NOLACLS

I am going to be putting 235/45/17 on the stock rim and i was wondering if the bigger footprint will slow the acceleration of the car any???

Thanks

Nicky Pass

Contact patch doesn't slow you down.........It is the weight that slows a FWD car down!!!!!!!!

typeR

slow ...if you mean will your gas milage suffer some due to increased rooling resistance...slow as in 1/4 mile...no i think you'll gain much in the ability to launch much harder...

NOLACLS

Type S

yah wider tire will definitely slow a bit ..but i am not sure how slow and u will feel u need to press the gas pedal harder a bit

EricL

If you just changed from a kept the current tire and made it wider, you would use more power to move down the road. However, a 235/45-17 has a smaller front-to-rear contact patch than a 215/50-17 and gets its increased grip from having a wider side-to-side contact patch. The smaller front-to-rear contact patch is kind of like adding additional pressure to the stock tires – there is less power loss due to DEFORMATION. (A tire is not a perfect circle – there is a flat spot that sits on the road. As a tire goes to lower and lower profiles, the weight that used to be supported by the front-to-rear area is supported by the increased side-to-side area.)

This question and answer probably belong in a FAQ, but the reason most of the "aftermarket" tires will hurt gas mileage is due to their increased stick.

If you could find the stock MXM4 OEM tires (stock size in a 215/50-17) and replaced them with the identical tires in a 235/45-17, they would actually need less power to roll them down the street at "most" speeds (up to 60-80mph). A lower profile tire, does not need to deform as much as a narrower tire, and as such, needs less power to roll it down the road. HOWEVER, when speeds start reaching 100-MPH (and higher), the wider tires can HURT the CD (Coefficient of Drag) of the car and increase gas consumption.


The biggest reasons people here (and on other forums) get reduced gas mileage from replacment/3-season rubber is due to the increased stickiness of the rubber. (Try rolling a round pencil down a board and then try rolling that pencil with double-sided tape on it...)


(If you see some of the vehicles that are used for high gas mileage contests, they are generally very high-pressure tires that have a very small front-to-rear contact patch due to the very high pressure.

AztecRol

iTrader: (2)

After I put the 235-45 Toyo T1-S's on my stock rims, I actually got FASTER!!!! Faster into turns, Faster out of turns, Faster on on-ramps, Faster on off-ramps, and FASTER through the TWISTIES!!!!
I hope this answers your question!!!!

JasonT

My road trip(over 3K miles) at speeds of 65-120mph. I got over 30MPG. So I don't think it's hurting my gas milage. I'd say from my experience with truck tires, that yes it does make the car slower, BUT, it's so little that the extra stickyness of the tires will offset any difference.

NOLACLS

Just the answer I was looking for heh heh :P

lou_RENAMED

Yea you do go faster around the twisties but I feel greater torque steer. Not too extreme but when accelerating hard the steering wheel becomes a little more difficult to hold. I personally love it b/c it gives it more of a sporty feel.

mlrspwr

Sticky tires is less wheel spin. From that aspect, you might get "faster" in the sense you cover distance per unit time where you used to just spin tires.
To me "fast in the turns" means "controlled turning at speed". Who cares if I can enter a turn at speed if my tires lose grip and I have no control? And yes, power is nothing without control.
Also, heavier tires affect the rotational inertia of the wheel. I'd be much less concerned with the width of the tire affecting speed than the material of the tire and the weight of the tire.
Yes, wider (and presumably, bigger) tires usually weight more, and that affects rotational inertia of the wheel and therefore wheel speed and acceleration.
BUT TO MAKE IT SIMPLE: I'd rather have my 225 wide S-03s on my car then crap OEM Mich's with the 215 width any day of the week.

NOLACLS

Well the shipping weight of the falkens I am getting is 25.9 lbs...does anyonw know the weight of the stock tires?? And do yall think by shipping weight they meand with the box as well or just the tire??

Bluto

Anyone have problems getting an alignment with 235s?

I'm about to get 235/45-17 Pilot Sport A/S. ($60 coupon at Costco, in the mail).

AztecRol

iTrader: (2)

No no problem at all!!!

mlrspwr

I think stock rims weight 26.5 lbs per. But double check my numbers on the Acura CL FAQ site set up by ChodtheWacko. It is most excellent.

EricL

24-26 lbs depending who weighed them and hom much tread they had on them. Using 25lbs would be a good round number for the stock tire with a few hundred miles on it (that's how much mine weighed with about 300 miles on them). The Chod FAQ says 26 lbs.

You have to call "them" to find out what the shipping weight means for THEM, as I've had vendors spec the weight with and without packing material.

IMO, there wasn't too much that "goes along" with shipped tires... (Ours have NOT come in boxes -- OK?)

When I was calc'ing the weight loss for my Toyos @ 23.8 lbs, I figured a 1.2lb loss per tire (These are much wider than the stock tires, and they are 1.2- to 2.2lbs lighter than stock!)


I highly endorse the option (the CLS really needs wider and stickier tires), and YOU WILL LOSE gas mileage -- it looks like you’re into sticky (good handling, etc.) --yes/no? So, if sticky is what you want, the car will stick to the road MUCH better, but don't be surprised to see a drop in fuel economy.

EricL

I have the same tires and I lost gas mileage. I also get 30MPG on some freeway trips in the 80+ MPH speed range. I’ve talked to a number of other members with “sticky” tires (Toyos, S-03, etc, etc), and they have lost gas mileage in all cases…

Some things to consider...

1. The loss of MPG is NOT from the width of the tire and the tires are lighter and help acceleration (the Toyos are 1.2 - 2.2 lbs lighter than stock per tire). (So, reduced rotational inertia HELPS with acceleration)

2. Depending on wind direction, a trip into a headwind at 60MPH could give someone the same mileage as someone with a tailwind going 100MPH. (The comparison is only valid with before and after averages over a period of time.)

3. Increased adhesion (stick) of the tires will hurt acceleration as speed increases.


AND

4. Lower profile tires don’t use as much energy IF AND ONLY IF they are made of the same compound and construction.

4. The better stick will help to hook-up and NOT squeal like piggies off-the-line!


As much as I really enjoy the "stick" of the Toyos, I can assure you that there is loss in gas mileage compared to those stock tires. Those stock tires are some of the most energy efficient tires around -- they just suck in the handling department when compared to a Ultra-high performance or Max performance tire...

EricL

*** Change in offset effects torque steer (your SSRs are +48 vs. +55 stock).. (tractive force is important, but this only comes into effect when more power is being put down (seems obvious enough – hit the gas harder in a turn (with traction) and there is more torque steer from more applied force…)

BTW, when I had the Toyos on the stock rims, there was NO perceived change in torque steer…

Change in wheel offset makes the biggest difference in torque steer. Here is a picture and note:



"...If the car is FWD, the steering offset D will introduce torque steer. This is because the tractive force will try to pull the center of contact patch of the front wheels forward, thus the wheel will rotate about the point the kingpin axle projected to the ground. The torque steer moment is the product of D and the tractive force. Therefore the amount of torque steer is proportional to D...."

If you look at the picture, the outside of the tire would be 7mm further out due to the +48 offset vs. stock.

Full link: http://autozine.kyul.net/technical_s...handling_6.htm

Jeremyp80

If you are going to notice any difference at all....It may be a slight, and very slight at that, change when you accelerate. That is of course assuming that the wider tire weighs a little more than the stock...If it does weigh more, the rolling inertia of the wheels will be increased, thus consuming more power (from the engine) to accelerate them...The rolling resistance due to friction will contribute too if the rubber compound adheres to the road much better....The big question to find out is how much more (if any) will these tires weigh....

TypeSKid

YUP!

I agree completely!


The Toyos TOTALLY kick ass.


I can't believe the difference from the stock tires.

The stock tires are without a doubt COMPLETELY pathetic!

They aren't as strong, and can't handle the weight in turns as well as the Toyos.
WEAK SIDEWALLS.

EricL

Well, since you opened the "can of worms"... Some thoughts...


Yes, it would be better to find a lighter tire *and* if someone really wants to, they can get the weight of the tire by calling the manufacturer and talking to one of the engineers there.

As a "rough" rule, 1 lbs of reduced tire/wheel weight is worth about 3lbs of reduced static weight (hood, seats, etc, etc). (Lose 50lbs in tires and wheels [assuming that the weight was lost uniformly compared to the original tires and wheels] and this is like losing 150 lbs in "dead weight" on a car.

There is also the "presumption" that the weight difference between tires is homogenous. For example, there could always be the "odd" case of a tire that was actually heavier by a pound or two, but actually had much thicker steel belts at the very outside of the tire. In this case, the moment of inertia could be greater for the lighter tire and as such, the heavier tire would help the car to accelerate faster!

The tire weight table is rather sparse, but...

http://www.miata.net/faq/tire_weights.html

For Toyo, they list the weights in their tables
http://www.toyo.com/tires/tire_specsheet.cfm?id=2 (T1S)
http://www.toyo.com/tires/tire_specsheet.cfm?id=4 (FZ4)

Falken weights/info:
http://www.falkentire.com/html/produ...tirespecs.htm# (451)
http://www.falkentire.com/html/produ...5tirespecs.htm
(115)

Main page with links to more weight and other specs:
http://www.falkentire.com/html/index.htm


The guys who don't list the weights are generally pretty happy to find someone who will dig-up the data...



and for wheel weights...

http://www./tech/wheel_weights.html
http://www.mysportscar.com/features/wheelweight.htm

TypeSKid

THIS thread deserves to be archived!!!

Mods, archive or add to Chods FAQ please?

mlrspwr

I agree with the FAQ. This is great feedback for us "how does it really work" type of people like me. It is good to see some science instead of supposition. Thanx EricL for the technical feedback!
I do think the end issue is that there will ALWAYS be tradeoffs! You can't have a tire with the best traction that also allows the best fuel mileage and least rolling resistance.
I personally choose traction because I like taking corners fast, but others who drag a lot might choose a different tire type and size to suit their needs.
I think EricL talked about the OEM Michs as being "efficient tires" or something. True, but most people don't like them because of poor traction. But if fuel economy was paramount, then you'd actually choose the Michs over a most excellent tire like Toyo T1-S.
But let's face it -- we bought this car not because of fuel economy. If you did, please go to the geo metro board right now!

Red Rider

Since i went to the Toyo 225-40-18s i have lost 1 to 1.5 mpg. But the superb handling is WELL worth it

AztecRol

iTrader: (2)

AHAHAHAHAHAHAHAHAHA or the Honda Insight board!!!

http://www.insightcentral.net/

NOLACLS

WOW EricL Great info!! Send this to the FAQ!! I am NOT in the market for gas millage but I dont want to put something on the car that weighs it down and slows it up a lot. If the tires are sticky and that slows it a slight bit...so be it...ill get better grip. The weight was another thing I was wondering. I will try to get the falkens weighed before they go on the car to see what the true weight is. I hope its at least as light as the stock ones.

Again thanks every one for all the helpful input!!!

JasonT

EricL


Don't know man? My mileage hasn't gone down. Well... it has but only if I drive hard. Normal driving I haven't seen any decrease. I got better mileage between 5-10K miles, then I did 1-5K miles. I put the Toyo's on at 5K miles. Maybe the CAI makes up any difference? Or maybe my car is just werid?

lou_RENAMED

Thank you for the explanation, I didn't know which of the two was causing the torque steer. At first I was really surprised on how little torque steer my car had for a FWD(with stock tires)I guess those days are over.

EricL

If you put the CAI on about the same time as the tires, they could just end up "offsetting" each other. (It would depend on how hard you "hit the gas pedal"...)

I did the tires first, then the wheels. I lost about 2MPG around town with the tires on (I was hitting the same pump at the same station and noticed a difference in gas mileage with feather foot driving).

So, it's not like the needle drops like a rock or something. With this car, I find it pretty easy to get BAD gas mileage by:

1. Stomping on the gas up onramps.
2. Making sure I'm in plenty of stop-n-go traffic (pretty hard to avoid these days from 8AM - 6PM).
3. Avoiding traffic with short cuts though the back roads in the hills.

OTOH, when I noticed the change (big time), I was driving like grandma’s grandma.

I have no regrets -- the stock tires on a few roads with low abrasive properties were driving me crazy (nothing like having the front continue to want to go straight with the tires making enough noise to wake the dead!)