BMW 1 Series Coupe Forum / 1 Series Convertible Forum (1M / tii / 135i / 128i / Coupe / Cabrio / Hatchback) (BMW E82 E88 128i 130i 135i)
 





 

Post Reply
 
Thread Tools Search this Thread
      01-12-2018, 07:06 AM   #1
bionicbelly
Second Lieutenant
78
Rep
237
Posts

Drives: Z3 coupe, 128i
Join Date: Oct 2017
Location: Des Moines

iTrader: (1)

Springs

So, I think I am going to get some shocks for my car, and I need to get springs. I have sets of 17x9 Kosei K8r's, and will be running 225 or 245 hoosiers.

I think I have the spring rates figured out, but I would like to confirm the lengths with people that are running 9" front wheels. From what I have read, it is a 9" spring in the rear and 8" in the front.

Thanks in advance.
Appreciate 0
      01-12-2018, 08:35 AM   #2
RyanDavies
Lieutenant
63
Rep
448
Posts

Drives: 2012 128i MSport
Join Date: Sep 2015
Location: Washington, DC

iTrader: (2)

Quote:
Originally Posted by bionicbelly View Post
So, I think I am going to get some shocks for my car, and I need to get springs. I have sets of 17x9 Kosei K8r's, and will be running 225 or 245 hoosiers.

I think I have the spring rates figured out, but I would like to confirm the lengths with people that are running 9" front wheels. From what I have read, it is a 9" spring in the rear and 8" in the front.

Thanks in advance.
With every setup I can imagine, that is way too tall of a spring to work in the front. and clear the tire. You want the lower spring perch sitting above the tire to maximize clearance, otherwise it will eat a LOT of it up. 9in without rear helpers (depending on rate, and depending on adjusters) is likely right. I have 6in springs up front (450/lbin), and they clear the perch fine. I wouldn't want any more than 6in, maybe 6.5 depending upon what you're doing for upper mounting (I think some specific camber plate combinations with a very low stack height could manage 6.5 or 7.

Which dampers again?
Appreciate 1
      01-12-2018, 08:49 AM   #3
bbnks2
Colonel
1207
Rep
2,025
Posts

Drives: 135i N55
Join Date: Jan 2017
Location: NY

iTrader: (0)

I am not sure how Ryan makes 6" work up front without massive binding unless he is running ridiculously stiff springs.

7" is what you need (depending on coil-over strut length) to keep the spring perch above the tire (I run 178mm springs). That is cutting it pretty close. I have K8R in 17x9 ET45. You need at least an 8mm spacer up front. Preferably use a proper 10mm so that you can get the spacers with a hubcentric lip to mount the wheel on. You'll also need adjustable camber plates.

In the rear, you'll need a slight roll too depending on how much camber you run. Personally, I try to keep my rear camber less aggressive than -2*. Multi-link rear suspension does not lose camber under cornering loads like the mcpherson front suspension does. But, the camber can help avoid the fender roll.

Also, stack height of the upper mount has nothing to do with the relationship between the lower spring perch and the tire. Stack height of the upper mount just effects ride height.

Last edited by bbnks2; 01-12-2018 at 01:13 PM..
Appreciate 1
      01-12-2018, 08:50 AM   #4
bionicbelly
Second Lieutenant
78
Rep
237
Posts

Drives: Z3 coupe, 128i
Join Date: Oct 2017
Location: Des Moines

iTrader: (1)

AST 5200. Awesome. This is what I was wondering. I saw that the lower perch has to go above the tire to clear a 9"wheel/tire combo, but couldn't find an exact measurement anywhere.

It looks to be a shorter stack height for the camber plate.

Am I correct in assuming 9" is good for the rear then?
Appreciate 0
      01-12-2018, 09:03 AM   #5
Kgolf31
Brigadier General
Kgolf31's Avatar
459
Rep
4,531
Posts

Drives: 2007 Z4MC, 2012 128i
Join Date: Sep 2008
Location: Ohio

iTrader: (4)

I ran 6.5" springs up front with no issues on Kosei K8Rs with a 12.5mm spacer
Appreciate 1
drunkenup213.50
      01-12-2018, 09:11 AM   #6
bionicbelly
Second Lieutenant
78
Rep
237
Posts

Drives: Z3 coupe, 128i
Join Date: Oct 2017
Location: Des Moines

iTrader: (1)

https://www.turnermotorsport.com/p-3...track/?pdk=Awo

These are the camber plates that will be used.
Appreciate 0
      01-12-2018, 10:41 AM   #7
RyanDavies
Lieutenant
63
Rep
448
Posts

Drives: 2012 128i MSport
Join Date: Sep 2015
Location: Washington, DC

iTrader: (2)

Quote:
Originally Posted by bbnks2 View Post
I am not sure how Ryan makes 6" work up front without massive binding unless he is running ridiculously stiff springs.

7" is what you need to keep the spring perch above the tire (I run 178mm springs). That is cutting it pretty close. I have K8R in 17x9 ET45. You need at least an 8mm spacer up front. Preferably use a proper 10mm so that you can get the spacers with a hubcentric lip to mount the wheel on. You'll also need adjustable camber plates.

In the rear, you'll need a slight roll too depending on how much camber you run. Personally, I try to keep my rear camber less aggressive than -2*. Multi-link rear suspension does not lose camber under cornering loads like the mcpherson front suspension does. But, the camber can help avoid the fender roll.

Also, stack height of the upper mount has nothing to do with the relationship between the lower spring perch and the tire. Stack height of the upper mount just effects ride height.
The difference in travel between a 6 and 7in spring is only 1/2in. I ran rates between 400-575 on my E82 with a 6in 2.25 spring (least amount of travel) and not once ran into travel issues. I have a bigger diameter (more travel) spring on the car now, but also run a lot less compression force now, so it probably uses more travel than it did. Still definitely no coil bind. If that's your concern, use a progressive bump stop to operate at infinite rate before coil bind. As stated above, I'm not at all stiff, very much the opposite. I think unless you're jumping your car or something like that, you massively overestimate how much travel is actually used. For example, at a given ride height, the wheel would have to go into the wheel well over 2in before the spring coil bound. For almost any of us, there would be WAY bigger problems like that than coil bind. Namely, either a destroyed tire or a missing fender. It simply doesn't happen.

In any case, there's a big difference in corner weight between a 135 and a 128.
Appreciate 0
      01-12-2018, 01:08 PM   #8
bbnks2
Colonel
1207
Rep
2,025
Posts

Drives: 135i N55
Join Date: Jan 2017
Location: NY

iTrader: (0)

Quote:
Originally Posted by bionicbelly View Post
AST 5200. Awesome. This is what I was wondering. I saw that the lower perch has to go above the tire to clear a 9"wheel/tire combo, but couldn't find an exact measurement anywhere.

It looks to be a shorter stack height for the camber plate.

Am I correct in assuming 9" is good for the rear then?
How long [short] the spring has to be to clear the wheel is going to depend on the length of the struts as well... not all coil-overs are the same length.
Appreciate 0
      01-12-2018, 01:18 PM   #9
bbnks2
Colonel
1207
Rep
2,025
Posts

Drives: 135i N55
Join Date: Jan 2017
Location: NY

iTrader: (0)

Quote:
Originally Posted by RyanDavies View Post
The difference in travel between a 6 and 7in spring is only 1/2in. I ran rates between 400-575 on my E82 with a 6in 2.25 spring (least amount of travel) and not once ran into travel issues. I have a bigger diameter (more travel) spring on the car now, but also run a lot less compression force now, so it probably uses more travel than it did. Still definitely no coil bind. If that's your concern, use a progressive bump stop to operate at infinite rate before coil bind. As stated above, I'm not at all stiff, very much the opposite. I think unless you're jumping your car or something like that, you massively overestimate how much travel is actually used. For example, at a given ride height, the wheel would have to go into the wheel well over 2in before the spring coil bound. For almost any of us, there would be WAY bigger problems like that than coil bind. Namely, either a destroyed tire or a missing fender. It simply doesn't happen.

In any case, there's a big difference in corner weight between a 135 and a 128.
My 135i weighed in at 3220lbs. The weight difference between a 135i and 128i is over-stated. All that is different is a turbo and an intercooler. True though that the extra weight is over the front wheels which moves it to a 52/48 weight distribution instead of 50/50. The mandatory sunroof doesn't help either.

As for travel... I'd beg to differ. Do the math. Cornering loads can exceed 1500lbs on the outside tires. Even at a spring rate of 500lbs/in that's 3in of compression travel (not including the sway bars added roll resistance of a big bar that puts you closer to 800lb/in). People who don't want to run 500lb/in, which is pretty damn stiff compared to say 300lb/in, would all benefit from running the longest spring possible when using the relatively softer springs vs your setup. If you're not already riding on your bump-stops at times, you are probably a hair away from it.

Last edited by bbnks2; 01-12-2018 at 02:28 PM..
Appreciate 0
      01-12-2018, 04:20 PM   #10
Ginger_Extract
California-bound
Ginger_Extract's Avatar
United_States
383
Rep
1,480
Posts

Drives: BMW 135i
Join Date: Jan 2013
Location: Los Angeles, CA

iTrader: (3)

FWIW, I'm selling a pair of TC Kline 6.5" 400lb-in coil-over springs. They cleared a 17x9 +35 with a 255/40 tires no problem. Message me if interested.
__________________
Streets of Willow: 1:27.7 CW 11/15/15; 1:29.5 CCW 8/15/15 |||| Autoclub Speedway ROVAL (CCW): 1.52.6 - 12/2/17
Willow Springs - Big Willow (CW): 1:35.8 - 3/31/18 |||| Buttonwillow #13 (CW): 1:59.3 1/27/18
https://www.facebook.com/JakeStumphRacing |||| http://www.youtube.com/user/RaceMeMZ3
Appreciate 0
      01-13-2018, 08:10 PM   #11
Kgolf31
Brigadier General
Kgolf31's Avatar
459
Rep
4,531
Posts

Drives: 2007 Z4MC, 2012 128i
Join Date: Sep 2008
Location: Ohio

iTrader: (4)

Quote:
Originally Posted by bbnks2 View Post
My 135i weighed in at 3220lbs. The weight difference between a 135i and 128i is over-stated. All that is different is a turbo and an intercooler. True though that the extra weight is over the front wheels which moves it to a 52/48 weight distribution instead of 50/50. The mandatory sunroof doesn't help either.

As for travel... I'd beg to differ. Do the math. Cornering loads can exceed 1500lbs on the outside tires. Even at a spring rate of 500lbs/in that's 3in of compression travel (not including the sway bars added roll resistance of a big bar that puts you closer to 800lb/in). People who don't want to run 500lb/in, which is pretty damn stiff compared to say 300lb/in, would all benefit from running the longest spring possible when using the relatively softer springs vs your setup. If you're not already riding on your bump-stops at times, you are probably a hair away from it.
Calculations are nice until you have to deal with real world.

I'd like to say, I've zip-tied my shocks and never went to bumpstops. And my car ran pretty damn well...
Appreciate 0
      01-14-2018, 08:21 AM   #12
bbnks2
Colonel
1207
Rep
2,025
Posts

Drives: 135i N55
Join Date: Jan 2017
Location: NY

iTrader: (0)

Quote:
Originally Posted by Kgolf31 View Post
Calculations are nice until you have to deal with real world.

I'd like to say, I've zip-tied my shocks and never went to bumpstops. And my car ran pretty damn well...
I think you missed the point... you can't run a 6" spring without running a significantly higher spring rate. That is what I hedged my statement with. Is op prepared to run 450lb springs?

If you do the math, a 6" 450lb spring will bind at about 2.5% less cornering load than a 7" 336lb spring can handle. The 336lb would just make more use of the struts usable stroke and have more droop travel available for curbing and uneven pavement.

If he runs a 6" 336lb spring he will have .5" less usable spring stroke (3.7") and he will reach max usable stroke at only 60% of the cornering load a 7" 336lb spring could handle. Does that better illustrate the point so that op can make a more informed decision about what springs to go with???

7" springs clear my k8r wheels fine even with a bit of sag in them. But, not all coilovers have the same strut length.

The math makes sense. Math is how engineers and race teams build cars. Peoples logic on forums for wanting to run springs that limit their suspension travel to nothing is what doesn't makes sense. Why not just bolt the wheels directly to the chassis?
Appreciate 0
      01-14-2018, 09:04 AM   #13
RyanDavies
Lieutenant
63
Rep
448
Posts

Drives: 2012 128i MSport
Join Date: Sep 2015
Location: Washington, DC

iTrader: (2)

Okay, starting back here.

You're assuming a lot of things. 100% load transfer (doesn't happen). That TOUCHING a bump stop is bad (it's not, assuming you have quality bump stops). That sway bars work in a very different way in your universe than they do in practice. I suppose if there was no sway bar on the car at all, operating on a very high grip surface, and running the mega-soft rates you're suggesting, you'd be correct. The car operates from the factory on the bump stops on both ends.

If OP runs a 336lb spring on Hoosiers, he'll have way bigger handling problems to worry about than coil bind...

You're right in that math is always right. But you have to utilize all of the factors to ensure your math is correct. You've also completely ignored the effects of roll centers as well. This isn't NEARLY as simple as your'e claiming it to be (nor is it for damn near anyone), which is why real world experience and testing is far more valuable than sitting in front of a computer.
Appreciate 0
      01-14-2018, 10:59 AM   #14
bbnks2
Colonel
1207
Rep
2,025
Posts

Drives: 135i N55
Join Date: Jan 2017
Location: NY

iTrader: (0)

Quote:
Originally Posted by RyanDavies View Post
Okay, starting back here.

You're assuming a lot of things. 100% load transfer (doesn't happen). That TOUCHING a bump stop is bad (it's not, assuming you have quality bump stops). That sway bars work in a very different way in your universe than they do in practice. I suppose if there was no sway bar on the car at all, operating on a very high grip surface, and running the mega-soft rates you're suggesting, you'd be correct. The car operates from the factory on the bump stops on both ends.

If OP runs a 336lb spring on Hoosiers, he'll have way bigger handling problems to worry about than coil bind...

You're right in that math is always right. But you have to utilize all of the factors to ensure your math is correct. You've also completely ignored the effects of roll centers as well. This isn't NEARLY as simple as your'e claiming it to be (nor is it for damn near anyone), which is why real world experience and testing is far more valuable than sitting in front of a computer.
I have done real world testing lol... I shouldnt have said bump stop. I meant to say you're probably a hair away from coil bind... I said bump stop instead because riding on the bump stop would prevent you from seeing the signs of bind. I don't know the stroke of the struts you run. Seeing as how you tried to rationalize my mistake with an outlandish example shows you don't understand what I am saying. Coil is always going to bind before touching the bump stops with the springs used in the above examples. Unless of course you have struts with insanely short stroke.

The numbers I presented don't factor in sway bars. I left those assumptions out of it to provide a straightforward example of how spring length plays a roll in how much load a wheel can see before the spring binds. It really is that simple if you understand how much the spring compresses at static ride height and how much usable spring length you then have left over before it binds. It's basic math that I won't lay out for you.

Everything else you said makes 0 sense as a rebuttal to what I said. You need to read back up. The only one making assumptions is you. I simply replied to point out to op that the length of spring he needs to clear the tire will vary depending on the strut body length and that the length of the spring is going to have a significant impact on what kind of spring rates he is going to be able to run. I then followed up with an example. You're the one assuming things based off the setup you run and the trial and error that finally got you to a working setup. The problem we have here is that you don't really understand why the setup you run works.

Also, I run 275 z214 with 336lb spring... Care to explain why it's a handling problem? As I already said, it just means that my car has more suspension travel. Roll center is a great thing to bring up, but moment arm can only be tweaked so much. Maybe if you tweaked it correctly you wouldn't need 500lb springs? There is only so much you can do to change weight transfer. The cars center of gravity can only change so much and you can only make the car so wide. All you can. Really do is tweak wether the outside front wheels see more load or the rear...

Also, It doesn't take "100% load transfer" (whatever that means) to put 1500lbs of Force on the outside front wheel if that's what you were getting at... And, I have no clue what you mean by sway bars work differently "in my world." I am the one usually saying there is no magic to a sway bar in threads. It's a lever that provides resistance to weight transfer.

Last edited by bbnks2; 01-14-2018 at 11:39 AM..
Appreciate 0
      01-14-2018, 11:46 AM   #15
Kgolf31
Brigadier General
Kgolf31's Avatar
459
Rep
4,531
Posts

Drives: 2007 Z4MC, 2012 128i
Join Date: Sep 2008
Location: Ohio

iTrader: (4)

Quote:
Originally Posted by bbnks2 View Post
I think you missed the point... you can't run a 6" spring without running a significantly higher spring rate. That is what I hedged my statement with. Is op prepared to run 450lb springs?

If you do the math, a 6" 450lb spring will bind at about 2.5% less cornering load than a 7" 336lb spring can handle. The 336lb would just make more use of the struts usable stroke and have more droop travel available for curbing and uneven pavement.

If he runs a 6" 336lb spring he will have .5" less usable spring stroke (3.7") and he will reach max usable stroke at only 60% of the cornering load a 7" 336lb spring could handle. Does that better illustrate the point so that op can make a more informed decision about what springs to go with???

7" springs clear my k8r wheels fine even with a bit of sag in them. But, not all coilovers have the same strut length.

The math makes sense. Math is how engineers and race teams build cars. Peoples logic on forums for wanting to run springs that limit their suspension travel to nothing is what doesn't makes sense. Why not just bolt the wheels directly to the chassis?
Well, for one I said 6.5" Springs.

And yes, I know what your point is. But there is math and "sound calculations" and there are real life data points.

If you want, feel free to lookup my 128i results from campaigning in STX...on 6.5" 400lb springs up front and 9" 700lb springs in the rear.
Appreciate 0
      01-14-2018, 12:04 PM   #16
bbnks2
Colonel
1207
Rep
2,025
Posts

Drives: 135i N55
Join Date: Jan 2017
Location: NY

iTrader: (0)

Quote:
Originally Posted by Kgolf31 View Post
Well, for one I said 6.5" Springs.

And yes, I know what your point is. But there is math and "sound calculations" and there are real life data points.

If you want, feel free to lookup my 128i results from campaigning in STX...on 6.5" 400lb springs up front and 9" 700lb springs in the rear.
I replied to Ryan who said 6." 6.5" and 400lb/in is close enough to seeing similar results to the two examples provided of 336 7" and 450 6."
Appreciate 0
      01-14-2018, 12:06 PM   #17
bbnks2
Colonel
1207
Rep
2,025
Posts

Drives: 135i N55
Join Date: Jan 2017
Location: NY

iTrader: (0)

Just some food for thought. Lots of people know that the front suspension is different from the rear. What they don't know is that lowering the front and rear does not produce the same affect on the moment arm. I'll let you figure out if you want the rear of the car higher or lower relative to the front... It will depend on wether you want load shifted forward or rearward in lateral transitions, of course.
Appreciate 0
      01-14-2018, 12:58 PM   #18
bionicbelly
Second Lieutenant
78
Rep
237
Posts

Drives: Z3 coupe, 128i
Join Date: Oct 2017
Location: Des Moines

iTrader: (1)

Thanks for all the input guys. I am going to start with 450 lb springs in the front with 6” length. Keep in mind that the ast’s have the upper perch on the strut shaft.
For the rear, it will be 800 lb 9” springs.
Probably have to play with it a bit, but it seems like a good place to start. FYI- it will be the stock bar in front. Might try a rear bar as well, but I want a torsen lsd, so May leave it off.
Appreciate 0
      01-14-2018, 01:02 PM   #19
bionicbelly
Second Lieutenant
78
Rep
237
Posts

Drives: Z3 coupe, 128i
Join Date: Oct 2017
Location: Des Moines

iTrader: (1)

Quote:
Originally Posted by bbnks2 View Post
Just some food for thought. Lots of people know that the front suspension is different from the rear. What they don't know is that lowering the front and rear does not produce the same affect on the moment arm. I'll let you figure out if you want the rear of the car higher or lower relative to the front... It will depend on wether you want load shifted forward or rearward in lateral transitions, of course.
Can you go more in depth on this? I know that on my z3 I found that a little rake helped with everything but braking. A touch more height in the rear that is. Seemed like the car always took a more solid set in the corner, and wasn’t as easily unsettled.
Appreciate 0
      01-14-2018, 02:58 PM   #20
bbnks2
Colonel
1207
Rep
2,025
Posts

Drives: 135i N55
Join Date: Jan 2017
Location: NY

iTrader: (0)

Quote:
Originally Posted by bionicbelly View Post
Thanks for all the input guys. I am going to start with 450 lb springs in the front with 6” length. Keep in mind that the ast’s have the upper perch on the strut shaft.
For the rear, it will be 800 lb 9” springs.
Probably have to play with it a bit, but it seems like a good place to start. FYI- it will be the stock bar in front. Might try a rear bar as well, but I want a torsen lsd, so May leave it off.
I use an 8" spring in the rear. a 9" might limit you in how low you can go in the rear but it really all depends on your particular coil over adjuster.
Appreciate 0
      01-16-2018, 02:55 PM   #21
lowside67
First Lieutenant
219
Rep
361
Posts

Drives: 2011 BMW 128i
Join Date: Apr 2015
Location: Vancouver, Canada

iTrader: (0)

A little late to the party, but I run:

Front Springs: Swift 7.0kg (392lb-in) / 7" length / 65mm ID
Rear Springs: Swift 12.0kg (672lb-in) / 9" length / 65mm ID

On the front, I have a custom spacer at the knuckle and this combination with the 7" spring works well as I have maximized spring travel (and minimized the risk of coil bind) - the spring is barely preloaded so we have maximum droop travel available.

I am thinking about a slight increase in rate - when I do this, if I had the option to do a 6.5" spring I would, but I think I will likely end up sticking with the 7" option which will fit the same as it does now but sit a bit higher on the ride height front.

On the rear, I could lower the car another 1/2" to 3/4" easily on my current adjusters so I believe the 9" spring is an ideal length without helper.

Cheers,
Mark

Ride height at rest:

__________________
Appreciate 0
      08-03-2018, 06:13 AM   #22
titium
Major
327
Rep
960
Posts

Drives: 2009 BMW 135i
Join Date: Jun 2015
Location: Sydney

iTrader: (0)

Quote:
Originally Posted by lowside67 View Post
A little late to the party, but I run:

Front Springs: Swift 7.0kg (392lb-in) / 7" length / 65mm ID
Rear Springs: Swift 12.0kg (672lb-in) / 9" length / 65mm ID

On the front, I have a custom spacer at the knuckle and this combination with the 7" spring works well as I have maximized spring travel (and minimized the risk of coil bind) - the spring is barely preloaded so we have maximum droop travel available.

I am thinking about a slight increase in rate - when I do this, if I had the option to do a 6.5" spring I would, but I think I will likely end up sticking with the 7" option which will fit the same as it does now but sit a bit higher on the ride height front.

On the rear, I could lower the car another 1/2" to 3/4" easily on my current adjusters so I believe the 9" spring is an ideal length without helper.

Cheers,
Mark

Ride height at rest:


What shocks are you running?
Appreciate 0
Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -5. The time now is 05:19 PM.




1addicts
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST