Official BC Coilover Kit Development Interest.

[rbryant]

The rear springs are stiffer than the fronts on G/J/P/etc-body cars because of the suspension design. The wheels have more leverage on the spring because of it's location. On chilort's Daytona we are trying out 325lb frt/375lb rr springs, but he is planning on road racing it and doesn't much care about a soft ride on the street.

Interesting point. Perhaps I missed something there being from the lbody crowd.

Well we can certainly go with stiffer rear springs if that is what works best on the non lbody.

I did start to do some calculations to figure out the stock rear rates based on the spring free and compressed heights once and dismissed them because the rates were coming up too high in the rears and I thought I was missing something. I will have to go back and repeat that now to see if they were right after all but it is still very difficult to compare progressive and linear spring rates so it still might not be possible to calculate.

This non coilover rear spring setup on the non lbody continues to be a pain in my side.

-Rich

[Force Fed Mopar]

Interesting point. Perhaps I missed something there being from the lbody crowd.

Well we can certainly go with stiffer rear springs if that is what works best on the non lbody.

I did start to do some calculations to figure out the stock rear rates based on the spring free and compressed heights once and dismissed them because the rates were coming up too high in the rears and I thought I was missing something. I will have to go back and repeat that now to see if they were right after all.

This non coilover rear spring setup on the non lbody continues to be a pain in my side.

-Rich

Lol, well I thought it was you that told me that, but I guess it was someone else But yeah, before that I couldn't figure out why the rear rates were always higher for non-L-body cars. After hearing it it made sense. The other thing is, the spring rates for all the different springs for them have a large variance in the front and rear rate differential. Some are nearly the same front and rear, while others have a 70+ lb difference. The rates are all listed in the Stock Suspension FAQ I created and maintain over on BM, if you want to study it.

[rbryant]

Lol, well I thought it was you that told me that, but I guess it was someone else But yeah, before that I couldn't figure out why the rear rates were always higher for non-L-body cars. After hearing it it made sense. The other thing is, the spring rates for all the different springs for them have a large variance in the front and rear rate differential. Some are nearly the same front and rear, while others have a 70+ lb difference. The rates are all listed in the Stock Suspension FAQ I created and maintain over on BM, if you want to study it.

Hmm...

I remember a discussion about how the leverage was "different" and I might have mentioned it but I never realized that they actually came with stiffer rear springs from the factory. For some reason it is easy to find lbody spring specs but the non lbody is harder to find.



If you look at the rockauto specs they state the following:

Front:

Free Height 17.7" to 17.3" depending on the spring
Compressed Height 12"

If we assume that the springs are linear in that range and the car weighs around 3000lbs with 60% of the weight on the front:

900/5.7 = ~158lb/in
900/5.5 = 163.6lb/in
900/5.3 = ~170lb/in (used on the passenger side to offset the weight of the AC)

All of that seemed fine to me...


The thing that seems way off is the rears:

With 40% of the weight left we have 600lb per side

There are 3 variants that I see:

RAYBESTOS Part # 5911035
Free Height: 11"
Compressed Height: 9"

600/2" = 300lb/in (that doesn't seem right so I stopped my calculations)


Now that I look at them there are more springs available that make more sense


RAYBESTOS Part # 5911003
Free Height 11.8"
Compressed Height 8.4"

600/3.36 = 176lb/in (reasonable).


RAYBESTOS Part # 5891076
Free Height=12.19"
Load height=8.44"

600/3.75 = 160 (also reasonable)

So prehaps the bottom line is that the non lbody might be better with a more even spring setting of 6k/6k or 8k/8k.

All of these calculations are highly dependent on the springs being linear for the first part of their travel and the weight ratio being right.

-Rich

[Reaper1]

A long time ago I thought it was found out that the P-body Eibach's were rated like this: 300fr/330r (of course this is the linear part of the spring).

[rbryant]

A long time ago I thought it was found out that the P-body Eibach's were rated like this: 300fr/330r (of course this is the linear part of the spring).

One other thing to consider is that we are making the adjuster align the spring angle. This will nearly eliminate the bend that the stock springs have. I will look into it but I would guess that the bow in the springs also affects the rates, leverage, etc and changes things.

-Rich

[Reaper1]

I agree. I've been thinking about a spring perch that pivots to keep the spring from being at an angle throughout the suspension travel. I've had this idea for a few years. I've seen something similar on a Mercedes IIRC.

[BlueBaron]

I had the crazy thought of urethane springs. They'd be a cylinder. Far too much R&D, including new measurement equipment for me to tackle though.

[rbryant]

I had the crazy thought of urethane springs. They'd be a cylinder. Far too much R&D, including new measurement equipment for me to tackle though.

Perhaps a very large spherical bearing or better yet a ball joint (so that it is sealed) on the adjuster...

That should allow for 10 degrees or more of automatic spring adjustment. The spring would want to stay straight so it would automatically move the joint similar to how a strut works.

Perhaps a ball joint that is already bolt on with a threaded shaft would be a nice solution. The ball joint would be cheap and should easily handle the load.

I am sure there is a simple old school threaded ball joint out there that can bolt on with just a few holes drilled into the frame... Probably for a F0rd or Cheby would work best.

Then I don't have to worry so much about the spring angles on my adjusters being a compromise either.

-Rich

[Force Fed Mopar]

I agree. I've been thinking about a spring perch that pivots to keep the spring from being at an angle throughout the suspension travel. I've had this idea for a few years. I've seen something similar on a Mercedes IIRC.

Perhaps a very large spherical bearing or better yet a ball joint (so that it is sealed) on the adjuster...

That should allow for 10 degrees or more of automatic spring adjustment. The spring would want to stay straight so it would automatically move the joint similar to how a strut works.

Perhaps a ball joint that is already bolt on with a threaded shaft would be a nice solution. The ball joint would be cheap and should easily handle the load.

I am sure there is a simple old school threaded ball joint out there that can bolt on with just a few holes drilled into the frame... Probably for a F0rd or Cheby would work best.

Then I don't have to worry so much about the spring angles on my adjusters being a compromise either.

-Rich

Hmm, those are good ideas. I am working on building the rear coil-overs on chilort's '86 Daytona right now, and having been researching/thinking about how best to do it. I was thinking of re-designing the lower spring perch to be slightly deeper and and different angle for the adjuster sleeve to sit into, but a pivoting lower perch might be the way to go. Be easy to do too, relatively speaking.

[rbryant]

Hmm, those are good ideas. I am working on building the rear coil-overs on chilort's '86 Daytona right now, and having been researching/thinking about how best to do it. I was thinking of re-designing the lower spring perch to be slightly deeper and and different angle for the adjuster sleeve to sit into, but a pivoting lower perch might be the way to go. Be easy to do too, relatively speaking.

If we just added one of these:
http://www.speedwaymotors.com/search...ing-perch.html


Between two rod ends (with the threads bolted downward through the spring pad) it would probably work with my existing design.

It would just make it about 1" taller so if someone wanted to slam the car they might need a shorter spring.

-Rich

[Reaper1]

I thought about using a plate that rides on a pivot where the axle of the pivot would be in double shear. The axle would be attached to a frame that would be welded to the rear axle. My only concern would be transferring the load to the axle without overloading the frame.

[iTurbo]

Then I don't have to worry so much about the spring angles on my adjusters being a compromise either.

-Rich

I applaud you guys for giving so much thought to this particular subject regarding the rear springs, and I admit it's very possible you are all far smarter than I am. However, I think you guys might be overthinking things here. My opinion is that if we can zero in on the best lower spring seat adjuster angle, then 95% of people buying these will be happy. Consider the fact that additional parts such as some kind of pivoting lower spring seat or ball joint to do the job, such as would be required to optimize rear spring angle throughout it's travel, would both increase the cost *and* chance of component failure. Also realize that since the lower spring seat angle in it's stock form is fixed without modification that it is always going to be a compromise since the angle changes throughout it's range of motion.

I myself and Warren Stramer (csxtra) have test fitted Rich's rear spring adjusters for the K-based cars on our own cars. Warren did in his '87 CSX and I did on my '87 Shelby Lancer with pics posted previously in this thread. Initially Rich, by way of a very edjumacated guess, thought that a 20' angle on the lower spring seat would work well on our cars. Warren test fit them first on his CSX and stated earlier in this thread that 15' would be better. Later, I test fit Rich's adjusters on my SL and personally I thought that something between 10-15 degrees would be better for my car. If I had to guess I would say 12.5 degrees might be perfect but it's impossible to say without further testing. I sent my rear spring adjusters back to Rich and they are being modified and will be retested by me as soon as they return!

That being said, It's my opinion that a pivoting lower spring seat would be somewhat overkill but I absolutely think it's interesting to read about. I would like to see the BMW setup Reaper1 mentioned...although as far as practicality I am skeptical. Rich is correct when he states that there is a enough offset that the stock springs on the K-based cars 'bend', as I have witnessed this on my own Shelby Lancer with stock and Eibach coil springs. Think about it, with the factory design of the rear axle, the lower spring seat angle is constantly changing in regards to the upper spring seat since it pivots. No matter what angle the lower spring seats are made it is a compromise just as Rich has stated. This is because the relationship between the upper and lower spring seats is constantly changing throughout it's travel up/down.

As soon as I get my revised rear spring adjusters back from Rich I will retest them on my Shelby Lancer and post pics. The first set I received from Rich were 20', and if you look at my previous posts they were a bit too much as far a angle. Warren thought that 15' degrees would be good. He may very well be right....although it is my opinion a bit less angle would be ideal compared to the Eibach spring set....we shall see as more testing is required.

[iTurbo]

Also, as far as the L-body BC Coilver kit is concerned....I recently bought a set from Rich for my own GLH Turbo. I have recieved the entire kit but have yet to test fit it to my Omni. Previously Bryan (black86glhs) got these but they were ordered with the DSM rears. The kit I bought (following further development) came with Toyota Tercel rear BC struts.

With the DSM style rear struts that Bryan got, a custom lower rear bushing from PolyBushings was required. I have yet to test fit the Tercel version BC rears to my Omni, but I have done some preliminary testing with an L-body rear axle out of an '85 Shelby Charger. So far it looks like the custom bushing will no longer be required, although a different bushing sleeve will be. The bushing sleeve that came in the Tercel BC rear struts are too short to fit the rear axle, and the ones that Rich sent with the kit are the right length to fit the L-body rear axle but they are too large diameter to fit the strut bushing eyelet. Considering my past experience getting the QA1 rear shocks to fit my Shelby Lancer, I am confident this problem can be overcome easily as soon as we find the right bushing sleeve.

I really gotta get my Omni GLH Turbo out of the garage!!! It's been in there since about '06. Problem is the garage it's in is too small to do test fitting of these parts so hopefully I will be able to pull it out soon and get it in our shop for some real work. Will post pics soon, don't want to keep you guys waiting. These BC Coilover kits that Rich is putting together are NICE!!

[Force Fed Mopar]

Actually, if I am thinking correctly, the angle gets smaller as the suspension compresses. If you have it sitting on jackstands with the wheels hanging, that is the most angle it will see. I'll have to go look at my Lebaron, but I'm betting there is very little angle when the car is resting w/ full weight on the wheels. What angle there is, is probably from the top spring perch.

[black86glhs]

Also, as far as the L-body BC Coilver kit is concerned....I recently bought a set from Rich for my own GLH Turbo. I have recieved the entire kit but have yet to test fit it to my Omni. Previously Bryan (black86glhs) got these but they were ordered with the DSM rears. The kit I bought (following further development) came with Toyota Tercel rear BC struts.

With the DSM style rear struts that Bryan got, a custom lower rear bushing from PolyBushings was required. I have yet to test fit the Tercel version BC rears to my Omni, but I have done some preliminary testing with an L-body rear axle out of an '85 Shelby Charger. So far it looks like the custom bushing will no longer be required, although a different bushing sleeve will be. The bushing sleeve that came in the Tercel BC rear struts are too short to fit the rear axle, and the ones that Rich sent with the kit are the right length to fit the L-body rear axle but they are too large diameter to fit the strut bushing eyelet. Considering my past experience getting the QA1 rear shocks to fit my Shelby Lancer, I am confident this problem can be overcome easily as soon as we find the right bushing sleeve.

I really gotta get my Omni GLH Turbo out of the garage!!! It's been in there since about '06. Problem is the garage it's in is too small to do test fitting of these parts so hopefully I will be able to pull it out soon and get it in our shop for some real work. Will post pics soon, don't want to keep you guys waiting. These BC Coilover kits that Rich is putting together are NICE!!

Jeremy, you'll get it figured. I totally forgot about the tercel stuff working on the omni. That gives us 3 different setups that can be easily modded to run in our cars. Awesome work guys.

[iTurbo]

Thanks Bryan. I was aware of the DSM rears being an option and had already bought the rear/lower bushings from polybushings.com, but Rich/I wanted to investigate the Tercel possiblity so I went with those instead. So far it *looks* like the custom lower bushing will not be required, but no promises as I still have to test fit on the actual car rather than this bare Shelby Charger rear axle in my bedroom..I will also look into mag lug nut top being required or not.

BTW...I was aware of the DSM rears (and now Tercels), but what is the 3rd possible rear setup you alluded to??

And tonight I was rereading my post and I hope none of you took it the wrong way. The way I see it, you all and mostly Rich are the brains behind all this stuff and I'm just the test-fitter! So I hope I didn't come off too harsh because I really do like reading others ideas so forget whatever I said! I sure as hell wouldn't have thought of a pivoting or ball joint equipped lower seat. Although I must say I'm happy thus far with Rich's rear spring solution for the K-based cars.

[Force Fed Mopar]

No offense taken here

Looking at my Lebaron, the lower spring seats are parallel to the ground with the car at rest. So most of the angle is in the top spring seat. I'm thinking a bolt-on upper spring seat that eliminates the angle (or at least alleviates it) may work good.

[Reaper1]

No offense taken here, either. I'd like to figure out how the rate of a spring is affected by the angle from wish the force is applied to it. That would answer our questions and set us up for a real solution vs. Just guessing. Honestly that isn't something they cover in classes and I've not seen it mentioned in books, so I might have to do some more research to figure this out.

[rbryant]

Thanks guys as with everything in our hobby we are constantly evolving and brainstorming new things. As soon as something works many of us (myself included) have some sort of affliction that requires us to try and make it better.

I agree that the rear perches at some angle between 13 and 16 will be a very good setup that will work for everyone and it is actually cost effective.

Ideas like the articulating spring seat could be nice or they could be a disaster due to the extra complication. I think they are something that we can try later on and are certainly not required. The discussion is what makes the hobby fun so while perhaps it should be in a different thread I greatly value the open discussion.

I strongly feel that we have already come up with the best bolt on coilover kit out there and it is ready (or nearly ready) for "mass" production. IN our world "mass" might still mean only 10-20 sets but that is what makes us a really unique niche group.

I greatly everyone that have taken their time to help develop these and taken some risk/reward on them. Without that cooperation this would never have happened. The continuing effort on things like testing the Tercel rears insted of the DSM rears is aimed at making a great product better. There will be no change in functionality it is simply an attempt to make everything more bolt on with less custom bushings, eliminating offset bushings, etc.

This is a great discussion on spring rates, etc lets keep it going so we can all get the best possible product configuration.

-Rich

[black86glhs]

Thanks Bryan. I was aware of the DSM rears being an option and had already bought the rear/lower bushings from polybushings.com, but Rich/I wanted to investigate the Tercel possiblity so I went with those instead. So far it *looks* like the custom lower bushing will not be required, but no promises as I still have to test fit on the actual car rather than this bare Shelby Charger rear axle in my bedroom..I will also look into mag lug nut top being required or not.

BTW...I was aware of the DSM rears (and now Tercels), but what is the 3rd possible rear setup you alluded to??

And tonight I was rereading my post and I hope none of you took it the wrong way. The way I see it, you all and mostly Rich are the brains behind all this stuff and I'm just the test-fitter! So I hope I didn't come off too harsh because I really do like reading others ideas so forget whatever I said! I sure as hell wouldn't have thought of a pivoting or ball joint equipped lower seat. Although I must say I'm happy thus far with Rich's rear spring solution for the K-based cars.

I think(bad idea depending on the time of day....lol) the other one was the VW setup. I may be thinking of the fronts, but I thought the rears were close too.
Rich, am I thinking right?