Wheel and tire change, any FE improvement here?

[MetroMPG]

Originally Posted by 90crxHF

Guys, I'm worried about the steel Honda wheels being way heavier than what I'm currently running and potentially making my MPG worse.

Not going to be an issue in highway driving.

That's what you're setting this car up for, right?

Also the issue is more complicated that simple weight. Mass distribution of the 15's - more mass toward the outside - could potentially be less favourable than 13's or 14's. (Someone feel free to correct me on that - just something I read elsewhere that makes sense.)

[mwebb]

did you calculate in a fudge factor to allow for the difference in OD when making the FE comparison between the
155x80x13 versus 195x50x15 tire wheel combination ?

are you thinking the change in 1/4 mile times are a direct result of
increased mass of the wheel tire assembly
or
increased aero drag of the wider tires / wheels
or
change in final drive ratio due to larger OD of the 15" wheel / tire ?

i have the same car and of yet un installed 15" alloy acura legend wheels with 195 60 15 tires

Originally Posted by ATaylorRacing

I'd suggest going to some 155x80x13 tires on American Racing Estrella rims. I went from that size 13 to the 195x50x15 tire/rim package on my Geo Metro 3 banger and the tire/rim pacage is 8 lbs heavier per corner. The old tires had a max tire pressure of 35 while the new ones would take 51.

In the end the gas mileage on flat ground/highway speeds remained the same due to much less rolling resistance, BUT the 1/4 mile times went from 19.9s normally to 20.6s.

When the weather gets warmer I will return to the 13 set up. The Power Star 13" tires are 14 lbs while my Estrellas in 15" are 18 lbs. My 15 inch rims are 16 lbs while the Am Racing 13s are 12.8...BUT, the newer 13s can take more tire pressure than my old ones. Going back to my 1/4 mile ets, I did take an extra 32 lbs out of the car to make the wt the same as it was earlier with the 13s. When I go back to the 13s I will loose anoth 32 lbs so that my new wt will be 1598 compared to the present 1630. I have taken 132 lbs out of it, but added 32.

Another idea I was thinking about was to keep my 15s, but go to the 175x55x15 size that are 4 lbs lighter and less costly than a new tire AND rim set up!

[ATaylorRacing]

Originally Posted by mwebb

did you calculate in a fudge factor to allow for the difference in OD when making the FE comparison between the
155x80x13 versus 195x50x15 tire wheel combination ?

are you thinking the change in 1/4 mile times are a direct result of
increased mass of the wheel tire assembly
or
increased aero drag of the wider tires / wheels
or
change in final drive ratio due to larger OD of the 15" wheel / tire ?

i have the same car and of yet un installed 15" alloy acura legend wheels with 195 60 15 tires

The 155x80x13s were 22.8" in dia while the 195x50x15s are 22.7, a difference of only .2%....and even though tiny I correct the miles per tank to reflect the shorter tires...for example every 100 miles traveled is really 99.8.

The 1/4 ets are slower due to the extra wt of the tire/rim combo...not aero drag because the car aero was cleaned up better with a grill block and headlight covers. The new aero mods made the top speed on the hiway rise from 81 to 87 mph! The slower ets were not caused by the difference in tire diameer because the 15s are a bit smaller and should have helped a quicker et.

As for putting 195x60x15s on your car you might run into clearance troubles. That size is 24.2" in diameter, and if your speedo says 60 you will be really doing 63.8 or a error of 6.3%. If I am on a undulating country road I can hear my LR tire barely scrape the fenderwell...your problem will be MUCH worse due to the much larger dia of those 60 series tires. If you think you'll get better mpg because of the larger dia you will also need to figure in that the 195x50x15 tires are about 5 lbs heavier each than the stock 13s.

Here's a link to what my stuff looks like, and the cars I race against:

Even the 3 cylinder Geo gets action
UMTR Nationals at Edgewater - 9/26/09 - Hyper-Performance Motorsports Inc. Photography
The White Gnat strikes again
UMTR Nationals at Edgewater - 9/26/09 - Hyper-Performance Motorsports Inc. Photography

[90crxHF]

Originally Posted by MetroMPG

Not going to be an issue in highway driving.

That's what you're setting this car up for, right?

Also the issue is more complicated that simple weight. Mass distribution of the 15's - more mass toward the outside - could potentially be less favourable than 13's or 14's. (Someone feel free to correct me on that - just something I read elsewhere that makes sense.)

Yes, I do like 90% highway with this car.

Oh and BTW, I got the 14x5.5" and I've already mounted them on the car. They fit great, now onto some Moon Eye covers...

I've found them online for like $85 for the stainless steel ones, anyone know of anything cheaper?

And BTW, Firestones on these wheels can take 44psi. What MPG difference would it make from 36PSI to the 44PSI? I guess only real world testing will tell, considering all the other variables... I try to drive as consistently as possible so my numbers are the least amount skewed....

Also, what size tire should I put back on these?? And if there is a 14" tire recommendation, please let me know. I've been looking at 175/70/14...

EDIT: There seems to be no difference in accelaration, and considering I don't drive fast anymore, it really doesn't matter....

[Ryland]

If you get the 165/60 R14 tires that the insight has they will be Low Rolling Resistance tires, also you should be able to get the lighter aluminum moon disc hub caps for around $100 used.

[moonmonkey]

look at some of the pizza pan mods you would be surprised how good they can look.

[90crxHF]

Originally Posted by Ryland

If you get the 165/60 R14 tires that the insight has they will be Low Rolling Resistance tires, also you should be able to get the lighter aluminum moon disc hub caps for around $100 used.

Dang, that will put me at 3600rpms at 70mph... With the 195/50-15 I was at 3400rpm at 70mph, and now with these 185/70-14 I'm at around 3200rpm at 70mph. I guess it really won't make much difference since I'm driving more around 60-65mph on the freeway now. I occasionally hit 70mph, but really only going downhill now.

Thanks so much for the replies guys. I will look into the pizza pan moon disc mod. I've already been thinking of doing that anyways, probably much cheaper, but I don't want it to look cheap. Know what I mean?

[90crxHF]

Okay guys, I'd like to report that I have now hit solidly in the 40's MPG wise... With this tire change I have now hit 41.35 MPG. This is running the tires mostly around 34 PSI. How much of a MPG improvement does pumping them up to say 40 or 44 PSI do? Would I see another 1 to 2 MPG? If so, I might try it and run my Illumina's on setting 1.

Oh BTW, I'm using the stock 2003 hub caps on the steel wheels. They seem pretty decent for aero, besides I waxed the crap out of them. I might eventually get the moon discs.

[Mifunego]

Originally Posted by 90crxHF

Okay guys, I'd like to report that I have now hit solidly in the 40's MPG wise... With this tire change I have now hit 41.35 MPG. This is running the tires mostly around 34 PSI. How much of a MPG improvement does pumping them up to say 40 or 44 PSI do? Would I see another 1 to 2 MPG? If so, I might try it and run my Illumina's on setting 1.

Oh BTW, I'm using the stock 2003 hub caps on the steel wheels. They seem pretty decent for aero, besides I waxed the crap out of them. I might eventually get the moon discs.

I've been researching wheels lately, as I plan to replace my stock 18" boat anchors when the tires wear out (wheels are 24 lbs each, stock!) I've got my eye on the Enkei RPF1 also, since they are so light. Are you still running the steel wheels? Did you really see a mileage increase when you swapped out the 15" Enkeis? I see that the 15x7s are specced at a staggering mere 9.5 lbs each! That's amazing. The 18 x 7.5 RPF1s for my car run 17.6 lbs, and the 17 x 7.5 are only 15.2 lbs (big for you, but a huge unsprung weight diet for me). I also see you have one car for high mileage, and one for high speed Unfortunately, living in the high-cost socialist city of Chicago makes it difficult for me to support too many cars (2 is enough for now), so my DD has to suffice as my track toy also - all the more reason for the RPF1s.

[2win2rbo]

I am not really sure about putting steelies on mine. The 14 inch ones are way heavier than my 15s.