Can you get coil bind/solid coil on the 120 Prado IFS?

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

Good stuff as ever Mark.

While your on it - how about a word on the rear? Without thinking about it id image its less likely for coil bind in the rear than front.

Hey,

Just checked all the numbers for the rear, data is below;



Bumpstop contact on the outboard chassis bumpstops is 405mm on the 120 series. The coil bucket separation is 193mm at bumpstop contact. The bumpstop is ca. 50mm thick, so 100% bumpstop compression occurs at a shock length of 365mm, or 145mm coil bucket separation.

You can see again that Toyota has engineered 100% bumpstop compression into the OEM closed length with around a 5mm safety margin for shock bush stretch. The OEM closed length is 359mm for the 120, and 363mm for the 150.

The solid height of the OEM coils is less than 100mm for the 120 and 150, so there is no possibility of binding the OEM coils to solid height.

However, after market coils are a different story.

The solid heights for C59-327 and C59-487 are 160mm and 155mm respectively. The solid heights of after market coils are always longer due to thicker wire diameter and more coil winds. The longest at 160mm occurs at around 370mm closed length, or ca. 70% bumpstop compression. As such, if you run a short closed length rear shock less than 370mm (there are several) with the popular 327 coil, then there is definitely a chance you could get solid coil bind on a very big hit on the rear. You would need the Prado flying to do this.

A more likely scenario for the rear is that you could bump out your shocks (with closed length longer than 370mm, of which there are many) before you get solid coil bind.

As is very typical for solid axle setups, bumpstop spacing becomes critical for the rear.

Many (not all) after market shock manufacturers will tell you that you must allow for 100% compression of the bumpstops to protect the closed length of your shock. For example, a 380mm closed length only allows for 50% compression of the outboard chassis bumpstops. To allow for 100%, the bumpstops should be spaced down to 380 + 50 = 430mm, which is 25mm longer than the OEM contact at 405mm. Ie, space your bumpstops by 25mm for 380mm rear closed length.

You can (and many do) choose to ignore the necessary spacing of bumpstops, and hope that you never get a big hit on the rear.

Many have bumped out rear shocks from accidental big hits. Conversely, many go rock crawling and bump their shocks out at slow speed repetitively and never damage them.

Take it easy and watch out for the big hits!

Best

Mark

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

Here's some pics of the arms and inner guard from the wheel arch side.

You can see an impression of the arm on the inner guard. The arm may well be a bit bent. The adjustor is maxed out to get reasonable castor and the other side adjusted to match is no where near maxed out.

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

Hey Ben,

With the angle that the upper arm sits at, do you believe it's possible for the arm to hit where you've circled it in the lower photo? ...edit, I just looked at my old arms, and that definitely looks like the highest part of the arm!

Regarding the caster, its typical for many aligners to run a degree of split, highest on PS, to allow for our crowned roads. As such it's common to see one cam maxed out on the high caster side.

Sounds like you could do with some after market arms, what is your front ride height?

Best

Mark

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

Wow. I didn't think that was possible!

Wouldn't the bumpstop prevent this happening? There's not a lot of room - maybe the body bounced down on the body mounts while the suspension was on the bumpstop?

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

Wow. I didn't think that was possible!

Wouldn't the bumpstop prevent this happening? There's not a lot of room - maybe the body bounced down on the body mounts while the suspension was on the bumpstop?

Hey!

It's definitely a body going down, suspension fully flexing on bushes travelling up situation!

...it would be much harder to do in lifted geometry I think, he was at 750mm ride height when it happened. Same for the 05 that hit a beach washout, factory ride height or less.

Best

Mark

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

Hey Ben,

With the angle that the upper arm sits at, do you believe it's possible for the arm to hit where you've circled it in the lower photo? ...edit, I just looked at my old arms, and that definitely looks like the highest part of the arm!

Regarding the caster, its typical for many aligners to run a degree of split, highest on PS, to allow for our crowned roads. As such it's common to see one cam maxed out on the high caster side.

Sounds like you could do with some after market arms, what is your front ride height?

Best

Mark

Yeah, I was VERY surprised too but I would say its a combination of the body compressing on the mounts and the arms coming up, it was on a steep downhill section to so the majority of the vehicles weight, full loaded with 5 adults would be over the front arms.

There is a <edit> 10' caster split to account for the road crowning etc. . They way we did it though was set the PS side to max as that was the limiting one, then set the DR accordingly.

I am currently a tad under 800mm rim to guard at the front, it may have settled a little since it was installed, perhaps 790mm buy the time I add my compressor up front and a few other things. I have plenty of droop at the moment so was tossing up the Dobinsons springs up front to go a bit more. will see how it settles after I add all the accessories up front and a few more trips.

Aftermarket arms were a consideration, at the moment at full droop, the arm JUST clears the springs (springs have to be in a particular orientation so the arm goes in between coils). If I was just after castor correction I would just use Superpro bushes, given I want a bit more height - aftermarket arms may be the go even if its just for more arm to spring clearance at full droop.

It drives pretty well for only having ~1.5deg caster

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

Hey!

It's definitely a body going down, suspension fully flexing on bushes travelling up situation!

...it would be much harder to do in lifted geometry I think, he was at 750mm ride height when it happened. Same for the 05 that hit a beach washout, factory ride height or less.

Best

Mark

Yes, it was 750mm height. Thats with ARB Steel bar, Warn winch, spotties and dual batt up front. The 150strut/spring has enough spring rate to give you stock ride height but obviously the travel is or less stock. I actually really liked it for a stock height touring combo. Stiffer coil rate made it handle much better, after going to Kings and Billys it handled similar to stock with the body roll and front pitch under cornering. I'll live with the current setup untill I finalise all the accessories up front then reevaluate what coil I want.

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

Yeah, I was VERY surprised too but I would say its a combination of the body compressing on the mounts and the arms coming up, it was on a steep downhill section to so the majority of the vehicles weight, full loaded with 5 adults would be over the front arms.

There is a 30' caster split to account for the road crowning etc. . They way we did it though was set the PS side to max as that was the limiting one, then set the DR accordingly.

I am currently a tad under 800mm rim to guard at the front, it may have settled a little since it was installed, perhaps 790mm buy the time I add my compressor up front and a few other things. I have plenty of droop at the moment so was tossing up the Dobinsons springs up front to go a bit more. will see how it settles after I add all the accessories up front and a few more trips.

Aftermarket arms were a consideration, at the moment at full droop, the arm JUST clears the springs (springs have to be in a particular orientation so the arm goes in between coils). If I was just after castor correction I would just use Superpro bushes, given I want a bit more height - aftermarket arms may be the go even if its just for more arm to spring clearance at full droop.

It drives pretty well for only having ~1.5deg caster

Hey,

I had 1.5deg/0.5deg caster, and it drove like a pig, was very twitchy at high speed. I put in after market arms, currently at 2.5deg and handles heaps better.

Sounds like you have a lot of droop if you're sneaking in between coil windings. I had a similar setup on mine, and rotated the coils, my struts are at 577mm open.

I know someone who is using the offset Superpro bushes in their lower arms, they haven't been around for very long though!

After inspecting my OEM ball joint, I can see small tears on both sides. The OEM ball joint binds up at 575mm open length, so this is enough to stretch the OEM boot to tearing point. Some folks are running out to 585mm on the IFS now, so after market arms become critical to avoid binding the ball joint.

What length struts are you running, and what is your droop?

Best

Mark

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

Hey,

I had 1.5deg/0.5deg caster, and it drove like a pig, was very twitchy at high speed. I put in after market arms, currently at 2.5deg and handles heaps better.

Sounds like you have a lot of droop if you're sneaking in between coil windings. I had a similar setup on mine, and rotated the coils, my struts are at 577mm open.

I know someone who is using the offset Superpro bushes in their lower arms, they haven't been around for very long though!

After inspecting my OEM ball joint, I can see small tears on both sides. The OEM ball joint binds up at 575mm open length, so this is enough to stretch the OEM boot to tearing point. Some folks are running out to 585mm on the IFS now, so after market arms become critical to avoid binding the ball joint.

What length struts are you running, and what is your droop?

Best

Mark

I think your twitchiness was possibly the castor split. I just checked my alignment sheet and I had 1.68deg / 1.47deg (L/R) which is a 13' split. before was a typo shouldn't be 30', it should be 10'

I wouldn't want to go any less castor than that, it still had reasonable return to center and tracks nicely on the highway.

Droop is 890mm/880mm
I have safely 80mm droop so was thinking to go to Dobinsons C59-354 which should give me around 820mm ride height with 65mm droop. I also prefer the onroad handling of the stiffer spring rate but for the expense I'd rather get my onboard air sorted... Plus with that additional lift I'd have to get aftermarket arms too. Only other consideration is that the spring will have an additional preload force on the strut at full extension (using stock 150 setup as reference, it is 95Kg more)

Strut open length: 573mm (just inside the OEM ball joint bind )

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

Wow. I didn't think that was possible!

Wouldn't the bumpstop prevent this happening? There's not a lot of room - maybe the body bounced down on the body mounts while the suspension was on the bumpstop?

Hey,

I just found some old clearance measurements I made, with the lower arm jacked into the bumpstop (strut/coil out measurements), I get ca. 45mm gap between the highest point on the upper arm and the guard.

That's a huge gap to close up!

Best

Mark

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

wow, yeah that is a very big gap! The body does move around a fair bit tho, you can see that on the ARB bar so say 20mm of upward movement of the arm and similar downward of the body?

I noticed the worn patch on the arms is significantly bigger than the tip of the bump stop which says to me the stop must compress a fair bit underload to get that large contact patch.

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

wow, yeah that is a very big gap! The body does move around a fair bit tho, you can see that on the ARB bar so say 20mm of upward movement of the arm and similar downward of the body?

I noticed the worn patch on the arms is significantly bigger than the tip of the bump stop which says to me the stop must compress a fair bit underload to get that large contact patch.

Hey,

It would definitely be split both ways. The bumpstop is 25mm thick, and it can compress a lot!

Best

Mark

[trevordd Lurker Find all posts View Profile Close trevordd]

Thanks for the information here! Have you ever tried making some custom springs for your car? I have found a company at http://www.sterling-springs.co.uk/ It seems like they are making different springs for different needs. Maybe I will try them out soon