getting bigger rims = odometer/speedometer changes? - Toyota Yaris Forums

songa · 11-26-2008, 12:52 AM

hey guys, i just wanted to get a couple things straight...my yaris came with the 15" steel wheels, and I am thinking about replacing them for 17" rims. however, if I do install 17" rims, doesnt that mean that my speedometer will be reading slower than my actual speed, and my odometer be less than my actual distance traveled?

if this is true, is there any way to recalibrate these meters to reflect the new change in wheel diameter? does anybody have experience with this?

since i have 15" wheels, i can replace them for 15" rims without having to worry about the odo/speedo issues, right?

last question...lowering your car doesnt have any affect on odo/speedo, or fuel economy, right?

id appreciate any quetsions you can answer! thank you!

ddongbap · 11-26-2008, 07:49 AM

http://www.miata.net/garage/tirecalc.html

Theres an area where you can type stock, and aftermarket tire size. Then it'll tell you the difference in percentages. It'll also tell you what the difference in the speedometer it'll show.

Long story short; as long as the outer diameter of the rubber, not the rim, is the same, then you will not have any problems. Though there are rarely EXACT rubber sizes that would be the same on a 15 and 17 inch. They'll come pretty damn close. I was looking at 215s for 16 inches, but the closest I've gotten to was around >1% in size difference.

Technically, lowering your car won't have any effects on your fuel economy. Technically. Lowering your car may have adverse effects on your alignment, and through that, you'll get difference in fuel economy. For example, if your toe happens to change slightly, it'll create some drag on the tires. Since the tires would try to pull away at different directions. Though most of this is only technically.

songa · 11-26-2008, 10:11 AM

thanks man, thats some good informatino. i found some 17" combos that would result in a 0.1% difference, but ive decided that even that small amount is too much. id rather have it all exact, because im very concerned about fuel economy and would like to know the exact # of miles ive traveled over time. and if you're 0.1% off, the more miles you drive, the more wrong the number will get.

what are the dimensions of the stock tires on the yaris? i got the regular sedan, but it has the package that includes the 15" steel wheels with full wheel covers. is that a P185/60/R15 size?

has anybody replaced their stock 15" steel wheels for 15" rims, but using the stock tires? right now thast what im most interested in doing. as for lowering the car, im still unsure of becuase im really afraid of bottoming out in thsee horrible boston roads...

CASTREX · 11-26-2008, 02:06 PM

You are really into the MPG and you are getting 17's???

a 0.1% diff is minimal....

If you are really interested on your MPG you should stay with 15" wheels. But if you really want larger tires. Try to get the lightest wheels you can find.

The wheels weight on such a small engine make a big difference.

songa · 11-26-2008, 02:45 PM

thanks for the input. well i really dont know much about cars, esp. stuff like how wheels affect fuel economy, etc. so i was just tyring to find out more information about them. 0.1% difference is minimal but over a long distance, the odo will be reading a value much less than what you actually traveleed, right?

in any case, i probably will end up getting 15"

thanks guys

CASTREX · 11-26-2008, 04:17 PM

Quote:

Originally Posted by songa

thanks for the input. well i really dont know much about cars, esp. stuff like how wheels affect fuel economy, etc. so i was just tyring to find out more information about them. 0.1% difference is minimal but over a long distance, the odo will be reading a value much less than what you actually traveleed, right?

in any case, i probably will end up getting 15"

thanks guys

0.1% is way inside the margin of error of your speedometer.

The general recommendation is not to exceed +/- 3% tire size diff.

Also, you will track you MPG over the distance driven on one tank of fuel right?

So, if your tank goes for 350 miles. 0.1% of 350 miles= 0.35 miles.

If your car does 40 mpg that means a difference of 0.00875 gallons per tank.

Again, 0.1% is nothing

songa · 11-26-2008, 04:25 PM

yes that makes sense, thanks. and also, you're right...even after 35,000 miles, you will only be 35 miles off....so say you drive 105,000 miles (close to the end of the life of the car), you'll only be 105 miles off on the odometer...still not that big of a deal. thanks for the clarification castrex!

this brings up one other question...you said that fuel economy will suffer if i get the 17" rims. how much will it suffer, and why? i currently avg around 37mpg. on 17s, will it go down to like the low 30's?

ddongbap · 11-26-2008, 09:18 PM

Quote:

Originally Posted by CASTREX

0.1% is way inside the margin of error of your speedometer.

The general recommendation is not to exceed +/- 3% tire size diff.

Also, you will track you MPG over the distance driven on one tank of fuel right?

So, if your tank goes for 350 miles. 0.1% of 350 miles= 0.35 miles.

If your car does 40 mpg that means a difference of 0.00875 gallons per tank.

Again, 0.1% is nothing

Paper MPG and actual MPG can't be rated the same as difference in tires sizes. You never know, the 1% difference may help the MPG.

You also gotta look at the larger picture. 350 miles is probably a tank of gas.

You gotta compare it to 1000, 10000 or so miles. It'll add up. But 1% doesn't bother me personally. Cause IDC either way, since I plan on keeping this car forever. Or till I run it to the ground.

Btw, you have to weigh the entire package. Rims with tires. I don't know how 15 inches get better gas mileage, but weight is weight. Though you gain more metal, in 2 inches you lose 2 inches in tire. I'm not sure which weighs more, but one thing for sure, if you get WIDER tires you'll surely get a ding in gas milage.

CASTREX · 11-27-2008, 12:43 AM

Quote:

Originally Posted by ddongbap

Paper MPG and actual MPG can't be rated the same as difference in tires sizes. You never know, the 1% difference may help the MPG.

You also gotta look at the larger picture. 350 miles is probably a tank of gas.

You gotta compare it to 1000, 10000 or so miles. It'll add up. But 1% doesn't bother me personally. Cause IDC either way, since I plan on keeping this car forever. Or till I run it to the ground.

.

I agree... is just that he said a diff of 0.1% not a diff of 1%.

A 1% is small but a diff of 0.1% is almost non existent!

CASTREX · 11-27-2008, 12:52 AM

Quote:

Originally Posted by songa

yes that makes sense, thanks. and also, you're right...even after 35,000 miles, you will only be 35 miles off....so say you drive 105,000 miles (close to the end of the life of the car), you'll only be 105 miles off on the odometer...still not that big of a deal. thanks for the clarification castrex!

this brings up one other question...you said that fuel economy will suffer if i get the 17" rims. how much will it suffer, and why? i currently avg around 37mpg. on 17s, will it go down to like the low 30's?

Your MPG drop won't be that drastic. Maybe 2-3 MPG less by going from 15 to 17.

The reason is basically the weight... The weight of the wheels is not simple dead weight. Is spun weight. A wheel is a rotating mass... So that weight has a big impact on the acceleration. If you have a very heavy 17 wheel your engine will have to use more energy to make them rotate. As simple as that.

Another reason is that usually 17 wheels will use wider tires. 205 or 215 wide. That also means more drag. A larger contact area means more friction.

Is all a compromise!

Ryu · 11-27-2008, 01:13 AM

Quote:

Originally Posted by CASTREX

Your MPG drop won't be that drastic. Maybe 2-3 MPG less by going from 15 to 17.

The reason is basically the weight... The weight of the wheels is not simple dead weight. Is spun weight. A wheel is a rotating mass... So that weight has a big impact on the acceleration. If you have a very heavy 17 wheel your engine will have to use more energy to make them rotate. As simple as that.

Another reason is that usually 17 wheels will use wider tires. 205 or 215 wide. That also means more drag. A larger contact area means more friction.

Is all a compromise!

^^ What he said.

Also even if you go with 15" wheel, there are some heavy one and light one as well.
Don't get blinded by just the size of the wheel itself.

I found this site quite useful of finding out the weight of the wheel and the weight of your tire as well. Go to any wheel or tire you desired and hit on the spec button.
www.tirerack.com

songa · 11-27-2008, 03:32 AM

thanks guys for all that info. quick question tho..does anybody know how much the stock 15" steel wheels weigh?

Ryu · 11-27-2008, 09:28 AM

Someone post it before the hack, I think it is 14" steel wheel for 14lb and 15" for 15 lb.
It is almost like 1:1 ratio for size of the wheel and weight.

I read it here that OEM hub cap weigh 2.5 lb as well from this thread http://www.yarisworld.com/forums/sho...t=10923&page=3

Quote:

Originally Posted by Snyprwlf47

I actually weighed my hubcaps and they were an unnecessary 2.5 Lbs....

yarstar · 11-27-2008, 10:19 AM

I went from the stock 15" wheels/tires to 17" Enkei aluminum wheels with 205/40/17 tires. The difference in MPG was significant. I went from 37-39 MPG to 30-34 MPG. I don't mind though because the wider tires give a major amount of traction and cornering ability to the car. I'm cool with 30+ MPG in a car I run like a scalded dawg.

The main issue is as mentioned before, rotational weight. The secondary issue is rolling resistance caused by more rubber touching the road. Increased tire pressure can help this but then traction is compromised.

I've debated using the Konigs with the stock tires. I think this may give more acceleration but also keep MPG. Of course I'll loose the cornering I now have, but I'd like to see more accel out of my vehicle right now instead of cornering performance.

It all comes down to what you want out of the car. You are limited with what a Yaris is capable of. IMO, you can't get both.

bzinn 1 · 11-27-2008, 01:43 PM

I went from the stock 14" to 17" and my MPG has only dropped 2MPG.....and I can live with that.My rim/tire setup now is only 2lbs heavier than the stock setup.add the hub caps to the stcok rims and I am about the same weight.

Bigger tire width though is most likely where I am losing ground as it has more drag than the skinny stock tire.

Find a good quality rim that is with the tire going to weigh near the same as the stock rim and tire and you will notice very little differance.

11-26-2008, 12:52 AM	#1
songa View User's Garage Drives: 2009 Yaris Sedan (Black) Join Date: Nov 2008 Location: MA, USA Posts: 139	getting bigger rims = odometer/speedometer changes? hey guys, i just wanted to get a couple things straight...my yaris came with the 15" steel wheels, and I am thinking about replacing them for 17" rims. however, if I do install 17" rims, doesnt that mean that my speedometer will be reading slower than my actual speed, and my odometer be less than my actual distance traveled? if this is true, is there any way to recalibrate these meters to reflect the new change in wheel diameter? does anybody have experience with this? since i have 15" wheels, i can replace them for 15" rims without having to worry about the odo/speedo issues, right? last question...lowering your car doesnt have any affect on odo/speedo, or fuel economy, right? id appreciate any quetsions you can answer! thank you!

11-27-2008, 10:19 AM	#14
yarstar View User's Garage Drives: 2008 Absolute Red HB Join Date: Oct 2008 Location: Georgia Posts: 264	I went from the stock 15" wheels/tires to 17" Enkei aluminum wheels with 205/40/17 tires. The difference in MPG was significant. I went from 37-39 MPG to 30-34 MPG. I don't mind though because the wider tires give a major amount of traction and cornering ability to the car. I'm cool with 30+ MPG in a car I run like a scalded dawg. The main issue is as mentioned before, rotational weight. The secondary issue is rolling resistance caused by more rubber touching the road. Increased tire pressure can help this but then traction is compromised. I've debated using the Konigs with the stock tires. I think this may give more acceleration but also keep MPG. Of course I'll loose the cornering I now have, but I'd like to see more accel out of my vehicle right now instead of cornering performance. It all comes down to what you want out of the car. You are limited with what a Yaris is capable of. IMO, you can't get both. __________________ AEM CAI, NST Pulleys/SSK, WR 4-2-1 Header, TRD axelback, R1 Concept Rotors, TRD Sway Bar, Nitto Rear Strut Bar, Cusco GT-Zero Coilovers, 1ZZ-FE 1.8L TB

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11-26-2008, 07:49 AM	#2
ddongbap Banned Drives: yw calls me douche and racist. Join Date: Aug 2007 Location: hay Posts: 2,183	http://www.miata.net/garage/tirecalc.html Theres an area where you can type stock, and aftermarket tire size. Then it'll tell you the difference in percentages. It'll also tell you what the difference in the speedometer it'll show. Long story short; as long as the outer diameter of the rubber, not the rim, is the same, then you will not have any problems. Though there are rarely EXACT rubber sizes that would be the same on a 15 and 17 inch. They'll come pretty damn close. I was looking at 215s for 16 inches, but the closest I've gotten to was around >1% in size difference. Technically, lowering your car won't have any effects on your fuel economy. Technically. Lowering your car may have adverse effects on your alignment, and through that, you'll get difference in fuel economy. For example, if your toe happens to change slightly, it'll create some drag on the tires. Since the tires would try to pull away at different directions. Though most of this is only technically.

11-26-2008, 10:11 AM	#3
songa View User's Garage Drives: 2009 Yaris Sedan (Black) Join Date: Nov 2008 Location: MA, USA Posts: 139	thanks man, thats some good informatino. i found some 17" combos that would result in a 0.1% difference, but ive decided that even that small amount is too much. id rather have it all exact, because im very concerned about fuel economy and would like to know the exact # of miles ive traveled over time. and if you're 0.1% off, the more miles you drive, the more wrong the number will get. what are the dimensions of the stock tires on the yaris? i got the regular sedan, but it has the package that includes the 15" steel wheels with full wheel covers. is that a P185/60/R15 size? has anybody replaced their stock 15" steel wheels for 15" rims, but using the stock tires? right now thast what im most interested in doing. as for lowering the car, im still unsure of becuase im really afraid of bottoming out in thsee horrible boston roads...

11-26-2008, 02:06 PM	#4
CASTREX Who said Yaris was slow? View User's Garage Drives: Yaris T-Sport 2008 Join Date: Nov 2006 Location: Costa Rica Posts: 1,287	You are really into the MPG and you are getting 17's??? a 0.1% diff is minimal.... If you are really interested on your MPG you should stay with 15" wheels. But if you really want larger tires. Try to get the lightest wheels you can find. The wheels weight on such a small engine make a big difference.

11-26-2008, 02:45 PM	#5
songa View User's Garage Drives: 2009 Yaris Sedan (Black) Join Date: Nov 2008 Location: MA, USA Posts: 139	thanks for the input. well i really dont know much about cars, esp. stuff like how wheels affect fuel economy, etc. so i was just tyring to find out more information about them. 0.1% difference is minimal but over a long distance, the odo will be reading a value much less than what you actually traveleed, right? in any case, i probably will end up getting 15" thanks guys

11-26-2008, 04:25 PM	#7
songa View User's Garage Drives: 2009 Yaris Sedan (Black) Join Date: Nov 2008 Location: MA, USA Posts: 139	yes that makes sense, thanks. and also, you're right...even after 35,000 miles, you will only be 35 miles off....so say you drive 105,000 miles (close to the end of the life of the car), you'll only be 105 miles off on the odometer...still not that big of a deal. thanks for the clarification castrex! this brings up one other question...you said that fuel economy will suffer if i get the 17" rims. how much will it suffer, and why? i currently avg around 37mpg. on 17s, will it go down to like the low 30's?

11-27-2008, 03:32 AM	#12
songa View User's Garage Drives: 2009 Yaris Sedan (Black) Join Date: Nov 2008 Location: MA, USA Posts: 139	thanks guys for all that info. quick question tho..does anybody know how much the stock 15" steel wheels weigh?

11-27-2008, 01:43 PM	#15
bzinn 1 Drives: 2008 Yaris HB Join Date: Oct 2008 Location: University Place,WA Posts: 828	I went from the stock 14" to 17" and my MPG has only dropped 2MPG.....and I can live with that.My rim/tire setup now is only 2lbs heavier than the stock setup.add the hub caps to the stcok rims and I am about the same weight. Bigger tire width though is most likely where I am losing ground as it has more drag than the skinny stock tire. Find a good quality rim that is with the tire going to weigh near the same as the stock rim and tire and you will notice very little differance.