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Discussion Starter · #1 ·
Getting on the highway today on my way to work. I blasted something in the road. At the time I thought I just clipped it no big deal, but upon inspection at lunch I found two hugh marks in my wheels and the sidewall on my tire was split wide open. Somehow though the tire was still holding air and better yet I hit the highway back home and still made it without the tire blowing to pieces. The only good news was that the tire is completely covered under the road hazard so I get a brand new Sumitomo 18" HTR Z II, but the wheels insurance won't cove because they are aftermarket. They are still driveable, but cosmetically they look like crap now.
 

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Good thing you didn't have a blowout. Front or back wheels?
 

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Discussion Starter · #6 ·
New tire will be here by Monday. I just threw the stock wheels back on winter will be here soon anyway I needed to change back just wasn't planning on doing it yet.
 

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x2. Sounds like you should pimp the donut until you get a new tire.
NEVER PUT A DONUT ON THE DRIVEAXLE. If you have a full-size spare tire, that's fine. If you have an emergency, do what you have to do. But if you have the time to do the job right, never put a small-size spare on the driveaxle because it will cause the differential to spin constantly. Instead, pull the full-size wheel off a non-driveaxle (if you have one) and put the donut in its place. You want to wear the diff out? Go ahead use the donut on a drive wheel, but you've been warned.
 

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Aren't VW donuts the same running diameter as the stock tire?
I only ask because: My V6 4Motion had a full sized spare, but my W8 has a donut - I thing do to the fact that I have a larger fuel tank (21.1 US gallons)?
 

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NEVER PUT A DONUT ON THE DRIVEAXLE. If you have a full-size spare tire, that's fine. If you have an emergency, do what you have to do. But if you have the time to do the job right, never put a small-size spare on the driveaxle because it will cause the differential to spin constantly. Instead, pull the full-size wheel off a non-driveaxle (if you have one) and put the donut in its place. You want to wear the diff out? Go ahead use the donut on a drive wheel, but you've been warned.
Man, you learn something every day in this place.
 

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Aren't VW donuts the same running diameter as the stock tire?
I only ask because: My V6 4Motion had a full sized spare, but my W8 has a donut - I thing do to the fact that I have a larger fuel tank (21.1 US gallons)?
The OP was running 18" Sumitomos, I doubt he has a donut that size. But I see your point, if the tire diameters are the same on both sides of the front, what's the issue?
 

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NEVER PUT A DONUT ON THE DRIVEAXLE. If you have a full-size spare tire, that's fine. If you have an emergency, do what you have to do. But if you have the time to do the job right, never put a small-size spare on the driveaxle because it will cause the differential to spin constantly. Instead, pull the full-size wheel off a non-driveaxle (if you have one) and put the donut in its place. You want to wear the diff out? Go ahead use the donut on a drive wheel, but you've been warned.
there is NO issue if the diameter is the same. if the donut is a different diameter than the normal tire/wheel, then limit the amount of miles you have to drive on the donut IAW your owner's manual.
sheesh, deus, I don't know what we're going to do with you. :poke:
 

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there is NO issue if the diameter is the same. if the donut is a different diameter than the normal tire/wheel, then limit the amount of miles you have to drive on the donut IAW your owner's manual.
sheesh, deus, I don't know what we're going to do with you. :poke:
Why don't you try reading my post, smartass. You just repeated what I said, and then scolded me for saying it.
 

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IIRC, FWD 1.8T and V6 passats come with a full-size spare. I don't know about the 4MO or W8's, however.

Even if you upgrade to larger rims, the *rolling radius* of the stock 195/65-15's and the aftermarket 225/40-18's (or whatever) are supposed to be the same (tirerack recommends staying within +/- 3% of the original rolling radius)

I doubt you're gonna damage the differential by driving for a few days on a full size spare that is less than 3% larger or smaller. Deus -- Is there any data that shows differential damage is possible?

...Somehow though the tire was still holding air and better yet I hit the highway back home and still made it without the tire blowing to pieces...
mtbwagon -- I'm more concerned that, even after seeing the damage, you still chose to drive at all on the tire with the damaged sidewall. That tire was "hanging by a thread" & you're lucky it didn't blow out on you.
 

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Glad you made it home safely. If you've got a gash in the sidewall I wouldn't chance it like that on the highway, good way to get into an accident.
 

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IIRC, FWD 1.8T and V6 passats come with a full-size spare. I don't know about the 4MO or W8's, however.

Even if you upgrade to larger rims, the *rolling radius* of the stock 195/65-15's and the aftermarket 225/40-18's (or whatever) are supposed to be the same (tirerack recommends staying within +/- 3% of the original rolling radius)

I doubt you're gonna damage the differential by driving for a few days on a full size spare that is less than 3% larger or smaller. Deus -- Is there any data that shows differential damage is possible?


mtbwagon -- I'm more concerned that, even after seeing the damage, you still chose to drive at all on the tire with the damaged sidewall. That tire was "hanging by a thread" & you're lucky it didn't blow out on you.
First of all, a donut is not full-size. A donut is a small, nylon-belted tire that is used only because it saves weight and is easier to dig out of the trunk. A full-size spare is called a full-size spare.

My 1.8t has a full-size spare. I have to think that VW is smart enough to include a full-size spare with their 4-Motion cars for exactly the reason I stated above.

No, Pete, I don't have data to support my claim. I'm left to flounder about with only the laws of physics and mathematics to support me.

If you take two wheels, one larger and one smaller, and roll them the same distance, the smaller wheel will rotate more times. When you connect those two wheels to an axle with a differential in the middle, the differential gears have to spin to compensate for the difference in rotational speed between the two wheels.

Now, if you take that assembly and attach its differential to a 170-horsepower engine, you get a hell of a lot of pressure on the gear teeth. Normally the differential oil can prevent bad things from happening to the teeth under the kind of torque that it takes to accelerate a 3500-pound car, but when you add in the extra heat caused by the constant rubbing of 5 sets of gear teeth (instead of one set, as is the norm when accelerating in a straight line), the differential oil thins out and offers those teeth less protection from the friction they are experiencing.

This will happen if you run a donut spare on a driveaxle. Now, if you have a full-size spare, there's no issue. The only reason I brought it up was because someone said something about "pimping the donut for a few days".
 

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I have to admit I've not seen any reduced size donuts though. Typically it's called a donut because the wheel is oversize (meaning the tire has a narrow sidewall) and the tire is very skinny.




Donut replaced by full size spare.
 

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All B5s, B5.5s, and MkIVs have full-size spares. They are the exact wheel that would be on a car equipped with steelies and caps from the factory.

For wheel repair, contact ReStock Wheels in Ferndale, MI. The only Bentley-approved wheel repair facility in the US. I use them, they are fantastic and you get your own wheel back, unlike most places which core out.
 

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I have to admit I've not seen any reduced size donuts though. Typically it's called a donut because the wheel is oversize (meaning the tire has a narrow sidewall) and the tire is very skinny.
I, on the other hand, have never seen a full-size temporary spare. That said, I'm not going to argue over whether they exist, because that has nothing to do with my personal opinion. It would be a good idea, though, for people to avoid using words that aren't universally-understood; if there are a lot of people who think a "donut" is any kind of temporary spare, not just the reduced-size kind, then we should avoid using the word "donut" to avoid confusion.
 
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