So it's almost time to switch tires and I've been looking at the different size options. The tires are mainly for aggressive street driving...aggressive, more on cornering than on acceleration, but needless to say I don't like losing especially when I'm pulled up next to a civic with spinning hubcaps.

I have an MY06 MCS and I'm considering reducing the tire size to achieve a more aggressive gearing effect, but I'm concerned about a few things.

1) I'm running a stock suspension and I'm wondering how large of a gap this will leave between the wheel well and the tire. I can do the math so what I'm really looking for is pictures. I don't want Morgan to look ridiculous, although I may consider getting springs and shocks, but then there's the little thing called my warranty.


2) The reduction in tire size is going to cost me a fortune.

• The engine will be consuming the same amount of fuel to cover less mileage. A simple calculation using the 205/40-16 shows that when the engine has gone 300 miles, actual distance traveled is only ~275. Now, assuming a gas price of $3.00, lower than what I've seen in awhile, and 25 MPG, higher than what I've seen (~20 - don't ask, I have no idea what's going on here), it practically raises the cost of a gallon of fuel by ~ $0.25. To put that in perspective, you will have spent $2,500 more in fuel by the time you do 10,000 miles on those tires. At 215/45-16, the cost of fuel is raised by ~ $0.10, a $1,000 increase for 10,000 miles.
• My warranty is going to get eaten up by the change in size. Again, another simple calculation shows that I'll lose about ~4000 miles if I go to 205/40 and ~1700 if I go to 215/45, a warranty loss of 8.1% and 3.4%, respectively.

All these, lead me to my last question, is the more aggressive gearing worth it? I mean, I understand that everybody's tastes are different and whatnot, but has anybody done any testing/dragstrip/track time that yielded significantly better times from just the reduction in tire size.

 

Oh, by the way, if my calculations are correct, and someone please do check. Downsizing tires has to be the worst performance upgrade ever.

 

Okay, nevermind the gas aspect, I miscalculated it. It actually only increases gas cost by $100 per 10,000 for the 205/40-16 and $40 for the 215/45-16. So the arguments come down to how ugly it'll be and the loss of mileage on the warranty and if the increase in acceleration is that noticeable.

 

You worry too much.

 

It looks like you might need to spend a little more time driving and a little less calculating.

Ever wonder how the MINI knows correct speed and mileage given that it uses everything from a 15" - 18" OEM wheel and no manual adjustments? That is one smart car.

 

The gas mileage issue isn't always so clearcut. I know a lot of people that did final drive swaps on honda/acuras and didn't see a reduction in gas mileage. Maybe it's because those engines were better equipped to run at high rpm's...

 

Well, at some point this spring I'll let you know how tire size reduction works from a performance perspective. My reasoning was based upon tire weight first. The gearing leverage is a benefit. The handling might be an issue - these will be dedicated track tires. 205/40/17 Toyo RA1

 

I just figured the ECU was programmed with the OEM tire size and it wouldn't matter, but I could be wrong. Anybody know? I mean, if the ECU that smart then, the only negative is Morgan looking silly.


why do you think the handling might be an issue on 205/40? Are you running 215? At least for me, the grip should increase since I'm running the stock x-lites with 195/55.


If you think I think too much right now, you should've seen me when I was trying to pick out a car. :impatient


And finally, anybody have any pictures of downsized tires on stock rideheight?

 

The tire sizes within the MCS and MC models are all the same relative diameter. The ECU might be able to correct for speedometer error electronically, but nothing will change the physical gearing. Therefore, tire sizes must be very close...differeing perhaps by a few mm.

Handling...this is not scientific observation, just one that comes with experience. A 40 series tire requires lots of roll control in an effort to control roll camber. In theory, the shoulders of a 40 series tire are more square than a 45 series tire. The only way to use a 40 series tire is to control roll...and I'll only have the JCW suspension with a 19 or 22mm bar - Ireland engineering fixed camber kit too. I'm not sure that'l be enough. I'll know soon enough...

 

can the 205/40 be able to handle the lateral vehicle load?
when you say track tires, do you mean drag racing or road course?

 

krazyivan- you probably won't even notice the gear ratio change if it's only a 5 profile difference.

and yes, your car will look lifted even more.... especially if you run performance tires like 215/40/17 since the shoulders are much broader.

imho, just get the same size but get tires that are stickier than
what you have now.

finally... you will be amazed how well a stock 04-05 civic handles the turns...
despite it not being anywhere near performance handling feel. the car
is so easy to control.

 

The load rating difference between my stock everyday tires and the ToyoRA1 is 133lbs...not insignificant. Michellin 1,235 lbs vs Toyo 1,102lbs. So long as I don't transfer more than 350 lbs during any corner...I may have to rethink this...especially if I grab an instructor. I may actually transfer close to twice that onto the front outside tire. Stock runflats load rating is 1202lbs. I'm a hundred pounds off, but still, that's a lot. I need to add load rating. Road course only Kenchan.

I may also have to opt for an adjustable camber kit so I can dial in more neg camber; toyo says no less than 2.5 degrees as a general rule for even wear - on a track. That'll be too much for all my highway driving however. I was planning on purchasing Ireland's fixed plates.

 

Are there any negatives of going with a wider tire (i.e. - 215/50-16), but maintaining the same diameter? Is it possible to do 215/50 on the stock x-lites?

 

those x-lites are 16x7 or 16x6.5? if 6.5, there's going to be a lot of
sidwall flex since the rim is narrow.

you want the sidewall to be about even with the rim to a slight pulled
condition for maximum cornering response.

also, 215/50/16 is actually a larger diameter than 205/50/16...

215/50 = 107.5mm sidewall width
205/50 = 102.5mm sidewall width

 

Aren't the OEM tires for the 16" rims 195/55? If so, 215/50 is just about the right diameter, no? If I wanted to go 205, 205/50 is closer to OEM diameter than 205/55. But, why would I go thinner tires when I can go wider? I mean c'mon, size does matter sometimes.

 

Wider tires also change offset - even if the wheel width remains the same. How camber affects a wider tire is also a concern, depends upon the setup

In the end, it's a compromise, and, an iterative process. I may decide to get the toyo's anyway and see for myself. Nothing like - calculated - first hand experience.

If you install too wide a tire on too small a rim, the contact patch is no longer the same as advertised - read not optimal. As Kenchan eluded to, this condition also lengthens the sidewall of the tire causeing more sidewall flex. It lengthens, becasue the tire side wall, in an effort to meet a rim that is farther away, lifts the outer portions of the contact patch off the ground. So the contact patch becomes more narrow. and we all know the a wide - left to right but short fore and aft contact patch is great for cornering. There is one optimal tire and wheel combo...everything else becomes a compromise in either direction.

 

If you're looking for better pickup off the line I wouldn't worry as much about the size of the tires effecting the gearing as I would the weight of the wheel/tire combo. I don't see where you indicated the current wheels/tires, but generally if you go to a non-runflat from a runflat and get some lighter wheels you'll get at least as noticeable gain, with BETTER mpg instead of lower mpg. Also if you get a different wheel you can get one with the correct offset to run whatever size tire works best for you.

 

I'm running on the stock x-lites with the OEM runflat tires. I think it's the Dunlop 3000a DSST. I'm really not looking into buying new rims right now. The x-lites are sufficiently light for the time-being and the $1000+ that I would need to be spending on rims doesn't justify the marginal improvement. What can I say, I'm cheap and very specific about what I want.

Regarding stickier or lighter tires, I looked at tirerack and they didn't have very much choices for 195/55-16. I took these from the sticky.

195/55/16
Bridgestone Blizzak WS-50 23 lbs WS50

Continental TS 790 18.0 lbs Ts790

Dunlop 3000a DSST 23.6 lbs 3000A
Dunlop 5000a DSST 23.5 lbs
Dunlop Winter Sport M3 DSST 24.01 lbs M3

Firestone Firehawk GTA 02 20 lbs GTA 02

Goodyear Eagle NCT 5 22.58 lbs NCT 3
Goodyear Eagle NCT EMT 5 22.58 lbs

Ruling out Firestone just because I've never heard good things about them. The Continental is an high-performance winter tire so I assume it's less sticky than the Dunlops. I live down in Houston, so snow isn't exactly the biggest thing on my mind. Without those two, the weight differences are minimal, 1 pound at most, but the Dunlops Runflats are in a sportier category than the Goodyears, whatever that means and for a 1 pound difference, I'd much rather keep my runflats.

Seeing how the 195/55-16 is so limited, are there any other possible sizes I can go without too much harm on the stock x-lites?

 

Keep in mind where the weight is too; two 35lb packages (wheel and tire combo) may posses very different weight proportions. One may have 23 pounds at the circumference while the other has 20. Braking performance improves with the latter, for example. A 4-6 pound difference - total package - using the lighter tire example will make a noticable change in braking. That is basically the difference between my winter and summer combos.

The new style runfalts are apparently lighter, so you can have your cake and eat it too.

 

You like calculations? Go here... http://www.1010tires.com/TireSizeCal...?action=submit

215/50 will put you in the right diameter range, but as kenchan said, you might have issues putting 215 tires on the 6.5 inch wide X-lites. Maybe alex can chime in on the facts regarding that claim.

mb

 

A 215 should be mounted on an 8" wide rim - ideally. This, so you gain the benefit of a wider tire; the entire contact patch, at the correct psi, remains in contact with the ground.

 

so it's everybody's consensus that I shouldn't go any wider than 195?

 

Toyo makes the T1R in 195/55/16 and it weighs 18 pounds. http://www.edgeracing.com/tire/2209/

 

Wow, thanks, 5 lbs off the Runflats. Do you have any personal experience with the toyos? I just took a look at the caranddriver review of the tire and it placed 8th out of all the 11 or 12 tires. They didn't seem to like it very much. The Goodyear Eagle F1 GS-D3 placed 1st.

http://www.caranddriver.com/article....&page_number=1

However, thanks for the info about the Toyos. I just assumed tirerack had every major brand. But with its poor showing in the caranddriver test, I'm leaning toward maybe getting some 195/xx-16. The Goodyear Eagle F1 GS-D3 comes in 195/45-16, but a 10 point profile jump is pretty big... Unfortunately, the Yokohama Advan Neova AD07 doesn't come in even a comparable size.

For a smaller profile jump (i.e. - 195/50-16), the Kumho Ecsta SPT/Supra 712 and the Michelin Pilot Exalto become decent choices also.

Anybody have feedback on the Kumhos, Michelins, or the GS-D3? Sigh, choices, choices.

 

I did all of this research and decided on the GS-D3s in 205/50. That is a widely used size for the x-lites and will reduce your gearing a bit.

Now for the weather to turn so I can put them on.

mb