Hey Dave - wheel question

AZ-Nick · Post by **AZ-Nick** » Tue Apr 05, 2005 4:26 pm

I was ready to buy the wheels for my X in a 4 3/4" backspacing when I was offered a new set in 4 1/2" backspacing at a great price, so I jumped on them. The question I have is, in the wheel spacing thread you posted that the 295 tire would have approx 3/4" clearence on both the inside and outside of the tire to the spring and quarter. That will leave me with 1/2" on the quarter side and 1" on the spring side, I think can live with that.
You then said "your tire is a 295x50", why did you go with only a 50 and not with a 60 tire? I want to run a 60 if I could.

AZ-Nick · Post by **AZ-Nick** » Tue Apr 05, 2005 5:42 pm

One more thing, you said you have 3/4" of room to the quarter.
looking at both these pictures of your car it sure looks like you have a bunch more that 3/4". Where is the measurment taken from?

Post by **Dave** » Thu Apr 07, 2005 9:06 am

Hey Bud!

Actually, flip your measurements around. You'll have 1/2" or so to the spring, and 1" to the quarter. You measure back space from the rear face of the rim to the hub, so a smaller backspace value moves the rim further under the car. FWIW, I did consider running the 4.5" backspace rims, becuase they have the really deep look to them. I had access to a guy that made me up a set in 4.75" for a really decent price, and this being my first real adventure into this type of thing, I felt I'd rather be safe than sorry. Though now looking back, I'm quite sure the 4.5" would have worked ok with the 295s.

You are going to have a hard time finding a 295 in 60 series. the BFG's only offered it in 50, so that's what I went with. Matter of fact, www.tirerack.com doesn't show a single tire in 295-60-15.

The clearance to the quarter panel is kinda an interesting calculation. Here are the steps I went through:

1) Mount the bare rim on the car - use 2 or 3 lug nuts to ensure the wheel won't move during this excercise.

2) Hold a yard stick across the face of the rim - to extend the plane of the rim higher into the wheel house.

3) Measure from the innermost lip of the quarter panel to the back side of the yard stick (so you include the width of the yard stick in the measurement). --> This gives you the clearance of the rim to the quarter.

4) Determine the section width of your tire, mounted on an 8" rim. (Might have to check with your retailer, or the manufacturer.) My BFG's are actually a little wider overall (not tread width, but secton width) on an 8" rim than they would have been on a 9".

5) Subtract 8" from that section width, and divide the result by 2. This gives you the amount of "overhang" of the tire (past the face of the rim) on either side.

6) Take the value from step 5, subtract from the value in step 3, and that is your calculated tire to quarter clearance.

Remember that this section width is not at the TOP of the tire, but 1/2 way down the sidewall (give or take a little bit). Therefore, in order to actually have that calculated clearance, you'd have to have the car loaded pretty well, or really be pressing it into a curve.

Basically, the clearance to the quarter is an important measurement to take into account, but not nearly as critical as the tire to spring clearance.

Hope this helps!

AZ-Nick · Post by **AZ-Nick** » Thu Apr 07, 2005 11:34 am

thanks for the response back.
I guess the older we get the more we forget. you explained it very well.

Post by **Dave** » Thu Apr 07, 2005 12:12 pm

No problem, Nick. Until I started Project Blue Bird, I didn't know this stuff at all.

FWIW, I'm running the 245-60's up front, and they are just 0.1" shorter overall than the 295-50's - perfect for how I plan to set the car up. I want to be able to set the mild rake these cars need to look "right" just with the T-bar adjustment.

AZ-Nick · Post by **AZ-Nick** » Thu Apr 07, 2005 12:32 pm

245-60, thanks