Downsizing tires?

[Cocobum]

Hey, I'm going to be doing a lot of highway driving these next few months and my Alts are almost bald and out of shape (meaning that the entire truck shakes when I exceed speeds of 55-65 mph). The tires are all balanced and the truck has been aligned 3 times.

Anyways, I have a set of almost brand new 235/75 R15 Michelin tires. I have 31x10.50 on the truck right now. What could I expect if I put those 235 tires onto the bronco?

(I'm doing this in an effort to save money because its running low)

Any pros or cons would help

Thanks.

 

[Seabronc]

The smaller the tire, the less road resistance so you will get a small gain in gas mileage. Don't forget that changing tire size requires a change in the speedo if your truck is in the 80's in order to make the Odometer reading correct. The smaller the tire diameter the higher the speed indication will be without the change.

 

[miesk5]

Right on Seabronc!

As Seabronc wrote, da Actual MPH will show Less on the PSOM; 55 MPH on PSOM is off by about 4 MPH.. so actual MPH would be 52 MPH; of course it does depend on Actual tire diameters of both sizes, as well as Tire Pressure...

Don't think your E4OD, if you have an auto, will be affected tho.. but if you feel that the shift points are off a bit, you can re-calibrate the PSOM

Replacement Size Calculator by Original Tire Size, Tire Width Aspect Ratio & Wheel Diameter w/ Corrected Speedometer Values by csgnetwork.com

Plug da numbers in and see how much the PSOM is off @ diff MPH

 

[Cocobum]

What is the stock tire size for a bronco? I've heard anything from 235 to 265

Thanks

 

[bigtrux]

i HAVE A 93 AND ON THE DOOR STICKER IT SAID 235/70/R15 I JUST TOOK OFF MY 32'S BECUZ I DRIVE OVER 80 MILES A DAY ON THE HIGHWAY AND I HAD THE SAME PROB ONCE I HIT60-70 HIT WAS A RUFF RIDE ON M/T TIRES BUT IT'S A LIL DIFF AT FIRST A MUCH SMOTHER RIDE ....

 

[Krafty]

it all depends on the type of tread your tire has, I had 33 that were almost bald but the ran smooth from 50 to 60mph and 65 mph + they had a very aggressive tread and cause alot of the road noise and what not. since I dind't have the money for a new set this winter I put on my old 31x 10.5 x 15's and they are quieter that the 33's cause they are a smaller tread width and not so angry lookin. but they are the same anything over 50 mph and they are perfectly smooth.

if your tires are causing a bad ride at 70- 80 mph check the speed rating, and maybe you wore them out a little too much. or maybe you just have a bad set of tires for some reason.

also you can get a 31 33 and 35 inch tall tires that have the smooth road running tread and not the m/s tires, I think its bfg or something like that. those are what my next set of 35's are going to be.

 

[WPW Bronco]

Hey, I'm going to be doing a lot of highway driving these next few months and my Alts are almost bald and out of shape (meaning that the entire truck shakes when I exceed speeds of 55-65 mph). The tires are all balanced and the truck has been aligned 3 times.
Anyways, I have a set of almost brand new 235/75 R15 Michelin tires. I have 31x10.50 on the truck right now. What could I expect if I put those 235 tires onto the bronco?

(I'm doing this in an effort to save money because its running low)

Any pros or cons would help

Thanks.

Alright, here's the info you need from one who has done the same. The 92-96 Bronc's came stock with 235/75R15's, which equates to a 29x9.50. Most people who have a lick of sense upgrade to the 31x10.50's because the look less dorky by filling in the wheel well some more and there are better tread options for off-road. The speed change goin up is 2 mph higher (25 mph on the speedo is actually 27 mph on the road) and the mileage goes down 1/10th of a mile (1.0 mile on the odometer is 0.9 miles on the road). So going from the 31x10.50's down to 235/75R15's will actually bring your reading back into factory ranges unless you have had the speedo recalibrated, which hardly anyone does for 2" of tire size.

As far as the shaking at higher rpm's, had a set of older goodyear's that did that to me adn when they were taken off at the tire shop, it was apparent looking inside the carcass that one of the belts was about to have puppies, so if you are doing highway driving, get those off ASAP! As far as the tires being balanced, if the belt is shifting like it probably is, they weight has shifted from when they were balanced with the tire heating and cooling on the road.

There's my two pennies.

 

[shift1313]

i put 235/75s on my f150 when my 32s ran out. how could i resist at $58/tire for bfs road tire. the trucks do look a little funny with that size tire but money talks