I went to the shop today and the person told me it is ok to put 225/40-18 even though the overall diameter will be smaller. He recommended 225/40-18 over 235/40-18 because he said wider tire will be more noisy, worse gas efficiency, and car may be slower.

So, would like to hear some input from you guys esp. those who have 235 tire installed.
1. Do you notice a significant decrease in gas mileage after you put 235 tire on?
2. Do you notice a significant decrease of acceleration esp. from a dead stop?

Thank you in advance

 

Your speedo will be off by 1.25% or 0.74mph @ 60mph. I wouldn't worry about it too much. Fuel economy and noise is bullshit. The difference between the two is minimal to none. The ride will be a little softer with the 235s and a little sportier with the 225s.

 

I know I am going to get flamed for saying this, however from all of my racing experience you want the narrowest tire possible to get the best of all worlds. I realize the tuner world is all about low profile tires that are really wide. However ultimately more important then handling is aerodynamics and the narrower the tire the more aerodynamic you are- get down on your knees and look at the car from the front, you'll see what I mean. Now on a TSX I don't think the difference will be substantial or possibly even noticeable- but whoever you spoke to is right the 235 will be worse on fuel economy and noisier(contact area is contact area- however the dB of the tires will change depending on the tire itself and the road surface) and possibly not even handle any better.

An industry standard is +/-5% is acceptable in the size department. In short if you can find a killer deal on an awesome 225 go for it you'll be fine(maybe even better off) if you have your heart set on 235's get them- I don't think you can lose either way.

 

The performance issue has more to do with sidewall flex than aerodynamics. The tires are well sheltered in the wheel wells of the TSX.

 

the 225 is fairly large. I wish I could see the difference with the 225 vs the 235. I have 225/45/17 on now and those tires look pretty damn wide. I went with the 225/40/18 because the width looks perfect and I really don't see the need to go any wider.

Also what size rim do you have? 7.5,8.0? I think that plays a part in deciding what width of tire to get too. If you like the 235's then go with them, overall it seems like it's a personal preference.

l8ers
Wess

 

I am confused by width do you mean sidewall height(aka the tires "profile") or are you reffering to the tires tread width? It sound like you are saying a 225/45-17 is wider then a 225/40-18 and the tire tread width is the same 225mm on both

 

I'm saying that 225 is wide enough for me. I was saying that my current winter tires are 225/45/17 and that my summer tires that I just ordered last week are 225/40/18. So I had the option of going 235, but I went with the 225/40/18. I ordered new rims and tires last week, the 225/45/17 are my Nokkian winter tires on the stock rims. Sorry for the confusion

Wess

 

Usually you want winter tires to be skinnier than your summer tires. I'd recommend 205 or 215's.

 

lol what fun is that? These tires were bought by the pervious owner at $250.00 a piece so I really can't complain. They give it a sporty look in the winter time and they seem to handle really well. There calling for a foot of snow by tomorrow morning, that's going to be fun...

l8ers
Wess

 

Thx for the info guys!

I think I will go ahead and put 235/40-18 on, because I want to have the same overall diameter.

I will order the wheels today and hopefully they will get to me in about a week

 

You guys know about this right http://www.miata.net/garage/tirecalc.html

 

I forgot about that one. Thanks CJ!

 

Thx.... but I am not worried about tire size at this point...
just want to know if that affects fuel economy, acceleration...

 

I have 235/40/18's on mine. THe acceleration difference. Well, I shaved close to 5 pounds or so per wheel with the rims. Plus the wider and MUCH sticker tires help acceleration grip.

Fuel economy is being affected mainly by the stickiness of the tires. I seriously doubt that it's due to the 2" bigger frontal area.

My goal was maximum grip. Thus, I got the widest tire I could.

Another thing to consider. With the 225 vs 235, the sidewall height of the 225's will be 0.16" smaller than the 235's (close to). Not a big difference, but it would probably be a bit harsher ride. Besides, on a 7.5" wide rim, the sidewall will have less initial flex to it with the 225.

So it depends...I wanted maximum grip, but my rim is a touch narrow for "optimum" performance. It is better for ride comfort and curbing though.

 

HAHAHA

Curbing = Road Head where I'm from. I'll have to get a set of those tires if it will get me laid!

 

Well if the wider tire is going to increase the acceleration then go for it. I got my rims/tires in yesterday and I wish I would've went with the 235 series tire. The lip of the rim would've fit perfectly with the 235 and that would've prevented curbing(it would hit the tire instead of the rim). The rim is 7.5 which people say a 235 seires tire would work just fine. I'd say go for it.

l8ers
Wess

 

wee~
thank you for the advice guys.
I am going for 235/40 -18!!!

 

just make sure that your rims can handle a 235 width tire... if the rim is too narrow it's going to look funny... to wide... and your tire will look like it's stretched on.

 

I think you can put them on a 7" rim, but I would recommend the standard 7.5" rim. Just about the perfect setup for me.

 

Why hasnt anyone answered me on the whole a spec tl rim 18 x 8.5 that was in tha last forums. Disadvatages to that. ????? anyone.

 

Wess---where's the pics man?

 

Too wide. Wrong offset. What else do you want to know?