fe1rx Ohlins Installation

[fe1rx]

Originally Posted by v4vasilis

Would you recommend the 60nm in front and the 140nm in the back for my car as well?

They work well for me. At the front the 178 mm x 60 N/mm spring is just about the only one that will give you decent clearance from the tire to the spring perch and will provide adequate stroke to prevent coil binding (but only when adjusted for minimal preload).

[davidwarren]

Since you have had the Ohlins installed for about three years now, have you considered having them rebuilt? I was reading the recommended service interval is only something like 30K KM. Would be interesting to have them dyno'd again before and after.

[fe1rx]

Originally Posted by davidwarren

Since you have had the Ohlins installed for about three years now, have you considered having them rebuilt? I was reading the recommended service interval is only something like 30K KM. Would be interesting to have them dyno'd again before and after.

No I haven't. I had them dyno'd at about 23K km and they have about 30K on them now. They seem fine still.

[titium]

Originally Posted by fe1rx

They work well for me. At the front the 178 mm x 60 N/mm spring is just about the only one that will give you decent clearance from the tire to the spring perch and will provide adequate stroke to prevent coil binding (but only when adjusted for minimal preload).

Firstly thanks for all the detailed information. awesome read


couple of questions

I'm trying to decide what springs to pair with my konis - my current swift spec r's are pretty average - too short imo resulting in noticeable coil bind and I've had to have the rears replaced due to sagging the equivalent of 20mm ride height.

I was thinking 300lb/in 53N spring 8" length front with 600lb/in 105N 10" length rear. ride height 10mm lower then stock (around 351mm using your measuring method).

my only concern is wheel fitment if I'm understanding your data correctly I think an OEM 261 front with 225 should be fine but I'd run in to issues if I wanted to go wider wheels. are you able to confirm ? stock top hats with dinan camber plates.

what offset would be required for an 8.5" wheel to clear the lower spring perch up front (assuming it can't be adjusted above the wheel).

[titium]

Originally Posted by Gangplank

When using the 7" springs do you have a front spring preload that you would recommend to avoid coil bind issues would 3-4 mm of preload be a good starting point?

Also when stating 10 clicks I presume that is 10 clicks from full soft (recalling from when I was racing motorcycles to start from soft not hard to adjust)

Easiest way to do it is to make sure the distance the lower perch is from the top of the strut body + some distance for the bump stop (when fully compressed) is greater then the height of the spring at coil bind + a tiny distance to keep the spring in its "usable" range.

7" springs are tricky, you really need to optimise your setup around the spring (forget adjusting height by simply moving the spring perch) also forget anything below 60N/mm rate.
A 60N/mm spring is compressed 60mm at static ride and has around 110mm usable travel this leaves approx 50mm of travel on compression. Preloading the spring above 20mm really eats into your droop travel even if you have a way to prevent the spring from being coil bound (e.g. external bumpstops).

[Gangplank]

iMuch appreciation to fe1rx for the info here.

[titium]

Originally Posted by Gangplank

Looking at Fe1xr's post from 4/03/14 and If I am reading this right (and I hope that I am) his GC modified stack is 44mm. The stock BMW top hats that I will be using give a Top Mount Height of 70mm. That's a difference of +26 (+6 if Dinan plates used but I'm not adding those at this stage).

Be sure to consider the fact that the top mount has some deflection in it and will compress when load it applied.

[Gangplank]

Originally Posted by titium

Be sure to consider the fact that the top mount has some deflection in it and will compress when load it applied.

I went back through the thread. You are correct, thank you for point that out.

[bbnks2]

That is a nice little spreadsheet for calculating resultant ride height changes. Even if you don't find it useful it's great to know how and why it works...

Increasing preload only changes your bump/droop distribution. The strut still has the same usable stroke. However, the springs usable stroke will effectively be reduced. So long as the spring has enough usable stroke (which it generally doesn't in 7" lengths), you won't be limiting your suspensions travel at all. However, you'll be increasing the return rate of the spring (you'll need more damping) and changing the droop/bump distribution as stated above.

Increasing the stack height of the camber plate has 0 affect on the spring or the strut. It only affects ride height. The strut tube length is really what determines the length of the spring that you can run. A longer strut tube provides additional clearance from the tire to the lower spring perch allowing for a longer spring. However, this increases the cars ride height. A shorter camber plate stack height can offset a longer strut tube and therefore increase wheel clearance without affecting the cars target ride height.

So, let's go back to what I said about 7" springs. Coil bind seems to be the focus of the discussion and for good reason. I'll use with my numbers to provide a working example since I know them and I already presented them elsewhere (although the autocross pros were quick to dismiss math and to dismiss anything that contradicted what they had to say):

* A SWIFT 6K (336lb/in) 7" spring has 4.2" of usable travel and 4.6"
of max travel (http://www.swiftsprings.com/products...lover-springs/) and my YCW struts have roughly 4.25" of available travel before engaging the bump stops. Therefore, coil bind should not be an issue.

Now, if we pre-load the spring .25" the spring would now only have 3.95" of available travel remaining which means it will begin to bind BEFORE the strut reaches it's usable range of compression travel (4.25"). Bad.

Why use a 7" spring? Well, we all want that extra bit of tire clearance and we need to raise the spring perch on every aftermarket coilover to get it... How long of a spring you can use all depends on your coilover length... You might be able to use a 7.5" spring, or, you might not be able to use more than a 6.5" spring. Why does this all matter? Well, if your coilovers have a longer stroke like 5", then you'll either need a significantly longer spring like 9" to use the same 6K rate, or, you'll need to run a significantly softer spring like 3k... not feasible. The most awkward solution that has been presented has been to run such a high spring rate that the car doesn't compress at all and you don't have to worry about spring lengths... but that is just stupid.

So, you really need to go outside and measure your particular coilovers strut stroke before you continue to talk about springs. As for static bump and droop travel, that is an easy calculation. You divide the cars sprung weight (roughly 700lb) by the effective wheel rate (spring rate x motion ratio). So for me, 700lb/(336*.9216)=2.26" of static compression. 4.25" of travel less 2.26" of static compression = 2" of remaining bump travel and 2.25" of available droop travel. The wheel itself travels slightly further... 2.25/.9216=2.44" of wheel travel.

So no, I don't think 7" springs are tricky at all... I think tuning suspension is tricky. This all goes back to the fact that a lot of people on this board advocate for running rates and springs that they have no idea WHY they work and they probably WON'T work for your particular setup.

[John_01]

The real key to preventing a spring from binding is to use the correct bump stop to suit the installation. It seems that is why there are issues with the Ohlins dampers, which have the bump stop located internally. Most of what is achieved with custom mounting hardware in this thread is there to position the stock ohlins bump stop to prevent the spring from binding.

If the bump stop was external like TC Kline or other Koni shocks, additional packing washers or different bump stops could be installed to solve the issue without requiring anything to be custom made.

[Gangplank]

Originally Posted by John_01

The real key to preventing a spring from binding is to use the correct bump stop to suit the installation. It seems that is why there are issues with the Ohlins dampers, which have the bump stop located internally. Most of what is achieved with custom mounting hardware in this thread is there to position the stock ohlins bump stop to prevent the spring from binding.

If the bump stop was external like TC Kline or other Koni shocks, additional packing washers or different bump stops could be installed to solve the issue without requiring anything to be custom made.

I don't think it was required due to the Ohlins design. I believe it was related to his choice of low profile camber plates which are 44 mm instead of the BMW tops which are 70.

[titium]

Originally Posted by Gangplank

I don't think they had to be custom made due to the Ohlins design. I believe it was more due to his choice of low profile camber plates which are 44 mm instead of the BMW tops which are 70.

Its a combination of multiple things related to his setup. Although not immediately obvious there are actually two sperate issues he's addressed with the custom components in his setup.

1) Maximum suspension travel to prevent coil bind
2) droop travel.

Having shocks with external bumpstops gives you the freedom to set your suspension bump limit to whatever you want satisfying requirement 1) however you still need to be weary when preloading the spring. For every mm of preload there is 1mm less droop travel (assuming a motion ratio of 1 for simplicity). General rule of thumb is to allow for approx 50mm droop travel (40mm minimum). With a 60N 7" spring on a 1 series which is compressed 60mm at static ride this means you're limited to approximately 10mm preload (20mm max) to satisfy the second criteria regardless of whether the spring will be coil bound at full bump travel.

Of course you can run more preload if your willing to accept less droop travel.

[bbnks2]

Originally Posted by titium

Its a combination of multiple things related to his setup. Although not immediately obvious there are actually two sperate issues he's addressed with the custom components in his setup.

1) Maximum suspension travel to prevent coil bind
2) droop travel.

Having shocks with external bumpstops gives you the freedom to set your suspension bump limit to whatever you want satisfying requirement 1) however you still need to be weary when preloading the spring. For every mm of preload there is 1mm less droop travel (assuming a motion ratio of 1 for simplicity). General rule of thumb is to allow for approx 50mm droop travel (40mm minimum). With a 60N 7" spring on a 1 series which is compressed 60mm at static ride this means you're limited to approximately 10mm preload (20mm max) to satisfy the second criteria regardless of whether the spring will be coil bound at full bump travel.

Of course you can run more preload if your willing to accept less droop travel.

I think more important than modifying bumps stops is to understand/measure your struts available travel and how it relates to your selected springs usable stroke.

[Gangplank]

Originally Posted by fe1rx

4) Ride height 326 mm front, 334 mm rear.

Item 4) represents no change from my previous front ride height and a 8 mm drop in the rear.

…

fe1rx I'm curious how or why you settled on the ride height. Are you still using the same or have you modified and if so can you fill us in on why? Do you know the actual rake measurement or is not not something you have measured or are concerned with?

Thanks in advance.

[bNks334]

Originally Posted by fe1rx

https://www.1addicts.com/forums/attachment.php?attachmentid=989172&d=1394383657

Is this chart correct? I have read the opposite that the rear losses camber and toes-in when compressed... E46's were known to gain camber and toe-out under compression, but our suspension has the toe-arm located behind the axle instead of in front of it like the E46. That location change would suggest the alignment changes should be the opposite under cornering loads. I am thoroughly confused now and I have found lots of contradicting opinions on how the rear suspension of an E9x and E8x changes dynamically. Please advise!

Edit: Maybe the charts are just misleading for my intents. It makes sense that both the front and rear would gain camber in compression, but IN ROLL both ends of the car lose camber and camber recovery is negligible. Looks like the rear will lose more camber in roll than the front?

[bbnks2]

Originally Posted by 135

There are two or three 135i race cars in the national professional categories but I don't think they'd provide me with the details of their suspension setup. I'd think those secrets would be tightly held. Other than at a professional level, there aren't many 135s, going to the same extreme, being raced here. From my research, I have come across several other US-based 135i race cars that have published their spring rates and they were as follows:
Front / Rear
650 / 700
560 / 800+
550 / 850
700 / 850

I just want to point out for anyone reading this thread that these cars more than likely not have modified rear suspension. They probably don't run a divorced spring setup. They have probably all moved to true coil-over designs which significantly increases the rear motion ratio such that the quoted spring rates are actually very relatively close. These cars also have aero added for several hundreds pounds of added downforce. The rates that they run are no where near as stiff as you need on a regular car or even one with a basic lip and spoiler lol.

[135]

Originally Posted by bbnks2

I just want to point out for anyone reading this thread that these cars more than likely not have modified rear suspension. They probably don't run a divorced spring setup. They have probably all moved to true coil-over designs which significantly increases the rear motion ratio such that the quoted spring rates are actually very relatively close. These cars also have aero added for several hundreds pounds of added downforce. The rates that they run are no where near as stiff as you need on a regular car or even one with a basic lip and spoiler lol.

All of those cars had standard divorced rear suspension. None of them had a rear coilover conversion. That post is 2 1/2 years old and the cars in question were setup up to 10 years ago - no one had even thought about doing a rear coilover conversion on a 1-series back then.

The front spring rate on those cars would be unusually stiff for a street car, while the rear spring rate would be standard fare for a street car - but these were race cars, not street cars, so they had the suspension tuned for their purposes - maybe they needed or wanted a softer rear spring rate relative to what would otherwise be required for the front.

While some street cars use F342/R684 spring rates, F400/R800 spring rates are just as common and perfectly suitable for the street - it's the setup and quality of the dampers that will determine how comfortable the ride is.

[bbnks2]

Originally Posted by 135

All of those cars had standard divorced rear suspension. None of them had a rear coilover conversion. That post is 2 1/2 years old and the cars in question were setup up to 10 years ago - no one had even thought about doing a rear coilover conversion on a 1-series back then.

The front spring rate on those cars would be unusually stiff for a street car, while the rear spring rate would be standard fare for a street car - but these were race cars, not street cars, so they had the suspension tuned for their purposes - maybe they needed or wanted a softer rear spring rate relative to what would otherwise be required for the front.

While some street cars use F342/R684 spring rates, F400/R800 spring rates are just as common and perfectly suitable for the street - it's the setup and quality of the dampers that will determine how comfortable the ride is.

I am not talking about being comfortable. I am concerned with mid corner balance. You make it seem like it's some revolutionary task to put a coilover in the rear lol who exactly are these race teams youre referncig? I've seen some pretty poor setups on some "race" cars. Bimmerworks is about the only one I know of that ran 328i's competitively.

[135]

Originally Posted by bbnks2

I am not talking about being comfortable. I am concerned with mid corner balance. You make it seem like it's some revolutionary task to put a coilover in the rear lol who exactly are these race teams youre referncig? I've seen some pretty poor setups on some "race" cars. Bimmerworks is about the only one I know of that ran 328i's competitively.

You drew a relationship between the spring rates (stiffness) used on a race car versus a regular car or one with a basic spoiler and lip. What else would a "regular" car be targeted towards if not some degree of comfort. At no point did you mention mid-corner balance so how is anyone supposed to know that's your focus in this conversation?

No, it's not revolutionary to convert from divorced to a true coilover setup but, when it takes anyone on the 1-series platform almost 10 years to do it, what would you suggest we call it?

[bNks334]

Stupid work computer is signed into my semi-banned account lol

Originally Posted by 135

You drew a relationship between the spring rates (stiffness) used on a race car versus a regular car or one with a basic spoiler and lip. What else would a "regular" car be targeted towards if not some degree of comfort.

No I did not. You did... I was comparing a "race" car to a street car because of the TIRES and DOWNFORCE. A "race" car is going to be running slicks and several hundred lbs of downforce which is going to require significantly more spring rate to support than your average street car that MIGHT run 200tw at best or maybe even some r-comps... the comment had nothing to do with ride comfort.

Originally Posted by 135

At no point did you mention mid-corner balance so how is anyone supposed to know that's your focus in this conversation?

Your original reply was made in the context of contradicting the need for less front spring and more rear spring rate as evidenced by whatever "race cars" you've gotten spring rates from. All of this being said within the context people stating their cars are not neutral handling and having reduced compression stroke with 12k/672lb rear springs...

Originally Posted by 135

No, it's not revolutionary to convert from divorced to a true coilover setup but, when it takes anyone on the 1-series platform almost 10 years to do it, what would you suggest we call it?

Race teams don't sit on forums talking about what they are doing. Most well driven/well set up cars I see at HPDE don't even even go on forums for their build info.

I was just at PWC and every 235i being raced is converted to a rear coilover setup. I don't see anyone on the 2-series forums doing it though... and you SHOULDN'T be doing it unless you are also doing a roll cage which reinforces the chassis mount. I am sure someone will ask one of those race teams what their spring rates are though (which I already did myself) and then post them all over the forums going "well race teams run..." Also, 1-series coilover conversion kits have been available since 2008.

Oh, and I was also reading the "stock" Ohlins rate on a F22 235i is 6k/16k. The F22 chassis has the same HA5 BMW multi-link rear suspension and close to the same motion ratio as the e8x/e9x. Makes me wonder why the Ohlins stock rate for a 335i was sold as 6k/7k...

Further, Ohlins stock spring rates for the M3/M4 with a .47 motion ratio (compare to our .31) is 9K/23K and no one over there is complaining about oversteer or their cars not being fast around a track... seems like Ohlins either didn't do their homework back in 2008, like many other manufacturers, or, they just didn't think drivers would be able to handle a neutral balanced car back in 2008 and manufactured in some understeer...

[135]

Looking back, it seems that I had misinterpreted some of your wording but my original points still stand: all of those cars had standard divorced rear suspension - none of them had a rear coilover conversion - and the referenced rear spring rates (at least those in the 700-800 lbf/in range) are not excessively stiff but quite the norm and suitable for a street-oriented 1-series car.
Granted, you used terms such as "likely" and "probably".

I didn't come across any 1-series rear coilover conversion kits in 2008, nor in 2012/13, so it would surprise me if they were available then but I'd be interested to know which coilover manufacturer was producing them. The first 1-series rear coilover conversion I saw was last year (I think) - I don't recall seeing one in 2016 (or earlier).
The 2-series platform has 6+ years advancement that's gone before it with its platform predecessor so it's understandable that it would be more advanced and advance more rapidly but I have not kept up with it to be able to comment.

I think in the early days for the 1-series, some (maybe most) coilover manufacturers just based their spring rates on the E46, only to find out they were a fair way off.

[ornicar]

Originally Posted by Orb

One of the best suspension write ups I have ever seen.....awesome details!!

I was looking at the CG plated when I came across this thread. I will defiantly will make my own. They obviously did no testing or calculations.

Question for the poster:
Did you account for the CG OEM spring perch deflection under load. I measured about 10 mm for the OEM spring perch. I suspect this came out a wash or close to it.

As for the rear spring compressing on a curved axis. I did a non linear analysis in Ansys and the spring rate does increase anywhere from 15-40%. This is dependent on spring wire diameter, spring length and stroke position so not a straight forward answer. I resolved the issue with the a sealed articulating spring perch placed between the helper spring and main spring. The soft helper spring works well at taking up translation by deforming as well. This made a very noticeable improvement and ride quality was a night a day difference especially over rough roads.

Hello,

i am into "constituing" a rear coilover set for my 125i:


- Main spring Eibach 7" Length ; 2,25" ID ; 650 Lb/inch rate ; PN : 0700.225.0650

- Tender Spring Eibach 2,68" Length ; 2,25" ID ; 300 Lb/inch rate ; PN : 0175.225.0300

- HPA Height Adjuster or another good quality one. I appreciate this one because you can fitting a thrust bearing to avoid stress in the spring

https://www.hpashop.com/HPA-E82-E9x-...st-e82-e9x.htm

I have one question:

Does anyone know where i can buying this ball joint coupler "sealed articulating spring perch" in 2,25 Diameter?

TY