225/45/17 or 235/45/17 Tyres a good option?
 

Hi all,
I cannot get 15 semi slicks like 225 or 235 15 inch tyres over this part of the world.
My next available option that is available here are 225/45 and 235/45 17" tyres.

Would it be logical for me to go 17" or am I better off staying on 15"? Have anyone ran 235/45/17 competitively? Am I "under-tired" running 195/55/15 Hankook Z221?

The car is running 300bhp with 6spd and 4.1FD. I am using the car for time attack events.


https://www.miataturbo.net/attachmen...ine=1388246311

the problem with running 17" wheels in a track environment is it takes up a lot of available shock travel (not to mention your wheels can hit the fenders/other parts), which we need as much of it as possible.

definitely at 300bhp, you could use more than a 195 tire. I think the performance minded option is to find a dealer for 225 or 205 tires in 15".

Otherwise, its a toss up really, probably do what you find is best.

Ahh...shock travel. I should have thought about that. Thanks.
But having said that, the difference is slightly over 1" of travel between 15" and 17".
Which is the worse of 2 evil? Shock travel or traction?

225/45R15 = 23.1" diameter
205/50R15 = 22.7" diameter
225/45R17 = 25.0" diameter
235/45R17 - 25.3" diameter

definitely the tires making an impact with suspension components and/or the chassis are a concern here. We are talking about limiting your suspension travel by an amount greater than 1" for sure.

Plus there is going to be some performance disadvantages here. You will need to drop the car further to get near the same COG and ideal ride height. You will in that case take out more suspension travel, and put the tires closer to the chassis. Its probably not a linear relationship.
You can try to google info about this or just do some testing with one wheel to see what you would end up with. I would mount the tires on a borrowed 17" and put the shock on the car without a spring. Use a jack to move it around, adjust to your planned ride height and see what you will end up hitting and how much shock travel you will have left.

I don't really know, but I would stick with a 15" personally. Not sure I want to deal with the headache of making sure there is no components colliding, especially because that will lead to premature failure or excessive tire wear. with that said, tires are the most important part right? a tire change could change lap times by seconds. I wouldn't take internet conjecture for this question, definitely go out and run tests. You may hate a 17" as you will end up on the bump stops and lose whatever traction advantage you would gain from running a bigger tire. Plus sticker tires=need more suspension travel (or stiffer springs).

move up to a slick tire if you can find that more easily and run that in your class.

You are right, there are more variables i didnnt think of. Guess I just have to test it on 17 to find out. I don't have an option to go slicks due to regulations....

Yak - What are the import fees like from Japan? I would think there would be plentiful options from there and it is geographically much closer than Europe or the US.

Well, 225/45/15 yokohama 050 would cost me about $300 a piece landed. I could get it 225/45/17 for $200 a piece.

What compound in the 221 are you running? Assuming your running the soft compound you should only be able to get 2 hot laps in. Have you tried running the RS3 in 225/45/15 and experimenting with tire softening? I think you might run similar lap times on a 225 RS3 simply due to consistency and break away characteristics. I would do back to back testing with your 195 z221 vs RS3 225 on a 15x9 rim. I would also spends some time on your front aero, that front bumper is a parachute.

I was running 225/15 Nitto NT01 but even that would be on the limits of over heating at 300hp

I am running c5 compound for the z221. C3 is too soft and overheats by lap 2. Possibly it is also due to me being in a tropical country with 38degree Celsius track temp.
The front bumper does look like it has a lot of drag, but the carnard and splitters made 2s difference consistently in a 2min30s track. This is in Sepang Malaysia. One of the f1 track in the calendar.

I also tried 225/45/15 on rs3. Nowhere near z221 in terms of performance. But I didnt have tyre softener.

Actually what would be really nice to hear from this forum is if anyone had used 17 and find it useful.
I come from a country whereby 90% of the cars goes to the junkyard by year 10 of its lifespan. Its rare for people to be tracking old cars.

If you're looking for more tire than the Z221, and you can get that from a 17" tire, If I were you I'd try to make the 17" wheel work. It's not "ideal" but I think in the real world you can tweak and adjust to get suboptimal setups to do pretty well (I've had to do plenty of this myself).

I'd run really stiff springs, and adjust/swap bump stops as necessary to limit your suspension travel from allowing the tire to drastically hit the inner fenders. Last resort use bump stop spacers or "packers" to engage the bumpstop sooner and reduce suspension travel. I played with such spacers this past season to combat the severe compression I was getting from downforce. There were better ways to address it, but that was what I could do at the time, and I made it work.

-Ryan

The track is quite smooth, i am guessing bumpstop spacer may work. Will give it a shot. Cheers.

I'd rather have a 205/50R15 over any 17" tire. No amount of clusterfuckery you do to the suspension or bumpstops will ever cure the issues caused by putting a tire 2" too tall under the car. We don't have enough suspension travel to start with, and all you're doing is taking 25-30% of it away. The car will be a nightmare to drive and will almost certainly go slower.

My R1R's are 245/35-17, or 23.8" diameter with a 9.4" tread width. These aren't exactly track tires but the mechanical grip I get from this contact patch is pretty impressive.

If you can run slicks, I think that Achilles has a 17" slick that's 600mm in diameter (23 5/8") and good for an 8.5" or 9" rim.

No offense, but don't you think it's worth mentioning that your car is a tube frame with no inner fender wells for the tire to interfere with?

There is that. :) C'mon Savington, you don't have to sugar coat it when I screw up!

Actually, If I had a 300hp Miata and some access to tin snips, and an open rule book, I'd look at the 16" tires that Hoosier makes for the Radicals. Where there's a will there's a way, right?

The Achilles tires aren't that oversized, and if you're running a low offset rim then I bet even Miatas with mild flares can get away with it. I'm running +25. The link below should tell you if I'm blowing smoke up your ass:

Custom rims, wheel tire packages for your ride - RIMSnTIRES.com

I plugged in a 225/45-15x8 with +38 and a 245/35-17x8.5 +25 and the numbers didn't look too bad.

I've had naughty dreams about the 23.5x12x16 Hoosier slicks. Probably the ultimate Miata tire, although it would take an act of god to get them under the car. IIRC they want a 12.5" or 13" wide wheel.

Like I said earlier, the diameter is the issue. Flares will cure all ills when it comes to overall width (to a point - eventually you run into the tub when turning) but flares don't move the inner fender when it comes to diameter. That's why a 225/45R17 would be a nightmare to fit, but a 275/35R15 isn't too big of a deal.

The 245/35-17 is only ~.4 inch larger by radius than the normal 15" wheel options. IMO that might be workable. But with the R1R is a very low temp compound tire so it wouldn't be my first choice on a road course.

lol. Talk about sugar coating...

curious what the op ended up doing regarding tire choice. even more curious how a 195/55/15 ventus td soft ended up faster than a 225/45/15 rs3 on track.

Shall let some of you say "see I told you so"
Trial fitted 17" with 225/45/17, it looks physically impossible. Don't think the wheels can turn without raising it substantially. See front wheel pics here:

https://www.miataturbo.net/attachmen...ine=1392807386

So you're sticking with 195/55/15 ventus td softs?

Time to pony up some $$$ and import tires

Well, found some dunlop d03g 205/50/15 at $160 or spend a lot of money to import yoko 050 225/50/15 at $320.
Will try and see.

I don't suggest the 225/50 Once again the size is larger than what you can comfortably fit under the car. You might be able to squeeze it in, but its a compromise over a 225/45

Well I'm not God, so it doesn't take an act of God. Lots of cutting and a little welding. 12" wheel.

Post pictures of your baller, shot-caller wheel and tire set up or I will have you banned for insubordination :party:

I have run these exact tyres for half a race season and found them to be excellent. Dont count them out. I may not be quite as low as "suggested" but pretty close....

The 50 profile didn't rub for me much if at all (the sig picture shows these tyres fitted). The car handled amazingly well, very balanced with my setup.

I am trying to replicate the balance I had with that setup on my new 9" wheels and 225 nitto's...

P.S - I ran the Dunlop d03g 205/50/15 On a 7" wide rim BUT to also point out, a 6UL 9" rim and 225 tyre has proven to be apprx 2 secs a lap quicker, even with the car "balance" being out/not right.

50 profile isn't really expected to rub on a 205 tire...

Don't have any pics with those up front. The pic I attached is with the 23.5x11.5 bias, which is basically the same size as the 23.5x12 radial, on the rear. The radial is .3" shorter and has a .5" larger section width. In the pic on the front are a 22x10, which are .9" shorter and have a 1.8" narrower section width. When the 23.5x11s went on the front, the fender had to be trimmed more at the rear and the inner wheel well had to be "adjusted" more in the rear as well. They hang out pretty far and need some big flares to make it look good, but they do work. Too much tire for a depowered rack at autocross speeds, so power steering is going back on to see how that feels.

Sorry this is so off topic from the OP

205/50 is not the same height as 225/50.

I really don't understand why street tires are sized with one dimension relative to the other one. It seems like overall diameter would be a more intuitive and useful spec.

(And, for that matter, why they're spec'd with one dimension in inches and another in mm.)

--Ian

haha, not intending to be a smart ass, but...its the standard...
https://www.miataturbo.net/attachmen...ine=1392850743

:confused::confused::confused:

Your particular race tires are not the subject of his rant. :giggle:

The non-DOT racing slick world agrees with you - they're all dimensioned as width/diameter instead of width/aspect ratio (except when they're dimensioned in all inches). A 205/50, 225/45, and 275/35 would be dimensioned 205/580, 225/580, and 275/580 respectively.

It's not like it's confusing or anything, come on guys :giggle:

You know what the wonderful thing about standards is, right?

There's so many to choose from!

(old, old joke, from Grace Hopper I think).

But I haven't seen a standard stupider than the street tire sizing one since the ISO was still trying to convince people to use CLNP back in the early 90s...

--Ian

Yes I tried Dunlop D03G 205/15/50 H1 compound and Hankook Z221 195/55/15 C5 compound both on a 8" wheels.

I have also been on 195/50/15 Toyo R888 and 205/50/15 Federal Z201 and they have been outclassed by the Dunlop and Hankook.

I hope to try the Yokohama A050 one day but they are really pricey.

The dunlop does feels better and is consistently 1s faster than than the 195/55 Z221

This car ran 315/30R18 front and 335/30R18 rear at nationals in SSM both sizes are listed at 25.6” in diameter. I would really like to look close at their car. Every time I look at it I don’t see how you could allow the suspension to move or be able to turn without hitting chassis parts that are forbidden to be modified by class rules. It won SSML and finished 8th and 11th n SSM.

https://www.miataturbo.net/attachmen...61426215_n-jpg

https://www.miataturbo.net/attachmen...51627084_n-jpg

https://www.miataturbo.net/attachmen...69285992_n-jpg

Look at the monster truck ride height. Thats how he handled the loss of bump travel. I doubt he could get near steering lock, but even with the manual rack I never put in more than 1.5 turns on course. Wait till you see the abortion JoeFis racing is running this year, 275-15s front 275-17s rear.

Seems like even the raising the ride height at the sill seam weld by 4" over what I run to maintain some bump travel the front tires would still crash into the sill area by the firewall with more than about 15 degrees of wheel cut. Has me wondering if A-arms to move the front wheels forward by about an inch were used. The wheel openings are completely not stock and the body work looks amazing.

Somehow they made the compromises work as I don’t think it is a slow car. Not sure it’s the best way to go however.

Oh yeah, certainly not slow, both drivers beat me, their time gap was bigger on the POWAHHHHHH course than the technical course though. And there's a ton of money in the car, there's an efr under the hood if I remember right from impound. Remember he has an inch that he can hammer out in the sill area to gain more clearance before he's illegal, I think he can get enough steering lock to be fine on most national size courses.

Anyone ever measure their lower control arm (rear) angle in addition to seam height in order to see if your suspension is at the optimum angle? Speaking of which, what's the optimum angle? 0?

An inch? I guess I need to find that in the rules didn’t realize there was any leeway inbord of the wheel mounting face.

FWIW I beat Duke Langley all three events we faced each other last year including NT right before the championship. He finished 3rd and was in second after the first day. Makes me wonder if he stepped it up a notch somehow at the finals, he was quick!

Outboard of the hubface you can do whatever you want to the fenders in order to clear tires. Because its street mod you can modify pretty much any part of the car by 1inch and 1 pound to facilitate an otherwise allowed modification.

Um that changes the game a bit. 1" bigger intire inner fender?

That rule does come with the caveat to not take advantage of the rule. IE, dont fuck it up for the rest of us. I say hammering the living shit out of it is within the spirit of street mod. Cutting out, moving and rewelding sizable piece of the chassis is a no.

I still dont think the 315s are worth 200 pounds and 3 inches of width.

Yea I still question the tradeoff. If my car had to weigh 200 lbs more though I could run it in open track form all the time and keep the roll bar on maybe a cage. But I couldn’t imagine that size tire being faster on the track not to mention the added cost in tire budget.

Those are basically the same dimensions as the tires we have on the front. 1" is not enough clearance for an NA chassis. Can't say I know about any other chassis. I'm guessing the factory wheel well size increased over the years and models as tire and wheel sizes increased.

I have both NA and NB chassis bare gutted sitting side by side. The only advantage the NB has is in the outer fender lip area, which doesn't matter when looking at tires this big as both would still need to be modified there. The NB is 10mm wider per side in the rear and 5mm wider per side in the front but much of the inner fender shock top area metal pieces appear to be made on the exact same tooling. This change is the same as OEM width change in suspension and wheel offset made by Mazda but there was no change made to accommodate larger diameter that I can see.

I'd sure want to investigate the rear portion of the inner well if the car were in my class.