Which Size Rear Tires?

[Just a Six?]

So I still have my MT 275-60 x 15 Drag Radials on the back (which were new back at BPG 2013) & they still have some tread for a track day but that's pretty much history for me so I'm in need of street tires & the front TA are still fine.                         
Amazon has MT 275-60 x 15 but I'm thinking maybe a 255-50? instead for a less aggressive look & a better fit?
What size tires are you guys using on the back these days? 

 
No I don't drive the car much for those tires to still have tread after 3 years of BPG events & 10 years driving. 
I do have a couple stock rims just in case I get the itch I can swap on the DR's.

[Steve Wood]

The 255-50s are a bit short I think. Getting hard to find 15s.  If they make a 255-55, that would be closer to a 26" diameter, I think

[Steve Wood]

Ok, I don't see anything. May need some 17" wheels. SMH

[Just a Six?]

Steve I agree that the 255's do look short. The 275-60 look good & with Air Bags in my springs I can adjust as needed so unless I hear of some other ideas come next year it will be the MT 275-60. I'm not changing rims etc. Honestly the thought of selling the car has crossed my mind this summer & it's the 1st time I've ever thought like that. I only put on about 600 kms so the oil isn't even dirty. The crazy thing is that I'm now out of the city with lots of roads to cut loose on but how many times am I going to do that? I don't know but if I get the price I'm thinking about it will probably be a move I'll make.
Now when spring rolls around & I fire it up the 1st time I won't be thinking about that because it's still gives me a rush when I jump on it!   

[xracerx13]

Correct me if I'm wrong but this is what I came up with...

275-60-15 are 28" tall and go better with 3.73 gears,. With stock 3.23 gears the speedo and ECM will be off.
255-50-15 are 25" tall no good period. Your speedometer and the ECM will be off.
255-55-15 are 26" tall and works best with stock 3.23 gears.
275-50-15 are 25.8" tall and require an 8.5" wide wheel.

[Steve Wood]

For a car running 20 psi boost or more, the 28" tire will usually out run 26" tires (both with 3.42 gears).  Taller tire is faster out of the hole and generally on the top end as well depending on equivalent cams.  That is my experience.

On the other hand, 255 tires often run just as quickly as 275's on launch as the length of the patch is more important than the width.  Of course, if one has enuf more horsepower than usual, the width may contribute a little more.

The speedometer issue easy to resolve as a switch to a yellow gear brings it back in line.

Modern chips are not bothered by tire diameter as many of the factory functions have been disabled or ignored.

The problem comes with simply finding a tire in the desired size as 15s and 16s are basically obsolete in our tire ranges.

I went to 255s on my GN.  Went back to stock speedo gear.  It has 16" wheels.  My T has 15" rims and I am tired of the tire scuff.  I guess rolling the lips would fix that.  A lot of cars seem to have the axle offset a bit to one side or the other.  My GN did not scuff but it was really close.

[Scoobum]

Dave, the definitive bible for these cars for tires is on this vid. The 255/60/15 is what you're looking at. MT sells them as a DR. Height is 27 inches and fits perfectly on the stock rim. Time stamp is 8:30. If you're gonna hit the track 1 last time and wanna set your best ET and MPH, then grab a 112 race chip from Eric and I'll put it on the back bumper for ya. Gotta get up to Uxbridge as I have a cousin up there. Hope all's well.

https://www.mickeythompsontires.com/drag-tires/et-street-s-s


https://www.youtube.com/watch?v=wWP-7sht2WU

P.S- Just got back from my engine builder from Montreal with a S2 engine for a customer in Toronto.

[Steve Wood]

Can't argue with "Been there, Done that"

Diameter on the M/Ts is a bit over 27".  Plenty of guys have run well on them and they will not hit the fender lips.  For a good weather tire, I think that Brad has the right solution for your needs

[Just a Six?]

Thanks for all the info guys I've run 275-60 for so long that I barely remember the others but I did have Hoosier Quick times in a 255-? Brad I may do one track day some time if Tim & Paul go out but I want Street tires that I feel safe with if I see rain clouds coming. I put the car away Monday after a car wash & a half hour cruise with the temp about 5*-6* & the ass end kicked out every time I gave it a bit of throttle so that's no fun. Just plain scary at times.
I'm going to see what I find in 255-60 & 255-55
Again thanks for the help! 

I haven't been paying too much attention to the car stuff the last 4-5 years but Wow prices are sure not what i remember from back in the day when stuff was plentiful   

[Scoobum]

I'm done with Buicks, as more and more Buick vendors are refusing to ship up here...and you're right...the parts prices are beyond stupid. Took Joe ages to get the parts to rebuild that S2 engine I took down to Montreal and back for a customer. If this guy wants to race this car it'll be here in the spring for line lock, rear brakes and suspension for launching. Hartline is doing the XFI for it. Joe ran 9.20's with doing nothing with Cals tune. His car is a monster. He had it sold, but the guy backed out at the last second. Like you, he's ready to get out.

[gnonyx]

It has been around 5yeaes ago when I got tire replacement
FRONT ARE: 245/50 ZR16
REARS ARE: 255/50ZR16
I did read it's getting hard to find 255/50's
Right now this is in the repainting stage until next year final paint job

[Steve Wood]

Same size as I installed about five years ago.  They might have 300 miles on them LOL

My car is lowered about an inch and they look good

[gnonyx]

Same size as I installed about five years ago.  They might have 300 miles on them LOL

My car is lowered about an inch and they look good

Did you lower by installing a different type of springs?
Speaking of rear springs, What type of OEM spring: constant, or variable?

[Steve Wood]

Eibach used to make a 1" lower spring. I think they stop making the G body spring.  But someone else has a set.  OEM were constant rate

[motorhead]

I am putting 315/50R17s under my MCSS... and I mean tucked. The M/T SS tires are a good compromise, but for regular street duty I prefer the Toyo TQs.

275/60R15 is the best looking tire for stockish car/wheel combo.

https://www.instagram.com/p/CwvrFHsv866/