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87 Wagon available in Portland Or Area


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I was thinking about this, and I hope this question elicits some response..

 

 

"4x4, Hi-Lo tranny,5 speed, 6 Inch SJR Lift kit, ......... twin stick modification(you can put it in 2wd LO to drive around town with those big tire) ...... Brand new 31x10.5x15 super swamper SSR'S ..... This rig would make a great wheeler it runs good around town but has trouble on Highway due to large tires and gearing but runs great on the trail."

 

 

but the ad mentions that the large tires would cause trouble on the highway.. why? I would imagine that if you could use the low range to get up to a reasonable speed, then shift into normal range, the tires would essentially serve as a mega overdrive, and wind up simply giving you superb highway fuel mileage???? Am I totally misconceived on that? Is there something about the lifted subaru on swampers that is simply unstable at highway speeds, beyond the gearing that I am not aware of? I am not understanding the highway problem with this vehicle... :confused:

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but the ad mentions that the large tires would cause trouble on the highway.. why? :confused:

 

Mostly, I'm betting it's a lousy ride. Most subies have a lot of road noise...I imagine the tires on this thing make it even worse. Knobby tires always do.

 

RB

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but the ad mentions that the large tires would cause trouble on the highway.. why? I would imagine that if you could use the low range to get up to a reasonable speed, then shift into normal range, the tires would essentially serve as a mega overdrive, and wind up simply giving you superb highway fuel mileage???? Am I totally misconceived on that? Is there something about the lifted subaru on swampers that is simply unstable at highway speeds, beyond the gearing that I am not aware of? I am not understanding the highway problem with this vehicle... :confused:

 

Not in practice.

 

The larger tires will make it hard to accelerate, and they give a much larger rolling resistance. You end up with 20 MPG or less on a rig lifted like that, and virtually no power. Top speed on that thing is probably around 50 to 60 MPH. Passing is not happening, and any kind of hill will result in a high RPM 3rd gear pull. Been there, done that.

 

Unstable.... well a little. If it's done right (looks like possibly) then it's got no sway bar. And the larger offset and huge tires make the steering very sensitive, and any rut in the road yanks the car around a bit as the mechanical advantage of the stock steering wasn't set up to handle those kind of large forces. So you end up driving slow, and it's sometimes a white knuckle sort of affair.

 

GD

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I would imagine that if you could use the low range to get up to a reasonable speed, then shift into normal range, the tires would essentially serve as a mega overdrive, and wind up simply giving you superb highway fuel mileage???? Am I totally misconceived on that? Is there something about the lifted subaru on swampers that is simply unstable at highway speeds, beyond the gearing that I am not aware of? I am not understanding the highway problem with this vehicle... :confused:

 

As GD says, not in practice. Due to the high gearing (and other factors, described below), the engine is being overworked. So, even though it's running at lower RPM (which, in the right situation, equals fuel savings) it's having to work so hard that it uses more fuel.

A good example is the 1962 Chevy C50 wrecker a friend used to use. It originally had a 292 Chevy six- they swapped to a 350 after a few years, then went to a 454. Each engine change improved their fuel mileage, even though they were increasing engine size. Of course, being a 454, the mileage was still horrendous:grin:

Increased tire diameter isn't the only thing contributing to the engine having to work harder- add in the increased rolling resistance of the aggressive tread pattern, along with the increased weight of the larger wheel/tire combo, and the poor little boxer ends up with quite a job to do. Lifting a vehicle increases it's wind resistance too, so that has to be factored in. Even if you lived in a totally flat area, had 31" tires with the same tread pattern as the stock tires, and magically lightened your wheel/tire combo to match the weight of the stockers, you'd most likely still get worse mileage than stock.

Andy

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so essentially, in addition to the additional resistance from the knobbly tires, and the unsprung weight, etc..

 

..the entire "gearing" thing is actually a parabolic function as opposed to a simple square or linear function then? I mean, smaller tires hurt fuel mileage and larger diameter helps.. but only to a point, and then once you get beyond that any increase essentially kills you. Right?

 

This is an end of the automotive spectrum I have NEVER EVER played with, so i have zero real world experience.. Even when it comes to sports cars, if someone GAVE me a set of 18" wheels for my Datsun I would sell them in a HEARTBEAT but hesitate long and hard before they went on the car...

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The larger tires will make it hard to accelerate, and they give a much larger rolling resistance. You end up with 20 MPG or less on a rig lifted like that, and virtually no power. Top speed on that thing is probably around 50 to 60 MPH. Passing is not happening, and any kind of hill will result in a high RPM 3rd gear pull. Been there, done that.

To which I will add that the weight of each tire/wheel will noticably increase stopping distances, due to the greater amount of rotating mass that must be brought to a halt. I had 28" Wildcats on two subes, an 84 wagon and a 91 Loyale, both lifted 3". Each tire/wheel weighed 52 lbs, vs. about 28-30 lbs for a normal 13" tire/wheel. Even with 185/80-13" Kumhos on the Loyale now, the tire+wheel weighs 32 lbs. (aluminum wheel).

 

There may also be shimmy and vibration issues. On the 84 they were fine, but on the 91 they shimmied at highway speeds, unless I aired them up to the point where they vibrated! A 6" lift on these cars demands 31" tires to look right, but overall function of the vehicle suffers.

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