Dobinsons 3 inch Progressive / Flexi coil review

[half k cruiser]

I figured I will start recording my thoughts here in case anyone else is interested or I need to review later on. This is going to be a straight up comparison, apples to apples of the OME J lift and the Dobinsons lift.

Before:
Old Man Emu 850J front / 863 rears
OME sway bar drops
Fox 2.0 shocks 985-24-076 front 985-24-087 rear

Here's a few trail shots to get an idea of the look. I wasn't able to find many with the flex but you can see that the rear was doing just fine.

Talking with @David Otero of Dobinsons USA made me realize that they have a staggering amount of suspension offerings. Personally I find there suspension catalogue to be rather confusing so it was easier for me to just email him for the information I required.

I in no way think the OME setup is a bad lift. There's a reason its so popular right ? However, for an upcoming trip I was ready to try something different. My main goal being to smooth out the ride and secondary goal increase articulation off road. After David and I talked for a while we settled on 3" progressives front and rear

Now, Dobinsons considers this a "progressive" rate coil. Based on what I currently know about springs, I would say it is more like "dual rate". Unlike say, a TJM progressive, the distance between coils does not change the length of the spring. You can clearly see there is a ride rate at the top, and a load rate from there down.

 

[half k cruiser]

Ok, so lets compare, here are the part numbers for those interested.

They are roughly an inch longer than the OME springs that came off. I initially tried to get before and after measurements from center of hub to bottom of fender but the tires got in the way and I didn't have a helper. I will try and get the after measurement at least for future reference.

 

[half k cruiser]

Install is pretty straight forward. If you have swaybars, disconeect them. Also go rent a Mchpherson style spring compressor unless you like to scratch and dent your springs into place. Once everything was in place I could tell the rear had come up slightly and the front "appeared" the same to me. Here's a good shot of the load rate on the front. About enough room to slide a few playing cards in between those top two.

The best shot I could get of the rears. They are not settled into the ride rate nearly as much as the front. However, this was taken before I put the spare tire back on.

The green really isn't that bad color wise, I'm starting to get used to it.

I know these aren't the best quality photos I've taken. However, its cold and dark here in Kansas, so we are gonna make do until I get out someplace sunnier or the weather changes. I will update with driving impressions here shortly.

Its worth mentioning that David, the vendor for these springs, has been great. He gave me his honest thoughts and concerns when we spoke on the phone. He was aware that I was on a time crunch and needed the springs quickly, and he got them out as soon as I paid him. Also of note, the Dobinsons swag is quite good. The hat and shirt that was included in my order are of surprisingly good quality.

 

[half k cruiser]

Ok, I installed everything Saturday and have been driving it since then. Initial driving impressions: the ride is softer than it ever was with the OME. The smaller stuff like road corrugations, minor dips, potholes are all much smoother than before. The big stuff, like speed bumps, or badly misaligned expansion joints still hit hard. Not jarringly hard by any means, I'm not getting my teeth rattled. Its more of a firm, dampened hit.

The one thing that takes the most getting used to is the truck wants to float more on big dips. I can definitely feel the springs want to stretch down into them, then when they come up the other side you get a good bounce up and the truck levels out. Since I don't have much experience yet with dual rates I am going to assume that I am feeling the transition between load and ride rate. Perhaps @GW Nugget can share his thoughts on that.

Also, I'm pretty sure the front end raised a bit. My steering is now pulling to the left. I attribute this to greater distance between axle and top spring mount. Therefore my stock drag link is now being stretched to the limit of its old adjustment. This would cause it to pull the inside of the RH tire towards the steering box. Luckily I have a replacement drag link and ends that will be going on soon.

 

[Box Rocket]

Those would still be a progressive rate coil. Just because the winds get tighter doesn't make them dual rate. The only way to get dual rate on an individual coil is with tapered wire like on the Slinkys, where not only do the winds get tighter but the wire itself gets smaller in diameter.

 

[baldilocks]

Thanks for the write up. As far as hitting big dips, maybe those springs would be best paired with Dobbinson shocks.

Are those tires 35's?

 

[half k cruiser]

Those would still be a progressive rate coil. Just because the winds get tighter doesn't make them dual rate. The only way to get dual rate on an individual coil is with tapered wire like on the Slinkys, where not only do the winds get tighter but the wire itself gets smaller in diameter.

If you change the distance between windings you are effectively changing the rate are you not? It seems that you could then have a dual rate coil in one of two ways. Either you adjust the distance, or you taper the wire diameter so you have a weaker spring at the top of the coil. They both do the same thing, adjust the rate. The difference is the tapered wire is going to allow longer free lengths.

Thanks for the write up. As far as hitting big dips, maybe those springs would be best paired with Dobbinson shocks.

Are those tires 35's?

Lol, you sound like David. But I agree, the Fox shocks have always been a stop gap for me between the OME shocks and a fully adjustable unit. They are good for a non reservoir shock, and the price was right. Eventually though, to get the ride I want I will need to upgrade to the big stuff. Much like springs it appears there is going to be a profusion of shock offerings for the 80 at some point this year. Of course Icon, King, and Radflo already have them. I know Trail Tailor is bringing in a new brand and Dobinsons will be releasing an updated MRR later this year. I think the best thing will be to wait and see what all the options will be. Those are 315/75/16 Kuhmos.

 

[baldilocks]

I hope a Mudder near me buys one of these fancy suspension set ups and allows test drives. Just when I thought i was content the market tells me otherwise.

 

[Box Rocket]

If you change the distance between windings you are effectively changing the rate are you not? It seems that you could then have a dual rate coil in one of two ways. Either you adjust the distance, or you taper the wire diameter so you have a weaker spring at the top of the coil. They both do the same thing, adjust the rate. The difference is the tapered wire is going to allow longer free lengths.
.

You are describing a Progressive spring, like what you have. Tighter winds are only part of a dual rate spring, the smaller diameter wire is what allows for a secondary spring rate through part of the range. There are three types of coils, linear, progressive and dual rate that are the most common for any of us to be dealing with.

“Linear rate springs” have one defined spring rate per inch of deflection throughout most of their range of deflection. For instance, if we have a 300lb/in linear rate spring that is 12 inches long, it will take approximately 300lb to deflect it 1 inch. The next inch of deflection will take another 300lb of load and the next inch of deflection will take an additional 300# of load (and so on until the spring goes solid). At this point there will be 900lb of load on a 12 inch long spring that has now been compressed to a 9” spring height.

The “linearity of rate” makes it quite easy to calculate a given spring length at ride height and this helps in setting up the ride height of a specific vehicle. If we know that we have 750lbs of sprung mass on a corner and we want to run a 250lb/in linear rate spring; we know the spring will compress 3 inches (750lbs ÷250lb/in = 3 inches). That helps us anticipate the total travel of the spring. Also, by measuring the total travel of the damper, we can easily estimate the total load placed on the spring during an event.

OME springs are linear rate.

“Progressive rate springs” are generally classified into two sub-types: 1) constantly increasing rate springs and 2) a “dual-rate” spring with two linear rates connected with a rate-transition range.

The first type (constantly increasing rate) of springs are most often used as “load-compensating springs” on the rear of a vehicle when the vehicle will often see significant load changes in the cargo area. These are most often stock replacement type suspension springs. They are identified most easily by continually varied spacing between the coils. One area of racing where constantly increasing rate springs are used is dirt modified racing where pull-bar springs, using a constantly increasing spring rate, are used to control rear axle wrap during acceleration. These springs are not suspension main springs, but are supplemental springs.

The particular Dobinsons are Progressive rate.

The second type of progressive rate suspension springs, the dual-rate spring with two linear rates connected with a rate transition range is a much more sophisticated suspension spring. The design is much more focused on the specific use for the spring. These types of springs are used primarily in road racing and high performance street and GT applications where the vehicle trim package will stay in a very predictable range. These springs are easily identified by having a few closely wound coils at one end and then wider, equal spaced coils at the other end. They have rates described as 200/425lb/in. This means that the spring has an initial rate of 225lb/in through some range of deflection and then the rate transitions to 425lb/in through a deflection range of 1”-1.5.” The big advantage of these springs is that they can provide “roll control” in addition to roll control provided by sway bars.

Slinky or Icon springs are Dual rate.

 

[scrowley]

Great write up. Hopefully a lot of ppl will dump there thoughts on this thread.

I've been wanting to swap out my worn in J's as well. But I think I will wait around this year and see what comes up. The slinky's interest me but these dobinsons do as well.

Oh, and IMO the color of these springs is a big turn off. Totally retarded they paint them like that. What's wrong with black?! I don't like flashy stuff. Black and white kinda person. Just throwing this out there.

 

[half k cruiser]

Oh, and IMO the color of these springs is a big turn off. Totally retarded they paint them like that. What's wrong with black?! I don't like flashy stuff. Black and white kinda person. Just throwing this out there.

The color isn't that bad in person. Plus, it would be super easy to shoot them with some Rustoleum black if that's the only hold up.

 

[rockstate45]

I hope a Mudder near me buys one of these fancy suspension set ups and allows test drives. Just when I thought i was content the market tells me otherwise.

Something tells me that @half k cruiser will have a pretty long line waiting to drive or ride in his at the next meet.

For

 

[Box Rocket]

I'm not meaning to derail the review of the Dobinson's with the discussion on progressive rate vs dual rate but its important for those reading the thread to understand what they are getting and what type of performance it will have if they decide to consider these springs.
Progressive rate springs have many good traits so I'm not sharing any of this information to "bash" the Dobinsons or any other progressive springs. Just describing differences.

Here's a link to another good description of the differences in linear, progressive, and dual rate coils. Disregard that the link says "jeep clothing Jeep Shirts"



Jeep Clothing Jeep Shirts

BTW @half k cruiser you've got a good looking truck. I like the fuel can swing out. Custom built or something from 4x4 Labs?

 

[baldilocks]

Post #3 shows the top few turns pretty much completely compressed which leaves it a single rate spring in the course of regular driving. All wraps below the "progressive" portion are equally spaced and appear to be the only ones suspending the vehicle.
I spoke to Chriso Slee a while back about their 4" progressive rear coils after I bought a set from a wrecked 80. He told me that the progressive portion of the spring had more to do with how it worked with the shock than how it would ride unloaded.
Once the high rate portion is completely extended the lower rate portion would continue to expand thereby retaining the spring. This also allows us to run longer shocks and attain the flex that many think is paramount.

 

[FloridaFJ80]

I've had the Dobinsons Linear rate springs on my 80 with the MRR shocks. I have been really happy with the setup. Dobinsons have a wide array of spring applications for the 80 series. Truck handles great on and off road. I really recommend the Dobinson setup. I have had the J's and can say that the Dobinson setup was a lot smoother.

Glad to see a fellow mudder try a new suspension setup and get out of the status quo when it comes to suspension for the 80 series.

 

[Sharky1528]

Lots of Great info here !!!!

 

[half k cruiser]

I also do not want to derail this review, however, I will have to disagree with @Box Rocket as to these being progressive springs. In actuality anything other than a linear rate will be "progressive" so it is somewhat semantics. However, the top coils have the same spacing, the next set of coils have a different spacing, but they are consistent all the way to the bottom of the spring. Therefore you have two different rates and only two rates.

What most people think of as a "progressive" rate spring will have spacing that increases all the way to the bottom of the spring. In that case you can't say its a 160/260 spring rate because it depends on where the coil is in its travel. The TJM springs were a good example of this. You could clearly see that the last two coils in them had the widest spacing and were therefore the stiffest rate. The illustration above is not the best example of this because its very difficult to tell that the coils are getting "progressively" spaced out. However the website where that information came from does a good job of describing the differences.

@rockstate45 , Jack, your welcome to take her for a spin !

 

[1973Guppie]

Am I correct in thinking that progressive and dual rate springs are not really made or good at carrying a heavy load? My truck has back. I carry 2 kids, a big dog, a wife, 3 cans of fuel, propane tank, labs bumper, jack, rear tire, etc. I have to have load carrying capacity. On top of that I tow sometiimes as well. I currently am running j springs front and rear.

 

[baldilocks]

Am I correct in thinking that progressive and dual rate springs are not really made or good at carrying a heavy load? My truck has back. I carry 2 kids, a big dog, a wife, 3 cans of fuel, propane tank, labs bumper, jack, rear tire, etc. I have to have load carrying capacity. On top of that I tow sometiimes as well. I currently am running j springs front and rear.

You didn't even mention camping gear, food, ice, tools, etc. sounds like your J springs are hating life.

 

[1973Guppie]

You didn't even mention camping gear, food, ice, tools, etc. sounds like your J springs are hating life.

no s***, I am the definition of "kitchen sink", 2 kids, wife, 135 pound dog, gear, food, tent trailer, 3 cans fuel, propane, jack, ax, shovel, rear sleep platform, arb fridge, yadda yadda yadda