Bigger tires questions


hunter01
11-02-2004, 03:20 AM
My 02 Blazer came factory equipped with size 235/70/R15 tires. I just switched to 235/75/R15 tires without any interference problems. From my own experience the slightly bigger diameter seems to have several advantages.
1. Cheaper tires
2. Better highway gas mileage
3. Higher under vehicle clearance
4. Better over pot holes
It also seems to have a tighter turning radius.

I,m interested in hearing if anyone knows of any other advantages or disadvantages in using the bigger tires.

Again from personal experience I made the same switch on my 91 Blazer and It seemed as if I went through idler arms and upper ball joints faster than I should have. (Maybe it's because of the bone jarring streets of NYC?)

My question is, do the bigger wheels put greater stresses on front-end and suspension components? Did GM allow for this in their design?
Also what is the procedure for recalibrating my speedometer, is it a spedo gear change or can this be done using the computer?

And lastly how fast am I going when my speedometer says 70mph.?

busa_4
11-02-2004, 10:15 AM
alright! when you say bigger tires are you referring to a bigger profile tire or a bigger tire with rim. for example: your factory tires are 235/70r15 are you going to change your tire to a bigger profile 235/80r15 or are you going to put a bigger rim and tire package 235/40r18. if you purchase a tire with a bigger side wall/profile it will of course be cheaper and smotther over bumps. a lower profile tire will give you better performance around corners but the ride will be harsher. of course this varies with tire design and compound. the bigger tire and rim you go with will effect braking ability as your trying to stop a heavier rotating mass. also it will take more power to turn the big tires and you will lose fuel economy. the wheel ofset is another factor as the more the offset the farther the rim sticks out from the fender well. this will cause pre-wear on your suspension ball joints, tie rods, etc because of more strain. if you change the over all circumference of your factory tires then you will need a power programmer so you can reflash the ecm with the new tire circumference. i thing there around 300-500.00. if you raise the circumference your speedometer will be reading lower than your actually going and vise versa for smaller circumference tires.

hunter01
11-02-2004, 12:16 PM
I'm just changing the profile on the tire, not changing the wheel dia. Thanks for all the info. I was able to unbolt my factory aluminum wheels (metal studded snow tires)from my 91
blazer and put them on my 02 Blazer. Same diameter same offset, larger profile.
My 91 blazer got a set of steel rims,my baldest tires and a set of mud chains. I've retired it to my land in the mountains where I use it to drag trees and pull stumps. 240k and going strong.

busa_4
11-02-2004, 02:48 PM
If The Circumference Is Different Your Speedo Will Still Be Off. Reguardless If You Change The Profile Or The Rim Size You Need To Keep The Same Circumference So You Wont Have To Reprogramm The Ecm For Tire Sizes.

BlazerLT
11-02-2004, 03:30 PM
My 02 Blazer came factory equipped with size 235/70/R15 tires. I just switched to 235/75/R15 tires without any interference problems. From my own experience the slightly bigger diameter seems to have several advantages.
1. Cheaper tires
2. Better highway gas mileage
3. Higher under vehicle clearance
4. Better over pot holes
It also seems to have a tighter turning radius.

I,m interested in hearing if anyone knows of any other advantages or disadvantages in using the bigger tires.

Again from personal experience I made the same switch on my 91 Blazer and It seemed as if I went through idler arms and upper ball joints faster than I should have. (Maybe it's because of the bone jarring streets of NYC?)

My question is, do the bigger wheels put greater stresses on front-end and suspension components? Did GM allow for this in their design?
Also what is the procedure for recalibrating my speedometer, is it a spedo gear change or can this be done using the computer?

And lastly how fast am I going when my speedometer says 70mph.?

Yip, your speedo will be off by 3.3% and when your speedo is reading 60mph, you will actually be going 62mph.

Also, you odometer will be recording the improper mileage.

Other than that, there will be no other differene other than maybe the cheaper tire price due to increased availability.

The rest of the advantages you stated are wrong.

83XFIRE
11-02-2004, 03:35 PM
Just putting bigger tires on won't wear anything out faster because you aren't changing any suspension parts. If the tires are just wider, you shouldn't be able to turn as sharp. As for the 70 thing, find one of those cop trailors they park on the side of the road and check you speed. If it is off, you will have to go into the programming of the ecu to change it cuz you have an elec speedo. To change it by 5mm shouldn't put you off by too much, but remember that your going faster than it says. My ranger was slow by 5 at 60 with decreasing tire size 5mm (just comparison, not giving any formula or specs). You can buy programmers that you just plug in and put in your different tires size and it re-callibrates your speedo. Good luck.

BlazerLT
11-02-2004, 03:43 PM
His new tires just have a taller sidewall, the width is the same.

The local dealer can redo the tire diameter for you for really cheap.

hunter01
11-05-2004, 01:13 AM
Thanks for the info everyone, now I'll just wait for it to snow so I can put my studded tires to use.

BlazerLT
11-05-2004, 01:28 AM
You sure your state allows studded tires?

hunter01
11-05-2004, 07:20 AM
Yes from Oct 16 to may 15

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