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UnCivic · 11-09-2009, 10:35 AM

Okay, I put about 600 miles on the Civic with the 185/65/15's

Contrary to all preconceived logic, the net efficiency result with the 4% correction, was only 30 mpg.

I was getting 35mpg before? Why did I loose almost 5mpg?

1. To make smooth shifts the PRM’s had to be taken up higher. This applied to all gears, but was especially the case from 1st to 2nd. Normally, when driving with a light foot, I could shift from 1st to 2nd around 2500rpm without a problem. With the larger OD setup, shifting at anything less than 3000rpm resulted in unsatisfactory bog-down when taking 2nd gear. This resulted in more lead-footed in 1st gear takeoffs and more cruising around parking lots and side streets in 1st gear.

2. 2nd, 3rd gears got used a lot more for regular driving. 4th gear became the new highway gear in traffic. 5th gear was great above 60 mph on flat roads or downhill. However, it was pretty useless for going up any long hills or for driving in traffic.

Other points of interest were:
1. The car felt like it was a bigger car. That was kind of neat.
2. Brake action changed a lot. There was a good bit of initial fade. However, the wheels didn’t lock up as easily so I could apply much more braking force. I can’t say if the net result was better or not.
3. The 185/65/15 were way too floaty for my liking. For driving on anything-but-smooth Pittsburgh roads, my preference is for the 50 to 60 aspect ratios. For a larger OD setup, something like 195/50/16’s might feel a lot better. However, I have never seen 16” wheels with 195’s mounted to them.
4. Rubbing was about the same as with the 195/60/15’s. It only happened a couple of times while maneuvering in a parking lot or doing fast turnouts onto main roads.
5. Having to keep the revs up higher to shift meant that I probably drove faster.
6. 2nd gear went all the way to 70mph!. That was kind of fun.
7. 3rd gear pulled "well" from 70 to 80, but that was it. Not enough torque.
8. Top speed was only around 90mph. It would only go faster on the downhills.
9. I think that this setup could work in the case where most driving was on flat ground, or in a car with a larger engine with more than 80 ft-lbs of toque.

It was an interesting experiment, but the Civic was more than glad to have the 195/60/15’s put back on.

11-09-2009, 10:35 AM	#29 (permalink)
UnCivic EcoModding Lurker Join Date: Sep 2008 Location: Pittsburgh, PA Posts: 17 Thanks: 0 Thanked 2 Times in 2 Posts	The Verdict... Okay, I put about 600 miles on the Civic with the 185/65/15's Contrary to all preconceived logic, the net efficiency result with the 4% correction, was only 30 mpg. I was getting 35mpg before? Why did I loose almost 5mpg? 1. To make smooth shifts the PRM’s had to be taken up higher. This applied to all gears, but was especially the case from 1st to 2nd. Normally, when driving with a light foot, I could shift from 1st to 2nd around 2500rpm without a problem. With the larger OD setup, shifting at anything less than 3000rpm resulted in unsatisfactory bog-down when taking 2nd gear. This resulted in more lead-footed in 1st gear takeoffs and more cruising around parking lots and side streets in 1st gear. 2. 2nd, 3rd gears got used a lot more for regular driving. 4th gear became the new highway gear in traffic. 5th gear was great above 60 mph on flat roads or downhill. However, it was pretty useless for going up any long hills or for driving in traffic. Other points of interest were: 1. The car felt like it was a bigger car. That was kind of neat. 2. Brake action changed a lot. There was a good bit of initial fade. However, the wheels didn’t lock up as easily so I could apply much more braking force. I can’t say if the net result was better or not. 3. The 185/65/15 were way too floaty for my liking. For driving on anything-but-smooth Pittsburgh roads, my preference is for the 50 to 60 aspect ratios. For a larger OD setup, something like 195/50/16’s might feel a lot better. However, I have never seen 16” wheels with 195’s mounted to them. 4. Rubbing was about the same as with the 195/60/15’s. It only happened a couple of times while maneuvering in a parking lot or doing fast turnouts onto main roads. 5. Having to keep the revs up higher to shift meant that I probably drove faster. 6. 2nd gear went all the way to 70mph!. That was kind of fun. 7. 3rd gear pulled "well" from 70 to 80, but that was it. Not enough torque. 8. Top speed was only around 90mph. It would only go faster on the downhills. 9. I think that this setup could work in the case where most driving was on flat ground, or in a car with a larger engine with more than 80 ft-lbs of toque. It was an interesting experiment, but the Civic was more than glad to have the 195/60/15’s put back on.