How to retro-fit the rear subframe harmonic damper from the Audi A3 Saloon (2013->)

[EEeegolf]

I don’t have a std Golf here to compare. But I have quite a lot of space above the subframe. No idea if it’s enough

 

[golfdave]

I don’t have a std Golf here to compare. But I have quite a lot of space above the subframe. No idea if it’s enough
View attachment 283351

Ah right you have clearance there....but I would also look at clearance of the hollow tube part of the subframe thats near your battery....

 

[EEeegolf]

If I would be sure the noise would be reduced. I'd do this for sure. But if it doesn't help much it's a real bugger. After all it ivolves some money and a lot of work. I don't really care about comfort (vibrations) as the car is already extremely comfortable. Due to the low center of gravity the e-Golf has really soft springs. I also run tires with high sidewalls (225/55R17).

 

[golfdave]

If I would be sure the noise would be reduced. I'd do this for sure. But if it doesn't help much it's a real bugger. After all it ivolves some money and a lot of work. I don't really care about comfort (vibrations) as the car is already extremely comfortable. Due to the low center of gravity the e-Golf has really soft springs. I also run tires with high sidewalls (225/55R17).

Wrong sized tyres ...you should have 225/45R17 (factory option)....having 225/55R17 means that the rolling circumference will make the speedo out by 6.36% (compared to the factory 16inch) according to online calculators...

You should have got 225/50R17....(out by 3.96%) or kept the 205/55R16 size (standard fit for e-Golf)

 

[Cuzoe]

Well... "wrong" sized is subjective isn't it? Could just be the tire size/look they wanted .

 

[EEeegolf]

It's definitely not by accident. And the speedo is now more accurate than stock. Most VW's are ~6% off.
Bigger tires (diameter - not width), mean more comfort and better rolling resistance. For the previous cars longer gear ratios also improving fuel consumption. Electric doesn't make a difference.
I actually passed these over from My Alhambra to Touran and now Golf. Even winter tires are 215/55R17
Only case I'd put stock diameter tires is if I sell the car

 

[golfdave]

It's definitely not by accident. And the speedo is now more accurate than stock. Most VW's are ~6% off.
Bigger tires (diameter - not width), mean more comfort and better rolling resistance. For the previous cars longer gear ratios also improving fuel consumption. Electric doesn't make a difference.
I actually passed these over from My Alhambra to Touran and now Golf. Even winter tires are 215/55R17
Only case I'd put stock diameter tires is if I sell the car

How do you know your speedo was "out"...comparing it to a standard GPS won't work as they are usually "out" on speed.....

More/deeper sidewall equals more comfort .....& to increase sidewall depth whilst retaining the same overall rolling radius you reduce the alloy rim diameter..

Better/less rolling resistance is gained with narrower tyre width... (all other rubber/tread factors being equal).

Also the narrower the tyre the less aero drag...as the frontal cross-sectional area is reduced...Why do you think the factory spec for the e-Golf & 1lt Bluemotion version are all narrow tyre widths??

The "winter tyres spec alloy program" from VW Germany for the MK7 Golf & most of the MQB cars are:-
195/65R15
205/55R16
205/50R17
225/40R18

Touran is:-
195/65R15
205/55R16


P.S. "Normal factory sizes" for MK7 & MK7.5 Golf are:-
195/65R15
205/55R16
205/55R17 (Alltrack only)
225/45R17
225/40R18
235/35R19

 

[ReadTheBook]

Great data @EEeegolf! Cool that someone finally measured this.
I tried to get some measured data from a friend after an engine treatment to post here but even though he recorded it, he never came through with the final data.

Having done it previously on 2 of my MK7s, we just got an MK7.5 Spektrum R car and came to this thread to check to see about AWD cars and this mod. Nice to read just in today’s updated posts that it’s sort of “built in”.

 

[EEeegolf]

Dave. The GPS are actually quite good. At least what we have here. If yours is "out" it might be time to update. Momentarily they can be off but average over a reasonable time is good. I also use professional measurement equipment (VBOX) for work and they confirm even iPhone GPS is okay for speed. Speaking about speed I also used PEiseler fifth wheel, Datron microwave and optical sensors. GPS is by far the best and used by all industry nowadays. (except Audi who uses Peiseler - likely the last ones not in a museum).

Your "thumb rules" are right.
Additionally you can increase sidewall maintaining the rim diameter and increasing tire diameter.
Also a bigger diameter tyre reduces rolling resistance all other things being equal.
I know very well the standard sizes. Your last one has a typo.

Next time I change I might go for 195/60 or 205/60 R17

Readthebook. Thanks. I try to validate all I do.

My next project will likely be the flat bottom at the rear. For this I will measure RR and Cd before and after installing it.

 

[mrmatto]

I just mounted the damper today. Took 3 minutes including some photos.
Next I went to my std measuring straight. Pretty smooth asphalt and cc at 82 km/h.
View attachment 283292

Clear difference in the resonance at 120 Hz.
Then I selected a rough road as well. Also asphalt but quite rough. 41 km/h
View attachment 283293Again a reduction in the resonance. A bit lower frequency as speed was lower too.

I must admit I was surprised as the effect was bigger than expected. Made the investment totally acceptable. This was on a 2020 e-Golf with additional sound deadening added.

I see you have the same hum at 210hz or thereabouts that I have. Part of the rear subframe resonates like crazy under certain conditions. Unfortunately unaffected by this particular mod.

 

[golfdave]

Dave. The GPS are actually quite good. At least what we have here. If yours is "out" it might be time to update. Momentarily they can be off but average over a reasonable time is good. I also use professional measurement equipment (VBOX) for work and they confirm even iPhone GPS is okay for speed. Speaking about speed I also used PEiseler fifth wheel, Datron microwave and optical sensors. GPS is by far the best and used by all industry nowadays. (except Audi who uses Peiseler - likely the last ones not in a museum).

Your "thumb rules" are right.
Additionally you can increase sidewall maintaining the rim diameter and increasing tire diameter.
Also a bigger diameter tyre reduces rolling resistance all other things being equal.
I know very well the standard sizes. Your last one has a typo.

Next time I change I might go for 195/60 or 205/60 R17

Readthebook. Thanks. I try to validate all I do.

My next project will likely be the flat bottom at the rear. For this I will measure RR and Cd before and after installing it.

I did state "standard GPS"...VBOX & other "pro" setups are more accurate....but again its usually only when used on a flat, level, straight road with 100% clear sky above, i.e. no trees etc.....& when it has 4 or more satellites locked to get 100% accuracy.

I prefer to tell people the official sizes & to keep within the factory design rolling diameter...from what I understand (right or wrong) in certain countries you wouldn't be able to run your tyre sizes as NOT to factory specs (standard or optional fit tyres)...car insurance & annual testing/inspection requirements come to mind

I placed the tyre sizes for the benefit of all who see this thread...

I saw the typo 25 instead of 35....thanks...

People have made up big covers for the huge uncovered rear void on the e-Golf....I think some have managed to fit the Versus rear diffuser, just I was concerned if there was enough clearance where it joins the front of the rear subframe where the rear of the battery pack cover is...I can't remember the outcome if it fitted 100% no problem or if there were modifications to be made...I think the info is in the big skid tray thread..

Anyway we are way off topic on this thread.....which is about retro-fitting the harmonic damper to the rear sub-frame....your sound measurement charts are much appreciated...

 

[Jachas]

Speaking about swapping rear subframes from bushless, tubular style to AWD style with bushing. Maybe A3 8V rear subframe from 07.07.2014 onward may fit? As its used on FWD cars too (US 1.8T A3 8V, or any EU A3 8V with multilink)

From my little research, it look like they adopted a revised rear subframe from EU passat B8, as subframe from A3 strats with 3Q0 part number (the same as passat B8 rear subframes) instead of 5Q0 (bushless style subframe). Parts number for subframe its the same beteen A3 8V (3Q0 505 315J/K/L repaced by 3Q0 505 235 AH) and B8 Passat (3Q0 505 235 T/AA/AC replaced by 3Q0 505 235 AH).

It should fit FWD golf, as floorpan in FWD vs Quattro A3 8V is different (lower in FWD, higher in Quattro, as in hatch golf)

 

[golfdave]

Speaking about swapping rear subframes from bushless, tubular style to AWD style with bushing. Maybe A3 8V rear subframe from 07.07.2014 onward may fit? As its used on FWD cars too (US 1.8T A3 8V, or any EU A3 8V with multilink)

From my little research, it look like they adopted a revised rear subframe from EU passat B8, as subframe from A3 strats with 3Q0 part number (the same as passat B8 rear subframes) instead of 5Q0 (bushless style subframe). Parts number for subframe its the same beteen A3 8V (3Q0 505 315J/K/L repaced by 3Q0 505 235 AH) and B8 Passat (3Q0 505 235 T/AA/AC replaced by 3Q0 505 235 AH).

It should fit FWD golf, as floorpan in FWD vs Quattro A3 8V is different (lower in FWD, higher in Quattro, as in hatch golf)

The Passat subframe is basically the same as the Golf subframe, just the addition of the bushes which the main bolts go through to the bodywork...You could swap them if you want..I never mentioned due to cost, time to do the work, & wheel/suspension alignment cost -vs- the benefits!...

 

[mrmatto]

Just a note: This fits the mk8 and similarly reduces road rumble. Not a night-day difference but it’s noticeable.

It’s weird it still wasn’t included despite all the additional steps VAG took to reduce NVH in the mk8.

Seems like we are missing a key detail…

 

[golfdave]

Just a note: This fits the mk8 and similarly reduces road rumble. Not a night-day difference but it’s noticeable.

It’s weird it still wasn’t included despite all the additional steps VAG took to reduce NVH in the mk8.

Seems like we are missing a key detail…

Same reason why it was designed originally for the MK5 Golf (PQ35 platform) subframe & has the part designation "1K0" & never fitted...It all depends on the NVH of that particular bodyshell & how it resonates with the subframe. Also is the car a premium brand in VAG & does the buyer expect less NVH....This is why the first car to have it fitted from factory was the MQB Audi A3 saloon.

Cost cutting everywhere....so much so VAG shot itself in the foot over dieselgate & the defeat software...It would have been far cheaper to have fitted all the existing undertrays from the "bluemotion" cars to all the other trim variants as the "collective" lessening of the combined emissions would have got the "group" emissions lower & in real life for the consumer......instead of having to fudge a stupid test....