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Is the bump setting on coilovers like a spring rate adder?

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Old Mar 23, 2012 | 08:53 AM
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Is the bump setting on coilovers like a spring rate adder?

I have the KW V3s, bump is 5clicks from max, springs swapped front to back, and I think I max'd my OE camber(slight toe in ). The car drives good, tires wear evenly on autox but i'm chewing up the outer corner edges too fast at 38psi in the tires. I already flipped the tires.
I'm not sure yet if I should get camber plates for the front and toe links for the rear to get a bit more camber (that doesnt sound good for street driving to events). So will additional bump/compression on the coilovers help from cord'ing and throwing out my tires prematurely? thanks
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Old Mar 23, 2012 | 09:59 AM
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Sounds like you need more camber. I DD my autox car with Ohlins set at 3degrees in the front. I have a set of all seasons that I DD on and they are lasting a while! Toe is what really increases tire wear when DD'ing.

What brand tires?
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Old Mar 23, 2012 | 10:16 AM
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Sounds like you need to get rid of that toe in or you need more camber. your bump settings will not affect tire wear just how stiff your suspension is. Why did u flop the springs?
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Old Mar 23, 2012 | 10:28 AM
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The answer is no, increasing bump/compression damping is not the same as adding spring rate. In a steady state corner the car will roll just as much.

- drew
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Old Mar 23, 2012 | 12:34 PM
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More camber or less roll is what you need. Thats why I always recommend a big front sway bar, the evo just need more roll resistance than the stock bar provides.
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Old Mar 23, 2012 | 02:00 PM
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Thanks. I have the Star specs, they do wear out quickly, even the inside front tire on OE camber/zero toe. We autox on concrete too.
I read on here that swapping the rear<-->front springs is a good starting point. it feels right i guess, maybe a bit harsh on the spine at first
I was hoping to get away with my current setup and avoid making adjustments on the autox events. I ordered the bump steer bushings and adjustable rear toe arms but those might take a while. I'll try testing +3 clicks on the compression this weekend (on concrete again) , maybe that'll leave me some rubber to drive home with atleast

whats the magic with Ohlins/Motons in stock classes? they cant upgrade their springs so the shocks must be doing some of that work

Last edited by ViciousLSD; Mar 23, 2012 at 02:04 PM.
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Old Mar 23, 2012 | 03:20 PM
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Originally Posted by GTWORX.com
The answer is no, increasing bump/compression damping is not the same as adding spring rate. In a steady state corner the car will roll just as much.

- drew
This. You might FEEL like you've added some spring, but that's not what's really happening.
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Old Mar 23, 2012 | 03:26 PM
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Originally Posted by ViciousLSD
whats the magic with Ohlins/Motons in stock classes? they cant upgrade their springs so the shocks must be doing some of that work
Better shocks do make a huge difference even on their own.

That and an assload of gas pressure....

- Andrew
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Old Mar 26, 2012 | 02:01 PM
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So I did some tests over the weekend and had overall bad outcome. I had a very good chance getting #1PAX in this event if I raced with my previous settings but ended 2secs slower (just to guage, the goal is to learn more about suspension tuning).
I tried and max'd out my bump settings on all 4 corners and I don't think I've ever been that fast and confident in the slalom section (26 paces) before. Braking was excellent, the best I've felt with this car from 2nd gear rev limit. The turn in was also great but power on exit on just about other elements of the course was horrible. I even got the tire to sound differently (way past sidewall screech) when it understeers like a limo. What I learned here is I need (to allow) some weight transfer to the back when I put down some power. Too bad the I didnt think fast enough to test backing out the rear setting (my reaction was to back out the front setting arr). I may have another chance to test until the camber parts arrive

Question: seeing that there is some consensus that the rear spring 'should' have a higher spring rate than the fronts, do we have a particular spring rate ratio between the springs as a starting point? I'm rethinking this front-back spring swap thing, maybe I should have higher spring rate in front for better braking and @slalom(?) and softer in the back to let more weight transfer to the rear during exit. and then fine tune with the bump setting.
I wonder if I'm looking at all this correctly
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Old Mar 26, 2012 | 07:29 PM
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What are your current spring rates?

- drew
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Old Mar 26, 2012 | 07:53 PM
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340lb front, 515lb rear.
stock IX wheels, star specs, 1.25"F & 1" R spacers
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Old Mar 27, 2012 | 08:23 AM
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I thought so. That's a bit too much of a spring rate spread IMO. Just swapping the springs on off the shelf KW's doesn't work out so well. I'd swap the front spring for an 8k and keep the rear 9k spring.

- Andrew
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