newb, but in the last few months I've done a few things on my own, including replacing handlebars, fork springs, fork oil, brake pads and fluid for both systems, and naked conversion of my F model to E (thank you, pantablo, Kerry, Alphamazing, and Coll0412!). Once the bike was street legal and I got it on the road again, I noticed a pulsating squeak from the front disc and brakes when pushing the bike around my local garage, and when rolling to a stop or pulling away at stop lights (slow speed).

I suppose two things could have caused this problem:
1) my low-side crash in November, which bent the handlebars from the force, and quite possibly the disc and/or wheel axle, right?
2) putting too much brake fluid in the front master cylinder when doing the system flush. I rode after the flush and noticed the disc was getting VERY hot, and was making a persistent rubbing noise with the new brake pads. A mechanic at my garage told me to drain some fluid out, and once I did this the rubbing problem went away. Could riding with the excess brake fluid and rubbing brakes have caused the disc to warp from so much heat and friction?

So, my question is, how do I know if my front disc is warped, or if the wheel axle is bent? See Scratch's post--http://gstwins.com/gsboard/index.php?topic=24803.msg255921#msg255921.

Thank you in advance for any advice, and I hope this post might help others with similar problems in the future.

- g

[ben2go]

You can check the axle bolt using a straight edge ruler.preferably metal but wood or plastic is ok.Lay the bolt on the ruler with the head touching the end, so the bolt runs along the rule's edge.If you can see light between the axle bolt and ruler,it should be replace.If no light can be seen rotate the bolt 90 degrees and check again.If it's flat it should be ok.

[yamahonkawazuki]

did you at any time remove the front wheel?

[bobthebiker]

What I've done to find out if, and exactly WHERE a rotor is warped, is I use a black permanant marker like a sharpie, and draw a line going around the rotor in various places, then spin the wheel.  where ever the rotor is out of spec and rubs, the marker line will disappear.     

I know its a shade tree solution to finding an answer, BUT I've used it, and it WORKS. cheap too.


Take note, this is with the wheel still mounted on the bike, and the front up in the air so the wheel will rotate.

[Fry]

What I've done to find out if, and exactly WHERE a rotor is warped, is I use a black permanant marker like a sharpie, and draw a line going around the rotor in various places, then spin the wheel.  where ever the rotor is out of spec and rubs, the marker line will disappear.     

I know its a shade tree solution to finding an answer, BUT I've used it, and it WORKS. cheap too.


Take note, this is with the wheel still mounted on the bike, and the front up in the air so the wheel will rotate.

That is the same method that I use to find out if a rotor is warped.

The Axle may have gotten bent, or Twisted in the fork legs, if you have sheet of glass lying around, I use that to check for straightness, just roll the shank portion of the bolt on the glass top and look to see if it maintains contact with the glass.

As for the Too Much Brake Fluid, I seriously doubt thats your issue, you'd have to pertae the brake system I believe before it would apply any pressure on the disc itself.

[gaspy]

Thanks for the awesome advice! I'll try the permanent marker trick, and I'll also use a ruler to see if the bolt is straight.

did you at any time remove the front wheel?

I removed the front wheel to remove the fork legs. What could I have screwed up when reinstalling it? I can't remember if it was making the noise before I removed the wheel.

[Fry]

Sometime when reinstalling the axle it can get tightened while bound up....I like to loosely fit everything, and with the Frt. brake held, rock the front end up and down a bit to get everything orientated correctly before I tighten everything down.