Gents,
I just got back from the Ford Dealership and the tech there advised me against putting anything bigger than a 17" tire/rim combo on the car. His reasoning is that this puts more stress on the ball joints as opposed to the lower control arm bushing/bearing. I am really looking at premature wear due to the larger wheels. I really had my heart set on the DD 20" Black Bullits. Of course I know wheel size is a matter of taste but technically speaking am I just looking for trouble?
Thanks as always for the feedback.
Cheers!
Irish

 

I don't think so. As long as the overall diameter of the tire stays the same, I wouldn't think that you would have any problems. Of course I'm not a Ford mechanic, but he probably doesn't mod a lot of vehicles.

 

well my car came with factory 18's so i don't see how 17's is the safest

 

That only shows how little the dealer knows...
Your stock tires, they measure 27.34" from top of the tire to the bottom (on 235-55-17)
If you put 20s (245-40-20), it would measure 27.84 inches, that's only 1/2" higher than stock, so I don't know how that is going to put that much stress on ball joints.
If you take dealers out of what they are used to seeing, then they do not know what to do with it, and they will tell you "it hurts the car"...

 

Maybe its from the increased traction of a wider tire that will stress the suspension more than the greasy stock tires. Also how can you stress any one component more when they all are connected? Higher stress loads are shared thought the whole system.

 

Totally Wrong.Tire size does not effect any suspension parts at all.Just like Sears wont put any diferant tire size or design except the fatory recomended.
you could have 50 inch tires and the car is still going to roll on the hub axis.the distance from the ground will change but thats it.

 

I'm not a mechanical engineer, so i don't know exactly which components would be affected, but if you increase the diameter of the wheel, and keep the tire diameter the same, that would mean you would have less sidewall, and hence less cushioning when going over a bump in the road. Less of the energy would be absorbed by the tire, and more of it would be transferred to the suspension. This would cause additional wear on the suspension. Now, that being said, how much more wear? Well, that would have to be done testing or simulation.

 

You forget about the additional load on the bearings. Also, with a much larger tire diameter, the gearing will have to change, otherwise you'll be putting a larger load on the engine simply to get the vehicle to move from a dead stop.

 

I would think a larger wheel would have some type of effect because even if the diameter might be the same there is more metal than before spread out wider which is heavier than the rubber tire. You'd probably have to look into gyroscopics and even so I don't know if it would even make a difference in suspension wear

I have no idea :scratch:

 

The dealership guy you talked to makes no sense. A larger rim does mean more weight and more rolling inertia but the suspension components would be affected minimally. The only system that takes a beating with larger wheels is your brakes. 10 pounds at the wheels equates to about 100 pounds in the car.

 

If thats true then why do dealers add 19 and 20 inch tires before you buy the car. I have seen a lot of new cars on dealers lots with upgraded rims/tires.

 

Not totally wrong, like I said increased traction = increased dynamic forces on the suspension. If you are capable of .89gs laterally with a 17 inch street tire and you go to a 20 inch performance tire that will allow for a .94 g turn that is increased load on the suspension components. Also wider wheels usually move the center line of the wheel out away from the axle bearings to clear shocks, brake calipers or what ever is in the way. This move increased side loads on the axle bearings and ball joints. Its like giving the wheel a longer leaver.

 

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From what I have seen in the vehicles that I have worked on, larger wheels generally do decrease ball joint life. I think the problem stems from other factors of the larger wheels though. First of all, people often put wheels on their vehicles with the wrong offset, which increases the load on the suspension, and affects every aspect of the suspension. It affects the scrub radius, etc, which all help to determine load on the parts. Also, generally when you go to a larger wheel, you go wider, which also increases load/leverage.

To put it simply, parts can and do wear faster with larger and wider wheels/tires. This is not limited to ball joints, but also tie rods, steering racks, hubs/bearings, etc. If you stay reasonable, you will probably never notice a difference, but if you push the limits, you welcome problems. I have seen these problems the most on trucks, where the variation from stock can be huge, but thats not to say it couldn't happen on a Mustang as well.

Others may disagree, but as someone who works on cars every day, that is my opinion, so take it however you like.

 

I think you're off on your logic train a little bit. He's asking about larger rims, your talking about better tires. Bigger rims do not equate to better traction and the "increased load" you mention. Following your train of thought no one should put on better tires because the traction will put load on suspension, but the rim size has nothing to do with it. Just trying to keep us on the same sheet of music.

 

OK you could be correct, but why would someone go through all the expense of buying new wheels and tires just to put the same size on? Granted the wheel would be larger with a same with tire.

 

Because the tire size is fine. The larger rim just looks better, and its easier to keep your speedo/odometer calibrated.

 

Bigger rims equal more rotational mass. This does place a load on the braking system and the suspension as well.

 

more rotational mass? Not really, as long as the new rim/tire equals about the size of the stock rim/tire, you should be fine. Besides, I highly doubt Ford would make a car with suspension components that can only handle the rims they install... sounds ridiculous, hu?
Maybe 18s from factory wears the suspension components and braking system as well... maybe they shouldn't put that and we should all be driving with 16s like the V6s.... anyone has any thoughts on that?