Single to Dually Swap for Driving Stability?

[Buyzen]

Hellooo eveyone! New member here... introduced my bus in the new member forum. I have a 2013 Chevy Shuttle Bus.. 3500 single rear axle. I've driven it from the west coast of Canada to the prairies where I now live and what's clear to me is the lack of stability and constant steering correcting I have to do when driving on the highway from winds, trucks and dips in the road/pavment. I don't drive past 90-95 kms/hr otherwise I don't feel safe due to the sway/tippy feeling of the bus even though the bus has lots of power and many of the highway speeds are 110-120 kms/hr.

I've done a bit of research on this matter and have seen suggestion for suspension upgrades, etc. to help with the counter steering but at the end of the day I feel swapping the single rear axle for a dually would be the change it needs for added stability and handling.

I'm unsure of this process.. the cost, etc. so any information would be greatly appreciated. This issue has been stopping me from progressing on my build. The inside is gutted and a blank slate but until the stability/constant counter steering on highway driving is addressed... I feel I can't move forward with my build.

Thank youuu!
Buyzen

 

[s2mikon]

Are your wheel wells large enough to accommodate dual rear wheels? What about your spare tire if you have one.

 

[Buyzen]

It doesn't look like it without lot's of modification work. I mounted a new spare tire under the rear when I bought the bus. Would wider rear tires help with stability? Current tire size is the stock LT245/75/R16's. I always felt they were bit too skinny.

 

[s2mikon]

I would start out with axle weights fully loaded water, fuel and luggage with the bike on the back and go from there.

 

[Buyzen]

In regards to having those things fully loaded and then addressing the stability/counter steering issue?

 

[La Camioneta]

Start with this https://www.hellwigproducts.com/products/?partnumber=7181 and then replace your shocks with the heaviest-duty replacements you can find.

 

[La Camioneta]

It doesn't look like it without lot's of modification work. I mounted a new spare tire under the rear when I bought the bus. Would wider rear tires help with stability? Current tire size is the stock LT245/75/R16's. I always felt they were bit too skinny.

And the actual tire makes a huge difference in sway. A friend got some off-brand put on his 3500 work van and he said it was all over the road. Went back to Transforces and it drove just fine again.

I have a 2500 Chevy van with Transforces and it is rock-solid all the way to the speed limiter.

 

[Buyzen]

Awesome I will look into the above link. Thanks for your replies! My current tires are Dynapro AT2's by Hankook. I think they are decently rated tires but not sure if for the bus.

 

[La Camioneta]

Good luck! The tire thing jogged my memory, not sure what it is about the Firestone Transforce that makes it a perfect van tire but I've had great luck with them.

Good shocks help a van a lot, too.

 

[joeblack5]

Check you steering alignment and wear on steering joint, does the bus have a rear sway bar? Different tires is a good thought. Weight ratio front to rear?Maybe ask a bus driver to drive the bus and see what is normal for that vehicle.

Good luck
Johan

 

[cadillackid]

tires tires tires.. also load load load.. if you have a lot of weight toward the bag the sway factor will be a lot more than if its loaded more over the axle or just a little forward of. the rear axle.. the farther back you get from the rear axle, the more the weight is multiplied...



if you want more rubber on the road, you can try a wider tire like a 265 (should fit in the wells).. however sometimes a wider footprint can increase the skate factor , esp if there is any wear in the bushings around the sprinf shackles allowing the axle to not be 100% aligned with the front.. the driveability of worn rear bushings is the perception your bus is dog-legging.. the rear appears to be off to one side from the front.. you'll try and correct it forever and never get it.. result is driving all over the road..



dont over-correct.. everything in a bus happens slower.. in a car moving the steering wheel is pretty much a direct and instant response from the vehicle.. in a bus the response is a bit delayed so you tend to move the wheel more and then the bus over-shoots... I find that very small movements in the wheel on any of my busses results in a slightly delayed but fairly pronounced response.. my load star has a wierrd steering system so it can be tricky to drive..



get the bus aligned.. every bus iove bought has been severely out of alignment .. I dont think schools ever align em...



make sure all the wheels are balanced.. (big truck tire shops often dont balance rears unless requested).. bouncing wheels can increase the skate factor as well...

 

[s2mikon]

Safety is your number one priority. You have a vehicle that is unstable correct? Is it overloaded? Is it unbalanced front to rear? You need to know. I’m guessing that your tires are around 2500 pound load rated, so for 2 tires that is 5000 pounds. What is the weight on them now? Your motorcycle on the back plus its rack is probably around twice its actual weight due to leverage. The shorter the wheelbase the higher the leverage factor. If you are over weight on the rear tires and you have a blow out due to overloading you will have your work cut out for you trying to keep it from tipping over. So go weigh it and go from there. The weight data is needed to make good decisions like buying tires and correct inflation pressures.

 

[Ronnie-SKO]

Must say I prefer a dually for a vehicle like this. A dually wheel may or may not fit, only way is to try one.



I also agree with others on checking alignment as well as any play in the steering. get all that top notch first. I too have had different tires behave different. Bought a set of Goodyear wranglers for my pickup and was all over the road with a camper on the back. I do not remember what I changed them to, but went right back to the dealer and and they swapped them. Generally speaking a straight tread tire is more stable then an all terrain or mud tire. Get as many plys as you can helps too.

 

[Buyzen]

Thanks everyone for all the replies! When I noticed the sway/tippy issue driving across Canada.. I had the bus semi-loaded with typical moving boxes but no heavy furniture. I already had the seats and wheelchair lift out. I had my motorcylce on the back but it only weights 260lbs.

Currently the bus is fully empty inside and I can still feel the issue when I drive close to 100 km/hr. It just doesn't feel as stable and safe as I feel it should. I also met a bus driver on my travels home who said that buses steering is set to slightly drift to the right of the road for safety reasons and that some of what I'm explaining is normal. But this is beyond normal. I've driven one other bus (a dually) and several of those Uhaul trucks on the highway moving and they were always very solid feeling.

I will have to find a reliable and honest mechanic to take my bus to and start with the suggestions you made. I suppose I just thought a dually setup would of been more ideal but as someone mentioned.. why try to change the axle that was designed for this bus.. especially a 2013. Being a city transit bus in the hilly roads of rainy Vancouver.. the bus probably has some suspension and alignment work to do after 10 years so here's hoping it's not the design or being a single rear axle bus that's the issue.

 

[Omnibot2000]

Google dually conversion kits. You get a spacer with dually rims. My F250 has been converted. Does make a difference. Sway bars if you don't have will do the same.

 

[Buyzen]

Hi everyone,

Just wanted to update:

As springs approaches it was time to bring the bus in for inspection. I bought the bus in British Columbia but moved home to the prairies in the fall. Upon the provincial inspection they found the front tie rod ends were VERY loose, the rear shocks are leaking and the front tires need to be replaced.

Bus is going in for wheel alignment and balancing tomorrow as they discovered negative camber as well. This was more than I anticipated for a 2013 and it having a full inspection pass in the previous province.

However in a weird sort of way I'm also kinda happy my stability issue wasn't the bus itself but rather a combination of the above. Hopefully after all these repairs it's more solid on the highway. If not I'll be looking to other stuff you all mentioned like a rear sway bar, etc.

Any feedback on what I mentioned would be appreciated and I'll relay it to my mechanic.