W204 front disc replacement tips

[190]

Just fitted new discs which should be a straightforward and relatively quick job with the right tools.

First issue is identifying the correct discs. Some web sites identified 295 mm discs and others 288 mm and some listed both sizes. So I measured mine carefully and they were 288 mm. I then abandoned any idea of buying from a supplier that couldn't identify the correct discs. I did what I always do and that was go to the disc manufacturers web site, in this case Bosch to check for the correct part no.

Offside first, Disc retaining screw is a Torx T 30 and it came out reasonably easily. Then caliper off leaving the carrier to remove only to find the bolts have an 18mm head which is a non preferred size. My socket set and spanners jumped from 17mm to 19mm, not that you would shift them with a spanner. So off on the bike to buy an 18mm socket for £1.69 from B&Q. Not where I would normally buy tools but they had one when I needed it.

Nearside retaining screw wouldn't budge and seemed to be made of cream cheese because it easily stripped it's splines. Drilling the head off was so easy it really must have been made of soft metal. New screws came with the discs. Job done in 3 hours including the trip to buy a socket. With the right tools and no problems it could be done with ease in an hour and a half. Why do garages charge so much ?

 

[DSM10000]

Just fitted new discs which should be a straightforward and relatively quick job with the right tools.

First issue is identifying the correct discs. Some web sites identified 295 mm discs and others 288 mm and some listed both sizes. So I measured mine carefully and they were 288 mm. I then abandoned any idea of buying from a supplier that couldn't identify the correct discs. I did what I always do and that was go to the disc manufacturers web site, in this case Bosch to check for the correct part no.

Offside first, Disc retaining screw is a Torx T 30 and it came out reasonably easily. Then caliper off leaving the carrier to remove only to find the bolts have an 18mm head which is a non preferred size. My socket set and spanners jumped from 17mm to 19mm, not that you would shift them with a spanner. So off on the bike to buy an 18mm socket for £1.69 from B&Q. Not where I would normally buy tools but they had one when I needed it.

Nearside retaining screw wouldn't budge and seemed to be made of cream cheese because it easily stripped it's splines. Drilling the head off was so easy it really must have been made of soft metal. New screws came with the discs. Job done in 3 hours including the trip to buy a socket. With the right tools and no problems it could be done with ease in an hour and a half. Why do garages charge so much ?

Garages have overheads to PAY.

Staff wages, utility bills, business rates, equipment costs etc etc etc.

Not that difficult to see why Garages cost more than DIY.

 

[vijilants]

Nearside retaining screw wouldn't budge and seemed to be made of cream cheese because it easily stripped it's splines. Drilling the head off was so easy it really must have been made of soft metal.

I had the same issue with my previous W204...the torx screw rounds off soo easily.

Note that if a garage does the job properly they should dismantle the caliper sliding pins, clean them and lubricate them before reassembly. If this isn't done the caliper stops moving and causes uneven wear and braking.

 

[Gazwould]

288mm is a shockingly small diameter front brake disc size .

 

[DSM10000]

288mm is a shockingly small diameter front brake disc size .

Why?

 

[Gazwould]

Because...

 

[alexanderfoti]

We charge 0.9 hours front discs/pads and rear pads (0.9 as well).

That includes getting it on the ramp wheels off, cleaning hub etc. I feel we are competitive. Its a nice easy job to do at home as well, not much to go wrong.

 

[markjay]

288mm is a shockingly small diameter front brake disc size .

Why?

Because...

When Abraham Lincoln was asked, "How long do you think a man's legs should be?" he replied, "Long enough to reach the ground."

Discs should be big enough to stop the car without overheating or brake fade... bigger grooved/drills discs look the part, but if the car already stops as it should, they won't make it stop any better (for the type of car and type of driving).

 

[190]

Discs should be big enough to stop the car without overheating or brake fade... bigger grooved/drills discs look the part, but if the car already stops as it should, they won't make it stop any better (for the type of car and type of driving).

The original ventilated discs lasted 73K and were only just down to the wear limit so I think they are big enough for the job.

Interestingly while I was searching for the correct discs I discovered W204's in some markets came with solid front discs. What would you make of them Gazwould !

 

[markjay]

The original ventilated discs lasted 73K and were only just down to the wear limit so I think they are big enough for the job.

Interestingly while I was searching for the correct discs I discovered W204's in some markets came with solid front discs. What would you make of them Gazwould !

Well, if they didn't fade.... then they were up to the job

 

[Gazwould]

My thoughts on the W204 .

I remember another manufacturers forum thread from 2009 that ran for 11 years that was a 288mm to 312mm upgrade that came from the larger V6 diesel engine , this particular conversion was easy because it was just the 312mm caliper carriers often sourced used and new 312 discs required and the existing calipers and pads were the same as the V6 .

11 years shows you how much disgust there was with the 288mm .
The 312mm even with unbeded pads gave an instant improvement .

Now even 295mm on a W204 are silly because the rear are 300mm , hmmmmm .

The bigger Merc diesel V6 as before has the answers or at least where it should begin , the 3.0 V6 350 CDI has 322mm but it's calipers , carriers , pads , and discs .

It doesn't end there either as a small lighter Merc sports car gets even bigger fronts .

 

[markjay]

...11 years shows you how much disgust there was with the 288mm .
The 312mm even with unbeded pads gave an instant improvement...

Improvement in heat way? Stopping distance? Brake fade? Brake feel and bite? Performance before warming-up?

 

[Gazwould]

That initial brake feel and bite.

 

[markjay]

That initial brake feel and bite.

This has to do more with the friction materials than the disc size.

 

[Gazwould]

Definitely not , you can't beat the physics of leverage .

It's mainly the spacing of the caliper with bigger discs the caliper gets placed further out making more leverage torque .