abcut973

So i recently switched my OEM 18" for some really nice CF10 forgestar 19" with Michelin PSS rubber (245/35 F, 275/30 R).

https://mbworld.org/forums/5605713-post4049.html

I do know i didn't lose power and that it's down to pure physics but the car gives me the impression to be slower than usual particularly at starts. When i was just touching the throttle pedal to get a decent acceleration now i feel like i really have to push it harder to get the same result. Hence a difference in my mpg! lol!
For sure the meatty PSS stick it to the ground and i have better traction now but still i'm slightly annoyed by this feeling. I guess i'm not used to it yet. It will fade with time and once i'll get more miles on the tires too

Did you guys experience the same when you put your new shoes on?

synacide

I have the same experience with my setup. I have 20" DPE 3 Piece wheels that i just put back on for the season. It feels like it takes more power in order to start the momentum of the car to move forward. Its kinda like the feeling of wearing weights on your ankles and trying to run....

gthal

I didn't notice it when my 19's went back on (also PSS tires). In theory, weight might have some impact but I would be surprised if it was that noticeable unless you went with very heavy 19's.

CarHopper

It comes down to the weight of the wheel. Lets say the 19's + tires weigh 5lbs more each. Its the difference in sprung vs unsprung weight. So, even though each wheel/tire weighs 5lbs x 4 wheels = 20lb gain total. However, this being unsprung weight is actually close to adding 100lbs of sprung weight to the car.

Sorry if that is hard to following. Think of it this way. Adding 1lb of weight to a wheel is like adding 5lbs to the car.

Pretty sure that's how it works, experts feel free to correct me

gthal

That is what they say but I don't think it should be felt. Put it this way... if I put a 100lb person in the car, I can't feel a drop in acceleration. I realize unsprung weight and rotational weight is different but I think it would need to be a real increase to be felt.

DuaneC63

What he said. It's even worse in the turns.

Ezec63

I agree with the assessment but even tho the forgestars are bigger the way they are made with flow formed lip they are still lighter than the stock cast wheels ! add in the bigger tires and they should be the same if not still a bit lighter

DuaneC63

Only way to tell for sure it to weigh the wheels and tires compared to stock.

CarHopper

I was just using that as an example... The only way to really tell is this...

A bigger diameter wheel as well as width on top of the wider tires would potentially net even more than that 100lbs. It all depends on the wheel choices really and what the actual difference is.

To the OP - weigh a stock 18 and tire (or I will when I put my new wheels on) and weigh what the new wheel and tire weighs. I believe the ratio for sprung to unsprung is something like 1:6. I think this is what you're feeling. If the only thing that you changed were the wheels than that can be the only thing unless it's your mind playing games with you.

adv4nced53

Weight matters. It's like getting a heavier flywheel - it will take more energy to accelerate it. But wheel diameter matters too - it's like gearing the car up. You sacrifice acceleration slightly for top speed. I wouldn't stress it...enjoy your car and its new looks.

Merc63

You have an over active butt dyno.

Must be a pretty sensitive rear end to feel at most 10hp loss.

rory breaker

Both weight and diameter affect acceleration. What you feel is normal. Every car I ever upsized took a hit from an acceleration perspective.

One reason I stuck with the OEM 18s (that, and I like them better frankly).

CarHopper

18->19 doesn't necessarily mean an upsize in the overall circumference. Then it comes down to just the tire size and the wheel itself doesn't matter.

If you're running an 18'' wheel with a tire that has a 2 inch sidewall you'd have the same circumference as a 19'' wheel with a 1 inch sidewall, yes? Then it is literally the same so I guess it comes down to what the tire size is.

So, what is the tire size assuming the weight of the wheel is the same?

abcut973

Are you talking about your 19" OEM. I think they 9x19 in the rear right? Mine are 10x19 + PSS.

Very interesting information. I didn't see it this way. Thanks


Will try to do this. Not too sure what scale to use?


I do enjoy the car but realize i may sacrifice acceleration for the look.



LOL! Probably


Well I was thinking about getting rid of my 18 OEM and buying 19 OEM instead. I'm pretty sure it does not feel different.


The car is on stock suspension. Do you think lowering with spring or coilovers will overcome this feeling?

Ezec63

Take a look at the aftermarket weight sticky ... When rear stock setup was switched to a bigger 18" setup with much bigger and reinforced nt05 the weight of each wheel was still a pound lighter even tho the rims is wider and the tire is wider so the jump to a similar rim in a 19" instead of a 18" shouldn't add more than a pound or 2 max .. Then the front setup where the rims and tires aren't that much bigger then stock have a big weight saving over 8 pounds a wheel ! and again a 19" size would prob bring that number down to 6 pounds a wheel lighter

CarHopper

@ abcut973 -- You said you don't know what scale to use. Do you have a scale to measure how much you weigh? Pick up a stock wheel + tire and hop on. Then pick up your aftermarket wheel + tire and hop on again. Difference = how much weight per wheel you gained.

This is a lot of work of course to just come to the same conclusion. You may be a tiny bit slower off the line and it may take a bit more to get going. However, you have wheels on that you enjoy and you still have a powerful car. There are trade offs to everything that you do.

abcut973

Well I was on OEM 18" with 265 PSS in the rear, 235 in the front.
Now I'm on CF10 19" with PSS 245 F / 275 R. I can definately feel the tire difference. The ride even feels more comfortable than my 18". Like I said the traction is much better.
But i have to stomp harder on the pedal to get the car going vs before. Which does not help my mpg since i see the fuel needle going down quicker

CarHopper

This isn't meant to sound mean (lacking a better word) but I doubt people buy a c63 for gas mileage. I mean, EPA rated 18mpg on a highway is no prius.

Stomp on it, enjoy the traction, and fill up once more per month.

Like I said, trade offs. You now have more comfort and traction and sacrifice a fraction of your mpg's.

Sounds like the benefits outweigh the drawbacks.

abcut973

Mine is a daily driver so I got into some type of routine that I guess I'll have to revise!

CarHopper

Gotchya. Well, I don't think the change will be as significant as you think.

rory breaker

There are many factors here and you have to factor in both the wheel and the tire. People get caught up on wheel weights, then throw tires that are 3lbs per corner heavier on. If you really want to be mindful of the performance you need to factor in wheel diameter, tire dimensions, wheel weight, tire weight...and then of course looks, wheel construction, etc.

Think about it...Upsizing to heavier, larger oem wheels, with wider, larger, heavier tires results in more weight + larger diameter. You can play with tire sizes and brands (impacting total weight and overall diameter) to minimize the effect, but it is going to have an effect. Whether you notice it or not is up to you.

shigo

Actually, more traction means more friction, more power wastage, the 275/30/19 is 814 revs/mi, but 265/35/18 is 822 revs/mi, when you change the circumference, it just likes that you decrease your final drive ratio, so i think that is why you feel lossing the power.
By the way, the original size of the rear tire is 255/35/18 or 255/30/19(option) which is only 832/829 revs/mi.

abcut973

I bought the car with 265/35/18. But i guess you are right 255 is the original size whether 18 or 19.
Interesting information as well. Thanks

By the way I like your wagon... except the front arches

_timothy

sorry to hijack but your widebody estate is SICK

dcho

greater moment of inertia!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!