In your opinion, which kit would provide the smoothest ride?

[6172crew]

If you want smooth, get some TRD PRO take offs from someone on here.

Another forum member added TRD Pro setup to his trail and said it rode stiffer than the stock trail suspension, his also has KDSS which can be stiffer than the non-kdss because the sway bars can feel a little stiffer than ones without the beefy setup.

 

[SoFloT4Run]

I put 5100's all around ... set the fronts @ .85 which leveled the car. The 5100's firmed up the ride a little, which I wanted, and reduced the dive a little, they have been perfect (for me) for >6 years.

You asked for "smooth". That is way too subjective a term. Like "rough", it is just impossible to quantify - as you can see, you'll get a wide variety of opinions. Don't forget, your tires have some effect too.

I like the 5100's but for some reason I am scared of a c-ring failure. Its crazy how the weight of the truck is being held by those flimsy rings.

 

[Jetboy]

The clip rings on the 5100 are strong if they are installed correctly (meaning not putting the perch on upside down). Just a back of the envelope calculation here (there are a few competing formulas I've found, so I'll go with the more conservative one I found).

The conservative formula would basically be area of interface between the circlip and groove seat multiplied by the yield strength of the shock body material. Assuming it's 6061-T6 and has a 42,000psi yield strength and a roughly 0.5 square inch surface area (I guessed roughly 1mm depth groove), the yield strength would be roughly 21,000lbs, and if you use a safety factor of 4, you'd still have a 5000lb working load limit. In a coilover the spring force will not include the shock load absorbing forces that will transfer directly through the shock eyes (which are often much higher than the spring force). With a 600lb/in spring - it would be pretty unlikely to exceed the safe working load of 5000lbs. I'd guess you would compress the spring to the bump stop long before you'd reach 5000lbs of force on the circlip.

So... just quicky calculation suggests that the circlips should be plenty strong for that application.



In the end though - a simple spacer may do everything you're looking for. Just keep it reasonable. If the shock body bottoms out in length before the bump stops stop motion, you can break the shock body and have a mess on your hands. The OEM shocks are small and inexpensive, but they're okay for most people for most uses. Don't be afraid of the 5100's use of circlips. It would be way better to have threads for adjustability reasons, but it's a fine design from a safety perspective. If bilstein would thread the bodies on the 5100 and 6112, they would probably sell a bunch of them to people like me who bought Fox for the adjustability moreso than really needing a high end dampener. I can't imagine that it would add more than $10-20 per shock in manufacturing costs on the scale they build them.


Something else to consider is how often you have to rebuild the higher end shocks. Typically every 2-3 years you'll need to replace the shock spherical bushings. So that means removing them and either having a shop do it, or doing it yourself. Depending on a lot of factors like weather and use, this can be easy or hard. I had to literally cut mine out with a cutoff disk the last time on the lower bolts because they were seized together. It cost me a few bucks for new hardware, but in a shop - it would be a few hundred for the extra labor. The bushings themselves are roughly $20ea and there's 4 of them in front and 2 in the rear. So... $120ish minimum in parts, plus half a day of labor every 2-3 years is part of the cost of owning them. In my experience the internal rebuilds are not necessary very often under normal use. Maybe every 10 years if something leaks. Or every 1000 miles of race duty. Just depends on use, but for daily driver it's not a frequent problem. Shocks like the 5100 or OEM are probably more like 100k miles and then throw them away. They're much lower maintenance and expense over time.

 

[philsey]

I like the 5100's but for some reason I am scared of a c-ring failure. Its crazy how the weight of the truck is being held by those flimsy rings.

Not to worry. What [MENTION=118321]Jetboy[/MENTION] is trying to say is hundreds upon hundreds of 4Runners are using these without issue. I've never read of a failure.

 

[SoFloT4Run]

The clip rings on the 5100 are strong if they are installed correctly (meaning not putting the perch on upside down). Just a back of the envelope calculation here (there are a few competing formulas I've found, so I'll go with the more conservative one I found).

The conservative formula would basically be area of interface between the circlip and groove seat multiplied by the yield strength of the shock body material. Assuming it's 6061-T6 and has a 42,000psi yield strength and a roughly 0.5 square inch surface area (I guessed roughly 1mm depth groove), the yield strength would be roughly 21,000lbs, and if you use a safety factor of 4, you'd still have a 5000lb working load limit. In a coilover the spring force will not include the shock load absorbing forces that will transfer directly through the shock eyes (which are often much higher than the spring force). With a 600lb/in spring - it would be pretty unlikely to exceed the safe working load of 5000lbs. I'd guess you would compress the spring to the bump stop long before you'd reach 5000lbs of force on the circlip.

So... just quicky calculation suggests that the circlips should be plenty strong for that application.



In the end though - a simple spacer may do everything you're looking for. Just keep it reasonable. If the shock body bottoms out in length before the bump stops stop motion, you can break the shock body and have a mess on your hands. The OEM shocks are small and inexpensive, but they're okay for most people for most uses. Don't be afraid of the 5100's use of circlips. It would be way better to have threads for adjustability reasons, but it's a fine design from a safety perspective. If bilstein would thread the bodies on the 5100 and 6112, they would probably sell a bunch of them to people like me who bought Fox for the adjustability moreso than really needing a high end dampener. I can't imagine that it would add more than $10-20 per shock in manufacturing costs on the scale they build them.


Something else to consider is how often you have to rebuild the higher end shocks. Typically every 2-3 years you'll need to replace the shock spherical bushings. So that means removing them and either having a shop do it, or doing it yourself. Depending on a lot of factors like weather and use, this can be easy or hard. I had to literally cut mine out with a cutoff disk the last time on the lower bolts because they were seized together. It cost me a few bucks for new hardware, but in a shop - it would be a few hundred for the extra labor. The bushings themselves are roughly $20ea and there's 4 of them in front and 2 in the rear. So... $120ish minimum in parts, plus half a day of labor every 2-3 years is part of the cost of owning them. In my experience the internal rebuilds are not necessary very often under normal use. Maybe every 10 years if something leaks. Or every 1000 miles of race duty. Just depends on use, but for daily driver it's not a frequent problem. Shocks like the 5100 or OEM are probably more like 100k miles and then throw them away. They're much lower maintenance and expense over time.

Wow! Thanks for that explanation!