91L98Z28

do all of the brake upgrades (1LE, LS1, etc.) result in pushing the front wheels out? Are there any that do not?

I'm interested in the LS1 upgrade, but not if it pushes out the wheels 3/10" of an inch as I have read. it seems that other upgrades are even worse.

Boosted_SS

LOL you act like 3/10" is gonna make half the tire stick out from under your fender

91L98Z28

*shrugs*

I don't want the look of the tires sticking out any further, I don't want the increase in scrub radius. Having driven a wide-tired car before and after a similiar increase in scrub radius, I don't care to do it again if it's avoidable.

anyone else?

1991camcamaro

iTrader: (1)

its 0.300 of a inch with bigbrakeupgrade. with is just a little more than 1/4 inch, its not that noticeable with stock wheels.
i have 4th gen wheels ZR1s GM factory 17x9, i was using 2 inch spacers on the front before this LS1 brake mod, and they fit inside the fenders.

but now i had to order a 1.75" inch spacer to counter for this outward movement, b/c i am like you and dont want a wheels sticking out from the fenders. so let me tell you i had to do some homework to find someone who can make me a 5 3/4 to 5 3/4. 1.75"inchs and custom spacers cost is $$$$ MORE.
once i get the new spacers i can go and put my factory 16x8s on and show what its going to look like.

Boosted_SS

over 3/10" this is retarded

91L98Z28

What exactly is your malfunction, anyways?

If you have nothing useful to add, go crap in someone elses' thread. I'm trying to get some useful information here.

DigitalMonarch0

Were you running the Skulte wheel adapters for your ZR1s or were they just spacers? I have adapters on my stock rotors now to make my ZR1s fit and I'm wondering how much of a difference installing my LS1 brakes is going to make.

Jetmeck

iTrader: (3)

If you are running GTA wheels you swap front to rear and essentially offset the offset...since the front and rear wheels have different backspacing. This is my plan.

Boosted_SS

could ask you the same question. it's 3/10's of an inch...NO ONE will ever notice and you are acting like it's a friggin nuclear emergency!

DigitalMonarch0

It's not up to you to decide what's important to him. If you think that show cars don't worry about the 1/4" gaps between their doors, or the correct spacing of the wheels, then you really don't understand this hobby at all. Those fractions of inches can be the difference between a trophy and no trophy.

Even if he's not into showing the car, then maybe the difference just bothers HIM. It is HIS car, not yours.

Either offer some useful information, or don't post. It's easy.

WillSpeedy

I guess it's due to the thicker rotor right? I wasn't aware it changed at all. Good to know as I plan to do the swap in the next year or 2.

Gladstoneiroc

iTrader: (1)

A final question, does the factory 1le push the wheels out at all? I know with my ls1 setup that can now rotate the wheels without dismount/mount. This is very nice, except I can not run weights on the inside of the wheel without contact to the tie rod.

91L98Z28

yes, 1LE's push the wheels out as well, by about the same amount (slightly more but roughly the same).

From what Dean has posted in the past, it's about a 10% increase in scrub radius.

bingo

iTrader: (2)

When I did my 1LE swap it pushed my wheels out about 1/4 inch. I was under the impression this was normal. I didn't notice any difference in the tire scrubbing until I lowered it 2".

wgripp

iTrader: (1)

What negative effects does widening the wheelbase have? Does it decrease handing, increase tire rubbing, etc?

I'm just wondering,

Thanks!
Bill

bingo

iTrader: (2)

I would think widening the wheel track would help stability.

Boosted_SS

body gap yes i'd say worry about the 3/10" but we are talking about the wheels being pushed out 3/10" that no one will ever notice unless you point it out and even then they would probably be like whatever.....in case you didn't know different tires can also cause your tires to stick out farther as well. not all 245/50/16 tires are the same tread width check it out. they may be close (within 3/10") but not exactly the same.

Orr89RocZ

iTrader: (20)

yeah .300 inch isnt that much at all, especially considering the great benefits of the bigger brakes. In fact, .3" is about as long as the typed word inch on your screen that your reading right now.

if .3" means more to you than braking ability, then i'd say your alittle crazy. j/k haha stock brakes really are not that good. I'd take bigger brakes and .3inch stickin out anyday. You'd hardly notice it. But hey its just my opinion

why get custom ones? Skulte already makes 1.7inch spacers for the brake swaps and 4th gen wheels. but custom ones from Skulte are only 6 bucks more so i guess its best that u dial in your wheels to "show" quality fitness

wgripp

iTrader: (1)

So the only difference with .3 inches is overall appearance, not handling or anything like that?

Boosted_SS

he's concerned about scrub radius but IMO if 3/10" is enough to make a significant differance there is something wrong

91L98Z28

According to measurements by Dean, a stock standard third gen scrub radius is 3.630.

1LE's increase the scrub radius to 3.948.

Do the math: that's an increase of 9%.

On a 300HP motor, 9% is 27HP. Think you'd notice an extra 27HP, or is that not significant?

On a 245 width tire, 9% wider is a 265 width. Think you'd notice that?

On a 3200lb car, 9% weight is 288lbs. Think you'd notice an extra 288lbs hitching a ride in your car?

9% higher than 3.73's is the equivalent of 4.06, think you'd notice that kind of gearing change?

Oh, and here's food for thought. The 1LE rotor is only 14% bigger diameter than a stock 10.5" rotor. obviously it must not be enough to make a significant difference, right?

Numbers matter. small numbers don't matter any less. Just because you don't care enough to learn about why it matters or what scrub radius even is, doesn't mean that it doesn't matter.

Would you accept an alignment of they told you the toe-in was off by 3/10"?

DigitalMonarch0

92BLKL98

91L98Z28, Your 9% examples are comparing apples to oranges. Some changes are not as pronounced as others IE .300" wheel offset to 27 horsepower. I installed the Bigbrakeupgrade LS1 kit on my Z28 and now I have much, much better braking. The difference in "scrub radius is" negligible and, unless you have spoken with a suspension engineer knowledgable in this matter it doesn't mean much. I can't really tell the difference in looks (except the awsome look of bigger rotors and calipers) nor handling. Braking performance is definitely worth it. I thought the factory brakes were OK but with performance mods we do on our cars the need for performance braking is and should be a big priority. Don't get off on a tanget about something that is not going to be a big deal. All of these folks responding to this have done some sort of mod to their brakes like this with good results. If you don't mod your brakes then IMHO you have no business modding the engine. You need atleast as much braking power as you do engine power. These cars are marginable at best from the factory in terms of braking.

norcalz28

iTrader: (13)

Just get some factory spacers. 1LE cars came with a really thin spacer for the rear wheels from the factory. My guess is they did this to counter the fronts sticking out slightly more than the rear. If you look on ebay, I see these all the time. Bottom line, it's not going to hurt, and you will prolly be the only one to ever notice.

Will

91L98Z28

My examples are very much apples to apples. Just because a 9% increase in scrub radius is neither pronounced nor important to you, has no bearing on whether or not it's pronounced or important to me. You have no idea what my motivations are, nor my experience with increasing scrub radius. I have owned cars where I've changed the scrub radius by less than this, and have not liked the results.

I'm well aware that the factory braking system is nothing to write home about, there is no need to lecture anyone on that fact. I'm also well aware that the various brake upgrade are substancial improvements over stock.

You may not be aware of the tradeoffs involved when increasing scrub radius, but ignorance of the issue is neither a justification nor a qualification to conclude that "it doesn't mean much."

wgripp

iTrader: (1)

What is a scrub radius, and how does it rob horsepower?

91L98Z28

the topic of what scrub radius is, is best left to the suspension board (or a google search). it does not "rob" horsepower.

91L98Z28

and for whatever it's worth to anyone. based on info dean has posted in the past, it looks like 13" C4 HD's with 1LE large-bearing hubs increase the offset by 0.618". Since rear IROC's are 16mm (or 0.623") offset, it looks like 13" C4 HD's with the 1LE hub and rear IROC wheels on the front will result in stock geometry for the front end.

Orr89RocZ

iTrader: (20)

IF 1LE cars got thicker hubs up front, then they had slightly increased scrub radius...which probly didnt matter much since those cars were so dominant in SCCA racing back in the late 80's. As far as i know the Irocz wheels only came in one spec size... 0mm offset front and 16mm offset rear. never heard of any different 1LE irocz wheels.

I'm sure the change wouldnt affect the steering/handling feel much. with stock rubber size, that small change may give alittle more force upon the steering but i dont think the difference would be that noticeable, UNLIKE those examples you listed above.

If GM made the 1LE cars with slightly wider scrub radius over base brake system IROCZ cars and didnt correct it with different wheels up front, then i dont think you should be worried if you change yours to the same specs. MANY ppl are running bigger GM brakes and i havent heard any complaints on tires sticking out or handling/steering feel.

92BLKL98

I took this info from a search I found on the web:

Scrub Radius
Scrub radius is the distance between where the Steering Axis Iinclination (SAI) intersects the ground and the center of the tire. This distance must be exactly the same from side to side or the vehicle will pull strongly at all speeds. While included angle problems will affect the scrub radius, it is not the only thing that will affect it. Different wheels or tires from side to side will cause differences in scrub radius as well as a tire that is low on air. Positive scrub radius is when the tire contact patch is outside of the SAI pivot, while negative scrub radius is when the contact patch is inboard of the SAI pivot (front wheel drive vehicles usually have negative scrub radius).

If the brake on one front wheel is not working, with positive scrub radius, stepping on the brake will cause the steering wheel to try to rip out of your hand. Negative scrub radius will minimize that effect.

Scrub radius is designed at the factory and is not adjustable. If you have a vehicle that is pulling even though the alignment is correct, look for something that will affect scrub radius.

So as I see it the only way you will see a negative impact because of the slightly increased scrub radius is if you install the space saver spare on your car or run a tire flat or loose a brake function or are running different tires side to side. Like I said I haven't noticed any ill effects on my Z. As long as I've owned the car I know how it is supposed to feel.

One negative it may have is the slightly greater stress on wheel bearings but if you replace your wheel bearings periodically (I do at about 50,000 miles) it really does not matter.

Dude, I'm not Flaming you I just believe you are big dealing this. If you don't like the results don't do it. The bottom line is for the most of us this mod made a big performance improvement. I do believe you have opened a pretty good topic for discussion. It atleast made me research why I have always had a pull on a road with a high center crown or when my brake pads are worn the car tries to overpower the steering upon braking.

Boosted_SS

exactly the bottom line is if you don't want to change it and the scrub radius is such a big deal then DON'T DO IT! but the benefits you get from bigger brakes would be worth any negative effects.

seanof30306

iTrader: (4)

You know, the fronts already fill the wheelwell better than the rears do, stock. I can see where someone wouldn't want to make that disparity any worse.

ES87iroc

I ran into the same issue on my car once I did the ls1 brake swap. Very worthwhile mod, but I didn't think about the slip-on rotor and take it into account for wheel fitment. Opps.

I am going to do a couple final measurements and probably end up going with a 1.5" adapter. The 2" always pushed the wheels too far out in my opinion, but I need to double check and make sure they can come .2" inwards from their original position.

RacerX13

Do yourself a favor and go over to FRAX and ask this question. It's "hardcore" enough that they won't be offended by it, and there are people over there that can actually be helpful.

I think you did already answer your own question though- do it and run rear wheels on the front.

J.Cutta

I wish I would have since this post before I upgraded my fronts to 1LE's. I have 245/40/18 with IROCS . It srubs kinda bad when you turn the wheel full turn. Didnt have a problem before the upgrade. Is there a tire I can go with to fix this like a 235/40/18