Mr S
Posted a lot
10-4 Good buddy.
Posts: 2,654
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Had a quick search and couldn't find the answer, so here goes. When you chop coil springs, what effect does it have on the spring rate? My own logic says that as you are removing metal from the spring, you are lowering the spring rate (making it easier to compress) as there is less material there. However, I've heard it said that it actually *increases* the spring rate - could this be right? If so, why? Later this year, I want to lower the 420SEL, but I want to do it 'stealthily' (20mm or so perhaps) so the Mrs can't really tell, she's totally against the idea! lol Then later, I'll get some smaller spring pads and lower it by about 6mm a time, she won't notice that either!  Cheers, Martin |
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Suzuki GSXR1000 K2
BMW R1150GS
BMW K1200RS
Chevy K5 Blazer
Chevy Suburban LT
Jaguar XKR
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It will stiffen them. Each coil now has to compress more for the amount of travel.
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Last Edit: Jan 1, 2009 21:08:18 GMT by Adam
1997 TVR Chimaera
2009 Westfield Megabusa
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Adam is correct.
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Your car is not 'epic', this thread is not 'epic'....the OCEAN is epic, the UNIVERSE is epic.... please stop misusing this word!! It would appear Hotrods are the new VWs - aint fashion funny! '69 BUICK LESABRE 350 |
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I repeat! adam is correct.
From my simple calculations, Halving the length doubles the rate or thereabouts.
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don't cut springs, YOU WILL DIE!
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1987 Maestro 1.6 HL perkins diesel conversion 1986 Audi 100 Avant 1800cc on LPG 1979 Allegro Series 2 special 4 door 1500cc with vynil roof. IN BITS. HERITAGE ISSUES.  |
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The size of the bar the coil is wound from is the relevant point - same bar weight over less coils equals more weight per coi and therefore a stiffer spring.
Leverage variation depending on your suspension design will also effect the spring rate.
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dannyb
South East
Posts: 1,048 
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don't cut springs, YOU WILL DIE! i'm still alive ;D |
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Odin
Posted a lot
Posts: 1,406
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Can you 'stealthily' lower with cut springs? Sport bras ahoy in my experience.
Not that they're wrong of course!
Cut springs that is, not sports bras - they're all kinds of wrong.
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don't cut springs, YOU WILL DIE! i'm still alive ;D No, your dead, like that bloke out the film "Ghost" |
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1987 Maestro 1.6 HL perkins diesel conversion 1986 Audi 100 Avant 1800cc on LPG 1979 Allegro Series 2 special 4 door 1500cc with vynil roof. IN BITS. HERITAGE ISSUES. |
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gasserjay
Part of things
Too bad the people who know it all can't do it all
Posts: 296
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Just slam it if she's not happy she can walk ;D
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1970 LTD country squire
1978 VW Westfalia
1988 VW Westfalia
1973 E100 econoline
1973 E200 econoline
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1973 VW GT bug
1965 21 window samba
1961 splitscreen double cab
1975 bay single cab
1956 oval baja
1975 Volvo 242
1993 Volvo 945 d24tic
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Seth
South East
MorrisOxford TriumphMirald HillmanMinx BorgwardIsabellaCombi
Posts: 15,516
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OK, hopefully here is the equation I have always used for spring rate.  k is the spring rate G is a material constant d is the wire diameter D is the mean coil diameter n is the number of active coils. If you cut coils off a spring the only one of these that changes is the number of coils. It decreases and since it is on the bottom of the fraction that means that your value of k, the spring rate, goes up. |
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Follow your dreams or you might as well be a vegetable. |
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OK, hopefully here is the equation I have always used for spring rate. k is the spring rate G is a material constant d is the wire diameter D is the mean coil diameter n is the number of active coils. If you cut coils off a spring the only one of these that changes is the number of coils. It decreases and since it is on the bottom of the fraction that means that your value of k, the spring rate, goes up. Thankyou Seth - I now have something to quote when people tell me I'm talking rubbish! |
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tigran
Club Retro Rides Member
In rust we trust. Amen.
Posts: 6,444
Club RR Member Number: 142
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Chopped springstigran
@tigran
Club Retro Rides Member 142
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Saying all of the above cut springs are running havoc with my stomach at the mo - bouncing around in the car all day long.
What is the solution to get rid of the bounce - better and shorter dampers i guess? Or harder springs? I know that the bounce is from the dampers not doing their job properly.
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1964 Rover P5 i6
1987 BMW 525e - The Rusty Streak
1992 Micra K10
2001 BMW E46 316i
2002 BMW E46 330Ci
2013 BMW F31 320d
2018 BMW G31 530d
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rtlkyuubi
Posted a lot
Low and Slow
Posts: 2,922
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it only gets bouncy once you cut loads off. My micra was bouncey because I kept hitting the bump stops  |
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Last Edit: Jan 2, 2009 7:13:23 GMT by rtlkyuubi
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Chopped springsDeleted
@Deleted
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Saying all of the above cut springs are running havoc with my stomach at the mo - bouncing around in the car all day long. What is the solution to get rid of the bounce - better and shorter dampers I guess? Or harder springs? I know that the bounce is from the dampers not doing their job properly. drive on flatter roads ;D no you are right it s bouncy because it could do with better springs and shocks its sitting about 5mm from the bump stop a shorter shock would sort the problem  . exactly the problem the polo has had really. been running it on cut fronts and the stock shocks for a while but really it needed a shorter shock for it to work properly. people put to much into the you shouldn't cut the springs it dangerous argument but when alls said and done its more to with the job of the damper really if its to long for the cut spring it will bottom out giving a harsh bouncy ride |
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don't cut springs, YOU WILL DIE!  |
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There is nothing more expensive than a cheap Mercedes
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don't cut springs, YOU WILL DIE! I think he was being ironical ... of he was thinking of the children.. OH PLEASE GOD THINK OF THE CHILDREN!!!! |
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Later this year, I want to lower the 420SEL, but I want to do it 'stealthily' (20mm or so perhaps) so the Mrs can't really tell, she's totally against the idea! lol Then later, I'll get some smaller spring pads and lower it by about 6mm a time, she won't notice that either! Good idea, got hints of these two about it:  |
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1974 Lancia Beta Saloon
1975 Mazda 929 Coupé
1986 Mazda 929 Wagon
1979 Mazda 929 Hardtop
1982 Fiat Argenta 2.0 iniezione elettronica
1977 Toyota Carina TA14
1989 Subaru 1800 Wagon
1982 Hyundai Pony 1200TL 2-dr
1985 Hyundai Pony 1200 GL
1986 Maserati 425 Biturbo
1992 Rover 214 SEi 5-dr
2000 Rover 45 V6 Club
1994 Peugeot 205 'Junior' Diesel
1988 Volvo 760 Turbodiesel Saloon
1992 Talbot Express Autosleeper Rambler
2003 Renault Laguna SPEARS OR REAPERS
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I think he was being ironical ... of he was thinking of the children.. OH PLEASE GOD THINK OF THE CHILDREN!!!! The children. Of course, silly me... |
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There is nothing more expensive than a cheap Mercedes
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Yes I was being ironicalised, although I'm still not convinced on the topic of spring cutting..... it just seems a bit of a bodge to me.
Still, weve been here before... horses for courses and all that!
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1987 Maestro 1.6 HL perkins diesel conversion 1986 Audi 100 Avant 1800cc on LPG 1979 Allegro Series 2 special 4 door 1500cc with vynil roof. IN BITS. HERITAGE ISSUES. |
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. exactly the problem the polo has had really. been running it on cut fronts and the stock shocks for a while but really it needed a shorter shock for it to work properly. 
