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03-05-2017, 02:15 PM | #199 |
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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).
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04-17-2017, 01:46 PM | #200 |
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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.
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04-17-2017, 03:07 PM | #201 |
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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.
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08-04-2017, 04:31 AM | #202 | |
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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). |
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02-27-2018, 01:51 AM | #203 | |
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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). |
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02-27-2018, 06:21 AM | #204 |
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iMuch appreciation to fe1rx for the info here.
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02-27-2018, 07:50 AM | #205 | |
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02-27-2018, 09:54 AM | #206 |
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I went back through the thread. You are correct, thank you for point that out.
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02-27-2018, 03:02 PM | #207 |
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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. Last edited by bbnks2; 02-27-2018 at 10:12 PM.. |
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03-03-2018, 06:29 AM | #208 |
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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. |
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03-03-2018, 03:30 PM | #209 | |
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03-03-2018, 08:55 PM | #210 | ||
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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. |
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03-08-2018, 08:51 AM | #211 | |
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03-29-2018, 05:50 PM | #212 | |
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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.
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05-24-2018, 09:10 AM | #213 | |
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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? Last edited by bNks334; 05-24-2018 at 03:16 PM.. |
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05-25-2018, 01:18 PM | #214 | |
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05-27-2018, 12:09 AM | #215 | ||
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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. |
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05-27-2018, 10:07 PM | #216 | |
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Last edited by bbnks2; 05-28-2018 at 08:40 AM.. |
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05-29-2018, 04:28 AM | #217 | |
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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? |
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05-29-2018, 08:01 AM | #218 | |||
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Stupid work computer is signed into my semi-banned account lol
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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... Last edited by bNks334; 05-30-2018 at 02:26 PM.. |
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05-31-2018, 08:12 AM | #219 |
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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. |
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12-25-2018, 05:01 PM | #220 | |
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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 |
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