Rear brake upgrade from drums to discs!
For Polo 6R hatchback( not Polo sedan/Vento)
A long post!!!
Background:
The motivation for this upgrade came to me after I installed oem bixenons+ AFS. The Indian Polo's were never offered rear disc brakes from the beginning till the end. Also Bixenons or led headlights were also never offered. Subsequently, the rear axle of Indian polo's neither had ears for rear disc callipers nor the AFS mount(stabiliser, PR8Q3) for AFS sensor. But fortunately the Polo's sold here from MY 2010 to MY 2013 had the rear axle with ears for mounting disc callipers as well as AFS mount even though drums were installed on such axle. ( part no:
6R0 500 051B)
From MY 2014, the rear axle for Polo was replaced with part no:
6RG 500 051( PR1KH+ 8Q0) a regular axle without ears and stabliser.
My polo being MY 2016, the rear axle didn't had AFS mount, so after installing OEM bixenons, I had to weld a metal on rear axle to hook the AFS sensor pole. Due to the poor placement of weld, the load on rear axle was not properly communicated to AFS sensor hence AFS was not working perfectly. To fix this inconvenience, I bought the used rear axle and refurbished it( new one is ridiculously expensive) from previous generation Polo. At the same time I took the opportunity to upgrade the rear drums to discs(PR1KT) as the option is now available.
Parts:
1)
Rear axle parts:
- Rear axle
6R0 500 051B (PR-0N2/K8G)
- Axle hub with wheel bearing -
6Q0598611 (2 no)
Bought aftermarket from OE manufacturer
FAG-713-6104-90
- Stub axle
6Q0 501 117 (2 no) used old ones from axle as they were in good condition.
Axle rubber bushes-
6R0501541A (2no) Replaced the old ones with new. Need special VAG tool to press these bushes into axle or need hydraulic press.
- Rear spring washer(underlay)
1J0 512 109(2no)
- Axle mounting bolts-
N10409902(2no)
-Self locking collar nuts-
N10106402(2no)
2) Rear disc brake parts:
- Brake calliper left-
6R0615423
- Brake calliper right-
6R0615424
- Calliper carrier left-
6R0615425
- Calliper carrier right-
6R0615426B
- Callipers repair kit-- 1 set( aftermarket)
- Rotors(230x9mm)
2Q0615601H (2no)
- Pads-
5K0698451E (1set)
- Brake cables
6R0609721C(1644mm, 2no)
- Brake hose rear left
6R0611763B
- Brake hose rear right
6R0611764B
- Dust cover left
6R0 615 611
- Dust cover right-
6R0 615 612
( dust cover part numbers ending with alphabets A/B/C/D are for 254mm disc, will be too big for 230mm)
- Parking brake for disc-
6Q0711303AG
- Parking brake return spring left--
7H0615295A
-Parking brake return spring right--
7H0615296
- Brackets for fixing handbrake cable--
1H0609747(2 no)
- Brackets for holding brake cables--
6Q0609639B(left),
6Q0609640B(right)
- Bracket for brake cable--
6R0609651(2no)
- Bolts
a)
N10648301( M6x16) -- 2no
b)
N90740302( M10x1,25x30) -- 4no
c)
WHT003250(M8x22)-- 4no
Sourcing and assembling the parts:
Rear axle and its components: I bought the used rear axle undamaged in excellent condition from scrap market here for a cheap price, and got it refurbished from a mechanic friend. The new axle as I mentioned above is very expensive around 1000€ just for bare axle!!
I decided to by new hubs with bearings and used stub axles from axle I bought, as they were in good condition. The OEM hubs are very expensive, so decided to buy aftermarket from OE manufacturer FAG. 2 sets including shipping from eBay Germany costed me less than 1 set OEM. VW asks too much just for 2 alphabet engraving.
Brake parts: With the help of iichel, I could able to source callipers with carriers, callipers repair kit, brake cables, hoses, springs and handbrake. Remaining parts I ordered from eBay and from my dealer.
My country Post has been savage lately, damaging the parts and have lost few.
I noticed a missing glide pin from one of the calliper carrier!
Unfortunately the caliper glide pins are not seperate part, they are part of calliper carrier and don't have seperate part number! But luckily the OE manufacturer TRW sells glide pin repair kit as aftermarket. I bought such a kit from eBay.
Now if we notice the glide pins carefully in above picture
, 1 pair is different from the other by design!
Now the question arose, which pin goes where into the carrier? According to the manufacturer, if the callipers are installed rear facing.. the glide pin with 3 horizontal circles goes on top and vertically sliced pin goes at the bottom& vice-versa if the callipers are installed front facing. For 6R, the callipers are installed rear facing so I followed the former. See below(credits to author from drive2).
Pictures of parts and installation:
The heavyduty axle with drums from 1st gen Polo sold here. bought:
The old OE hub, replaced with new.
Stub axles from old axle, retained
New rubber bushes:
New rear spring washers(underlay):
Axle mounting bolts+nuts:
Brake callipers and carriers: Refurbished using repair kit and repainted to red.
Rotors and pads:
Dust covers:
Brake fluid:
Handbrake (drum vs disc) not my picture, I forgot to click mine. Credit to respective owner from Drive2.
Brake cables, hydraulic lines, and remaining parts all assembled together:
The stock rear axle removed, comparing with new refurbished axle. I forgot to take the pictures of axle swap. Followed the workshop manual instructions.
Installed the rear disc setup according to the below scheme from workshop manual:
Used my stock ABS sensors
Finally!!!
Brake bleeding, wheel alignment and balancing and ABS firmware upgrade:
After complete installation, I took the car for a long test drive and honestly speaking I was bit disappointed with the outcome, for a moment I felt my previous drums were much better!! There was too much Sponginess and braking was pathetic. Something was not right.. thanks to iichel, he recommended to rebleed the brakes again to remove remaining air in the lines. After rebleeding with proper tools second time the sponginess reduced significantly! One more significant change I noticed was that ABS was kicking in way too early! it was so embarrassing
Finally I pulled up the ace under my sleeve to fix the brakes. I knew that the abs coding has to be changed from rear drums to disc, I didn't do it purposely for testing purposes and my stock abs firmware doesn't accept rear disc coding anyway. After driving few hundred kms I decided to flash my abs firmware to updated one and code the rear discs.
Flashed new and updated abs firmware using ODIS-E:
Successfully flashed.
The new firmware accepted the coding for rear disc, so I coded rear drums to disc(230mm)
Byte 2 from 24 to 28 and byte 10 from 24 to 14. The new firmware accepts coding for front disc upto 288mm and rear disc upto 230mm( tested). My old BN firmware refused to accept any coding except 256mm disc front and 200mm rear drums.
My final abs coding( 254mm disc front+ 230mm disc rear):
After firmware update and coding change, I drove close to 1000km and I will say correct coding does make a lot of difference!! abs doesn't kick in early now!! and also bite has improved. The front nose dive has also significantly reduced during high speed braking.
And also will add a note that, I do recommend changing the handbrake lever from drums to disc type.. as I felt the disc one grips the rotors more firmly with less pull than the drum type. VW designed them differently not without a reason! Overall I would say my drums were not bad but discs are good.
Final impressions:
Honestly speaking, the improvement in braking is not extraordinary for the kind of money and efforts you put. But on the brighter side, yes high speed braking has vastly improved, aesthetically look better than drums and most importantly my AFS issue was fixed to factory level! which was the very reason for axle change and discs just followed... and why not
a win-win situation.
With this upgrade, I conclude mods on my little 6R. Now I will concentrate on T-roc mods.. another exciting journey
I wrote this post in detail with lot of pictures so can help someone. My heartfelt thanks to iichel for helping me to source critical parts.
A special thanks to my dear friend Sheetal for motivating me and
also many thanks to CNK, Nikhil and Slavik for all the suggestions/help..
Namaste