Hi,

I am new member to the forum. Can the front axle weight capacity be upgraded or be increased by replacing the axle. Noticed that alot class 8 trucks have a 12,000 pound rating. Thank you.

Good question. I'll be interested to see the answers too. My rig has a 12k front axle. I scaled mine and got 11k on the front wheels. That was with almost full fuel tanks and my fat but sitting at the helm. I thought maybe only having 1k to spare might be bad. But, there really isn't any need because there isn't any way to add more weight up there. There's only one passenger seat up there and my wife is very slender. And I wouldn't think I'd put much in the front storage bins underneath because the rear bins are much bigger. I've seen some huge rigs with monster front tires on them. I think they use some sort of cement mixer front axle or something. I wonder it that would bolt onto where a 12k axle comes off? I bet it would cost a ton.

BigRig,

I had mine scaled with totally full fuel and propane. I had no water in the rear-fresh-tank and no load in the garage, both of which would reduce the front-end-load. I scaled at 12,200lbs on the front axle.

I asked the guy that did my alignment and ride height adjustments (a local specialty truck frame shop) and he said that was insignificant. And he agreed that it would not be that way when I added 100gal of fresh water and bike or 2 in the garage hanging out over the rear axles.

He said to make sure your tires are up to the load, then your wheels, then your springs. But within a 5% margin - it really isn’t much to worry about in an RV application.

That’s the conversation that I had for what its worth?

Rad

....I'M WITH YOU GUYS ON THIS ONE....I CAN NOT SEE WHERE EVEN 50% MIGHT MAKE A DIFFERENCE ON THE FRONT END-ONE SEES THAT JUST GOING AROUND A CORNER AT SPEED FROM THE LOADING AND UNLOADING OF A TURN AND THE WEIGHT SHIFTING FROM ONE SIDE TO THE OTHER.....WITH OUT SET UPS I'D THINK IT WOULD NOT BE AN ISSUE....IF ANYTHING IT MIGHT HAVE SOME SAG IN THE FRONT END-BUT TIME DOES THAT ANYWAY.....geofkaye

Well I dont know about your guys, but with time, it seems to me, everything starts to sag...up front, out back - it doesent matter what, who or where. https://www.truckhome.com/infopop/emo.../icon_wink.gif

Rad

Question on Front Axle, is springs or Air the better way to go? And, should I look for a greater capacity axle as part of my search for the perfect, well OK, satisfactory rig?

....AIR IS THE LATEST THING FOR SOME MANUFACTURES TO DO TO MAKE THE RIDE AND HANDLING BETTER....THE DOWN SIDE IS THAT IT IS JUST ANOTHER PART TO FAIL IN THE SYSTEM... I suggest you stay with a springer front end unless the ride issue is paramount to your comfort....having driven an air axle tractor and owning a springer i REALLY CAN NOT TELL THE DIFFERENCE... my truck seems to feel the bumps just like the air bags do....maybe if I was more than 23,000# tractor- with a 12,000# trailer[COMBINED TOTAL WEIGHT-35,000# with all the stuff I {could} carry if I wanted to].....but as it is....well ,unless I carry a bunch of fat girlz to a show....[which isn't going to happen] I can not see a big advantage to airbags...others might not agree-but as an extra it is something I can do without....geof kaye and the Rivercity Group[of skinny girls[-['cept me that is!]

I appreciate everyone's quick responses. Thanks

It's not just changing out a 12,000lb axle for a larger one-that's the easy part. The complicated part is will the frame take the extra stress-especially with some of the conversions with long wheelbases. Check with your truck manufacturer before you just change the front axle. TomC

Why would you wont to increase front axel lbs? DOT will not allow you to increase weight on front axle. DUE TO THE SPECS OF THE TRUCK BUILDER AND THE REGS. OF HWY USEAGE. I am a retired truck driver and I know if you change the axle and run over a hwy. scale plate the DOT officer in the scale house will come out and stop you and make you return to the scale house to be inspected and weighed. Then your problems are really going to start.

Alpharv, I would suspect that would only be an issue if you are in fact in any way commercial. If you're truly recreational the DOT inspectors and weigh stations have nothing to do with you. So putting a heavier axle on would be for the owner's personal desire. I wonder if you had an rv that was seriously overloaded and you got into an accident and the lawyers got involved might it cause more problems for an owner? Would it decrease your legal exposure if you had upfitted a higher capacity axle and not overloaded it? I don't know. I'm no lawyer. Just curious.

Have you weighed the truck? Do you think you'll have a front axle weight problem? Whenever I see at T/C motorhome with little or no rear overhang and the generator, water tanks, waste tanks, etc. are ahead of the rear axle(s), I wonder how much weight of the truck is on the front axle and if it isn't too much.

Any pilot (private on up) has to know how to make "weight and balance" calculations for an airplane to determine the center of gravity (CG) of any airplane. While I've never done it for a real truck or talked to the engineers, I presume the calculations are the same.

Simple rule of thumb ... the more stuff you put in front of the rear axle(s) and the closer the heavy stuff is to the front axle ... the more front heavy the truck will be. (But you probably had the figured out already.)

Unless you're deeply committed already to where stuff is going to be on your truck, I'd recommend trying to solve the front axle weight problem by placement of the heavy stuff rather than installing a heavier front axle.

I think if your able to shift some of your heavyest items towards the rear of your rige it might help you to litting he front end. when I end up with my front end over weight I slide my 5th wheel back.

Nice looking rig Bob I am suprized that your haveing front end issuse. I would of thougt the builder would of allowed more room for weight. are you maxed out?

I'm not having any front end issues. Is there some other Bob around here?

The high end stretch coach converters use 16k front suspensions, research shows that the larger than 12k front axles all use the same main beam part number, 16,18,20k, the spindles and bearings are probably all the same for these axles also. the brakes,hubs, wheel offset and tires are capacity related and of course the spring packs will be different.
I'm thinking that an upgraded 18 or 20k axle mounted to airide would give the necessary capacity and adjustability for increased weight without compromising the ride and ride height
Question is, is their a way to legitimatly change the build spec sheet to reflect the change, upfitters regularlt change the titles to reflect their finished products, ie; tanker,box van,reefer,motorhome semi etc.

When Showhauler built mine they warned of too much front axle weight since I wanted the generator up front. They said if I keep the 200 gallon tank of fresh water full under the bed it shouldn't be an issue. It hasn't been an issue but I found the addition of 2000# behind the axle sure make for a smoooth ride!
https://i41.tinypic.com/35i8yf9.jpg

whats your overall length? whats your length from center of rear axle to rear of car ramp? can you see ends of car out side mirrors? who built car platform?

I have a 28' conversion, the truck is rougly 10' and the car platform is 5' roughly. I've never measured from the rear axle back. I designed and built the platform. It was laser cut out of mostly 1/2" thick plate and box welded. It could probably hold 5000# safely. I didn't want to stress when on rough roads so I over bult it. The car is about 4" longer than the RV is wide so you see just about 2" in the mirrors. The 1800# car takes some of the weight off of the front axle making the ride much less harsh. I installed a air bag dump which makes loading/unloading easier.

how did you fasten platform to truck? ramps must be 5 foot? that car a two seater? any back seat or storate area? much room in drivers area of car? i like the idea of car sticking out so you can see it. so your over all lenght is about 43'?
with graphics on car do you think they will think its for business not plesure? which then you would have to follow dot rules.
not trying to start trouble. i was thinking about putting graphics on motorhome but think it maybe a problem.

It mounts like the hitch does. 8' ramps, yes about 43' long. I follow all DOT rules when driving my SMART. ;) When I drive the RV it's always for pleasure. To complicate things further, the SMART has Oklahoma tags and the RV has Montana. I'm sure you can imagine the semantics that will ensue if a rookie LEO pulls me over!

Bringing up an old thread, but we've been deep into this problem for a few months now. We bought a 1996 Volvo WIA that was converted into a 41' motor home. Sorry guess it's not a true HDT or MDt rig. We were originally told the front axle weight was 12K but after having a steer tire blow out on the first trip out we discovered the front axle weight was 14,900 with only 1/4 full fuel tanks (16K with full tanks). Volvo of North America was absolutely no help at all so we currently have a private shop installing a used 18K front axle assembly with all new components and 315/80 tires. We came to this conclusion after talking to one of the Freightliner builders who now puts 18K front axles & 315 tires under all their big 40' rigs. We also just looked at our friends brand new Volvo 45' Show Hauler with an 18K front. We were told that our current front axle capacity was actually 15.7K with a spring change but the truck just didn't feel safe after the blow out. The 315 tires by themselves may have solved the weight issue but we figured we'd try to do it right and changed the whole axle assembly. We've heard all kinds of information on the front axle beams interchangeability and a lot of it seems like mis-information at times. So again we figured the best solution was to go with a true 18K assembly. So far everything has been a bolt-in on our Volvo, including the secondary steering ram for the steering. Our only remaining issues now are the drag link and whether or not the current steering pump and reservoir will handle the load.

DeepVee - what is the axle rating on your front axle ?

Im not following how your truck isn't an HDT (class 7 or 8) ?
Our Freightliner Columbia coach has a front axle rating of 13880 - full of fuel we tip the scales at 12,460...1420 under weight. (we only have 65g of fuel PER side).

Our truck VIN states 12,300. The truck was stretched and rebuilt as a 41' motor home with the original Volvo front axle but the builder replaced the original springs with 15,700 lb rated springs. The builder stated that the 12K & 15.7K Volvo specification both used the same axle beam and that the springs are all that changed between the two different ratings. From what I've read, these trucks were heavy on the front when they were new and in our case the builder added the coach box, an 18KW generator in front of the rear wheels and a big slide-out. In addition, we can hold 300-gallons of fuel just behind the front wheels. It all starts adding up quick and we calculated a total front axle weight of 16,300 lbs when we're full of fuel. Even if the current front axle rating is 15,700 lb, it's not enough for us. Especially after we blew out a 7160 lb front tire at highway speed, and you can feel the weight in the steering. This is why we're going to a true 18K spec front.

After I uploaded the original message I saw the HDT forum title. I got the impression that the HDT classification is for an truck that still looks like a semi, without a motor home box like ours. Is this the case?

Ok given the different trucks manufacture & your fuel capacity (man id kill for that range), makes me glad our (single screw) coach has the generator POST rear axle.

have you actually WEIGHED it (rather than calculating the weight) ?

Yours sure looks like a big truck to me!

Ok, thanks, guess it qualifies then. :)

We should be ok now with the axle and tire swap but one of the other thoughts I've had is to replace our big Iszuzu generator with a smaller, possibly lighter unit that can still give us enough power.

How big is the existing (isuzu) generator ? Looks like you have at least 2 A/C units on the roof.

I wouldnt want to go any smaller than an 8kw (diesel) - assuming your electrical load beyond the immediate coach is light.

I think it's a 16kw unit. It's fairly loud when compared to an Onan.

JEEZUS what where they planning to run w/ that !?!?!

We've got an Onan QD 10kw in our coach (running 2 - 15.5k BTU Air Conditioners). The QD10k reportedly weighs 765 lbs (the QD12.5kw is 770lbs) according to their DOC

Our QD10k is rated to burn between .42 & 1 gallon per hour (the 12.5 is .48 & 1.2 per hr consumption & I swear ours burns less than i think (or worry about)....even w/ both air conditioners running it never seems to burn as much as i think it should....and we've done a fair amount of tailgating & track side camping.

Hell i can back=feed our house (including 1 of the 2 AC units) w/ 10kw....
Had to do it on tuesday as a matter of fact (lost power for 15 hrs) due to Flooding.

https://www.truckconversion.net/attac...1ce01f6c67.png

That's good to know, thanks. From what I was told the unit we have was priced pretty fairly which is why it's in our coach, something like $9K new. I'd rather have an Onan though like yours in there. Our unit is still pretty much brand new with minimal hours so I might be able to swap it out and break even at some point. I think we'd be fine with the same unit you have.

On a side note, I just talked to the shop that's doing our front axle swap. It sounds like we only have one remaining issue. The stock steering box in our truck only has one pressure line port coming out of it to feed the new secondary assist steering cylinder. We obviously need two lines for the cylinder to run it in and out. Unfortunately it looks like the 18K Volvo steering box is not a direct bolt in on our chassis so they have a call into one of the parts guys to see if there is a solution for our current box.

Good timing on this and I can add to the discussion. I just weighed mine, mostly to see how it compared to the sticker from mfr, which listed 34900 as rig weight. I had 14600 lbs on the front axle on mine, and about 20600 on rear axles together, for combined weight of just over 35K. This was with just me in it, about 50% fuel, and not much water and drained grey/black tanks. So it appears the mfr sticker is pretty accurate.

I don't know what capacity my front axle is, my tires are 11R22.5 size. Seems I am near or over what many of the tire mfrs list as load capacity for this size tire?

38Chevy454, Who's the manufacturer of your truck and what does your sticker say for the front axle capacity? With a light load of fuel we were at 14,860 lbs on the front and 22620 lbs on the rear tandems. Hopefully you have the H-rated (7160 lb) 11R's and not the G-rated 11R's? Our first sign of a problem was the squat in the side wall of the 11R's. One of the tire guys we went to could tell we were overloading the tires just by looking at the side wall.

The big change in mind set for me happened after I went and talked to the Renegade guys at SportTruck | Home . The owner was extremely helpful and told me how they went through their own learning curve on the front axle capacities. He said they started by changing a few 16K front axle trucks over to 18K before deciding to go to 18K on all the new 40' trucks.

We also had a problem steering our truck at slow speeds or when sitting still. Our new set-up uses the same steering box as before but we'll have a secondary steering ram on the other side of the truck for steering assist.

So the new Freightliner Cascadia with an18000 lb front axle has 315 80R22.5 tires on it. This tire is spec'd at 9090 lbs per tire at 130 psi.
When I ordered my 2007 Century with a 16000 lb front axle the 315 were the tires that came from the factory.
After the conversion and I scaled at 17500lbs I bumped the pressure to 130 (for the load capacity) and talk about a rough ride.
Then I upgraded my Freightliner from 16000 to 18000lb capacity. I bought new Alcoa 10.5 rims and put 365 70R22.5 Michelin XZA. These are rated at 10500 lbs and to carry 18000 I only carry 100 psi, which makes for a way smoother ride than the 315's I took off.
Not sure how Freightliner calculates tire capacity today but it does seem different than the way they used to.

Good info Gordy. We should be picking up our truck tomorrow then taking it in for new tires and an alignment. Right now I'm only planning on running 115-120 psi in the 315's. Michelin rates the 315 tire combination at 16,480 lbs @ 115 psi & 17,060 lbs @ 120 psi for a single wheel axle application which should be fine for us.

We also added a little more front spring in the truck so It'll be interesting to see how it rides after all the changes.

We got our truck back late last week, loaded everything up then took off for a race in Vegas. I'm very happy so far with the modifications. The steering is way better with the new dual steering on the front axle. I also like the new Michelin 315's & the ride they're giving us. The tire shop only filled them to 110 psi when we left so we bumped them up to 120 psi for the trip back from Vegas.

Update on my situation. I bought two new 315/80R22.5 BFG ST230 front tires. These are the same load range L or 20 ply rating tires with a 9090 load rating on 9-iinch wheel, or 8000 lbs on a 8.25 wheel. Since i used my orig wheels and are 8.25, I still have some margin. Tires were $586 each, and $1362 out the door with taxes, mounting and balancing.

Finally took a long enough trip last weekend (325 miles one-way) to really give the new tires a road test, beyond the 30 miles driving home from the tire dealer. I run at 120 psi, and don't really notice any difference in the ride vs the old 11R22.5 tires. The new tires track nice and run smooth, they are balanced at installation by the dealer since they are front steer. The slightly wider tires fit the wheels fine and the truck has no rubbing issues. No tread wear issues, my alignment seems good.

On my axle, it is rated 12K, but the same axle is used for 13.2K, and best I can figure the 14.6K axle is different. Talking with several people, there seems to be a lot of trucks that actually run over limits a bit and no reported problems. I am going to pursue a used 14.6 take-out axle assy to swap, but for now I feel fine with my current axle. The springs do not sag or have bottoming out issues, and the fact i am running at way less than the the GVWR (50K) or GCWR for the truck is more reason to not worry.

The next big tire purchase will be to replace the aging, but not even close to worn, rear tires. No need to change them to higher load, they run at approx 40% load capacity. Biggest issue with the rear is just need 8 of them that will be a nice bill to pay.

Good to hear 38Chevy454. We have a second trip under our belts, went up to Fallon NV a few weeks ago. I really like the feel of the 315's on the road. Interstate 40 is pretty rough in western Northern AZ and the 315's seem to take the ruts just fine.

DeepVee-look into joining FMCA (Family Motor Coach Association). They have a "national program" with Michelin and you can't believe the deals. My 365's were around $1060 for a pair and that included mount and balance.