Jump to content
Ultimate Subaru Message Board

Official 6-Lug Re-drill Thread: Now in the USRM!


Recommended Posts

close, your on the right track. for example an 175R/75/15. the tire is 175mm wide, the side wall is 75% of that, and it is radial tire on a 15" wheel.

 

 

correct, and a 175R/70/15 would be the same width, but only 70% for the sidewall height, making it a slightly smaller tire, even tho it will still fit on the same rim.

 

the contact patch is determined by the first number - the width of the tire (and proper tire inflation) - the side wall height really has very little to do with it. a taller sidewall may "look" wider (balloon out more, depending on wheel width), but it doesnt really affect the contact patch all that much.

Link to comment
Share on other sites

Here's my 87 with b2300 mazda wheels. One with the wheel fully stuffed - mounted everything but the spring & jacked up until it lifted both wheels.

4" SJR lift, 27x8.50x14s

 

OOPS! No pics!

Edited by czny
spelling
Link to comment
Share on other sites

correct, and a 175R/70/15 would be the same width, but only 70% for the sidewall height, making it a slightly smaller tire, even tho it will still fit on the same rim.

 

the contact patch is determined by the first number - the width of the tire (and proper tire inflation) - the side wall height really has very little to do with it. a taller sidewall may "look" wider (balloon out more, depending on wheel width), but it doesnt really affect the contact patch all that much.

 

 

That's what I'm getting at, even if the tread width on the tire is marked identically, the tire with the shorter sidewall will be marginally wider.

 

MARGINALLY, but still a measurable difference. I do not know if this is true for ALL tires, but all that I have measured, it has held true for.

Link to comment
Share on other sites

That's what I'm getting at, even if the tread width on the tire is marked identically, the tire with the shorter sidewall will be marginally wider.

 

MARGINALLY, but still a measurable difference. I do not know if this is true for ALL tires, but all that I have measured, it has held true for.

 

you might be dealing with over inflated tires. because if they are both 235/75/15 and 235/70/15 they should both be 235mm wide, but different brands might be off a bit.

Link to comment
Share on other sites

That's what I'm getting at, even if the tread width on the tire is marked identically, the tire with the shorter sidewall will be marginally wider.

 

MARGINALLY, but still a measurable difference. I do not know if this is true for ALL tires, but all that I have measured, it has held true for.

 

Tires do not mark the tread width. They mark the section width. The tread width is almost always narrower than the section width.

 

tireDiagram.gif

 

The section width of a tire will vary based on inflation pressure, but more significantly, will vary based on the rim width. The section width as marked on the tire is based on the tire being mounted on a specific width of wheel. If you mount the tire on a wheel of a different width than what the manufacturer used, then your actual tire width (what you measure) will be different than the width marked on the side of the tire.

 

It is also true when comparing tires of different sizes, styles, or manufacturers, that the manufacturer(s) may have used different width wheels when marking them. There are standardized rim widths that the manufacturers use for measuring, but they are standardized per tire size, so the baseline rim might not necessarily be the same if you are comparing different sizes of tires. This means that it is entirely possible for two tires, of the same marked section width, to have different actual widths when mounted on your wheels.

 

//edit: There is some manufacturing tolerance as well. So two tires of the same size from different manufacturers or of different styles won't necessarily measure exactly the same either.

Edited by Red92
Link to comment
Share on other sites

Tires do not mark the tread width. They mark the section width. The tread width is almost always narrower than the section width.

 

tireDiagram.gif

 

The section width of a tire will vary based on inflation pressure, but more significantly, will vary based on the rim width. The section width as marked on the tire is based on the tire being mounted on a specific width of wheel. If you mount the tire on a wheel of a different width than what the manufacturer used, then your actual tire width (what you measure) will be different than the width marked on the side of the tire.

 

It is also true when comparing tires of different sizes, styles, or manufacturers, that the manufacturer(s) may have used different width wheels when marking them. There are standardized rim widths that the manufacturers use for measuring, but they are standardized per tire size, so the baseline rim might not necessarily be the same if you are comparing different sizes of tires. This means that it is entirely possible for two tires, of the same marked section width, to have different actual widths when mounted on your wheels.

 

//edit: There is some manufacturing tolerance as well. So two tires of the same size from different manufacturers or of different styles won't necessarily measure exactly the same either.

 

Awesome information, and I already understood the difference between tread width and section width, but was trying to prevent the muddying of the waters by adding yet another term to the mix.

 

Let me refine my statement even more:

 

Taking the EXACT SAME model, manufacture, section width, rim width and diameter, the tire with the shorter sidewall WILL be slightly wider than the taller version.

Link to comment
Share on other sites

Yeah I think the only solution is to wait a few months and go 5 lug lol

 

why do you say that? it is alot more work, and cost more, and i like the selection of wheels for 6 lug preferably.

Link to comment
Share on other sites

why do you say that? it is alot more work, and cost more, and i like the selection of wheels for 6 lug preferably.

 

You can run Impreza struts and driveline then. The XT6 knuckles are what the EJs were based on and well worth it!

Link to comment
Share on other sites

^^^ this is what determined my choice to go five lug instead of six. Opens up more options than just wheels.

 

From running Outback struts to Impreza Tokicos, not to mention any 5x100 wheel on the market, the 5-lug swap is worth it if you can come up with the Parts. THe XT6 hubs are kinda like gold to the Aussies since they never had the XT6 (Although they did get the Vortex) but in limited numbers.

Link to comment
Share on other sites

Why not have two Cool Subies? Hell, I have 3 vehicles. No crime in that ;)

 

yeah buddy! if i could have these three ( witch i will one day ) i would have my current car ( 85 wagon, soon to be lifted 2" ) my next car ( 06' wrx, turbo hatch back ) and if i find one ( 78 wagon, cherry red )

 

one day......

Link to comment
Share on other sites

yeah buddy! if i could have these three ( witch i will one day ) i would have my current car ( 85 wagon, soon to be lifted 2" ) my next car ( 06' wrx, turbo hatch back ) and if i find one ( 78 wagon, cherry red )

 

one day......

 

I think the '78 Wagon will be the most hard to find ;) Although, it would probably be the cheapest on the list!

Link to comment
Share on other sites

ya i paid 500 for my car up front, and since then have put about 3k into it. i probably wont get what i want out of that 06' wrx for less than 15k ish. and i dont even know where to look for a 78 besides japan, lol

Link to comment
Share on other sites

touche...

 

Lol! Well. They junk cars that are 10 times cleaner then what I'm trying to save. Outstanding isn't it? I can't get over how many clean running Subarus they junk out west because it has a rust hole in the door about the size of a golf ball... :horse:

Link to comment
Share on other sites

Lol! Well. They junk cars that are 10 times cleaner then what I'm trying to save. Outstanding isn't it? I can't get over how many clean running Subarus they junk out west because it has a rust hole in the door about the size of a golf ball... :horse:

 

im tellin you man, get out here. drive back. all smiles.

Link to comment
Share on other sites

Please sign in to comment

You will be able to leave a comment after signing in



Sign In Now
 Share

×
×
  • Create New...