Hey all,
It’s always a bit frustrating to hear suspension sales staff suggest the BE5-A713 shock for the rear of a lifted Prado, so I thought it would be informative for everyone to know why it should not be used.
The first reason is quite simple, the A713 has a very short open length of 580mm (574mm on OEM shock), and will result in minimal droop for the standard 2” lift. With the Prado having IFS, maximising articulation on the rear is crucial for off-road performance. Maximising rear droop is critical. The plot below shows the how the rear shock open length affects your rear droop;
The A713 has closed-open lengths of 368-580mm. As you can see in the plot, for a typical 2” lift, you’ll end up with around 60mm of droop in the rear by using this shock.
The second reason is a little more complex, and is to do with the valving. Historically the predecessor of the BE5-A713 is the BE5-A481. The BE5-A481 was developed by Bilstein Germany for stock non-lifted Prados on soft OEM coils. The A481 was extended by 19mm (as OEM ride heights in Japan can be lower by up to 25mm) and sold in Australia as the A713 with the same valving as the A481. Most OEM Prado rear shocks have lost gas by now, but we can compare the A713 valving with a new OEM rear shock from an FJ Cruiser, shown below;
Toyota has designed a rear OEM shock for FJ/Prado with 1700N:1475N at 0.52m/s, and they have matched this with a 195lb/in coil. Comparing the valving curves of the A713 and the FJ OEM shock shows they are very similar in magnitude and shape. The A713 has moderately stronger valving at low-mid velocity, but at high velocity, for all intensive purposes, the OEM FJ Cruiser shock behaves just like an A713 Bilstein.
There is a higher rebound version of the A713, the 24-238830, 370-587mm with 2800N/1570N, which utilises the same compression stack as the A713. This shock would be suitable for an OEM non-lifted vehicle with a packed up cargo area. Unfortunately this is where the development of rear Bilstein shocks for the Prado stopped. Luckily for us, the problem was sorted much earlier on the 80 series Landcruiser.
When the 80 series Landcruiser came out, Bilstein developed a similar rear shock, which was the B46-1478 (note no S or LT in the part code). This original 1478 shock had valving similar to the A713/A481. This 1478 shock was also made for a Japanese model 80 series Landcruiser which sits 25mm lower than the Oz spec Landcruiser, so it also had a very short open length.
When the Australian model 80 series was released, fortunately for us the original 1478 was deemed to be inappropriate both in length and valving terms. This motivated the development of the B46-1478S.
The plot below compares A713 valving with 1478S valving;
As you can see, the valving for the 1478S for the 80 series rear is substantially different, with compression lowered by around 780N, and rebound increased by around 1560N. The knee in the rebound curve was also designed to inflect underneath 200mm/s to catch the body roll of the 80 Cruiser.
So how does the 1478S valving connect to the Prado?
Everyone is aware that 80 series shocks fit the back of the Prado. The rear solid-axle geometry of the 80 series is also very similar to the Prado. So length wise the 80 series shocks are a great fit for the Prado rear.
On the valving side, I’ll use the example of a heavily loaded Prado. Many of you are aware that once you pack up the rear cargo area of a Prado the vehicle weight can quickly exceed GVM at 2850kg. I’ve seen Prados with 3200-3300kg bridge weight. For a 3200kg Prado, you are going to be running at least a 280lb/in coil in the rear to combat the sag. The calculations to get the valving needed are simple scaling from the OEM valving and coil rates;
Rebound: 280lb/in coil needs (280/195)x(3200/2110) = 3811N
Compression: 280lb/in coil needs (195/280)x(2110/3200) = 712N
So a 3200kg Prado with 280lb/in rear coils will need a rear shock with valving of 3811N/712N.
These scaling calculations are quite simple, and you can do them off vehicle weight, axle weight, sprung weight and unsprung weight. You’ll end up with numbers that are in the range 3800-4800N for rebound, and 560-710N for compression. Up to 5000N rebound will feel very stiff when the Prado is unloaded, and you could easily bounce the rear over speed bumps with that much rebound. 14mm shafts on the 46 series Bilsteins are also at their performance limits around 4000N of Force, you won't normally see more than 4000N of valving with 46mm piston/14mm shaft. Similarly, high compression can feel very twitchy on the road, and you’ll feel every little bump and it can feel like you have leaf springs in the back of your Prado.
The most common solid-axle valving used in US model Toyotas is 255/70, or 2550N/700N, for leaf sprung vehicles. Here in Australia we tend to use more rebound for our heavier vehicles, eg, the Hilux B46-1036LT has 3200N/700N. For coil sprung solid axles, including the front of Jeeps etc., you can see valving range up to 400/100, or 4000N/1000N.
The longest Bilstein for the rear of the 80 series is the B46-1478LT, 380-625mm, with 4000N/900N. The 1478S is shorter and softer with 380-595mm and 3865N/540N. There is also Quadrants commonly used rear shock 24-217897 which is 380-610mm with 3700N/515N.
The rear of the Prado is very similar to the 80 series Landcruiser in terms of geometry and kerb weight (2110kg compared to 2163kg), so it is no surprise that the 80 series valving works well in our Prados.
I have excellent feedback on the use of the 24-217897 and the B46-1478LT in the rear of both Prados and FJ Cruisers. I have received feedback that the 1478LT can feel “stiffish” on-road when the vehicle is unloaded.
I myself have run 80 series shocks with 365-618mm and valving of 3000N/600N, and have run them at 3000kg bridge weight. The rear suspension cycles beautifully with this valving.
My seat of the pants feeling with rear valving suggests a limit of 3500N:800N. Certainly anything over 1000N compression is going to feel bumpy when the 4wd is unloaded. The old 82 series Koni for 80 series Landcruisers is 2300N/1050N, built for OEM configuration. Koni can have quite unusual valving when compared to a Bilstein, and in this case 2300N will be nowhere near enough rebound in a heavily loaded vehicle.
As I mentioned in another thread, I have driven on the A712/A713 combination through the Simpson in a lifted and heavily loaded 120 Prado, and the A713 could never control the 270lb/in Ridepro coil I had at the time, and the rear was very unbalanced and would force significant uncontrolled vehicle pitch which needed to be cycled out. There is simply not enough rebound in the A713 to control a high rate coil or to handle a heavily loaded rear which can run to 1800kg, which means using the brakes to slow the Prado down and kill the uncontrolled pitch, even at a miserly 20km/h.
The A713 should be thought of as useful only for an unloaded non-lifted OEM vehicle on soft OEM springs. The short open length of the A713 also means it is not at all useful in a lifted geometry, and you will end up with only 50-60mm of droop at a 2” lift.
As is usual for the majority of Prado owners who modify their suspension, they lift the vehicle typically at least 2”. If any sales person suggests to you to use a A713 in the rear, my advice is to hang up the phone and find somebody competent. Go for the 24-217897 or the B46-1478LT.
Note that for 120 owners, you can get away with not lengthening your brake lines or swaybar links with the 24-217897, but you’ll need to lengthen both with the 1478LT. FJ and 150 owners should only need to lengthen their swaybar links with the 1478LT as the FJ and 150 come with longer OEM rear brake lines.
Hope you all get your rear shocks sorted and end up with appropriate valving, and make sure to keep the open length longer than 600mm to get some decent droop in the rear.
Best
Mark
It’s always a bit frustrating to hear suspension sales staff suggest the BE5-A713 shock for the rear of a lifted Prado, so I thought it would be informative for everyone to know why it should not be used.
The first reason is quite simple, the A713 has a very short open length of 580mm (574mm on OEM shock), and will result in minimal droop for the standard 2” lift. With the Prado having IFS, maximising articulation on the rear is crucial for off-road performance. Maximising rear droop is critical. The plot below shows the how the rear shock open length affects your rear droop;
The A713 has closed-open lengths of 368-580mm. As you can see in the plot, for a typical 2” lift, you’ll end up with around 60mm of droop in the rear by using this shock.
The second reason is a little more complex, and is to do with the valving. Historically the predecessor of the BE5-A713 is the BE5-A481. The BE5-A481 was developed by Bilstein Germany for stock non-lifted Prados on soft OEM coils. The A481 was extended by 19mm (as OEM ride heights in Japan can be lower by up to 25mm) and sold in Australia as the A713 with the same valving as the A481. Most OEM Prado rear shocks have lost gas by now, but we can compare the A713 valving with a new OEM rear shock from an FJ Cruiser, shown below;
Toyota has designed a rear OEM shock for FJ/Prado with 1700N:1475N at 0.52m/s, and they have matched this with a 195lb/in coil. Comparing the valving curves of the A713 and the FJ OEM shock shows they are very similar in magnitude and shape. The A713 has moderately stronger valving at low-mid velocity, but at high velocity, for all intensive purposes, the OEM FJ Cruiser shock behaves just like an A713 Bilstein.
There is a higher rebound version of the A713, the 24-238830, 370-587mm with 2800N/1570N, which utilises the same compression stack as the A713. This shock would be suitable for an OEM non-lifted vehicle with a packed up cargo area. Unfortunately this is where the development of rear Bilstein shocks for the Prado stopped. Luckily for us, the problem was sorted much earlier on the 80 series Landcruiser.
When the 80 series Landcruiser came out, Bilstein developed a similar rear shock, which was the B46-1478 (note no S or LT in the part code). This original 1478 shock had valving similar to the A713/A481. This 1478 shock was also made for a Japanese model 80 series Landcruiser which sits 25mm lower than the Oz spec Landcruiser, so it also had a very short open length.
When the Australian model 80 series was released, fortunately for us the original 1478 was deemed to be inappropriate both in length and valving terms. This motivated the development of the B46-1478S.
The plot below compares A713 valving with 1478S valving;
As you can see, the valving for the 1478S for the 80 series rear is substantially different, with compression lowered by around 780N, and rebound increased by around 1560N. The knee in the rebound curve was also designed to inflect underneath 200mm/s to catch the body roll of the 80 Cruiser.
So how does the 1478S valving connect to the Prado?
Everyone is aware that 80 series shocks fit the back of the Prado. The rear solid-axle geometry of the 80 series is also very similar to the Prado. So length wise the 80 series shocks are a great fit for the Prado rear.
On the valving side, I’ll use the example of a heavily loaded Prado. Many of you are aware that once you pack up the rear cargo area of a Prado the vehicle weight can quickly exceed GVM at 2850kg. I’ve seen Prados with 3200-3300kg bridge weight. For a 3200kg Prado, you are going to be running at least a 280lb/in coil in the rear to combat the sag. The calculations to get the valving needed are simple scaling from the OEM valving and coil rates;
Rebound: 280lb/in coil needs (280/195)x(3200/2110) = 3811N
Compression: 280lb/in coil needs (195/280)x(2110/3200) = 712N
So a 3200kg Prado with 280lb/in rear coils will need a rear shock with valving of 3811N/712N.
These scaling calculations are quite simple, and you can do them off vehicle weight, axle weight, sprung weight and unsprung weight. You’ll end up with numbers that are in the range 3800-4800N for rebound, and 560-710N for compression. Up to 5000N rebound will feel very stiff when the Prado is unloaded, and you could easily bounce the rear over speed bumps with that much rebound. 14mm shafts on the 46 series Bilsteins are also at their performance limits around 4000N of Force, you won't normally see more than 4000N of valving with 46mm piston/14mm shaft. Similarly, high compression can feel very twitchy on the road, and you’ll feel every little bump and it can feel like you have leaf springs in the back of your Prado.
The most common solid-axle valving used in US model Toyotas is 255/70, or 2550N/700N, for leaf sprung vehicles. Here in Australia we tend to use more rebound for our heavier vehicles, eg, the Hilux B46-1036LT has 3200N/700N. For coil sprung solid axles, including the front of Jeeps etc., you can see valving range up to 400/100, or 4000N/1000N.
The longest Bilstein for the rear of the 80 series is the B46-1478LT, 380-625mm, with 4000N/900N. The 1478S is shorter and softer with 380-595mm and 3865N/540N. There is also Quadrants commonly used rear shock 24-217897 which is 380-610mm with 3700N/515N.
The rear of the Prado is very similar to the 80 series Landcruiser in terms of geometry and kerb weight (2110kg compared to 2163kg), so it is no surprise that the 80 series valving works well in our Prados.
I have excellent feedback on the use of the 24-217897 and the B46-1478LT in the rear of both Prados and FJ Cruisers. I have received feedback that the 1478LT can feel “stiffish” on-road when the vehicle is unloaded.
I myself have run 80 series shocks with 365-618mm and valving of 3000N/600N, and have run them at 3000kg bridge weight. The rear suspension cycles beautifully with this valving.
My seat of the pants feeling with rear valving suggests a limit of 3500N:800N. Certainly anything over 1000N compression is going to feel bumpy when the 4wd is unloaded. The old 82 series Koni for 80 series Landcruisers is 2300N/1050N, built for OEM configuration. Koni can have quite unusual valving when compared to a Bilstein, and in this case 2300N will be nowhere near enough rebound in a heavily loaded vehicle.
As I mentioned in another thread, I have driven on the A712/A713 combination through the Simpson in a lifted and heavily loaded 120 Prado, and the A713 could never control the 270lb/in Ridepro coil I had at the time, and the rear was very unbalanced and would force significant uncontrolled vehicle pitch which needed to be cycled out. There is simply not enough rebound in the A713 to control a high rate coil or to handle a heavily loaded rear which can run to 1800kg, which means using the brakes to slow the Prado down and kill the uncontrolled pitch, even at a miserly 20km/h.
The A713 should be thought of as useful only for an unloaded non-lifted OEM vehicle on soft OEM springs. The short open length of the A713 also means it is not at all useful in a lifted geometry, and you will end up with only 50-60mm of droop at a 2” lift.
As is usual for the majority of Prado owners who modify their suspension, they lift the vehicle typically at least 2”. If any sales person suggests to you to use a A713 in the rear, my advice is to hang up the phone and find somebody competent. Go for the 24-217897 or the B46-1478LT.
Note that for 120 owners, you can get away with not lengthening your brake lines or swaybar links with the 24-217897, but you’ll need to lengthen both with the 1478LT. FJ and 150 owners should only need to lengthen their swaybar links with the 1478LT as the FJ and 150 come with longer OEM rear brake lines.
Hope you all get your rear shocks sorted and end up with appropriate valving, and make sure to keep the open length longer than 600mm to get some decent droop in the rear.
Best
Mark
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