experience of front wheel bearings and judder

[nb1914]

do you experienced guys have any experience of front wheel bearings causing front end judder under braking ?
bearings seem ok with a standard push pull spin test by hand but under the forces of actually braking I'm not sure. i get bad judder with no lever pump so i think the disc is straight. i havnt changes fork oil yet but have rebuilt the calliper with new piston seal oil etc. what i can say is the calliper float ( calliper free movement on the mount )was very hard to move on the front calliper could that also be a cause.

 

[grizld1]

The problem may have nothing to do with brakes or wheels. What you're describing often happens when the steering head is a little loose, especially when tapered roller bearings have been installed. Give those cogged nuts a smack with a flat punch and the Big Friendly Hammer and see if things improve. Don't go overboard with it; a little movement can make a big difference.

 

[gggGary]

the calliper float ( calliper free movement on the mount )was very hard to move on the front calliper could that also be a cause.

Yes the caliper should be free enough that hand pressure will move it in and out on the mount when free of the rotor. and stiffness there could cause judder.

 

[nb1914]

thanks all i have some checking to do

 

[fredintoon]

The problem may have nothing to do with brakes or wheels. What you're describing often happens when the steering head is a little loose, especially when tapered roller bearings have been installed. Give those cogged nuts a smack with a flat punch and the Big Friendly Hammer and see if things improve. Don't go overboard with it; a little movement can make a big difference.

Hi grizld1,
good thought on the headraces perhaps being loose.
I'd go further and ask if nb1914 has ever greased or adjusted the headraces or perhaps upgraded them to tapered rollers.
And I have to say NO! Do NOT whack the headrace adjusting nuts around with a punch and a BFH!
Use a pair of C-spanners like Mr. Whitworth intended.

 

[5twins]

Yes, it's best to use the proper tool for the job. If you're shopping, you will find C spanners to be quite expensive, as much as $15 to $20 each. But now, with eBay to peruse, they can be had for a very reasonable price. These fit perfectly and a pair will set you back less than $8. No excuse now for anybody not to have them .....

http://www.ebay.com/itm/321756353972?_trksid=p2060778.m1438.l2649&ssPageName=STRK:MEBIDX:IT

 

[DanielBlack]

I've still got a small amount of jitter in the front end upon takeoff. Following the holidays, I'm going to get into the steering head and see what's in there. Thanks 5twins, I've purchased a pair of those c spanners.

 

[nb1914]

yip i have replaced the original ball bearings with taper roller bearings, reading i see they are harder to get set right. what i can say is i went for a quick spin before changing anything and I'm sure along with the judder i could at times hear a knocking. on my return i re-checked the locking nuts, loosened top pinch bolts etc then loosened the top locking nut without moving the bottom one. Then on checking the bottom tightness with a C spanner found it was very easy to turn another 1/4 rotation before getting any resistance, didn't go too far and then locked it, I only have one C spanner so on tightening the top the lower tightened slightly so i then undid it slightly while holding the top one with a screwdriver blade resulting i hope in it locking tight where i just got the resistance.I havnt managed ride it yet as the heavens opened but hope to tomorrow. I have also reversed the bottom clamp on the left fork which i had indeed installed the wrong way round (well spotted 5twins )

 

[fredintoon]

Hi nb1914,
here's the old-fashioned way to set the head race tension:-
Put the bike on it's centre-stand and jack up the frame to lift the front wheel off the ground.
Tighten the adjuster nut so the steering is quite stiff to move.
Carefully slacken the adjuster nut until the bars will stay straight ahead when you centre them but will fall all the way to the steering stop either side when you give the bar a little nudge.
Tighten the locknut down onto the adjuster nut (And really, buy another C-spanner, eh?)
Road test.
Note that this setting is for SOLO bikes. If you are running a sidecar tighten the locknut by at least another half-turn.

 

[5twins]

Yes, setting the bearing tension is often a "ride, adjust, ride" proposition. You should always check them a few rides after the initial install because many times they will have seated in more and become loose. Also keep in mind that many times after tightening that big bolt on top of the upper tree (I think it gets 40 ft/lbs), the bearings will become a little tighter.

I guess I should also mention this about those 2 slotted top nuts. If you examine them closely, you will find one side is flat and the other has a bevel or taper into the center threaded portion .....

I've found that installing them with the beveled sides facing each other allows them to tighten together more progressively and with more "feel" for just how locked together you've gotten them. This also presents a bigger flat surface down on the bottom nut to apply tension to the bearings, and a bigger flat surface up on the upper nut to better support the top tree.

 

[xjwmx]

Hi nb1914,
here's the old-fashioned way to set the head race tension:-
Put the bike on it's centre-stand and jack up the frame to lift the front wheel off the ground.
Tighten the adjuster nut so the steering is quite stiff to move.

This might be okay with roller bearings (which is what the op has), but DON'T do this with ball bearings. The overtightened starting point will ruin the balls and races and cause the steering to be notchy, and there's NO way to fix it except by replacing the balls and races both. With ball bearings, just snug them up and you're good.

 

[grizld1]

Fred, there's more than one way to skin a cat. I'm very picky when it comes to handling: cartridge emulators, springs chosen to achieve proper laden sag, premium shocks custom made by Works Performance, TX750 swingarm (thanks, 5twins), custom duraluminum wheel bearing spacers, and a lot of unsprung weight shaved off with a Brembo full float front rotor and plastic and titanium bits here and there. The result is a quick steering D-model that's stable and free of oscillation well into 3 digits of speed (in mph, not kph) and holds its line when flicked into washboarded corners. The practice for making minor adjustments to steering head bearing tension that I offered is one that I've used on various bikes for around 50 years. Please confine your yelling to people who do not know what they're doing.