GTJim

Ok, going to be getting some new wheels for my Vette. Already have them picked out, TSW Interlagos in 19X9 and 20X10.5

I had picked Michelin Pilot Super Sports in 265/35R19 and 305/30R20. My problem is the 305's are on national backorder with no ETA as to when they will be available so I'm looking at alternate sizes. I want to stay with the Pilot Super Sport so that limits me to 265/40R19 and 295/35R20 or 275/40R19 and 315/35R20. Looking at the specs for the two rear tire sizes, Tirerack has the tread width listed as 11.5 for both sizes.

How can a 295 series and a 315 series tire have the same tread width???? Doesn't make sense to me. If the 315 isn't any wider than the 295 I'll just go with the 295 series. Any thoughts???

Mickeyrx70

mrr23

I'll explain as this is in my wheelhouse. The 295 and 315 are the measurements from sidewall to sidewall of the tire. Each manufacturer decides what percentage tread width they want. Some use 80%, some use 95%, and some use anywhere in between. Also rim width can change tread width slightly.

When you compare the 295 to the 315 of the same aspect ratio (the 35 number), there will be a different tire height.

One other point. Generally, the taller the sidewall, the less tread width manufacturers will use. As evidence by the tires you have selected.

GTJim

Thanks for your response. So the 315 will be taller and have more sidewall than the 295 but overall the width (tread width) will be roughly the same. Got it, I always thought as you go up in series (295 vs 315) the tire was wider.

GTJim

In my experience, which is very little, the tread width is what gives the overall appearance of width to the tire. The higher the tread width number the wider the tire appears. So in this case since the tread width number is the same for both tires, the 295 should appear to be the same width as the 315.

mrr23

Yes. People tend to focus on the tread area of the tire because it's the most appealing.

Rookieracer

Pilot Super Sports

265-35-19

295-30-20

GTJim

Very nice, thanks for posting!!!

What wheels are you running and do you have any shots from the rear? Just trying to see how wide they look and if they are flush with the fenders.

Edit: Just noticed they are TSW's

Rookieracer

Sorry I don't have any other pics and I'm not with the car today. I can shoot some Monday. Having the tires flush with the fenders was one of my primary concerns, and they are.

The wheels are TSW Nurburgring in std C5 offsets.

Rookieracer

I apologize in advance for the crappy pictures.
Hope this helps.........

From the rear.

Rookieracer

Front....

grantv

Have you considered the gear ratio change and speedo re-calibration effects from going to such a larger diameter tire? Speedo; easy fix.
Gears; either you'll have to live with the change (slower off the line in theory) or change the gears to get you back to your base line.

Stock tires base model 275/40/18 = 26.66 OD (Z06 tires 295/35/18 = 26.13 OD)
Assuming yours is a base model your circumference = 83.75.

295/35/20 OD = 28.13 OD, C = 88.37
83.75/88.37; your 3.42 gear (example) just became a 3.24 gear

315/35/20 OD = 28.68 OD, C = 90.10
83.75/90.10; your 3.42 gear is now 3.18

GTJim

Thanks for posting the pics

Looks perfectly flush with the fender.

GTJim

You bring up a good point and one I've considered. The 315/35R20 is too tall of a tire and I'm told I'll have problems with rubbing. I'd prefer to get a 305/30R20 but they are on national back order so the 295 is my only choice at this point unless I go with a different tire.

GTJim

Here's a pic of the car. Running 265/40R17 and 295/35R18. Car is lowered all the way on stock bolts. With this combo it sits way too low and scrapes every where. What I'm trying to do is raise the car up with the larger diameter wheel and tire combo. I'm thinking about an inch will do it.

I could always adjust the bolts but then I end up with too much wheel gap for my taste.

Rookieracer

My thoughts exactly. Fill up the fender without having to worry about driveways and speed bumps.
I tried 18-19 combo on my Vert. It looks good, In fact a lot better than stock, but a little more sidewall height than I was looking for.
For the Z06 I chose the same tire combo I have on the Vert, but in 1" larger rims, which essentially reduced the sidewalk by 1/2" per side.

IMHO,
The 19-20 combo is what the car should have come with stock.

Rookieracer

Like this?

GTJim

This shows exactly what I was talking about, 295/30R20 Michelin Pilot Super Sport, all the same size and manufacturer but three different tread widths. The two tires will definitely look wider than the one but the other two the difference is so small you wouldn't notice it. 11.5 inches wide is pretty wide for a 295 tire, it actually has the same tread width as the PSS in 315/35R20.

Rookieracer

I agonized over the tread width issue before and after the purchase. There is no clear cut part #. Who is to say the guy in the warehouse ships any 295-30-20 he feels like. For the rears, I purchased the 11.5 tread width version.

You will find the same issue with the fronts. I purchased the Porsche version.

GTJim

That's the one I want, the 11.5 version. No part number is going to make it interesting.