Tires/Size

[GotMINI]

Is anyone out there running 225/45/17 on there 17" Rims ? Any problems ? I just ordered a set of Continental Extreme Contact DW for my 03. I am currently running the Extreme Contact DWS 205/45/17"s. I wanted some Summer tires vs. running the all weathers all year long. The 205's look small and way too much clearance. I want to go with a meatier tire.

 

I spoke with a Rep at Tire Rack about a week ago and he said that a 225 would be the biggest he would go. Then after ordering today, I got a call from another Rep wanting to know if that's the size I really wanted. Suggesting they were too big.

 

Help, anyone running 225's with Stock suspension ?

[Edge]

There are three things to be concerned with in changing the tire size like that:

 

1) Fitment onto the wheels - are the wheels themselves wide enough to mount that size tire?

2) Clearance in the tire wells - especially when the car is loaded down, you go over heavy bumps, or when you have the steering wheel at full lock. I recently discovered that only a 5mm wheel spacer on the rear wheels caused tire rubbing in the rear wheel wells on my car... and that was with the stock 205 size!

3) Speedo/odometer differences - different tire sizes cause a different wheel diameter (and therefore circumference), changing your speedometer and odometer values slightly.

 

I can't personally speak to the first 2 concerns - that depends largely on your exact setup. I have seen many people move up to 215s but not many that went to 225s. Others can probably speak to this better.

 

As for concern 3 - I highly recommend plugging in your stock tire size and proposed tire size(s) into the Miata.net Tire Size Calculator. Fantastic tool! In the case you gave, it shows that the 225/45R17 size will cause your speedo to run 2.9% slower, so when it says you are doing 60mph, you're actually doing 61.8mph. Now, BMWs & MINIs intentionally inflate the reported speed anyway, so this would probably make your speedo more accurate. However, the odometer is accurately calibrated, so this would cause your odometer readings to go off (2.9 miles every 100 miles!)

 

For this reason, if you really want a 225 tire width, I recommend checking to see if 225/40R17 is available instead of 225/45R17. The % differential between that size and your stock size is only 0.7%.

 

Just food for thought. I'm sure there will be much more info coming from others.

[GotMINI]

Thanks for your input. I also read that anything from 3% or less is fine. When speaking with the Rep he stated that I would have an 8/10" larger all the way around in Diameter. Width I am not worried about. After I measured my wheel well, I have at the smallest clearance spot, 1.5" and up to 2.25" where I think it matters most. I don't load my car, except for my Fat A$$ !

 

Any other input from others is welcome.

 

Thanks !

[elpollodiablo]

I've been looking everywhere for a selection of non race 225 40 17's but haven't had much luck. Seems like 45 is the only common size made in the 225 17's

[cmcveay]

Beau - what size are the Kumho's that you grabbed from here? Were they 40's or 45's?

 

I ran 17" 225's on a lowered R56 with a set of Rota Torque wheels and no spacers (I was worried about the issue that Haemish pointed out). The only place I had a problem with contact was where the mud flaps attached. When I wore those out, I went with a set of Dunlop Star Specs and they were even wider but I also changed struts/springs to raise the car back up about .25" and I didn't have any problems with contact except at low speed when I turned the steering wheel all the way to the locks. I still have two of those Kumho's (Beau took the other two) so if you'd like to mount them on rims and give 'em a try, just let me know.

[GotMINI]

Mine is not lowered and I have ordered a set of Kyoma Evolve series 628 17x7's to mount them on. All are being sent to my installer so, when they come in I will have them mount just one. See what we're looking at.

 

It makes me a little more confident that you ran them on your car and only had some rub at the lock with a lowered set up.

 

Worse case senario is that I will just have to pay for shipping back and Tire Rack will send another set of tires. I appreciate all of your input. I will let you know how everything comes out sometime next week when I go to mount.

 

Thanks !!

[cmcveay]

If it'll help you feel better, the rubbing at the locks was only with the Star Specs. If you take a look at the dimensions provided by the manufacturers on Tire Racks website, you'll see that the Star Specs are a bit wider at the tread and sidewall than other tires of the same size.

 

Oh, I shold also mention that all of those tires were mounted on 17.7's but I don't remember the off-set on the wheels. If you give Dan a call or google the Rota wheels, you can find out what their offset is just to compare. I'm not a fan of using the wheel spacers if it's not needed though. My .02 on that is you are putting the load a little farther out on the axle/spindle/bearing so it increases the load on the bearings. Also, the spacer requires longer bolts so the leverage applied when starting/stopping is increased. The only reason to use spacers is to clear the brakes so I just shopped around until I found wheels that cleared the Wilwood brake kit and I didn't have to use spacers. In the case of Haemish, that wasn't an option because he has a set of wheels that he wants to use and spacers were the only way to clear the brakes.

 

The tire size calculator that Haemish (Edge) mentioned really is an awesome tool to use. When I was trying to figure out what size tire I wanted to run, I first selected the brand and models that I was going to choose from and I then put all of the dimensions (including the OEM tire/dimensions) into an excel spreadsheet. Then, I ran them through the Miata calculator so I could get the changes that would happen and with that data, I was able to sort through the choices with very little confusion. Using the OEM as my baseline, I could easily see which tires would be the closest fit to OEM and my ultimate goal was to keep the tire "height" as close as possible while getting a wider tire under the car and my other big concern was weight. A tire that's too tall will hurt the acceleration of the car as it effectively increases the final drive ratio and a heavier tire takes more energy to start/keep rolling and with more unsprung weight, they change the handling/ride dynamics. The impact upon the speedo and other data displays had no impact on my decision because I can check the indicated vs. actual with mile markers or a GPS and it's really not that hard to remember that if the speedo says I'm doing 65 mph, I know it's off by 4 so I'm actually doing 61 mph. I've also heard the argument that if you get a speeding ticket and you have the calibration/accuracy of your speedo checked and it's off, the ticket will probably be thrown out. Your mileage may vary on that tactic but I've had people tell me that story.

[elpollodiablo]

Those were 235 40's not 225 40's, since the sidewall is a percentage height of the tread width, the 235 would be a little bit taller than the 225 which causes further issues since the inside of the wheel well is rounded

 

Also the 2nd generation minis have a bit more room in the wheel wells than the first gen's.

 

The numbers on the side of the wheel are width in mm, height of the sidewall as a percentage of the width and rim size . . .

Soo for a 215 45 17

The tread would be 215mm wide (or 8.46")

The sidewall would be 96.75mm high (215mm x .45 = 96.75mm or 3.8")

and the rim size would be 17 inches

 

Add all that together and you have a tire that's 8.46" wide and 24.6" tall (don't know how to calculate the contact patch since that math's a bit more scary since you have to figure in tire pressure, sidewall flex, weight sitting on that particular axle and so on

 

Not sure why they combined metric and english units but that's what they did.

Edited June 16, 2012 by elpollodiablo

[cmcveay]

That's why I go to Tire Rack and get their numbers - your math example gives me a headache....

[elpollodiablo]

Sometimes the maths give me a headache too

 

That's why I go to Tire Rack and get their numbers - your math example gives me a headache....

[S Whitey]

I have 18x8 Motegi's and I'm running 225/40ZR18 Kumhos on them. It fills the wheel arches nicely and gives it a seriously boss like look. The stance is amazing and the extra tire keeps the car glued to the road. Oh, and did I mention my mini is lowered!

[GotMINI]

Well finally the verdict is in regarding my quest to install 225/45/17's on Otis. I finally got my new wheels in and my Tires had been delivered to my installer (Goss' Garage in Seabrook) (Pat Goss, one of the hosts of Motorweek) I had a Thursday appointment for the install, but everything was in on Tuesday, I went over and Pat Goss had his best tire and Alignment guy check out fitment. Well to my delight we decided to mount only one tire, we checked the rear because that was where we were going to have issues if we were to have any at all. This way if they were too big I could order another size and all would be good for my Thursday time frame. I got the all clear. I was so happy !!

 

So I go in Thursday afternoon, rears went on perfectly, the fronts another story ! I have ASA AR1's with my all seasons on them, they have a 42mm offset that clears my JCW Big brakes no problem. The new wheels I ordered are Kyowa Evolve 628 series with a 42mm offset. What could go wrong I say, all the same measurements. Well I just found out that all wheels are not cut the same as far as the back side of the spokes ! My ASA AR1's are more concave and produce more clearance. I had to order some spacers and wait until today to finish the job.

 

Be carefull out there when ordering your wheels, an offset does not guarantee the clearance you may need. Design plays a huge role.

 

Thanks to all with your great input. That's all of the fun, figuring out what works and being able to share so the next person may benefit. So in conclusion, 225/45/17's will work with a stock suspension.

 

 

 

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[Bert]

Great job. Can't wait to check it out in person.