Author Topic: Tire / Wheel combo Diameter  (Read 294 times)

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Offline s3racing

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Tire / Wheel combo Diameter
« on: April 24, 2018, 01:01:47 PM »
Probably a Nube?

I’m running Factory Boxster Tiresizes on my car205/50zr17 front and 255/40zr17 rear

Having rubbing issues and a very bad turn radius to try remedy that I was thinking of going down an aspect ratio to 205/45zr17 or 205/40zr17up front and leave the tires on the rear as they are. But then they will have a staggered diameter. Will that cause me a lot of handelling issues I again an 1” to 1.5” in hight clearance Beter said half `that which could make quite a difference for me.

Just worried about brake and handelling issues

Anyone a
Have any real world experience with running staggered tire sizes in regards to overall diameter differences?
« Last Edit: April 24, 2018, 01:12:27 PM by s3racing »

Offline Bruce

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Re: Tire / Wheel combo Diameter
« Reply #1 on: April 30, 2018, 05:33:43 PM »
How wide are the wheels?

Reducing the tire size like you suggest won't hurt handling much.  You will still have a lot more rubber on the ground than most other Beetles. You will have so much tread contact area that it will take a lot to lose traction.
 Many don't know that when you reduce the aspect ratio only, the actual tread contact width increases.  A 205/40 will have a wider tread contact than a 205/60.  On the other hand, a 205/40 will have a shorter tread contact pattern than a 205/60.

Over the years I've had 7 and 8" wide wheels on my car.  I've run 205/50, and 205/55 on the front, and 225/50, and 215/60 on the rear. In my experience, the rubber compound was the biggest factor determining grip, not the size.

What brakes?

Offline s3racing

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Re: Tire / Wheel combo Diameter
« Reply #2 on: May 01, 2018, 06:15:55 AM »
7” x 17”Boxster wheelsfront and 8.5” rear

2001 Boxster front and rear calipers and discs on 944 hubs and e-brake set up.

Was just worried as the fronts will have a considerable diameter difference to the rears if I change.

Guess I might have to play with the brake bias a bit to counter the effects. I have a balance bar on my peddle set up and a bias adjuster to my rear brakes. So can play with those a bit to get the brake balance right.

Offline Brenticon

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Re: Tire / Wheel combo Diameter
« Reply #3 on: May 01, 2018, 08:43:57 AM »
From my understanding, the first numbers are the actual width of three tire in mm.
The second set of numbers are the percentage of the first number, which becomes the height of the site wall.
I'm confused how changing the aspect ratio changes width?

Offline Brenticon

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Re: Tire / Wheel combo Diameter
« Reply #4 on: May 01, 2018, 09:32:52 AM »

Offline s3racing

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Re: Tire / Wheel combo Diameter
« Reply #5 on: May 01, 2018, 09:52:56 AM »
It changes  the diameter not the width really. The width will be slightly affected but more because of  possible streatch because of the wheel width but my question is in regards to possible performance issue caused by the two different overall diameter from front to rear.
With my proposed change the front tires will have more revolutions vs. the rear which I could imagine have an affect on the braking and hadeling performance of the car.

I’m hoping on one or two peoples real world experience with a similar tire diameter combination.

Thanks guys

Offline Bruce

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Re: Tire / Wheel combo Diameter
« Reply #6 on: May 02, 2018, 05:34:53 PM »
I'm confused how changing the aspect ratio changes width?
The 205 refers to the width of the tire measured at it's widest point of the sidewalls.  IOW at the bulge of the sidewalls.  In my post above, I said when you reduce the profile %, the tread width increases.

Here's your side walls: (__)  If you reduce the height, the line at the bottom gets closer to the bulge of the sidewall.  Since the sidewalls are curved outward, the tread contact gets wider.

Who reading this has some 205/70s or 205/65s that they can measure the actual tread width and post it here?

Offline Bruce

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Re: Tire / Wheel combo Diameter
« Reply #7 on: May 02, 2018, 05:43:07 PM »
7” x 17”Boxster wheelsfront
It rubs at full lock on the inside, right?  Can you put a wheel spacer on?

What about getting the wheel narrowed to 6"?  When you remove 1" from the inner side of the wheel, the inner rim moves closer to the wheel centerline.  Your ET reduces by 13mm.  It also moves the tread 13mm away from the inner fender, allowing you to turn tighter.

Do they make a 195/50/17?

 

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