Understanding rear leaf springs.

[fred heath]

There seems to be a great deal of confusion regarding rear springs and ride height.

The Toyota axle sits ABOVE the top most leaf. Adding extra springs may stiffen the ride, but will not alter the ride height to any degree. They just add extra weight to the vehicle.

There are two means available to increase ride height. Air bags which rest between the frame rail and the top of the axle, which in effect push the coach body up, or shackle extensions which elevate the frame rails from the drivetrain again elevating the body.

I chose shackles as they are passive and not subject to failure.

These are your only options. (you could try relocating the axle below the bottom spring, but you would end up too high).

[zero]

There seems to be a great deal of confusion regarding rear springs and ride height.

The Toyota axle sits ABOVE the top most leaf. Adding extra springs may stiffen the ride, but will not alter the ride height to any degree. They just add extra weight to the vehicle.

There are two means available to increase ride height. Air bags which rest between the frame rail and the top of the axle, which in effect push the coach body up, or shackle extensions which elevate the frame rails from the drivetrain again elevating the body.

I chose shackles as they are passive and not subject to failure.

These are your only options. (you could try relocating the axle below the bottom spring, but you would end up too high).

You lost me. I think you share some of the "confusion." Adding leafs - or fixing the olds certainly does add height. The springs are supposed to rid with a certain arch that gives ground clearance. When loaded heavy they flatten out and the RV gets closer to the ground. Add some leafs and it comes up a bit. Have the old springs rearched and heat-treated and it can also come up.

Shackle extensions often effect handling in a negative way. Very common in the 1960s and early 70s on muscle cars when we did not care about handling.

I added three leaves per side on my Chinook and it now sits 3" higher then before.

The OEM leaf spring assembly is two stage. When heavy and riding on the 2nd stage - the truck sits lower.

[fred heath]

I disagree JD.

The arch of a new spring will add a certain amount of lift. If you added all new springs to both sides you will get some lift. But only as long as the arch stays constant. Over time the spring will compress. The top leaf if replaced with a new better arch will lift the vehicle. But not to any sufficient degree.

As far as shackle extensions go, your thinking the 70's. Mine are 3/8 black steel. I have a center hole which will brace the shackle and prevent "twisting". It's a very strong setup. I have pictures but haven't figured how to upload them from my phone.

If your top leaf is original I don't care how many extra leafs you add, your not going to see an increase in height when loaded.

[zero]

I disagree JD.

The arch of a new spring will add a certain amount of lift. If you added all new springs to both sides you will get some lift. But only as long as the arch stays constant. Over time the spring will compress. The top leaf if replaced with a new better arch will lift the vehicle. But not to any sufficient degree.

As far as shackle extensions go, your thinking the 70's. Mine are 3/8 black steel. I have a center hole which will brace the shackle and prevent "twisting". It's a very strong setup. I have pictures but haven't figured how to upload them from my phone.

If your top leaf is original I don't care how many extra leafs you add, your not going to see an increase in height when loaded.

I've got clear proof that you are wrong - sittting in my driveway. 1978 Chinook that still has the original main leaf (the one that attaches to the spring perches). 3.5" higher now after I added some leafs. You can say what you want and theorize - but I did it and it worked as decribed.

Springs leafs are heat treated to retain a predetermined arch that gives the proper height under a certain weight load. They get tired over time and sag. If you add leafs with the proper original arch that the truck calls for - it rises.

You claim otherwise until you turn blue in the face - but I've fixed a lot of leaf spring packs in my life and always gained height. That is except in the case of the inverse leaf springs used in the front of some 4WD trucks. They have an "upside-down" arch.

Just about every Toyota RV I've looked at close has flattened out leaf springs that no long have the factory arch - unless they've been repaired or beefed up. Or air bags or load-assist shocks were added.

Your are free to think whatever you want - but don't tell people who have fixed their spring packs that they are "confused."

In regard to shackles. No matter how strong they are - the longer they are - the more "leverage" they have to sway sideways.

If somebody wanted their RV even higher then stock - getting the leafs "re-arched" at spring shop is a way to do it without adding shackles or air-bags. But the packs of leafs must be adequate to handle the load or they will settle fast and lose the arch.

[fred heath]

What ever......

Mine is real world too. I drive it every day. I evaluated adding extra springs be could see no advantage. You seem to have many projects going in your yard. Are any of them on the road?

Knowing you need to have the last word, I'm done with this thread.

Unlike you, my pencils come with erasers.

[zero]

That's a bit childish. I do something that works - and to please you I should say it did NOT work?

Just because you did not see any advantage does not mean it does not exist.

Geez. You are the one that announced that some of us are confused. You make it sound like it's the other way around.

I don't know how much mechanical experience you've got with suspension work - but ride-height is probably the #1 reason why people have their leaf-springs re-arched -or add leaves. Not so easy to re-arch any more since it takes a good spring shop and many have gone out of business. Cheaper just to buy new.

Since you expressed a need to know - I have three RVs on the road at present. Four if I include my 1992 Dodge truck with a camper on the back. Ironically, I just lowered the back by 6" instead of raising it. Axle is underslung and all I had to do is remove the OEM riser-blocks.

Dimension "C" in these charts is what determines ride-height. It gets lesser over time as spring lose their arch and sit lower. Especially in Toyota RVs.

[MontanaChinook]

I see that you first say adding leaves will give you no height, then just a bit later you say it will give you temporary lift.

So obviously it does give you lift.

It isn't where the axle sits, it the arch that gives you height. I mean obviously if you put the spring on top of the axle like it is on toyota 4x4s, that would give you lift. But it's the arch giving lift. Every description I see of add-a-leaf products advertise the amount of lift you'll get. I don't see how being sprung under or over has anything to do with it. But I'm no suspension expert!

My added leaves at first gave my truck probably 3". It's since settled at about 1" lift.

Just my experience, which I've learned means a lot more than stuff on the Internet.

[MontanaChinook]

Actually reading back through I'm not sure exactly what you're arguing. You say, a couple times, that you WILL see an increase in height with added leaves. So we all agree. Adding leaves gives you lift.

The whole "until the springs lose their arch" is like saying a toyota engine only runs until the timing chain breaks, then it doesn't run. So the conclusion is that toyota engines don't run.

The sag you see in all pre-2000 4Runners is from the rear leaves losing arch. They started at one height, but weren't heavy duty enough so they sagged and the rear dropped, just like in a pickup used to carry heavy loads.

You add a couple leaves, the height is returned, because with or without a spring shop re arching the old springs, the new added leaf does that a bit on its own. Until it wears out again and loses the lift.

So I guess your point is about PERMANENT lift?

Anyways, its common practice to lift a vehicle with added leaves, so I don't see the confusion that you do.

[fred heath]

I see that you first say adding leaves will give you no height, then just a bit later you say it will give you temporary lift.

So obviously it does give you lift.

It isn't where the axle sits, it the arch that gives you height. I mean obviously if you put the spring on top of the axle like it is on toyota 4x4s, that would give you lift. But it's the arch giving lift. Every description I see of add-a-leaf products advertise the amount of lift you'll get. I don't see how being sprung under or over has anything to do with it. But I'm no suspension expert!

My added leaves at first gave my truck probably 3". It's since settled at about 1" lift.

Just my experience, which I've learned means a lot more than stuff on the Internet.

When I first redid my suspension I added 4 additional leafs per side. The unsprung lift was noticable but as soon as weight was applied (like you experienced) the ride height disappeared. Maybe an inch at best.

Perhaps I should qualify my statement in terms of money spent vs desired goals. How many leafs would it take to get you to that magic 3" mark mentioned earlier? And over time that arch will depress even more as the springs stretch.

3" shackle extensions gave me 1.5 inches of body lift with no extra leafs or special hardware.

With deep pockets I'm sure you could elevate the ride height to anything you wanted.

[MontanaChinook]

Used leaves or new? Four is a lot!

I would expect used leaves to give more weight capacity but very little lift. Where two very arched new springs per side would give quite a bit.

Obviously with my camper, its always "loaded". The weight is always there. Yeah, my 3" lift settled in to a 1" lift. I'm thinking another leaf on each side would be perfect, since I'm going for stability, with a little extra height being a bonus.

[WME]

A spring is rated in lbs per inch for deflection. Leaf springs come with a designed arch in them. When you add load the spring will deflect based on the load. It also grows longer, thus you need shackles at least at one end.

As the spring ages (wears out due to constant overload) the arch becomes less so with the same weight it deflects about the same amount, but it is starting from a flatter arch so the back end sags.

Adding leafs increases the spring rate (stiffness) so even though the main spring has less arch the spring rate goes up and the spring pack deflects less. So the back end comes up. Of course the rig rides harder

Re-arching springs is normally a waste of time and money as most places do it cold, ie just rebend the sucker big time. Re-arching hot and re-tempering will restore the spring to almost new. But there are VERY few places that can do this.

Re-arching cold and adding extra springs will last longer but eventually it will sag too as the extra leafs are caring a lot of the load.

Best is a new spring pack with the correct capacity, airbags would be next best.

.

[zero]

Leaf spring packs are made to carry a X amount of weight and provide X amount of height that is determined by the spring-arch.

Someone correct me if if I'm wrong -but as far as I know - in the USA, the Toyota Chinook was the only Toyota RV that Toyota had any direct input with.

All the other Toyota RVs that I am aware of - came with leaf-spring assemblies NEVER intended to be fully loaded full-time. They are progressive-rate springs and the general design allows a soft ride and high spring arch under "normal" conditions. Not during "fully loaded " conditions. Even the Toyota 1 ton box trucks were designed to be driven empty or partially loaded much of the time.

So we have the situation where RV builders were buying Toyota cabs and chassis with "part-time heavy load" springs - and outfitting them so they are at or near max load 100% of the time. Many companies factory installed air-bags to make up the difference instead of beefing up the springs. I.e. a cheap fix.

If you take a Toyota RV, re-arch or renew the most of the leaves - and then add a few it will ride higher then when new (not counting air bags), and a lot higher when it had used and flattened out leaf springs.

This is suspension 101 and I don't comprehend the argument here. To say beefing up the springs will never increase ride height is silly.

[Gary_M]

I should do that to my leafs given the scenario you provided JD. My rearend sags but the airbags keep it somewhat level. I still bottom out at gas stations and even the drivway. The bags are getting old to the point of replacement. I'm going to get a set of superior helper springs, cut the airbags in half and slip the helper springs over the old air bags. I heard that give it some extra lift and a lot cheaper than airbag replacement or adding leaf springs.

[zero]

It was nice when there used to be old fashioned spring shops around that would re-arch springs. Not so common anymore. Nearest one to me is over 100 miles away. New springs from overseas have gotten so cheap - it put many spring shops out of business. At least here in the northeast.

Several auto parts stores in my area sell generic spring stock. You buy the desired thickness and width and cut to length with a torch. Problem is - they come with a generic arch and often won't match the arch needed.

What I've found to be a cost-effective fix is to buy either new spring assemblies - or good used from a Toyota truck that has not been overloaded its whole life. Then cut the stacks apart and add those leaves to the RV being worked on.

One other item about springs. Very often the rubber "bump stops" are missing on Toyotas (and all the other make trucks I know off with leafs). They fall off over time - especially where I live.. They are there to prevent the springs from travelling too far which wears them out faster - or allows them to break when you hit a big bump. If you are working on your springs - make sure you've got good rubber bump stops installed.

Toyota uses an odd-ball leaf spring size so leaf spring stock is not as easy to find as with other trucks. USA trucks and SUVs commonly have leafs that are 2 1/2" or 3" wide. Toyota uses leafs that are 2 3/8" wide X 1/4" thick. So does Mazda and some Ford Rangers. Not sure what else. The last spring pack I worked on (Toyota truck) I added some leaves that are 2 3/8" wide x 5/16" thick.

[WME]

I should do that to my leafs given the scenario you provided JD. My rearend sags but the airbags keep it somewhat level. I still bottom out at gas stations and even the drivway. The bags are getting old to the point of replacement. I'm going to get a set of superior helper springs, cut the airbags in half and slip the helper springs over the old air bags. I heard that give it some extra lift and a lot cheaper than airbag replacement or adding leaf springs.

Google ZUK MOD

Its what your talking about

[Gary_M]

Google ZUK MOD

Its what your talking about

Yes very similar to the zuk mod. Though no torches, just a hacksaw to cut the airbag in half. These are the springs I plan on getting.

http://www.amazon.com/Superior-12-1600-Design-Helper-Capacity/dp/B000CPAVZC/ref=sr_1_5?ie=UTF8&qid=1379040527&sr=8-5&keywords=superior+helper+springs

[Skydancer2992]

Reading about the Zuk mod on the Yotatech forum is the reason I thought I'd try out the coil springs. I used cheapor Harbor Freight tin snips to cut the airbags in half. The springs slipped right over the bag ends (I had already lifted the camper up by the frame for replacing the spring bushings). As the camper was lowered, the springs snugged up over the bag ends.

I paid $25 for the SUperior helper springs on Amazon. The 1500# ones were on clearance. The Yotatech guys go to junk yards and buy Jeep springs, which would be somewhat stiffer.

Have driven about 4000 miles on them. The main difference I notice is that the camper leans more with the coil springs than the air bags. I suspect this is because the springs have a constant coefficient whereas the airbags are probably logarithmic.

I have a new airbag kit but I wanted to try out the simpler and cheaper solution first.

[linda s]

Timbrens are another option for more lift there. Usually a little cheaper than air bags and they can't deflate. I have heard from a couple of people who used them and they thought the ride was less bouncy than air bags and decreased the lean noticably.

Linda S

[Derek up North]

Springs are springs and not really designed (or capable) of much in the way of damping the oscillations. That's the job of the shock absorbers (or DAMPERS, as the Brits call them). They also do a pretty poor job of controlling 'sway'. So, springs to spring, dampers to dampen and sway bars to control sway! IMHO, of course.

[snail powered]

Timbrens are another option for more lift there. Usually a little cheaper than air bags and they can't deflate. I have heard from a couple of people who used them and they thought the ride was less bouncy than air bags and decreased the lean noticably.

Linda S

I had never hear of Timbrens before. Interesting product, essentially a big rubber bumper that is not attached at the bottom. Who knew? Shaped a bit like an air bag but not adustable. Seems to be an interesting option if you tend to have a load in a reasonably consistent weight range which would be typical for me. Would certainly save having to frequently check the air pressure levels.

I will have to keep them in mind if putting new shocks and upgrading and replacing other suspension on my rig does not help. Right now it sways like a fashion model walking down the runway.

[Derek up North]

Right now it sways like a fashion model walking down the runway.

Got a sway bar installed? Shocks in good shape? Stiffening springs could control it at the expense of becoming (literally) a pain in the butt!

Using blocks of rubber as the springing medium isn't too new. Consider the original Mini and the Moulton bicycle.

[zero]

Doesn't sound too promising according to what Timbren says . . .

"Timbren SES kits are not designed to decrease sag on an already poor suspension"

"Kits are not designed to increase weight-carrying capacity of vehicle"

"Kits are intended to assist suspension in good working order"

At least the Firestone Ride-Rites are intended for full time HD use and leveling.

[zero]

Air Lift sells air-springs for Toyotas with a sort of "Timbren" already inside of it. Best of both designs. You get the full time use of an adjustable air-spring along with a solid rubber spring incorporated inside of it for when you bottom out. This allows them to be used with low or no air if wanted - unlike Firestone Ride-Rites. Looks like a great setup other then the over $300 price-tag.

On the subject of adding a few leafs to the existing spring packs to increase ride-height . . . the 2.36" wide leafs are not common. You need to find them (or buy new) for a Toyota Tundra, T100, Mazda truck, etc.

[linda s]

Well if you got this pic from SD truck springs they have an awful lot of discounts on this. by the time you add all the discounts, if they will apply them all, it comes in at around $260. Not bad for someone who needs a replacement kit. Inside bumper looks neat. No minimum pressure needed so if a rock takes out your air lines you can get somewhere safely without trashing your bags. I haven't seen these before

http://www.sdtrucksprings.com/index.php?main_page=product_info&products_id=19781&currency=USD&gclid=CJKq-fSJy7kCFap7QgodskgAqw

Linda S

[zero]

Well if you got this pic from SD truck springs they have an awful lot of discounts on this. by the time you add all the discounts, if they will apply them all, it comes in at around $260. Not bad for someone who needs a replacement kit. Inside bumper looks neat. No minimum pressure needed so if a rock takes out your air lines you can get somewhere safely without trashing your bags. I haven't seen these before

http://www.sdtrucksprings.com/index.php?main_page=product_info&products_id=19781&currency=USD&gclid=CJKq-fSJy7kCFap7QgodskgAqw

Linda S

The photo I posted came straight out of the Air-Lift factory installation manual for the 5000 series. Same photo is posted all over from whoever is a dealer selling the stuff. In today's world - $260 is a pretty good price. I might be tempted to buy some myself for my MiniCruiser. We'll be using it on a lot of rural dirt roads with deep potholes and I'd like the option of adding air and getting more ground clearance when needed.

[Bob C]

I have been trying to find someone that can order new spring packs for the rear of my RV. All three shops in Madison, WI
say that they can't get them for me. I also tried to contact three spring shops that I knew about and all three have gone out of business.

I will just keep on checking my ride-rite airbags until I find my new springs. They lifted the axle about 3" and the ride is greatly improved.

[snail powered]

I have been trying to find someone that can order new spring packs for the rear of my RV. All three shops in Madison, WI

say that they can't get them for me. I also tried to contact three spring shops that I knew about and all three have gone out of business.

I will just keep on checking my ride-rite airbags until I find my new springs. They lifted the axle about 3" and the ride is greatly improved.

http://www.truckspring.com/suspension-parts/replacement-leaf-springs.aspx

[Bob C]

I will be contacting them soon to see if they can get me some springs rated for carrying a 6,000 RV. The one place that said he could get me springs said that he could not get them rated that high. I gave him the weight for front and rear axles and the total weight. Stock Toyota pick-up springs are not rated high enough. I had one parts place tell me that he never heard of a 1987 one ton Toyota.

[zero]

I will be contacting them soon to see if they can get me some springs rated for carrying a 6,000 RV. The one place that said he could get me springs said that he could not get them rated that high. I gave him the weight for front and rear axles and the total weight. Stock Toyota pick-up springs are not rated high enough. I had one parts place tell me that he never heard of a 1987 one ton Toyota.

I've posted the numbers and diagrams for Toyota 1 ton springs several times.

Toyota part # 48210-35660 and aftermarket # 90-205 for the 1 ton Toyota "cab and chassis" as was used by RV companies in the 80s-90s.

http://www.truckspring.com/products/Toyota-Pickup-Replacement-Leaf-Spring-(5-Leaves--Rear)__90-205.aspx

Just keep in mind that Toyota 1 ton springs are two-stage and were made for part-time loads of 5000-6000 lbs. and sit on their "second stage" while doing it.

Unlike a Toyota 1 ton box-truck that is not always loaded - Toyota RVs are full loaded ALL the time. With new spring packs, I would add at least one extra leaf per side.

[Derek up North]

... allows them to be used with low or no air if wanted - unlike Firestone Ride-Rites. Looks like a great setup other then the over $300 price-tag.

Nay, nay. The Installation Guide says not to operate them with less than 20psig (Minimum recommended pressure, pg 8) as well as "... air adjustability from 5-100 PSI" (pg 2). So you'd better not count on them going undamaged with no air.

http://www.airliftcompany.com/content/manuals/MN-856_88113.pdf

[linda s]

Weird cause in the main description it says several times can be safely run with no pressure.

Linda S

[zero]

If you read though it all - it looks like they are saying you can safely run with no air as long as the air-springs are being used as over-load helpers and not a full-time remedy to get more ride-height. I.e., if you have adequate springs in the RV and the air-springs are put in for those times you load it even heavier- you can run empty when in "normal" use mode. Clear as mud I guess.

[Astas]

I cannot find anywhere a new leaf spring pack for 1875-1978 Toyota Pickup. Everybody sells leaf springs starting with 1979 models. Did anybody have any luck with these? Do leaf springs from other vehicles fit 1978 Toyota 1/2 ton pickup chassis for my Toyota Chinook Newport? Please help.

[MontanaChinook]

Didn't you already ask about this in another thread?

At some point you need to just measure your springs and compare. When you're dealing with trucks this old, there are a lot of things that won't just be handed to you. You're going to need to do some work and find what fits.