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Winter Tires / Wheels w/Spacers ?


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'04 996 C2 - normal summer tires are 18" Light OEM. Purchased Blizaks for all 4 and purchased new rims (inexpensive & just for winter) that are 18x8.5 &18x10. Seller mandated 12MM spacer for rear and 5MM for front. He says w/o rear spacer tire will hit strut when tires heat up (currently there is no spacer on rear and vehicle seems to drive OK with the new rims) & I know I need spacers in front as w/o them the wheel hits the caliper. Question is will these spacer sizes have any adverse effect on handling?

Are they two large? New used spacers before!

Thx for replies.

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You need to check the offset (ET Value) stamped on the wheel. My 2003 996 C2 is ET50 front and ET 65 back. So the wheel offset with the spacer must come to the right value.

ET values are given in the handbook.

8.5 is not a stated rim width for winter tyres. It's either 8 or 7.5

H

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Wheels are ET58 rear, and ET 52 front & 10" and 8.5 respectively, just had the wheels rebalanced using a lug centric balancing tool.

Getting significant vibration at 65 mph. Saturday I will install the 5mm spacer in front and the 12mm in rear and see if issue resolves.

Only other possibility is bad wheel, spacer, or tires for cause. Porsche dealer sold me the blizak after checking wi/tech support rear tires and I purchased the fronts from Tirerack. Wheels tires & spacer all new.

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I am not sure why you want spacers. Putting on a 12mm rear spacer with an ET 58 wheel will push the wheel centre line outwards to an ET of 46mm against a handbook recommendation of 65mm. As a result the edge of your rear wheel rim will be 19mm further out than it should be. Similarly as you have 8.5's on the front, which are 12.5mm overall wider than recommended the combination of this wheel with a 5mm spacer will push the wheel edge out 11mm (6.25 + 5) further out than recommended.

An ET of about 46 will push the bead on a 265 tyre outwards beyond the wheel arch on a 996 C2.

The ET is the distance inwards from the mounting face of the wheel to its centre line. Spacers decrease the ET value.

Just in case I am wrong you need to check the handbook.

H

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Frankly I would prefer no spacers but the front wheels strike the calipers w/o a spacer ( should have gone with second hand OEM wheels for winter).

USA Rims where I purchased the wheels says I need a spacer in the rear to avoid striking the strut, although I am running it presently without a spacer and no problems noted. I don't drive the car hard or past 70mph, just want to get rid of the front vibration at 60-70 mph.

I should mention the tires are: 225x40r 18, and 265x35 18. As recommended by porsche & tire rack.

Edited by Wausau 911
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Hi Wausau,

Someone sold you wheels with the wrong offsets. You are shaking because your wheels are way out of balance ( assuming you do not have a bent rim). The problem with spacers is the wheel is centered on the hub by the three flanges that stick out past the brake disc. This is critical. You put the spacers on and you have less flange to grab the wheel center. 5 mm you can get away with but you will notice that you have to hold the wheel tight to the brake disc when you put your lug nuts on or the wheel falls off and dings your brake caliper. THE WHEELS ARE NOT CENTERED BY THE LUG BOLTS. Balancing the wheels by the bolt holes is a big mistake. You balance the wheel off it's center hole which is what the car indexes. A 12 mm spacer is a big mistake. do not use it. Use the wheels as they are. It is only a cosmetic issue if that. Use the 5mm spacer in front.

Next find someone who knows how to balance wheels which is not easy. Don't worry about the balancer used. Worry about the tech.

If the tech does not warm up the tires before he puts the car on the lift, run away. High performance tires flat spot in as little as 15 minutes depending on temperature. This can throw the balance off by as much as 1/2 oz.

If the tech uses the balancer in round off mode, run away. Porsche wheels have to be balanced to < 0.1 oz. You can't do this with a balancer that is reporting in 0.25 oz intervals. Out of round off mode the balancer will report in hundredths of an ounce. Such as 0.78 or 0.07

Tape weights come scored in 0.25 oz segments. If all you see used are whole 0.25 oz segments, run away. Although occasionally you will land on a whole segment in most cases you will have to use a fraction of a segment to get the balance right.

If the tech adheres to these three rules you are probably OK.

If the balance is good your steering wheel won't shake anywhere assuming your wheels are true and your tires are OK. If not the steering wheel will start dancing somewhere around 75 mph.

Edited by Mijostyn
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Your insight is appreciated. Going forward here's what I will do. Use no spacer in rear, and the 5mm spacer in the front as w/o it the wheel strikes the caliper. I will use Standard lug size for the front as I have been told by two people this is sufficient for the 5mm and acceptable. Myjostyn do you see an problem with this setup?

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You need the longer lug bolts for the front. Remember, the bolts now have to go through the wheel, the spacer, and the brake disc to get to their threaded holes in the hub. The shorter bolts will not have enough purchase. I would not like to see you going down the road without a front wheel. Otherwise you should be fine. I would like to have seen you with an 8" wheel in front. 8.5 is a tad wide for a 225. This might make the ride a bit harsher up front as you give up some of your side wall flexibility. But, if you think the car feels good than it is not an issue.

Now get those wheels balanced!

By the way, the guy that sold you the wheels is a jerk. He told you to put a spacer on a wheel with less offset than the factory wheel. If he sold you the spacer I would shove it down his throat. Screw the refund.

Offset is the distance of the wheel's mounting surface from the center line of the wheel. Positive offset is towards the wheels outside. Negative towards the wheels inside. Most wheels like all our Porsche wheels have positive offset. Positive offset pulls the wheel into the car. The less positive offset the more the wheel sticks out. A spacer effectively gives you less positive offset. Instead of spacers it is much better to just get wheels with 5 mm less offset. You actually did just that with your rear wheels!

Nothing like fast cars and fast women.post-89070-0-31419100-1382669829_thumb.j

Edited by Mijostyn
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No problem.

Not far behind the hub is the cap that covers the wheel bearing. If the bolt is too long it will scrape against this. Measure the shank (threaded portion) of the bolt. The right size is 35 mm. 2 or 3 more mm should not be a problem. If they are too long they can always be carefully ground down to fit.

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