Benefit to larger rezzy than shock body? Intro to my new shock quest

Welcome to DezertRangers
Join the community. Register today for all the benefits of membership.
Register

ASHCAT

Member
Dec 8, 2016
57
0
6
Any advantage to retrofitting a 2.5 remote rezzy to a 2.0 shock?

Currently running 2.0 14” king C/O but want to upgrade to their compression adjusters on all 4 corners. Just a thought while I have them apart and will be purchasing the new reservoirs.


Been reading a lot of mixed info about 1:1 axle mounted shock applications. Vehicle in question is a (soon to be) 4,800lbs Ultra4 solid axle, front engine and 55/45 split. Single shock vehicle. Bypasses aren’t feasible for this build in particular. Disc brake Dana 60/70, trussed and 37s (130lbs/corner tire/wheel) I read the 2.0 is pretty much maxed out at that kind of weight but 2.5 is trying to move too much oil and isn’t of any benefit for 1:1.


I’m new to shock tuning but have a pretty good grasp of the fundamentals. I’m familiar with the parts. Been into my fox 2.0 bumps to destroke them and have since revalved them, tried a new oil, adjusted the oil volume and will be working with nitrogen pressure once I get the shocks straightened out. Prior to my first KOH I had a local tuner molest my setup. (Factory king F15/10). Guy turned out to be a self proclaimed know it all and a flake. His fees were ridiculous and claims were false. Heavier and heavier spring rates with no preload was his go to game plan. This turned the vehicle into an unpredictable and violent death trap. A local racer advised me to go back where I was with springs and I’ll be damned if that’s not exactly what king prescribed on the lakebed. Lighter is better. Originally I was 150/200 14” springs x4 out of the box. I later changed to 185/200 front and 175/200 rear. The front was still a bit too light after the first season of wheelin. Kings advice was 150/200 rear and 200/250 14”/16” front. I like it and I’m going to keep these springs. Post race fueled my fire to learn something new and take matters into my own hands.

The shock tuning was absolutely garbage and the desert lap was brutal on the truck. We ate the front bumps for 63 miles and I was being easy. I feel as if I have very little compression dampening and the front packs. The front bumps hydro locked since there was 120cc of oil with a stroke of 1-1/2” I was running 200psi in them and in the shocks. The strike pads are destroyed on the front.

The rear felt ok to us and no harshness in the bumps. 2-1/2” stroke 90cc and 150-180psi. I feel as if the 2.0 shocks are sufficient in the rear but need some proper tuning still. The rear reservoirs melted the stickers off though.

Where should I start in the front? Proper 2.0 tuning with or without a 2.5 rezzy or go to the extent of retrofitting a 2.5 shock up there? My frame is wide and I’d have to recess and modify a few things to accommodate the larger coil. Is a 2.5 worthwhile with the appropriate piston? I hear fox is superior and flows much better but I also read that a low flowing piston is sometimes more beneficial. Tuning preference maybe? I don’t want to get too carried away with expense or parts because this truck will only race once more and be retired to trail duty. I’ll do it if it really pays off.

So moving forward here’s where I’m at to begin with.
Overall weight reduction. Official race weight was 5,123. Goal is to shed 300-500lbs
New valving profiles for bump stops. 2” travel front 2-1/2” travel rear. Appropriate oil volume and 50psi to begin
Compression adjusters for all 4 corners
Tear down shocks and evaluate current garbage valving and oil volume. Will I find something scary like professional shock gurus do? Lol
Test and move forward with new my new shock oil as recommended by this board.
Decide upon front shock shock body diameter.
 

FasterNU

Mega Member
Jun 28, 2006
6,877
382
83
San Diego
Any advantage to retrofitting a 2.5 remote rezzy to a 2.0 shock?

Currently running 2.0 14” king C/O but want to upgrade to their compression adjusters on all 4 corners. Just a thought while I have them apart and will be purchasing the new reservoirs.


Been reading a lot of mixed info about 1:1 axle mounted shock applications. Vehicle in question is a (soon to be) 4,800lbs Ultra4 solid axle, front engine and 55/45 split. Single shock vehicle. Bypasses aren’t feasible for this build in particular. Disc brake Dana 60/70, trussed and 37s (130lbs/corner tire/wheel) I read the 2.0 is pretty much maxed out at that kind of weight but 2.5 is trying to move too much oil and isn’t of any benefit for 1:1.


I’m new to shock tuning but have a pretty good grasp of the fundamentals. I’m familiar with the parts. Been into my fox 2.0 bumps to destroke them and have since revalved them, tried a new oil, adjusted the oil volume and will be working with nitrogen pressure once I get the shocks straightened out. Prior to my first KOH I had a local tuner molest my setup. (Factory king F15/10). Guy turned out to be a self proclaimed know it all and a flake. His fees were ridiculous and claims were false. Heavier and heavier spring rates with no preload was his go to game plan. This turned the vehicle into an unpredictable and violent death trap. A local racer advised me to go back where I was with springs and I’ll be damned if that’s not exactly what king prescribed on the lakebed. Lighter is better. Originally I was 150/200 14” springs x4 out of the box. I later changed to 185/200 front and 175/200 rear. The front was still a bit too light after the first season of wheelin. Kings advice was 150/200 rear and 200/250 14”/16” front. I like it and I’m going to keep these springs. Post race fueled my fire to learn something new and take matters into my own hands.

The shock tuning was absolutely garbage and the desert lap was brutal on the truck. We ate the front bumps for 63 miles and I was being easy. I feel as if I have very little compression dampening and the front packs. The front bumps hydro locked since there was 120cc of oil with a stroke of 1-1/2” I was running 200psi in them and in the shocks. The strike pads are destroyed on the front.

The rear felt ok to us and no harshness in the bumps. 2-1/2” stroke 90cc and 150-180psi. I feel as if the 2.0 shocks are sufficient in the rear but need some proper tuning still. The rear reservoirs melted the stickers off though.

Where should I start in the front? Proper 2.0 tuning with or without a 2.5 rezzy or go to the extent of retrofitting a 2.5 shock up there? My frame is wide and I’d have to recess and modify a few things to accommodate the larger coil. Is a 2.5 worthwhile with the appropriate piston? I hear fox is superior and flows much better but I also read that a low flowing piston is sometimes more beneficial. Tuning preference maybe? I don’t want to get too carried away with expense or parts because this truck will only race once more and be retired to trail duty. I’ll do it if it really pays off.

So moving forward here’s where I’m at to begin with.
Overall weight reduction. Official race weight was 5,123. Goal is to shed 300-500lbs
New valving profiles for bump stops. 2” travel front 2-1/2” travel rear. Appropriate oil volume and 50psi to begin
Compression adjusters for all 4 corners
Tear down shocks and evaluate current garbage valving and oil volume. Will I find something scary like professional shock gurus do? Lol
Test and move forward with new my new shock oil as recommended by this board.
Decide upon front shock shock body diameter.
Not sure the info really relates to the "title" .... but to answer the first question in the body of post:

In theory, for a given hose diameter and given pressure.... a larger diameter external reservoir will combat piston plunge/cavitation better than a smaller external reservoir would. Simply because there is more surface area on IFP (think pounds per square inch)

But, I would think you need more shock than 2.0's for sure.

I don't understand the logic behind the second part of this comment:
I read the 2.0 is pretty much maxed out at that kind of weight but 2.5 is trying to move too much oil and isn’t of any benefit for 1:1.
 
Last edited:

ASHCAT

Member
Dec 8, 2016
57
0
6
Sorry, I’ve got a lot of questions and ideas flying around so I was struggling to get started but get as much info/questions out there. That’s why I included new shock quest in there.

So it is a practice to equip smaller body shocks with a larger body reservoir? Wouldn’t be a waste of a 2.5 rezzy if ultimately I upgrade to a 2.5 shock. Hmmm

From what I can tell there’s debate to whether or not a 2.5 single c/o is beneficial over a 2.0 on a 1:1 solid axle mounted shock because there is not enough leverage to correctly or efficiently force the larger piston through the larger volume of oil. Harshness on compression or inability to rebound light enough to extend the shock quick enough. But I read those issues are circumvented with superior flowing piston designs. Seems the common ground is retain 2.0 coil carrier and add a 2.5 bypass in those claims/arguments. Not going to to happen with this build. No room period for bypasses. In fact I’m not even interested in them because I know how smooth/fast a single shock car can be in the U4 world. The legends guys could smoke me in the desert and it’s not all about them running trailing arms. My quest is to perfect the single shock.

I can can provide more detailed shock setup. Angles, sway bar, wheel base, scale weights, etc. It’ll be a few weeks before I can inspect current shims and oil volume because I’ve got some other jobs going. No matter what, I’ve got to solve why this truck blows through the compression.

117.5 WB

1” minor diameter sway bar, 42” long, 16” arms links set at 15”, 12” links, flat arms at ride

Front shocks laid back 12* inward 15*

Rear shocks laid forward 10* inward 15*

Front and rear links are nearly level

limited front uptravel 6”. 4” before bump contact and 2” bump stroke

Rear uptravel is 7”. 4.5” before bump contact and 2.5” bump stroke


Will provide scale weights later with approximate unsprung weight figures.
 

dsrtrcr01

Well-known member
Jan 31, 2005
3,744
176
63
Not a shock guy but my last truck was a 94 2wd Toyota. Very light. I ran a 2.5 18 inch fox right off the rear axle with 18 inches of travel. Had it tuned and it worked amazing. I am now running a heavier 4 runner with a Fox 2.5 bypass and it works good. Once tuned it should rock. So you need bigger shocks in my opinion
 

ASHCAT

Member
Dec 8, 2016
57
0
6
I’ve been leaning heavier towards upgrading the front to 2.5. So which brand? Do I concern myself to the point of losing sleep over piston design between manufacturers?- (At my level) I’m more than capable, ready and excited to tune once I get going in the right direction. I just don’t want to waste money pursuing the wrong shock choice moving forward. Meaning it would be silly to buy a 2.0 shim kit from king if I’m just going to go bigger in the end. Really wish I knew the valving profile now to validate this thread further.

How is king to work with over the phone? Preferred king dealers that know their stuff and their product? Gerardo Iribe was very helpful on the lakebed but unfortunately I didn’t have a chance to tune with him. Would like to stay with king at this point.
 

dsrtrcr01

Well-known member
Jan 31, 2005
3,744
176
63
Again I am not a shock pro but I like fox. Stainless shafts so no rust, better resi lines. If you search the net there are some comparisons done between king and fox and in those fox wins for quality of products used. I don’t know if they used a certain type of king or whAt. I have ran king, fox, sway, doetsch, Rancho, bilstein and so on. I am sticking with fox. Once tuned I got them to work best for me. No leaks or failures so far
 

ASHCAT

Member
Dec 8, 2016
57
0
6
Yeah I know how those comparisons go.....and Fox seems to come out on top. I’ve read just about every article I can find by Ryan or Wayne. Seems like Fox is a good investment.
 

only1mikey

OG Member
Apr 24, 2006
11,979
28
48
Simi Valley, CA
Without going too far into things cause you are all over the place. Your question my answer (in my opinion).

Run whatever resi sizes you want, it's not going to change anything with a compression adjust resi. How the compression adjust resi works is it restricts flow so the size doesn't matter. Personally I really like the little Sway-A-Way resis on low travel shocks cause it ramps up the N2 more, building more bottom resistance, which is nice when you have a single shock (this if for a standard resis without compression adjusters). But others swear by bigger resis. Some claim they cool the shock more, more oil volume or whatever, but without two hoses and some short of check valve all that fluid is doing is moving in and out of the hose into either the resi or shock.

One thing I noticed when reading about your setup is your lack of up travel. You can have the best shocks in the world right now on your car and with 6 and 8 inches of up travel it's going to hinder your go fast off road performance. I know it's tough to setup a straight axle car to have good up travel numbers without them being monster trucks and working well in the rocks.

What I think you should consider since like you said you aren't going to be racing the car much longer is just get the setup you have now to work as good as you can. Spend the money getting the car out west and work with a competent shock tuner. But if it's in the budget get those compression adjust resis cause they do help wonders with cavitation on a single shock setup.
 

Tchajagos

Senior Member
Feb 12, 2010
1,600
7
38
Riverside
Hard to say if you should go to 2.5 or not. If you were keeping the truck I would say 3.0 minimum for desert race or 2.0 coilovers with 2.5 bypasses. For a 5k lb truck. A 2.5 resi will help to keep the shock a little cooler because it has more surface area to dissipate heat and more oil.
 

ASHCAT

Member
Dec 8, 2016
57
0
6
Without going too far into things cause you are all over the place. Your question my answer (in my opinion).

Run whatever resi sizes you want, it's not going to change anything with a compression adjust resi. How the compression adjust resi works is it restricts flow so the size doesn't matter. Personally I really like the little Sway-A-Way resis on low travel shocks cause it ramps up the N2 more, building more bottom resistance, which is nice when you have a single shock (this if for a standard resis without compression adjusters). But others swear by bigger resis. Some claim they cool the shock more, more oil volume or whatever, but without two hoses and some short of check valve all that fluid is doing is moving in and out of the hose into either the resi or shock.

One thing I noticed when reading about your setup is your lack of up travel. You can have the best shocks in the world right now on your car and with 6 and 8 inches of up travel it's going to hinder your go fast off road performance. I know it's tough to setup a straight axle car to have good up travel numbers without them being monster trucks and working well in the rocks.

What I think you should consider since like you said you aren't going to be racing the car much longer is just get the setup you have now to work as good as you can. Spend the money getting the car out west and work with a competent shock tuner. But if it's in the budget get those compression adjust resis cause they do help wonders with cavitation on a single shock setup.
I was hoping you’d chime in among others. I literally read through every relevant thread in this section in the last 2 months.

I know it’s a bit unorganized, I’m anxious and unfamiliar with expressing my questions or understanding in the right terms. At any rate, the curiosity for larger reservoirs is because I’ll be upgrading and just wanted to know if it was a stupid idea, mute effect or had potential. I’m not so concerned about heat. I want dampening control. So, I’ll stick with 2.0 w/comp adjuster in the rear and a matching 2.5 package w/comp adjuster in the front.

My truck is low. 77 F-150. It’s probaby not any higher if not lower than original. The front frame rails are in the stock location. I removed 4” off the bottom of them. I didn’t get crazy with trying to accommodate 8” uptravel. 6” at best depending if I want my ride height up there.

So a smaller shock and or rezzy benefits in dampening control by ramping up the gas and a 2.5 shines with oil volume/surface area?

For optimum dampening effect, do you want the stroke to bottom out? Right now I measure 1-5/8 shaft left at full bump. When I come in contact with my bumps, I have 3-5/8“ shaft before utilizing 2” stroke of the bump. I can negate this two ways, buy kings standard 2.5 x 14” or change my axle mounts. Increase their height.

I plan to go west alright. Lol I live in slc and have some epic terrain ideal for repeat shock tuning in Wendover.


Hard to say if you should go to 2.5 or not. If you were keeping the truck I would say 3.0 minimum for desert race or 2.0 coilovers with 2.5 bypasses. For a 5k lb truck. A 2.5 resi will help to keep the shock a little cooler because it has more surface area to dissipate heat and more oil.
Class is limited to 2-5/8 body. Most run the bypass combo you mentioned but it hasn’t proved to be superior. Cars are still competitive on single shocks in both 4500 and per the rule in 4800.

My focus is KOH getting through the short 5, 8, 10 or
whatever mile bursts of desert between washes, hills and the rocks at anything faster than a craptastic 18-20mph while still blowing through the compression. Hell, cherocars were faster than me.
 

Latest posts

Today's birthdays

New Threads

New Classifieds

latest desert trips

Member Builds