rymanrph
Well-Known Member
I'm planning on taking the car to the tire shop on Saturday so I'm curious to see what they say.
Front Rubbing - Tires, Suspension or Wheels?
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rymanrph
Well-Known Member
Here is what I found. The wheels on the front right now are actually 15x6 with 3.375 back spacing. The rear are 15x9 with most likely 6.5 backspacing. I'm guessing on the back spacing by looking at what's available to purchase new (yes I know I could take the wheel off and measure, but I just haven't had a chance).
I went to Discount Tire today to get their input. He didn't actually measure anything except the wheels I already had and then made some recommendations. With that said, I thought I would post his recommendations and see what the consensus is here.
For the front, he recommended a 17x7 with a bs of 3-3.5" with a 225/45/17. I can get a TTII in a 17x7 with 3.5" bs.
For the rear, he recommended a 18x8 with a bs of 3.5-4" with a 275/40/18. I can get a TTII in a 18x8 with 3.75" bs.
Thoughts? The guy seemed to know what he was talking about, but since he didn't actually put a measuring stick to the car, I'm a little hesitant. If I order what they recommend and they don't fit, they'll have to take them back and get me the right size, but I don't want to go through that hassle if I don't have to.
I went to Discount Tire today to get their input. He didn't actually measure anything except the wheels I already had and then made some recommendations. With that said, I thought I would post his recommendations and see what the consensus is here.
For the front, he recommended a 17x7 with a bs of 3-3.5" with a 225/45/17. I can get a TTII in a 17x7 with 3.5" bs.
For the rear, he recommended a 18x8 with a bs of 3.5-4" with a 275/40/18. I can get a TTII in a 18x8 with 3.75" bs.
Thoughts? The guy seemed to know what he was talking about, but since he didn't actually put a measuring stick to the car, I'm a little hesitant. If I order what they recommend and they don't fit, they'll have to take them back and get me the right size, but I don't want to go through that hassle if I don't have to.
Wow. Those won't even come close to fitting. Not even close.
In the front, even for a 7" rim you need 4.25" of backspace. Less than 4" will cause you problems with a 225/45/17. I know this because I have 15x7's with 4.25" of backspace and 225/60/15's on my Duster right now, and there's very little room to the fender. 3.5" of backspace will NOT work on a 7" wide rim with a 225.
In the back, again, not going to fit. For an 8" rim you're going to want 4.5" of backspacing for a 275. Also, I seriously doubt you have 6.5" of backspace on those rear wheels. I say that because if you have a stock A body 8 3/4 your tires would be about 1" on the inside of the inner fender well. By the looks of the picture, I'd be surprised if you had more than 4" of backspace right now, since the tires are hanging out of the quarters.
What's REALLY surprising to me is that he recommended a 275/40/18 on an 18x8", because the smallest recommended width for a 275/40/18 is 18x9". I'm not saying you can't fit a 275/40/18 on an 18x8, but I can tell you that it's against the manufacturers recommendations for EVERY 275/40/18 that I've ever seen.
If you want to run 17's and 18's, this is what I would do.
Get a 17x8 with 5.3 to 5.6" of backspace in the front and run a 245/45/17. In the back, get an 18x9" with 5" of backspace for your 275/40/18. But, in the back, if you're spring's aren't offset you're going to be shoehorning those 275's in there. You might be better off just going with a 255/40/18, or even a 265/40/18. If you do have a spring offset, then you shouldn't have any issues, and should probably run more like 5.25" of backspace.
rymanrph
Well-Known Member
Another question. Is there any difference in looks between the one and two piece versions of the TTII? If they look the same and I can get away with a 4.0 bs on the front as opposed to a 3.5 then I can save a significant amount with a one piece wheel. The difference just at Summit is $56. I could knock off another $59 each through Amazon. That would save me $230. I think I'm stuck with the two piece for the rear.
I agree. Pictures attached. Front is 245/45-17 and rear is 255/50-17. 17x8 all four corners. Backspacing on the front wheels was 5.5". I think the rear was 5", but do not remember for sure. Rear was a little high in the pictures because I had SS springs. Front suspension was '73-'76 disc spindle with a Cordoba rotor, rear was stock A body housing with Moser resplined C body axles and 1970 B body drum brakes.
What your tire "expert" does not realize is that diameter makes a huge difference on the wheel clearance to the suspension on the front. 15" wheel is limited to 4.5", 16" is limited to 5.0", 17" is limited to about 5.5", and 18" is limited to when the tire hits the frame at full lock. Each increase in diameter allows you to clear more. 15" is limited by UCA, 16" is limited by the UBJ, 17" is limited by the OTR. 18" definitely clears the OTR... I was test fitting 18" today on the front with 6.5" backspacing.
Note: for 17" I had to swap UBJ to clear the wheel. Tall style on the left would not clear with a grease fitting.
rymanrph
Well-Known Member
I'm actually good on the upper ball joints because I just replaced the driver side today, so I know both sides have the smaller profile. Oh and I do have relocated springs, so the clearance there is not a problem.
Ok, so here is another issue. I just measured my rear end. I thought it was a A body rear end, but it appears to be a narrowed B body (the internal measurement of the brake drum was 11" so I assume that's the factory B body brake). Best I can tell, its 49" between the backing plates. I took a straight edge from the mounting surface of the drum and measured to the fender lip and the tub. From the mounting surface of the drum to the fender lip was roughly 6.25". From the mounting surface of the drum to the tub was roughly 6".
And you guys were right about the back wheel. The guy at discount measured it and said it was a 15x9 (so I just looked up the bs of the only wheel in that width). It is actually a 15x10 with a 5" back space. He told me the front was a 15x6, but I'm not so sure about that either...
I feel confident with the 17x8 245/45 up front, but now I need some help with the rear. Thanks guys.
Ok, so here is another issue. I just measured my rear end. I thought it was a A body rear end, but it appears to be a narrowed B body (the internal measurement of the brake drum was 11" so I assume that's the factory B body brake). Best I can tell, its 49" between the backing plates. I took a straight edge from the mounting surface of the drum and measured to the fender lip and the tub. From the mounting surface of the drum to the fender lip was roughly 6.25". From the mounting surface of the drum to the tub was roughly 6".
And you guys were right about the back wheel. The guy at discount measured it and said it was a 15x9 (so I just looked up the bs of the only wheel in that width). It is actually a 15x10 with a 5" back space. He told me the front was a 15x6, but I'm not so sure about that either...
I feel confident with the 17x8 245/45 up front, but now I need some help with the rear. Thanks guys.
rymanrph
Well-Known Member
Based on my measurements, the mounting surface of the wheel is roughly centered in the wheel well. I can only get a 18" TTII in an 8" width (or I can jump up to a 9.5"). If I understand this correctly, since my mounting position is centered, then I would want my bs to be half the width of the wheel. So for the 18x8 there is a 4.25" bs (with a -6 mm offset), so wouldn't that put me right where I need to be?
If I'm totally off then fine, but I tend to understand things better when I try to figure something out and then someone explains to me why I'm wrong as opposed to just telling me what I need.
If I'm totally off then fine, but I tend to understand things better when I try to figure something out and then someone explains to me why I'm wrong as opposed to just telling me what I need.
:sign3: Exactly this. Most of the 17's can get away with 5.6" of backspace, but that's dependent on the style of rim. I've heard of 17" rims that needed to be spaced out to 5.5", and others that worked at 6" of backspace. 18's are good up to about 6.5" of backspace. Much beyond that you'll start running into frame clearance issues. But 72BBswinger had a 275/35/18 on an 18x9 with 6.5" of backspace and didn't hit the frame.
As far as the rear end, an 11" diameter brake just means that someone put B body brakes on it. I have 11x2.5" drums on my Challenger, EL5 Dart (which has an A body 8 3/4), and my Duster. All they require is a BBP axle, they'll work in any housing. 49" backing plate to backing plate isn't that far off an A-body measurement. 52 5/8" is the flange to flange measurement for an A body, but keep in mind that the backing plate to backing plate measurement will be less than that. I get ~49.5" doing a quick measurement on my Dart, it has an A body 8 3/4 with 11x2.5" brakes. Problem with the backing plates is they aren't flat, so you can measure to different places and get different #'s.
I'd be that your axle is either an A-body rear that was converted to BBP axles, or one that was narrowed to A body specs (or very close to it).
And the 15x10 with 5" backspace pretty much says the same thing based on how it fits, looks like it sticks out a bit. Which would be about right for a stock length axle.
I'd get the 18x9.5 AR TTII. They come in two backspaces that would be useful, either 5.25" or 5.5". I would bet that the 5.25" backspace 18x9.5 would be about perfect. But if you tell me how much clearance you have on the inside of that 15x10" wheel I could tell you exactly what you need. I just need the size of the tire on it and what the distance is to the first thing that it would hit.
rymanrph
Well-Known Member
The tire on there now is a 295/50/15 and there is no distance between it and what it would hit. It already rubs on the tub and the fender lip (more so on the tub).
Go measure that wheel about three more times... if you are barely rubbing on both sides with a 295 and want to run a 275/40-18 it fits perfectly on a 9.5" wheel. What you want is the same offset. It sounds like your wheel is centered. Measure the outside of the wheel from edge to edge, a 10" wheel will measure about 11" outside edge to outside edge. If your 295 is rubbing a 275 will give you almost 1/2" more room on each side if it is centered.
Now, how to calculate offset... 11" divided by 2 is 5.5". If your wheel measures from the mounting face that sits against the brake drum to the back edge of the wheel 5.5" that would be 0" offset. Anything less is negative offset, anything more is positive offset. Use a good straight edge laying on the outside of the wheel lip when measuring backspace, it is easy to measure this wrong. I use my carpenter square. If you are measuring 5" that is -0.5" or -12.7mm offset. You want the same offset on your 9.5" wheel. Since a 9.5" wheel measures close to 10.5" that means 0" offset would be 5.25" backspacing. -0.5" offset would measure 4.75" backspacing. Another way to think of it is that your wheel is 1/2" narrower than the one it is replacing and you want to take 1/4" off both sides to keep is centered. That is 5" - 1/4" which gets us back to 4.75".
Make sure you get them to check the backspacing on whatever wheel you order. I was looking at Summit's website and the descriptions were all jacked up; the size, backspace and offset numbers they had listed did not add up. One of the numbers is wrong on several of their descriptions. Surprisingly few people can calculate offset correctly, so I usually stick to backspacing when I discuss wheels. That includes people that work with tires and wheels.
If they do not have the 9.5" with the backspace you need a 275 will work fine on a 9" wheel. Just take 1/2" off the backspace of your 10" wheel, so, assuming 5", that would put you at 4.5" backspacing on the 9.
rymanrph
Well-Known Member
Its a little difficult since the tire sticks out past the wheel lip, but here is what I did. I put the straight edge against the edge of the tire and measured from the mounting surface = 5.6875 (5 11/16). Then I measured from the edge of the rim to the straight edge = .8125 (13/16). That difference is 4.875 (4 7/8). From 5.5" that's .625" or ~16mm. Summit lists the wheel at -12mm and the Center Line website says 14 lbs (whatever that means).
-12mm is about -1/2". The difference between 12 and 16 isn't much more than 1/8" so -12mm, or -1/2" is probably the right answer. Is 14 lbs the weight?
rymanrph
Well-Known Member
I assume that it is, but I just thought it was interesting that it was listed under the offset.
So, if I want to match the placement of the current wheel (15x10 5" bs with 1/2" offset) with the narrower 18x9.5, then the 5.25 backspacing with 0 offset would be correct - right?
So, if I want to match the placement of the current wheel (15x10 5" bs with 1/2" offset) with the narrower 18x9.5, then the 5.25 backspacing with 0 offset would be correct - right?
No. That would move the inside edge of the rear wheel 1/2" deeper than where you are now. If you are rubbing on the inside now that would make it 1/2" worse. Not what you want.
If you want the 18x9.5 centered in the same space as the current wheel you need to maintain the same -1/2" offset. That would be 4.75" backspacing. If you are rubbing on the tub and the fender lip both this is what you want to do. Worst case, you decide you want to space it out a little (less offset) and you can run a thin spacer if needed.
This is why talking about offset and backspacing can get confusing...
Just think about it. You are at 5" backspacing now. If you go more that moves the tire closer to the frame. You are rubbing on the inner fender now. We want to move the other direction. By running a 9.5" wheel you do that without moving the center of the wheel by taking a 1/4" off each side. So your backspacing goes from 5" to 4.75" and the center of the wheel does not move. By going from a 295 to a 275 tire you are reducing the total width by 20mm (about 0.8"). Since the center is the same we effectively take 0.4" tire off each side and gain about that much in clearance.
I hope this clears it up for you.
Just think about it. You are at 5" backspacing now. If you go more that moves the tire closer to the frame. You are rubbing on the inner fender now. We want to move the other direction. By running a 9.5" wheel you do that without moving the center of the wheel by taking a 1/4" off each side. So your backspacing goes from 5" to 4.75" and the center of the wheel does not move. By going from a 295 to a 275 tire you are reducing the total width by 20mm (about 0.8"). Since the center is the same we effectively take 0.4" tire off each side and gain about that much in clearance.
I hope this clears it up for you.
rymanrph
Well-Known Member
Thanks for setting me straight (I think). I had to make a couple drawings and sketch everything out so it would make sense to me.
The TTII in an 18x9.5 isn't offered in a 4.75 backspace. There is a 5.00, but the only thing that would help me on the tub side would be the slightly narrower tire, though my clearance with the fender lip would be OK.
There is also a 4.5" backspace, but that would reverse the situation; I would gain a 1/2" clearance on the tub side (plus the difference in the tire, but I would be sitting exactly where I'm at on the fender side (minus the narrower tire). So is 0.4" enough on either the fender side or the tub side? I'm not so sure. Unfortunately, the wheel is not offered in a 9" width. Then next step down is 18x8.
The TTII in an 18x9.5 isn't offered in a 4.75 backspace. There is a 5.00, but the only thing that would help me on the tub side would be the slightly narrower tire, though my clearance with the fender lip would be OK.
There is also a 4.5" backspace, but that would reverse the situation; I would gain a 1/2" clearance on the tub side (plus the difference in the tire, but I would be sitting exactly where I'm at on the fender side (minus the narrower tire). So is 0.4" enough on either the fender side or the tub side? I'm not so sure. Unfortunately, the wheel is not offered in a 9" width. Then next step down is 18x8.
Get the 5" backspace 18x9.5. With the 275 it may work anyway. If not, you can run a small spacer, up to .25" without any issues, to get the clearance you need. If you get the 4.5" backspace and it rubs on the quarters, there's nothing you can do about it.
I agree... get the 5". Like 72blu states, you can always add a small spacer, you cannot make the wheel deeper! Once you get the wheel bolted on find out how much spacer you need and order a set of custom made hub centric spacers. Get the ID machined to fit on your hub and the OD of the center part to fit in the wheels hub. Make sure your studs are long enough to get plenty of bite, get longer studs if you have to.
Is the center bore on these wheels designed to accept a hub ring? Hub centric is always the best way to go if you can make it happen.
rymanrph
Well-Known Member
Here is the situation in the rear. This is a shot of the driver side:
Here is the best shot of the inside edge I could get (that's a small wire brush):
There is even less clearance on the inside of the passenger side (not a whole lot, but I couldn't get the brush in there vertically).
Because of how my exhaust is routed, the 295s are barely rubbing there as well in the corners.
I found a measurement of 57 1/8" for drum to drum on the 8.75 and mine appears to be just under that. I just hate to spend $740 on two wheels just to have to run spacers. I found that I have Mopar Performance Competition leaf springs (are these what everyone refers to as SS springs?) so I definitely want something lower and that worries me too with rubbing.
You mentioned long enough studs; this is what's on there currently:
I'll need to swap those out as well.
Here is the best shot of the inside edge I could get (that's a small wire brush):
There is even less clearance on the inside of the passenger side (not a whole lot, but I couldn't get the brush in there vertically).
Because of how my exhaust is routed, the 295s are barely rubbing there as well in the corners.
I found a measurement of 57 1/8" for drum to drum on the 8.75 and mine appears to be just under that. I just hate to spend $740 on two wheels just to have to run spacers. I found that I have Mopar Performance Competition leaf springs (are these what everyone refers to as SS springs?) so I definitely want something lower and that worries me too with rubbing.
You mentioned long enough studs; this is what's on there currently:
I'll need to swap those out as well.
It sounds to me like you've got a stock A body rear axle. They varied a little bit in length, so if its just under the 57 1/8" mark that its supposed to be drum to drum that's what I would say it is.
As far as the rubbing issue you've got now, as you've said before it looks like your wheel is pretty well centered. It would definitely contact on both sides if you lowered the car down.
Assuming you have the backspace measured correctly on your current wheels, that is to say 15x10 with a 5" backspace, the 18x9.5" with 5" backspace with a 275/40/18 should fit, as it will leave room on both sides compared to your current set up.
This is a tire program that I use to check specs on tire and rim clearances. It isn't the end-all-be-all, as tire sizes vary from manufacturer, but it really helps, especially if you have data from a combination that you know fits.
http://www.rimsntires.com/specspro.jsp
So I used your current data, and this is what it comes up with...
So it tells you that the new combo will have space all the way around it. If you "swap" the data, it tells you that the old combo sticks out .2" further on the inside and .6" on the outside. Which also tells you that you should have an extra .2" of clearance on the inside and .6" on the outside with the new combo. Looking at your clearance, I think that's pretty close to right. You seem to have a little more room on the inside, on the outside you're already past the quarters with your current combo, it wouldn't even be close if you lowered the car.
As far as the spacers go, that's life. Obviously it would be better not to need them, but as long as you use quality spacers they're perfectly safe, all kinds of folks use them on everything from daily's to race cars. When you get within a 1/2" of the body with your tire clearances the body tolerances are a big factor, and spacers can become a necessity.
From what the calculator says, you shouldn't need the spacers. But that will depend on how much you lower the car, and how well centered the axle is with the body. Either way, the spacer you'd need would be less than a 1/4", and those are readily available even in generic form, in plenty of hubcentric options.
As far as the rubbing issue you've got now, as you've said before it looks like your wheel is pretty well centered. It would definitely contact on both sides if you lowered the car down.
Assuming you have the backspace measured correctly on your current wheels, that is to say 15x10 with a 5" backspace, the 18x9.5" with 5" backspace with a 275/40/18 should fit, as it will leave room on both sides compared to your current set up.
This is a tire program that I use to check specs on tire and rim clearances. It isn't the end-all-be-all, as tire sizes vary from manufacturer, but it really helps, especially if you have data from a combination that you know fits.
http://www.rimsntires.com/specspro.jsp
So I used your current data, and this is what it comes up with...
So it tells you that the new combo will have space all the way around it. If you "swap" the data, it tells you that the old combo sticks out .2" further on the inside and .6" on the outside. Which also tells you that you should have an extra .2" of clearance on the inside and .6" on the outside with the new combo. Looking at your clearance, I think that's pretty close to right. You seem to have a little more room on the inside, on the outside you're already past the quarters with your current combo, it wouldn't even be close if you lowered the car.
As far as the spacers go, that's life. Obviously it would be better not to need them, but as long as you use quality spacers they're perfectly safe, all kinds of folks use them on everything from daily's to race cars. When you get within a 1/2" of the body with your tire clearances the body tolerances are a big factor, and spacers can become a necessity.
From what the calculator says, you shouldn't need the spacers. But that will depend on how much you lower the car, and how well centered the axle is with the body. Either way, the spacer you'd need would be less than a 1/4", and those are readily available even in generic form, in plenty of hubcentric options.
rymanrph
Well-Known Member
That program would have saved me a little time. I have a sketch pad sitting here at my desk with almost identical diagrams drawn out.
I'm pretty sure my rear axle isn't a factory 8.75, but its pretty close. I guess the only thing I'm concerned with at this point is will a 275 still allow me to lower the vehicle (more than it is now)?
This is my first car where the axle and wheels/tires came from:
I'd like for it to sit just a little lower than that in the rear. Lower than mosleyme's car in the above pictures (mine has Mopar competition springs that I'd like to swap out).
Thank you both for your help. I've spent way more time on this subject that I cared to, but I only want to spend $2k one time.
I'm pretty sure my rear axle isn't a factory 8.75, but its pretty close. I guess the only thing I'm concerned with at this point is will a 275 still allow me to lower the vehicle (more than it is now)?
This is my first car where the axle and wheels/tires came from:
I'd like for it to sit just a little lower than that in the rear. Lower than mosleyme's car in the above pictures (mine has Mopar competition springs that I'd like to swap out).
Thank you both for your help. I've spent way more time on this subject that I cared to, but I only want to spend $2k one time.
I have already dropped mine about 2"... looking to maybe go 1" more:
http://www.forabodiesonly.com/mopar/showpost.php?p=1326604&postcount=18
I went from the SS springs to -1" Caltracs. I have relocation spring boxes, so I can't lower the front eye but I can still add a lowering block.
rymanrph
Well-Known Member
I love that stance. If I could get mine to sit just like that I'd be happy.
I called and talked to the guy at Discount Tire yesterday. After telling him I wasn't comfortable with his recommendations, he made some excuses and then said that he could take some more detailed measurements (what I asked him to do originally and why I made the 30 minute drive there in the first place), but they would only be suggestions since my car isn't stock. I have liked using them in the past because their customer service is usually so good, but without that I can order everything I need somewhere else for cheaper.
I called and talked to the guy at Discount Tire yesterday. After telling him I wasn't comfortable with his recommendations, he made some excuses and then said that he could take some more detailed measurements (what I asked him to do originally and why I made the 30 minute drive there in the first place), but they would only be suggestions since my car isn't stock. I have liked using them in the past because their customer service is usually so good, but without that I can order everything I need somewhere else for cheaper.
I had the tires for my car mounted at America's Tire, same chain as Discount here in California. I bought my rims on the internet, MUCH cheaper.
But tires are kinda tricky. They're cheaper on the 'net, but after shipping, and then finding a shop to install them, usually at a higher price than if they sold you the tire, it usually ends up better to go through a shop. The tires I bought for my Duster were cheaper from America's than they would have been after shipping, mounting, balancing etc if I had bought them for "less" online.
But tires are kinda tricky. They're cheaper on the 'net, but after shipping, and then finding a shop to install them, usually at a higher price than if they sold you the tire, it usually ends up better to go through a shop. The tires I bought for my Duster were cheaper from America's than they would have been after shipping, mounting, balancing etc if I had bought them for "less" online.
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