Front end shudders during braking

[stan23]

Hi! first post on your great forum! 

Bike: '97 Monster M900 with the stock non-adjustable forks--Bike has 16K.

Forks have new seals, along with new oil. New brake pads too (EBC HH installed 300-miles ago).

Problem:

During heavy braking from say 50mph, the front end shudders real bad. If I look down at the fork, I can see the front fork moving up and down really quickly. At first thought, I thought the rotors could be warped, but If I put the bike on a front stand, and spin the wheel, I do not notice anything abnormal. There looks to be even drag.

Another hint to lead me to believe it is not the brakes is when you try and turn the bike during low speed riding (5-10mph) the front wheel feels like it is 'hunting' meaning, it is tracking un-smoothly, and you can feel a similar shudder, although not too bad.

I have also loosened the pinch bolts and pumped the forks up and down to center the axle. Tires are freshly mounted Michelin Pilot Road 2CTs, and are not worn or flat-spotted.

Previous owner mentioned when one fork seal was leaking, the shuddering problem did not exist. Only until he serviced the forks did the problem come back.

Any ideas on what to check next?

Thanks!

[Pedro]

Have you checked the steering head bearings?

[Hedgehog]

Sounds like the pads are contaminated with oil, to me.

[Howie]

Definitely check the head bearings, but if only one fork is moving rapidly I would suspect there is a problem with one of the forks.

[stan23]

Thanks all, I will check the steering head bearings next.

The pads are new, and was beaded in properly. The old pads were worn even, and the pistons on the calipers looked good.

I don't know if one fork is moving faster than the other. I just poked my head down there when I was braking hard momentarily.

[EEL]

ITs called front end chatter. It can occur for multiple reasons.

1) Pads as mentioned are one of the reasons, Try to get a rag, spray it with contact brake cleaner and rub the rotors clean.

2) Your rotors are warped or badly grooved.

3) If you're braking really really hard and your forks could be bottoming out, a very dangerous condition. Here's a simple way to check. Put a zip tie on a fork slider(not too tight but snug). For for a ride and try to SAFELY replicate the conditions resulting in the chatter.

Then go home and lift the front end of the bike with a front stand (I am assuming your have one). Make sure you dont touch the zip tie in the process. Then measure the distance from the bottom time of the dust seal to the top of the zip tie. This will give you your total fork travel. Look in your manual and compare the total fork travel distance to what your measured. If its within a quarter inch, you need to fix your suspension before you wash out your front end..

[stan23]

ITs called front end chatter. It can occur for multiple reasons.

1) Pads as mentioned are one of the reasons, Try to get a rag, spray it with contact brake cleaner and rub the rotors clean.

2) Your rotors are warped or badly grooved.

3) If you're braking really really hard and your forks could be bottoming out, a very dangerous condition. Here's a simple way to check. Put a zip tie on a fork slider(not too tight but snug). For for a ride and try to SAFELY replicate the conditions resulting in the chatter.

Then go home and lift the front end of the bike with a front stand (I am assuming your have one). Make sure you dont touch the zip tie in the process. Then measure the distance from the bottom time of the dust seal to the top of the zip tie. This will give you your total fork travel. Look in your manual and compare the total fork travel distance to what your measured. If its within a quarter inch, you need to fix your suspension before you wash out your front end..

Thanks for the reply. I am quite familiar with suspension, but this new to me bike has me stumped.

1. The pads are new. Rotors are clean. Pads were beaded correctly. But I can measure the rotor run out, just for my sanity.

2. Again, I'll measure the rotor run out.

3. Forks are not bottoming out. I can feel the shuddering even in relatively mild braking force.

[davejenknz]

Previous owner mentioned when one fork seal was leaking, the shuddering problem did not exist. Only until he serviced the forks did the problem come back.

Sounds like a problem with the fork service. If nothing else changed.
Check your damping, pre-load, fork height and air gap.

I've just cured my Brake shudder (low speed) with a service where I re-oiled (Ohlins 22cst) and re-adjusted fork height, preload and damping. I also dropped the oil level by 10mm.

[Ducnial]

Check the front wheel bearings too.  Unload it and via spools or axle and look for wobble by grabbing the tire and rock top and bottom.  If you feel any play then the front bearings are either toast or need adjustment.

[Howie]

Also make sure the rotor buttons are clean.  I would still consider a possible fork problem if the pads were replaced before the forks and the problem happened after the forks.

[jerryz]

Clean the buttons and even better take off the rotors and bash the buttons  with a big hammer and a 19mm socket the result is full floaters and no chatter.

[mangeldbug]

Check your fork oil level. 

Also, what weight fork oil did you refill with?  Stock oil is supposedly 7wt (or something heavier?) -  I remember it being very thick when I poured it out.  I refilled with 5wt since before they felt unresponsive, and now its really flowing through the valves and the progressive rate springs are blowing past the beginning with every small bump (which there are A LOT of in Pennsylvania).  I also get more front end dive upon braking.  My next mod is fork suspension.