JackSparrow

I'd like to try to gain some mpg and speed in the 1/4 mile
by switching the stock tires on an LT to something slightly smaller than stock
for less wheel and tire weight as well as rolling resistance,
but pick a tire with a compound and tread pattern that's still quite grippy.

I had in mind 185/65R-15 tires.
They're about 24.5 inches tall, so fairly close to stock.
Their load rating is identical to the 195/60R-15's
which come stock on even 2009 Cobalt LS's with auto trannies.

I was also toying with the idea of going down to 14 inch rims,
however this doesn't seem like a good idea
because it might be hard to find a decent performing tread pattern and compound
as well as if I ever try to sell it, people might wonder "what I've been smoking."

Another problem is that for 2009
the LT's come with 5 lug hubs instead of 4 lug hubs
so it might be hard finding a good 15" wheel (hopefully inexpensive and fairly lightweight)
for this bolt pattern, so it seems a hub conversion might be in order.

Is it hard to do a hub conversion?
How long does it take to do it? (if I had the GM mechanics do it for me)
I'm trying to get an idea how much this conversion might cost.

*The GM dealer said to me that I do not need to keep the stock wheels and/or tires,
I could simply sell them back to the GM Parts Department,
preferably before I drive the car off the lot,
to maximize the amount they'd give me back trading in the OE parts.

roadrage06

you do know the objective is to get a lower ET in the quarter.........not a higher mph.

JackSparrow

Actually yes I do...
but I figured that if the stock motor isn't making enough power to break the tires loose most of the time,
a smaller footprint would allow it to accelerate better due to lower resistance.

Even if the motor can occaisionally break the tires loose,
if going slightly smaller but using a great tread didn't make much difference,
perhaps I could get it to accelerate faster
even if I had to re-learn how not to break loose the tires.
I also figured it'd be really nice while driving at 50+ mph.
Then at speed there's the effect of wind resistance on tire too. (subtle, but it's still there)

What got me into thinking about this:

I saw a Motor Trend tire test using an F-150 with 2wd, auto and 5.4 L V8 back in 1997
where when they swapped the stock tires from 245/75R-16's to an all-season or summer sport tire 285/60R-16's that the tire hurt both their 0-60 time and their 1/4 mile time... Going from 8.3 seconds to 8.5 seconds 0-60 and 16.4 to 16.7 by swapping on wider tires, even though the wider tires were 2 inches shorter, which should have helped add more rear-wheel torque and horsepower.

I forgot to mention in that tire test,
they also tested stock sized tires on BFG All-Terrain rubber.

The all-terrain's lost more in the 0-60,
going from 8.3 seconds, down to 8.6 seconds
but amazingly enough, it was able to gain a bit back in the 1/4 mile,
doing that in 16.6 instead of 16.7 like the 2" shorter, 1.5" wider "sport truck" tires.

The sport truck tires only scored better on the 600 ft slalom and lateral g's.
Motor Trend admitted they were a nice tire, but probably better suited to a modified engine
with more powerfull launch.

So it seems that a wide performance tire doesn't always provide a better E.T.
Probably from what I was assuming earlier;
when you're not breaking the tires loose,
less rolling resistance equals better acceleration.

Maven

iTrader: (1)

You dont want smaller tires for better fuel mileage. the XFEs actually have slightly LARGER tires195/65 vs 195/60.

Its incredibly unlikely youll find a 14" wheel in 5x110. Its even less likely youll find a 14" wheel that fits the 11" brakes that 5 lug cars have.

A hub conversion at the dealer is going to be obscenely expensive, expect to spend about 6hours labor(1.5 per hub) and an absolute minimum of $1300 in parts(4 hubs, 2 drums, 2 rotors, 2 caliper brackets)

Youd probably be better of finding an LS that wants 5 lug setup( If you want to drive to Southern NJ youre invited over to the shop and Ill do the swap striaght up.)

JackSparrow

I hear that the XFE tires are made with a harder tire compound.
That's probably where the lower rolling resistance comes in.
The XFE tires are not narrower than stock however.
Maybe they thought people expect a certain width of tire?

I wasn't really that serious of finding a 14 inch wheel to fit,
a 15 incher with moderate sidewall would do me just fine.
(I liked the ride in the rental with the 195/60R-15's)

Oookay. So it sounds like I might not want a 2009 LT after all.
You have to change the all the brake components to do a hub conversion?
Why does Cobalt even have two different styles of hubs?
Just to be annoying?

Are there any advantages to the 5 lug hub for an LT?
I can imagine the extra strength might be need in the SS, but certainly not the LT.

Thanks for the offer!
BTW Is the New Jersey Six-Flags with "Kingaka" near by?

Maven

iTrader: (1)

Correct XFE have "low rolling resistance" tires, they are also a taller tire than 15's used on other LS/LT cars


Well, you just might not want the top of the line LT, decide what options you really need and see if you can get them on the 1LT and maybe you wont have to get the 2LT and its 5lug wheels. You dont "have " to change the brake components, but its easier. If you didnt want to buy/swap brake parts with a 4 lug car, youd need redrill the rotors and drums with the 4lug pattern and get centering rings made for them. Its gonna be hard to convince anyone to swap with you if youre keeping the rotors/drums/front caliper brackets. I didnt mention this, but it should be fairly obvious that if you want to swap with someone, youll need to find an LS/1LT with ABS. Um, I dont know exactly why they used two different hubs.....its got somehing to do with worldwide compatability and availablility of parts etc(they use the 4 lug hubs and smaller rotors overseas, but they use the 5lug stuff there too....)....but it still makes no sense as to why all the cars didnt get the same pattern.

Ummmmmmm, its easy to put on the SS brakes?

I live about an hour or so from SixFlags Great Adventure

JackSparrow

What I meant was smaller tires should take less power to roll,
but the reason I suspect the XFE is different is it's only slightly taller, but harder too.

I'm in Canada. Check out this link.
http://www.gm.ca/gm/english/vehicles...obalt/overview
It seems that in Canada, you cannot get an LT with 15" rims, or 4 lug hubs.
Every LT I've seen seems to come standard with 16" wheels on 5 lugs, LT1 and LT2.
I'd like side-curtain airbags and A/C, and an LS costs nearly as much as an LT when equipped like that.

If I buy an LS with a stick, it comes as an XFE.
I don't want the hard tires, or the 3.63 final drive instead of 3.84.
The only features I really want from the LT are keyless entry and power windows.

Would it be easier and cheaper to buy an XFE,
sell GM back the tires before I after I've bought it but haven't driven it,
buy my own tires and have them mounted at GM on the stock 15x6 before I drive
or even buy my own rims and mount them myself
and then some day later,
buy myself a custom final drive gear, either the 3.84 or something a little deeper?

I also forgot that I'd prefer an Ebony interior and you can only get that on an LT in Canada.

Would it be possible to find aftermarket 15 inch rims for the 5x110 bolt pattern?
Preferably in 15x6 or 15x5.5

Maven

iTrader: (1)

How does the Pontiac G5 come equipped up north? In the USA a base G5 will have 4lug wheels, will be XFE if stick shift, and comes with the black interior, RKE, power windows, etc.... It sounds like thats what you want.

Youre going to need to decide whats most important to you, the 37mpg highway rating of the XFe cars or the added features of the LT if you decide to stay chevy(or if the pontiac is specd the same way up there) You cant get power windows or RKE in an LS from the factory, buy you can add them either aftermarket, or install GM stuff after the sale. It doesnt make any sense to buy an XFE car and then switch out the final drive.....itll cost well over $1000USD to do that.... why buy a car designed for fuel efficiency and just return it back to "normal" spec?

I understand your concern over the 5x110 bolt pattern, theres very limited selection of wheels under 20lbs in that size, but buying a car you dont like just because it gets 2mpg more than the one you do like is silly. We are talking about a $15-20k purchase, buy the LT(or G5) is my advice.

EXsoccer1921

iTrader: (14)

http://www.mickeythompsontires.com/s...8.0-15&type=SS

theres your tire. now go find a 15"

JackSparrow

Okay, this is retarded...
Both the LT and equivalent G5 show 4 lug 16" alloy wheels on the Canadian GM website
but and all I see at the dealerships are 5 lug 16" alloys.

I'm not interested in buying extra economy,
but it seems that the XFE is the only Canadian '09 stickshift model with 4 lug wheels.
I only expect average Cobalt economy,
plus perhaps quicker acceleration from a better wheel and tire combo.
*If I go ahead with the gear swap, I might want to go a little deeper than stock.

What's the weight of the GM 16x6 inch 5 lug alloy wheels?
If it's 20+lbs and the LS steel 15x6 inch wheel is 16 lbs
it doesn't seem like much of an "upgrade" does it? :p

And I know the tires will be heavier (even if only slightly) on the LT, since it's wider.

NICE!

*I'd be afraid to use those off the track though.
We get a lot of wet and damp days here.