Tires too big

[Bdhand]

Ok so I have a 66 bronco with a 170 straight six. It has 35X12.50's on it. I'm thinking they are way to big for that 6 cylinder!! Took it out for a spin this morning to test the new disc breaks and it seems like it struggled to even get to 35 mph!! What do you guys think. I want to keep nice size tires on there but no this big. What are the next 2 sizes down???

Thanks for the input
Brent

 

[EB70]

Try some 31x10.50's. Probably like it a lot better!

 

[bronccar]

What gears are you running and what wheel size?

Flotation size, you'd step down to 33", 32", 31" widths vary.

Here's a great resource to help determine tire size / gear ratio to hit desirable RPMs at cruising speeds, etc

http://www.grimmjeeper.com/gears.html

 

[bronccar]

*I only asked about wheel size b/c it impacts availability of tire sizes

 

[Prizefighter]

You don't need smaller tires, you need a bigger engine!

 

[Bdhand]

Not sure of the wheel size. Guess I just measure the diameter of them? Right now I don't have the money to do a bigger engine. I don't want to go fast just cruise but more than 25 mph! LOL! Here is a pic of the tire. Not sure about the gear ratio either. How can I find that out?

 

[Prizefighter]

It says on the tire 35x12.50x15 so you have 15" wheels. Measuring the diameter will not give you the right number and that wheel probably measures close to 17". Most wheels have the size stamped on the inside for future reference. You could see 15x8 or 15x10 on those. I have even seen where the width is listed first then the diameter so it read 10x15.

As far as finding your gear ratio, it should have come from the factory with 4:11 ring and pinion since you have an I6 engine. The V8s came with 3.50 gears. You probably have a tag on the axle that will tell you, look near the differential cover for a rectangle tag with numbers stamped on it.

 

[Bdhand]

So I'm gonna get rid of these so what size do y'all recommend??

 

[DirtDonk]

those are some wide wheels it looks like. Probably just the angle of the camera at the time, but it almost looks like they're bulging that tire out like a 12" wide wheel would!

The most common width for that "look" would be 10" wide, which would dictate that you stick with a 12.50" wide tire even if you go shorter. So that 33" mentioned would be the next logical move if you have to keep the wheels for now.

While you "can" go with a narrower tire, many shops wouldn't even mount a 10" wide tire on a 10" wide wheel because it's not within the manufacturer's specifications. And if you did manage to mount one, it's not the best for tire wear, handling or bead retention.
Not sure if you're going to do any off-roading with this rig or not, or if you will ever have occasion to run lower air pressures. So the whole bead-retention thing might not even come up. But it's there in the background, looming so to speak, so just wanted to mention it.

If those turn out to indeed be 12" wide wheels, your tire choices just got much narrower.

The good news is that your existing tires sure looks like they have not been used much. Should be easy enough to sell a set of 35 inch ProComps I would think. Assuming they're not too old that is.

Good luck.
Let us know when you determine the gear ratio. Yours could even have been optioned with 4.56 gears, but from your description it's more likely you still have the 4.11's I would think.

Paul

 

[Bdhand]

I'm gonna go with new rims and tires. So the whole set will be for sale when I get to that point. Vin # says 4.11 gears and I have no reason to believe they have been changed out. I am assuming that they are the original.

 

[DirtDonk]

Sounds like a good plan.

Paul

 

[blubuckaroo]

To start out, I have to say I love the sound of six cylinder engines and would keep it.
Keep the tires around 30" and enjoy it.
Also, narrow tires cause less drag than floatation tires. Something to keep in mind when shopping.

 

[Prizefighter]

My previous comment about not needing smaller tires and needing a bigger engine was mostly sarcastic humor and a little bit of truth. The 170 doesn't put out much power but it all depends on what your intended use for the Bronco is. Everybody wants a 302/351 and I think being unique and different is cool, changes it up a bit and not boring. Keeping the little inline six would be more original to the Bronco and could work perfect for what you need so don't rule that out and instead drop down in tire size.

You have to remember that when Ford designed that Bronco it had about a 29" tire on it. Increasing the tires to 35s requires more energy to turn them, and stop them. Personally, I love the stance of your Bronco but a 31" tire would be much better. If you could find some stock steelies then you would have a narrow wheel that would be easier on your steering components. A 15x8 wheel would be good too. Lastly, I don't think you would have a problem selling those wheels/tires that are on it now. A tire like that in a 15 inch wheel is hard to find now days and the 5x5.5 bolt pattern of the wheels will fit older Fords, older Jeeps, and Dodges so there are plenty of people in your target audience.

 

[englewoodcowboy]

Your other option if you do like that tire combo is to swap to a set of 5.38 gears. It will get you so you could scoot around town and cruise a little with the 6 cylinder. Even dropping tires sizes with the 6 cylinder it will be anemic and you will eventually want new gears or a v8 swap. The cost of a gear swap is similar to what a new set of wheels and tires would run so log as you had a decent mechanic.


Sent from my iPad using Tapatalk

 

[Bdhand]

I like the stance of my bronco too and that is something that I don't want to loose by going to smaller tires and rims. I'm guessing the gears would have to be changed out in the front and the rear? Is this correct? Another option is I have a bronco friend here in town that has a 302 sitting on a stand that needs to be rebuilt and he said he would give it to me. But what cost is there in rebuilding a 302 and what changes to the tranny would have to be made.

 

[bronconut73]

I like the stance of my bronco too and that is something that I don't want to loose by going to smaller tires and rims. I'm guessing the gears would have to be changed out in the front and the rear? Is this correct?

Yup.....

 

[bronconut73]

The rear 9" is really easy to do.
You could do that one your self then take the front Dana to an axle mechanic when funds are available.

 

[sykanr0ng]

Another option to taking it to a shop for the gear change may be to find some Bronco brothers that have the skill and tools to change the gears.

As much as I am a fan of the V8 engine and a fan of modifying, I would keep a six cylinder Bronco as a six cylinder Bronco.
What I would do is swap in a larger six instead, either a 250 or a 200.

There is actually quite a bit that needs changed when swapping a V8 into a Bronco that came with a six.

 

[Bdhand]

So it sounds like smaller tires and rims (that look good) and different gears is the way to go. I jus hope I can find some smaller tires and rims and still keep somewhat of a good look with the 3" lift that is on the bronco. I really didn't want wide tires like are on there now anyway but I don't want some that look too small either. I guess skinner but still as tall is the way I need to go. I like the look of the BF Goodwrench on the bronco's.

 

[Prizefighter]

Another option to taking it to a shop for the gear change may be to find some Bronco brothers that have the skill and tools to change the gears.

As much as I am a fan of the V8 engine and a fan of modifying, I would keep a six cylinder Bronco as a six cylinder Bronco.
What I would do is swap in a larger six instead, either a 250 or a 200.

There is actually quite a bit that needs changed when swapping a V8 into a Bronco that came with a six.

X2. I second this.

One other thing I want to highly encourage you to do - Enjoy your Bronco and slowly make changes. What I mean is you can start looking at what everyone else has and decide you want to upgrade everything about it (engine, axles, suspension, etc.) then get yourself into a major overhaul. I know because I'm in the middle of that process. You have a solid Bronco it seems, make the few changes you need to be able to have fun while you drive it. Change the gears out, see if you can find a 250, and drive it while having fun the whole time.