What would GRM do? 225 width tires on 7" wheel?

Good evening all. I scored a set of cheap wheels for my wife's 1st gen TSX and want to put a good set of summers on them. Unfortunately, there's limited availability in the stock 215/50/r17 size. 

Current tires 215/50/r17 DWS 06
Wheel size: 17 x 7 + 55 (Same as stock)
Stock tire size: 215/50/r17
Available sizes: 225/45/r17 , 205/50/r17, 225/50/r17

Tirerack lists alternate sizing the TSX as 225/45/r17, so I'm assuming that size would work, but most of what I've read on the internet say 205/215 would work better on a 7" wheel and 225 might lead to mushy turn in.

The car doesn't see many miles so I'll be stuck with these tires until they age out or if I end up tracking the car and burning through the tire. I'm looking at 2nd tier 300 tw tires (indy 500, g-max rs) 215s don't seem to be available anywhere. All of my alternate sizes are available and rather cheap (~450 after rebate and discount for a set).

What size would you guys go with?

205s: less weight, most appropriate size for the wheel

225/45s: closest in diameter to OE setup

225/50s: more sidewall, which i've read is better when mounting on an 'undersized' wheel

Im running 225/45/15 on 15x7 on my neon. No issues. Still has crisp turn in. And even wear.

My racecar has 225/50R16s on a 16x7. With the inflation pressure we run, they aren't mushy. More rubber is good!

One of the things I do is take it out on the stock tires and compare the speedo to a GPS speed on your phone.  Most factory speedos read a couple MPH over what you're actually doing.  It's not that I have OCD, I just like accuracy, so if I have to choose a slightly different tire size I don't want to go in the wrong direction and make my 2mph inaccuracy into a 2.5 mph inaccuracy.

In those three sizes, take a look at your offerings in the summer category.  You might find that the actual treadwidth is remarkably similar.  Don't assume that a wider section always equates to wider tread.

Otherwise, I doubt you'll notice much difference, but I agree with the more rubber idea.  I don't see any issue running 225/45 on a 7" wheel.  Don't call it "outside of specifications," call it "supplemental engineering" and it will be fine.

I run a 225/45-15 on six inch wheels on my autocross Miata. 

How about 215/45R17? Tire rack has Indy 500s, PS4s, and Conti ECS for that size in stock. I am shopping for similar tires for a set of 17x7 wheels and that's the size I plan to run (stock is 205/45 in my case).

Tire manufacturers publish a list of acceptable wheel widths for each size of their tires.  You can look it up, but I'd be very surprised if the 225s weren't considered safe on 7 inch wheels.  Performance wise they'd probably be faster on 8s (or even 9s), but that's a different question.

Is there enough lateral clearance to get the wider tires on there?  Some suspension geometries are not very forgiving in this regard.

I would not go with the taller sidewall, that is more likely to cause rubbing.

225/45 would absolutely be my choice.  When you land on a few top choices, look up the actual dimensional specs on each tire. I was surprised to find that they in fact can vary quite a lot much like clothing.  In other words, 3 different manufacturers' 225/45 tires could be 3 different widths and 3 different heights.

codrus (Forum Supporter) said:

Tire manufacturers publish a list of acceptable wheel widths for each size of their tires.  You can look it up, but I'd be very surprised if the 225s weren't considered safe on 7 inch wheels.  Performance wise they'd probably be faster on 8s (or even 9s), but that's a different question.

Is there enough lateral clearance to get the wider tires on there?  Some suspension geometries are not very forgiving in this regard.

I would not go with the taller sidewall, that is more likely to cause rubbing.

 

 

Some tire stores, Discount Tire in particular, won't mount tires on a wheel wider than what is printed in the tire manufacturer's' specifications for that tire.

When I wanted to put 205/50-15's on 15 x 8 wheels Discount Tire would not do it. They said the tire's specifications say 7.5" max.  So I went to National Tire and Battery right down the street.   No problem they said, we do this all the time.   This combination is very common in Miata land.

I use 225/50/15 on 15x7's no issue.  even 235/60/15 on 15x7  works good for me.

Like a lot of Porsche 993 drivers I've run 225s instead of stock 205s on the 17x7 fronts for decades. Better turn in with reduced understeer on that car, should be no problem on the TSX. 

Tire Rack has specs for each size of tire by model, with the wheel widths specified, as well as diameter, revs/mile, etc.  I use this as a reference.  Also - have 225/45-17 on my Mazda3 and 225/45-15 on the Miata.

Well, by jiggers, back in the olden days when there was only 10 sizes of tires, the factories used to ship all sorts of trucks with 235's on 7 inch wheels.

78 series, but still...

A 205mm tire on a car like that sounds less than ideal as you're giving up footprint and load capacity. 

Thanks guys. I'll order 225/45/r17s g-max rs's tonight. Minimum spec wheel is 7".  I just tested fitted the wheels I purchased to make sure brakes clear. They're NC1 alloys. Same fitment as mid 2000s honda/acuras but at 17lb compared to 21 lb stock and dirt cheap. 

Are hubcentric rings recommended/required? The NC1 alloys take a tapered lug if that makes any difference

In reply to maschinenbau :

I think 225/45/17 will be too short for what the car is used for. I have very mild lowering springs on it and the pitches of some driveways require careful maneuvering. I'm hoping to change my springs out for a ground control sleeve later on, but wanted to see how the car behaved on a summer tire first. The retailer I'm looking at has 15% off for tires shipped to an installer (including ECS/PS4s). I know tirerack is a sponsor for many things motorsports  & grm, so I didn't want to 'promote/reveal' the retailer, unless the big guys say it's okay.

edit: The g-max rs aren't avaivable with an XL rating from this retailer. Looks like I'm going for the big boy ps4s

Gearheadotaku (Forum Supporter) said:

I use 225/50/15 on 15x7's no issue. 

Fun fact, this was the factory wheel and tire size on many Fox body Mustangs. If it's good enough for the factory, it's good enough for me.

Floating Doc (Forum Supporter) said:

I run a 225/45-15 on six inch wheels on my autocross Miata. 

How is that working out for you?

I've been wondering about 205 vs. 225 on narrow wheels. I have a set of 6" Miata wheels and a set of heavier unknown brand 6.5" wheels. I'm trying to decide which tire and wheel to go with. Is the extra half inch of width worth the added weight of the heavier wheels? Will the 205 perfom just as well as the 225 on 6 - 6.5" wheels? The car has over 200hp so traction can be a challenge, leading me to wonder if a staggered setup (205 front and 225 rear) would work better. (Possibly crisper steering with the 205 up front and more meat for acceleration with the 225 rear??)

Yeah for a 17x7" wheel the 225/45/r17 would be a fine choice. As diameters go up you can get away with putting wider treads onto a wheel of the same width without getting squeezed sidewalls. A 225-wide tire on a 15x7" wheel would be a significant squeeze for example.

I ended up going with a 225/45/r17 PS4S. I saved a whopping ~8lb per corner compared to the OEM wheel with a 215/50/r17 DWS06.  (38-38.5lb  with the NC1 wheels/PS4S and 46-47lb on the OEM/DWS06s).  I went out for a brief test drive and the car is much happier and still looks stock.

In reply to bigben :

Sorry, didn't see your reply to this thread. 
 

The 225/45-15 Rival 1.5 has been one of the fastest tires on E Street Miatas for years. You can look at the results from Nationals and see all of the 99 Miatas, every one of them has to be running a six inch wheel, as that's the maximum width allowed for that car in street class.

Previous owner of mine trophied at Nationals in 2018, and I bought it with three sets of wheels, all with those tires.

 I've never seen anyone run a staggered setup on a Miata.  My car is strictly autocross and I rotate the tires front to rear every event, too.

A lighter wheel is a big improvement for my car. I have a set of the stock wheels which are a very good wheel and pretty light at 13 pounds, but when I put the eight pound SSR wheels on it I can really feel the difference. I think a lighter wheel is going to be a better choice than a heavier wheel that only gains you a half inch in width.

In reply to lnlds :

Rock on. Glad that it all worked out.