Stephen

iTrader: (12)

16x8 16lb wheels & 245/255 tires.....
vs
17x9 24lb wheels & 275/285 tires.....

Which would be better? More footprint or less weight?

Obviously, TOO little of a footprint (like a 6" tire) would be bad, but between the 2 examples above.....?

Oh....HANDLING (like autocross), not drag racing (like wrinkle wall tires).

BMR Sales

What do you do with the car?

Stephen

iTrader: (12)

Its a street car, but I live out in the hill country & enjoy some of our twisty lakeside roads.

Might toy with autocross & not really interested in drag racing. Might for sh*ts & giggles once, but that's it.

RedHawkLB9

i would think the wider the better...i mean the extra weight is already being moved

BMR Sales

If youre not trying to shave 1/10ths of a second of track times (road or drag) then just get the wider heavier wheels. More grip with more tire for spirited street driving and the occasional track run will be just fine!

Lonnie P

The 275/40-17's were one of the best things I did to my car. 285's are a little big for a 9" wheel.

Stephen

iTrader: (12)

Nah....I have 285s on them (17 x 9) right now & see no fitment problems. 10 mm isn't gonna make or break a good fit.

I've just been wondering if I should hang in to my stock gold crosslaces or sell them. I think I'm just gonna sell them. I need the $$ for more mods.

91_5.7_TPI

iTrader: (2)

Most prefer the added foot print over the added weight. My 17s weight like 21lbs while my 16s are somewhere between 17 and 19. Just try to find some lighter 17s. GM wheels (real, GMs not repros) are lighter than aftermarket in most cases. Unless you want to spend it out the rear on some Volks, CCWs, or the like (think 16x8 or less weight for 17x9s). Hope this helps.

Stephen

iTrader: (12)

It was more a question of curiosity than "What do do..."

I'll be keeping my Snypers, no doubt there. In fact, I'll be adding even more weight on the rear 2, before long.

32 lbs over all, isn't enough to concern me.

racing geek

iTrader: (5)

Your car is growing/evolving and it needs new shoes. I wish I could afford a set of 17x9.5 snypers... Oh well.

Mike

Guest

Its not all about size. Qualiy makes up a good part of it.

Why? You can take a good quality 245/50-16 and have better lateral AND straightline grip and braking than you could on a less expensive 275/40-17.

Suspension makes up a good part of it

Why? Because you can have alot of roll due to a softer inferior quality 245/50-16 sidewall colapsing (NOTE: Different tire brands and styles have different sidewall spring rates) than an inferior quality 275/40-17.......and so on.

Things have to be married to what you are doing. Alot of people also may have a tire on a car without a good alignment and proper caster settings to get adequate camber gain.

General rule of thumb- ask yourself this- Have I really had alot of traction loss driving today, or is it just an occational thing that happens a few times a year? If its the later, keep what you have. You will get better gas mileage out of narrower tires and actually drive nicer. Now if safety and grip is a major concern, then spend as much as you can on GREAT QUALITY tires and shocks, until then, nothing else matters on size.

Dean

Guest

Let me just add that most people tend to "feel" much better by simply adding a lower profile tire to their vehicle because it raises the sidewall springrate over the stock wheels and tires they had on there.

A car will handle better with a tire sidewall that is designed for the suspension geometry which is generally a larger sidewall design combined with a basically stiffer (adjusted travel range) and better dampered (meaning shocks) suspension and keeping a slightly stiffer than stock sidewall tire that has a larger aspect ratio and a much more forgiving feel and predictavility.

In other words, I will take a properly built suspension and 50 series tire over a stock suspension 30 series tire any day of the week. I will also take the first above over the 30 series on a built suspension hat senrio will give you no ability to set the car on edge- when it goes....no warning, it goes- and you are spinning dounuts.

91_5.7_TPI

iTrader: (2)

While we're on this track, I've noticed my car 'feels' better when cornering hard on the stock 16s with 245/50R16 Bridgestone G009s than with the BFGoodrich g-Force Sports 275/40R17s. But, I've punished the car enough to know the 17s will stick harder and longer than the 16s, but I just feel more secure and at ease with the car on the 16s. But, the G009s deform quiet a bit when I try to put the car through the paces like I can with the g-Force Sports. Can anyone help me understand this?

Guest

You will get more mechanical grip with more sidewall.

As the tire sets on edge, the transition point from longitudinal to lateral grip is reduced in a lower aspect tire. THUS, the transition point from max grip to slip is reduced as well when that point is breached.

When is it breached, not just when overdriving, you may have a car set perfectly into a corner but then hit just a tad little bump 5/8 of the way through that corner and the sidewall will deflect just a smiggin more to deflect into a slip point and you are gone. I larger sidewall pecentage wise will absord a little more and not gain and then loose mechanical grip as spontaniously.......i.e.- more predictable.

All you need is to make sure that tire is set up with the proper cmaber and caster gains to insure the footprint is flat at max lateral grip and desired body roll. All cars roll differently (And remember, that includes the inside radius suspension angles also with there grip and roll footprints) and by changing tire profiles alone can mess up engineer designed footprints. There is a whole lot of mathimatics that goes into this and a whole lot of testing- then... there is a whole different road temp and grip coifficient in the winter months than the summer months.... and so on. This sh*t never ends. Thts why preictablity will win on a strret car that sees unpredictable enviroments.

edit: the best tool for any of this is fender well pyrometers giving instantanously recorded tire temps on the fly. You can see where the tire temps accross the tire read on the straightaway and then also in the turn. Whne I read them after the fact I am guessing at a happy medium sometimes. A right front (RF) tire that comes in at lets say 245 242 240 could be that on straight and corner, or it could be 250 260 270 on the straight and 275 265 255 on the corner and I am getting to it when it slightly cools already. Generally on a racecar and specific track, you get to know the chassis type characteristics as well as the track it is on. General rule is to go about 10* hotter on the outer edge when taking static readings.

91_5.7_TPI

iTrader: (2)

So I'd need a different allignment for the 17s vs the 16s to maximize my grip for each? Would the larger wheels need more negative camber than the smaller ones? I have the caster maxxed as far as I know, and my camber is set to -.5-.75 if I recall correctly. It's a DD, so I don't want to kill tires too much. The car feels 'right' with this allignment on the 16s, so I'm assuming that an increase would improve the feel with the 17s? I haven't pushed the car enough to loose grip since I installed my KONIs. Partially because I've lost my nerve on the street and partially due to the HUGE advantage of the KONIs compared to the Monroes... I'm not looking to get the absolute most from the car as it's a street car and I have to compromise, but I would like a more confident feel from my stickier wheels/tires....if that makes sense.

Guest

larger SIDEWALLS usually need more negative camber.

Caster has alot to do with driver feel and how you have the rear set in balance- These are personal feelings that two drivers could get in the same car and one would like, the other would not. There is no right or wrong, its driver preference.

What I like? Is mild negative camber and massive caster so when you have to introduce more wheel the tire gets the bite it needs without rolling over. I also like a very firm spring and a 50 series sidewall ( a good quality sidewall. Note that my car change feel drastically going from the Goodyear GS-D3 to the crappy KDW. I used to run BFG Comp TAs on this car and loved them. They were much beter than the just discontinued BFG KDW. I put some BFG G-force sport's on my girlfriends 320 Mercedes sport and they seem better than the KDW were, but those are also a 225/40-18 where the KDW were a 245/50-16

zride91

How about the narrower 16's upfront with the wider 17's in back? I would think the wider footprint would be beneficial in the back for traction. But isn't going much larger than the stock 8 or 8.5 in front counter productive, even in the road course application, the 8.5" tires were the reason for the OE wonderbar afterall, wasn't it?

I'm just thinking out loud, so don't destroy me too badly if I am out of line...

Vettes have the bigger, wider wheels in front, don't they?

paul_huryk

Third gen cars respond exceptionally well to a wider tire. That is one reason why the factory offered a 245-50-16 tire on the IROC (vs. 215-66-15 on Z28). It also allows a 275-40-17 tire to work wonders too.

Of course tire design does make a difference: a 275-40-17 all season snow won't outperform an ultra high performance 245-50-16 tire.

91_5.7_TPI

iTrader: (2)

I'll have to get my allignment guy to mark off different points on the allignment with a sharpie. I'll play around with the allignment this summer and see what I can get. My caster is ~4.5 I think. What do you mean about having the rears in balance? They are the same size wheels/tires as the front.

No, the Vette's front wheels are either the same size (in the case of almost everything up to the C5) or larger in the rear (in the C5s- C6s).

alanq64

i'm wanting to get 17's for my 86 t/a. could you give me the specs on yours? do you have 17x9's front and rear? what are the offsets for the front and rear?

Stephen

iTrader: (12)

I have 17" x 9" with 4.5" backspacing, on all 4 corners.

Room to go wider in the rear, but 4.5" is the max backspacing on the front, with 17"s. 4.75" & it would be hitting the tie rod end. As it is...I'm CLOSE! But safe.

alanq64

got it.. 17x9 w/ 4.5" up front. anyone have specs for the rear. i'm wanting to go the widest i can. i don't want any rubbing but i would like the widest possible for the rear.

Stephen

iTrader: (12)

The question is.....How much inner panel modding are you willing to do to fit a wide tire?

I'm fixing to fit 315s, possibly 335s, depending on what my measurements reveal on Sunday.

alanq64

i'm willing to roll the fender lip but nothing like mini tubs... i also don't want any rubbing if i have passengers in the back seat. 315's are prob the widest i would want to go.

Stephen

iTrader: (12)

315s seem to fit & need mimimal BFH work to the inner fender, 335s a little more.

But.....

It depends on what backspacing you go with....
how far (if any) you are willing to let to stick out....
the amount of inner fender mods you are willing to do....
and the amount of lowering (if any) your car has.

alanq64

just read the thread of fitting the 315's.

stock stance for now. will lower 1 to 1.5 later
i also want them to fit in the fenderwells. i definately don't want the tires scrubbing if i decide to take a drive on a country road.

RED_DRAGON_85

So what you seem to be saying is run slightly negative camber and lots of caster if you have big sidewalls? This is a street car with stock sized tires and wheels

Flip 2

iTrader: (1)

Stephen-
One other advantage of 17s is the better brakes you can use.

TPI-
You gotta be setup for the 16s. I bet you can find a setup where the 17s (and bigger tires) feel secure. One thing, 275s up front may wander more than 245s (16 0r 17).

Vetruck-
How much caster are you talking about??? Since it is you, I'm expecting an interesting number. I've never seen you be half-hearted.
PS- how's the West Coast short track scene doing with the down turn?

91_5.7_TPI

iTrader: (2)

I know the 275s wander more than the 245s. I've been running them for two or three summers now. I was more curious about why the car felt less confident with more grip. I'm gonna play with the allignement more/

Lonnie P

Here is what i can provide....

I run a 17x9 w/ a 6"BS & a 9/16" spacer on the front. They tuck rather well & barely clear the tie rod, but I've driven them for 3 years this way.

Recently added C4HD front brakes which allowed me to reduce the spacer to an approx 1/8 spacer. (using the factory rear spacer)

I went from a 16" G-force to a 17" Nitto 555 & felt an improvement. According to the above comments it should have worsened with a cheaper lower profile tire.

This is a street car, but it is pushed hard enough to test everything from understeer to throttle induced oversteer. The 17's gave me a better feel & I could better predict when it was about to come unglued, plus I picked up corner speed.

Now with a set of 800/150's & Konis & Strano rear bar, it fascinates me to the point that I want to see how I can improve it more. It is only slightly loose to the point that it will slide all 4 tires with just slightly more rotation of the rear.

Went to a 1/2" spacer on the rear tires & it seemed to slightly help it out.

Better tires may make it understeer again, but I have yet to test new tires.
Also since I drive this car in the summer, I do not want to run race tires on the street, nor do I want to buy multiple sets per year.

I am in no way a suspension expert, but most of my experimentation has been successful.

I'm following this thread to see what else the experts have to say.

91_5.7_TPI

iTrader: (2)

I picked up speed in sustained corners with the 17s, and even in switch backs, but I never feel as confident on them at the same speed as I would with 16s. Might be (mentally at least) where I'm more used to the behavior of the 16s as compared to the 17s.

Stephen

iTrader: (12)

Wait a sec.....

I have 17" x 9" with 4 1/2" bs on all 4 corners. Doing the math, your effective bs is 5 7/16". That would be IMPOSSIBLE on mine....Yet somehow, YOU did it?

I can't even fit an open ended wrench between the tie rod & the rim. If I had 4 3/4" I would be IN tie tie rod. 5 7/16" & I would be on the other side, THROUGH the tie rod end.

So...I'm ROYALLY CONFUSED by yours.....Please tell....HOW?

Flip 2

iTrader: (1)

TPI-
See if toe and caster can bring back your feel.
Personnally, I'm going to go 255/285 or 245/275 when I put my C5 rims on.
That said, 275s should not run away with your feel. Lots are happy with their setup.
Maybe a rack where you get toe for each wheel would help. Is one way different from the other, and the wide tires are exaggerating.... Years ago, on a Monza I had, too wide a wheel spacer made it steer funny.
Good luck, let us know.

Stephen

iTrader: (12)

The road has a big deal to do with it too.

In Austin area (Williamson & Travis Counties) my car feels PERFECT.

Once I cross over into Burnet County (NW of Austin where I live) it is like I'm driving on a road of marbles. Making steering corrections left & right.....pulls left & right.

With the 275s, that is. With the 245/16s, I didn't notice ANY steering problems out here.

Lonnie P

Stephen,
You are using math to determine backspace based on offest.... Place a straight edge across the wheel & measure to where it touches the mounting face on the back side of the wheel. This is the correct way to measure backspace which takes in to account the bead thickness as well.

Depending on the wheel manufacture & the inner shape/dimension on the actual wheel it can vary a little depending on how sharp the radius is on the inner edge near the tie rod. Many run a 5.5" BS wheel without problem.

This is the wheel (AR Rebel 17x9 24mm offset) which has a 5.94" BS... you can verify it on American Racings website.

Stephen

iTrader: (12)

I understand how YOU are measuring it, & the generally ACCEPTED way of your measuring method. But it not the CORRECT way to measure. Just easier for people to understand.

By that method, which is not the TRUE method (just easier for people to understand) the bead seat is not counted. Just tire seat to seat surface. INSIDE the beads.

THIS is the TRUE wheel width. It is just easier for people to understand surface to surface.

Coker Tire


By your account, my 17" x 9" are 10" wide,surface to surface. I think the manufacturer knows best. But even with your method, that would only equal a 5" bs. 5.5" would NEVER fit.

Lonnie P

Stephen,
I guess you did not look at the American racing website..... it shows 5.94" BS. I agree the manufacturer knows best & my measurement agrees with theirs. They are not all wrong. Take a look if you do not believe me.

http://asp.americanracing.com/wheels...ted&section=AR

This link is in the sticky above in this forum
http://www.rsracing.com/tech-wheel.html#backspace
Check it out

Here is what the wheel manufacturers & how various others say to measure..... just the way I did it.

http://www.bogartracingwheels.com/diagram1.gif

http://centerlinewheels.com/faq.php#measure

http://custom-wheels-n-rims.com/images/DIAGRAM1.JPG

http://www.summitracing.com/streetan...spacechart.htm

You measure backspace to see how it clears the suspension components & use offset to see how the tire relates to the position in the fender.

Also there are probably 50 posts on this site saying how 5.5" BS works on our cars. They are not all wrong.

Please review the above before you post again... your remarks are going to confuse people. What you should care about is the measurement like I did it.... this is what makes the tie rod hit. The thickness of the wheel effects this measurement & causes interference. Offset will not tell you this, only backspace.

Stephen

iTrader: (12)

No....I AM NOT MISLEADING PEOPLE! YOU ARE!!!!!

For YEARS & YEARS & YEARS, the measurement has been at the TIRE BEAD SEAT. As I showed in the site link. I guess YOU did not look? I even supplied the pic, for those too lazy & stubborn to click on links themselves.

The wheel manufacturers, as of late, have given up on EDUCATING people, such as yourself, which regards to WHERE to measure backspacing.

It is just EASIER to explain..."Take a ruler...Measure..,There's your backspacing.", to people like yourself. Instead of EXPLAINING to them, that the TRUE place to measure, is at the TIRE SEAT SURFACE.

ROH themselves, my rim manufacturer, will tell you (i have personally emailed them to ask, and your welcome to also)...The ORIGINAL (not the ones that fit 4th gens) 17" x 9" Snypers for 3rd gens (that did not require spacer/adapters) are a 4.5" backspacing/0mm offset. I guess you are saying they don't know how to make their own wheels?

Attached you will see...Even by YOUR measuring method (which is wrong), they are exactly 5", to the edge. I don't have 1/2" between the edge & the toe rod. IT WOULD NOT FIT.

Before you suggest that my measurement clearly shows it to be above the 5" mark, notice that the #s are just to the left, or below in this orientation, on the ruler. The 5" line is RIGHT AT THE cross bar measuring point, which is on the edge of the rim, which is you you suggest the measurement be taken at.

I can explain this all day, but if you are not willing to learn the TRUTH, and are swayed by modern interpretation, then there isn't much I can do to educate you.

You know.....I'm wondering WHY I care so much about YOUR misinformation.....I guess I'm only gonna post, because I already typed all this & took pics for you....

Guest

I ran 5 left/5.5right positive caster and -0.8 camber, 1/16 toein.

Every car is different in this aspect, roll pitch in degrees, car height and cg, roll centers and roll couple, spring rates, brake bias resulting in chassis atitude as compared to no braking roll (setting the chassis, or letting it set itself)....all basically resulting in the dynamic end result of how things migrate from static readings into actual real world footprint based on the tire choice you have (that tires individual sidewall charateristic and behavior aiding in the above changes of the chassis).

What does this all mean? basically just as you would have neg camber gain if designed correctly (I will give an example- 0* camber at straightline driving, then with 2* body roll and lets say 3" front suspension travel you gain -3* giving an overall camber gain of -1* footprint aid in a corner for prevention of sidewall rolling under the footprint) you also can and genearlly do have susbsantial caster change dynamically. The shorter the strut mount distances (strut length at stagnant height) the greater the general caster gain under compression and the lesser of "caster loss" under brake dive of the chassis due to a lower cg, etc.

Beware though, too much caster will give bumpsteer pulling the tierods up and backwards trough adequate suspension travel so travel should be limited.

my car's ride height was at 24 3/4" from ground to fenderlip and I ran aprox 800lb springs on a very lightweight nosed 60*V6 car. This suspension never grounded out yet artculated very well through a total of 1.5" max travel- most cars have about 4" strut shaft travel.
http://www.cardomain.com/member_page...0074_large.jpg

http://www.cardomain.com/member_page...0001_large.jpg

http://www.cardomain.com/member_page...0134_large.jpg

You can see up under the shiney travel section of the strut shaft polished where suspension travel exists in only about 1" normal and 1 1/2" extreme travel. This car is lightweight and limited on body movement.
http://www.cardomain.com/member_page...0116_large.jpg

Guest

No, you are.

What link? The one to Coker tire? That says how to measure rim width. They have another page on how to measure backspacing, did you read it?

RED_DRAGON_85

lol
he's right
not trying to start a fight here guys, but backspacing is measured from the outermost point to the mounting point...
thats it
pretty simple.
then again, guess i am one of those "simple minded" people who only use this method cause i am less intelligent...

Stephen

iTrader: (12)

I give up.....

Ya'll continue to measure the way wheel manufacturers are doing NOW. Not the way it STARTED.

They gave up explaining it, because of people like ya'll.

I guess I'll hafta start doing it the "simple way", to conform to the NEW method.

Sigh.......

Stephen

iTrader: (12)

No...This really bugs me.....

How can my WHEEL MANUFACTURER, the people who MADE MY WHEEL, call my wheels a 4.5" bs/0mm offset, on a 9" wheel.

By YA'LLs measurements, the WHEEL MANUFACTURER is wrong (do ya'll know more than them?) & the 9" wheels have 5" backspacing, yet 0mm offset (which would equal 4.5")!

Explain THAT to me.....

Guest

Because everyone except apparently ROH will tell you that is not how its measured. Ask anyone. Call Boyd, Budnik, Centerline, American Racing, Cragar, Weld, etc etc. So they're all wrong and you and ROH are right? I think not.

Tell you what, I'll go ask the guy down the street that worked for Boyd (was #2 in charge) that makes his own wheels now how to measure it. That make you happy?

Here's the title of the link you put up
"How do I measure my rim width?"
Look how they say to measure backspace
http://resources.coker.com/wheel-tec...backspace.html

Why have both a backspace dimension and offset dimension if you can use simple math to get one from the other? The only useful purpose of knowing the backspace is to know where the absolute back of the wheel falls for clearance purposes. The distance from the bead to the edge of the rim varies from one rim to the other, so the only way to know is with the measurement that they call... backspace. I'll bet you ROH cant tell you what the distance is from the bead to the edge of the rim and its not disclosed on anything they give you when you purchase. Your method, you have no clue where it is, and its easily calculated from offset and width so its completely worthless and doesnt need to be known.

Stephen

iTrader: (12)

I can't believe how MY THREAD has degraded ito this STUPID "discussion".

It is a FACT, that measuring the way YA'LL want to measure wheels, has CHANGED in modern times. How many times do I have to repeat that?

It's people like me (and apparently ROH) are the ones not wanting to "go with the flow" and change to everybody else's new way of measuring....Whatever....I'll just measure thing for ya'll, so that I don't hafta explain the TRUTH anymore............

So yeah...My 9" wide wheels have 5" of backspacing, yet a 0mm offset......

Flip 2

iTrader: (1)

Vee-
Thanks.
Veddy cool paint job, BTW.
Phil

toxik IROC

iTrader: (12)

my 9'' wheel has a 47.9mm

this is how i mease Backspacing with your back up against the wheel and then count how many toes you have and then Stand on your LEFT foot, not your right....Stick your tongue out, and sing the Pledge of Allegiance...Otherwise it won't work. thats your back spacing

alanq64

you said that you have 285's on the rear with 17x9's. i'm wanting to try and keep the wheels as centered as possible and since the rims i'm looking at have various offsets, would it be better to have more bs? also, i've decided to run 255's on the front. do i need to go down in width for the front? I can figure out the bs (and i am refering to backspace )ha, from the info you have already given me... i just realized that you can write some pretty long sentences that add up to not a whole lot when you're sleep deprived.ha

Stephen

iTrader: (12)

Centered where? In the wheel well?

alanq64

yeah, i guess i forgot to say that ha..... i hate the look of tires not centered in the wheelwells...