OEM coil spring rates for Toyota 4wd vehicles

[Whitey Shockie Maker of the Month Award Find all posts View Profile Close Whitey]

Hey everyone,

After spending many hours hunting down OEM coil spring rates for various old and new vehicles, I thought it would be a great idea to keep a table of OEM rates for Toyota 4wd vehicles.

There are two figures for the coil spring rates, the first is calculated from the spring rate equation;



G = torsional modulus = 75800N/mm2 (spring steel)
d = wire diameter
Na = number active coils
Dm = mean diameter = inside diameter + wire diameter

Using industry standard, the number of inactive coils is 0.75 at each end, or 1.5 in total. This is the same no matter the type of end, ground flat or open. You can also note that the 0.75 inactive end approximation is always quite close by observing the marks on the coil ends where they rub on the coil buckets. The wire diameter should be measured on every coil wrap and then averaged, as the diameter can vary by up to 0.5mm across all coil wraps. Note my measurements now exclude the powder coat.

120/Hilux/150/FJ coils;





Landcruiser coils;





The second figure for OEM coil spring rate has been determined by load testing at King Springs. Here is a video showing how Dobinsons manufacture their coils, you can see the load testing performed at the 4:20 mark, where the coil is fully 100% compressed to solid coil height;

https://www.youtube.com/watch?v=en8Q...&nohtml5=False

Many thanks to John at Zordos Suspension for providing OEM coils for measurements, and to Steve at King Springs for load deflection testing of 12 coils.

If anyone has their pre 2015 OEM 150 petrol coils, if you’re willing to donate them to my coil collection could you PM me so I can complete the table. I’d also like to get some earlier Hilux coils from 05/06, as I suspect they have changed free height and spring rate slightly up to the 2015 coils I have measured. Same applies for Landcruiser coils, if you have some, please let me know!

This is a work in progress, so I’ll update the table every time I get some new data.

Best

Mark

[Whitey Shockie Maker of the Month Award Find all posts View Profile Close Whitey]

Hey all,

I've updated the table today after chasing down some 120 coils.

The 120 coils are from a 2006 diesel, and I was surprised to find the front coils have two different rates (due both to different wire diameter and number of wraps), similar to the setup in FJ's and 200 series.

The PP suspension database has only ever quoted a single OEM spring rate for the 120 front coils, so it has me wondering if the diesel and petrol coils are different. The deflection test value from Dobinsons of 605lb/in is also substantially lower than what I measure by the spring rate equation.

Similarly, the value Dobinsons have for the Hilux front coils is also much lower.

It's possible that the value I am using for G is not correct, but this value may be impossible to find from Toyota. The extra powder coat thickness may also slightly modify the final spring rate.

I'll see if I can get the correct value for G from Toyota, but this may be difficult. G can be calculated backwards from the load deflection values, but this may vary quite a bit.

More updates to come in the future!

Best

Mark

[ejukated Senior Member Find all posts View Profile Close ejukated]

interesting.. I guess one variable could be eliminated by sanding off the powercoat.

[damo73 Lurker Find all posts View Profile Close damo73]

Hey all,

I've updated the table today after chasing down some 120 coils.

The 120 coils are from a 2006 diesel, and I was surprised to find the front coils have two different rates (due both to different wire diameter and number of wraps), similar to the setup in FJ's and 200 series.

The PP suspension database has only ever quoted a single OEM spring rate for the 120 front coils, so it has me wondering if the diesel and petrol coils are different. The deflection test value from Dobinsons of 605lb/in is also substantially lower than what I measure by the spring rate equation.

Similarly, the value Dobinsons have for the Hilux front coils is also much lower.

It's possible that the value I am using for G is not correct, but this value may be impossible to find from Toyota. The extra powder coat thickness may also slightly modify the final spring rate.

I'll see if I can get the correct value for G from Toyota, but this may be difficult. G can be calculated backwards from the load deflection values, but this may vary quite a bit.

More updates to come in the future!

Best

Mark

my 08 petrol 120 has same amount of coil raps left and right with a red dot and aqua dot

[brogers Advanced Member Find all posts View Profile Close brogers]

wow, I'm intrigued, and I appreciate the effort you have gone to with the information in the table.
Can I show my ignorance however, and ask you, when you get a chance please, could you help me understand why this information is important...I'm sure its useful, but I just need some further explanation ...please. I did have some pre 2015 150 Prado coils...but the good Mr Zordo disposed of them for me when we installed Dobinson springs...as I will do soon for my 2016 Prado

[Guest Close Guest]

The info is important as it is a good point of reference.

[Whitey Shockie Maker of the Month Award Find all posts View Profile Close Whitey]

my 08 petrol 120 has same amount of coil raps left and right with a red dot and aqua dot

Hey damo73,

Thanks for checking that! So we now have confirmation that the petrol and diesel 120 use different OEM coils.

Best

Mark

[Whitey Shockie Maker of the Month Award Find all posts View Profile Close Whitey]

wow, I'm intrigued, and I appreciate the effort you have gone to with the information in the table.
Can I show my ignorance however, and ask you, when you get a chance please, could you help me understand why this information is important...I'm sure its useful, but I just need some further explanation ...please. I did have some pre 2015 150 Prado coils...but the good Mr Zordo disposed of them for me when we installed Dobinson springs...as I will do soon for my 2016 Prado

Hi brogers,

The OEM coil database has come from my investigations into understanding the valving/coil rate difference between the IFS in the 120, Hilux, 150 and FJ. The database grew bigger than just those vehicles when I started looking at 80 series rear shock valving and how it relates to OEM and after market 80 series coil spring rates. I’ve also included 200 series coils to see what coil rates are used with its KDSS.

There are many points of interest in knowing the OEM coil rates;

1. In general there are many people looking to know their OEM coil rates, wether that is from a valving standpoint, or a suspension frequency standpoint. There is in general a limited amount of information on OEM coils on the internet, so having our own database here on PP is a good idea for the entire Toyota 4wd community.

2. Interchangeability is also a big interest. For example, Surf drivers use 80 series OEM coils to get more lift. Just recently there was a thread from a 120 driver who asked about temporarily running OEM FJ coils in his front IFS, as this was all he had access to at the time.

3. The rear coils in the Prado are of interest from a few points of view, i) the 120, 150 and FJ all share nearly identical rear suspension geometry, so knowing the OEM rear shock travel and coil bucket separation is important, ii) 80 series rear shocks are in common use in Prado rears, so knowing their valving is important, and their valving is almost always directly related to 220lb/in after market coils, substantially stiffer than OEM 80 series, but very close to Prado OEM coil rates, which is why 80 series rear shocks are so comfortable, they are very well matched to the Prado OEM coils, iii) in general, it is interesting to know the suspension geometry changes from Landcruiser to Prado, eg, higher floorpan/chassis separation in Landcruiser means taller OEM coils etc., and how the coils have changed from 80/100 series to 200 series.

4. Without a doubt the most interesting coils are the relationship between 120, Hilux, 150 and FJ. All of these vehicles use a similar double wishbone geometry, and similar length upper and lower control arms. However, the strut lengths and coil rates are different between all of them. 120/Hilux are close to 600lb/in, while FJ is around 700lb/in, and 150 is 800lb/in. These are dramatic changes in coil rate for the IFS, some of which is related to VSC (absent in 120), and weight changes and distribution. Knowledge of these OEM rates also means you know that you will need much stiffer rebound valving to cope with the higher rates in the 150 and FJ (if you choose to keep close to OEM spec valving/coil rates when purchasing after market suspension). These choices can affect VSC and trigger it in unusual circumstances.

5. There are also differences in the same series, for example, the 120 has different coils for petrol and diesel, see post #4 above.

John at Zordos has been a huge help with being able to make this database, as I potter around his backyard measuring things!

Hope this helps you understand the importance of this type of database.

Best

Mark

[Whitey Shockie Maker of the Month Award Find all posts View Profile Close Whitey]

Hey all,

I have updated the database again today after sanding back some powder coat. The powder coat turned out to be around 95 micron in thickness, not so much, but a reduction of 0.19mm in wire diameter means a reduction of coil rate in the range 8-38lb/in across the entire database.

Here is an interesting link showing deflection measurements with and without powder coat, and you can see that the powder coat can change the result by around 2lb/in. This may be within measurement error of the instrument used. As such, it is quite relevant to sand back the powder coat and get the coil wrap back to bare metal for wire diameter measurements, as the powder coat contributes less than 1% of the coil rate. The powder coat thickness from this example was around 70 micron.

http://powder365.com/forum/viewtopic.php?f=3&t=3005

The largest discrepancy between coil rate by equation and coil rate by deflection testing are the 150 coils. However, as noted above in post #4, the 120 uses different coils for petrol and diesel, and this may also be true for the 150, and I don't know if Dobinsons measured petrol or diesel coils.

More to come!

Best

Mark

[Whitey Shockie Maker of the Month Award Find all posts View Profile Close Whitey]

Hey all,

Another update today which includes the 03-09 petrol 120 coils, where you can see they are a bit softer than the diesel coils, likely due to the extra weight of the 3.0 D4D compared to the 1GR-FE.

Best

Mark

[Peterpilot Avid PP Poster! Find all posts View Profile Close Peterpilot]

Another interesting video, "MEASURING A COIL SPRING - Dobinsons Springs & Suspension"
https://youtu.be/afsHVWGSudE

[Whitey Shockie Maker of the Month Award Find all posts View Profile Close Whitey]

Hey all,

I updated the tables again today after confirming the 2016 2.8 diesel front coils are nearly identical to the pre face lift 150 series front coils.

So the 150 has preserved the high rebound/high coil rate setup on the IFS, at least for the diesel.

Best

Mark

[Whitey Shockie Maker of the Month Award Find all posts View Profile Close Whitey]

Hey all,

Another update today after King Springs have completed load-deflection testing of 12 coils for me, indicated in red in the first table.

The only other load-deflection figure in the first table is for Hilux coils (which I haven't got in my collection yet), at 565lb/in, determined by Dobinsons.

You can see that the load-deflection figures from King Springs are in nice agreement with most rates determined by the coil rate equation.

I had to double check the FJ coils, as I originally had quite high rates above 700lb/in by the coil rate equation. I had assumed the same 95um powder coat thickness I measured on 150 coils, but this was not valid. The powder coat on the FJ coils is over four times as thick, ca. 430um. This highlights the necessity of determining the powder coat thickness for every single coil!

This makes more sense now in terms of kerb weight, and it appears the FJ has kept 120 spec coils, while the 150 Prado uses higher rate coils due to its heavier kerb weight.

I'd like to say a big thank you to Steve at King Springs who enthusiastically and carefully measured 12 different coils for me. The error in measurements by load-deflection would typically be around 10lb/in, so I think that the agreement between the coil rate equation and load-deflection measurements is quite reasonable now.

I'll update again in the future when I get some Hilux coils.

Best

Mark

[drwormy Junior Member Find all posts View Profile Close drwormy]

Awesome work Mark.

Correct knowledge of factory springs (as well as shock valving) is key to understanding and predicting suspension upgrades and performances.

[Guest Close Guest]

Fantastic effort, Whitey and King Springs.