15 or 16" rim for Toyota Sienta : pros & cons

Car dealer told me 15" saves more fuel & is more suited for Sienta hybrid  (& Airwave)
while 16" is more suited for Toyota C-HR.

I like 16" so that my bumper is not too low & often get scratched when reverse-parking
or head-in near high pavements (have seen pavements of 9-10" higher than parking
ground)

Q1:
Is this true that 15" saves more fuel?

Q2:
which one can accelerate faster or no diff?

Q3:
which one is more stable ?  I tend to think lower centre of gravity makes
an object less likely to overturn
sunhuxAsked:
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David Johnson, CD, MVPOwnerCommented:
A1: There is the rim size and the aspect ratio of the tire.A tire with the same aspect ratio but a larger rim size will require less revolutions to reach the same road speed.
A2: Acceleration is more dependant upon torque (horsepower) Again larger tires require less rpm to achieve a faster speed. It also depends upon the friction coefficient of the tire itself (fatter tires have a larger contact area and depending upon the tread pattern (or lack thereof) have a higher friction coefficient before they slip when accelerating you want to be at the edge of the tire slipping (burning) to achieve maximum traction.

A3: Yes the lower the center of gravity the less likely to overturn.

One also has to consider the sprung weight vs the unsprung weight (the weight above and below the springs)

There also is the design of the wheel wells.. is the car designed to have 16" wheels with tires of the same aspect ratio of the 15" rims?-
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serialbandCommented:
I think he's got more 15" Sentras available and is getting a slightly bigger commission for them, so he's trying to move them off his lot.  Your factory set wheels and tires will have the correct odometer settings.  If the sticker shows the same mpg, then it's essentially the same.

A1.  The larger wheel will be very slightly heavier and might use a tiny amount of extra fuel that way, but it would be negligible overall, maybe a mile or so difference every 100,000 miles.  If the final tire size is also larger and they didn't recalibrate your odometer, then there may be a false perception of using more fuel, but if you calculate your wheel size ratios, you'll know that it's getting close to the exact same mpg.

Long ago I had the same wheels but when from an r14 to an r15 tire, because that was what they had in stock and allowed on my car.  I ended up with a 35/37 mile ratio difference because they didn't recalibrate the odometer.  When I factored that into the mpg calculations it was essentially the same.  My annual ~400 mile trip to visit family became about 380 on the odometer.  The Radar signs also showed that difference in mph.  I calculate my gas usage and kept receipts, so I know I was using the same amount of fuel.   There was no perceptible difference in performance.  The thread patterns might actually matter more.

A2.  There should be no perceptible acceleration difference, as the wheel weight is negligible compared to the total weight of the car.  You might notice a difference if you were to drag race it.

A3.  While technically, a lower center of gravity is more stable, but 1" on a sentra will not make a perceptible difference, unless you're racing your car and cornering at its very limits.
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RaminTechnical AdvisorCommented:
Is this true that 15" saves more fuel?
Only if you are going to use a wider Tire with Rim16 then the answer is yes, because the range of Tire dimensions that you are allow to use  for Rim 15 or 16 have an overlap dimension ( you can use the same tire width that you want to use for Rim 15) .   fuel consumption directly depends on the Coefficient of Friction  between tire and  road and  width of the tire can increase this force.


which one can accelerate faster or no diff?

since the tire's diameter must keep intact so there is no difference. but if you use a high quality rim with less weight then it can cause a little more acieration.

1.jpg

which one is more stable ?  I tend to think lower centre of gravity makes
 an object less likely to overturn
The more you increase the Rim size the more you must decrease the side wall of the Tire to keep the diameter intact and this will bring more stability on the curves (less sidewall and more width) and better handling on road but absorbs more shocks from the road and less comfort for the passengers.




Note: Changing the Rim size is not that easy.  you need to search more and get some knowledge about Rim offset (you have to make sure you are using the same factory original offset with your new Rims or you will damage your car), Tire dimensions, Tire Plus Sizing Calculator / Calculates Tyre Dimensions for Plus Sizing.

Please read below article.
http://www.tyresizecalculator.com/

you must choose the best combination of Rim and tire with the least difference in diameter in compare with the standard rim and tire which your car came out with.  

Changing  the Rim size  without knowledge can affect on ABS mechanism and also shows incorrect Speed (changing Tire's diameter).
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JohnBusiness Consultant (Owner)Commented:
If your car was designed for 16 inch wheels, then it should have bigger brake disks, so the brakes will run cooler and last longer. My Volvo XC70 has bigger wheels and disks than my Volvo S60 has.  Bigger brake disks is the best advantage of the big wheels.
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serialbandCommented:
All those specs are mainly noticeable when you push your car harder and like to speed.  If you're an average driver, you won't really notice most of those variables.  The engine would have the most effect on fuel economy for most users.  That is usually reflected in the standardized test by the government.

If you want the extra clearance, then you need larger tires.  The rim size may include larger tires, but if the wheel well doesn't allow it, then you just have larger rims with the same radius tire meaning you won't be raising the car up by an inch; it will stay the same.

Which model Sienta is it?  https://tiresize.com/tires/Toyota/Sienna/
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sunhuxAuthor Commented:
I m quite newbie in this.  Oddly the site gave Sienna   instead of Sienta.  The closest I got is   https://tiresize.com/tires/Toyota/Sienna/2000/

Its sienta 1.5 G (A)   2017 make according to my dealer.  Does above link mean its meant for 15" rim?
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RaminTechnical AdvisorCommented:
If the original size of Rims for your car is 14" and Tire dimension is   175/70/R14 then:


The Standard match for Plus one and Plus two Rim Upsizing are:

Rim 15" with Tire dimension 185/60/R15 84H  Rim Detail: 5.5Jx15 ET39 with positive offset
OR
Rim 16" with Tire dimension 195/50/R16 84H  Rim Detail:  6Jx16 ET45 with positive offset
1
sunhuxAuthor Commented:
Attached is what I've seen from the site: looks like every possible models of 2017 Sienna indicates 15" rim:
so going by the last post above from Ramin, does it mean there's a leeway of upgrading the rims by 2" ?
ToyotaSienna_Rimsize.JPG
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RaminTechnical AdvisorCommented:
Rim Diameter = 14 inch  = 355.6 mm
Total Tire Diameter with Rim = 175 * (70/100) * 2 + 355.6 =  600.6 mm   // Standard Tire Diameter
// The most Comfort, The least Performance //

Rim Diameter = 15 inch  = 381 mm
Total Tire Diameter with Rim = 185 * (60/100) * 2 + 381 =  603 mm          // Acceptable Tire Diameter  
 // Good Comfort,   Good Performance,  The most accelerate because of more Tire's diameter //

Rim Diameter = 16 inch  = 406.4 mm
Total Tire Diameter with Rim = 195 * (50/100) * 2 + 406.4 =  601.4 mm     // Acceptable Tire Diameter
 // Comfort is nor acceptable,  Very Good Performance//



Rim Diameter = 16 inch  = 406.4 mm
Total Tire Diameter with Rim = 215 * (45/100) * 2 + 406.4 =  599.9 mm     // Acceptable Tire Diameter
 // The least accelerate, The most Performance,  The least comfort, The most Fuel consumption //



Rim Diameter = 15 inch  = 381 mm
Total Tire Diameter with Rim = 205 * (55/100) * 2 + 381 =  606 mm              // More than 5 mm difference with original Tire's dimension

Any combination of Rim with more than 2" difference with original Rim and any Tire  will cause more than 5 mm in Tire Diameter which will cause Contact between Tire and Wheel arch when car is loaded.
1
serialbandCommented:
Oops, sorry, here's the correct link https://www.wheel-size.com/size/toyota/sienta/
1
sunhuxAuthor Commented:
One more query:

So if I stick with 15" rim, I can still go with 16" tyres?


I narrow down to 3 options below & is considering option 3 if it's as comfortable as Option 1 & yet gives best performance?

Option 1:
Rim Diameter = 15 inch  = 381 mm
 Total Tire Diameter with Rim = 185 * (60/100) * 2 + 381 =  603 mm          // Acceptable Tire Diameter  
  // Good Comfort,   Good Performance,  The most accelerate because of more Tire's diameter //

Option 2:
 Rim Diameter = 16 inch  = 406.4 mm
 Total Tire Diameter with Rim = 195 * (50/100) * 2 + 406.4 =  601.4 mm     // Acceptable Tire Diameter
  // Comfort is NOT acceptable,  Very Good Performance//

Option 3:
Rim Diameter = 15 inch  = 381 mm
Total Tire Diameter with Rim = 195 * (50/100) * 2 + 381 =  576 mm
// ??,  ?? //
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RaminTechnical AdvisorCommented:
So if I stick with 15" rim, I can still go with 16" tyres?
No, only 15"" Tire can install on 15" Rim

Tire height in your car must keep around 600.6 mm  (standard height for your car model) and +/- 4 mm .

Your suggestion with  Rim 15" and 195/50/R15 tire  will decrease tire height to 576 mm.  that means 24.6 mm less diameter.
don't even think about it.  your choice must be +/- 4 mm less or greater than 600.6 mm.

If you like 195/50 Tire then below is your best choice:

Rim Diameter = 16 inch  = 406.4 mm
  Total Tire Diameter with Rim = 195 * (50/100) * 2 + 406.4 =  601.4 mm     // Acceptable Tire Diameter
   // 60% comfort ,  Very Good Performance//



                                                                               * * * * *

let me show previous suggestion with comfort in percentage:

 Rim Diameter = 14 inch  = 355.6 mm
 Total Tire Diameter with Rim = 175 * (70/100) * 2 + 355.6 =  600.6 mm   // Standard Tire Diameter
 // 100% Comfort , The least Performance //

 Rim Diameter = 15 inch  = 381 mm
 Total Tire Diameter with Rim = 185 * (60/100) * 2 + 381 =  603 mm          // Acceptable Tire Diameter  
  // 80% Comfort ,   Good Performance,  The most accelerate because of more Tire's diameter //

 Rim Diameter = 16 inch  = 406.4 mm
 Total Tire Diameter with Rim = 195 * (50/100) * 2 + 406.4 =  601.4 mm     // Acceptable Tire Diameter
  // 60% Comfort,  Very Good Performance//



 Rim Diameter = 16 inch  = 406.4 mm
 Total Tire Diameter with Rim = 215 * (45/100) * 2 + 406.4 =  599.9 mm     // Acceptable Tire Diameter
  // 40% Comfort, The most Performance (Excellent),  The least comfort,  The least accelerate,  The most Fuel consumption //
1
RaminTechnical AdvisorCommented:
You also have this option: 195/55/R15 Tire with 15" Rim .  

Rim Diameter = 15 inch  = 381 mm
Total Tire Diameter with Rim = 195 * (55/100) * 2 + 381 = 595.5 mm          
   // 70% Comfort ,   Very Good Performance,  The least accelerate because of less Tire's diameter //

Note: you will see your Speedometer shows about 4 Km/h more than your real speed ( 5 mm difference less than standard Tire diameter)

Note: you have to make sure you can get the Tire with your desire dimension before buying the Rims (some Tire dimensions are very rare to find).

Another factors which are important in fuel consumption & Performance on curves field are Tire Brand / Technology /  Quality and Tread design.
http://www.michelin.com.my/MY/en/tires/products/energy-xm2.html
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bsodCommented:
Stick with the same wheel diameter and tire size the manufacturer recommends. Your vehicle's suspension system was set up for that wheel/tire configuration and anything different will impact handling and stability, as well as the speedometer/odometer issues everyone else has already mentioned. Amateur second-guessing of OEM engineering can lead to all kinds of headaches.

If you're concerned about fuel economy, a better strategy is to look for recommended-size tires with better (i.e. lower) rolling resistance, rather than different sized tires. Consumer Reports, for example, shows rolling resistance ratings in their tire scores.

If you're concerned about scratching your bumpers when you park, consider buying an SUV, rather than re-engineering a minivan.
2
BillDLCommented:
Another thing to consider is whether your insurance requires that you notify them of "modifications" from standard.  This is certainly the case here in the UK and I would imagine that there are similar clauses with car insurance in other developed countries, but it would depend on what they specify as "modifications".  I know of a guy who fitted a fancy flush fuel filler cap, machined his own aluminium gearknob, and stuck a couple of "go faster" decals on his car, and his insurance payout for a no-fault collision (other car caused it) was reduced drastically because he hadn't previously informed them of the "modifications" and allowed them to bump up his premium.
1
bsodCommented:
Good point re: insurance. In fact, thinking back to all those Wheeler Dealers episodes I watched (when Edd China was still on the show) I wouldn't be surprised if installing 16" rims on a car designed for 15" rims might cause the car to fail its MOT inspection in the UK. Something to consider if the OP is from a country that mandates vehicle/equipment inspections.
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dbruntonQuid, Me Anxius Sum?  Illegitimi non carborundum.Commented:
If you go to a non-standard wheel rim and tyre configuration such as you are suggesting you will find that when you come to replace the tyres they will be expensive.  Because they are not a normal off-the-shelf tyre they will cost more.
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BillDLCommented:
Land Transport Authority Of Singapore:
https://www.onemotoring.com.sg

Guides to what vehicle modifications are allowed, require approval of the LTA, and are disallowed:
https://www.onemotoring.com.sg/content/onemotoring/en/lta_information_guidelines/modifications_and_vehoffences/modification_guide.html

Important note on that page:

"The General Insurance Association of Singapore would like to advise motorists to notify and declare to their respective motor insurers any modifications (including those approved by the Land Transport Authority) made to their vehicles. Failure to do so may result in the declining of claims in the event of an accident and the motor insurance policy considered void on the grounds of non-disclosure."

Modifications that are allowed:
https://www.onemotoring.com.sg/content/onemotoring/en/lta_information_guidelines/modifications_and_vehoffences/modification_guide/modification_allowed

 
Sports rims
(for cars only)

The following requirements must be met for cars when changing to sports rims:

a) The size of the sports rims should be in accordance with the car manufacturer's recommendations.
b) They shall not protrude from the car body laterally.
c) The overall rolling radius of the original wheels and tyres should not be altered.

 
Tyres
 
The following requirements must be met when replacing tyres:
a) Every wheel of a vehicle shall be fitted with a pneumatic tyre that must be of the correct width, profile and diameter as recommended by the vehicle manufacturer.
b) The tyres must not protrude from the vehicle body laterally.
c) The overall rolling radius of the original wheels and tyres should not be altered.

Note: Off-road tyres are not allowed for use on normal roads (e.g. slick tyres, semi-slick tyres, cross-country tyres for rugged terrain, etc).

In Singapore after a private motor car reaches 3 years old it must have a safety inspection and emissions test every two years until it is 10 years old, at which point it must be inspected each year.  Taxis must be inspected every 6 months from new.  One of the key checks done is that of the "wheel system", i.e. "The condition and operation of the tyres, suspension unit, shock absorber, wheel bearing, the alignment of the wheels are checked to ensure that vehicle stability is not compromised."
https://www.onemotoring.com.sg/content/onemotoring/en/lta_information_guidelines/maintain_vehicle/inspection/systems_of_a_vehicle.html

It is all more similar to the UK laws than to any on the American continent, which is hardly surprising since it was a British colony up until fairly recent times.
2
bsodCommented:
Well there you have it. I hope the OP hasn't gone and bought 16" rims already.

It's too bad Edd China isn't on Wheeler Dealers anymore. I learned a lot from him over the years.
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sunhuxAuthor Commented:
So from the LTA link  / extract,

a) The size of the sports rims should be in accordance with the car manufacturer's recommendations.
Both 15 & 16" rims are within Sienta manufacturer's recommendations, aren't they ie as per link below?
https://www.wheel-size.com/size/toyota/sienta/2017/
Extracted from above link the 2 lines below:
  5.5Jx15 ET39  <== 15" rim
  6Jx16 ET45     <== 16" rim

c) The overall rolling radius of the original wheels and tyres should not be altered.
The radius will get changed if I increase to 16"
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bsodCommented:
Hi sunhux,

I would not recommend using wheel-size.com to make your decisions. That's an independent US website and Singapore LTA will not care what it says. LTA will go by Toyota's manufacturer specifications only. So I downloaded the Sienta brochure from here:

https://www.toyota.com.sg/showroom/new-models/sienta

It says 15" rims for Sienta Standard and 16" rims for Sienta Elegance:

Sienta Standard: 185/60R15 = 492mm outside diameter of tire

Sienta Elegance: 195/50R16 = 504mm outside diameter of tire

The suspension systems of the Standard and Elegance versions may be adjusted differently by Toyota for these different wheel/tire combinations. The computer modules that control the speedometer and odometer will definitely be programmed differently. Therefore LTA might not allow you to put the Elegance wheels/tires on a Standard Sienta.  (i.e. LTA might consider Standard and Elegance to be different vehicles with different specifications.)

I would recommend you contact Singapore LTA before deciding to spend any money on 16" rims.

Good luck, and happy motoring!
1
dbruntonQuid, Me Anxius Sum?  Illegitimi non carborundum.Commented:
>>  c) The overall rolling radius of the original wheels and tyres should not be altered.
The radius will get changed if I increase to 16"


Not necessarily.  The tyres recommended will usually be not so high as the 15".

Thus a 15" wheel rim plus high tyre is the same as a 16" wheel rim plus low tyre.  Your link above does show the tyres recommended for the Sienna.

Smallest tire size:  185/60R15
Largest tire size:    195/55R16

There is a magic formula which gives you the height of wheel and tyre from that information.

(2 x Nominal height x Aspect Ratio) + (Wheel Rim Radius x 2.54) = Height of wheel and tyre  (See  https://en.wikipedia.org/wiki/Tire_code#National_technical_standards_regulations  for more information only if you're bored).

So for the 15"
(2 × 185 × 60/100) + (15 × 25.4) = 222 + 381 = 603 mm
And the 16"
(2 × 195 × 55/100) + (16 × 25.4) = 214.5 + 406.4 = 620.9 mm

Thus you see the 16" height is approximately 16mm higher than the 15".  What the 16" wheel also offers is wider rubber on the road for better grip.  This is usually at the cost of a slightly worse ride on rough roads.

You wouldn't notice that 16mm height in the car park.
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bsodCommented:
Thanks for fixing my math, dbrunton. I forgot to double the width of the tire in my calculation.

Note, however, the manufacturer-recommended tire for 16" rims is 195/50R16 instead of 195/55R16. That would result in a 601.4mm outside diameter for the tire. It's almost identical to the 603mm 185/60R15 tire for the 15" rim and might receive LTA approval. (Your odometer would be off by 266 KM when it shows you've traveled 100,000 KM.) I would still check with LTA before buying the 16" rims, since they're not manufacturer-recommended for the Sienta Standard.
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RaminTechnical AdvisorCommented:
Thanks,
I'm glad we could help.
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BillDLCommented:
Thank you sunhux
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