Different-width tires on front and rear to help with chains?

[NY2LA]

I was thinking about tire chains today in preparation for my next tire purchase and future trip needs. One thing I'd love for my go-anywhere setup is the ability to put on tire chains in an emergency.

Limiting factor up front for chains is often tire width. So, has anyone ever considered putting wider tires on the rear and narrower once on the front to accommodate chains on all four wheels? I've seen road cars with wider tires in the rear, so how about our trucks?

 

[bloc]

Doing so would limit rotation ability. And in all but the most extreme conditions rear chairs should get the job done. By extreme I mean very very steep iced out hills. Nothing you’d find on a paved road.. though I get it we don’t want to have to stick to pavement.

You could always run more narrow tires all around if you think you’ll realistically be in conditions to need 4-wheel chains.

IMO the idea causes more problems than it solves..

 

[Sandroad]

Different traction and handling capability front and rear would play havoc with stability control, traction control systems, as well as braking and driving dynamics. Don’t do it. Use the same tire on all 4 corners.

 

[NY2LA]

Different traction and handling capability front and rear would play havoc with stability control, traction control systems, as well as braking and driving dynamics. Don’t do it. Use the same tire on all 4 corners.

I've seen folks say this in this past, but the support for this claim has been limited. For one thing, some on road vehicles have different sized tires front and rear to actually improve performance, so why not an off road vehicle? For another, I'm not convinced the stability and traction control systems are dependent on equal-width tires any more than they are on having equal traction surfaces on all four spots on the ground. I don't think these systems are smart enough to differentiate between a difference in traction based on the tire vs the ground itself. I think they are just responding to the net traction being input. But any experts out there, please prove me wrong.

 

[Toyoland66]

You would be better off running a wheel spacer on the front for times you want to run chains. Cheaper and easily installed/ removed.

 

[bloc]

I've seen folks say this in this past, but the support for this claim has been limited. For one thing, some on road vehicles have different sized tires front and rear to actually improve performance, so why not an off road vehicle? For another, I'm not convinced the stability and traction control systems are dependent on equal-width tires any more than they are on having equal traction surfaces on all four spots on the ground. I don't think these systems are smart enough to differentiate between a difference in traction based on the tire vs the ground itself. I think they are just responding to the net traction being input. But any experts out there, please prove me wrong.

You can bet systems as critical as stability control are tuned for whatever tires come on a vehicle. And other routine changes like in compound of the tire would be a similar change front/rear. Yes these systems can adapt in real time to feedback they get from wheel speed, G, and yaw sensors, but they program all of this stuff to work making assumptions about behavior.

Now if we are only talking a 10mm difference out of a 285 tire, do I personally think that will make a substantial difference that the system can't adjust for? Probably not. But do I like taking changes with this stuff? No. And as I said above, there are other negatives to the strategy of asymmetric tires front to rear.


Plus.. why the need for four chains? I do remember someone here posting they had to do so for an extremely steep off-camber driveway.. but chains on one axle can safely take something like a cruiser to a whole lot of places. Have you found situations where that isn't enough?

 

[NY2LA]

You can bet systems as critical as stability control are tuned for whatever tires come on a vehicle.

You could be right. But the logical flaw here is that our custom rigs aren't using the tires that come on the vehicle. By applying your notion, one could make the argument that having two of the four tires be closer to the factory size would be better for the traction systems than having all four tires be further away from the factory size. Ie, one could argue that it would be more beneficial for the average of the four tires to be closer to the factory calibration than for all four tires to be the same size.

I don't know what the truth actually is here. But I think you and I are both theorizing. And that's why I made this post: because I see a lot of speculation on this issue and no convincing support for any viewpoint.

(Chains is my reason for asking the question. But there are other reasons one could ask too. So instead of turning this into a "why get chains" or "what axles for the chains," I'm trying to focus on the issue of different tires, which I haven't seen as thoroughly discussed.)

 

[daneo]

Would studded tires work for the use case you're planning for? Icelanders drive in a lot of deep snow and always use studded tires and never chains.

 

[bloc]

You could be right. But the logical flaw here is that our custom rigs aren't using the tires that come on the vehicle. By applying your notion, one could make the argument that having two of the four tires be closer to the factory size would be better for the traction systems than having all four tires be further away from the factory size. Ie, one could argue that it would be more beneficial for the average of the four tires to be closer to the factory calibration than for all four tires to be the same size.

I don't know what the truth actually is here. But I think you and I are both theorizing. And that's why I made this post: because I see a lot of speculation on this issue and no convincing support for any viewpoint.

(Chains is my reason for asking the question. But there are other reasons one could ask too. So instead of turning this into a "why get chains" or "what axles for the chains," I'm trying to focus on the issue of different tires, which I haven't seen as thoroughly discussed.)

I'm no stability control engineer, but from what I do know about vehicle dynamics "balance" is critical, meaning the tendency to under or oversteer from a given input. I'm guessing a lot of what the stability control does, and the assumptions it will make about X control output having an intended effect, we wouldn't want to upset its expectations that the front does Y at a similar rate to the rear doing so.. and in my brain at least, deviating too much from that balance is where we can get into trouble. Significantly different tire sizes on one axle than the other seem like a ticket toward this happening.

Yes, this is theory. If we follow theoretical stability control consequences out we shouldn't be doing the majority of the things we do on this board then drive on the road. Most of it works out fine. But significantly different tire sizes front/rear is kindof uncharted waters for this platform.. and for good reason IMO.

 

[Sandroad]

I've seen folks say this in this past, but the support for this claim has been limited. For one thing, some on road vehicles have different sized tires front and rear to actually improve performance, so why not an off road vehicle? For another, I'm not convinced the stability and traction control systems are dependent on equal-width tires any more than they are on having equal traction surfaces on all four spots on the ground. I don't think these systems are smart enough to differentiate between a difference in traction based on the tire vs the ground itself. I think they are just responding to the net traction being input. But any experts out there, please prove me wrong.

It’s fine to have different size tires front/rear if that’s how it’s fitted out OEM.

My info on any issues with tires comes from The Tire Rack. I try not to make up too much

https://www.tirerack.com/upgrade-garage/is-it-ok-to-mix-tires

 

[doru]

The question is what advantage the narrow front tire will bring you.

The cars that do that is for increased sport performance on paved roads. Those cars are also rear drive cars. They use the big meat where the traction is needed - rear (or front if you look at a front-drive drag car). The fronts are narrower as they no longer need to provide forward traction, just steering and braking. The narrower front also means less sprunged weight on the wheel and on the suspension, helping with both acceleration and car dynamics. The narrower tire also helps with quicker turn in so more agility.

Coming back to our trucks I do not see any of the above important until you put the truck on a drastic diet to lose at least 2000 lbs. But most of us are going in the other direction adding weight. And the fact that we are permanent all-wheel drive puts the whole project into question as you will lose effective traction for little gain, and a lot of pain in the but to deal with the logistics of having two size tires.

As for the chain stuff, get a 10mm narrower tire and/or spacers and a cable type chain like Security Chain Company ZT751 Super Z LT or even lower profile Super Z6 SZ451. Those are available on my size 285/50R20 and I've tested on my truck (I created a post on MUD with lots of pics).