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BMW 3-Series (E90 E92) Forum > BMW E90/E92/E93 3-series General Forums > Regional Forums > UK > UK Technical Forum > Bumpstops and Shocks for 25-30mm AC Schnitzer lowering springs



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      10-16-2012, 09:24 AM   #1
mob17
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Bumpstops and Shocks for 25-30mm AC Schnitzer lowering springs

Hi,

Firstly I do not know much about lowering so may ask some silly questions

I recently put some ACS lowering springs on my car, and rather naively didn't replace the bump stops.

I now want to upgrade the OEM shocks and the bumpstops at the same time. I have had some advice from a forum member over in the states, who says the E36 M3 front bumpstops and E85 Z4 rear bumpstops would be a good choice. But just wanted to know what everyone else has done with 25-30mm lowering springs? Apparently you shouldn't use OEM bump stops with lowering springs.

Regarding the shocks I am looking at 3 options. Bilstein B4s, Koni Sports Yellows or the ACS ones that come as a kit with my current springs. Am I right in thinking I should go for monotube ones?

The Bilstein ones are the cheapest at 328 shipped, Konis are 513 shipped and the ACS ones are 580 collected from Aachen, Germany LOL. It would cost me another 100 there and back but this is still cheaper than buying from ACS UK. They are a lot more expensive than the Bilstein and Konis, plus i'm sure some of that money is for the ACS branding. But then again they always go on about how they've researched into it and the springs/shocks are perfectly designed to work together and with my car AND the original bumpstops.

Can someone please clarify things for me? Am i being silly even considering going to Germany to buy ACS shocks (wouldn't mind the day out with a few friends though thrashing it on the Autobahn), or are they really that amazing? I just don't want to buy shocks which are not great for my set of springs, for which the spring rates are not published.

Many thanks

Edit: I never go tracking but may do one day. But for now I want the ride to be firmer, but i really don't want that rock hard feel. Just firmer going around corners and reduce body roll if possible.
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      10-16-2012, 12:20 PM   #2
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Going to visit Birds this week to see what they have to say.
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      10-16-2012, 02:35 PM   #3
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All issues sorted after a lengthy conversation with the brilliant Kevin @ Birds.

Mods please delete.
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      10-17-2012, 12:17 PM   #4
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Or... you could share the answer with everyone!
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      10-17-2012, 03:41 PM   #5
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Oh yeah even better! Thought it was just me who wanted to know.

Anyways Kevin said that a company like ACS would never sell springs by themselves if it required different bumpstops too, they would have included them in the package, or at minimum informed you.

I have also very nearly decided to sell my ACS springs and get the full Brids B3 kit.
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      10-18-2012, 02:48 AM   #6
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They're not really 'bumpstops' that's a sort of misnomer, but eveyone knows that is meant though.

They are called 'additional dampers' and they are there to control the end speed of the damper travel and prevent the softer factory dampers from bottoming out so easily.

These allow the car manufacturers to use the same damper across a lot of vehicles and to easily tailor the travel and end cushioning using cheap rubber collars instead of multiple costly damper variants.

The birds B3 kits for example needs NO 'bumpstops' at all as the damper has end travel protection iternally, and is much stiffer anyway so the end travel is already much slower.

AFAIK you wouldn't use any bumpstops on a decent after market kit.
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      10-18-2012, 11:21 AM   #7
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Quote:
Originally Posted by doughboy View Post
They're not really 'bumpstops' that's a sort of misnomer, but eveyone knows that is meant though.

They are called 'additional dampers' and they are there to control the end speed of the damper travel and prevent the softer factory dampers from bottoming out so easily.

These allow the car manufacturers to use the same damper across a lot of vehicles and to easily tailor the travel and end cushioning using cheap rubber collars instead of multiple costly damper variants.

The birds B3 kits for example needs NO 'bumpstops' at all as the damper has end travel protection iternally, and is much stiffer anyway so the end travel is already much slower.

AFAIK you wouldn't use any bumpstops on a decent after market kit.
That's good news.

Just left Birds. First we went around in my car and the roads around there aren't that good, pretty similar to my area. Driving my car just felt normal like usual. Then sat in his demo car, which has ARBs as well, and went the same route at similar speeds. Just had to account for the larger and lower profile tyres. Felt so much more planted and in control. In low speed scenarios i didn't notice a great deal of difference, but thats due to the 19" low profile tyres the demo car has. I've got 17" higher profile so it will feel better. But high speed driving was amazing. The car just took the rough road surface in like it was nothing. The back end was much more controlled, even though the car has a lot more power than mine. For example it doesnt feel like its going to suddenly jump out and lose traction, if it does jump out (which kevin kindly showed me!) its gradual and not sudden. Big bumps in the road feel like nice soft thuds, similar to what i have at the moment but much improved at the rear. Minor-average bumps feel like nothing. Obviously you will feel something but its vastly improved from my set up. Another thing i notice is when we hit bumps, the car was a lot quieter, it didn't "bang" as much. The rear is well balanced with the front. In my car the front is ok but the rear is not really balanced, jolts quite a bit.

Now i just need to think about whether its worth it....thinking done, it is!!
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