ATF: Cyclone - Axle Spacing

[danemayer]

Stepping back from all this, it sure looks to me like this spacing issue is an unintended consequence of changing to larger wheels/tires.

I'm not an engineer, but I'd guess that axle spacing isn't just about making room for the tires. I'd guess it might affect balance, how the rig tows, and perhaps stress factors arising out of weight distribution.

The engineers design some rigs for 33" and others for 35". I'm just thinking that there could be related design issues we're not aware of.

Do you really want to deal with the next set of unintended consequences?

 

[oscar]

The reason I don't chip my truck and run the oil they recommend, aside from the fact that it voids warrantees.

One immediate effect from increasing spacing is even more twisting and the resulting tire wear.

 

[scottyb]

The engineers design some rigs for 33" and others for 35". I'm just thinking that there could be related design issues we're not aware of.

Do you really want to deal with the next set of unintended consequences?

I'm not buying it. "Let's build the longest trailer we have ever built to date, and let's give it the narrowest axle spacing possible". You are giving the "engineers" way too much credit. I see it as merely an oversight. There is no way you can convince me that 35" spacing would be anything but an improvement in performance. Yes i do understand the issues of 3 axle trailers with twisting and turning. I pulled my 1st 3 axle 6-horse gooseneck with my learner's permit and my Mom sitting in the passenger seat. I pulled that same trailer into my 20's. I have also pulled a 28' Rescue boat on a 3 axle trailer, and a 36' gooseneck flatbed with 3 axles. None of them had this issue, just like the Voltage in my photos. Maybe someone from the "Factory" will weigh in and change my mind.

 

[porthole]

MOR/ryde IS


And all the threads/posts change ..............

 

[CrazyCooter]

With this style of suspension, leaf spring/shackle, you will always have a different axle spacing between the front to center axle and center to rear axles. As a leaf spring compresses, it gets longer and this distance is taken up by the shackle.

On a tandem axle arrangement, the axles will get closer together under load and move away when load is removed. With the triple arrangement , depending on where the shackle rockers are located, the one pair will get closer and the other will move away under loads. There is NO WAY around it with this suspension design. They could only be symmetrical if the hangers are welded on at a certain load condition.....Then when loads changed, it would be off again.

To run the tire size you have, you really should have 35" axle spacing. Was that pic taken loaded for a trip? If not, I would not tow it loaded with those tires as contact while hitting bumps is likely. It will get worse with time as those springs sag. The fender spacing clearly looks to be for 35" spacing.... not for your 33" spacing. Another thing to look for is that your shackle rockers are indeed for the 33" axle spacing....your shackles should be near vertical or maybe like this \./ slightly if unloaded like the pic below. If they look like this /.\ with the period being your rocker pivot bolt, you have 35" rockers installed on your 33" hanger spacing.

Mine is a tandem with 7K axles and 35" spacing. I felt the suspension was too soft as body roll was present. I added a leaf to each of the springs to correct it and lift the chassis a tad for bed clearance. My loaded axle center spacing is now 35.25" as a product of my springs getting shorter since they don't compress like they used to.

On a triple axle setup, where scrubbing is far worse than the tandem, I would prefer to use a heavy spring and 33" axle spacing combined with the Goodyear G614 235/85R16 which tends to run a tad shorter in height than the truck tires to minimize tire scrub and lateral loads to the chassis while turning.

 

[scottyb]

Was that pic taken loaded for a trip? If not, I would not tow it loaded with those tires as contact while hitting bumps is likely.

No, it is not loaded in the photo but it looks the same when loaded to the max. I have towed it 4500 mi loaded heavy with no tire scrubbing. The only time they get really close is in a tight turn in a parking lot or fuel stop. Thanks for the explanation on the lack of symetry.

 

[wiredawgchief]

Fellow Cycloners, I'm not too concerned about mine. I had a 1999 Travel Supreme that had the same setup. I had about 1.0 to 1.5" between the rears and center with a little more on the fronts. It came with 235-16-E LT tires and never had a problem. I noticed it on this one too, but still no concerns. That unit towed great and so does this one. Ron

 

[oscar]

OK, in all fairness I took (another) hard look at it after coming to a gentle stop straight ahead. Although the spacing is less than I've seen on other trailers, it is even between all three. Yes, a bigger tire could be tight, but I'm not sure I feel the urge. Carry on.

 

[ssober]

I agree with one of the earlier posts about the 15" wheels and the axle spacing. A 6000 lb axle will stay within the ratings of a 15" wheel and a 225 trailer tire. I have been there done that and got the t shirt. Blew every tire off the trailer twice. That was my old trailer and i ended up with 16" wheels. It would be nice to see symetrical spacing.

 

[scottyb]

Added another 1200 mi last week. I was loaded for bear, carrying 2000+ lbs in the garage, a weeks provisions and clothes, and full load of water for 3 days of boondocking at my 1st stop. I wasn't sure of a water source and was planning a late arrival. The trailer pulls amazingly. No complaints, and I subjected it to some adverse conditions, with west Texas winds. It was litterally 30 - 40 mph winds the day we moved from Rio Grand Village to Lajitas (90 mi). I am going to chill about the axles for now. I am super pleased with the coach.

 

[oscar]

It would be nice to see symetrical spacing.

I'll state (again) that when I stop gently straight ahead the spacing IS symmetrical.

 

[TwoGypsies]

We bought our 3812 in early 2011. When I noticed the spacing miss-match I started looking closely at the spacing on every triple axle Cyclone I could find. They may be out there but I have yet to see one where the axles are symettrically spaced. This includes looking at several brand new units at dealerships. I've seen triple axles with even spacing, but always on other brands. The Cyclone axle spacing leaves one pair somewhat on the tight side, especially if you're contemplating a move to LT tires. If you decide to go to LT's, consider LT245x75R16's which have an almost identical diameter with the Towmax ST's that our trailer came with.

 

[wiredawgchief]

Friends, I previously owned a Travel Supreme, on of the top three luxury full time manufacturers in the industry. Because of the weight of these units, they were never offered with 15" wheels. I had the same spacing on that unit as I do with this one except it came with LT tires. The rear two had approx. an inch of spacing and the unit weighed 17,800 lbs and the tires never touched. If you look at the design, the more weight, the more spacing. If in doubt, contact Dexter. They'll tell you the size tires that can be fitted. For me, I'm getting ready to test the Tow Masters. I'm going to purchase the tire pressure and temp monitoring system that constantly report temp and pressure. I'm running 70 and 75 mph and seeing temps around 90 degrees. Any of you weigh your rigs loaded each tire? I'm an Industrial Technologist and can tell you from a manufacturing perspective, that, as long as you balance your rig AND you don't pull it with a truck that is too far over it's limits, you don't need to do anything but keep the pressures right, cover the tires and keep the tires on wood planks when stored AND don't run them more than five years after the date of the tires, you're pretty much OK. I expect when I'm done. my 3950 will weigh about 19.5K to 20K lbs. And, the axles, tires nor pin will exceed max ratings. The manufacturer, because of liability issues cannot say this. The line has to be drawn some where. You want to buy a unit rated at 22K to 25Klbs? You can buy them for about $125K to $150K and more. These units are just fine the way they are. You just need to understand all the attributes. And, don't forget to address your tow vehicle. The biggest there too: Axles, tires, transmissions and BRAKES. Load your unit and tow rig and weigh each tire. This isn't Flying J and is likely going to cost you about $150+ to have done, but will be the best money you ever spent. Take care and be safe, Ron

 

[danemayer]

I'm running 70 and 75 mph and seeing temps around 90 degrees.

Don't forget to check the tire manufacturer's speed rating. Many of the ST tires are not rated for that speed.

 

[wiredawgchief]

Dane, I can't find a speed rating on these tires. Neither the Power King website nor anywhere stamped on my tires is there any indication they are speed limited. I need to correct myself though...I run 70mph typically, not 75. Not trying hijack the axle thread to tires, but it's all relevant. These units are fine, built very well and are very capable. These axles will have the same percentage of spacing difference no matter what tires are put on them and it is not a manufacturing nor configuration error. Ron

 

[danemayer]

This might be the page

http://towmaster.com/trailers/maintenance/tire_info/.


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[wiredawgchief]

Dane, I emailed Power King asking the question outright if there MAX 24 tires can be safely operated a 70MPH with proper inflation and within load limits. Here is their spec sheet with speed info left out. http://www.powerkingtires.com/Tires/Trailer/ST Radial/318 I'll let everyone know their response. Ron

 

[danemayer]

Ron,

The way I've heard and read it explained, the faster you go, the faster and more frequent the flex of the steel belts within any given time period. Flexing generates heat. The tire is designed and constructed to dissipate a certain amount of heat within a given time period. Going faster than the design point may generate more heat than can be dissipated. That excess heat breaks down the tire. Internal damage occurs, but may manifest later on, way down the road; maybe next year.

Btw, under inflating, or overloading both increase the amount of flex, which also generates more heat.

My non-expert opinion is that if you load the RV to within 5% of the tire load spec (probably most of us are there), and you under inflate by 5% (not hard to do - just takes a slightly inaccurate gauge), you're living right on the edge. And if the tire manufacturer's process isn't perfect, he may turn out a batch of tires that are 5% under the design spec. Uh-oh.

Speed is the one variable over which you have complete control. Drive fast - live on or over the edge.

 

[wiredawgchief]

Dane, First, I received a reply back from Power King...the MAX 24 STR tires are speed rated at 65mph. Second, my bad for not providing all the numbers that I'm using to manage weight on my rig. I weighed trailer at each tire: avg 2,500 lbs with rating at 3,520 leaving 1,020 or 29% headroom; Axles avg 5,000 with rating 6,000 lbs leaving 17% headroom, GVWR of RV 18,000 lbs, weighed 18,700lbs and 3,700 pin weight. I don't know the rating of the pinbox, but would guess between 20K and 30K lbs due to stresses induced to it. I'm exceeding two variables on my rig: the speed on the tires (5mph) and the GVWR of the RV, which is basically the frame and structure. I'm not exceeding critical tire weight, axles, and pretty sure (99 and 44/100 %) I'm not exceeding the pin box. This weekend, I took the RV 180 miles to Del Rio on Sat and cam back today running 70 mph. I shot the tires with a infrared thermometer and consistently read 80s and 90s, great temps. Checking tires cold every day, shooting them with thermometer every couple of hours, and driving carefully, I'm confident my weight and speed numbers are good. Getting ready to order tire pressure and temperature monitoring system to have constant visibility. I'm counting on any failure will have elevated temperature before having a problem. I see you're in TX also...we need to hook up. Ron

 

[danemayer]

Ron,

We're planning on being at the Fall rallies for the North TX and South TX Heartland chapters. Join us.

Dan


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