Wheel size mystery....

[zappbranigan]

Another mystery involving a 2001 boxster I bought with no maintenance history.

Among many other issues I've solved/working on thanks to the help from everyone here on Renntech :renntech:

I've got another anomaly. The back wheels are much wider than the front wheels. I don't know anything (yet :)) about wheels or wheel sizes, but there are some numbers imprinted on the wheel around the valve stem hole. I assume it's the wheel size numbers...

The back wheel reads 8.5 and 48

The front wheels read 7 and 55.

The recess for the lugnuts are also quite different as the lugnuts on the front wheel are flush with the holes (almost sticking out). The back lugnuts are pretty recessed and out of sight. I don't care for the difference aesthetically.

Can anybody advise if this is a problem? What's the stock size wheel for a 2001 Boxster (non S)?

[rsfeller]

You are nervous with a new car! I was the same way, but not over thinking this point! Many (most now) preformance cars have different front/back tires.

It's be design. Do some research on google and this site, all the answers are there. Your manual (assuming you have one) has the specs to as well as down loadable manuals you can find here.

Those numberss are the rim width and I'm assuming the 2nd number in each case is the offset, but not sure.

Shawn

[zappbranigan]

Shawn,

I am a little cautious with this car because of ALL the problems that I've had to fix to bring it back to road worthiness. This thing must've been in a flood or something. Rust everywhere on the undercarriage and wheel carrier.

I had some "rubbing" coming from the rear of the vehicle that was identified as wheel bearings. I'm almost done completing that DIY, and the larger wheels got me wondering if that may also be causing the roaring sound I heard. Didn't know if the larger wheels were an improper size for the vehicle.

Thanks again for your input!

[rsfeller]

Shawn,

I am a little cautious with this car because of ALL the problems that I've had to fix to bring it back to road worthiness. This thing must've been in a flood or something. Rust everywhere on the undercarriage and wheel carrier.

I had some "rubbing" coming from the rear of the vehicle that was identified as wheel bearings. I'm almost done completing that DIY, and the larger wheels got me wondering if that may also be causing the roaring sound I heard. Didn't know if the larger wheels were an improper size for the vehicle.

Thanks again for your input!

I totally get your concern. Although I got my car for a great deal I expected to have 101 "unknown" issues to make it a great deal. What was that sound? What was that vibration? Why does item "A" look wrong?...I know your concern for sure.

"roaring" is always 99% wheel bearings. I've done 101 of them on 101 cars and I always try to convince myself that it's something else before I except the fate that it's bearing. Some cars it's really easy and on this car it didn't look to fun, and I have one slightly noisy too!

By "larger" you simply mean different, correct? Or are they after market rims which could be a concern.

Two things all new "used" Porsche owners should do is buy the Bentley and the Durametric software. These two items can put 92.5% of your concerns to rest. Especially if you don't have the factory user manual the Bentley will fill you in on all specs needed. Although this website has a better then average search function not all forums do. You can spend an hour searching a topic to come up empty handed, just to have a bunch of "know it alls" tell you it's in there somewhere!

Give us a photo of your car with rims and we'll tell you if they are OEMs.

Good luck.

[jmatta]

Sounds like you have the stock wheels; just as built. I'd be more concerned about the origin of this car...was this a flood victim from the south?

I'd check into title history and see where it's spent it's life. Salt water can do an enormous amount of damage. I guess you're already "in", so I wish you luck. Hopefully the car will turn out to be OK.

[rsfeller]

Sounds like you have the stock wheels; just as built. I'd be more concerned about the origin of this car...was this a flood victim from the south?

I'd check into title history and see where it's spent it's life. Salt water can do an enormous amount of damage. I guess you're already "in", so I wish you luck. Hopefully the car will turn out to be OK.

There you go, really stress the guy out now!

My vote is no-go on flood damage, you'd have more then your share of electrical concerns the day you got it!

[grover]

The back wheel reads 8.5 and 48

The front wheels read 7 and 55.

Oh my god, don't drive it with tires like that, you'll ruin the transmission!!! oh what the heck were they thinking???

Sorry, couldn't resist ;) Porsche went to exquisite pains to give the Boxster perfect 50/50 weight distribution for incredible performance and handling... and then proceeded to spec out stock wheels and camber to make it plow like a front wheel drive sedan. Makes it safer that way; less likely to fly tail-first over a cliff.

Without getting too deep into the physics of it, wider tires grip better when cornering than narrow tires. So, if you're driving your Boxster really fast around a corner, Porsche designed it so the front wheels (205mm wide/0 camber) will start slipping before the rear (255mm wide/-1.5 degrees camber). This way, if you skid, you skid straight ahead. It's nice and predictable and the anti-lock brakes will help you steer. Whereas if the rear tires lose grip first, the car will want to spin. Which is good for racing, and fun for drifting, but bad for lawyers, I suppose.

Have you bought the Bentley manual yet? If so, turn to page 44-1 :) If not, WHY NOT??

Narrow tires also resist hydroplaning better, so they're safer in the rain as well. Oh, and be mindful of the offsets; you need to use different spacers if you change wheel sizes (for instance, if you use the spare tire) to keep the tire from rubbing in the wheel well during suspension travel. It's all in your owners manual and the Bentley manual.

Edited March 25, 2009 by grover

[pk2]

Your wheels sound kind of narrow but shouldn't cause a problem. It's easy enough to find out though, look at the tire on the inside and outside and see if it has rub marks on the upper sides. If your not sure, take it off and look for polished spots on the inside of the fender lip or on the strut tower.

Regards, PK

[ericinboca]

Another mystery involving a 2001 boxster I bought with no maintenance history.

Among many other issues I've solved/working on thanks to the help from everyone here on Renntech :renntech:

I've got another anomaly. The back wheels are much wider than the front wheels. I don't know anything (yet :)) about wheels or wheel sizes, but there are some numbers imprinted on the wheel around the valve stem hole. I assume it's the wheel size numbers...

The back wheel reads 8.5 and 48

The front wheels read 7 and 55.

The recess for the lugnuts are also quite different as the lugnuts on the front wheel are flush with the holes (almost sticking out). The back lugnuts are pretty recessed and out of sight. I don't care for the difference aesthetically.

Can anybody advise if this is a problem? What's the stock size wheel for a 2001 Boxster (non S)?

These are 17 inch? If so, my PET shows for the '01 these sizes as stock.

[zappbranigan]

'preciate everyone's input. Since owning this car, and discovering all the hidden problems not mentioned by the dealer, I suspect everything wrong with car is a product of ductaping or a paint-over. This forum has been an unbelievable help for people like me with these nagging issues and a limit on my bank account. So thanks again to everyone!!!

Grover: I keep putting off buying the durametric software and manual cuz I'm always thinking the money needs to go to the next project. After being embarrased again by not having it and being told I need it...I'm going to make it my next "project". Thanks for calling me out on that one.

PK2: No signs of rub marks or polished spots...thank God. First time I think I haven't discovered a new problem while fixing an old one.

To put the issue to rest, I'm going to do the history search and see what comes up. Based on everyone's ideas, I think the tires are there by design, and they are stock.

[jmatta]

"This thing must've been in a flood or something. Rust everywhere on the undercarriage and wheel carrier"

Sorry, but I didn't bring up the topic...buyer beware.

[pk2]

In lieu of a Bentley manual, just to be able to feel your way around, a guy on Ebay used sell on the factory manual on a CD for $5. I've also seen it out there on the net.

It's completely illogical in its layout and a real pain to find stuff in it but it's all there for the most part.

Regards, PK

[whall]

With regard to the wheel size, jmatta is correct. From owner's manual:

.................Tires ......................Rim.................Rim Offset

front.......205/50 ZR 17.............7 J x 17 H2.....................55 mm

rear........255/40 ZR 17..........8.5 J x 17 H2.....................48 mm

Bill

Edited March 26, 2009 by whall

[jmatta]

Thanks for laying that out, Bill...sometimes my answers are short and to the point. I guess when I purchase a car, I read or investigate what I'm getting and getting into.

This certainly isn't a knock on our original poster; these forums are a wealth of information and I enjoy reading all the comments and collective knowledge.

Edited March 26, 2009 by jmatta

[geoff]

...

I am a little cautious with this car because of ALL the problems that I've had to fix to bring it back to road worthiness. This thing must've been in a flood or something. Rust everywhere on the undercarriage and wheel carrier.

...

Porsche uses cosmoline, which is a yellow/brown coating, on the undercarriage and many other parts to prevent rust. See Wikipedia for a brief description. Lots of aluminum parts on the undercarriage, which doesn't rust like steel. If for some reason you do have rust, I think Porsche's new car warranty covering rust is a lot better than their drivetrain warranty. You might want to have someone knowledgeable look at your car to determine if it really is rust, as well as address a lot of your other concerns. Try your local PCA group.

You can look at places like tirerack.com or tires.com to see what the original and optional wheel and tire sizes are

If you bought the car with any kind of warranty, you might want to take it to a trusted independent shop and get a PPI (pre-purchase inspection) with written report, then take the report to the seller to get items fixed. You don't have to tell the shop you already bought the car