Diagnosis - warped rotors

So I have a small wobble ~70-80kmph, which gets worse as I brake.

I've checked the bearings, wobbled the wheels vertically and there's no play there, and theres only a thin layer of grease on the ball joint by the swivel, which I believe is normal. So my next thought, especially given that it gets worse as I brake, is that maybe the rotors are warped or have loads of build up.

I've done some reading online and it'd only take the rotors to be out by 1mm or less for this kind of effect

I've jacked it up and spun the front wheels. They stop after maybe 1 full revolution. I reckon I've got warped rotors or at the very least they need to be machined.

Thinking that next time I need new brake pads (a month or so), I'll get the rotors looked at and machined, or replaced.

Can anyone offer any input or give their opinions?

The rotors (we call them brake discs over here- except for the ones on a bicycle ) are unlikely to warp, but they do suffer from build up of material, which is made worse by holding it on the footbrake or by parking up with wet/muddy discs: they rust more behind the brake pads, and small amounts of brake pad material stick.

It wont hurt to lightly skim/grind them flat, but be aware that there is a minimum thickness allowed. If you go below this, likely nothing will happen,, but they might crack (or explode or the car burst into flames or your cow won't give milk or something, but it is a Very Bad Thing :dry: )

They are cheap enough to just replace, get some Pagid or Apec discs when you buy new pads.

Again, in The Olden Days when we had proper carcinogenic asbestos brake pads, you could get 200,000 miles out of brake discs, and fit 7 or 8 sets of pads in that time, now with "modern" tree-hugger organic pads you are looking at 20,000 road miles to a pair of discs.

The wobble is just something that jimnys do, the steering is underdamped, and your brakes are showing up a problem that is already there.
What you can do is shim the kingpin bearings to preload them- there was a Suzuki bulletin on here somewhere about how much force it should take to turn the hub on its swivel, or for a quick bodge, add a thin soft copper shim to the top kingpin. (copper shims, and a kit of steel shims are available in the shop)

The damping is actually from the friction of the dust seal on the ball shaped swivel housing, new seals can help, but the price will make your eyes water :blink:

I'd go for copper shims myself, and skim the discs if you can get it done for nothing, else new discs.

EDIT: just noticed the comment about the wheels stopping quickly. Make sure the callipers slide easily on the slide bushes with rubber boots at each end, that the securing bolts screw into. Do NOT put copper grease on them, only grease suitable for rubber.

Ok. Sounds all very complicated. I'll have a look at this again tomorrow morning and see if it's something I could do, or something it'd be better to leave to a professional.

Only done 30000 kms so shouldn't be too much wrong. Im due for a logbook service in a few weeks so I'll get a quote on having the "discs" machined and go from there - if thats what they recommend.

If it is still under warranty, at 30,000km , see what the dealer can do. (Brakes are wear & tear items, and like I said, 32,000 km is the typical life of a disc nowadays, but steering wobble when not braking isn't the brakes)


The copper shims are easy to fit, just undo the bolts, lift the top kingpin out, add the shims and replace.

www.test.bigjimny.com/store/index.php?_a=product&product_id=136

I'll see what I can do. it's an 08 model. No more warranty

I've ordered some copper shims. for $5, it's worth a go!

What lubricant would one apply before putting them back in?
Should I do to all 4 top king pins?
I dont have a torque wrench, is this a problem?

The copper shims fit at the top kingpins only. (where the pink circle is on the lower picture

The kingpin has a flat top with 4 holes in (lower picture), the "pin" part is the peg that sticks down into the actual bearing (marked A in the top picture)

You need to apply a little sealant (instant gasket) where the shading is on the kingpin to keep water out.









You may find that at 6 years your bearings are starting to wear, your garage will advise you, the copper shims will take up a little of this wear, but if the bearings are worn, they must be replaced.


In The Olden Days, we never had torque wrenches, just did the nuts up tight with a ring spanner by hand. I still do for most jobs, you get a feel for what "tight" means, the bigger bolts have longer spanners, so you naturally did them up tighter.

If this is you first job, you may be better asking your garage to fit them at the service, it wont take more than half an hour extra when they service the brakes to do both sides. ( I think the brake calliper has to come off, I don't remember)