Silverado's Silverado

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Re: Silverado's Silverado

Post by Silverado »

Well, this morning I had a sudden hungover urge to get up early and put those tires and wheels on that I bought way back. I took off my front 235's and back 255's and put 265's all around. I love the new(er) rims.

When I was driving to the gas station to pump up the tires, it was like a rock hit my stomach because the steering was all over the place there was lots of shaking. When I realized it was because the front left was at 15psi and the right was at 35psi, I felt better.
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Re: Silverado's Silverado

Post by theholycow »

Do you have a 265/70R16 for the spare?

It's odd that your truck had different-diameter front/rear tires. I doubt it came from the factory with "front 235/70/R16's and back 255/70/R16's". You can check the door jamb label or your RPO codes (there's a label in your glovebox and a decoder at http://lonestarthunder.com/m_rpo.php ).

255/70R16 is 1.1" taller than 235/70R16 and .4" shorter than stock which was probably 245/75R16.

265/70R16 is .1" taller than stock, .5" taller than the rears you had, and 1.6" taller than the fronts you had.

I've also got a set of 265/70R16 tires to put on, but they're not on wheels so I can't just bolt 'em on like you did.
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Re: Silverado's Silverado

Post by ElectroGhandi »

theholycow wrote:It's odd that your truck had different-diameter front/rear tires.
The DeLorean did that.
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Re: Silverado's Silverado

Post by theholycow »

ElectroGhandi wrote:The DeLorean did that.
The DeLorean did that to his truck?

It used to be common on trucks and muscle cars, but it's quite rare on modern vehicles. Even the 2010 Camaro comes with same-diameter tires all the way around (though you can get it with wider tires on the rear, the diameter is the same). If nothing else it's because of ABS.
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Re: Silverado's Silverado

Post by Silverado »

Well, I've got not idea what you're talking about with the tire heights, but if that is true that may be why the back end looked a little propped up.

I'm pretty sure it came out of the factory on 235's but then the last owner had 255's and then the dealership put 235's on the front. As of now the 235's have 10mm of tread and the 255's have 7mm's of tread. I'm pretty sure the 265's have between 6-8mm which is ok because I was looking for the wheels anyways.

Corvette's even have different wheels in the back maybe an inch difference.

After I burn through all of the tires I have now (i'm going to get the 235's and 255's remounted and balanced on the alloys i have now when the 265's are bad. The dealership gave me a voucher for a free mounting and balancing because of the non-new tires they sold me), I am going to buy a full set of 4. Probably 235's again.
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Re: Silverado's Silverado

Post by theholycow »

What does the label in your door jamb say for original tire size? I suppose it might have come with 235/70-16.

Just calling them "235", "255", or "265" only specifies width. You have to use the whole thing to determine actual diameter, because whoever created the sizing system was on crack. The middle number is sidewall height measured as a percentage of width...

Edit: Has your ABS seemed good, or has it seemed excessively sensitive and/or insensitive?
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Re: Silverado's Silverado

Post by LHOswald »

to me different tires sizes on the front\back seems stupid. you would never be able to rotate your tires
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Re: Silverado's Silverado

Post by ElectroGhandi »

The reason DMC did it for the DeLorean was for weight balance. The rear engine layout + low profile would have made the car too unbalanced without bigger rear tires.
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Re: Silverado's Silverado

Post by IMBoring25 »

I think they did it on the 'Vette because the steamrollers they decided to put on the back wouldn't steer very well.

255/45-17 Front, 285/40-17 Rear.
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Re: Silverado's Silverado

Post by Silverado »

Uhoh, the door says 235/75/16. What a wacky truck I bought.

And whoever said that fatter tires in the back is stupid is right, but that's what I've got.

So wider tires with the same sidewall ratio tend to be taller as well? Is there a link you can point me to Cowman that lists standard overall tire heights by tire widths?

and the ABS is fine. I don't do a lot of hard braking so I never really have tested it out.
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Re: Silverado's Silverado

Post by theholycow »

Silverado wrote:So wider tires with the same sidewall ratio tend to be taller as well?
Yes. Because it's merely a ratio of width, not a measurement, it changes with width. Here's some examples with round numbers:
100/100R15: 100mm wide, 100% of that in sidewall height = 100mm sidewall. Diameter is 15" + 100mm + 100mm.
100/70R15: 100mm wide, 70% of that in sidewall height = 70mm sidewall. Diameter is 15" + 70mm + 70mm.
200/75R15: 200mm wide, 75% of that in sidewall height = 150mm sidewall. Diameter is 15" + 150mm + 150mm.

I can't imagine a more crackheaded system for describing tire sizes, especially when overall diameter is so important - most modern vehicles really need the same overall diameter but differing widths don't matter.
Is there a link you can point me to Cowman that lists standard overall tire heights by tire widths?
I don't know about a list, that's a good idea though. Generally I use a tire size calculator. There's two that I like. The standard one that everyone uses is this:
http://www.miata.net/garage/tirecalc.html
It's very good, but its interface is a little clunky and it doesn't provide much info. Here's one that gives you list of other sizes and how they compare:
http://wheelsmaster.com/rt_specs.jsp
I like that one because I can put in one size and see a list of which other sizes have the same outside diameter.

Edit: If you look at a tire on tirerack.com in it's "Specs" page you'll see overall diameter for each size offered. I also just found this nice calculator: http://www.tiresizecalculator.info

Also remember, these measurements are vague and approximate; you can only expect really good consistency within one tire model, and even then if two were manufactured in different facilities they might not match. Yesterday I rolled out 5 tires all the same size spec, one new and two pairs of worn tires; I only got two that rolled out the same circumference (and they were't from one pair, they were one of each pair). I'm trying to decide how to place them on my truck without hurting my differentials...
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Re: Silverado's Silverado

Post by Silverado »

Very clear now. However, that is a stupid system.

Depending on how my gas mileage suffers with the 265 width I may go back to the 235/75/R16
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Re: Silverado's Silverado

Post by LHOswald »

your gas mileage may be better with bigger tires because you'll be able to keep a lower rev while maintaining the same amount of tire rotation.

yes?
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Re: Silverado's Silverado

Post by theholycow »

Possibly not with the V6. With the V8, definitely. They offer the V8 with 3.42, 3.73, and 4.10 rear ends; 3.73 is most common and 3.42 gets slightly better fuel economy. I don't know if they bothered to offer the V6 with 3.42.
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Re: Silverado's Silverado

Post by Silverado »

theholycow wrote:Possibly not with the V6. With the V8, definitely. They offer the V8 with 3.42, 3.73, and 4.10 rear ends; 3.73 is most common and 3.42 gets slightly better fuel economy. I don't know if they bothered to offer the V6 with 3.42.
I tried the VIN decoder to find out what it came with but that did not show up.

Lets see, my 04 chevy pdf lists that with the nv3500 tranny possible final drive ratios are:

3.08, 3.42, 3.73, 4.10



We both have 1900rpm at 65 in top gear so depending on what you have, I probably have the same. Could that be the case?
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