Some advice on a Chevy Suspension Upgrade

[Hondo]

It depends on the tires that you are using. I cannot imagine Roadtrek or any mfg selling an RV with tires not capable of operating the RV at the maximum certified weight.

I use BFG T/A KO2 radials and they can handle the stock (and extra) load with ease. Tires have to be researched for load capacity and chosen (like Booster said) to handle the load (and then some).

[booster]

Originally Posted by Hondo

It depends on the tires that you are using. I cannot imagine Roadtrek or any mfg selling an RV with tires not capable of operating the RV at the maximum certified weight.

I use BFG T/A KO2 radials and they can handle the stock (and extra) load with ease. Tires have to be researched for load capacity and chosen (like Booster said) to handle the load (and then some).

Nobody would be able to sell a vehicle with tires that aren't up to the rated load of the vehicle, but some other things also get into it. One is that the rated weight should really be by wheel not by axle or by total vehicle weight. We do get axle weight ratings, but not tire weights. As I just mentioned in another discussion, Roadtrek Chevies tend to run heavy (2-300#) on the right rear, so you can be overloaded on one rear tire, under on the other tire and still be within axle rating.


The other main point would be if it is a good idea to have some "safety factor" cushion in tire loading. You hear fairly often recommendations of no more than 75% and 90% of maximum load rating, especially if the vehicle is loaded to the heavy load all the time. I have never heard of any real testing to prove that there are less tire failures at either reduction, but it does make sense, especially in tall, always heavy, vehicles especially in hot weather. Personally, I do like to have some extra space from the rating if I can get it, and more will never be a bad thing. Tire temperatures will tell you a lot, as will the temperature related pressure changes in the tires.


For reference here are the per tire rating of 3 of the mentioned tires:


OEM Bridgestone 245-75-16 3042#


Michelin Defender 265-75-16 3415# so 373# or 12.% more capacity


BFG T/A KO2 265-70-17 3195# so 153# or 5% more capacity


All of these appear to have very good reliability and reputation.



Particularly vans like the Roadtrek 210 and the 2500 Sprinter seem to have quite a few overweight vans on the road. Getting corner weights, especially for a 210 Roadtrek rear is a good idea IMO, as most of the weighings we have seen for them are very near or over for rear axle weight, and if they have the 2-300# misbalance on the rear, they will be quite far over on the right side.

[Hondo]

Totally agree Booster, spot on.


I've weighed my rig 3 times to see where I am at and I haven't exceeded either axle limit for a stock van....I have about 750 lbs of payload not including fuel. I know that some of the weight is below frame with heavier leaf springs, Dana 70 axle, wheels and tires and the rear sway bar, I'd bet that's 300 lbs right there.

Add in the 320 lbs to the front half of the rig for the 4x4 conversion, some of that's above frame weight. The entire front end is now 3500 truck torsion bar suspension.

The tires I'm running do have the capacity but like I talked about in the other thread I'm probably going to go to an 18 inch wheel & tire combo because I can get a wheel with 18-20mm of offset and the BFG tires rated to 3,640 lbs (275/70R18, p/n 45062), just shy of 500 lbs extra load capacity per tire, this all for the sake of safety and reliability.

Also, for those that might be wondering how to deal with different sized tires, I use the Bully Dog GT to change the tire size in the computer so that the odometer and speedometer are correct. I believe that Booster can do the same thing with his laptop and computer program.

[booster]

Yikes, those are 33.2" diameter compared to 30.5" for the stock tire and about 31.6" for the 265-75-16 like we have. No way would we have room for another3/4"+ all the way around, as we would be into the grey tank an fender, I think.

[cruising7388]

Originally Posted by Hondo

The tires I'm running do have the capacity but like I talked about in the other thread I'm probably going to go to an 18 inch wheel & tire combo because I can get a wheel with 18-20mm of offset and the BFG tires rated to 3,640 lbs (275/70R18, p/n 45062), just shy of 500 lbs extra load capacity per tire, this all for the sake of safety and reliability.

I don't think you can pull that off without some butchering. We tried 18 inch rims on our 210 and the fronts rubbed the spoiler.

[Hondo]

If you look at my build thread you will see that I did a bit of trimming when I was using the 0mm offset wheels....

The wheel size doesn't matter. What matters is the tire size and the wheel offset together. The senior tech at Advanced 4 Wheel Drive in Salt Lake is running 20s on his lifted 4X4 express van, 275s I think.

Here are a few pics that I just took of the 275/70R-17s on the 28mm offset Chevrolet wheels, lots of clearance -







About 1 1/4 inch clearance between the wheel well and the tire edge - at the tightest point, fully turned -



Going to a larger 275/70R-18 tire (p/n 45062, 3,640 lbs) will increase the overall diameter of the tire from 32.2' to 33.2 inches, reducing clearance by .5 inch with these wheels. Buying a new 18 inch wheel will mean getting one with either 18 or 20mm of offset, a reduction of 8-10 mm. This will move the wheel outward that little bit but eyeballing it I don't think that it will make a difference.

But what if it does, what then?

A slightly smaller 18' tire that will fit on the new wheels.

That's where my tire dealer comes in - Discount Tire. If they don't fit they will order the other size or maybe preorder both sets.

The 1st alternative tire is the 265/70R18 p/n 40855, rated at 3525 lbs and a diameter of of 32.6, just .4 inches larger than the current 17s (ie .2 inches less room per side of the tire) and provide 410lbs more capacity per tire/820 lbs per axle than the 17s. This may be my go to tire in the beginning but I'd sure like the larger tires...

The 2nd alternative 18 inch tire is the BFG KO2 p/n 19463, a 275/65R-18 load rated at 3415 lbs and .1 inches smaller. That is 225 lbs less than the larger tire but 220 lbs more than the 17' tires currently being used...this will then further increase the tire load capacity over the 17s by 440 lbs per axle instead of the 890 lbs offered by the bigger 18's.

Lots of stuff to think about, I've been looking at the tire issue since the lift began. The thing to remember is that my 4X4 210 is lifted about 4 inches over stock and my experience will be different than most owners.

[Hondo]

Just went out and looked again at the wheelwells and tanks & such...looks like about 1-1.5 inches of clearance between lowest edge the body frame mount and the tire with the wheel cranked -








That steel plate is about 1-2 inches from the tank on each side and look like they could safely be set back a bit to make more room if necessary.

[bwolfsohn]

someone mentioned the continental tire kit earlier in this thread... How does this affect the "larger wheel" larger tire" issue ??

btw, great info all around... thanks guys...

[booster]

Originally Posted by bwolfsohn

someone mentioned the continental tire kit earlier in this thread... How does this affect the "larger wheel" larger tire" issue ??

btw, great info all around... thanks guys...

Any wheel and tire bigger than stock will not fit the Roadtrek tire carrier, so you either have carry the odd size spare, as we do, or modify/replace the tire carrier with one that will fit the new size.

[Hondo]

Originally Posted by booster

Any wheel and tire bigger than stock will not fit the Roadtrek tire carrier, so you either have carry the odd size spare, as we do, or modify/replace the tire carrier with one that will fit the new size.

That's my plan...cutting, welding, modding the stock carrier to accommodate the larger spare.

[cruising7388]

Originally Posted by booster

Any wheel and tire bigger than stock will not fit the Roadtrek tire carrier, so you either have carry the odd size spare, as we do, or modify/replace the tire carrier with one that will fit the new size.

I think you're right that a bigger diameter wheel or larger tire will make the RT tire carrier totally unusable.

Even if you stick with 16 inch rims, there are complications because the carrier is designed for the factory steel wheels. If you don't choose the AR aluminum wheel option, you're in good shape. Any of your five tires will fit properly. But if you order aluminum wheels, you still get a steel wheel with the factory offset for the spare. Consequently, when replacing a bad aluminum rim tire with the steel spare, while the dead soldier may fit into the spare carrier, because of the different rim offset you can't put the carrier rear fiberglass cover back on.

The additional consequence is that you end up with the spare steel wheel with +28 mm offset on one side of the coach with an aluminum wheel with a -6 mm offset on the other side.

[booster]

Originally Posted by cruising7388

I think you're right that a bigger diameter wheel or larger tire will make the RT tire carrier totally unusable.

Even if you stick with 16 inch rims, there are complications because the carrier is designed for the factory steel wheels. If you don't choose the AR aluminum wheel option, you're in good shape. Any of your five tires will fit properly. But if you order aluminum wheels, you still get a steel wheel with the factory offset for the spare. Consequently, when replacing a bad aluminum rim tire with the steel spare, while the dead soldier may fit into the spare carrier, because of the different rim offset you can't put the carrier rear fiberglass cover back on.

The additional consequence is that you end up with the spare steel wheel with +28 mm offset on one side of the coach with an aluminum wheel with a -6 mm offset on the other side.

Part of it is how you define usable on the tire carrier, I think. If the wheels are the right offset, there is a likelyhood they will mount to the carrier OK unless the tires are wider and hit the support. Similarly, any wider tires won't fit inside the fiberglass cover and band. Same thing if they are larger diameter tires.


Aluminum or any other wrong offset wheels would need the carrier to be cut and rewelded, I think. The AR aluminum wheels do not fit the carrier, and the factory provides a steel wheel spare.



Actually driving the vehicle with the mismatched wheels and tires would be possible, but not ideal. If there is any diameter difference, you would need have that in the front to prevent having a lockup axle lock, if you have one, or standard axle to overheat from the different axle speeds. On the front, you might feel the difference if it is offset, but less likely to feel diameter, I think. By any thought, you would need to get the tire replaced as quickly as possible so back to matching.

[Hondo]

I ordered 5 wheels & tires to avoid the mismatch on my 210.

The spare tire carrier may require modification to hold the 18mm offset wheel but I really won't know until I try to fit it. It may be possible to simply add an inexpensive aluminum wheel spacer to the mount.

The 10mm/.4 inches offset difference hopefully won't be an issue.

[Hondo]

Found these 1/4 inch aluminum wheel spacers on ebay for $10.75 shipped...

https://www.ebay.com/itm/2X-8-LUG-WH...xVN0QS&vxp=mtr

Maybe need one or both, I'm ordering a set.

[booster]

Originally Posted by Hondo

Found these 1/4 inch aluminum wheel spacers on ebay for $10.75 shipped...

https://www.ebay.com/itm/2X-8-LUG-WH...xVN0QS&vxp=mtr

Maybe need one or both, I'm ordering a set.

Unless I am missing something, spacers on the hub to wheel surfaces is going to take the offset to the negative direction, thus reducing the positive offset that you are looking to increase, to the stock 28mm.



I you want to spacer back to 280mm, you probably would only be able to find the newer +44mm offset wheels to start with and it would take 16mm of spacer to get to 28mm, which is quite a bit, but not crazy big.

[Hondo]

The spacers will be used for just the spare tire carrier, not the rolling wheels.

Even then it might not work as the spacer will mover the spare tire closer to the rear door. Modification to the carrier itself may be required down in the receiver or maybe a bigger job cutting and welding the carrier to mount the tire opposite from stock. (rearward facing)

I don't think the 18 mm offset wheels will be an issue on the 210.

[Deano]

When I changed to the 265/75X16 tires with the 7" wide GM 6 hole wheels I had to modify the spare carrier. As Booster said the tire hits the support bar and required spacing the tire forward approximately 3/4". That required using the adjustment bolt to move the bar to the rear, and that required drilling the safety pin hole out. The bar had to be ground down at the pivot to allow the tire to be low enough to clear the bottom of the door when opened. As stated, the cover will not fit either. At this time I am using a soft cover and installed a bolt through the fiberglass cover into a hole I drilled and taped in the support arm. It is working good so far. However, when I can afford it I plan to buy a complete cover/stainless ring I found at: http://www.boomco.com/hummer-tire-co...ss-steel-ring/
The cover will require modification to clear the support arm.

[cruising7388]

Originally Posted by Deano

When I changed to the 265/75X16 tires with the 7" wide GM 6 hole wheels I had to modify the spare carrier. As Booster said the tire hits the support bar and required spacing the tire forward approximately 3/4". That required using the adjustment bolt to move the bar to the rear, and that required drilling the safety pin hole out. The bar had to be ground down at the pivot to allow the tire to be low enough to clear the bottom of the door when opened. As stated, the cover will not fit either. At this time I am using a soft cover and installed a bolt through the fiberglass cover into a hole I drilled and taped in the support arm. It is working good so far. However, when I can afford it I plan to buy a complete cover/stainless ring I found at: http://www.boomco.com/hummer-tire-co...ss-steel-ring/
The cover will require modification to clear the support arm.

When you changed over to your current tires and rims, did you experience any difference in ride quality and handling on the road?

[cruising7388]

Originally Posted by booster

Unless I am missing something, spacers on the hub to wheel surfaces is going to take the offset to the negative direction, thus reducing the positive offset that you are looking to increase, to the stock 28mm.



I you want to spacer back to 280mm, you probably would only be able to find the newer +44mm offset wheels to start with and it would take 16mm of spacer to get to 28mm, which is quite a bit, but not crazy big.

This link seems to indicate that back spacing increases positive offset.

https://www.autoanything.com/wheels-...el-backspacing

[booster]

That should be correct as you state it. Less backspace moves the wheel centerline outboard, so if only the backspace changes the offset will go more to the negative side. More backspace moves the wheel centerline inboard if there are no other changes.


One thing that happens all the time is that backspacing and wheel width both change from stock on any given wheel. This changes how much, if any, the offset changes. If you make a wheel an inch wider, it will be 1/2 inch further to the inboard and outboard at the rim edge. If the wheel flange stays in the same place, the offset doesn't change, but the backspace gets 1/2 inch bigger even though the offset didn't change.


It is very common when going to wider wheels to decrease the backspace by 1/2 of the width increase so the inside edge of the wheel stays int the same place in relation to the van itself to assure the wheel or tire doesn't hit anything like the brakes or wheelwells.