Do 18" rims really slow you down?

Tommy 00GT · Nov 30, 2005

yep, I felt the car was noticably slower after putting on the 18" deep dish bullitts

OinkAodeOink · Nov 30, 2005

just throw another bolt on or power adder to it, if your worried about slowing down. That'll more then make up for the added tire weight.

2002GreyGT · Nov 30, 2005

So the weight thing I understand, but the thinner sidewalls slowing you down I just don't understand.

Thinner sidewalls I can see increasing the roughness of the ride and maybe a little traction off the line. But when you compare a 17x8 with a 245/45 traction patch and a 18x9 245/40 traction patch, wouldn't the extra rubber on the ground make up for the little bit of thinner side wall.

Also, what about keeping the same thickness sidewall and recalibrate the speedo? Or would that add too much extra weight with a thicker sidewall when compared to the larger rotating overall size?

~K

mity2 · Nov 30, 2005

2002GreyGT said:
Also, what about keeping the same thickness sidewall and recalibrate the speedo? Or would that add too much extra weight with a thicker sidewall when compared to the larger rotating overall size?

~K

Thinner and harder sidewall on tire will give you better road holding. But when you want to get up and go from dead stop, it'll spin really easily. You want soft sodewall allows it for lack of better terminology, "bite", and gummy compound for traction off the line. But they do not handle as well on corner

blackfang · Nov 30, 2005

The taller the tire the better sidewall flex you will get in launching. the shorter the tires the less flex you will get and will affect the launch.

My DR's on the Pro Stars are a 275/50R15

jstreet0204 · Nov 30, 2005

tomustang said:
If the overall diameter of the 18's with a smaller tire wall is equal to the stock 17's it wont be a longer rotating mass

having an extra inch is adding weight over a 17

BUT!! More weight is shifted further away from the center, which takes more to overcome and get rolling. I remember a while back on one of the speed channel shows they were modding some import car. They put a larger wheel/tire package on it, that weighed significantly less overall, but becuase the weight was closer to the outside of the wheel it showed a loss on the dyno.

tomustang · Nov 30, 2005

jstreet0204 said:
BUT!! More weight is shifted further away from the center, which takes more to overcome and get rolling. I remember a while back on one of the speed channel shows they were modding some import car. They put a larger wheel/tire package on it, that weighed significantly less overall, but becuase the weight was closer to the outside of the wheel it showed a loss on the dyno.

yes, damn the unsprung weight theroy crapola

Mustang5L5 · Nov 30, 2005

jstreet0204 said:
BUT!! More weight is shifted further away from the center, which takes more to overcome and get rolling. I remember a while back on one of the speed channel shows they were modding some import car. They put a larger wheel/tire package on it, that weighed significantly less overall, but becuase the weight was closer to the outside of the wheel it showed a loss on the dyno.

Bingo. Adding weight isn't the problem, pushing it further away from the wheel is. The further away from the center of the wheel you go, the more energy it takes to spin it.

AN 18" wheel pushes the rim of the wheel further away. Even if the wheel weighs the same, it will still rob more power.

Same deal with Brakes. Larger brakes will slow you down a little bit.

jasonh_86 · Nov 30, 2005

tomustang said:
yes, damn the unsprung weight theroy crapola

Can somebody please explain that to me? losing hp on the dyno and all that..

jstreet0204 · Nov 30, 2005

jasonh_86 said:
Can somebody please explain that to me? losing hp on the dyno and all that..

Think of it like this. Take a 4ft long stick and hold one end of it. Now hang a wieght on it a couple of inches from the end you are holding and raise the other end of the stick. Now do the same thing with the weight hanging on the end of the stick farthest away from your hand, and raise it the same way. It will be harder to raise, but the weight of the stick and and the hanging weight comined has not changed. This is an overly simplified example, but the principles are the same. The greater mass being further away from the fulcrum (center) takes more torque to accelerate the wheel which takes away from the final amount of torque being applied to the ground or rollers on a dyno.

03MGT · Dec 11, 2005

I was worried about the extra wieght as well, But you know what?? Think about when your driving it around, how peoples mouths will drop when they see those deepdish 18`s. I didnt want to go 18`s because I race the stang but what about the 99% of the time when im not racing just driving around and all the looks ill get form them.

Mustang5L5 · Dec 11, 2005

03MGT said:
I was worried about the extra wieght as well, But you know what?? Think about when your driving it around, how peoples mouths will drop when they see those deepdish 18`s. I didnt want to go 18`s because I race the stang but what about the 99% of the time when im not racing just driving around and all the looks ill get form them.

Unfortunately the average person doesn't know the difference between a stock bullitt wheel and a deep dish version.

Sure it's a huge difference to Mustang enthusiasts, but the average non-car person won't know the difference.

03MGT · Dec 11, 2005

Shure people would notice, especially the younings and the people who are into cars would notice. Think about it this way, like anything you do to the car, the average person wont notice or even care.

ponysarepretty · Dec 11, 2005

Especially replicas, they weigh a lot more than stock rims, the stockers are about 22 lbs + 20 lbs of rubber, sp 44 lbs. 18 in FR500s weigh 32 lbs, they are 10 in rims, so they fit about 295s? I would say aout 5 lbs of rubber, so that is 15 lbs of weight!!! per corner!!! Most 18s are about 30 lbs. So which is it? Are you getting more traction or is it your car can't overwhelm the extra weight it need to sling around? 13 in brakes add probably another 5 lbs.

Why do you think SSRs, Steeda superlights and other light rims are so expensive?

StevenGT-02 · Dec 20, 2005

I have muling over my wheel options for over a year...17's or 18"s and i cant deciede... 18's look better but 17's perform better.. i dont go to the track at all, i just like to take coner's fast...I have to pull the trigger soon, i will need new rubber in the spring.

tomustang · Dec 20, 2005

StevenGT-02 said:
I have muling over my wheel options for over a year...17's or 18"s and i cant deciede... 18's look better but 17's perform better.. i dont go to the track at all, i just like to take coner's fast...I have to pull the trigger soon, i will need new rubber in the spring.

if you want to perform better you have to get a tire to match the rim, don't get an oversize tire that'll bulge out from the rim, make it flush

CdnNavybob · Dec 20, 2005

Don't forget that the extra unsprung weight will also affect handling and braking. Wheels are the worst place possible to add weight to the car. Not only do you add rotating mass, you add unsprung mass. Now you've lost acceleration, braking and handling! Lovely!

StevenGT-02 · Dec 20, 2005

Best would be to get a liight weight wheel, like a steeda.. do 17x9 all the way around.

Bullitt0616 · Dec 20, 2005

StevenGT-02 said:
I have muling over my wheel options for over a year...17's or 18"s and i cant deciede... 18's look better but 17's perform better.. i dont go to the track at all, i just like to take coner's fast...I have to pull the trigger soon, i will need new rubber in the spring.

17'' rims perform better? as in drag handling or corner handling? assuming cornering, go 18's. bigger rims mean u'll most likely be putting on a thinner sidewall tire, and thinner sides mean less body roll for better cornering. that's why every road course race circuit uses 18+ rims with thin sidewalls.

there can never be a jack-of-all-trades choice, only a master of one. either a small rim/big tire combo for drag or big rim/thin tire for the twisties.

unfortunately, we are at a disadvantage due to our high amounts of torque in relation to similar HP cars. my old RX-7 had more HP, but less TQ than my Bullitt stock, plus by the time a turbo spools, traction isnt a problem as much. we have ALOT of TQ right after idle and we need tires that can help us grip during launch. that same tire also means less cornering ability.

sigh...

sorry for the long post, but im trying to find the best rim/tire combo as well. no sense making more power if i can still waste it in smoke.

FalconGuy016 · Dec 20, 2005

^^ I have always had all this in consideration when I think about wheels. Good thing I really like how the steedas look cause there is very little to choose from that will actually improve performance.

Do 18" rims really slow you down?

Tommy 00GT

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