Go Back   The 75 and ZT Owners Club Forums > The 75 and ZT Owners Club Forums > Technical Help Forum
Register FAQ Image Gallery Members List Calendar Mark Forums Read
Notices

Reply
 
Thread Tools Display Modes
Old 5th August 2022, 12:58   #1
Retap
Loves to post
 
MG ZT-T CDTi

Join Date: Sep 2020
Location: Lincs
Posts: 290
Thanks: 73
Thanked 51 Times in 44 Posts
Default Front Brake disc groove query

Hi all its been a while

Just changed front pads and discs on Nigel it was overdue and has resulted in restoration of great braking performance.

The only oddidty i keep puzzling over is this edge groove machined out on one of the Eicher discs, only on one disc though not both??? see photo below. The discs that came off did not have this any ether....

At first I worried this loss of material from the edge of the disc may cause inbalance but its closer to axle centre so maybe not to bad still a slight inbalance but still puzzling what it is. My only real rational is a wear marker but why not machine this on both discs then or evenly around the circumference to keep it balaned? Could this groove actuaally be the factory balancing process of the disc? Do we think this is a flaw or seconds reworked part?

Hmmm, any thoughts?


__________________
ZT-T Mk2 Jobs to do:

Renew auxiliary drive belt # Replace driver door lock actuator # Refurbish wheels
Retap is offline   Reply With Quote
Old 5th August 2022, 13:45   #2
Popcorn
Loves to post
 
Popcorn's Avatar
 
55 cdti tourer slush box executive grill

Join Date: Feb 2022
Location: Sheffield
Posts: 372
Thanks: 40
Thanked 85 Times in 72 Posts
Default

Never seen that before, I would guess at it being for balance but wow that disc was way out if that's what it's for
Just done a little search on Google apparently it's a disc wear indicator
https://www.pistonheads.com/gassing/...&t=720952&i=20
Just scroll down and all is revealed.

Last edited by Popcorn; 5th August 2022 at 13:52..
Popcorn is offline   Reply With Quote
Old 5th August 2022, 13:53   #3
Retap
Loves to post
 
MG ZT-T CDTi

Join Date: Sep 2020
Location: Lincs
Posts: 290
Thanks: 73
Thanked 51 Times in 44 Posts
Default Never seeen it befpore

The old discs where well ready i reckon a good 1/8" was gone they where mentioned in last mot so planned to do them at this time but the wear on th eold discs was not far off these grooves in the new disc but i to have not seen it before and found it odd especially as just seems to be machined out on one of the discs and not both of them.


EDIT


Strange the disc wear indicator is only machined on one disc i will have to recheck that next time the wheels come off.
__________________
ZT-T Mk2 Jobs to do:

Renew auxiliary drive belt # Replace driver door lock actuator # Refurbish wheels
Retap is offline   Reply With Quote
Old 5th August 2022, 14:30   #4
maxi_crawf
Posted a thing or two
 
maxi_crawf's Avatar
 
R75 Saloon Conn CDT SE, MG ZT190+

Join Date: Nov 2006
Location: Kingston-upon-Hull
Posts: 1,960
Thanks: 823
Thanked 426 Times in 274 Posts
Default

I've always assumed it was to balance the disc, I have a set of new rears to fit on my 190 and one of them has the same bit (more or less) machined out of the edge.
maxi_crawf is offline   Reply With Quote
Old 5th August 2022, 15:58   #5
daveo138
Gets stuck in
 
daveo138's Avatar
 
Rover 75 Tourer

Join Date: Mar 2022
Location: Chesterfield
Posts: 616
Thanks: 206
Thanked 69 Times in 53 Posts
Default

Hard to tell from the photo, but it doesn't look like a machined finish.
daveo138 is offline   Reply With Quote
Old 5th August 2022, 18:56   #6
Popcorn
Loves to post
 
Popcorn's Avatar
 
55 cdti tourer slush box executive grill

Join Date: Feb 2022
Location: Sheffield
Posts: 372
Thanks: 40
Thanked 85 Times in 72 Posts
Default

Looks like proper rough ar$€d grinding,if my surface finish was like that I'd get the sack you can see where the wheel has bounced
Popcorn is offline   Reply With Quote
Old 5th August 2022, 19:27   #7
Retap
Loves to post
 
MG ZT-T CDTi

Join Date: Sep 2020
Location: Lincs
Posts: 290
Thanks: 73
Thanked 51 Times in 44 Posts
Default

i dont like it but they could only be bothered to mall one disc so yay
__________________
ZT-T Mk2 Jobs to do:

Renew auxiliary drive belt # Replace driver door lock actuator # Refurbish wheels

Last edited by Retap; 5th August 2022 at 19:32..
Retap is offline   Reply With Quote
Old 5th August 2022, 20:35   #8
Ducati750cc
Loves to post
 
Rover75 tourer

Join Date: Jun 2018
Location: Ashton
Posts: 428
Thanks: 121
Thanked 206 Times in 145 Posts
Default

Quote:
Originally Posted by Retap View Post
Hi all its been a while

Just changed front pads and discs on Nigel it was overdue and has resulted in restoration of great braking performance.

The only oddidty i keep puzzling over is this edge groove machined out on one of the Eicher discs, only on one disc though not both??? see photo below. The discs that came off did not have this any ether....

At first I worried this loss of material from the edge of the disc may cause inbalance but its closer to axle centre so maybe not to bad still a slight inbalance but still puzzling what it is. My only real rational is a wear marker but why not machine this on both discs then or evenly around the circumference to keep it balaned? Could this groove actuaally be the factory balancing process of the disc? Do we think this is a flaw or seconds reworked part?

Hmmm, any thoughts?


It's for balancing ����


https://www.youtube.com/watch?v=p8mfw3WYBAM


And how it's done.


https://www.youtube.com/watch?v=SS12QOByiN8
__________________
Common sense isn't a gift, it's a punishment because you have to deal with everyone who doesn't have it.

Last edited by Ducati750cc; 5th August 2022 at 20:46..
Ducati750cc is offline   Reply With Quote
Old 6th August 2022, 08:24   #9
Ducati750cc
Loves to post
 
Rover75 tourer

Join Date: Jun 2018
Location: Ashton
Posts: 428
Thanks: 121
Thanked 206 Times in 145 Posts
Default

Quote:
Originally Posted by Popcorn View Post
Looks like proper rough ar$€d grinding,if my surface finish was like that I'd get the sack you can see where the wheel has bounced

You would have to sack a very, very expensive machine.


I suppose the manufacturers are only interested in that is balanced, not the finish of the groove.
__________________
Common sense isn't a gift, it's a punishment because you have to deal with everyone who doesn't have it.
Ducati750cc is offline   Reply With Quote
Old 6th August 2022, 12:30   #10
Retap
Loves to post
 
MG ZT-T CDTi

Join Date: Sep 2020
Location: Lincs
Posts: 290
Thanks: 73
Thanked 51 Times in 44 Posts
Default

Its a lot of material to remove from the disc and i dont have much confidence in the manfacturer process especilly when considered the other disc has no groove so one would like to assume it was made perfectly balanced but has been through the balancing test and did not need balancing in that expensive machine. Then in my mind as a former production manager it leads to a question of quality and process if two discs from the same production process have such a difference. I am going to drive Nigel tho regardless and we are going to stop when we need to right where need to.
__________________
ZT-T Mk2 Jobs to do:

Renew auxiliary drive belt # Replace driver door lock actuator # Refurbish wheels
Retap is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 09:29.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Copyright © 2006-2023, The Rover 75 & MG ZT Owners Club Ltd