You've a '95 Caprice LT1. The OE factory tire size for a '95 Caprice is 235/70R15 which is 27.95" tall.
255/50R17 is not your OE tire size (only 27.03" tall).
Your speedo will be most accurate with these:

275/50R17 (27.82" tall)
255/55R17 (28.04" tall)
235/60R17 (28.10" tall)

If you get your pcm reprogrammed, choose any size between 25.6" tall and 29.1" tall, so long as it has a minimum load rating of 98 or more.

275/40R17 - 25.66"
245/45R17 - 25.68"
315/35R17 - 25.68"

285/40R17 - 25.97"
255/45R17 - 26.04"
235/50R17 - 26.25"
245/50R17 - 26.65"

255/50R17 - 27.03"
235/55R17 - 27.17"
245/55R17 - 27.61"

275/50R17 - 27.82"
255/55R17 - 28.04"
235/60R17 - 28.10"
245/60R17 - 28.57"
275/55R17 - 28.91"
235/65R17 - 29.03"
255/60R17 - 29.05"

 

You've a '95 Caprice LT1. The OE factory tire size for a '95 Caprice is 235/70R15 which is 27.95" tall.

This is not exactly accurate. The civilian Caprice came stock with tire size P215/75R15. The optional tire size was P225/75R15. The 9C1 police Caprices came standard with P225/70R15 tires and the optional tire size was P235/70R15. At least that is what I remember about them.

Mike--Hamilton Chevy

 

Having bought and sold well over 1,000 1991-1996 Caprices at auction I purchased a bunch of tires over the years. The above info is how I remember it. Right, wrong or otherwise.

 

Again, not disagreeing, not disputing.

Here's what I remember:
OEM tire specs for 91-96 B-cars:
235/75R15 (28.87") OEM for Cadillac Fleetwoods with V4P Tow, V4U Limo, B9Q Hearse, or B05 Armour
225/75R15 (28.28") OEM for 91-96 B-wagons
235/70R15 (27.95") OEM for 91-96 B- & D-cars with V92, or 9C1s with LT1
215/75R15 (27.69") OEM for 91-93 9C6 B-sedans (taxis) with LB4 4.3L V6
225/70R15 (27.40") OEM for 94-96 B-sedans with L99 4.3L V8, 9C1s with LT1 (VZ2 130MpH limiter), & 1A2s
205/75R15 (27.10") OEM for 91 sedans (GM themselves 'retconned' this spec, however, because it was dumb)

255/50R17 (27.03") OEM for 94-96 B-sedans with WX3 or WX8

Your memory and mine were never at odds.
As of '06, I only care about 235/70R15, and 235/75R15, because all the smaller tire sizes have no decent performing tires left to choose from.

 

You guys realize you can just go on Discount Tire and they have a tire sizing engine that can give you the right 17" tire sizes, right?

 

hey guys just bought ss wheels

So if that's the case, then the discussion about the 9C1 stock tire size isn't as relevant here. 255/50ZR17 is indeed the stock tire size for the 17" SS wheels. And it unfortunately is a fairly uncommon size; none of the world's 5 largest tire manufacturers make a tire in this size presently.

I'm actually myself in the market for stock size tires, and it seems the options are realistically limited to:

• Nitto NT555 G2 - 255/50ZR17 101W - UTQG 320 AA A (seems to be a popular option)
• Hankook Venus ST RH06 - 255/50ZR17 101W - UTQG 420 A A (tends to be slightly more expensive, mixed opinions as to whether it's worth it)
• Riken Raptor ZR A/S - 255/50ZR17 101W - UTQG 300 A A (cheaper & less common option, haven't read too much on this one)

Generally you won't see those locally stocked, rather they would need to be purchased through Tire Rack, Walmart, SimpleTire, etc. There's a sticky thread on this forum regarding tires for stock wheels, reading into it you'll see some people have gone with slightly different tire sizes with effective ±3-5% diameter difference.

 

255/50ZR17 is indeed the stock tire size for the 17" SS wheels. And it unfortunately is a fairly uncommon size; none of the world's 5 largest tire manufacturers make a tire in this size presently.

I'm actually myself in the market for stock size tires, and it seems the options are realistically limited to:

• Nitto NT555 G2 - 255/50ZR17 101W - UTQG 320 AA A (seems to be a popular option)
• Hankook Venus ST RH06 - 255/50ZR17 101W - UTQG 420 A A (tends to be slightly more expensive, mixed opinions as to whether it's worth it)
• Riken Raptor ZR A/S - 255/50ZR17 101W - UTQG 300 A A (cheaper & less common option, haven't read too much on this one)

The wheels don't care about which tire is mounted to them, so long as they can support the car.
However, the pcm cares about tire height (and which reluctor is paired with which gear).

255/50R17 is the OE size for the Impala SS.
The correct tire sizes for any LT1 B- or D-car that is not an Impala, however, would be:
275/50R17 - 27.82"
255/55R17 - 28.04"
235/60R17 - 28.10"
as those are closest to 235/70R15 (27.95").

Of course, the pcm can be reprogrammed for other tire sizes, leading to more and better tire options.
Anything between 25.5" tall and 29" tall works in the wheel wells of any B- or D-car.

 

If it was me with SS wheels i would buy this one. Personal preference.

• Riken Raptor ZR A/S - 255/50ZR17 101W - UTQG 300 A A (cheaper & less common option, haven't read too much on this one)

-ALF out...

 

If it was me with SS wheels i would buy this one. Personal preference.

• Riken Raptor ZR A/S - 255/50ZR17 101W - UTQG 300 A A (cheaper & less common option, haven't read too much on this one)​

• ​

If it was me with SS wheels, and a B- or D- car that was NOT an SS, I'd consider recalibrating my speedometer for:
Toyo Proxes ST III 275/55R17 . 109V . UTQG 500 A A
or
Toyo Proxes ST III 255/60R17 . 110V . UTQG 500 A A
or

Forced to consider snow / ice traction, there are at least:
16 different tires I'd consider in 235/65R17
12 different tires I'd consider in 235/60R17

All car tire sizes between 27" and 28" diameter are ... underrepresented in selection and performance.