Would you guys do anything with these values?
AHC question for the pros (1 Viewer)
- Thread starter dchilds
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
trdcorolla
SILVER Star
Yes, you can read through these threads to get you started.
forum.ih8mud.com
forum.ih8mud.com
Definitive list of AHC maintenance items
My nagging "issue" with AHC is wondering if the suspension doesn't feel quite right. I feel bumps pretty well and I subjectively recall an older 100 series land cruiser standard suspension feeling like being on a cloud vs the small cracks in the road. The question is driving me insane when I'm...
forum.ih8mud.com
The ABCs of AHC - How to Measure, Flush, and Adjust all in one place
I initially put this in the Definitive list of AHC maintenance items thread, but at almost 800 posts long and growing, it's going to get buried and the thread itself is very unwieldy. In an attempt to make as focused a summary as possible, I present "The ABCs of AHC." It's intended as a...
forum.ih8mud.com
yes I would aim to lower both of the pressure values
The front is done by simply turning large bolts that preload the torsion bars
The rear will need to be done with new springs, spacers, or a combination of both depending on how much weight you carry.
The links above will get you on the right track.
The front is done by simply turning large bolts that preload the torsion bars
The rear will need to be done with new springs, spacers, or a combination of both depending on how much weight you carry.
The links above will get you on the right track.
Yes, assuming neutral heights are all correct (or adjusted how you want them), I'd turn the torsion bars until Front is around 6.7. I'd consider adding rear King springs or 30mm spacers. The springs would be good if you plan to add any weight (rear bumper, cargo system like the SS1, or regular towing). The spacers would be good for continued use loaded up as it was for this screenshot.
- Thread starter
- #5
I took a few more pressure readings and my average came down a hair. I put one full turn on each TB and rechecked. I came up with a value of 6.6. I think I'm on target. As far as the rear goes, this is my daily driver and I don't carry much weight around for long periods of time. On occasion, I'll have it loaded up for a hunting trip etc. but no constant load. I assume I just get new OEM springs, correct?
My front height at neutral is sitting just under 19.5. I'm reading the target is 19.75". My height sensors are 0" +/-.1". What do I do from here?
dchilds, I'd be tempted to call your front height fine and move on. You can adjust the sensors a bit to raise it slightly, but then you'll have to tighten the torsion bars again, and I'm not sure that's worth the effort. Buy some new OE springs or spacers and call it a day.
ramangain
Clarksonian disciple
I would not sweat 1/4" height delta on the front fender to hub center distance. IMHO that "spec" needs plus/minus 1/4" tolerance anyways.
Not a ‘pro’ but agree with all the previous replies. Looks like you have followed the AHC mantra and have recognized that the sequence is important:
- Equalise front cross-level hub-to-fender using Torsion Bar adjusters,
- Get ‘operating heights’ a.k.a. ‘ride heights’ correct using Height Control Sensor adjusters at Front and Rear,
- Get AHC Front and Rear neutral pressures in specified range at correct heights using Torsion Bar adjusters at Front, if necessary consider spacers and/or replacement springs at Rear, noting that damping performance and longevity usually are best when AHC pressures are a little below the mid-point of the specified ranges,
- When heights and pressures are correct, check overall ‘globe’ condition by measuring difference in graduations at AHC Tank at “LO” height and “HI” height, noting that ‘correct’ AHC pressures by themselves cannot tell anything about the condition of the ‘globes’ and also that this test at wrong pressures is pretty close to meaningless.
Heights are slightly low – but not by much. Heights and AHC pressures are inseparable. Basic mechanics: more height, less spring force to carry vehicle weight, so more AHC force to carry a greater share of vehicle weight which means higher AHC pressures. Or vice versa, so slightly lower heights than ‘standard’ would mean slightly lower AHC pressures than standard, all other things being in order.
Height and pressure variations noted in other threads by @PADDO and subsequent others estimate variation of ~2.2Mpa per inch of height variation at Front and ~0.6MPa per inch at rear, relative to IH8MUD hub-to-fender ride height ‘standard’ of 19.75 inches at Front and 20.50 inches at Rear. (Note: These hub-to-fender numbers are widely respected IH8MUD approximations, not FSM specifications).
So conceivably quarter-inch low at Front might be worth 25% of 2.2MPa, say ~0.55Mpa pressure relief at Front? If perfection is pursued by increasing Front height by quarter-inch using Height Control Sensor adjusters, then the resulting increase in pressure would need to be off-set by winding on another (say) two to three turns at both Torsion Bar adjusters at Front (at ~0.2MPa AHC pressure change per full turn).
This effort does not seem worthwhile unless the lost quarter-inch of height is desperately needed for some obscure reason!!
In addition, there are various other causes of variation as implied by @ramangain and @suprarx7nut. Not least of these is the accuracy of hub-to-fender measurements – in my own case I doubt that I am better than +/- one-eighth inch and maybe not better than +/- one-quarter inch if rushed or light is poor.
There is support for some Rear AHC pressure correction – in my case, it was done with KING KTRS-79 springs, others are happy with OEM new AHC springs and spacers -- all depending on intended loads and weight of added fittings. For a lifted vehicle it is a whole different ball game. Originally fitted AHC springs are well past their best if still in place on LC100/LX470 vehicles which are now 14 to 22 years old.
By the way, in addition to other threads quoted in earlier replies and if not seen already, see also:
Builds - The YotaMD Build - Cypress - https://forum.ih8mud.com/threads/the-yotamd-build-cypress.1184210/page-9#post-13383404
- Thread starter
- #10
Thanks for all the thorough responses, guys! I really appreciate the efforts. I decided to leave the front alone after turning the torsion bars one turn each. Pressure is in spec and height is close enough for me right now. I ordered a set of OEM springs for the rear to bring the pressures down a bit. I'll report back when I have new numbers after that installation.
For what it's worth, I'm super impressed with the ride quality of the AHC. I previously had a 2004 LC without AHC and now have a 2003 LX with AHC. Both relatively low mileage vehicles. I replaced the rear springs and shocks all the way around in the LC. The ride difference is noticeable to me - in favor of AHC. Though, I recognize there are additional costs and headaches (albeit minor, in the scheme of things) that come along with AHC. I'm happy with the setup.
For what it's worth, I'm super impressed with the ride quality of the AHC. I previously had a 2004 LC without AHC and now have a 2003 LX with AHC. Both relatively low mileage vehicles. I replaced the rear springs and shocks all the way around in the LC. The ride difference is noticeable to me - in favor of AHC. Though, I recognize there are additional costs and headaches (albeit minor, in the scheme of things) that come along with AHC. I'm happy with the setup.
...definitely a pro
