Calculation Formula with Towing Capacity when adding bigger RIMS

[SunlitComet]

best way I know is use tirerack.com site to find info based on your vehicle Pick your tire selection and look at the specs which will give you all kinds of load and dimensions and you can also choose custom tire sizes and get specs on those too. I put your vehicle with 24 "rims and chose a yokhama advan st and it chose a 305/35R24 tire with these specs:




Load Max. 2469 lbs.
305/35R24
Load Index 112 = 2484lbs (1129kg) per tire
Speed Rating “W” = 168mph (270kph) 112W RF Treadwear: 320
Traction: A
Temperature: A320 A A

32.4 overall diameter
12.3 sectional width
tire weight 47lbs.

 

[longstand]

Thanks man

i did check the website. and the original Stock rims diameter is 30".
By me having 24" rims it just added 2" more

from 30" to 32", i don't think i should loss much of any towing capacity.

my gear ration is 3.73 and maximum towing is 6500 pounds. so i assume it will go down to 6000 maximum towing capacity

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I got this weird idea, maybe it will work..

Let's say, i wanted to tow my boat to the beach and i have a 1 pair of 15" rims with total diameter of 26".
I keep the front tire with the 24" rims and just replace the rear temporally while i move the boat. will this create any kind of hazard?

 

[SunlitComet]

something is wrong with that number I don't think they manufacture rims up to 30 inches. Not even for big rigs so I will assume you are talking about total diameter.

1. There will be a mismatch is ABS speed sensors front to back
2. It will look weird
3. The speedo will be off

How about posting the tire size you have on these 24" rims and I will try a calculation for you based on your gear ratio.

I really think you will just have a very slight lack of power and a slower speedo with your 24's. It is the weight capabilty of the rims and tires I'm most worried about along with the trailer tongue weight that is going to make or break you plan.

Can you get the full make, model and sizes of rims and tires to post here?

 

[branndon_b]

he probably meant that stock tire diameter was 30 inches. that sounds about right

 

[BigDaddy13440]

Stock tire - 265/70/16

265 - tire width in millimeters
70 - % of sidewall height to width
16 - rim diameter

Formula for figuring diameter -

Width X %, divided by 25.4 (mm per inch conversion) = height of one sidewall
Take that height, multiply x 2 (2 sidewalls, one on top of rim, one on bottom)
Add the rim height, Total is overall tire height.

265 x .70 = 185.5
185.5 / 25.4 = 7.303
7.303 x 2 = 14.606
14.606 + 16 = 30.6" tire height

Of course, this is a tire/rim combination that is fully inflated, and not under load. As you know, tires under load squat, and so the static loaded radius (distance from ground contact to the very center of the axleshaft) isn't exactly 1/2 of the overall diameter, usually about 47-48%. So, in this case, the SLR is roughly 14.6".


Comparing the two tires this way,

305/35/24

305 x.35 = 106.75
106.75 / 25.4 = 4.203 x 2 = 8.406 + 24 = 32.4" overall

To see how far off your speedo is, divide the new tire diameter by the old:
32.4 / 30.6 = 1.058

Multiply this by 60 (what your speedo would say is 60 mph).
1.058 x 60 = 63.54 - this is how fast you are actually going when your speedo says 60mph.

I would most likely assume payload and towing capacity aren't affected by much, as long as your rim and tire combination are rated at the same capacity as your stock set.

---------- Post added at 10:01 AM ---------- Previous post was at 09:59 AM ----------

Of course, the larger diameter DOES affect your braking - if you plan on towing anything anywhere near the maximum load, I'd highly suggest doing a break upgrade.