Brake disc thickness?

simonsGSA

Registered user
Joined
May 8, 2018
Messages
96
Reaction score
1
Location
Hampshire
Took my 08 GSA with ABS to a main dealer for the long overdue rear wheel flange recall. They did a check and found a few other issues:

Front suspension ball joint boot split - I will change this before the next MOT.
Rear brake disc 3.8mm (min 4.5)
Front left brake disc 4.17mm (min 4mm)
front right brake disc 3.82mm (min 4mm)

Rear has been on my to do list for a while but are the fronts in need of changing or are BMW being a bit oversensitive to the minimum thickness?

Also, where is the best place to source pads and discs?

They did offer to do it all for me for a mere £1100!!!!
 
Hi

Those figures are the manufacturers recommendation, the MOT manual says

1.1.14. Brake discs and drums
A brake disc or drum must be significantly worn before rejection is justified. Being worn below the manufacturer’s recommended limit is not a reason in itself.

Bearing in mind from your figures, the most wear is on the rear disc at 0.7mm. Thats 0.028inches, or 28/1000, the thickness of around 8 human hairs. Thats hardly significant wear.
 
I've just had my rear disc replaced with genuine BMW parts. Mine was getting a little worn and with the wear pattern on it I didn't want to put a new set of pads on on their own as( pads were almost worn out) I thought they might take a while to bed in as the disc was a little dished.
I had the main dealer do the work as the bike was in for a new fuel strip to be fitted, plus I get a warranty on it as it was fitted by BMW.
I was also wary of taking the old disc off myself as the bolts are most likely well bedded in with locktite. So didn't want to cock it up.
Rear disc, new bolts and BMW pads Inc fitting was a little over £200.00 . I didn't think that was too bad. Another £900.00 for the fronts to be done sounds a little bit extortionate to me.
Anyway I got 110.000 miles out of 2 rear discs so it's not really that expensive. Second set of fronts on the bike have still got loads of life left in them I expect them to last for another 30.000 miles or more.
 
Disk wear.

BMW car or motorcycle, BMW "Dangle the Skeleton" at every opportunity. As others have said, the wear level to from BMWs point of view to change a disk is insignificant.
I have spent a lifteme ignoring their suggestions to replace perfecly good disks.

I will replace any disk showing signs of cracking warping or scoring, but this policy of theirs is just job creation.
 
Myke Rocks said:
BMW car or motorcycle, BMW "Dangle the Skeleton" at every opportunity. As others have said, the wear level to from BMWs point of view to change a disk is insignificant.
I have spent a lifteme ignoring their suggestions to replace perfecly good disks.

I will replace any disk showing signs of cracking warping or scoring, but this policy of theirs is just job creation.
Click to expand...

There you go, it's the way forward :thumb2

The discs on my GS, at 73k. are below the wear limits but they are good to go and as i'm an awesome rider that is always in the right gear at the right speed
for every situation negating any need for braking the discs are not wearing very much at all so i'm expecting them to be there for a long while yet :thumb2 :D
 
are BMW being a bit oversensitive to the minimum thickness
Click to expand...

In my experience, they are.

Bought a used bike years ago (for a friend) and when the owner did show us the service history, it had all three discs replaced at the 20k km service.
I asked if he bent them somehow (all three...) and he told me no, the dealer considered that standard procedure because they were worn. 20k kilometers... 12,000 miles :D


Same thing happened on one of my bikes when the dealer insisted in replacing the disks (40.000km service) until I asked them to measure the thickness. Then they shut up.
I understand brakes (calipers/discs) might have shorter lifespan due to corrosion/salt at this latitudes... but all the above seemed like taking the piss.
 
I get countless customers in winter who’ve been and taken “advantage” of BMWs day dealers “Free winter safety check” and have been told their discs are worn and dangerous...... and they aren’t. I do wonder who’s taking “advantage” of whom, and the altruistic “free” check must certainly be a good earner during a quiet time of year. :D
 
Steptoe said:
I get countless customers in winter who’ve been and taken “advantage” of BMWs day dealers “Free winter safety check” and have been told their discs are worn and dangerous...... and they aren’t. I do wonder who’s taking “advantage” of whom, and the altruistic “free” check must certainly be a good earner during a quiet time of year. :D
Click to expand...

Adding to the above. My GSA was in for a fuel strip a couple of years ago, they did a free safety check, told me the rear pads were nearly worn out, front were 50% worn and should be replaced soon.
It then went in for another fuel strip a year and 14.000 or so miles later the free safety check said that all my pads and discs were fine. The bike still had the same pads in it still that were in there the last time it was in.
Oh how I laughed. I may have mentioned it here when it happened. Unbelievable.
Btw I've now had 10 fuel strips fitted, though there's nothing wrong with them. Lol
 
When I had my 06GS I replaced the rear disc at 3.5mm after 29k - both fronts at that stage around 4.2mm so a pronounced bias in wear towards the rear.
 
I think we need to get Tripleblack and his lawyer on this case as we all (me included) seem to be ignoring the manufacturer's recommendations :augie
 
Our Mini brake pad warning lights came on to say the rear pads needed to be replaced. When I took the wheels off to do this the pads were only worn by 50% compared to new. I didn't replace them and am disappointed with BMW for setting the warning light to illuminate when they're only 50% used. Most owners would simply pay huge amounts to have them replaced
 
My fronts wore well beyond bmw limit before i replaced. Not at all warped - this is a greater risk for thinner discs as there is less material to dissipate heat.

Unever wear on fronts - does one or more of the caliper pistons needs to have seals and seats cleaned up?
 
NicD said:
My fronts wore well beyond bmw limit before i replaced. Not at all warped - this is a greater risk for thinner discs as there is less material to dissipate heat.

Unever wear on fronts - does one or more of the caliper pistons needs to have seals and seats cleaned up?
Click to expand...

We are talking thousands of an inch here so the heat dissipation doesn't come into it and anyway it's more about the surface area available for cooling which doesn't change with wear.

If you can squeeze the brake hard then release and can still rotate the wheel freely it's unlikely there is a sticking piston but, it's just possible but unlikely a piston is seized solid
and not moving.The only way you will see that is to remove the pads and by blocking one piston so it can't move far try to pump the other out; if it does, return it, then try the
other repeating until you have checked them all. If one is seized it wont pump out or at least will take a lot more pressure on the lever to shift it.
 
Steptoe said:
I get countless customers in winter who’ve been and taken “advantage” of BMWs day dealers “Free winter safety check” and have been told their discs are worn and dangerous...... and they aren’t. I do wonder who’s taking “advantage” of whom, and the altruistic “free” check must certainly be a good earner during a quiet time of year. :D
Click to expand...

As a professional, at want point do you recommend replacing discs? Only when warped/damaged? When below (say) 1mm below minimum specified thickness? Mine are below min thickness but otherwise perfect & if I can safely avoid spending £100's that'd be great
 
UturnTony said:
We are talking thousands of an inch here so the heat dissipation doesn't come into it and anyway it's more about the surface area available for cooling which doesn't change with wear.

If you can squeeze the brake hard then release and can still rotate the wheel freely it's unlikely there is a sticking piston but, it's just possible but unlikely a piston is seized solid
and not moving.The only way you will see that is to remove the pads and by blocking one piston so it can't move far try to pump the other out; if it does, return it, then try the
other repeating until you have checked them all. If one is seized it wont pump out or at least will take a lot more pressure on the lever to shift it.
Click to expand...

No, no, and no. Then yes
 
Thanks all. rear has been picked up as slight fluctuation in last 2 or 3 MOTs so I was going to change when pads next need doing. Fronts I will have a clean of the calipers and all should be well. Ball joint has a new boot just waiting for me to fit it.
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
You must log in or register to reply here.

Similar threads

rustychain
Warped rear disc
Replies
13
Views
397
rustychain
rustychain
Gelandestrasse
320mm brake disc source
Replies
7
Views
363
MartinK
Brake Failure Warning Light + Error codes 5DA0 & 5DA1
Replies
15
Views
621
gazza12adv
gazza12adv
er-minio
Where to (quickly) find disc brake shims?
Replies
9
Views
829
er-minio
er-minio
iangough
2004 GS Top Speed Degradation
2 3
Replies
41
Views
1,816
iangough
iangough


Back
Top Bottom