Caliper block alignment to disk - GSXR

[Mario]

Last weekend I was at the track and I noticed the front wheel was binding more than usual, more than the regular rubbing of the pads against the rotor. I inspected the calipers and found the caliper block (sorry if using wrong name) was rubbing against the rotor, i.e. the rotor was not centered around the opening in the caliper.

Looking at the diagram in service manual, it looks to me that the fork axle clamp opposite to the nut is actually floating and only held in place by pinch bolts? I don't see anything on the axle that will make it sit lcoked in a certain position. In fact, after tightening the nut and releasing the pinch bolts, I am able to slide the axle on the clamp opposite to the nut.

Is this supposed to be this way? If so, it looks like I might need to tighten the axle, loosen the pinch bolts, align the rotor to the caliper (or at least get some clearance) and then tighten the pinch bolts again.

Does this sound right?

PS: the bike came back from front end alignment after hitting a wall at Sonoma, it might be possible that not everything is perfectly straight anymore. I never had this issue before.

 

[auntiebling]

Yes it floats, but there is also a proper method install the front wheel that centers it in the available space. I assume. Because this has been more or less "the way everyone does it" since the 90s or so?


Find a manual and read it regarding front wheel installation. It'll probably answer most of your questions. It might even be in the Owners manual that came the bike

 

[Demoni]

You are correct the side of the axle opposite the nut is floating. You want to let the fork and axle naturally align themselves before torquing the pinch bolts down.

Regarding the calipers you want leave the bolts loose and squeeze the lever, this centers the calipers on the rotors. Torque the bolts down with the lever applied.

I would also check your wheel and rotors for runout once everything is together.

:ride

Dave has some great content that helps explain both these topics.
Forks

Calipers

 

[Mario]

The way you are describing is the way I've always done it and never had any issues, that is until this bike hit a wall and got the front end a bit out of alignment. I took it to Jerry to get it straightened (triple and forks were bent) and it is all straight but probably not perfect anymore, it seems self centering is not happening anymore. I was able to slide the axle on the floating side and keep the calipers centered, but it might be putting the forks under sideways tension...

I'll read the manual and watch those videos tomorrow, I'll see if I get any pointers. Thanks for the feedback!

 

[OaklandF4i]

I always leave the pinch bolts very loose. With the bike off the stand and front brake applied, I strongly bounce the forks up and down.... this has always aligned the hub and calipers between the forks for any bike I've owned, regardless if the manual states so or not. Only after do I tighten down the bolts. Pretty much common practice in my experience.

If you think the forks are twisted in the tiple, loosen them to and do the same think Leave just one of the pinch bolts on the upper triple slightlylightlty tensioned with the rest loose. Usually aligns most dirtbikes I've crashed. If neither of these two processes aligns everything, something is bent. Though I doubt if Jerry aligned everything.

If a fork is truly bent, its usually obvious causing stiction and or fork seals failing rapidly.

 

[stangmx13]

How do you install the front wheel?

The proper install procedure is generally the following. Doing any of this out of order may cause the issue you are seeing:
- install axle and tighten nut/bolt to spec
- tighten nut/bolt side pinch bolts
- bounce front end with calipers off (dont accidentally grab the brake lever)
- tighten other side pinch bolts
- install calipers

If you need some way to hold the axle to tighten the nut/bolt, you can tighten the opposite pinch bolts. But you must loosen them before doing the rest of the install procedure, especially before the bounce.

Who did the "front end alignment"? If you took it to the dealer or that type of shop, they didnt do shit. At best, Id bet they loosened all the bolts and re-torqued. Nothing was fixed if something is bent. You need someone like GP Frame and Wheel to quickly diagnose a bend, or a suspension shop that is willing to take everything apart. Last time I had an alignment issue, one fork was not straight by <0.1". This caused the fork lower to be out of alignment by 0.2". You cant see that <0.1" visually. Other common bends that often can't be seen are the axle and lower triple. If you do the above procedure and the rotor still isnt pretty close to the center of the caliper, something is bent.

One other thing - check the fork lower and axle for burrs and nicks. If the fork lower doesnt slide nicely on the axle, it wont self-align on install. File or sand them off as necessary. And clean & grease that part of the axle & fork lower.

 

[Mario]

That's the procedure I follow (and also the same described in Dave Moss video). I even had guys from Catalyst look at it, they loosened front axle/pinch bolts, bounced the front end, tightened back. Still very little to no clearance on the free leg caliper block.

Front end was straightened by GP Wheel & Frame. My mistake is that I sent the bike to get it straightened without the calipers. I might have to go again and have Jerry look at it with the calipers installed.

 

[stangmx13]

Are the pistons/pads relatively centered in the caliper? If not, the pistons can bend the rotor when you install the caliper. To fix this, you can push the pistons back into the caliper, install it, then pump the brakes up to center everything. Make sure the pistons are clean before trying this and the reservoir doesnt overfill.

Other than that, I'd call Jerry.

 

[Mario]

I tried two things:

1) push the pads/pistons in, until they are centered, mount, then press the brakes, then tighten (like Dave's video posted here)
2) Mount everything without the pads in to see how everything falls naturally without the pads

Both without and with the pads, I get something pictured as below. The free leg axle is sticking out a bit and the rotor does not center on the caliper opening.

I will give Jerry a call, it might need some realignment.

 

[Mario]

BTW thanks all for the feedback, learned a few things. Did not know one of the legs slides free until held by pinch bolts. It all makes sense to me now. Some smart people designing this fast things :thumbup

 

[stangmx13]

ya, that fork is probably bent.

on modern radial calipers, tightening the calipers while holding the brakes does nothing. on 4-pot non-radial calipers, u shouldn't do that.

 

[Mario]

One more thing I can try... If the outer tube is bent, I can probably loosen the triple, rotate the fork tube and see if alignment changes? If it does, it should tell me it is the outer tube that is messed up (I believe Jerry told me he had to straighten the outer tube but not the inner). If this doesn't do anything, I might have a triple issue or an inner tube issue.

 

[stangmx13]

^^ Yep

 

[Darkness!]

Does your GSXR have radial or axial calipers? Axial means that the caliper bolts screw in parallel to the axle. Radial means they bolt into the fork leg pointing forward. Check that your caliper pin or slide bracket (if there is one) is free to move. If the caliper bolts are axial then the misalignment of the caliper might be due to a stuck pin or slide...good luck.