Backspacing opinions on my car...please check it out

[Dr. Jeckel]

I have the stock t-type wheels with 245/60/15's on them and I measured from the frame to the tire and it is right at about 1" and from the inside of the lip on the fender to tire is also about 1 inch. I have black out trim on the car.
I am wanting to put 15x8 draglites on the car with 275/60/15 nittos. Everyone says go with 3.5" backspacing but that would put the tires about 1/2inch into the fender. Stock backspacing is 4", if i'm correct, so if I got 4.5" backspacing then I should still have 1/2" to the frame and to the fender lip on an 8" rim. I know the tire will be wider but with the 275 on an 8" rim it should stick out the same proportionally as the 245 on the 7" rim, shouldn't it?
This is probably very confusing...I have been thinking on this for the past 2 days.
Anybody else have an opinion? I'd like to hear it.
Thanks, James.

 

[stickybones]

Just my $0.02

I think most recommend the 3.5" backspace because it's easier to roll the fender lips than it is to notch the frame. With 4.5" backspacing and a 275 tire, you'll be real close to the frame...real close if not touching.

I would think that a 275 tire on 3.5" backspacing will probably put you under the fender lip. Don't know if that concerns you, but as I said above, it's easier to roll the lip than notch the frame.

How about a compromise? Can you get the wheels in 4" or 3.75" backspace?

Another thing to consider. Is your rear centered? Mine is off about .5" and I think it's common for then to be off a little bit.

 

[Dr. Jeckel]

I did make sure the rear is centered. The measurements are exactly the same on both sides.
So how much more are 275/60's going to stick out on an 8" rim compared to 245/60's on a 7" rim?
The draglites are only made with 3.5" or 4.5" backspaing, otherwise I would do 4".
I was just thinking that if I have a inch both ways then adding a 1/2" to both sides is going to be better than adding 1 1/2" toward the fender even if the 275 sticks out a 1/4" inch father on the 8" rim than the 245 on the 7" rim. After looking at it I just don't know if there will be enough room even if I do roll the lip.
Does anyone know for sure(I mean you measured yourself) if the backspaing on t type wheels is exactly 4" ?

 

[charlloots]

3.5 look at my sig my lips are not rolled and my frame is not not notched

 

[stickybones]

So how much more are 275/60's going to stick out on an 8" rim compared to 245/60's on a 7" rim?

Probably not much if at all.

As for the rest, all I can say is that I couldn't fit 255 tires on a 16x8 rim with 4.5" backspacing because the tire would rub the frame. Now of course, my rear was off a bit and this was the tight side. As for your car, if you're confident in your measurements, than go with what you think is best. All cars are a bit different and I have no personal experience with your particular application.

(I also have a GN so I don't know for sure about the T-Type wheels. GNTType.org may have the backspace number you're looking for.

Good luck.

Mike

 

[camino70]

Just a thought:
How about going with the 4.5" BS and if there are any problems, go with aluminum drums in the rear and/or possibly a .25" - .5" spacer.

Ron

 

[Dr. Jeckel]

That would work...I completely forgot about spacers.
Thanks!

 

[stickybones]

Be careful with spacers. If you need to use them I'd only recommend hub-centric ones...along with the obvious need for longer wheel studs.

 

[Dr. Jeckel]

I would only go with the 1/4" spacers at the most. The 245's are going on the wheels for right now. I'm sure they won't rub and then I'll know what kinda room I have.
Thanks for all the advice, James

 

[Dr. Jeckel]

Does anyone have any pics of 275/60's on 3.5" backspacing and or 4.5" backspacing on there car?
Thanks, James.

 

[Dr. Jeckel]

I was reading gnttype.org and I came across where it says that gn wheels have a 4" backspacing but t type wheels have 3 3/4" backspacing. Can someone verify this?
Here is the link:
http://www.gnttype.org/techarea/suspension/tired.html

 

[49-blues]

DR.Jeckel- that backspacing is correct. what i found that whatever size rim you choose- if you use a backspacing that keeps the rim centered-is usually the best fit. 4" bs on a 8" rim, 3.5" on a 7" rim, 4.25" bs on a 8.5" rim work the best on my cars. even spacing all the way around.

 

[stickybones]

Clarification to what 49-blues wrote...

There is a difference to advertised rim width and actual rim width. For instance, the GN rims are 15x7, but they are actually 8" wide. The 7" number is the width at the tire bead seat. Backspacing is measured from the extreme outer edge to the wheel mounting surface. So with the GN rim, 0 offset (or a centered rim) is equal to 4" of backspacing, not 3.5" (I'm not positive of the factory GN rim backspacing...never measured it, but I think I read some where that it has a small amount of offset...but that's not important in this thread). I imagine 15x8 draglites are actually 9" wide, so a centered draglite would need 4.5" backspacing for 0 offset.

 

[Dr. Jeckel]

Thanks for the help guys. I am going to go with 4.5" backspacing and get some 7/32" spacers incase they get to close. I remeasured and I actually only have 3/4" to the fender lip so that puts me 1/2"-3/4" under the lip and I'm not sure there is enough room to roll it that much. Once again, thanks for all the advice and I'll let ya'll know how it goes.
Thanks, James.

 

[Dr. Jeckel]

Thats why I am just going with the 7/32" spacer. And it is going to be a long time before my car sees enough traction, i.e. slicks, to be able to put enough stress on the studs to do any harm.

 

[Race Jace]

where the frame bends outward toward the edge of the car at the rear of the wheel well is where the clearance issues are going to be.

I have tried stock GN wheels with a 275/60/15 these are about the same as 28-10.5-15 slicks. they will not clear even with aluminum drums. they require a 1/2" spacer.

4" BS works great if your rim is 10" wide.
8" wide rims fit good with the 3-3.5max" BS.

If you try 4"BS on an 8" rim they will rub.

 

[Dr. Jeckel]

Well I have done the measurements on my car and beleive they will fit. Plus the wheels are ordered. If you put a 275/60 on a 7" rim they are going to pouch out on the sides alot more than an 8" rim. Plus 4" backspacing on a 10" or 8" rim is still 4" backspacing. the only reason they would work better is if you are using the same tire size for both, which would make it pouch less on a 10" rim. We'll see if I'm right or wrong come saturday.

 

[camino70]

How did you make out with this?

What width, backspacing and offset?

What tires?

Any pics?

Ron

 

[Dr. Jeckel]

Well after I waited till tuesday to get the right mags from summit the wheels went on fine. I went with 6" up front with 3.5" backspacing and 215/65 bfg's and 8" out back with 4.5" backspacing and 245/60 bfg's. Both sets just came off my stock wheels. The rear tires came pretty close to the frame were that stamp plate is so I had them put the 7/32" spacers I got from summit on and it gave me about 1/2" to the frame and probably 3/8" to that stamp plate. I probably have about 3/8" from the very outer edge of the tire to the inner fender lip. When my tires wear out I am going to put 255/60 on the back and 205/65 on the front. If you are planning on putting 275/60 DR's then this would probably not be the way for you as the DR's are much wider than a regular 275/60 tire, which I doubt I could fit on there without some rubbing. I don't plan on running DR's on mine so that is why I went this route.
This was the best choice for backspacing for me because if I would have got 3.5" backspacing then I would have been deep into the fender lip, 1/2" or more, and it would have taken alot of work to roll or cut them.
The front and rear tires fit real nice and I am very happy with the look of the new wheels compared to stock.
Hope this post helps out future people with there selection.

 

[strikeeagle]

You guys make me very happy that I have 7" Convos with 235/60 Radial TAs on my GN.

Jeeeeeessssssshhhhhhhh............