Question about tires sizes, changing to 20's

RZAwora

Original poster
Member
Apr 15, 2012
196
I'm looking at getting a set of the TBSS 20's to put on my '06 Envoy Denali. My truck currently has the stock 18's with 245/60/18 tires.

In speaking to a friend he said that he used some kind of tire size calculation program, and the tires I would want to put on the 20's would be 245/50/20 or 275/45/20.

He said the 245's a) would match the tires I currently have the closest b) are the same width, but would have a smaller sidewall profile c) would be the closest match d) would be the least expensive choice.

He said the 275's a) would have same profile as 245's b) are slightly bigger in width, like an inch c) would be more money d) would have more road contact. According to him I can go either or... The wheels I'm looking at are MAY03LT's and they currently have 265/50/20's, and my friend says that would not be the right size to put back on them. They need new tires anyway.

My question is to you guys who have experience with these vehicles...what tire size should be on the 20's going on my truck?
Is there going to be a speedo difference? Don't care about a mile an hour...
Any noticeable difference in ride quality, road noise, etc?
 

Boricua SS

Member
Nov 20, 2011
3,080
Ohio
typically with the TBSS wheels, they come with the Goodyear RSA's 255/50/20.. and almost ALL of us SS folks make the switch to the 275/45/20's... but the 265's do fit... i know some of the SS folks have 265's on thiers...


i cant attest to the road noise, etc... but i know i will be switching to the 275/45/20 as soon as my goodyears are worn down...
 

RZAwora

Original poster
Member
Apr 15, 2012
196
Boricua SS said:
typically with the TBSS wheels, they come with the Goodyear RSA's 255/50/20.. and almost ALL of us SS folks make the switch to the 275/45/20's... but the 265's do fit... i know some of the SS folks have 265's on thiers...


i cant attest to the road noise, etc... but i know i will be switching to the 275/45/20 as soon as my goodyears are worn down...

Why would one want a wider tire? The stock tire on my truck is 9.8" wide, the 275 would be 10.6" wide. What is the benefit? Would it throw off the traction control system? Would the 245's fit on that rim?

The dude I was talking to said the 245 is the way I should go, as it is actually the "truest" replacement. I'm confused...maybe I'll should call tirerack or something.
 

jrSS

Member
Dec 4, 2011
3,950
275 45 20 are what I ran on my envoy.
43ecd419-61f9-d329.jpg
. Didn't hardly throw speedo off at all. Maybe 1mph off.
 

Boricua SS

Member
Nov 20, 2011
3,080
Ohio
rzawora said:
Why would one want a wider tire? The stock tire on my truck is 9.8" wide, the 275 would be 10.6" wide. What is the benefit? Would it throw off the traction control system? Would the 245's fit on that rim?

The dude I was talking to said the 245 is the way I should go, as it is actually the "truest" replacement. I'm confused...maybe I'll should call tirerack or something.

well most of us with SS' race them.. so the more meat we can get to the ground IE: wider tires, the better the traction on launches etc... but overall as well, better in rain, snow, etc... The 275's are the same width as the stock 255 RSA's that come on SS wheels to begin with... Lame but true... The 255 RSA is 10.9" wide and a lets say for example purposes, a 275 yokohama Parade Spec-X tire is 10.6", which is what you stated earlier... so you'll be fine with 275's
 

Scott_mcd

Member
Jul 29, 2012
88
I'm running the 275 45 20s on my truck. Here is the difference between my stock 17s and the 20s. This is from the tire calculator.
View attachment 22375
 

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RZAwora

Original poster
Member
Apr 15, 2012
196
I appreciate everyone's input so far...I'm not trying to beat a dead horse, I promise...I'm just trying to figure out what size tires I'm going to put on.

View attachment 22378

The 245's (original & pictured right) would be 9-21/32" wide on the road, the 275's (pictured left) would be 10-53/64" wide. There is a difference of 1-11/64" width. I know I can use either tire...but WHY would I choose one or the other? Why would I want a wider tire vs a narrow one? What are the pros/cons? I'm just looking for an explanation as to why I would choose one over the other. Also, my other concern as I asked is will the wider tire affect the traction control or ABS systems?
 

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lint

Member
Dec 4, 2011
155
I have 265/50/20's om my SS rims ,one good thing about them being wider is curb rash , you don't have to worry scuffing the rims on a curb.
 

RZAwora

Original poster
Member
Apr 15, 2012
196
lint said:
I have 265/50/20's om my SS rims ,one good thing about them being wider is curb rash , you don't have to worry scuffing the rims on a curb.

Okay so +1 for avoiding curb rash...but I live in slower lower Delaware and we don't have curbs. Well we do, but only in very few areas...there's hardly any parallel parking in this area of the state. But I will keep this as a Pro 275's.

Right now I'm looking at pros & cons for 275's vs 245's:

Pro
avoid curb rash
better in sand w/ low pressure
less heat
better handling when dry surface

Con
more likely to hydroplane
worse in snow
lower fuel efficiency

That's where I'm at so far...I posted over on TBSS too to see if those guys can answer my questions...keep 'em coming guys...sell me one way or the other...
 
Dec 4, 2011
520
rzawora said:
I appreciate everyone's input so far...I'm not trying to beat a dead horse, I promise...I'm just trying to figure out what size tires I'm going to put on.

View attachment 8707View attachment 8708

The 245's (original & pictured right) would be 9-21/32" wide on the road, the 275's (pictured left) would be 10-53/64" wide. There is a difference of 1-11/64" width. I know I can use either tire...but WHY would I choose one or the other? Why would I want a wider tire vs a narrow one? What are the pros/cons? I'm just looking for an explanation as to why I would choose one over the other. Also, my other concern as I asked is will the wider tire affect the traction control or ABS systems?

Here is another web site that you can put tire sizes in and it will calculate the differences.

Tire Size Calculator - tire & wheel plus sizing

the only problem is when it comes to finding some tire sizes. I have Michelin Cross Terrains at 275 - 55 -18's on my Denali and when they wear out next spring I can only find this size in two brands, Michelin (but Cross Terrains are discontinued and I haven't read any good about their Latitude replacements) and another brand Khumo I really don't think I want either. I may just have to back to stock size and purchase a set of Cooper CTS's.
 

RZAwora

Original poster
Member
Apr 15, 2012
196
Thanks for everyone's help. Went with the 275/45R20's and I'm happy with them. Got the GMC center caps on order today, should be in later this week. Pics are in the "What did you do to your GMT today" thread. I'll post final pics here once I get the right caps on there. :thumbsup:
 

Rudeawakening

Member
Jan 25, 2012
147
Im sorry and I hope im not rude for asking a question off topic, but since theres alot of SS rim experts here I was wondering if SS rims would fit my 03 TB Lt. I have read that they will fit but do I have to do anything at all to my TB first? Or can I just yank off the stock rims I have on now and put on a set of SS rims? :confused:
 

RZAwora

Original poster
Member
Apr 15, 2012
196
Rudeawakening said:
Im sorry and I hope im not rude for asking a question off topic, but since theres alot of SS rim experts here I was wondering if SS rims would fit my 03 TB Lt. I have read that they will fit but do I have to do anything at all to my TB first? Or can I just yank off the stock rims I have on now and put on a set of SS rims? :confused:

No need to be sorry, and you aren't being rude, and this question is right on topic. :thumbsup:
Yes they will fit no problem. You are correct, all you need to do is take of the stockers and put on the SS wheels with tires. For the appropriate tire size you'll want to use a calculator. I know everybody says to just go with 275/45R20's, but from my understanding that may differ depending on what size tires are on your stock wheels. You can find a tire size calculator here for exact measuring, and you can find a reference to the appropriate conversion here. Start with the second link and put in your stock tire size, then hit search. When it pops up down bottom with tire sizes, change the "New Wheel Ratio" to 20". It will then show you the tire sizes that can be used. If you want the wider tire, look for a 265 or 275. You want a tire size that has the LEAST diameter difference. The first link allows you to put in a stock tire size and a new tire size and shows you the exact difference so you'll see the impact on speedo and such. If you have any questions or problems let us know.
 

jrSS

Member
Dec 4, 2011
3,950
Just slap em on. Here is a pic of my envoy not lowerd stock height with 275 45 20's. Hope this helps.
6b1b12e7-148d-54b2.jpg
 

RZAwora

Original poster
Member
Apr 15, 2012
196
jrSS said:
Just slap em on. Here is a pic of my envoy not lowerd stock height with 275 45 20's. Hope this helps.
6b1b12e7-148d-54b2.jpg

That looks sharp jrSS...you got rid of that Voy when you got your SS right?

You can see a pic of what they look like on my Envoy over here in the other thread. My truck has the running boards. Stock height, well except the 1" drop in the rear from air bag adjustment, just enough to level off the rear with the front and kill the rake.
 

jrSS

Member
Dec 4, 2011
3,950
Yes. I traded it in at 96k miles and they gave me 13k for it. Here it is lowered.
6b1b12e7-1931-25e0.jpg
same tires.
 

RZAwora

Original poster
Member
Apr 15, 2012
196
Rudeawakening said:
Nice :thumbsup: I cant wait to get some SS rims :salivate:

I hear you brother. They do look good... keep your eye out on eBay, Craiglist, and also tbssowners.com. They pop up every once in awhile. You can also order new factory reproductions over on tbssowners. Good luck finding a deal! I got mine from a fellow member on here, MAY03LT, for a great price. :thumbsup:
 

Rudeawakening

Member
Jan 25, 2012
147
rzawora said:
I hear you brother. They do look good... keep your eye out on eBay, Craiglist, and also tbssowners.com. They pop up every once in awhile. You can also order new factory reproductions over on tbssowners. Good luck finding a deal! I got mine from a fellow member on here, MAY03LT, for a great price. :thumbsup:

Thanks, Ill do that. For the kind of tires, well, I live around chicago, rain and snow is not uncommon, so what should I get?
 

RZAwora

Original poster
Member
Apr 15, 2012
196
Rudeawakening said:
Thanks, Ill do that. For the kind of tires, well, I live around chicago, rain and snow is not uncommon, so what should I get?

There's a bunch of options. I will say though, if you get real bad winters I'd go back to putting stockers on for the winter time. If that isn't an option due to cost, inconvenience, appearance or whatever, I'd go with an all season tire. My recommendation would be the General Grabber HTS tires. You can pick up a set of 4 for about $500 plus mounting/balancing. Should be under $600 total. Don't know if you have Sears in your area, but what I always do is find the cheapest price I can online (usually tirerack.com or similar), print it out (total with shipping) and Sears will price match it plus another 10%. Thing is, it has to be a tire they normally carry.
 

Rudeawakening

Member
Jan 25, 2012
147
rzawora said:
There's a bunch of options. I will say though, if you get real bad winters I'd go back to putting stockers on for the winter time. If that isn't an option due to cost, inconvenience, appearance or whatever, I'd go with an all season tire. My recommendation would be the General Grabber HTS tires. You can pick up a set of 4 for about $500 plus mounting/balancing. Should be under $600 total. Don't know if you have Sears in your area, but what I always do is find the cheapest price I can online (usually tirerack.com or similar), print it out (total with shipping) and Sears will price match it plus another 10%. Thing is, it has to be a tire they normally carry.

Awsome, thanks, thats really good to know :yes:
 

SAR85

Member
Jan 31, 2012
74
Rudeawakening said:
I know it will throw off my speedometer a little, but wont that mean itll throw off my odometer as well?

Yes, by the same percentage as your speed for the miles you accrue after the size change.
 

SAR85

Member
Jan 31, 2012
74
For 2006+ you can get your pcm tuned to change the tire size. For earlier years there is nothing to do that I know of.
 

RZAwora

Original poster
Member
Apr 15, 2012
196
Rudeawakening said:
What can you do to make it read right?

SAR85 is correct. For your 03 there isn't anything you can do. With my tire change from the factory 18's to the 20's I have now, my speedo is off by such a minor amount it doesn't even matter. Again, this is why you want to try and get as close as possible to the factory diameter tire.
 

jrSS

Member
Dec 4, 2011
3,950
Wheels are polished. Not chrome. Tires also look too big to fit on a stock tb. How much is he asking? It would be a good idea to set up an account on ss owners and buy a set there. Cheaper usually too..
 

RZAwora

Original poster
Member
Apr 15, 2012
196
Rudeawakening said:
20 Trailblazer SS wheels and Tires

What do you guys think of these? I think I can get $1000, the tires seem in pretty good shape. He says crome but they look like there polished aluminum.

I think that is a pretty good deal IMO. You are correct, they are polished aluminum not chrome, they have the factory finish. The things I would be concerned about is A) it says curb rash on one wheel but doesn't show a pic, it does say it's very, very minor so it probably isn't bad, you'll just have to check it out when you look at them before buying. B) It says it has Goodyear Wrangler's on there, but doesn't tell you the size...the tire size does matter as we have discussed. You'll want to make sure that they are factory spec or close. I couldn't tell in the picture what size the tires are, though they look like 275/45R20 to me. C) What year SS are these off of? The 2006 and prior had problems with the clear-coat from what I've been told, so therefore looking for a wheel from a 2007 up is best. D) Black center caps? These are not original, which leads me to believe they may have been on a different vehicle then a Trailblazer or Envoy, more the reason to verify the tire size before purchase. If it's not a good tire size for your truck then it's not a good deal because you're going to need to buy new tires anyway. You can purchase the factory center caps, they'll cost anywhere from $28-$45. I don't think the black center caps looks good at all, but that's just my opinion.

For a comparison, I paid $400 for my set of wheels, and cost me $598 for the four tires plus mounting and balancing. Therefore the total cost was $998.
 

RZAwora

Original poster
Member
Apr 15, 2012
196
Oh yeah... plus the lugs. I had to purchase the 24 lugs and that cost me another $24, but the guy at the Parts Plus cut me a deal because he knows me...it should have cost $42.
 

jrSS

Member
Dec 4, 2011
3,950
ALL years of SS's have shitty clear. Mines an 07 and they were starting to look like ass. Soooo...I dipped them.
 

jrSS

Member
Dec 4, 2011
3,950
rzawora said:
Oh yeah... plus the lugs. I had to purchase the 24 lugs and that cost me another $24, but the guy at the Parts Plus cut me a deal because he knows me...it should have cost $42.

Maybe he was just dsyelxic...I mean dyslexic.
 

RZAwora

Original poster
Member
Apr 15, 2012
196
jrSS said:
Maybe he was just dsyelxic...I mean dyslexic.

LOL. He might be! :rotfl: Actually he gave me a mechanics price instead of a cash customer price.
 

Rudeawakening

Member
Jan 25, 2012
147
Yeah, now that you mention it those tires look pretty thick. Im really clueless when it comes to rims and tires so this is all new to me. Iv read that the tires size on stock 16 inch rims is P245/70R16. What is the closest size that I can put on 20 inch SS rims that would be close to my current size? In other words, im trying to get the overall wheel size of the SS rims to match the overall size of my stock wheels so I dont see a difference or hardly any difference in on my odemeter, I hate the idea of my odometer reading more miles than I actually have.
 

SAR85

Member
Jan 31, 2012
74
I'm not sure about equivalent sizes, but you could try searching for a tire calculator online. Also, your odometer and speed will read LOWER than actual if you get larger than stock tires.
 

Rudeawakening

Member
Jan 25, 2012
147
I checked it and I used the same size tire as jrSS had on his voy. and it came out to be 0.8% difference so for every 100,000 miles its actually 800 less than my odometer so no big deal plus its actually an advantage becuase my odometer will show me having less mileage than what I actually have as SAR85 puts it. Also what size width should I use? I know someone said wider is better to take of faster but not so good on rain and snow. Since I Live around chicago snow and rain is not uncommon at all.
 

RZAwora

Original poster
Member
Apr 15, 2012
196
Rudeawakening said:
I checked it and I used the same size tire as jrSS had on his voy. and it came out to be 0.8% difference so for every 100,000 miles its actually 800 less than my odometer so no big deal plus its actually an advantage becuase my odometer will show me having less mileage than what I actually have as SAR85 puts it. Also what size width should I use? I know someone said wider is better to take of faster but not so good on rain and snow. Since I Live around chicago snow and rain is not uncommon at all.

This is going to be entirely up to you. The 275 in a 275/45R20 is the width of the tire. Just remember wide tires tend to "float" on deep snow, and the tread lugs never have a chance to "dig" through to the road surface to gain traction. Narrow tires are a better option in deep snow. The tire acts similarly to a knife cutting through butter; the blade works best when using the narrow edge to push through the butter rather than the wide flat side of the blade. This is because the weight distribution on a narrow tire is displace among a smaller area, whereas the wider tire the weight is distributed through a larger area. The theory here, is that the more narrow the tire, the better chance it has of being pushed down into the snow to get a better grip and "dig" through the snow. I don't know how much a difference it really makes though going from a 245 to a 275. If you're looking to stay with the same width as the factory tire, you could go with a 245/50R20, which is actually closer to the factory spec coming in at +0.48%.
 

Rudeawakening

Member
Jan 25, 2012
147
RZAwora said:
This is going to be entirely up to you. The 275 in a 275/45R20 is the width of the tire. Just remember wide tires tend to "float" on deep snow, and the tread lugs never have a chance to "dig" through to the road surface to gain traction. Narrow tires are a better option in deep snow. The tire acts similarly to a knife cutting through butter; the blade works best when using the narrow edge to push through the butter rather than the wide flat side of the blade. This is because the weight distribution on a narrow tire is displace among a smaller area, whereas the wider tire the weight is distributed through a larger area. The theory here, is that the more narrow the tire, the better chance it has of being pushed down into the snow to get a better grip and "dig" through the snow. I don't know how much a difference it really makes though going from a 245 to a 275. If you're looking to stay with the same width as the factory tire, you could go with a 245/50R20, which is actually closer to the factory spec coming in at +0.48%.

Yeah, thats what im pretty much looking to do. The factory tends to be pretty much even which is what I need. Something decent on snow and and water but not as much where itll affect hp or mpg. Iv been looking up rims and i would see some that would say 20x8 or 20x9 ect, Im assuming that measn 20 inch tall and 8 inch or 9 inch wide. What is the size of the factory ones?
 

RZAwora

Original poster
Member
Apr 15, 2012
196
Yes, the 8 or 9 is the width of the wheel in inches. The 275 or 245 is the width of the tire in millimeters. I believe the factory wheels are 8" but I'm not 100% on that. You must also factor in the offset and lug pattern when dealing with aftermarket rims so you should probably consult with a shop or something before purchasing any wheels.
 

Rudeawakening

Member
Jan 25, 2012
147
RZAwora said:
Yes, the 8 or 9 is the width of the wheel in inches. The 275 or 245 is the width of the tire in millimeters. I believe the factory wheels are 8" but I'm not 100% on that. You must also factor in the offset and lug pattern when dealing with aftermarket rims so you should probably consult with a shop or something before purchasing any wheels.

Wow, im glad im looking this stuff up I could of bought After market rims and be screwd. Im just gonna stick with OEM rims to play it safe, plus I dont know how good aftermarket stuff is, there generally cheaper for a reason, that reason being on lesser quality.
 

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