Replacement Shocks /Ride Height ? - Page 2

ASO544 · #21 (**permalink**) 10-03-2015, 05:32 AM

Quote:

Originally Posted by cbreez

They have oil surrounding the shock for cooling...you don't mean that I hope.

Yes....the oil is leaking out of the shock. It's running down the side of the body of the shock. Drivers side.

Kobura · #22 (**permalink**) 10-03-2015, 03:10 PM

This is kind of on this subject as it is related to shocks. I have test driven my car with both rear shocks removed. The ride was jouncy with a few large excursions of the rear, but still surprisingly firm as I could feel jarring from the small bumps along the test route I travel routinely. Most notable was that I never experienced bottoming of the suspension. I believe that my experiment points to the need for softer springs on my car as opposed to softer shocks if I want a ride that is closer to that of those fabled Bavarian machines.

cbreez · #23 (**permalink**) 10-03-2015, 05:03 PM

Remember that shocks add nothing to support the car. They don't add any spring rate at all. They control the bounce, period. I could see where you wouldn't bottom out on a smooth road, that's all a function of existing spring rate, load and cornering or other external force. Your springs have the same weight on them, shocks or no shocks. But try really driving hard without any or proper shocks, the oscillations will help you lose it!

You need to know your suspension/shock travel before you do anything with shocks or springs. Push down the rubber grommet on the shock shaft or use a tight, closely trimmed zip tie if your's are missing, and see how much travel you have.

ASO544 · #24 (**permalink**) 10-08-2015, 02:39 PM

I replaced both 1k mile Gabriels and one was dead... the other had a 5 minute rebound time..... : /

Jaydee · #25 (**permalink**) 10-08-2015, 05:58 PM

I haven't driven mine yet, but i have adjustable spaks shockers. So I'm hoping I can set them soft for everyday driving and tighten them up for racing. One question. If I have heavy duty spring set at the right height as apposed to soft springs that will compress to the right height, then the soft spring should still less jarring?
JD

Kobura · #26 (**permalink**) 10-09-2015, 11:21 AM

My aim is to install the softest springs that I can while maintaining proper ride height. My reasoning is based on my understanding of a simple spring-mass-damper system which those of us studied as an introduction to mechanical vibrations and dynamics in engineering or physics. The solution of the motion for such a simple system, which I admit is inaccurate for a car suspension, includes the critical damping ratio which can describe the amount of damping required to bring a vibration to a stop in the least amount of time without oscillation/overshoot. The solution is that the viscous damping factor/amount of damping is proportional to spring rate. Spring rate, on the other hand, is proportional to the natural frequency. So, my thinking is that I want a low natural frequency for a soft ride and enough damping to keep oscillations to a minimum or zero. So, I am going to try springs that compress down to the proper ride height while using my current shocks which are for a comparable light car(VW Bug).

avdcav · #27 (**permalink**) 10-09-2015, 11:32 AM

I agree with past posts wow that got ugly quick , but cbreez was correct
Shocks have nothing to do with spring rate in any way .

unless I was building for track beast
I normally find some used or old units and have bilstien custom valve them for me.
You just fill out the form send them in and bilstien will give you a quick phone call in a couple of
Days and whammy your custom valved shocks are on there way. It's less than a $100

But in fairness I do understand the other points , my 930's have over 15k in suspension goodies
In them and those cars will scare you in a corner. I own wireless scales so adjustments and balancing takes 20 mins.

My EM cobra is like fighting in a bull ring to adjust QA-1 funny seriously if you think QA1 are performance .
Suspension components it's probably best to bow out if this conversation.

In closing I will admit when younger I actually thought I understood vehicle suspension
But when you take your first ride in a 270k real race car you instantly go hmmmmm
I know nothing I am a fool and my car on the track is a danger to myself and those around me.

Hopefully someone who is a real cobra suspension person will jump in as this is a great
Topic that doesn't seem to come up often and provide real information for novice guys
To utilize and apply to there vehicles.

Talking motors all the time gets boring. Safe driving to all ...

fordracing65 · #28 (**permalink**) 10-09-2015, 09:50 PM

Quote:

Originally Posted by Kobura

My aim is to install the softest springs that I can while maintaining proper ride height. My reasoning is based on my understanding of a simple spring-mass-damper system which those of us studied as an introduction to mechanical vibrations and dynamics in engineering or physics. The solution of the motion for such a simple system, which I admit is inaccurate for a car suspension, includes the critical damping ratio which can describe the amount of damping required to bring a vibration to a stop in the least amount of time without oscillation/overshoot. The solution is that the viscous damping factor/amount of damping is proportional to spring rate. Spring rate, on the other hand, is proportional to the natural frequency. So, my thinking is that I want a low natural frequency for a soft ride and enough damping to keep oscillations to a minimum or zero. So, I am going to try springs that compress down to the proper ride height while using my current shocks which are for a comparable light car(VW Bug).

If springs compress they will become stiffer not softer...

Kobura · #29 (**permalink**) 10-10-2015, 09:03 AM

Apparently there are two types of car springs in common use: Those with a constant spring rate and those with a progressive spring rate. The progressive rate springs become stiffer with compression, the constant rate ones don't.

I may have not conveyed the reasoning behind my planned approach to modifying my BDR rear suspension very clearly because I gave a superficial summary of the spring-mass-damper system analysis. No differential equation, no exponential function, no imaginary number, etc. However, I think that my planned approach to achieving a more supple suspension is intuitively obvious in that a soft spring rate with minimum damping seems like the way to go rather than a stiffer spring with over damping.

What makes my situation difficult is that there doesn't seem to be a source of the BMW 'beehive shaped' rear springs with a softer spring rate. Moreover, the selection of a shock absorber is kind of a crap shoot in that the damping factors for shocks is not stated/known. I know that a couple of CC contributors have shown photos of modification of their BDR rear suspensions to coilovers which allows great freedom in spring and shock selection, especially with variable compression and extension damping shocks. However, I have not reached the point of spending that kind of money to solve my issues...yet.

Kobura · #30 (**permalink**) 10-10-2015, 09:05 AM

Duplicate post.

Cashburn · #31 (**permalink**) 10-10-2015, 09:23 AM

We have billet saddles that fit aftermarket 2.5" springs. They drop right in the place of the beehives.

Kobura · #32 (**permalink**) 10-26-2015, 03:55 PM

I have put a couple hundred miles on my new rear suspension setup and it seems like it is as good as it gets. The ride can still be quite jarring but overall the ride is noticeably smoother while still maintaining good control and handling on the twisties.

I switched to 10" long, 300 lb/in, 2.5" coil springs by installing the saddles/perches provided by Jay/VMS and replaced the Monroe 31412 shocks with the KYB 343144 shocks mentioned in a previous post. The ride height adjusters are backed up to the frame producing a couple of fingers of clearance with the fender cutouts.

The saddles/perches are precision parts that fit perfectly. They have to be regarded as additional testaments to Jay/Brian/VMS standup support for us BDR owners.

BTW, if anyone needs BMW beehive shaped springs (either OEM or softer BMW 318i), rubber supports, metal washers, OEM Gabriel G45419 shocks, or the Monroe shocks for their BDR, they can be had for shipping cost.

Richard

cbreez · #33 (**permalink**) 10-27-2015, 12:59 AM

TURNER MOTORSPORTS has a great selection of various ways to further spend your money on shocks and springs if one so desires...very smart and experienced folks too!
Keep it simple...

MJC · #34 (**permalink**) 10-30-2015, 02:44 PM

Quote:

Originally Posted by itstock

Hopefully this doesn't come off as a dbag, but if you want a smooth ride, why did you pick this car? I have a couple of roads around me that I literally have to avoid do to chatter, but I understand that and it's not an issue. If all of your roads are like the one road that I absolutely despise that is right outside of my neighborhood, then I would sell the car and never consider driving it again. The car as it is stock, is a good mix of road/driveable and race IMO. If you don't like the quirk of having a somewhat stiff suspension because of roads, I guarantee you a million other issues are going to come along as well do to ****ty roads.

It isn't my only car to hobby around in. I just like to take it out when I get bored of creature comforts. What I'm really complaining about is that it feels like something on the car is gonna break considering how stiff it is.

I know some tuners sell a suspension upgrade to soften it up here in the northern states. However they all want you to ship them the car and thats not an option as I'm tearing it down for a built motor this winter. Apparently the only people qualified to work on cars is the tuners....they dont like to sell you parts. lol

Cashburn · #35 (**permalink**) 10-30-2015, 03:17 PM

Quote:

Originally Posted by MJC

It isn't my only car to hobby around in. I just like to take it out when I get bored of creature comforts. What I'm really complaining about is that it feels like something on the car is gonna break considering how stiff it is.

I know some tuners sell a suspension upgrade to soften it up here in the northern states. However they all want you to ship them the car and thats not an option as I'm tearing it down for a built motor this winter. Apparently the only people qualified to work on cars is the tuners....they dont like to sell you parts. lol

Our system requires some machining and some welding to fit given the current Backdraft factory spec... 2 things you are not going to do without complaining

MJC · #36 (**permalink**) 11-14-2015, 09:51 AM

Quote:

Originally Posted by Cashburn

Our system requires some machining and some welding to fit given the current Backdraft factory spec... 2 things you are not going to do without complaining

Haha true.

Are the stock springs a linear or progressive rate? What is the VMS suspension?

Cashburn · #37 (**permalink**) 11-14-2015, 01:14 PM

Quote:

Originally Posted by MJC

Haha true.

Are the stock springs a linear or progressive rate? What is the VMS suspension?

Stock are linear. We have done the progressive fronts. Our suspension upgrade includes springs, billet saddles, front struts, rear shocks, and sway bar mounts (front).

Late Apex · #38 (**permalink**) 10-30-2016, 04:10 AM

KYBs a must have. On my new BDR I just had the rear OEM junk shocks replaced with the KYBs in the back and it improved the driving experience 100%. Smoother ride and no wheel hopping when hard on the throttle. These are very inexpensive and well worth changing them out. Adjustable too!

Steve Gallegos · #39 (**permalink**) 10-30-2016, 03:47 PM

Late Apex what is the part # for the rear KYB's Thanks

Late Apex · #40 (**permalink**) 11-05-2016, 07:50 AM

My invoice only says KYB gas adjustable shocks but if you call James at Radical Roadsters of Texas in Tomball Tx. he can give you the exact part number.