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Wayne,
I wish I would have listened to you before when we discussed tires for the Del Sol. But I needed tires that were good in the snow for the winter. Now that warmer weather is on the way, I took your advice and ordered the Potenza RE 92's in the OEM Insight size of 165/65/14. I will also be picking up a set of used 14" Civic HX Aluminum Wheels this weekend. The wheels are 12 lbs each and the tires are 12.7 lbs each, total under 25 lbs for each wheel and under 100 lbs for the set. That is a 36 lb reduction in unsprung weight compared to my current tires. The tread width is 5.0" vs 5.6 so over 10% reduction in contact patch. Also, with the higher 44 PSI rating, I will press them up to 60PSI vs 47PSI currently.

The only downside is that thesetires have poor wet and snow traction. But with my driving style, it shouldn't matter much. I am keeping my fingers crossed for a 2 MPG gain. Wish me luck!:D

Nice job, Krous.......... excellent choice. Those HX wheels are super, I used to have some for snow tires. I cleaned them up, then put 3 coats of wax on both sides of the wheel. Yeah, that will give you a winning combination. I would think, however, that it will be much easier to see a measurable FE increase on longer trips, longer runs, not short ones. Billy...

Nice job, Krous.......... excellent choice. Those HX wheels are super, I used to have some for snow tires. I cleaned them up, then put 3 coats of wax on both sides of the wheel. Yeah, that will give you a winning combination. I would think, however, that it will be much easier to see a measurable FE increase on longer trips, longer runs, not short ones. Billy...

Thanks Billy! So now I can get 80+ MPG like you? I shoulduve done this a long time ago!:D

I predict a 5 mpg increase.

No Prediction here, I will wait and see and hear from the Horse's Mouth. :D

Sounds like a very sound combination to me though.

Hey, the HX rims are 11.75 pound each according to the UPS scale I stacked all 4 of mine on. LOL. Actually I had two sets of HX wheels for a while, one for street driving and one with my Kumho V700 autocross tires mounted up on them. I always liked them, but ended up going to 15x6" Integra GSR wheels a couple years ago because I liked how they looked better. :)

Woot! 11.75 each means that I just lost another pound of unsprung weight. Next I will cut the ends off of my lugnuts!:D

Now you are putting some real thought into this. Quote:Next I will cut the ends off of my lugnuts!

It's about time that you are taking this "Serious", I wondered how long it would take you. ;)

Hi Dan:

___I thought 70 was about the max you would see out of your del Sol and I have been proven wrong already! Although I have no idea where you will end up by mid-summer, I do know you are doing a great job for both yourself and us as well.

___I do have one prediction that might be worth your while however. I think you will leave the Insight’s RE92’s on year round given you know your capabilities and there’s.

___I wonder if I could cut the top off my Accord and replace it with a sheet of cardboard at steering wheel level to reduce my frontal area and lower the weight by maybe 150 #’s or so ;)

___Good Luck

___Wayne

Woot! 11.75 each means that I just lost another pound of unsprung weight. Next I will cut the ends off of my lugnuts!:D
Actually I was imagining your next mod would be to put a giant slab of clear plastic going from the rear roofline of your car to the rear of the trunklid to clean up the aero from that completely vertical rear window the del Sol has. That's gotta be worth something.

This is prolly the best thread to put this in. My latest built in FE mod was to replace the 15" wheels and tires with 14" HX and Insight rubber. Here is what the car looks like now...
http://img90.imageshack.us/img90/3208/dcp60343ci.jpg (http://imageshack.us)

The tire diameter is 2" less than the previous tires so the car is 1" closer to the ground as a result. The old wheel/tire weighed 34.5 lbs each, the new ones are 24.4 lbs each for total unsprung weight reduction of 40 lbs!

I made a quick calculation and changed the SuperMID distance parameter before going out to finalize the calibration by 40 miles of highway driving via the milepost method. After another small tweak, methinks I am calibrated.

Initial driving impressions...
Good stuff
- Easier to steer, less rubber on the road
- Easier to start from a stop and easier to accelerate according to the buttometer
- Quieter ride, bumps are less sharp even at 62 PSI.
- Rolls much farther when coasting
Bad stuff
- Less rubber on the road
- Cornering ability greatly diminished, oversteer !!!
- Nearly spun out on two occasions, need to reduce speed on curves
- I can only imagine what it will be like in the rain.

Initial FE impressions...
- Good stuff
- The trip to the inlaws was 73MPG (warm start) vs 62MPG (cold start) (pre belly pan) similar temps (52F) and winds.
- The trip around the park was 82.9 MPG vs 72.0, again similar conditions although I made one of the lights this time.

So far I am happy as long as I don't kill myself on a guardrail. We shall see what the commute data looks like. Next two days should be dry and moderate temps.

Actually I was imagining your next mod would be to put a giant slab of clear plastic going from the rear roofline of your car to the rear of the trunklid to clean up the aero from that completely vertical rear window the del Sol has. That's gotta be worth something.

It would be worth more if i spent more time at highway speeds. Currently only 1/4 of my commute is above 35 MPH.

I am thinking about how to do that mod however and will try out Insight style rear wheel covers too. But anything that would cover the trunk lid would have to be easily removeable. That is where the top goes on nice days.:D

I ran a test a few weeks ago with the top off and the results, while not scientific, lead me to believe that at under 40MPH, top off doesn't reduce FE measureably. Possibly because there is turbulence over the trunk anyway so more turbulence doesnt make it that much worse.

Another downside is that your engine now must spin higher RPM for any given roadspeed in 5th gear. At 2 inches on a 24" tire, we're talking about at least an 8% increase in engine speed for any given roadspeed. Ouch! Anyway, I guess in light of the fact you never get going to significant speeds anyway, perhaps it won't hurt you so much since you're going so slow anyway and the main enemy of the old setup was the rolling resistance rather than aero drag or engine speed.

Yes, rpms are up which does offset some of the gains by switching tires. My next mod will be a CX tranny swap. The final drive will go from 4.06 to 3.25 and will more than offset the smaller tire size. Hopefully over the summer I will get that done.

What a beautiful day for a drive! 72F, sunny and 5-10MPH southerly wind. So I decided to take the top off. ****ed the aerodynamics I say! Just for good measure I rolled the rear window down all the way.

Woot! 65.45 MPG! That is another best for the trip home by 2.5MPG and the first time that my return trip was higher than my drive to work. Today's round trip was 65.23 MPG.

Current tank, 240 miles, 63.47 MPG. :)

The tires seem to be breaking in nicely. I read something over at tire rack that says it takes several hundred miles (or was it 1000?) for tires to shed the oils that are used to release them from the mold. I havent had any more understeer problems and am slowly taking corners faster to find the limit. The tires are much quieter than the Kumhos and even though they are 12PSI higher, they absorb the bumps much better. Smoother, quieter, better MPG (guestimated at 2-3). I can live with that just fine. Maybe I will get another 1 or 2 MPG when they fully break in. I am happy with my investment and the look of smaller tires and the HX rims is really growing on me. Anyway after my MPG stabilizes i will swap tires again to see how much it effects FE. Should be interesting.

Anyway no more updates until next Tuesday for the del sol although I will be online. Im off to Myrtle beach with the family for spring break. We will have the prius but in deference to the family who just wants to get there ASAP, I will be driving blindingly fast, approaching 75MPH at times. Hoping for 48MPG in the fully loaded Prius under those conditions. And if they make me turn on the AC, it goes downhill from there.:(

how fast you go over your bumps Dan? When looking at the side of my tires it seems to be ripping apart, maybe I'm taking the bumps too harshly?

http://img150.imageshack.us/img150/9389/sonandoutsidecar053large8wg.th.jpg (http://img150.imageshack.us/my.php?image=sonandoutsidecar053large8wg.jpg)

http://img99.imageshack.us/img99/4075/sonandoutsidecar052large8su.th.jpg (http://img99.imageshack.us/my.php?image=sonandoutsidecar052large8su.jpg)

how fast you go over your bumps Dan? When looking at the side of my tires it seems to be ripping apart, maybe I'm taking the bumps too harshly?

I go iver thousands of bumps every day at all different speeds. The roads here suck.:mad:

so for sure if you found a road that gave you great mpg but you go over so many bumps and traintracks for it then you'd reconsider right? Do you ever slow down for a bump at all or always at whatever velocity your travelling at? Also do you dodge potholes? or the decreased momentum due to steering is not worth it ;)?

I'm just trying to juggle wear and tear vs mpg here.

how fast you go over your bumps Dan? When looking at the side of my tires it seems to be ripping apart, maybe I'm taking the bumps too harshly?
Looks normal to me. Are you talking about the smaller sipes? Those appear to be part of the tread design.

http://www.tirerack.com/tires/BigPic.jsp?tireMake=Dunlop&tireModel=SP20+FE&sidewall=Blackwall

how much longer (in miles) you guys think i can scretch these tires out before replacing? or do i just have to feel when its not safe to drive with them anymore?

so for sure if you found a road that gave you great mpg but you go over so many bumps and traintracks for it then you'd reconsider right? Do you ever slow down for a bump at all or always at whatever velocity your travelling at? Also do you dodge potholes? or the decreased momentum due to steering is not worth it ;)?

I'm just trying to juggle wear and tear vs mpg here.

I always dodge potholes but never slow down for bumps. I know where all the bumpa and potholes are so I dont have to dodge much. Usually bumps can be lessened by moving over to the left or right.

Your tires look fine. My last set of Prius tires I ran practically bald. Since I drive slow and anticipate traffic conditions, I dont need my tires to do anything except to stay inflated to 62 psi. I just had to be more careful in the rain. I put new tires on the prius last winter due to poor snow traction.

Hi Dan:

___Now that you have a few thousand miles on your RE92’s, has the traction improved somewhat now that they have been scrubbed? I never thought the RE92’s were a problem in the traction area other then in heavy rain and light snow and even then, I was always so gentle with the Insight that high traction driving situations were never really an issue.

___Good Luck

___Wayne

Hi Dan:

___Now that you have a few thousand miles on your RE92’s, has the traction improved somewhat now that they have been scrubbed? I never thought the RE92’s were a problem in the traction area other then in heavy rain and light snow and even then, I was always so gentle with the Insight that high traction driving situations were never really an issue.

___Good Luck

___Wayne

Well I only have about 300 miles on them due to a vacation and a few days sick. I first put them on on 4/10. I have not had any traction issues other than on the first day but I have also kept my speeds lower around the corners. One thing is for sure, they appear to be worth 3-5 MPG. Hopefully more when they are properly scrubbed.

I just posted my latest tank, another 66 MPG. My last seven tanks (starting when I got the RE 92's) have ranged from 64 to 67, averaging 65.67 over 2400 miles. Looks like I have hit the wall. At least I finally hit the 60% over EPA mark.:D

Before the RE 92's my best tank was 60.60, 58.88, 56.94 and 54.41. True, the temps were on average 20F cooler and the winter fuel plays a role in the lower FE, but I suspect that the tires had the most influence on the FE gains.

The best way to isolate the effect of the tires would be to look at the last tank with the old tires and the first tank with the new tires. The week over week temp in April wasn't that large and I was still on the Winter fuel at the time. So 64.649-60.607 = 4.042 MPG. I think this is a close approximation of the icrease due to the new wheels and tires. The subsequent gains to 65-66 MPG tanks is probably due to summer fuel, warmer temps and tire break-in.

And as I have mentioned before, the tires have broken very nicely and now have better traction than the previous tires. It was a win-win for me.

I just posted my latest tank, another 66 MPG. My last seven tanks (starting when I got the RE 92's) have ranged from 64 to 67, averaging 65.67 over 2400 miles. Looks like I have hit the wall. At least I finally hit the 60% over EPA mark.:D

Before the RE 92's my best tank was 60.60, 58.88, 56.94 and 54.41. True, the temps were on average 20F cooler and the winter fuel plays a role in the lower FE, but I suspect that the tires had the most influence on the FE gains.

The best way to isolate the effect of the tires would be to look at the last tank with the old tires and the first tank with the new tires. The week over week temp in April wasn't that large and I was still on the Winter fuel at the time. So 64.649-60.607 = 4.042 MPG. I think this is a close approximation of the icrease due to the new wheels and tires. The subsequent gains to 65-66 MPG tanks is probably due to summer fuel, warmer temps and tire break-in.

And as I have mentioned before, the tires have broken very nicely and now have better traction than the previous tires. It was a win-win for me.
Dan,

Looks like those Tires are working for (You), Congrats. :D

I would like to give you a (Two-Thumbs-Up) from the Icons but we don't have them in our list. :(
So just picture a 2-Thumbs up anyway. :)

Terry