Silverton

Has anyone tried this tire combination on a C6 non-Z06: 275/35-18 front and 295/30-19 rear? I'm looking at the CCW wheels in 18x10 front and 19x11 rear. By the way, the front OD = 25.6" while the rear OD = 26.0". So, yes, the rear OD > front OD. These would be Michelin PS2 tires in those sizes.

AU N EGL

If your looking at getting new wheels go with 18s" all around. Less rotating wt and tires are less expensive.

18x10 front and 18x11 rear.

gkmccready

I have 18x11 front and rear. 295/30r18+305/35r18. I have the most minor of rubbing on the front (inboard, with the tie rod arm), but the wheels stick out [too much]. I'd go 18x10 front if I had it to do again -- 275/35r18 in that case.

Silverton

I'm not ready to move up to track tires, or even R-compound tires. So, initially, I'll run street tires on the track. For the C6 non-Z06, the widest tire that can be run on the street is the 273/35-18, and the 18x10 wheel works well with that tire size.

For this front tire size, the available rear sizes (rear OD must be greater than the front) are limited. With a 19" rear wheel, the choices are either 295/30-19 (OD=26.0") or 305/30-19 (OD=26.2") tires. With an 18" rear wheel, there is only one choice, the 295/35-18 (OD=26.1"). For street tires, the 19" wheel offers more and better choices.

Joe_G

I'm pretty sure your size ratio is too far from stock and will mess with your active handling - your car will do weird things in lane changes, drag control will kick on at odd times, etc. Two of my buds went with 305/30/19 rears and 275 fronts and it didn't work. I think you need to go to the z06 325 rear size if you want to go 275 front. All assuming you want to keep active handling on.

I use nitto 555 r2 305/35/18 and 275/40/17 on C5 wheels for track time and they work great. BTW I would never use street tires on the track anymore after using the 555 r2's. It's just so much more fun using tires designed for the job at hand. Night and day more fun.

AU N EGL

not likely. as long as the rear is only slightly larger OD then the front. Does not have to be 1". or a certain width.

and if you turn off AH/TC you can run the same size wheels and tires front and rear without a problem.


Even for street use 18" all around works, tires are less expensive and have more choices.

Good Luck

Silverton

With 275/35-18 (OD=26.1") front tires and 18" rear wheels, there is only one available rear tire size: the 295/35-18 (OD=26.1").

With 19" rear wheels there are two (2) available rear tires sizes: 295/30-19 (OD=26.0") and 305/30-19 (OD=26.2").

AU N EGL

Have you looked at other tires?

The main reason I ask is 19" wheel/ tire combo are heavier then 18" wheel / Tire combo. Most ppl never notice the difference, until they put both on. The 18" are much lighter and quicker.

and dont get hooked on the OD stuff. You will soon turn the Ah/TC to comp or OFF so it wont matter.

Silverton

Keep in mind that I'm talking about street tires here. The rear tires have to be just a little bit taller than the fronts. At least with a 19x11 rear wheel, I have the option of a 305/30-19 tire.

Also, there's a thread under C6 Tech/Performance that confirms that the widest rear tire that will not stick out (on a C6 non-Z06) is a 315 mm tire. However, there are no 315/30-19 or 315/35-19 street tires available; and the 315/25-19 tires are too short while the 315/40-19 tires are way too tall.

Having said that, I agree with you completely re an 18" rear wheel. So, I think I'll purchase the CCW 18x10 front wheels only (with the 275/35-18 tires) and use my OEM 19x10 rear wheels with 295/30-19 tires. When those tires need replacing, perhaps there will be more wide 18" tires available.

Joe_G

If you are talking street where you want to keep active handling on... you would be well served choosing tires that keep the same size difference front to rear of about 1". The C6 is much choosier about proper F-R ratio than the C5 was and two of my buddies tried 305 19's 's with no luck.

Silverton

Joe, I hear what you're saying. The responses to this same post on the C6 Tech forum are pretty much saying the same thing. Spin pointed out an option that I had not considered: BFG KDW2 tires in 275/35-18 front and 295/35-19 rear. That front-to-rear tire differential is very close to OEM. Unfortunately, there is only one tire manufacturer (BFG) that makes a 295/35-19 tire.

There is a thread on the C6 Tech forum that confirms that 325 mm tires will stick out in the rear. If I were to use those tires, I might as well mount 295/30-18s in the front: then I'd stick out at both ends! Even worse, the only street tire in that size is the GY run-flat!

In conclusion, it seems that the only wide street tire option for the C6 is the BFG KDW2 tires in 273/35-18 front and 295/35-19 rear; don't even consider 18" rear wheels unless you always drive with TC off.

Joe_G

I'm kind of in the same boat as you - I have Ace Slick wheels which are Z06 size up front but 11" in rear, 1" less than Z06 size. They are at the edge of the fenders but not sticking out. Stock tires are stretched a bit to fit on the rim. I want to run Z06 size tires but I was trying to find someone who did it first to see how far, if at all, it sticks out.

Silverton

I posted this on the C6 Tech forum:

Here is a table of tire combinations for 19" rear wheels:

Front Size / Front OD / Rear Size / Rear OD / Height Difference / Tire

245/40-18 25.7 285/35-19 26.9 1.2 OEM

275/35-18 25.6 285/35-19 26.9 1.3 PS2, GS-D3, KDW2, PZero Rosso, Advan
275/35-18 25.6 295/35-19 27.1 1.5 KDW2, Kuhmo Ecsta MX
275/35-18 25.6 295/30-19 26.0 0.4 PS2, RE050A, PZero Rosso, Advan, R888
275/35-18 25.6 305/30-19 26.2 0.6 PS2, RE050A, PZero Rosso, Advan, R888 (2008)

265/35-18 25.3 285/35-19 26.9 1.6 KDW2, Advan
265/35-18 25.3 295/30-19 26.0 0.7 PS2, PZero, Advan

255/35-18 25.0 285/35-19 26.9 1.9 KDW2, PZero Rosso, Advan, RE050A
255/35-18 25.0 295/30-19 26.0 1.0 PS2, PZero Rosso, Advan


Here is a table of tire combinations for 18" rear wheels:

Front Size / Front OD / Rear Size / Rear OD / Height Difference / Tire

245/40-18 25.7 285/35-19 26.9 1.2 OEM

275/35-18 25.6 295/35-18 26.1 0.5 PS2, GS-D3, KDW2, PZero Rosso, Advan, Ecsta MX
275/35-18 25.6 305/35-18 26.4 0.8 R888

What's missing here is this: What is the minimum height difference between the rear tire and the front? There have been several reports that the 275/35-18 front with 305/30-19 rear (height difference = 0.6") may work. If that combination works, then perhaps any height difference greater than or equal to 0.6" may be OK. There are also reports that the combination 275/35-18 front with 295/30-19 rear (height difference = 0.4") does not work very well.

AU N EGL

MattW_VA runs the same size tires on all four course on his C6Z51. He does run with AH/TC off with no problems. His C6 is also an early production, if that makes a difference.

To My Understanding and from talking to Chevy engineers, the rear tire only needs to slightly larger OD then the front. Not a specific distance.

What is also missing in that report is the skill of the drivers. I would not be surprised, and we have seen this on the track, guys with minimal skills put on sticker tires, think they are hot chit, then slide around a corner. The cause this slide to AH/TC issues and wrong tire diameter, when in actuality it was the poor skill of the driver.

I would say stick with an 18" rear wheel do to the weight of the rim/wheel combo will be much lighter then the same rim/tire in 19" sizes.

I have seen some same CCW rear wheel designs, one was an 18x11 the other was 19x11, almost a 2 lbs difference in weight with the 19"

IIRC each 1 lb or rotational wt was about 4.7 lbs of static wt we calculated here a few months ago. So 2 lbs or rotational wt is about 9.7 lbs of static wt / wheels. Say 10 lbs or 20 lbs in the rear wheels.

Does that really matter? Yes it can for acceleration and even more so for braking.

We also understand that purchasing a set of after market wheels is a big purchase and you do want to do your best to get everything correct.

HTH

PS the last combination is very nice.

Silverton

That last combination (R888 with 0.8" height difference) should work fine. But, how good would the Toyo R888's on the street?

AU N EGL

The R888 is not a street tire to my under standing. I might be wrong, but lots of ppl that I know in England race a full season on the R888s

codename Bil Doe

PM me if you're looking for a non-C6Z06 race setup (315's all around). Many people on here say they don't fit but I've run them np for a full season. They tuck under the fenders and don't stick out. Can also run a 335 in the rear without any rubbing or sticking out.

Silverton

So far, it looks like 275/35-18 front tires are OK on a non-Z06 with 305/30-19 rear tires. For this case, the height difference between the rear and front tires is 0.6".

Has anyone tried 295/35-18 rear tires? With 275/35-18 front tires, the height difference between the rear and front tires is 0.5". So this tire combination might be OK.

There have been reports that 275/35-18 front tires with 295/30-19 rear tires has problems. Here, the height difference between the rear and front tires is 0.4".

Shinobi'sZ

Not sure but am trying to track down a Steering Wheel Position Sensor code that is occurring when I get the Service Active Handling/Traction Control on the DIC.

I switched from Michelin PS to BFG KDW 275/35/18s....BFG was supposed to release the 335/30 18 KDW NT but was delayed. I have been running the CCW 335/30 18 rear and 285/35/18 fronts on two different C5s for the past 7 years no problem. Because BFG didn't have the KDW NT (335) I purchased some 335 Toyo Proxes RA1...which give me enormous traction over the Michelin PS 335s. I will probably always use the Toyo Proxes because of the traction they have and the fact that they come with 8/32nd tread depth...which allow for more tread life (street).

However this code appeared almost immediately after putting the 335/30 Toyos on with the BFG KDWs....I think the Toyos are a little smaller because I was also able to put back on my rear brake ducts. I know that the Steering Wheel Position Sensor goes bad...but it seems coincidental with my tire swap.....has anybody ran the 275/35 18 with a 335/30 18 rear and had any problems?

Thanks