Tell me what you think.

[jak112460]

Iam am leaving a link to a photo album. The first picture of my car is with 18x12 rear wheels with 335/30/18 tires. I changed to 19x12.5 with 345/30/19 tires. The second picture will be with the 19" wheels and has a date of 4/25 in the right hand corner. I hope this works. Thanks.
http://www.imagestation.com/album/?id=4290403961

 

[jak112460]

By the way, any picture with the 4/25 date, is with the 19" wheels.

 

[IH2LOSE]

Jack i would love to see the photos I am shopping now for a set of whells and tires for my C5 .But up load the images to this site They may be a little smaller But I hate to have to join all those photo sites just to see a picture or two and then only to find out the album is closed because the bandwitch for the free site has been exceeded

 

[EHS]

335s and up without tubbing will rub if the offset is anywhere near correct. They also protrude past the fenders.

 

[jak112460]

My car has the tubs. They work great and you cant tell they are there.

 

[EHS]

My car has the tubs. They work great and you cant tell they are there.

I don't believe that ih2lose has tubbed his car yet.

Hence, your tire and wheel combination would not fit his car without problems, and/or tubbing.

Thus my comment, that "335s and up without tubbing will rub if the offset is anywhere near correct. They also protrude past the fenders."

 

[corvettecrazy]

how exactly do you "tub" a wheel well??

 

[jak112460]

Go to Lingenfelters website. They make the tubs and if done correctly you can't tell they were done except that there will be huge tires inside the fenders.

 

[EHS]

Remember that the C5 has various sophisticated computer software programs that include traction control and active handling.

These programs were written with certain basic assumptions on tire response and traction, such as coefficients of friction, tire contact area, etc.

When you diverge too far from the basic program assumptions, by installing larger than expected (by the program) tire sizes, rolling diameters, etc., you may experience erratic behavior and response from the system(s).

See some posts on the other fora, where a gent ran into problems with his larger than normal tire sizes.

Not to say you can't do it, just remember that you are becoming a test driver.

 

[jak112460]

You assume that the person doing this modification is not doing their homework. Everything done on my car was done by a prefessional and of course the computer was programmed to accept the tire diameter. Doing your homework first is the only way to do it right. The tubbing is no big deal if you get a good body shop to do it. Talk to other people who have done this modification to get ideas on wheel offets and tire sizes. Believe me I emailed a bunch of people before I did anything.

 

[EHS]

You assume that the person doing this modification is not doing their homework. Everything done on my car was done by a prefessional and of course the computer was programmed to accept the tire diameter....

The "computer" you reference as being reprogrammed for tire diameter is simply the one that affects the speedometer readout. For example, this is a feature of the Hypertech III.

I'm talking about the ABS module, traction control, active handling, etc. black boxes, all of which cannot be reprogrammed that easily -- as a matter of fact, I don't know of anyone that does it at all.

In the past I've discussed with c4c5specialist having simply the steering feel of my 2000 C5 convertible reprogrammed to match that of the Z06 (which is heavier), and after he did some research, we both agreed it was not worth the trouble, if it could be done at all. It would have meant digging into the ABS module and software, by a computer programmer familiar with the Bosch/Delphi systems.

Same thing with the even more than important (than simply steering feel) alogrithms for computer assisted responses to braking, skids, and other handling parameters when you go to larger (or smaller) tire sizes, or size differences between the front and rear, that are outside the computers' parameters.

You become a test driver.

See this link and Justin Bell's comments:

http://www.vetteweb.com/tech/0301Vette_Retiring/

Here's what he says:

"I know our Z06 very well, so I know exactly how it should handle. I run the car with the active suspension set in the competition mode. But the interesting thing I noticed immediately on the project car is that the tires are wider, lower, have huge grip and the brakes are very impressive. These factors increase the corner entry speed to a fair degree; this means that the mid corner speed also is increased. The net result of this is that your one-setting active handling system is permanently activated. In my opinion, this is because the parameters in which it was designed have been exceeded. I could feel the grip of the car, but I couldn't use it."

Search the other boards, and I'm sure you can find some more discussion on the issues and problems when folks mount wheels and tires that exceed the computers' (and I do mean plural) parameters. Not to say they can't be driven. Justin Bell, who certainly knows how to drive a Corvette and has also done his homework, certainly does, just not that one might want to do that everyday on ordinary roads.

 

[jak112460]

You are obviously much smarter than anyone else doing this exact same swap. So tell me what the parameters of the computer are? I'll give you some help. I contacted Specter Werks
http://www.spectergtr.com , they do the exact tire and wheel combo that I did. They work closely with factory engineers and they told me that the factory ABS computers and other peripherals were capable of learning different tire sizes. The computer must be reprogrammed for the tires sizes. He went on to say that this change was made after the 2001 model year. I have had no problems with my setup. Again as I said before, rather than speculating about problems, it is best to contact those that have actually done the modification. Mallett does the same wheel and tire combo on some of their cars as well. As far as using a Hypertech power programmer, if you have no respect for your car then go ahead and use it.

 

[EHS]

You are obviously much smarter than anyone else doing this exact same swap. So tell me what the parameters of the computer are? I'll give you some help....

jak112460:

I'm not saying that it doesn't work, just that the car can become unpredictable in certain situations. Others have had problems, and accidents. Read some past posts.

Please be careful out there.

 

[c4c5specialist]

Hi there,
There is something that is being suggested but NOT talked about.
ACTIVE HANDLING.
While you can appropriately calibrate the tire diameter to the speedometer, and the traction control system, you cannot completely rewrite the algorithm for the active handling system.
While it does work, just as JAX has stated, it will not be optimal. The reason being is that every tire diameter size will give a different hertz at 5mph, which is only one parameter of the active handling algorithm. 245/45r17 will be 1.12 hz. However, the rears, at 275/40r18 will be 1.08. So, with that in mind, figure this. If your hz 1.08 @ 5mph, then multiply that times 10, which will give you 10.8. Ok, so then, lets say you have 295/35r18 as a small jump, but it will show the point. These size tires have a hertz of 1.10, times 10, which would be 11.00. While this may not seem significant, consider this. Your active handling reads tire rotational speed, as well as the yaw rate sensor, lateral accelerometer, and the like.
If you are in an ACTIVE HANDLING event, your wheel speed plays a vital role in this function.
The EBTCM is so precise, there is a different algorithm for the coupe/convertible, than that of ZO6.
So with that, I would not know if these aftermarket tires and wheel are optimized for the active handling, however, we are talking optimization, not if it will work or not.
The actual learning of the wheel sizes is only within the certain parameters of tire wear, NOT different sizes.
The ACTIVE HANDLING is a safety feature, and this is why the discussion has gotten to this point.
Jax and EHS are both correct, to a point. There are WAY TOO MANY parameter to debate and fine tune.
Will it work??? Probably. Is it optimized???? I would suggest no.
Allthebest, c4c5

 

[jak112460]

I will make a point to counter your point and be brief. Say you have two brands of tires that are the same size. I have found that from one company to the next there can be a 1/4" difference between manufacturers because of what they call tolerences. For example, Pilot Sports 345/30/19s are supposed to be 27.1 if you do the math. Michelin rates them at 27.4. Nobody knows for sure what the parameters of the active handling is but it has to be large enough to cover manufacturers tolerences plus wear. I do not believe that there is enough of a tire difference to create any issues whatsoever. I know from my point of view that I will never be testing the limits of my handling system anyway so it's moot to me and I believe that it is for most of the people on this board. As long as codes are not being set I'm ok with the way my car drives.