DIY: A tiny bit more stiffness from the stock rear ARB

[brad1.8T]

I have a 2007 build 118tsi.

 

I bought a MKV Golf GTI sway bar for the price of a few cups of coffee.  It's not a huge upgrade from stock.  19.6mm up to 21.6mm give or take 0.1mm.

What I did notice was how much flat was on the lever arm & it got me thinking about the aftermarket  Whiteline adjustable RSB I had on my Subaru Liberty/Legacy

I decided to drill an additional mount hole 20mm shorter along the bar.  This effectively reduces the moment arm & makes the bar stiffer.

I was concerned about drilling a hole in what should be spring steel but the 3mm pilot hole & 10.4mm clearance hole went through like a hot knife through butter, so I doubt it is proper spring steel.

There's possibly room for a 3rd hole if you felt so inclined or make the initial spacing 30-40mm.

 

I've had a look at the Front ARB & there isn't as much room to play with there - the edge of the new hole would kiss the original hole.

 

I has made a difference though it's not as ,arked as when I fitted the Eibachs or the Konis.  It's more what I call tuning than modding.

[rob_e]

nice cheap mod. 

 

how does it drive with that fitted up?

[Stuarted]

Yup, a neat mod which provides a simple and quick way of changing the effective stiffness of the bar - and back again, any time you want.

Anorak note: the torsional stiffness of a bar is proportional to the fourth power of its diameter, believe it or not, so even a small change in the diameter makes a massive difference to the stiffness whereas changing the effective arm length in the way described above has only a directly proportional effect - easier to measure and assess.

[19.6mm dia > 21.6mm dia = almost 50% (well, 47%) increase in torsional stiffness.]

[brad1.8T]

Thanks Stuarted for the numbers.  I knew it was more than you'd expect (eg: a lot of people would think that plus 2mm on 20 would be +10% stiffness).

 

rob_e.

the overall change is noticeable but not ground breaking - on a stock car you'd be pretty happy but I've got Eibach wagon springs in my sedan so the back end only drops about 5mm when I fill with fuel (used to drop 20mm on OEM springs) & I'm on Koni Yellows set half a turn off soft + 17s with RE050A Bridgestones which have the sidewall compliance of a brick.  It's safe to say the chassis is planted without being uncomfortable.  It corners well but if you do something silly & lift off in a hot corner the back end will step out on you & then the ESP takes over & ruins the fun.

 

I've had adjustable RSBs on stock suspension before & the change in position is noticeable.

[jeallen01]

Brad

 

Many thanks for the info - will try to get my hands on one of those GTI rear ARBs, and drill the holes before I fit it.

 

Question: I realise that new ARB bushes were required, but were the original ARB bush mounting brackets OK, or did you have to use the ones from the Golf GTI MkV?

 

I had a Whiteline adjustable bar on the rear of the old Golf estate, and you could certainly feel the differences when you changed between the various positions, but I suspect that the equivalent bar for the Skoda (is there one?) would probably start off a bit too stiff at the minimum position for my needs (and my back!).

Edited 31 May, 2016 by jeallen01

[brad1.8T]

I used the original D-bush bracket off the Octavia.  Used the D-bushes that were already fitted to the rear GTI bar.

 

Golf GTI bar is the same diameter as Octavia vRS - 21.6mm

 

Whiteline do a 22mm solid bar with no adjustment and a 24mm (solid) adjustable bar.  There are plenty of other RSB suppliers for the GTI as well.

 

You can go too heavy on the rear and ruin the balance if you don't do the front bar as well.

Edited 1 June, 2016 by brad1.8T

[jeallen01]

I used the original D-bush bracket off the Octavia.  Used the D-bushes that were already fitted to the rear GTI bar.

 

Golf GTI bar is the same diameter as Octavia vRS - 21.6mm

 

Whiteline do a 22mm solid bar with no adjustment and a 24mm (solid) adjustable bar.  There are plenty of other RSB suppliers for the GTI as well.

 

You can go too heavy on the rear and ruin the balance if you don't do the front bar as well.

Cheers for the info about brackets and bushes - that was what I had hoped.

 

I'm now looking for a GTI bar in the UK, but, whilst the dismantlers appear to have a few front bars, they don't see to have any rear ones at present, and I don't t to go the Whiteline route because of the costs.

 

I think, on the estate - and based on past experience as mentioned - fitting a GTI rear bar should be enough to sort out the slight sloppiness at that end of the car without ruining the balance (going too hard on the Golf made it very tail-happy!)

[cheshire_cat]

I think there are 4 or 5 different factory sizes on the same pattern   whilst shopping for what I could get I went from to smallest to the next one up which made a difference,   based on that I wouldn't want to go more than  2 sizes up on the rear alone  (with poly bushes)

[jeallen01]

I think there are 4 or 5 different factory sizes on the same pattern   whilst shopping for what I could get I went from to smallest to the next one up which made a difference,   based on that I wouldn't want to go more than  2 sizes up on the rear alone  (with poly bushes)

I agree - experience with the adjustable Whiteline on the Golf taught me that.

[brad1.8T]

Keep in mind OEM is hollow and the whiteline is solid - so comparing based just on diameter is fruitless.  Go with the biggest OEM you can find

 

I'll say again:

 

The GTI and VRS run the same hardware - you can look for either.

[jeallen01]

Update

 

Found a VAG P/N for the 21.7mm bar - 1K0511409CB - still looking for a s/h one.

 

Also available aftermarket part in the UK and Europe as Meyle 100 653 0011 - about £70-£75 inc P&P to UK locations

(http://www.buycarparts.co.uk/meyle/7938482, &

http://www.ebay.co.uk/itm/100-653-0011-MEYLE-Sway-bar-fit-VW-/391396327257?fits=Car+Make%3ASkoda%7CModel%3AOctavia&hash=item5b2109ff59:g:pFEAAOSwe7BW1P1h

 

Edited 29 July, 2016 by jeallen01

[jeallen01]

Now found this list on TDIClub Forum - if you look closely you will see that there are two different wall thickness (3mm and 3.7mm) for the 21.7mm diameter bars

 

Part Number Size Use
1K0511409BA 18.5x2.5 Superceeded by 1K0 511 409 BN
1K0511409BB 20.7x2.8 Superceeded by 1K0 511 409 BQ
1K0511409BC 21.7x3 Golf Plus (Early)
1K0511409BD 18.5x2.5 A3 (AWD), TT (AWD)
1K0511409BE 20.7x2.8 Golf (AWD), Passat (AWD), A3 (AWD)
1K0511409BF 21.7x3 Golf (AWD), Passat (AWD)
1K0511409BH 19.6x2.6 Golf (AWD)
1K0511409BK 18mm Jetta, Golf (FWD)
1K0511409BL 19mm Jetta, Golf (FWD)
1K0511409BM 20mm Jetta, Golf (FWD)
1K0511409BN 18.5x2.5 Golf (FWD), TT (FWD)
1K0511409BP 19.6x2.6 Golf (FWD); Passat (FWD)
1K0511409BQ 20.7x2.8 Golf Plus
1K0511409BR 21.7x3 Eos (Early), Golf (FWD), Golf Plus (Late), Passat (FWD)
1K0511409BS 18.5x2.5 A3 (FWD)
1K0511409CA 20.7x2.8 Eos, Golf (FWD), Passat (FWD), Touran, A3 (FWD)
1K0511409CB 21.7x3 Eos (Late), Passat (FWD), Golf (FWD)
3C0511409A 20.7x2.8 Passat (AWD)
3C0511409B 21.7x3.6 Passat (FWD)
3C0511409C 21.7x3.6 Passat (AWD)
3C0511 409D 21.7x3 Passat (AWD)
3C0511409E 21.7x3.6 Passat (AWD)

See here
 

Edited 30 July, 2016 by jeallen01

[sniper29a]

ARB arm length makes more difference than diameter.

[jeallen01]

ARB arm length makes more difference than diameter.

You are probably correct (leverage effect) from  my experience but I hope that getting a GTI bar might help (currently "negotiating" with a breaker on one to see what they what they will do).

[sniper29a]

and what are you trying to achieve?

 

drilling holes in weakest part of bar is probably not very good idea

[brad1.8T]

and what are you trying to achieve?

 

drilling holes in weakest part of bar is probably not very good idea

It's not the weakest part of the bar.  How do you come to that conclusion?

 

What is trying to be achieved is more stiffness from a stock item.

 

As a qualified Automotive Engineer and qualified Mechanical Engineer with 37 years experience, I feel fairly comfortable doing what I do.

 

The GTI rear bar cost me $10, so if it breaks there's no big loss.

[jeallen01]

Brad

 

I agree with what you said - just wish the bars over here were that cheap (think around $ 70-120 Aus inc P&P)!

[brad1.8T]

Brad

 

I agree with what you said - just wish the bars over here were that cheap (think around $ 70-120 Aus inc P&P)!

Bought mine 2nd hand off a guy with a MkV Golf GTI that lived 2km from my office.

 

He was trying to clean out his garage after upgrading.  Also got a set of GTI calipers, caliper carriers, 50% pads, rotors & braided lines for $40.  They needed a lot of work to clean up (about 3 hours) but my time is my own.

 

I'm fairly ruthless when making an offer as they want to sell more than I want to buy.

 

I think you either do it cheap like I do (which requires time and flexibility) or go all out and fit aftermarket.

[jeallen01]

Morning.

 

Yesterday I managed to get a GTI Rear ARB on UK ebay - funny story in a way.

 

I must have put this one on my Watchlist a few days ago but forgot about it until I got an alert yesterday morning that the Auction was coming to an end. Anyway, I followed that up with a message to the seller to ask for the P/N to make sure I got something appropriate - so first he gives me a number which turned out to be a Front ARB (!) although the pic in the ad clearly showed a Rear one, and when I pointed that out to him he then gave the correct P/N (turned out to be 1KO 511 305 DF, which looked OK (21.7mm bar with 3mm wall thickness).

 

The minimum on-line bid price was £20 + £10 p&p, and so I then asked what about an offer of £25+ p&p to "buy it now" - but he said that he would let the auction run, presumably because he thought he had a number of other potential buyers.

 

Later on, I finally bid (£20 with a limit of £28) on it as no-one else seemed to be bidding, but had to go out before the bidding finished - half an hour later I got an ebay message to say that I had won the bar for the original minimum bid price because no-one else HAD bid , and it should be on its way to me today.

 

Moral and a lesson to the seller: - a bird in the hand is worth two in the (Anti Roll Bar) bush!  

 

PS: several other ebay suppliers appeared to have appropriate bars, but all of them failed to communicate properly, or even at all, when asked for the P/Ns of the bars they were offering - why don't people like that realise that if you don't give the info that the customer wants/needs then you won't make a sale, and if you don't really wanted to bothered with selling something then why bother to advertise in the first place  

Edited 9 August, 2016 by jeallen01

[brad1.8T]

well done!

[jeallen01]

Cleaned the "new" ARB up a few days ago  (derusted, zinc primer and then some Satin Black) - but then had a lot of trouble drilling the extra holes 20mm from the first ones (my drill bits were obviously not sharp enough but a new Dewalt HSS one did the trick).

 

This afternoon I managed to fit the new bar in about 2hrs (took it easy, kept mislaying tools etc.  ) - all the nuts/bolts came off fairly easily, but it was a bit of pig to fit the new bar because the new bushes -  which were supposed to be the right ones for that bar thickness -  were too small for the bar and I had to reuse the rather "tired" old ones which had come with it. Little bit of rubber grease helped - as did the fact that someone (could have been me last year when I changed the springs!) had put a long bolt through one of the chassis mounting holes "from the wrong end"  and so it was easy to hitch the bush clamp over that whilst I lined everything else up.(that could be a good tip for anyone else changing the Rear ARB).

 

Then went for a short blast to a place round here where I could rag it around a few corners and roundabouts - big improvement and feels much safer as the back end stays planted and the opposite front inside corner does not try to **** up into the air like it did before ! That was with the droplinks in the OEM position, and I will run it for a few days to decide if I want to try to tighten things up by moving the links to the new holes that I drilled.