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Lesson teaching about tires, Was: Ouch$$$ Lesson learned

Subject: Lesson teaching about tires, Was: Ouch$$$ Lesson learned
From: raveracer77 at yahoo.ca (raveracer77)
Date: Thu Nov 23 16:28:07 2006
References: <003201c70e84$e50e4ca0$6401a8c0@sharpshooter><00d001c70eb9$2e755ad0$0200a8c0@usafi88fmqcm6g><005201c70eba$03154520$6401a8c0@sharpshooter><011101c70ec5$528d3300$0200a8c0@usafi88fmqcm6g><004201c70f39$e6024750$6401a8c0@sharpshooter> <007901c70f4b$83e4c400$0200a8c0@usafi88fmqcm6g>

Nice, the List changes the font so the drawing came out all sorts of wrong. Either way I forgot to finish the point that once you've measured the rim width and divided it by 2 (halfway mark) you then subtract that from the backspace measurement and you have your offset.

Rave Racer
Currently:
NEW!! 91 Jetta GLI 2.0L 16V
'81 Scirocco Mk1 1.8L 8V Digifant 2

'89 Jetta GTX 1.8L 16V
'87 Audi 4000 Quattro
http://www.audifans.com/registry/view.php?action=viewCar&carid=110
'72 Triumph GT6
http://www.triumphowners.com/uploaded/34/50-50-111014_20raveracer-gt6-1.jpg

http://spaces.msn.com/raveracer77/photos/
http://www.myspace.com/rave_racer
___________________________________________

----- Original Message -----
From: raveracer77
To: scirocco-l@scirocco.org ; David Brown
Sent: Thursday, November 23, 2006 03:05 PM
Subject: now: Lesson teaching about tires, Was: Ouch$$$ Lesson learned

I'm going to forward this back to the list because it's probably some good information and if I'm wrong about anything (that's rare) someone should be able to correct it. I say it's better to be corrected then to pretend to be right. So here's that compomotive link again and a rather long explanation:

http://www.usacomp.com/terms.htm

I'm not sure what the factory offsets are and it's possible that it's different for each style. I think that my bottle caps are +40 (40 mm) but I haven't measured so I can't say. I know they're possitive offset but I just don't know how much. Probably between +30 and +45. The easiest way to measure the offset is to lay the rim on it's face, carefully on something soft of course, then lay something long across the top like a ruler, yard stick, meter stick or whatever. Then you can measure from the hub to the measuring stick and that will give you the T Dimension as it's called on the Compomotive site or in common talk "Back space". If you've measured the overall rim width which is from the inside of each inner lip I know that mine are 5.5 inches, don't know what that is in millimeters but consider that your tread width is 195 mm. The ones on my GLI are 7. A more negative offset would reduce your backspace for a similar width rim pushing it out of your fender more for a wider stance. Most people will get a wider rim then increase the offset to keep the wheel closer in which I hate but really it's about personal taste. If I'm getting a wider wheel I'm going to use that extra rubber to effectively widen my stance so I'm looking for less or the same amount of backspace so that the extra width pushes out but that's just me. That would mean more negative offset or at least a less positive one. An easy rule to remember is "More positive offset means more backspace". If you can remember that more backspace puts the rubber under the car, and by under I mean inside the outer limits of the body. From there if you can do the math then you'll be able to figure out the rest of the rim.

Here's where it gets real confusing. For example If I have four sets of rims and two sets are 5 inches wide and the other two are 7 inches wide. One set of 5's are a +40 offset and the others are a +10 offset the +10's are going to stick out more because the +40 means that the hub face is closer to the outer lip of the wheel from the verticle center of the rim so the whole rim is more under the fender. Now those 7 inch wide wheels are the same a +40 and a +10. Comparatively the +40 in the 7 will stick out farther then the +40 of the 5 and the +10 of the 7 will stick out further then the +10 of the 5, BUT the +40 of the 7 probably won't stick out as far as the +10 in the 5 because the hub on the +10x5 pushes the rim out further. I wish I was good with a drawing program because I could make comparative pictures.

I tried but it might be more confusing. The verticle line on top represents the imaginary center line on the rim and then the verticle lines in the center are the hub face. As you can see the 5x+10 have less distance between the imaginary centerline and the hubface but they still stick out further (more Front space) even though they're narrower overall.

not to scale, obviously:
5x+40 5x+10 7x+40

____|____ ____|____ _____|_____
| |-| |---|<----------Offset
| | |
| | |------------| <--Backspace
| | |
| | |
_________ ________ __________

I remember when I first started trying to figure this out I thought to myself "How could wheels be so damn confusing?" Hope this helps. Oh and by the way, truck tires are sometimes measured on a completely different system. I can't be bothered to learn it so anytime people start talking to me about them I just flip them off then they leave me alone. It pays to be ignernt about some things.

Rave Racer
Currently:
NEW!! 91 Jetta GLI 2.0L 16V
'81 Scirocco Mk1 1.8L 8V Digifant 2

http://spaces.msn.com/raveracer77/photos/
http://www.myspace.com/rave_racer
___________________________________________

----- Original Message -----
From: David Brown
To: raveracer77
Sent: Thursday, November 23, 2006 12:59 PM
Subject: Re: Ouch! $$$ Lesson learned about tires.

No it's not offensive in fact very informative. I just got my 1st egumacated info on the tirerack.com site. Yours looks more informative.
If I would have read the scirocco.org threads a few months back when Cathy was talking about this I might have learned something then also. So it's my own fault for being ignert. 8-)
I don't know what the offset is for the aftermarket rims, but I will measure them when I take them off. How do I measure them? take the overall rim width/2. Then measure to where they meet the hub and subtract?

BTW what is the stock offset on factory rims? Am I understanding this right also or am I ass backward. The more positive offset the more the rims will push the tires out toward the fenders and the more neg the more it would pull them in around the inner fender covers and narrower?

I was looking at a set on tirerack that has a +35mm. What are factory rims.

Thanks for helping me catch up to an already posted thread that I should have read. 8-)
----- Original Message -----
From: raveracer77
To: David Brown ; scirocco scirocco
Sent: Thursday, November 23, 2006 1:05 AM
Subject: Re: Ouch! $$$ Lesson learned about tires.

I'm not trying to be rude so please don't take offense to this if you already know how offsets work but here's a link that explains it fairly well:

http://www.usacomp.com/terms.htm

Do you already know what offset you have on what I'm assuming to be aftermarket rims? Have you checked the spacing while you're sitting still... like if the outer sidewall touches the fender I'm assuming if you turn the wheels to the right it's on the upper front outer sidewall on your right side, does the rear of the tire have a lot of clearance at the back on the inner fender well? Does the front of the left tire touch the inner fender at the same time? If so then I don't know what to do other then try to pick up different rims. The nice thing about this compomotive site is that on the main page there's a section I think Modular rims where you can custom request exact measurements. Kind of cool because they just keep inners and outers in a bunch of sizes and the face and then bolt them together to order depending on how wide you want the tire, how deep the face and how much offset. Wish I could afford that kind of nonsense. One of the faces even looks like 80's Audi Stock fuchs.

Rave Racer
Currently:
NEW!! 91 Jetta GLI 2.0L 16V
'81 Scirocco Mk1 1.8L 8V Digifant 2

http://spaces.msn.com/raveracer77/photos/
http://www.myspace.com/rave_racer
___________________________________________

----- Original Message -----
From: David Brown
To: scirocco scirocco
Sent: Wednesday, November 22, 2006 09:44 PM
Subject: Re: Ouch! $$$ Lesson learned about tires.

There rubbing pretty bad. I'd say if I used them much with any type of hard cornering I'd tear a hole in them or pull body parts off. 8-)

I'm thinking since I had 195/60/14's on it with stock rims that maybe the 195/60/14's in the non stock rims are under offset. They do fill up the wheel wells so I really don't know. Whatever it is it's not really drivable right now.
----- Original Message -----
From: raveracer77
To: David Brown ; scirocco scirocco
Sent: Wednesday, November 22, 2006 11:27 PM
Subject: Re: Ouch! $$$ Lesson learned about tires.

Are they rubbing badly? Edgeracing.com has a great system for looking up tires by size only and then it shows you all the ones they have available in that size. I had 195/45/14 on stock bottle caps on my Rocco for track days. Real low profile and quick, but it would be screaming in top gear at speed because it effectively lowers the final drive ratio. Toyo T1R seems to be the only tire that gets made in almost any size. My street tires for after the track were some stock Saturn tires that were really narrow but very tall, taller then stock and they never rubbed. Not great grip but I was going in a specific direction with her before I melted the fuse panel. Now I'm going in a slightly different direction..... uh, standing still actually till I finish the 16V swap.

Rave Racer
Currently:
NEW!! 91 Jetta GLI 2.0L 16V
'81 Scirocco Mk1 1.8L 8V Digifant 2

http://spaces.msn.com/raveracer77/photos/
http://www.myspace.com/rave_racer
___________________________________________

----- Original Message -----
From: David Brown
To: scirocco scirocco
Sent: Wednesday, November 22, 2006 03:23 PM
Subject: Ouch! $$$ Lesson learned about tires.

Well I thought I was pretty slick. I got some rims last year at Cincy. I ordered some H rated 195/60/14's from the tire rack. Both for a good price. Then had them mounted and balanced. All ready to go and.....they rub. The previous tires were 185/60/14's. I had already switched them out for a set of T rated 4 season tires in 195/60/14 so I figured they'd fit just fine. Well wrong. I forgot that the suspension on this scirocco had been lowered. They rub on turning and bouncing.

I figured all 195/60/14's should be the same, but evidently they are some differences. Looks like my Jetta got a new set of summer performance tires and I've got to go tire shopping again. 8-( Even if there the same measurements looks like some have different tread width.

Lessons learned.

Later
David
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References:
- Ouch! $$$ Lesson learned about tires.
  - From: sharpshooter33 at adelphia.net (David Brown)
- Ouch! $$$ Lesson learned about tires.
  - From: raveracer77 at yahoo.ca (raveracer77)
- Ouch! $$$ Lesson learned about tires.
  - From: sharpshooter33 at adelphia.net (David Brown)
- Ouch! $$$ Lesson learned about tires.
  - From: raveracer77 at yahoo.ca (raveracer77)
- now: Lesson teaching about tires, Was: Ouch$$$ Lesson learned
  - From: raveracer77 at yahoo.ca (raveracer77)

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