Fitting longer rear shocks on 3rd Gen. Tacoma

This thread is a compilation of information from a previous thread discussing installing a 1.5" block under stock leaf springs and still running 3rd Gen Offroad model shocks or swapping to standard length Bilstein 5100 rear shocks. Both are approximately the same lengths, 14.02" compressed and 22.94" extended, making for about 9" total travel space.

The gist is this, lifting the rear enables longer length, rear shocks to be installed. However, longer shocks effectively move the rear ride height down in the total travel range, making more uptravel range possible, but it is limited when the shock body has to get longer, and hence, a longer bump stop. A stock OR leaf spring and OR rear shock and OR bump stop, allow about 3.5" of uptravel,.leaving about 5.5" for downtravel at the shock.

To utilize this 5.5" of downtravel, the leaf spring needs to be able to extend to 22.94" and beyond.
One of the biggest assumptions without actual measuring of rear droop from jackstands, is that stock leafs cannot droop to 23" in stock configuration (no lift). When I measured my stock leafs plus 1/2" block P.S. and 1" block D.S., droop compared to fully extended 5100s, the leafs drooped 1-1.5" below the 5100 shocks at full extension.


This led me to realize 2 things: 1. I have an 1-1.5" unused travel range without lifting, and 2. The stock bump stop length of 2.5-2
6" prevents some potential uptravel.

I then bought Fox 2.0 performance reservoir shocks, which have a compressed length of 15.2" and extended length of 24.8", which were sized for 3-5" lift regardless, and bought what became about 3" hard rubber bump stops with 3/8" steel flip bracket. After experimenting with different block sizes under stock leafs to get tire tuck and maximum travel usage, I bought General Springs HD 1.5" lift leaf springs to lift the rear up as this was all I needed to minimally use all available shock travel.





The limitations of space between the stock upper and lower shock mounts, regardless of lift, and the construction limitations of making longer shocks (longer bodies to house longer shafts, meaning longer compressed lengths, requiring longer bump stops to prevent overcompression) means an effective shock travel range of 9" low end, and 11" at top end.

A 6" longer shock may make 2" more total travel at best. Most shock manufacturers are happy to squeeze out 1.5" more total travel for the space.

Therfore with a longer compressed length, requiring longer bump stops, the uptravel increase is limited with longer shocks while the downtravel is extended. The ride height within that range, due to lift, is what changes.

PREVIOUS THREAD:
With a 1.5" block inserted between the leaf spring and axle, the upper shock mount is roughly 1.5" higher and further apart from the lower shock mount on the axle. If you wish to make this gap back up to maintain the same amount of downtravel as the stock situation was (assuming leafs can droop down as far as shocks can extend) the replacement shock would have to be 1.5" longer.

Herein lies the difficulty finding a match: Stock OR rear shocks and Bilstein 5100 are the about same 23" extended length. A 24.5" extended length shock is going to increase compressed length from 14" stock OR/Bilstein 5100, to around 15". This is because a longer shock body is needed for the longer shaft, all of which ia housed between the upper and lower shock mount locations. Not only has no absolute space really changed (1.5" longer but lose 1" compressed length), you'll also need slightly longer bump stops that can stop the frame's downward motion prior to the new longer shock shaft compressing on itself.

Most people get a slightly longer shock between 23-24" that keeps the compressed length close to 14". The additional lift then goes toward uptravel. If for example, you were to add the long 5100 Bilsteins at 16.3" compressed length, you would need about a 4" or so bump stop instead of the approx 2.5" stock bump stops. In that case, your bumps are close to always engaged by being so close to the frame, especially at only 1.5" lift.

Rear lifting does increase shock size that can be fit into the stock mounts, but it is far from 1:1.

Using the stock mount locations in the rear works similar to the front IFS in that the range is pretty much fixed at around 10" total travel. The difference is where the ride height (lift) is set, and the resulting division of travel range between up and down.

Bilstein 5100s are good and will work fine with 1.5" block or even more. The total travel range (22.94-14.02=8.92) is basically the same as the stock offroad shock. Other than being stronger, what changes is the ride height point within the shock travel range and the division of up travel, limited by the bump, and down travel, limited by the shock extended length (so long as the leafs droop to match).
Adding the 1.5" block moves the ride height in the shock travel range downward 1.5" from where it used to be. You thereby gain 1.5" of up travel and lose about the same amount of down travel. Many people want this extra up travel for high speed and jumping, hence, many published lift ranges.

The next longer Bilstein rear shock, non-reservoir and non-bypass, is the 5125. It is 24.38" extended length, but compressed length is now 15" instead of 14", which pretty much requires a slightly longer rear bump stop. The 5125 has .45" more total travel than the standard 5100. With a 1.5" block lift instaled, 5125 gives back 1.38" of down travel. Up travel gained now is just .12", assuming a slightly longer bump stop.

Given the total travel space constraints of the stock mount locations and work involved to relocate and weld new mounts, the longer bump stop install work, and desire of many for additional up travel, most people will be happy with 5100 rears with a lift, or 5160s with wide bodies and reservoirs, at 14.2"-23.6" travel, well within stock fit parameters, unless you specifically want max down travel, i.e. slow, rough offroad/ rock crawler users.

Ha, I just write up long form because it takes more than 3-4 sentences to explain all angles. I rearranged different leafs, blocks, AALs, and shocks, multiple times, on my 2016 OR last year, trying to dial in a 1" lift with max flex, running mostly empty bed offroad, with 400 lbs suspended armor and bed cover weight. 1" is harder than 2" lift as most 3rd Gen products are geared to 2". Yes, I have a collection of extra parts in my garage now.

My ride is a Frankenstein of different manufacturer parts to get what I wanted, keeping my bed as low as possible for in and out work use, yet still offroad worthy. My front hub center to fender is 22" and my rear hub center to fender is 23.25". Both about 1-1.5" give or take, over new stock height.
I run General Spring HD leafs right now, cheap but effective, and keeps my rear low, yet high enough to give my neg offset 33s room to sneak up into the fender wells I run rear Fox 2.0 shocks, 24.8" extended length, in the stock mounts. My rear bumps plus flip bracket are about 3.5". This gives me about 4" up travel and 5.5" down travel at the shock, both ends being maximized by just enough bump stop to prevent overcompression and leafs with droop more than 24.8" down.

Now if I didn't use my truck rear for work and I was taller, I'd spec everything for 2" lift front and rear, and saved myself alot of time and money, and ease of measurement and fit.

 

I forgot to specifically add that more uptravel on a given extended length rear shock, is gained by increasing rear lift more than the minimum rear lift that I sought in my case, 1.5", which settled to 1.25", which still provides about 4" uptravel before hard bump stop.

3" rear lift will easily see a near 2" of additional uptravel on the same size shock, which is a big factor in aftermarket manufacturer suggestions for rear shock lengths to lift height.

As for bump stop length manufacturer suggestions, a better measure to use than lift height, which most do, would be how much extended stop over stock bump length is needed, based on new size shock compressed length. This can be calculated given a weight on compression scale or sample ratio. Durobumps to their credit, provides the latter part.

 

Here is the same longer shocks concept, fitted onto my FJ Cruiser this week, 26.5" extended length, 15.2" compressed length OME shocks. The old Icon shocks are approximately 14.8" compressed length and 24.8" extended. The 3" rear lift springs, weighted down by bumper and gate mounted spare tire, still keep over 5" uptravel of the available 11.3" shock travel on the new shocks. The remaining available travel goes toward downtravel.
Raising more or lowering the rear lift would change the ride point within the travel range and division between up and down travel.

Before longer shocks, no bump stop contact even with 4.25" compressible bump stops:

After longer shocks, allowing more rear droop and axle tilt. The bump stops are now touching but not compressed on these 12.75" cross axle ramps:

 

Not sure if maybe I missed something in your post or misread it, but the simple addition of a 1.5" rear block on a Tacoma does not increase uptravel at all. This is because the bumpstop is directly on top of the leaf spring, the position of which is not changed by the block.
What is changed is the amount of downtravel the shock will allow from the new (1.5" taller) ride height... Because you moved the axle downward 1.5", the shock is now that much closer to reaching fully-extended and will cut that amount off from your downtravel. Since the uptravel didn't change, your total travel will now also be 1.5" less (the shock's compressed length from 14.02" to 15.52" no longer being utilized because the axle is 1.5" further away).

To regain that downtravel, (as you said) you do need longer shocks.
In your example of using lift blocks, the minimum distance the shock mounts can compress to is also increased by the amount the block is thick. This means that (in theory) you should actually be able to increase the (extended) length of the shock by double what the block is thick and not have it bottom out, since the increase in collapsed shock length would be half that of the increased extended length.

You showed that the factory spring/shock configuration already cuts off some downtravel, this should easily allow you to use pretty much all the travel the leafs are capable of without risk of bottoming out the shock.

The above however does not apply if lifted with replacement leafs (instead of blocks). In this case uptravel does increase because the bumpstops are moved further away from the frame with the lift. This means that with extended shocks, the bumpstop distance potentially would need be decreased since the axle can still move up to the same position it could before (minus any difference in leaf thickness).

Hopefully that makes sense.

 

Wherever I wrote that lifting blocks or the AAL thickness would increase the same shock uptravel on the same leafs and same bumps, I stand corrected. Thanks.

As to total shock travel, blocks to me fix a certain amount of downtravel in, so I generally define the total shock travel to still be the same, not less. I may have tripped myself up writing without defining it and/or using both views.
Again, thanks for clarifying.

 

Thanks for the comprehensive post and saving us a lot of time!

I have Dobinson 111R leafs ready to go with 5100 rear shocks. Since 111R's have 2" lift due to thicker leaf pack, and 5100 rears have roughly the same travel as stock, I feel I'm just trading down travel for up travel. Do you know how much down vs up travel is on the stock rear shocks?

Alternatively I'm thinking of getting the 5125s which has 1.4" more total travel. The fully collapsed length is 1" longer than 5100. Based on your post, I wonder if the 111R's has a fully droop that can make use of 5125's longer travel. I also wonder if stock bump stocks will still suffice, since on paper leaf packs add 2" and collapsed length on 5125's are only 1" longer. Can it be understood that way or does the curvature of the leaf pack also play a role in whether you need longer bump stops or not?