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Help! I'm overthinking tire sizes!

Shimmy

Contributor
1977 Bronco
Joined
Jun 20, 2021
Messages
594
Loc.
Maple Valley
as mentioned above, 2.5" and 33's is perfect. I'm at 3.5" with a 1" BL on 35's and always think about lowering to 2.5" and going 33's. a lower lift and smaller tires is always more streetable. if you are staying with 33's i'd go 15" wheels. Lots of options and 15's look better IMO.
 
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NickMcAFP

NickMcAFP

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Sturbridge
33s all the way with that lift It is a great look and as you dad and other say they just look right on the early broncos! I had 33x 12.50 x 15s on a few broncos and they looked great and wheeled well. My 70 has 33x 10.50x 15s BFG AT/2 on it with no lift, 302, 3 speed, and 4.10 gears and it clears fine is good on the street. I have had great luck with the BFG AT tires for the last 30 years. Run them on everything from broncos, f150s, and F250s. Long tread life ok off road and quiet on road.
How do the 10.50 compare to the 12.50?
 
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NickMcAFP

NickMcAFP

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Here is a pic of mine with 2.5” lift and 1” body lift with 32 x 11.50s . While 33s would fill the wells a little better. I think you could run 32s and be pretty pleased with the look. Kinda the half way point of what your talking about. Split the difference and you can’t go wrong. Gears matter . I am running 4:11s and seems to be just about perfect for what I am running. Just my two cents worth.
How's the speedometer with that combo? Looks great! I honestly have a hard time telling the difference between 32s and 33s in most photos.
 

661buster1963

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Feb 18, 2009
Messages
287
When I had very little funds to work on my bronco I was always amazed when I would give a call to K bar S at the time they had recently moved to Las Vegas that John Karp would answer the phone. He was a freaking bronco genius and would entertain every question I ever had. They guy was always chatty, always upbeat, and his recommendation was to stay no bigger than 32” tires. Times may have changed, but still good recommendations. Much bigger and Dana 30 or 44 will struggle some to stop and start.
 
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NickMcAFP

NickMcAFP

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Your dad was right. An Early Bronco lifted 2.5 with Carpenter quarters should be on 33's.

The proportions are right, and the tires fit, and it will be very capable off road.

I'm running 35's, but I'm 3.5 lift with a 2 inch BL. I'm not saying that 33's would be perfect...but they actually are.

If you want road friendly, get the BFG All Terrain KO and 17 inch wheels. And listen to your father...he's not wrong.
Your 35s don't stick out too far without the flares on the front? I was worried about trying to pull off 12.50 wide tires with stock fenders
 

DirtDonk

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Bronco Guru
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Nov 3, 2003
Messages
47,345
The 12.50's almost always stick out some. But fender flares minimize that.
However the key to how much or how little they stick out past the sheet metal and flares is the wheel the tire is mounted to. After all, a 12.50 is a 12.50, whether it's a 33 or 35 or even 37.

The wheel width and backspacing/offset are key to looks, sometimes road manners, and definitely fitment. Put a tire on an 8" wheel with 5" of backspacing and it's tucked in pretty decently. Put that same exact tire on a 10" wheel with 3" of backspacing, and it sticks out like a skateboard!

Paul
 

TDubya

Sr. Member
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Aug 3, 2009
Messages
381
Loc.
Fortuna, CA
How's the speedometer with that combo? Looks great! I honestly have a hard time telling the difference between 32s and 33s in most photos.
I originally had 3.50 gears with whatever size tires that came stock on 75 Rangers. With the current setup of 33s and 4.11s the speedometer is dead on without having to change the speedo gear.
 
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NickMcAFP

NickMcAFP

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The 12.50's almost always stick out some. But fender flares minimize that.
However the key to how much or how little they stick out past the sheet metal and flares is the wheel the tire is mounted to. After all, a 12.50 is a 12.50, whether it's a 33 or 35 or even 37.

The wheel width and backspacing/offset are key to looks, sometimes road manners, and definitely fitment. Put a tire on an 8" wheel with 5" of backspacing and it's tucked in pretty decently. Put that same exact tire on a 10" wheel with 3" of backspacing, and it sticks out like a skateboard!

Paul
I wasn't planning on running flares. I was looking at those 15 inch Indy mags. I think the backspacing on the 15x8s is 4. I have an unknown disk brake setup in the front though so I'm not sure how they'll fit without spacers
 

DirtDonk

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Ahh, you've been reading about the rubbing issues recently? Seems to be an issue with some of the Chevy conversions, but not all. And yours would in theory have those, but someone (your dad?) might have used Ford parts instead.

Next time you're under there looking, or have a wheel off, look at the calipers themselves. If they slide on two pins, they're GM based items. If there are no pins but they slide instead on two smooth surfaces, where the lower one has an additional slider bracket and single bolt, then it's Ford stuff.
Hard to see unless you're looking right at the caliper up close sometimes.

Paul
 
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NickMcAFP

NickMcAFP

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Ahh, you've been reading about the rubbing issues recently? Seems to be an issue with some of the Chevy conversions, but not all. And yours would in theory have those, but someone (your dad?) might have used Ford parts instead.

Next time you're under there looking, or have a wheel off, look at the calipers themselves. If they slide on two pins, they're GM based items. If there are no pins but they slide instead on two smooth surfaces, where the lower one has an additional slider bracket and single bolt, then it's Ford stuff.
Hard to see unless you're looking right at the caliper up close sometimes.

Paul
I've been reading everything. It's really about all I can do. I'll check on the calipers. I suppose replacing them isn't out of the question at this point if they are going to be a problem. We've replaced just about everything else.

The rubbing is was got me considering smaller tires in general. I can just picture everything painted and the tires coming in and not fitting.. and that's what's got me waking up at 2am now.

Thank you for the information!
 

DirtDonk

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47,345
Oh, the other thing about wheel fitment and backspacing would be if the disc conversion was using '76 or '77 Bronco disc brakes. That's where the more traditional issue comes up. Not of the wheel hitting the brake caliper or backing plate, but of the wheel edge hitting the actual tie-rod ends where they mount to the steering arms.
That's where backspacing is an issue once it gets over 3 5/8" or so. Until you get into a 17" wheel, where that issue almost goes away completely.

Paul
 

DirtDonk

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With stock uncut fenders you always have to look out for rubbing. Are you cut in the back? Or was that you that said you've got the new DC rear fenders? I thought it was someone else today, but I could have everyone mixed up.
If you have stock uncut fenders in the rear, then the discussion of 33's (of any width) and 285's takes on a whole new level of discussion.

Paul
 

TDubya

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Fortuna, CA
My 33s are mounted on 15x8 American Racing Outlaws w/ 3.75" backspace and have no clearance issues with the front Chevy disc conversion
 
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jamesroney

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Fremont, CA
Your 35s don't stick out too far without the flares on the front? I was worried about trying to pull off 12.50 wide tires with stock fenders
Ugh. My bronco is a terrible role model. and I'm a terrible resource to ask. And "stick out too far" is pretty subjective. However...

The early Bronco is kinda funny because the front axle is 1.25 inches wider than the rear. The original rear 9 inch was 58.25 WMS.

The Bronco Front Dana 44 with Ford Disc Brakes is 59.5 inchs WMS. Mine is a HP44 with Early Bronco shafts, Long side cut 6, and the short side was cut 5/8. I didn't like the way the rear axle looked skinny...so when I built my rear High Pinion 60, I set the rear WMS to 60.

So...the stock front fenders cover the outer TREAD block of the KM2's. The sidewall bulge is definitely farther out, but I think the legal requirement for "stick out too far" is to cover the tread. So that means that if I throw a rock vertically, straight up from the outer tread block, there is a high likelihood that it will hit metal. I went to great pains to center the track under the fenders when I built the trac bar riser...but of course the bronco settled about an inch after I put all of the accessories on it. So now the axle is shifted to the passenger side by 1/2 inch. Coincidentally, my D44 Yoke put a dimple in my exhaust pipe about 1/2 inch deep.

I'm running Hutchinson Rock Monsters at 17x8.5 with 4-5/8 backspace.

I saw about 50 Broncos at Prairie City last weekend. I saw a lot of full width axles. I saw a LOT of tires sticking out past the fenders. I didn't see any tires that stuck out "too far." I thought they all stuck out "just right."
 

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NickMcAFP

NickMcAFP

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With stock uncut fenders you always have to look out for rubbing. Are you cut in the back? Or was that you that said you've got the new DC rear fenders? I thought it was someone else today, but I could have everyone mixed up.
If you have stock uncut fenders in the rear, then the discussion of 33's (of any width) and 285's takes on a whole new level of discussion.

Paul
I have the DC quarters, yes. So right now it's DC in the back and stock in the front.

I'll look at the discs but my father installed them in the mid 90s so they are likely whatever was the most readily available option back then.
 

DirtDonk

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Unfortunately, either one...
But maybe more likely the Ford version because the GM version had not gained much favor yet, at that time.

If he did what I did, and used F150 brakes, then you won't have that same issue with the wheels hitting the rod ends. Guessing using the Early Bronco version was more common, but you won't know for sure until you look and take some measurements and maybe pics for us if you're not sure.

Paul
 

EB70

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Jun 9, 2006
Messages
696
I'd run the 33's. I really liked my Bronco with them. I would not run any smaller but that is just me.
 

Yeller

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Mar 27, 2012
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5,881
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Rogers County Oklahoma
Ugh. My bronco is a terrible role model. and I'm a terrible resource to ask. And "stick out too far" is pretty subjective. However...

The early Bronco is kinda funny because the front axle is 1.25 inches wider than the rear. The original rear 9 inch was 58.25 WMS.

The Bronco Front Dana 44 with Ford Disc Brakes is 59.5 inchs WMS. Mine is a HP44 with Early Bronco shafts, Long side cut 6, and the short side was cut 5/8. I didn't like the way the rear axle looked skinny...so when I built my rear High Pinion 60, I set the rear WMS to 60.

So...the stock front fenders cover the outer TREAD block of the KM2's. The sidewall bulge is definitely farther out, but I think the legal requirement for "stick out too far" is to cover the tread. So that means that if I throw a rock vertically, straight up from the outer tread block, there is a high likelihood that it will hit metal. I went to great pains to center the track under the fenders when I built the trac bar riser...but of course the bronco settled about an inch after I put all of the accessories on it. So now the axle is shifted to the passenger side by 1/2 inch. Coincidentally, my D44 Yoke put a dimple in my exhaust pipe about 1/2 inch deep.

I'm running Hutchinson Rock Monsters at 17x8.5 with 4-5/8 backspace.

I saw about 50 Broncos at Prairie City last weekend. I saw a lot of full width axles. I saw a LOT of tires sticking out past the fenders. I didn't see any tires that stuck out "too far." I thought they all stuck out "just right."
Your bronco is headed down that slippery slope of being a bad roll model, fortunately it’s not near as far down that slope as mine…LOL

I have 33x12.50 (not on my bronco…..) on 15x9 us mag slots with 4.5” of backspacing. I love how they look. I think 8” wide wheels is tucked a bit tight on the sidewall and I think 10” wide is a bit fat. I also have them on a GM brake conversion with 78/79 rotors and hubs. This combination will not fit a 76/77 front axle.
 
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