tire sizes

[murph]

My car has 215/45/17 tires from the factory. If I wanted to mount lower profile/wider tires on my same rims, would that be legal in stock class? So say when I eventually go with Azenis or something similar, would 225/40/17 or 215/40/17 be ok?

Thanks in advance.

Matt

[StevenMosley]

It is legal.

I have 215/40R17 Kuhmo MX's on the front of my car. Check with Dwight on ordering you some MX's. I think you will be happy.

You can also change the struts, front sway bar, and cat back exhaust.
Camber/Crash bolts might also be possible in stock.

[murph]

225/40/17s here I come! =]

Do you drive the MP3 I've seen doing so well?

What's the difference between the Kumhos and Azenis?

I looked on the discounttire.com site and the Azenis they have listed there must not be the Azenis you guys talk about, the treadwear rating on them was like 300 something! The rating on my stock Potenza RE040s is 140... ?

[MNbiker]

Any DOT-approved tire you can fit on the stock wheels will be legal.

The Azenis have stiffer sidewalls than the Kumhos, so they have a more precise "feel" than the Kumhos. They also handle cold/cool weather better. If your car is heavy (say 2,800 lbs or more), the stiffer sidewalls on the Falkens will be more helpful/noticeable.

The Kumhos come in a lot more sizes and handle heat better than the Falkens.

The Falkens you want are the Azenis Sport. The only 17" sizes are 225/45-17 or 245/45-17, so the Kumhos might be a better option, if you do want/need a smaller diameter tire to lower your gearing. Note: Kumho doesn't make a 225/40-17. They do have 215/40-17, 225/45-17, 235/45-17, 245/40-17 and others.

-Steve

p.s. One other thing - the Kumhos need to either be driven a few hundred miles or shaved before they'll provide optimal autocross performance. The Falkens are fast immediately.

[StevenMosley]

Originally posted by MNbiker
p.s. One other thing - the Kumhos need to either be driven a few hundred miles or shaved before they'll provide optimal autocross performance. The Falkens are fast immediately.

I didn't know that one. So I can look forward to more grip. :)

The other thing to consider is that Falken’s also tend to weigh more and have a wider section width then labeled. I remember sitting Kuhmo V700's next to Falken Azenis Sports that were the same size and could see that Falken's noticeably wider.

Do you drive the MP3 I've seen doing so well?

No, I drive the Red MR2 Gen2 that is a work in progress. Negative Camber and reduced stiffness in front are on the agenda.

[murph]

Hmm, I think I want Azenis, but the 225/45/17's apparently rub on my car, so it looks like those are out.

Ideally I'd like 225/40/17's, but the only tires I can find in that size at Nitto 555's, which don't seem like autox-level tires, and are expensive.

I could get the Kumhos in a 215/40/17, but I feel like I'm wasting potential grip! =]

Bah, I suppose it's academic until I actually wear out my current tires, which could be a bit.

[rdub]

remember too,if you run Kumho V700s or Victoracers you wiil be in Race rubber class not Street tire class,like the Azenis run in.Azenis are not faster than either of the above mentioned Kumhos ,they will be close when the weather is cold or rainy but thats it.
#97 SVT Pinto

[murph]

ok, bringing this back out, as it may actually be relevant for me now...

I think I'd rather go with Azenis, but they just won't fit. I don't want R compound, because I want them to be (summer) daily driven.

So is the Kumho MX a good choice? Any other recommendations?

Then the other question, go with 215/40-17 for the lower sidewall, or 215/45-17 for the slight width advantage? (stock size)

I ask now because it looks like Santa might bring a set of these for Xmas. =]

Thanks!

[73GT]

So Randy the 3 month lease is up on the MINI;)

Also the Azenis are about the noisiest tire out there that just get noisier with age! Just look at the tread design and you go Da! They also aren't very good in the rain if you use them as a daily tire.

73GT

[magicsammy]

Originally posted by murph

So is the Kumho MX a good choice? Any other recommendations?

Thanks!

I bought a set of these for my VR-4 in the spring and I am very happy with them.

They feel good, have good grip and I didn't think they were too noisy.

I did wear half the thread off at Evolution school though but that was like 25 runs at Midway.

All the reviews I read said they were the best for the price, you can get slightly better tires at almost twice the cost. I recommend them.

[914 Dave]

I have the Azenis on the 914, and like them for a street tire. They are a little loud, but an air-cooled car is not known for being quiet! They are not the tire you'd put on a camry, so to expect them to be quite and all season is wrong. Their grip in the rain is, well, questionable, but driven w/restraint they'll get you where you are going. About 1/2 way thru the second season of street driving/auto-x they started to go away- by the last valley fair, I think those camry tires would have had better grip- the Azenis were slick as snot! Overall, for a cheep street tire class tire I was satisfied I got my $ worth and then some. I have a friend w/MX's on his Focus and he loves them, so do your research, pay your money, and have fun.

[pinhead]

My Azenis were a heck of a lot better in the rain than I expected them to be. Not that they were super-great, but from looking at the tread, you'd expect them to be almost undriveable in rain, which I didn't find to be the case at all.

Although I bet they are awful in the rain once the tread gets thin, which can happen sorta fast... I sold the car (with the azenis on it) before the tread got low enough to change how the tires drove in the rain.

[murph]

so no input on lower profile vs larger grip patch?

[StevenMosley]

Here is a good tire size calculator.
http://www.1010tires.com/TireSizeCalculator.asp?action=submit

As far as the Kuhmo MX vs the Falken Azenis after running a season on the MX's
I would say they are a better street and track tire, but not a better autocross tire.

Autocrossing:
They take a little more work to get heated up. On the front on my MR2 I could get the rears up to operating temps just by dumping the clutch and praying they would grab, the fronts would never get up to temp and the car would have a lot of push that was not an issue when I ran Toyo RA-1's for the last event. For your car it will be a little tail happy, but a little oversteer is not a bad thing.

Track Events:
Falken's would be pretty greasy after 2 laps. The Kuhmo MX's would warm up and then stay consistant through out the session.

[StevenMosley]

Originally posted by murph


so no input on lower profile vs larger grip patch?

Go with lower profile. It will give you better feel due to less sidewall flex and it will not raise your car, but lower it almost a half inch. The other benefit will be you will have a lower gear ratio that will help you pull out of slow corners.

Size---------------Diameter--------Width-----
-------------------------------------------------
225/45R17 _____24.97 inches____8.85 in
215/40R17 _____23.77 inches____8.46 in
215/45R17 _____24.61 inches____8.46 in

[murph]

I'd rather have Azenis, but I don't think they make a size even close for me. 225/45-17s will rub on my car, is there a way to get spacers to give me 3-4 tenths of an inch?

For some reason I thought it was the 215 number that varied with the sidewall height, but it's the other way around.


Correction, I guess I'd only need 2 tenths, which is still more than I have, so I'd still need some sorta spacers. Recommendations? Is that even legal in stock class?

[StevenMosley]

Spacers are not legal in sotck class unless you are using them with a rim that is not within the stock offset.

They are making Falken's in your size next spring. You will have to wait for the easter bunny to bring them though.

New Falken Azenis (http://forum.mnautox.com/phpBB2/viewtopic.php?t=1943)

[murph]

oh, the PAIN!

well, thanks a lot for all your help. =]

[rdub]

you can run wheel spacers in stock class as long as they don't go over the Scca's
limits of + or - .25 (1/4) (approx.6mm)from the stock offset.
The mazdaspeed and Mp3(I used to own and race Barrys Mp3) do have tire size issues in stock form.I would try to squeek as much tire under the car as possible(at least the front anyway) We use to race stock sentra SERs and miatas with bigger front tires than rear.The car could actually use a little more side wall,so I'd go slightly taller and wider. We had trouble on the MP3 rolling on to that short square edge,not quite enough give in the sidewall for a stock vehicle ,and just shredding the crap out of it.Once you went past the limit of adhesion ,the car broke away quickly,with not much window to catch it. And yes Lee the MINI is for sale

[pinhead]

Originally posted by rdub
And yes Lee the MINI is for sale

Sooooo..... Gonna sell those wheels :D

[Dave Kral]

Originally posted by murph


so no input on lower profile vs larger grip patch?

A common misconception is that a wider tire has a larger contact patch than a narrower tire. The size of the contact patch is determined by the weight on the tire and the air pressure. A tire with 800 lbs on it and 40 psi inside will have 20 square inches of contact with the pavement regardless whether its a 185 or 245 section tire. It's just the shape of the patch that changes.

The lower cross section is better for a couple reasons as mentioned by both of the Steves (G and M). Less flexing on turn-in and better overall gearing.

[AlexL]

Originally posted by StevenMosleySpacers are not legal in sotck class unless you are using them with a rim that is not within the stock offset.
Wrong.

Rule 13.4 in the 2004 Solo II rulebook:

"Any type wheel may be used provided it complies with the following: it is the same width and diameter as standard, and as installed (including wheel spacers if applicable) it does not have an offset more than +/- .25 inch form a standard wheel for the car. The resultant change in track dimension is allowed.

[don't feel like typing crap about how you can use 13" wheels if your car came with 12" wheels]

Wheels spacers are permitted as long as the resultant combination complies with the offset requirements of this section.

[more crap about wheel studs, lugnuts, and metric rims]"

[AlexL]

Originally posted by rdubWe use to race stock sentra SERs and miatas with bigger front tires than rear.
Randy- Tell me more about running different sized tires on a miata.

[73GT]

Hmm Maybe a SVT Orange Capri Randy? It would be nice to see it out again;)

73 GT

[murph]

oh, you guys had to make it hard on me again...

So I looked up the actual width of the 225 Azenis, which someone mentioned are a little wider than advertised, and they're right, 9.1 inch vs 8.85 for the tire size calculator width. So the width difference between stock 8.7 inch RE040's and 225 Azenis is about .4 inch, so I could use them if I got .2 inch spacers. (slightly over 5mm) According to folks on the msp boards, the 5mm spacers work with 225's until you push it pretty hard, but I'm guessing Autocross is gonna fit that definition, and they weren't talking about Azenis, which are wider than most. hmm.

The kumhos list their 225 tire at 8.9 inches wide, which would mean it'd probably fit fine with 5mm spacers, but the 215 is probably the better idea at 8.5 inches.

So I'm still stuck. Gonna have to noodle on this one for a bit I think.

[rdub]

Alex ,we ran 225s on the front and 205s on the back for nationals
They didn't work well here though.

[StevenMosley]

Randy, When does your C6 come in? :beer:

[rdub]

Thanks for starting that rumor Ha Ha Steve
But you never know ,if the MINI sells

[aansorge]

Randy, Please, PLEASE do not get a 2005 Mini S and run in GS.

[MNbiker]

Originally posted by aansorge
Randy, Please, PLEASE do not get a 2005 Mini S and run in GS.

Pretty much guarantted fast PAX every event, if he does. ;)
(of course, he might do that anyway!):p

[DCM]

Hey Murph
You know that lower is at least as good as wider?

I've kept the 14 wheels on my 'B'. And went from 205X55X14 tires, to 185X55X14 , and it lowers a the car about 1/2" or so.
And they weigh less.
Dwight

[MNbiker]

Originally posted by DCM

Hey Murph
You know that lower is at least as good as wider?

I've kept the 14 wheels on my 'B'. And went from 205X55X14 tires, to 185X55X14 , and it lowers a the car about 1/2" or so.
And they weigh less.
Dwight

But 225/45-13's would be faster! ;)

[phile]

>The size of the contact patch is determined by the weight on the tire and the air pressure. A tire with 800 lbs on it and 40 psi inside will have 20 square inches of contact with the pavement regardless whether its a 185 or 245 section tire.


This is true if the tire has the structure of a rubber balloon. In practice, the contact patch will be less than 20 square inches. The size of the contact patch is determined by the weight on the tire, the air pressure, and the structure of the tire.

load / pressure = patch is not correct in practice

load / pressure > patch is correct in practice

We went through this whole discussion on autox@autox.team.net a decade ago.

There are many variables in finding the best traction. Tire structure is an important one.

[MNbiker]

Originally posted by phile

The size of the contact patch is determined by the weight on the tire and the air pressure. A tire with 800 lbs on it and 40 psi inside will have 20 square inches of contact with the pavement regardless whether its a 185 or 245 section tire.



Yes, but the size of the contact patch doesn't determine cornering traction. A wider tire provides a wider contact patch, which provides more traction under lateral loads. If this weren't so, everyone would be running 165mm tires!

Now, there is a point of dimishing returns in tire width, typically limited by one or more of the following factors:

unsprung weight - bigger/wider weighs more.

The ability of the car's suspension to keep the rubber in contact with the road.

The ability to heat the tires to operating temperatures. Too much tire on too light a car will never get warmed up.

-Steve

p.s. I can tell we're getting bored with the off-season allready.....



-Steve

[fitz]

Originally posted by MNbiker


Originally posted by DCM

Hey Murph
You know that lower is at least as good as wider?

I've kept the 14 wheels on my 'B'. And went from 205X55X14 tires, to 185X55X14 , and it lowers a the car about 1/2" or so.
And they weigh less.
Dwight

But 225/45-13's would be faster! ;)

Except they will then foul the brakes, such as they are on a MGB.

[MNbiker]

Originally posted by fitz
Except they will then foul the brakes, such as they are on a MGB.

Those things have brakes? ;)
Mine never did much good, other than spraying brake fluid on the ground at regular intervals.....or was that the clutch?:p

[DCM]

OK Mnbiker, put up yer dukes!:flame:
Them's fightin' words!

Brakes?
I don' need no stenkin' brakes!

Fitzy, what'aya' mean, foul the brakes?
Tire rub?
The wheels i got from your Dad just are too deep of offset to run the 205 tires, with the suspension set where I have it.

Isn't the 'silly season' fun?

Bench racing, aaahhhh!

Hope the ice comes soon.
Dwight

[murph]

Originally posted by DCM
Isn't the 'silly season' fun?

Bench racing, aaahhhh!


wwweeeee!!!

Well, it looks like we've competing theories about what makes for good traction. The gentleman with the MP3 (almost identical car) says the lower profile tires weren't enough, and I saw what they looked like when he stopped running at VF! yikes! So at this point I think I'm leaning towards the Kumhos at the stock 215/45-17 size, partly because I don't think Mazda was wholly inept in putting this car together, and they've proven (to me at least) they knew what they were doing with the suspension. I wish I could get tires that wouldn't take so much to warm up, but it looks like that's in the cards for next year.

Anyone have anything to add?

[MNbiker]

Murph,

I just glanced back through this thread, and noticed one factor that wasn't mentioned. Lower profile tires are typically far more camber sensitive, which creates problems for most Stock Class cars. Unless you can get -2.5 degrees or better in front, you will likely have issues with 40 or 35-series tires.

If there's any way you can make the 225/45-17 Azenis fit with spacers, that would be my first choice. Otherwise, I think you're on the right track with the stock size Kumhos.

-Steve

[fitz]

Originally posted by DCM


OK Mnbiker, put up yer dukes!:flame:
Them's fightin' words!

Brakes?
I don' need no stenkin' brakes!

Fitzy, what'aya' mean, foul the brakes?
Tire rub?
The wheels i got from your Dad just are too deep of offset to run the 205 tires, with the suspension set where I have it.

Isn't the 'silly season' fun?

Bench racing, aaahhhh!

Hope the ice comes soon.
Dwight


Foul as in interfere with (foul is I believe the proper British way to put it). I don't think 13" wheels fit on B's as they won't clear the brakes. I've never seen it done anyway.

[fitz]

Originally posted by MNbiker


Originally posted by fitz
Except they will then foul the brakes, such as they are on a MGB.

Those things have brakes? ;)
Mine never did much good, other than spraying brake fluid on the ground at regular intervals.....or was that the clutch?:p

Yes, complete with an early and highly sophisticated system known as British ABS.

[MNbiker]

Originally posted by fitz
Yes, complete with an early and highly sophisticated system known as British ABS.

More than once, I've had the "pleasure" of my British ABS in action as I coasted through an intersection. :p

Note: this is second only to the "joy" of driving 3 hours home from college, with a non-functional clutch pedal. :barf:

-Steve

[DCM]

Been there, done that.............

Just think of the character it has built into you Steve..........

[maybethatswhyi'msuchacharacter?]

Safety Fast [that's an MG thing]
Dwight

[larry200]

The way the master cylinders were attached to the common fluid reservoir on my MGA, the clutch always "told" me about the loss of fluid before it affected the brakes. Just one more "safety fast" feature from the fine folks at Morris Garages.

-- Larry Bereuter
STS Subaru 2.5RS

[DCM]

I am surprised that nobody has brought up anything about Skinners Union carburetors. [S. U.]

And then what about Lucas electrics?
[Lucas, Prince of Darkness]

Allright all you British bashers, I worked on German cars professionally for 28 years, what would you like to know?
And then the early Japanese cars...........................

[herewegofalminagain]
Safety Fast [it's a MG thang]
Dwight:dancin:

[StevenMosley]

Murph,

Looks like you are going to have some Mazdaspeed Protege company this year in DS.

:alc: :beer:

[pinhead]

Originally posted by StevenMosley


Murph,

Looks like you are going to have some Mazdaspeed Protege company this year in DS.

:alc: :beer:

Did you buy one Steve? Or your brother? Cool :dancin:

[StevenMosley]

Chris did. Let the battle of the Turbo's begin. :)