Brake caliper screws & wheel bearings

[andyandy2]

My post on page 3 of this thread suggested that the op needed professional help, or supervision, he could quite easily of caused an accident with loose hub nuts mismatched pads, sticking calipers.
Is working on brakes on a road going vehicle really the place to learn mechanical skills, as someone suggested maybe try and help out at your local garage or as i suggested a college course. You tube video's, repair manuals and diy forum's are not the place to learn if you have no or little mechanical knowledge.

Read softus's post in general discussion about stopping distances, and then decide if you want to "experiment" with brakes.

DON'T take your car to Kwik-fit, find a local independent garage

If you want to work on your car, change its oil, change its plugs or filters, don't mess with brakes or wheel bearings untill you have gained more knowledge (sorry to be blunt, but in my mind its as dangerous as working on your own gas boiler or electrics)

 

[pretzelz]

Thanks for your concerns, I really appreciate your views.

You can breathe some sigh of relief. I'm also insured on my mums car, which is the car I primarily use for most of my car driving because its much nicer than mine and she rarely uses it... she walks everywhere. And it's serviced properly.

My car cost £540 and, although I did intend to do some driving with it, I also bought it with the intent to some day learn how to do some basic things with it. Since the brake pads wore out, I decided now was the time to start looking into it.

So after heeding your advice, I will stick to driving my mums car and just test this on the quiet roads in my suburb, at least for the next eight months, as I try to learn something about how it's mechanics work. If I choose to use it properly after that period, then I'll have a mechanic do it all. I also have my moped which I do my main A-B driving to uni, simply because the petrol is £2.50 a week. Can't argue with that.

Today I ordered an official hub nut for my wheel from a daihatsu dealer that I just found was in the vicinity. Although thanks for the previous link to order a hub nut online, looks like a good resource.

I've also just ordered a torque wrench and have found some Nm's specified in the service manual. The hub nut doesn't seem stated however. I'll ask at the dealership when I pick up the nut.

I'll have some questions soon about the floating caliper design, and with regards to my ceased parts. What isn't clear to me is, if two bolts go through the back of the caliper and out the brass into the plate behind the brake disc, where is there room for these to be flexible and move back and forth? And as suggested, push it backward so to fit both new brake pads, in the caliper, onto the disc.

http://www.wikiupload.com/download_page.php?id=90964

In the above link, I've drawn an arrow depicting the piston moving the brake pad out to clamp the disc in the caliper. And I've drawn (my misunderstood?) notion of the the restricted movement of the brass tubes with the caliper mounting nuts through them. ...in an effort to understand how, when they're bolting the caliper onto the bracket, they have any flexibility at all.

Thanks.

 

[Avocet]

Can't quite see from the photo but the main body of the calliper slides along those slideswith the rubber bellows on them - usually on a couple of hardened pins. It only needs to slide to take up the wear in the pads, so it doesn't need much travel. When it's all bolted up with no pads in, you ought to be able to grab the main body of the piston housing and slide it from side to side with almost no effort (just enough to overcome the stiffness of the bellows, in fact).

Also, looking at the photo, you appear to have a suspension bush that's absolutely knackered. It's on the far side of the hub, near the bottom of the page. it looks like it used to be a big rubber washer that's now split in several places.

What sort of wheel bearings did the car have? Were they tapered roller bearings or a sealed pack of ball bearings? If it's the latter, (by far the most common sort these days), you might struggle to buy a big enough torque wrench for the hub nut - they do them up to enormous torques!

 

[pretzelz]

I believe it's a tapered roller bearing. But I may decide that, since bearings don't have to be done every year, I'll let a garage do that one. Although I think I don't need my new bearing anymore.


Today I got my new 32mm hub nut from a dealer. £3.99 I bought a 32mm socket and put the new nut onto the shaft. Torque wrench hasn't arrived yet so I wasn't able to apply a specified torque.


From searching hub nut replacement on the internet (as none of the previous guides I had read mentioned this point) it seems what I have to do is protude some of the nut into the spindle "keyway", like this chap is doing:

http://www.miata.net/garage/fronthub/images/punch_in_large.jpg

into this

http://lios.apana.org.au/~c900/images/P2120027.JPG

And apparently that will stop the nut coming off, as mine did. Although I don't see how a small indent really keeps the nut on in the face of pressure. Any insight into that one?

 

[Stivino]

If you tighten the nut up properly, it probably won't slacken off even if you don't tap it in. But make sure you tap it in anyway.
It's probably not a tapered roller bearing on that hub, it's more likely to be a caged roller bearing. If you have the new one, can you post a pic?

 

[Avocet]

I Agree. With a hub nut like that, it's VERY unlikely to be a taper roller bearing. They almost invariably have a castellated nut with a split pin through it to stop it turning. What's the torque that they tell you to tighten it up to? It's normally something HUGE! I don't have a torque wrench big enough to do the ones on my car, but I normally just get a breaker bar (say) 2 feet long and stand on the end of it. As I weigh (cough!) "rather a lot" of pounds, that gives me a torque of "rather a lot" x 2 lbft. In other words, if I weighed 200lbs and stood 2 feet away from the centre of the nut, I'd be exerting a torque of 400lbft on it. The tricky bit is making sure you get a pure torque rather than just bending the extension bar. I sometimes put an axle stand under the exension bar between the soket and the breaker bar to act as a bearing surface. That sounds really hit-and miss but it's a method that has never let me down and my car now hs nearly a quarter of a million miles on it. I've had hub nuts off many times and they're actually not that critical on torque with the design of wheel bearing that I think you have there.

As for "staking" the nut (bashing a bit of the edge into a machined groove in the shaft), it works fine. It's very commonly done on lots of cars and they don't come undone. I'd be inclined to bash it a bit further in than the one in your photo, but I doubt the one in the photo would come undone in any case.

 

[cjard]

http://www.wikiupload.com/download_page.php?id=90964

In the above link, I've drawn an arrow depicting the piston moving the brake pad out to clamp the disc in the caliper. And I've drawn (my misunderstood?) notion of the the restricted movement of the brass tubes with the caliper mounting nuts through them. ...in an effort to understand how, when they're bolting the caliper onto the bracket, they have any flexibility at all.

Thanks.

If you were to bolt the whole thing back up without any pads in at all (and it was all working properly) it would make sense, as you would be able to slide the entire caliper up and down the brass sliders by a significant amount. As Avocet says it actually slides far less; we're talking millimetres.
When you press the brake the piston comes out and pushes the inner pad against the inner face of the disc, but the entire caliper that houses the piston will also move away from the inner face of the disc, clamping the outer pad against the outer face of the disc. Thus the pads squeeze the disc evenly on both sides, wear evenly, exert no overall force that will seek to bend the disc etc.

For more info see here:

http://auto.howstuffworks.com/auto-parts/brakes/brake-types/disc-brake2.htm