Rear discs 'on axle' lathe

[Petrol Pete]

Hi
Sine I have had my car it had an annoying rust ring on one disc (see photo) it passed MOT and does not make a noise or anything but it looks carp. When I painted the callipers I popped the pads out and they were OK so it was obviously an old war wound from the first 100K miles before I bought it.

New discs are available from about £60 a pair but another garage 'mate' of mine said he wouldn't mind running his disc lathe over them as he has not used it for a while and had someone booked in later this month.

So anyway the photos show those of you who haven't seen one before what goes on. There are different types of lathes around but this type aligns itself to any hub run out (the hub faced is polished with a flap wheel first to get 100% mating surface) Once set and running the pass to RPM ratio is set by the lathe and the tooling runs in an orbital fashion so as not to cut grooves in the disc face. on non drilled it does both sides at once , on drilled it can only do one face at a time.

It took just one pass to clear the surface leaving the discs 21.45mm thick which is way within spec.

Interestingly when he bought this machine 8 or 9 years ago it was used a lot but he says the price of discs have dropped so dramatically in recent years (China ?) that it is often not worth doing from a labour/cost/reward.

But he says he has done a lot of pretty new BMW X5 and other 4x4's where the disc is captive behind the Hub (who knew ?) which are much more labour-intensive to remove even if the parts are cheap(ish) ££.

We put a new set of Akebono Ceramic pads in, Job done.

 

[Abb]

Very impressive, especially the fact they didn't have to be removed! During my project, I removed a perfectly good set of AMG discs which were only replaced due to them being so discoloured in rust! This would have been a good solution!

 

[OneForTheRoad]

I rang a place at boro for this service . £80 plus vat .

 

[Codger49]

I rang a place at boro for this service . £80 plus vat .

Was that price per side, per disk, per axle or per car?

 

[OneForTheRoad]

2 fronts pal .

 

[Codger49]

Think most folk would just replace the disk with new.

 

[clk320x]

Think most folk would just replace the disk with new.

I suppose, but arnt some discs ridiculously expensive especially on AMGs?

 

[Codger49]

I guess the question then is whether these machines work on 'floating' disks as well as fixed disks?

If so, then I think a cleanup as shown above would be worthwhile.

 

[paul73mt]

This was used on a wheeler dealer episode looked impressive

 

[OneForTheRoad]

Think most folk would just replace the disk with new.

exactly what i did , shame though the discs that were on were run out after 500 miles or so . person that fitted them didnt bother cleaning up the hub face .

 

[Petrol Pete]

Think most folk would just replace the disk with new.

Agree, most would it's normally more cost effective as I said in my thread, its the route I was going down until he suggested blowing the cobwebs off the lathe.

 

[Petrol Pete]

Was that price per side, per disk, per axle or per car?

This would have been £90 including VAT. it is quite time consuming , about 2 and half hours in total.

 

[Petrol Pete]

I guess the question then is whether these machines work on 'floating' disks as well as fixed disks?

If so, then I think a cleanup as shown above would be worthwhile.

Do not think they work on floating discs as the machine has to set itself to disc/hub run out before giving the go ahead to cut. With a floating disc I can not see how that could be achieved.

 

[OneForTheRoad]

This would have been £90 including VAT. it is quite time consuming , about 2 and half hours in total.

the place at boro uses the latest laser guided cutter and takes around 20 minutes.

 

[Petrol Pete]

The cutting itself is quick, its the lifting of car/wheels off/hub dressing/caliper removal and doing the reverse (both sides) that takes the time. No chance that you could achieve all that in 20 minutes.

Curious as to what the laser you mention is actually doing. This lathe is fixed by design to the disc with 4 wheel bolts into the very hub upon which the disc is fixed and as a result the lathe is on a 3 legged wheeled frame which can wobble around all it likes as it has no bearing on the disc/tool interface.

 

[OneForTheRoad]

This system you don't remove calipers etc . its on google . Why skim discs with a Pro-Cut brake lathe - Skim My Discs . sorry like 10 mins per disc.

 

[Petrol Pete]

You will note that this is the same machine in my photographs on my original thread. You might also note that the video is a SALES video trying to sell you something (a disc lathe) Note that in the sales video there are no disc covers behind the brake rotors, you know, the bits of pressed tin (that normally rust) that we all have on our cars whether we like it or not. It is almost impossible to use this disc lathe without removing the callipers on most cars PLUS for the sake of unbolting 2 bolts you risk a lot of swarf collecting in your caliper. And normally if you were having this work done you would normally be replacing your brake pads (unless it was a 'tart up' before selling the car). Absolutely 100% no chance this process could be carried out in 20 minutes per wheel. Never

 

[markjay]

Think most folk would just replace the disk with new.

When I was a young lad discs were always cut once - halfway through their service life - either on the car as per above, or removed and taken to the workshop.

At some point garages stopped doing that... I think the issue is that dealers no longer fix or repair anything, they just change parts, and specialists can get branded (but not original) discs for very cheap, making the whole thing false economy in some cases (given that you are only extending the life of the discs by that much, and that you'll need to factor in the cost of replacing the pads anyway).

On some models the new discs can be quite expensive, but for many models you can get a pair of brand new discs from anything between £25 and £100.

See for example a pair of front discs for my car (W204):

Mintex:
NEW MINTEX FRONT BRAKE DISCS (2x DISCS) - MDC2214 | eBay

Ferodo:
Ferodo Front Brake Disc (Pair) DDF1693 Fits MERCEDES C250 S204 1.8 4044197496358 | eBay

Delphi:
Brake Discs Drilled 2x Front W204 C180 C200 C220 C250 CDI 1.8 2.1 Delphi | eBay

Etc.

 

[Petrol Pete]

Markjay, you reinforce a valid point that I made in my first post that skimming discs these days is not usually a profitable option - at least not in the UK where it is cheap and easy to buy new rotors. I think this type of lathe will be scrap metal in the UK in the very near future. But solid gold in Africa and other parts of the world without the easy access to spare parts that we enjoy.

 

[markjay]

Markjay, you reinforce a valid point that I made in my first post that skimming discs these days is not usually a profitable option - at least not in the UK where it is cheap and easy to buy new rotors. I think this type of lathe will be scrap metal in the UK in the very near future. But solid gold in Africa and other parts of the world without the easy access to spare parts that we enjoy.

In African countries, where parts are expensive and labour is cheap, the discs will get removed and skimmed on a lathe (the on-car one will be too specific and too expensive) - time after time, until the discs are paper-thin...

I worked in West Africa in the nineties and it was amazing to see how they maximise (and then some...) the service life of almost every consumer item. Very little is wasted or actually thrown away.