Bilstein Gas Shockies have bit the dust!!

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

Hey everyone,

I got about 47,000km out of my 712/713's, cross country Brissy to Perth and back with work, Simpson crossing both ways, lots and lots of beach work in WA and QLD. My front struts are completely stuffed after regular topping out and my internal bump stops have failed letting the washer seat slide back into the strut body.

See this thread for a detailed discussion of my problems...

http://www.pradopoint.com/showthread...-Prado-120-IFS

I will never use Bilsteins again, they are valved far too softly, their design is ancient technology, and their long closed lengths are very problematic in the Prado IFS.

I hear good things about Lovells from both users (as mentioned above) and from blokes who sell suspension for a living. Even though I have reservations about them being rebadged Driveline Services shocks that are made in China, Lovells open and closed lengths are spot on for the Prado. If German engineered monotube Bilsteins can fail like mine have, then any shock can.

My 20 cents worth!

Best

Mark

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

Hey everyone,

I got about 47,000km out of my 712/713's, cross country Brissy to Perth and back with work, Simpson crossing both ways, lots and lots of beach work in WA and QLD. My front struts are completely stuffed after regular topping out and my internal bump stops have failed letting the washer seat slide back into the strut body.

See this thread for a detailed discussion of my problems...

http://www.pradopoint.com/showthread...-Prado-120-IFS

I will never use Bilsteins again, they are valved far too softly, their design is ancient technology, and their long closed lengths are very problematic in the Prado IFS.

I hear good things about Lovells from both users (as mentioned above) and from blokes who sell suspension for a living. Even though I have reservations about them being rebadged Driveline Services shocks that are made in China, Lovells open and closed lengths are spot on for the Prado. If German engineered monotube Bilsteins can fail like mine have, then any shock can.

My 20 cents worth!

Best

Mark

Topping out as in fully opened length, or bottoming out as in fully closed length?
A712's only run a topout bump stop internally, they use the OE bump stops on the vehicle for compression.
I have seen hundreds of Bilstein & every other brand destroyed from Topping out, but have not seen any bottom out failures in the Bilsteins.



Kind Regards, Jason.

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

Hey Jason,

My 712's have topped out (open length) a lot, on roundabouts/speedbumps etc. They did it since install, and still do it today. My lift started at 2", and has sagged to 1" over 4 years, droop went from 50mm to 75mm today. If you include the 8mm shroud cylinder on top of the strut, that means my 712 struts are topping out at an effective open length of 553+8 = 561mm. They do this with 75mm of droop.

I wasn't aware that the 712 monotube didn't run an internal bump stop. I thought nearly all monotubes run internal bump stops?

If this isn't the case for the 712, then I don't understand how the washer seat flange can now slide inside the strut body on my 712. My first thought was that the internal bump stop had failed.

So the closed length has now decreased on my 712, can you offer an alternative explanation for how this has occurred if it isn't internal bump stop failure?

Best from the Bris

Mark

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

Without stripping the shock for inspection, i cannot tell you why that failure has occured. I wouldn't even like to take a guess.
Are you measuring droop from the new lower ride height?, which will give a different figure than what it would have sitting 1" higher when 1st installed.
If you have had a lot of topping out all it's life you could have pancaked the top out bump stops which could explain it.
There are a lot of shocks that do not run bottom out bump stops or even top out bump stops internally. A lot of telescopic rear shocks might just run an external compression bump stop up over the shock shaft.
You will find that a lot of manufacturers will only use them where needed. ie: the vehicle has nothing built in to stop the travel before the shock bottoms out or tops out.
As for the design of the Monotube A712 being old, almost all shocks from everyone, barring high end exotic race style shocks are based on a 70-80+ year old design that has been refined through development over time. There really are only 2 basic configurations of telescopic shock available on run of the mill vehicles, with either a twin tube or monotube design. the biggest differences are in the bore sizing, valving systems used internally & the quality and sizing of the internal components used.
The A712's & A713's like all Aus spec Bilsteins are specifically valved by Bilstein Aus in-house.
They do the R&D here for valving at the start of a new part number run, then send the finished specs back to Germany & they valve them to Aus specs specifically.


Regards, Jason.

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

Hey Jason,

Thanks for all of that excellent info.

My 75mm droop is from the lower ride height.

When I measured the open length of my 712 strut (just a few days ago), it was bang on 553mm, as recorded in the suspension database. As such, I don't think the top-out bump stop has failed/pancaked, as if it had, the open length would be longer than 553mm.

The problem is at the other end of the strut. The washer seat can slide inside the strut body when you push the shaft in. That shouldn't happen, and indicates something has failed at the bottom end of the strut.

Without cutting open my 712, I have no idea what has failed. As soon as my new suspension goes in, I will be cutting my 712's open with a dremel and will find out what has failed.

This indicates that there is a problem with the 712 closed length = 427 + 8 (shroud) = 435mm. Something is bumping out at this strut length and breaking something in the bottom end of the strut.

There are many struts available with closed lengths around 435mm, and they are even longer closed when you add in a shroud cylinder below the washer seat. These might be ok in 150's which have longer OEM closed length of 432mm, but in 120's they can obviously be problematic.

The factory OEM closed length on a 120 Prado is 420mm, and it's clear it has been engineered that way so that solid coil bind and full lower control arm bump stop compression occurs before strut bottom out can.

This is the principal reason I won't use Bilsteins on my 120 again, as the closed length is too long.

Best

Mark

[Rusty62 Advanced Member Find all posts View Profile Close Rusty62]

This topic re Billie failures has come up before. I'm on my second set, the first ones replaced after 150000 km and only replaced because we were going on a long trip. I still have the old ones as spares.
Before anyone says I do a lot of bitumen, a lot of it is on second class potholed back roads around south east queensland, plus the odd run up the cape and one to Tassie.
What I found to increase life of the fronts is no to have more than 45 mm of lift and run standard raised springs. The harder the spring ( as I had on my first 120 ) would make it hard for the shock to control the rebound. A interesting feature of running the front softer and under the traditional 50 mm lift is the car has less understeer, particularly in the wet. The softer spring allows the car to lean a bit in corners and this allows the rear to lean as well, the result is slight angle change of the rear axle and a minute amount of toe out, thus reduction of the understeer. This became apparent when I did the second car, same tyres same pressures but different spring rate and height but the same Billie shocks.

Rusty.

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

Hey Rusty,

That is some impressive km's you got from your first set of Bilsteins. Were these 712/713?

Interesting point about the understeer. What coils are you using, spring rate and free height?

Best

Mark

[Rusty62 Advanced Member Find all posts View Profile Close Rusty62]

Mark.
Standard bilsteins and kings standard raised coils.
Also use this set up on brothers 150 with same result. Also have airbag man inside the rear coils for that bit extra load carrying when needed. Empty around town run 3-5 psi.

Rusty.

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

Hey Jason,

Thanks for all of that excellent info.

My 75mm droop is from the lower ride height.

When I measured the open length of my 712 strut (just a few days ago), it was bang on 553mm, as recorded in the suspension database. As such, I don't think the top-out bump stop has failed/pancaked, as if it had, the open length would be longer than 553mm.

The problem is at the other end of the strut. The washer seat can slide inside the strut body when you push the shaft in. That shouldn't happen, and indicates something has failed at the bottom end of the strut.

Without cutting open my 712, I have no idea what has failed. As soon as my new suspension goes in, I will be cutting my 712's open with a dremel and will find out what has failed.

This indicates that there is a problem with the 712 closed length = 427 + 8 (shroud) = 435mm. Something is bumping out at this strut length and breaking something in the bottom end of the strut.

There are many struts available with closed lengths around 435mm, and they are even longer closed when you add in a shroud cylinder below the washer seat. These might be ok in 150's which have longer OEM closed length of 432mm, but in 120's they can obviously be problematic.

The factory OEM closed length on a 120 Prado is 420mm, and it's clear it has been engineered that way so that solid coil bind and full lower control arm bump stop compression occurs before strut bottom out can.

This is the principal reason I won't use Bilsteins on my 120 again, as the closed length is too long.

Best

Mark

You won't need to cut it open, they are fully serviceable & rebuildable. You should be able to disassemble it.
I have never seen a Bilstein on a Prado front fail due to bottoming out.
There is more to them internally than meets the eye. They have a floating piston that is nitrogen charged underneath.
(I'll attach a cutaway pic for reference)
To physically bottom them out would require it to be out of the vehicle, and to compress the shock enough to also bottom out the lower nitrogen filled section.
When in the vehicle, they won't contact the lower piston.
They will become coil bound & bump stop bound before any damage could occur in car.
If yours has lost gas, the floating piston could have sunken further down the bore than normal, which will let it compress further by hand when out of the vehicle.
If it were the case that the A712's & in that case most other aftermarket front struts were too long compressed at their stated closed lengths, they would be showing similar repeated failures within weeks of fitment from bottoming out which just isn't the case.
A bottoming shock will usually badly damage or destroy the internal foot valve within a couple of hits & clear signs of a problem will be evident almost immediately.

Kind Regards, Jason.

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

Hey Jason,

Excellent points that you raise!

The internal nitrogen gas pressure is not that high inside the strut, 200-300psi, and I can push the shaft on my strut in by hand out of the car (with great effort), which suggests I still have a lot of gas pressure in the strut. When the strut is in the vehicle, there is enough force from the factory weight of the car alone to push the piston through the gas, by several factors. This means the strut can be bumped out on full bump travel in the vehicle, depending on the suspension geometry.

I agree with you that solid coil bind and bump stop bind will occur, and you can see measurements for my 120 in the plots below;





Take note that the real danger zone for strut length is 440mm, where you are at -25mm compression on the bump stop. On the OEM bump stop, this would be a very big hit (wheels/car in the air), either that or the bump stop has failed for whatever reason, fallen off/rock strike etc.

Also note that depending on your coil free length/number of turns/coil diameter, you will very likely be close to solid coil bind at around -25mm.

For the Prado 120 series, the real danger is in having all of these factors occurring close together, strut length 440mm, -25mm bump stop compression, solid coil bind.

This thread from the FJ (identical IFS to Prado 120) forum highlights this problem;

http://www.fjcc.com.au/f36/superbump...-details-1413/

An extended travel bilstein was used with an after market bump stop. The closed length of this strut is most likely 433+8 (shroud) = 441mm, and it is no surprise that the complete compression of the after market bump stop allowed the struts to fully bump out and kill the struts.

It is stated in the thread that FJ's with identical struts using OEM bump stops were ok.

The real issue that isn't discussed here is suspension geometry safety margins.

If you run a closed length around 440mm in a Prado 120, you have taken away 20mm of bump travel on your strut compared to the OEM strut at 420mm. If your OEM bump stop mechanically fails/falls off, you will bump out a 440mm strut and break it. If you have a 420mm strut, you strut will be ok.

Keep in mind that you are going to have to bend a lower control arm metal on metal compared to bending a piston shaft. The piston shaft will always bend first.

If this happens to you in the bush/remote area, you are stuck, and you will not be able to drive your Prado. However, if you are running 420mm closed length struts, your struts will be ok and you can still drive the car slowly and get out of trouble, patch in an emergency bump stop etc.

Now this is obviously a different story for 150 series drivers, as the OEM closed length on the 150 is 432mm. This means your bump safety margins are already built in, and you can happily run 440mm closed length struts without fear of ever bumping them out.

Back to the other end of the 712 strut, where I have experienced topping out since day 1 of installation.

This plot easily explains why;



Here you can easily see why it is not a good idea to run 712 struts in lifted Prados. If you lift 2" on this strut, you will have minimal 50mm droop on the IFS, which on the taller lifted coils means topping out will occur.

This situation has not improved for me, and my 712's still top out at 75mm droop today after the front end has sagged 0.85".

If you want to use 712/713 struts/shocks, then my suggestion is to use them as a handling upgrade as OEM shock replacements, and keep the OEM coils. If you lift, you will top out due to the short open length of 553mm on the 712, and it will not last as long.

After my own experience of driving cross country twice in a lifted 120 with 712/713's, my personal opinion about Bilsteins is polarised.

In some ways, they are brilliant, eg., I drove the great central road (1100km of corrugations) in one hit in a 15 hour drive, and the Bilsteins just kept on going, minimal fade in a heavily loaded vehicle near GVM.

In other ways they are poor, eg., the valving is too soft to cycle out vehicle pitch at 20-30km/h, which can turn the Prado into a boat.

In suspension geometry terms, they are in my opinion not appropriate for use in lifted Prados due to their minimal suspension travel, short open length leading to top outs, and elimination of bump safety margins.

All of that being so, I would happily run a new monotube Bilstein strut if it was 420-570mm, the correct lengths for the Prado 120. New model struts only seem to be targeted towards 150 series and Hiluxes with their longer closed lengths of >433mm.

Best

Mark

[gxl_d4d Advanced Member Find all posts View Profile Close gxl_d4d]

The strut being hard to move by hand is because of the valving, not the gas.

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

Hey gxl_d4d,

Good point to know!

Best

Mark