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Author Topic: Chaining up tag axle  (Read 3107 times)
captain ron
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« on: November 02, 2006, 10:28:54 AM »

In an effert to increase my fuel mileage it has been suggested I try chaining up my tags. When I bought the bus the tags were chained up. It came from Colorado so I'm guessing it was for traction porposes. I'm wondering if this will cause any damage? Or any other problems?


Ron, I moved this to the main board where it will hopefully get a little more attention.
Richard
« Last Edit: November 02, 2006, 11:47:11 AM by DrivingMissLazy » Logged
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« Reply #1 on: November 02, 2006, 12:35:37 PM »

Ron I would think this would take weight off the steer tires , and make the front end feel light. Huh
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« Reply #2 on: November 02, 2006, 12:41:42 PM »

You're going to chain up your tag axle in order to increase your fuel mileage?Huh  What are you expecting to achieve, maybe a tenth of a mile per gallon more?

Ok, sorry, I'm feeling a bit cranky today.

There's a reason MCI put tags on these buses. It has to do with weight carrying capability and distrubution, drivability, and stability, stoppability. Suffice it to say I think it's probably not the wisest decision to chain them up and not use them for what they were designed for. I also don't think you'll see ANY noticable difference in fuel mileage.

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« Reply #3 on: November 02, 2006, 05:07:37 PM »

Hi Capt. Ron & Folks:

Ron, most importanbtly, if you chain up your tags axles and run down the road, you have 2 sets of barkes that are not functioning, and you do need them!!!!

The tags are there not only to support weight but to stop he heavy Beast!!!!!

I hope this HELPS!!!

Happy & SAFE!! Bussin' to ALL.
LUKE at US COACH
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« Reply #4 on: November 02, 2006, 05:29:48 PM »

Even though you won't come close to overloading the front and rear axle only, I would keep the tag down for the extra stability and braking power.  Over the road buses don't have the huge brakes a transit bus has, like I have.  So, in contrast, I feel perfectly safe with only two axles, since I'm 5,000lb below the 36,000gvw rating-and that's for stop and go service.  I have seen some plainly take off the tag axles altogether.  That does eliminate probably close to a ton of equipment and frees up additional storage space (think MCI 102A2, and 2 axle Eagles).  Good Luck, TomC
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« Reply #5 on: November 02, 2006, 05:48:19 PM »

I can't understand what the logic would be that would lead you to believe that lifting two tires would improve your fuel mileage.  Don't do it.
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« Reply #6 on: November 02, 2006, 05:55:02 PM »

I see the logic of not dragging and extra set of wheels for mileage purposes but don't know if it is the right thing to do. In snow country they do pull up the tags when it gets slick. I have seen buses on the side of the road when the going gets slick because they cannot climb a hill. If they pull their tags up it does give them better bite.
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« Reply #7 on: November 02, 2006, 06:03:13 PM »

Hi Tom C and Folks:

Good post Tom, but you make reference to a 102A2.

Capt. Ron's bus has 5 inch wide front & tag  brakes and 8 inch wide rear brakes.

A 102A2 has 6 inch wide front & tag brakes and 10 inch wide rear brakes., so the engineers obviously adding a lot more braking power for the 2 axle version, while eliminating the tag axle.

I post strictly for informational purposes, so that readers of this post do not compare apples and banannas and:

I Hope this HELPS!!!!

LUKE at US COACH
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« Reply #8 on: November 02, 2006, 06:09:14 PM »

Captain Ron -

It states very clearly in the MCI Operator's Guide that chaining up the tag axle is for emergency only, and that the coach should be driven at reduced speeds until repairs can be completed.

Anybody want that page of Da Book scanned for them??

FWIW & HTH. . .

 Wink
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« Reply #9 on: November 02, 2006, 10:37:28 PM »

Luke- that makes sense.  I too have the 6,10" setup.  Compared to normal 15 x 4 and 16.5 x 7, they are huge compared to truck brakes.  Good Luck, TomC
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« Reply #10 on: November 03, 2006, 03:30:17 AM »

Many, if not most, triple axle trucks and coaches here have the undriven rear axle on hydraulics so it can be lifted when the vehicle isn't fully loaded. In some coaches the third set of wheels is hidden behind the bodywork, so the vehicle looks to only have two axles from the outside. Big tyres have a lot of rolling resistance, so having fewer of them will make a small but significant difference to economy. Remember that, other than perhaps Saudi Arabia, America probably has the cheapest fuel of any country in the world, so historically manufacturers in Europe and elsewhere have traditionally put far more effort into fuel economy measures.

Jeremy
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« Reply #11 on: November 03, 2006, 05:20:08 AM »

jeremy, we arent comapring apples to apples with the truck vs bus comparison. The bus is nearly always loaded the same, only variables being whether holding and fuel tanks are full.
  My bus doesnt handle the same with the air off the tag bags, let alone the brake efficency.
If it REALLY saved fuel........you would have seen Greyhound and Trailways with their tags up............
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« Reply #12 on: November 03, 2006, 06:03:08 AM »

jeremy, we arent comapring apples to apples with the truck vs bus comparison. The bus is nearly always loaded the same, only variables being whether holding and fuel tanks are full.
  My bus doesnt handle the same with the air off the tag bags, let alone the brake efficency.
If it REALLY saved fuel........you would have seen Greyhound and Trailways with their tags up............

There must a be HUGE difference in weight between an empty bus and one with 60 passengers and it's bays full of luggage. That's why they have liftable axles - not whether the holding tank is full.

If Trailways and Greyhound paid half as much for their fuel as operators in other countries do, you can bet your bottom dollar they would be immediately investing in liftable axles (and a lot else besides).

If I had a 'heavy metal' American bus conversion, or even a full size triple axle European bus, one of the first things I would do is fill all the water tanks right up and take it to a weigh bridge to find out it's heaviest 'converted' weight. Then I would deduct the estimated weight of the tag axle, and compare the resulting figure with the original GVW of the bus full of passengers, luggage and fuel. If 'my' bus was significantly* lighter than the original maximum design weight I would have that tag axle off in two shakes of a duck's tail: - less weight, more mpg, fewer tyres to replace, and a lot of extra space underneath for whatever you want to use it for.

Just my opinion - *and quite what 'siginificantly' means is entirely debateable of course.


Jeremy

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« Reply #13 on: November 03, 2006, 09:05:53 AM »

And last but not least, the max speed with a tag chained is 45 MPH per a Crusader owners manual.
That would eliminate the chained tags for most.   
The manual also says best to remove and store the tag when operating with a chained tag axle.
FWIW, JR
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« Reply #14 on: November 03, 2006, 09:29:37 AM »

Best advice to improving fuel mileage is to SLOW DOWN. These busses have the aerodynamics of a brick. Wind drag goes up exponentially with speed & after 45 mph, wind drag is more than rolling resistance.

Also, find out where your engine's peak torque is & try to cruise at that rpm as that is usually where the engine is most efficient.

I'll bet the reason trucks have the lift axles isn't so much for fuel mileage but to save wear & tear on the tires. Those things scrubb an awfull lot & I've seen 'em tear up pavement.
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« Reply #15 on: November 03, 2006, 10:40:04 AM »

Gosh Folk's
Us older bus owners that own the GMC Buffalos with the optional drop down tag axle are way ahead of the later model MCI and other type buses that are on the road today.
GMC was way ahead of it's time when it came to bus building.
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« Reply #16 on: November 03, 2006, 05:54:29 PM »

When I was driving for the charter company it was a rule that you not run down the road with the air off of the tag axle.  This would have caused damage to the airbags on the tag axle.

I personally released the air from the tag suspension on several occasions when I got into a situation where the empty bus didn't have enough bite after unloading to drive away from the unloading area.  Once I was someplace where I could get good traction elsewhere in the parking lot, I would put the air back on the tags.  Then when I loaded the passengers I didn't have a problem at the same place as the drop off.

One time I had a passenger get back on while I was moving to the parking area and we couldn't move.  He wanted to know if he should gather everyone else from the passenger load and push.  I let the air off the tags and told him "sit down we are leaving."  He wanted to know what I had done as we didn't slip at all.

I have heard other drivers that have driven with a tag chained up say that the bus wallows like a wounded hippo. 

Yes the tag axle eats tires in tight turns.  A large number of buses making the same tight turn on concrete can really lay down a lot of rubber in a short amount of time.  Our company would use a tire on the steer axle, then the drive axle and finally on the tag axle.  There the tire would end its useful life and then be returned to the leasing company.  I know it is difficult to prevent tight turns that scuff the tag but do whatever you can to prevent these turns and the tag will last longer.

Those tags are there for a reason and I would not want to drive a bus that started out with tags and had them chained up or removed.
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« Reply #17 on: November 04, 2006, 06:55:18 AM »

Hi Tom C and Folks:

Good post Tom, but you make reference to a 102A2.

Capt. Ron's bus has 5 inch wide front & tag  brakes and 8 inch wide rear brakes.

A 102A2 has 6 inch wide front & tag brakes and 10 inch wide rear brakes., so the engineers obviously adding a lot more braking power for the 2 axle version, while eliminating the tag axle.

I post strictly for informational purposes, so that readers of this post do not compare apples and banannas and:

I Hope this HELPS!!!!

LUKE at US COACH

I believe the 96A2 and the 102A2 also had a different wheelbase than the 3 axle coaches.  They didn't just remove the tag.  I also believe the GVW was about the same, not sure about the turning radius.

I'm not sure if the same thing applies to the Eagle Suburbans. I think they just removed the tags and reduced the GVW.  Some converters of entertainer coaches also removed the tags (Caldwell Brothers for one)

Personally, I think if you keep the conversion weight down, a two axle forty footer is well suited for our purposes.

Len
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« Reply #18 on: November 04, 2006, 08:53:44 AM »

The Eagle suburban was a 35 foot coach. All with the bogie axle were 40 foot.
Richard
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Dallas
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« Reply #19 on: November 04, 2006, 01:57:37 PM »

Here are the pages from the MCI Maintenance Manual for the 96- A2, A3 and 102- A2, A3.

You need to remember that the wheel base on the 3 axle MCI's is measured not from center of the front axle to center of the tandems, (like a truck is), but from the center of the front axle to the center of the drive axle.

The wheel bases on on the 96A2 and 102A2 are longer because the drive axle has been placed where the tag axle on the 96A3 and 102A3 is. Thus the 2 axle coaches have a lager turning radius than the 3 axle coaches.

Also notice the vehicle weight and payload capacity.
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Dallas
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« Reply #20 on: November 04, 2006, 02:01:51 PM »

And the second page:
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« Reply #21 on: November 06, 2006, 03:45:27 AM »

It so happens that when returning home from a long trip on saturday evening I had to wait for a short while only 1/4 mile from my house as the road was blocked by a big double-decker coach (a Scania I think) trying to do a 3-point turn (I live close to a motorway junction, and the coach had evidentally taken the wrong exit off the roundabout). Whilst watching the coach doing the manoevre I realised the Scania was fitted with a steerable third axle, which is something I had not seen before on a bus. Obviously truck trailers often have steerable axles, so I guess it's a no-brainer to put them on a bus as well - it's just that I'd never actually seen one before.

Jeremy
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