If you've put larger, aftermarket wheels on your G, I have a few questions.

1. Gas mileage - better, worse or not noticeably different?
2. Did you get your speedo adjusted to read right? (is it even possible?)
3. Odometer - obviously not going to read right - can it be adjusted so it reads correctly?

Thanks in advance.

 

If your overall circumference is the same, the speedo and odometer won't be affected. If the larger wheels are lighter, your mileage won't suffer, certainly not significantly.

 

most important thing is to keep the overall diameter the same as stock wheels. most people get carried away with wheel widths and getting it to sit flush with the body and hence ignore to keep the overall diameter the same.
also buying wheels based on looks alone is quite silly, as some of the more popular wheels people use here weigh quite a bit. dont see the point in slowing down your car for the sake of looks.

 

another question, if you upgrade to 19s and lets say God forbid, one of them blow and you gotta use your donut, wouldnt that be bad for the car? i am assuming the donut is 17" (definitely not 19" basically).

 

Damn. Hadn't even thought of that.

I'm going from 18's to 20's, but from 225/50/18 and 245/45/18 to 255/35/20. There will be a difference in overall circumference/diameter, though I'm not sure how much.

 

The problem is that you keep focusing on the size of the wheel. The wheel size does not determine the overall diameter, the tires do. With the stock wheels, you have thicker tires which will sett the overall diameter around 26".

Now you switch to 20" wheels with thinner tires, and the overall diameter is still 26". Therefore your speedo reads the same and the spare wheel can still be used.

 

^ what bout the donut issue?

 

To answer your question:


Tire size 225/50-18 255/35-20
Tire diameter 683 mm (26.9'') 686 mm (27'') 3 mm (0.4%) taller.


The overall diameter is 3mm bigger, which is insignificant. When speedometer reads 60mph (96.6km/h) actual speed will be 60.3mph (97.1km/h): 0.5% faster.

 

Hey MAC u can always use this calculation @ Tire Size Calculator - tire & wheel plus sizing

You are < 1% off, so it's fine.

Stock Tire - 225/50R18 >Search Tires Tire 1 - 255/35R20 >Search Tires
Section Width: 8.85 in 225 mm
Section Width: 10.03 in 255 mm

Rim Diameter: 18 in 457.2 mm
Rim Diameter: 20 in 508 mm

Rim Width Range: 6 - 8 in
Rim Width Range: 8.5 - 10 in

Overall Diameter: 26.85 in 681.99 mm
Overall Diameter: 27.02 in 686.30 mm

Sidewall Height: 4.42 in 112.26 mm
Sidewall Height: 3.51 in 89.154 mm

Radius: 13.42 in 340.86 mm
Radius: 13.51 in 343.15 mm

Circumference: 84.35 in 2142.4 mm
Circumference: 84.88 in 2155.9 mm

Revs per Mile: 774.6
Revs per Mile: 769.8

Actual Speed: 60 mph 100 km/h
Speedometer1: 59.6 mph 99.3 km/h

Speedometer Difference: - Speedometer Difference: 0.623% too slow
Diameter Difference: - Diameter Difference: 0.63%

 

It shouldnt be an issue. The donut that comes with the stock 19" sports wheels is 18". Even at stock, the spare wheel is a mismatch. And since your 20" wheel + tire will have the same overall diameter and stock, you can use your donut with no problem. The spare is for temporary use only and should be removed as soon as possible.

 

The donut isn't the exact same circumference or diameter as the OEM wheel either. It isn't an issue if you are using the donut only for emergencies as it's intended to be used.

 

^ ok, i was thinking for example your on the highway and something happens, i guess go slow for the rest of the way.

I just upgraded from 17'"s to 19"s and forgot to ask my wheel guy about this.

 

Thank you, gentlemen, for all the input. You've put me at ease.

I am so stoked about getting my wheels... gotta wait up to 60 dang days...

My detail equipment will be here Monday and I am just ITCHING to get a good, quality detail on the girl.

After that I'll just need an emblemless grill. Been looking for one, but no luck. I saw that 180custom can make it that way, but it just seems like a hassle to have to mail it and then pay for the work + paint, etc.

I'm sure someone will eventually start mass producing them.

 

[quote=Dj farhan;3118494]^ ok, i was thinking for example your on the highway and something happens, i guess go slow for the rest of the way.

Yep, you're not supposed to go faster than 50mph and farther than 50 miles on the donut anyway, IIRC.

On the question of mpg, for what its worth there was a slight decrease in MPG with mine when i changed to approx 4 lbs. heavier tires.

gshack » Mods vs. MPG

YMMV, of course.

 

^ thanks!