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2016 Sienna XLE FWD
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162 Posts
Discussion Starter · #1 ·
I recently purchased a set of Cooper Discover AT3 4S in a 235 65 R17 (1” taller overall (1/2” more ground clearance). I wanted the XL load rating for towing and AT ability for dirt forest service roads. They didn’t do my gas mileage any favors (2mpg+ drop) between the larger diameter and tread pattern. However, my speedometer, GPS and iPhone now all match. If the wheels are locked to the left while reversing and I hit I bump, I get a slight rub. Otherwise they have been awesome for towing, dirt road driving and water displacement.

I wanted 235 65 R17 spare on an OEM wheel for towing and trips in remote areas.

I got a used wheel on eBay for $130 and a XL rated tire installed with damage protection from Discount Tire for $115. It measured just under 29” outside diameter.

Under the vehicle where the donut resides:
I bought two additional AirLift heat shield kits for $10 each from Summit Racing to shield the larger tire. It fit, but was in direct contact with the heat shield. It actually didn’t smell after a few hours of driving. It also seemed to have an additional negative impact on my MPG due to how far it hangs down. I have a rear lift, so I still had 7.5” of clearance, but it must create some serious wind resistance.

In the roof box:
I placed the full size spare in my 2013 Thule Force 624 L. It was a bear to get it up there. I strapped it down to keep. From shifting. I may cut a piece of wood to put underneath it to help disperse the weight more over the cross bars.

Anyways, just my experience with a with options.
 

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'11 Limited FWD
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That under-vehicle option sure looks bad. Seems like you already realize that, but to me it's a massive safety issue. Not only would you be giving up all of the ground clearance you were trying to gain, and then some, but there's a big obstacle underneath. Encountering a rock, or a ladder, or any number of routine highway dangers would be potentially cause a lot of damage to the van, never mind the risk of loss of control. You are seeing 7.5 inches of clearance now (less than stock Siennas) but with load, and speed, and normal highway undulations it would often be much less. Hitting a hard obstacle at 70MPH would be awful.
 

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2016 Sienna XLE FWD
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162 Posts
Discussion Starter · #3 ·
Yes… really just took one drive to realize it is not worth the benefit of having it under the vehicle. I’d imagine it would be pretty quick to get ripped out from under the vehicle in a serious collision and then you’ve got a loose wheel flying around the highway.

Additionally, even with shielding, full on conductive heat is way too hot for it. With a little gap the radiant heat would probably be acceptable.
That under-vehicle option sure looks bad. Seems like you already realize that, but to me it's a massive safety issue. Not only would you be giving up all of the ground clearance you were trying to gain, and then some, but there's a big obstacle underneath. Encountering a rock, or a ladder, or any number of routine highway dangers would be potentially cause a lot of damage to the van, never mind the risk of loss of control. You are seeing 7.5 inches of clearance now (less than stock Siennas) but with load, and speed, and normal highway undulations it would often be much less. Hitting a hard obstacle at 70MPH would be awful.
 

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'11 Limited FWD
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173 Posts
I'm thinking more that the wheel is basically jammed between the obstacle and the rear wall of the spare tire well, tearing into the body and catapulting the van (this happens with broken driveshafts).
 

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If you have a donut spare just use that and keep a can of Slime and a plug kit onboard. You'll be fine. Or you could put it on a hitch carrier. It's going to be pretty terrible wrestling that spare out of a roof box and getting the blown one back up there. Mounting it underneath looks like a junk show tbh.

I have no stock spare so got a RIGd Ultramount (very cool but $$$) and also keep a can of Slime and plugs, since there's no sort of roadside assistance out here.
 
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