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Well, I see a wheel that's listed as 5" wide with 3" backspace. Just looking at those numbers, you'd have an offset (positive) of 1/2" (12.5mm). It's only further down that it shows an offset of 0.00. You can't have it both ways. Better get on the phone to them.

I don't know one way or another if the taper on the Toyota nuts is 60 degrees or not, but it's important that they be the same as the wheel.

That wheel's 5" wide. I think the factory ones might be 5'5".

Why not just pick up a pair of genuine Toyota rims from the junkyard?

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Well, I see a wheel that's listed as 5" wide with 3" backspace. Just looking at those numbers, you'd have an offset (positive) of 1/2" (12.5mm). It's only further down that it shows an offset of 0.00. You can't have it both ways. Better get on the phone to them.

I don't know one way or another if the taper on the Toyota nuts is 60 degrees or not, but it's important that they be the same as the wheel.

That wheel's 5" wide. I think the factory ones might be 5'5".

Why not just pick up a pair of genuine Toyota rims from the junkyard?

The factory rims are 5" wide on a 1978 Chinook. The 185R-14" D tires are made to be mounted on a 5" to 7" wide rim.

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So if I'm looking to have my tires set slightly wider than stock, I'm looking for a NEGATIVE offset. Correct?

Or say with these...since their offset is zero, they would stick out slightly farther than stock?

http://www.summitracing.com/parts/wvi-12-451203/overview/

Most of the wheels I've been seeing have positive offsets.

I'm getting lost in all this. The stock wheels that come on a 1978 Toyota truck are 5" wide, have around 35 mm positive offset, and a backspace around 4". If you stick with a 5" wide wheel but choose less backspace then that 4" - the wheel and tire gets further out from the center-line of truck - i.e. the distance between the two front wheels become increased (wider track). If you want stock wheels - how come you don't just order the OEM stock 5" wheels for $35 I posted a link to?

I have to admit that this "backspace" and "offset" thing constantly hurts my brain. If you want, I can measure a stock 14" rim from a 1978 Toyota tomorrow and give you exact measurements. I've got some scribbled notes here from when I measured quick awhile ago and the backspace was around 4" (give or take a half inch). That is the distance from the mounting flange where the lug nuts are - to the inside edge of the rim. The measurement of the same mounting flange to the center of the 5" wide rim is the "offset" which is a different way to measure.

And again - unless I'm getting senile - "positive" offset makes the overall track less wide. "Negative" offset makes the two front wheels further away from each other and a wider track.

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Well, like I said, I think, and please correct me if I'm wrong, that being wider in the back would be a GOOD thing. No? I'm not replacing the front rims. They're the stock rims and they're fine.

I'm replacing the rear rims, because what's on there now will only fit a super wide passenger tire.

I've ordered d rated tires in 185/R14. Because I don't have a dually, but I do have the bigger Newport Chinook, I feel like any little bit of extra width in the back would be good. Is that incorrect?

So I'm ready and willing to go with those stock wheels you posted, but if I'm finally understanding offset and back spacing correctly (which I'm not sure is true...), then maybe I can find something that'll make my rear wheelbase a little wider than stock, and provide just a bit of extra stability.

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I'm replacing the rear rims, because what's on there now will only fit a super wide passenger tire.

I've ordered d rated tires in 185/R14. Because I don't have a dually, but I do have the bigger Newport Chinook, I feel like any little bit of extra width in the back would be good. Is that incorrect?

So I'm ready and willing to go with those stock wheels you posted, but if I'm finally understanding offset and back spacing correctly (which I'm not sure is true...), then maybe I can find something that'll make my rear wheelbase a little wider than stock, and provide just a bit of extra stability.

Here's a chart I made with every possible measurement I can think of for the stock 14", 5" wide rim that came on the 1/2 ton two-wheel-drive trucks. I did it with an OEM rim from a 1978 Chinook.

As to more width in back is better? Why? Toyota already designed your truck with stock wheels to be two inches wider in back then in front. Seems they felt it was best. I cannot think of a reason to change it and make it even wider.

post-6578-0-41790500-1360694037_thumb.jp

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Alright.

Why? For the reasons i stated. Theres a giant camper attached to my truck. Its not a stock situation. I feel like this would be like telling a Dolphin owner they dont need duallies, "why would they?" "Toyota designed the single rear wheels the way they are". Ive framed this every way i can come up with, each time saying "to me, having a wider wheelbase in the back seems like it would provide stability, since i have a big wide camper back there. if that reasoning is not right, please tell me!!!" I understand you and everyone else are going out of their way to help me and I really appreciate it. It's just that I've laid out very clear, basic assumptions I'm making, over and over, asking to be corrected if my assumptions are wrong. I've never heard that they're right or wrong...just more info that is good to know, but isn't addressing some of my most clearly stated questions and assumptions.

We could have ended this thread days ago if someone could tell me: Is my assumption that wider is better in the back, since we aren't talking about a stock 2wd Toyota, we're talking about an overloaded, oversized camper on a little 2wd frame, right or wrong? If there's no reason to be looking for a wider stance, then absolutely those stock rims you were nice enough to find are perfect, and if I had heard this in relation to my questions of "is it a correct assumption that wider=more stability, and is something I should go for, or not?" I would have the rims by now.

I guess I've just been in enough situations where someone tells me something, over and over, but they aren't taking everything into account...no matter how many times I bring up what they aren't including, I get the same response, with no acknowledgement that they're hearing the whole question...and if I listen to them...sometimes they're right, but sometimes they really were wrong.

So the reason I'm still bugging you is that I guess I would like, PLEASE, an answer acknowledging the one point of my concerns:

This is not a stock Toyota. It's got a camper on it. Does this NOT make a wider rear stance make sense? Is this assumption wrong? It seems to me Toyota did NOT build these trucks expecting this much bulk and weight in them their entire lives.

If its wrong, I'm buying those stock rims. If its not a wrong assumption, I'll deal with summit or someone like them on getting a more negatively offset rim than stock. And we can put this thread to bed.

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Sorry I'm getting a little frustrated with the situation. I didn't expect this part of my project to be any trouble, and I don't feel like it even needs to be...I've just been buried under a gigantic pile of information, without having some very basic, direct questions answered.

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Repeating what I wrote in Post #9:-

"I'm not in a position to say if the handling will be better or not. Probably a question better asked to the Chinook Group. Maybe someone there has tried both."

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I'm just going to go on what, after doing more Internet searching, seems to be the consensus over the years: wider tires/wheels gives more stability, at the expense of more wear on bearings and axles.

So within reason, going with wheels with less positive offset than stock would be an improvement in stability.

No matter what wheels I get for the back, they're going to way more narrow and tucked in than what's on there now.

Thanks everyone, for all the help!

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This is not a stock Toyota. It's got a camper on it. Does this NOT make a wider rear stance make sense? Is this assumption wrong? It seems to me Toyota did NOT build these trucks expecting this much bulk and weight in them their entire lives.

None of the Toyotas were designed to handle RV loads and the GVW ratings they have. In the case of a Chinook - no it was not designed by Toyota but it WAS designed by the Chinook people. By the last year of production in 1978, the Chinook and chassis it sits on got many changes and updates. A wider track in the back was not one of them that I've seen . . in life or in the literature.

I guess I cannot answer your question except I spoken to many people who have owned stock Chinooks and bigger 21 foot high-roof models like the Winnies and Sunraders. All have said the Chinooks handled better. But yeah, they are lighter and have less wind-drag. Chinooks are also on Toyota trucks with narrow frames and coil springs in front, whereas later RVs are on Toyota frames that are wider and have torsion-bar fronts. So comparing is difficult. Newer truck are wider front and back - but the rear is still only 2" wider then the front - just like the older trucks.

Toyota DID design HD 1 ton dually trucks. I have one here. The rear is only 2" wider then the front, just like the 1/2 ton trucks of all years - but it has dualies. So, not a perfect comparison.

In the case of handling-and-suspension 101 - I can't think of anything that makes a rear wider then the front as an improvement. Changing the front track in relation to the rear can affect "understeer" or "oversteer" if the vehicle has a inherent problem. Nothing else that I've ever read about. Other fundementals of handling yes . . e.g. with 4WD the front wheels need to be slightly faster then the rear for good handling, . . or on any truck the front wheels should be slightly "pigeon toed" in front (called "toe in) . . or for steering that does not burn up tires there must be an Ackerman angle whenever turning, etc.

If people had been reporting "understeer" or "oversteer" problems with Chinooks , the idea of changing widths would make more sense (to me). I've never heard that.

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Alright, thanks. I think probably I'm just looking for easier answers...for some reason I thought it would be a more clearcut issue. I do appreciate all the help. I ordered these http://www.summitracing.com/parts/wvi-38-4612334/overview/ A slightly more expensive route, but not too bad. Still within my "tax return" budget. :)

Just 1" wider than stock, still within the 185/R14 tire suggested range of 5-6" wheels, and a positive offset of 6mm, only 6mm less than stock. So I feel like it's not straying far from stock, while making me feel a little better than I'm slightly wider (but way skinnier than what's on there now, so an improvement as far as load on the axle compared to what it's had) than stock.

**I know we've been over this, and it mostly has to do with the type of tires available back then, but for my model Chinook, they did put on wider tires. My Chinook door tag called for L60x14 tire on 14x8 rims. The tires I bought are different, but definitely more narrow. So I think it's an ok compromise to go with 1" wider rims, with a little more width to the outside of the vehicle. Remember, this 1978 Newport is not the apex of Chinookery. My model is a "one-year-only" Chinook, much bigger and bulkier than your Chinook and all that came before it. On a 1978 pop-top I would completely agree with you.**

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**I know we've been over this, and it mostly has to do with the type of tires available back then, but for my model Chinook, they did put on wider tires. My Chinook door tag called for L60x14 tire on 14x8 rims. The tires I bought are different, but definitely more narrow. So I think it's an ok compromise to go with 1" wider rims, with a little more width to the outside of the vehicle. Remember, this 1978 Newport is not the apex of Chinookery. My model is a "one-year-only" Chinook, much bigger and bulkier than your Chinook and all that came before it. On a 1978 pop-top I would completely agree with you.**

What does your Newport actually weigh? I suspect not an awful lot more then a pop-up roof Chinook.

As to rear width versus front - that's a way of "adjusting" for understeer or oversteer. Making your rear wider - if anything probably make it handle a little worse.

I suspect Chinook put wider tires on your's because just to get more load capacity. With modern HD single-wheel commercial vans with GVWs higher then your Chinook - e.g. the Sprinter, the rear axle is only a 1/4" wider then then the front. Most HD single wheel trucks have rears the same or slightly narrower then the front .

Sprinter 1 ton van FWD rear is 1/8" wider

Chevy 3/4 ton Suburban RWD rear is 2" narrower then front

Chevy C30 and K30 1 ton RWD trucks - rear is 3" narrower then front

Chevy 3/4 ton cargo van RWD rear and front the same

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Well then i did good going with skinnier tires and rims than Chinook called for, and skinnier tires and rims than what are on there now. So more than likely ill see an improvement in handling. The rims are 2" more narrow than Chinooks recommended size, and the tires are definitely more narrow.

I'm not sure what I actually weigh.

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I also bought 1978 Toyota Chinook Newport in a pretty bad shape and am restoring it. I was wondering where did you buy the front axle springs for the shocks since I can't seem to find them anywhere on the eBay.

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Yep. Go with the Rock Auto ones. Much cheaper.

As far as front shocks (not springs), I just got them from...shockwarehouse, I think? They weren't hard to find. It's the springs for the front that aren't specifically made for Toyota pickups anymore. But those Saab ones work!

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Linda,

Thank you very much for the link to the thread.

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On another note, for the rear tires on my Chinook Newport one of my mechanic friends suggested to go with 31/10.50/15 tires with 109 Q speed rating, 2,190 lbs load capacity, Load Type C, 50Psi max pressure, all terrain 6ply walls.

Has anybody in the Toyota Motorhome community ever used these on their rigs? If yes, I would like to know how well they handle and how they performed on different types of terrain. Thank you!

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http://www.walmart.com/ip/Hankook-Radial-RA08-Tire-185R14-8/17792669

this tire is available from other sources too. Wally's world charged about $20 per tire to (lifetime) mount/balance road hazard. Some walmarts will not lift a camper but some will. I jacked mine up outside the door & gave them wheel axle by axle. Tighten lugs with a cheater bar (piece of pipe over ratchet) , also used anti-seize on lug nuts.

Do you know about tire dates? If you buy them from small shops it is something to discuss. Most any tire dealers can get hankooks.

Goodyear used to make wrangler RT's - cost more but good tires.

Don t know the specs on your wheels/ tires/ my camper is winnie warrior & spec-ed 6 ply (load range C) and the hankooks (likemost similar tires) will be load range d which corresponds to the old 8 ply designation.

You do not want to put car tires on it - no matter if they are about the same size/

btw, my camper is listed as 6000 maxweight - 5300 empty - we might be a "wee bit" overweight on longer trips....

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On another note, for the rear tires on my Chinook Newport one of my mechanic friends suggested to go with 31/10.50/15 tires with 109 Q speed rating, 2,190 lbs load capacity, Load Type C, 50Psi max pressure, all terrain 6ply walls. Has anybody in the Toyota Motorhome community ever used these on their rigs? If yes, I would like to know how well they handle and how they performed on different types of terrain. Thank you!

You'll need to compare that to what the stock size is.

I cannot imagine that on my Newport, 31s would fit without a lift. But I didn't try it...so I can't say for sure. See what size is on it now, see how the 31s compare, and measure. Taking into account some flexing.

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Yeah I know 4x4s are kind of dogs with 31s on them. They aren't geared for it. The biggest you can go without feeling a real noticeable effect is 30x9.50. Once you go to 31x10.5...you don't have to regear, but really should. You'll really notice it on hills.

Stock for 4x4s is 225 75 R15, I think.

30x9.50 = 235 75 R15. So 31s are even bigger still.

Stock for 2wd is 185 R14.

I know a guy on the Yahoo Chinook site has 30x9.50s on his 2wd Chinook. He has two extra leaf springs on each side in the back, and longer shocks.

So I'm guessing you'll need a lift to get 31s to fit.

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Did you ever consider putting 31/10.50/15 size tires on the rear axle ? They have an all terrain load C rating 2090 lbs 6 ply and 50 PSI max pressure. One of my mechanic friends suggested to me that I do it for my Newport. I am contemplating on using 185R14 in the front and 31/10.50/15 in the rear to maintain a proper height and weight distribution on the front and the rear.

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If you rear is sagging and needs ~3" of lift (which is what this tire size will give you), I'd suggest you have your rear springs replaced/repaired/beefed up. Bigger tires might raise the rear but it won't fix worn out springs! :)

P.S. Parking on a hill will level things just as effectively and is a lot cheaper. But your springs will still be worn out.

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Did you ever consider putting 31/10.50/15 size tires on the rear axle ? They have an all terrain load C rating 2090 lbs 6 ply and 50 PSI max pressure. One of my mechanic friends suggested to me that I do it for my Newport. I am contemplating on using 185R14 in the front and 31/10.50/15 in the rear to maintain a proper height and weight distribution on the front and the rear.

Deja Vu!

Make sure they fit...

I don't get what you're trying to do. Are you trying to give your Chinook a slant? Rear higher than the front, so more weight is shifted forward? They were never built to sit that way...

The right way to raise up the rear to stock height is with the leaf springs and shocks, not larger tires. Especially if your rear springs are sagging, no way you're going to fit larger-than-stock tires back there.

But again...measure to make sure. Who knows.

But I really wouldn't suggest trying to regain lost height by putting on bigger tires. That's just not the way to do it.

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The way my Chinook Newport sits now is it has it's nose up in the air and the rear is very low to the ground. Additionally, my mechanic welded on a steel platform in the rear and placed an aluminum tool box on it with an Onan 4000 generator that weighs about 200 lbs. Moreover, whoever owned it before me have installed a heavy air conditioning unit on the roof 13,000 BTU that made a sag in the roof because it did not have any support beams. And to add to these trouble issues, my Chinook' s leaf springs and shocks are sitting very low. I have not measured the 31/10.05/15 tire size next to my RV but they looked very wide and had good depth of thread that I did not see on any 185/R14 tires. I can use a 3" lift on my RV but judging by some other threads neither rearching the old leafs nor add-a-leafs will give me a lasting result. The Zuk mod looks weird and unstable for this type of vehicle. My only other option is to install additional air bag suspension stabilizers, new shocks, new springs and new spring leaf packs. However, I do not know if they even make new spring leaf packs for Toyota 1978 Pickups.

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You can buy new leaf spring packs.

I've found them...I'll look around. Can't remember where right now.

You need to get rid of some weight, or put a one ton axle in the back. Seriously. You're about to loose a tire next time you drive down the road. That's way overloaded.

And bigger tires isn't even a bandaid at this point...it's just worthless.

You need to:

A. Drop weight.

B. Replace your rear axle bearings.

C. Replace your rear shocks.

D. Either add two add-a-leafs, or get a new spring pack and put an add-a-leaf in those before installing.

Seriously.

Then do what you want as far as oversize, power-robbing tires. But stock will do you fine once your suspension is fixed and your extra weight is gone.

You have tons of extra weight at the very weakest point of your Chinook. Hanging off the very end of the already sketchy frame extension. Lever action working on an already questionable joint.

Yikes.

If you're looking for 4wd tread on a 2wd tire...yeah, you're gonna be disappointed with the treads on all 185 R14 tires. Just remember you've got a 2wd truck. If you want 4wd performance, do all the above a-d, plus another add a leaf, longer rear shocks and a rear locker. Then you can fit 30x9.50 tires with agressive tread, and go offroad.

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Not sure how much changed between 78 and 79...might want to measure and call them.

http://www.generalspringkc.com/product_p/90-113.htm

I find plenty of 79 leaf spring packs online, so it's worth looking into. I know JDemarris said you could buy new spring packs for these, and he was a guy who knew how to measure and find stuff that fit, even when it didn't say it did. Like the Saab springs that fit perfectly in my front suspension. No one sells springs for the front of pre-79 trucks. But the Saab rear springs are a perfect fit.

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My thinking is inline with Zach's.

Zach might want to start worrying! :)

I'd suggest you load it up as you expect it to be when you're using it and then get it weighed (front axle/rear axle) so that you know what sort of weight you're dealing with. Remember that each 185R14 LR D is rated for 1875lb @ 65psi. I would hope you're NOT having 3700lb on the rear axle alone.

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I absolutely agree that there is way too much weight in the rear of my Chinook. I am planning on removing the rooftop A/C altogether and installing a small 7000BTU standing A/C in the closet at the rear of the RV. I am also planning to remove that huge generator and place in that box 35lb Ryobi 2200 watt generator or a Honda 2000. I am also remaining a portapotty nitch into a small shower stall with portapotty fitting inside of it. That way, I figured that I will be able to loose at least 350lbs in the rear prior to changing the suspension. I had a terrible side to side sway when I took this RV on its maiden trip from South Carolina to Alabama. Besides, I was towing a 1500 lb Honda Civic 2door hatchback behind it. My max speeds were 35 miles per hour up the hill and 50 down the hill with a terrible sway. I almost got into 5 accidents and almost lost my brakes once and did lose all of my lights twice. So, as you imagine, it was not a nice trip. Having said this, I want to do everything that I can to make it a safe and dependable Motorhome.

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First off, stop towing with it :)

Mine also had bad side to side sway. An add a leaf in the back and new shocks and springs all around took care of it. I'd like a rear sway bar but haven't done that yet.

So just keep in mind that with no extra weight from AC or a generator, which didn't come stock with your Chinook, it's already loaded to the max of its capacity.

But yeah, I'd say replace and add a leaf to the rear springs, and replace the front and rear shocks and front springs. And yeah, wait until you get rid of all that weight to do it.

It's expensive so it's better if you can do it yourself...but since yours has been so overloaded for so long, I'd really look into replacing the axle bearings.

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