[68lemans462]

I have been running M/T ET Street "R" tires size 255/60r15's on 15x7 Rally 2's. So far I really like these tires. They seem to hook up pretty well and they also dont wear too bad. I have left them on the car for the last couple years since the BFG radials dont stand a chance behind my 455. I feel way safer driving the car with these tires most of the time. One of my racing friends is pressuring me into getting 275/50R15 M/T's either in the SS or R version. I will probably have to replace the M/T's this season and looking at this option. There is some extra expense involved because I would have to buy a set of 15x8 rally 2's to accommodate the wider tires.

The 255/60's are 27.5" tall and 8.82" tread width. The 275/50's are 26.30" tall 10.1" tread width.

How much traction improvement is there between these tires? Is it worth the coin to go in this direction? I like the idea of a shorter and wider rear tire, especially if it will improve traction.

[Stan Weiss]

Don't know about the tires, but remember the difference in height changes your effective rear end gear ratio.

Stan

[lust4speed]

Smaller diameter tire will be much more prone to breaking traction, and would be better to go with the 275/60R15 at 28" tall. Doesn't the SS tire have a pretty hard compound?

[GTOLou]

Post this over in the race section. Those guys will know better. Make sure you know the stall on your torque converter. I used to weekend drag race a bit - but am no expert. And - I always used a four speed.

Your rear gear in the signature is 3.42 - not that deep of a gear for the strip. The shorter tire is a cheap way to lower your rear gear ratio to find out if the lower gear will help your ET.

[Mike Davis]

Go with a 275/60/15 over the 275/50 series. Bigger footprint. The 275/50 actually measure 25.8"

[78w72]

275/50 at 25.8" is too short of a tire IMO unless you want to reduce the gear ratio a lot, & most pontiacs dont want/need low gear ratios unless its an all out race car set up for it. if you like the 255/60 i would go with the 275/60 which can still be ran on a 7" wide rim ok... its not ideal but for straight line racing the added sidewall bulge isnt as much of a problem as a tire on the street doing cornering. also the 25.8" tire wont look right in the wheel well of most cars.

i have the 255/60 m/t's for the last 4-5 years & will be going to the 275/60 soon. & although not street legal, the pro bracket radials are supposed to be a little better traction wise than the DOT approved drag radials.

[Singleton]

Another vote for 275/60. I've gone through several pairs of drag radials over the last decade, M/T, Hoosier, and M&H Racemaster. All seem to have about the same traction, but I like the M&H best, lasts a little longer and has a little more tread pattern

[Chief of the 60's]

Stick with the size you have. Lower the pressure when racing. You won't miss the 1.2" in width but you will miss the 1.2" in height at the big end if you switch.

[RocktimusPryme]

Im using the 275/50, but I only have 3.08 gears.

[68lemans462]

I'm not at all interested in 275/60's. They are way too tall and look stupid, plus they make the gear ratio softer. I can't disagree that these would probably give the best traction, however... .. I run these 100% of the time on the street and dont like the "Joe Dirt" look with an almost 2" taller tire in the back. I use a 3.42 gear so I'm not afraid of a little bit more gear.

So, back to the original question and reason for this post -- the difference between the 2 tires 255/60 and 275/50..

275/50 M/T is NOT 25.8", the SS are 26.42" and the R are 26.30" as previously mentioned

[straycat]

My 455 powered 68 prefers the 275/60R15 over the 255's. It's got 3.55 gear. The 400 powered 65 Tempest stick with 3.42 likes the P255/60R15. Both sets of tires are the Street R. Funny they both run near identical ETs but the 68 just blows the smaller tire off and the 400 doesn't make enough power for the larger tire.

[68lemans462]

ACTUAL Tire specs from Summit

[leeklm]

Went through this just last year... in my case, went from a 28x9 bias slick to a 26x10 radial. I have 3.50 gears (low trans gear set, similar to 3.73 gears with normal transmission) so figured I could use the extra rpm.

Getting traction has proved to be challenging unless track is prepped well. At first I was blaming the radial, but think the bigger culprit is the smaller diameter tire. Going to a looser converter has made this even more of a challenge. Once I get it hooked, I love the combination, but need more consistency for bracket racing!

Will see how it goes this spring, but I may end up going back up to a 28" radial, and use my 26" tires when going to BIR, which is top notch. I think I could almost launch from the wet box at that track

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[68lemans462]

Originally Posted by leeklm

Went through this just last year... in my case, went from a 28x9 bias slick to a 26x10 radial. I have 3.50 gears (low trans gear set, similar to 3.73 gears with normal transmission) so figured I could use the extra rpm.

Getting traction has proved to be challenging unless track is prepped well. At first I was blaming the radial, but think the bigger culprit is the smaller diameter tire. Going to a looser converter has made this even more of a challenge. Once I get it hooked, I love the combination, but need more consistency for bracket racing!

Will see how it goes this spring, but I may end up going back up to a 28" radial, and use my 26" tires when going to BIR, which is top notch. I think I could almost launch from the wet box at that track

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This is just the type of feedback I'm seeking. I also just put in a new converter that seems to hit HARD so I'm anticipating more traction problems. I never thought that a shorter wider tire could make it worse but it certainly makes some sense when considering the increase in effective gear ratio.

[leeklm]

I did some googling on this topic a while back, and it was proving a taller/narrower tire was often preferred, partly due to the pounds per square inch on the ground. In the end, wider was not always better.

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[78w72]

Originally Posted by 68lemans462

I'm not at all interested in 275/60's. They are way too tall and look stupid, plus they make the gear ratio softer. I can't disagree that these would probably give the best traction, however... .. I run these 100% of the time on the street and dont like the "Joe Dirt" look with an almost 2" taller tire in the back. I use a 3.42 gear so I'm not afraid of a little bit more gear.

So, back to the original question and reason for this post -- the difference between the 2 tires 255/60 and 275/50..

275/50 M/T is NOT 25.8", the SS are 26.42" and the R are 26.30" as previously mentioned

joe dirt? lol. 275/60 is only .5" taller than 255/60, how does that make them look stupid at only 1/2" taller? i think a 26" tall tire would look more "stupid" on most cars... going to the 275/50 at ~26" tall is 1"+ shorter & on many cars will look too small IMO. but if you like them thats all that matters...

not trying to persuade you to use 275/60, just mentioning some advantages like wider foootprint & better traction & keeping the final gear ration closer to what you have with 255/60 unless you want/need to go lower with a over 1" shorter tire.

[Chief of the 60's]

LOL!

[Navy Horn 16]

Originally Posted by 68lemans462

I run these 100% of the time on the street and dont like the "Joe Dirt" look with an almost 2" taller tire in the back. I use a 3.42 gear so I'm not afraid of a little bit more gear.

275/50 M/T is NOT 25.8", the SS are 26.42" and the R are 26.30" as previously mentioned

This might not be the exact information you are looking for, but it's still information.

275/60/15s both right (MT ET Street Radial Pro) and left (Nitto 555).

MT is on an 8 inch Snowflake, Nitto is on a 7 inch Rally 2.



I don't know how much of the extra width is the MT being wider than the Nitto, and how much of it is being mounted on a wider rim.

Just like you, I've got to keep the drag radials on for safety. The M/T hooks way better than the Nitto, but my next set are not going to be the Radial Pro version. The rubber and traction is fantastic, but the sidewall is designed to be soft so you get some of that wrinkle at the track. Even with higher air pressure for street driving, it's a little squishy on the street and I feel it in curves.

I wish someone made a road racing tire in 275/60/15s.

[Steve C.]

Nitto P275/60R15 107V

Tread depth 6.3
Overall dia. 27.76"
overall width 11.10"
Approved rim 7.5-(8.0)-9.5

MAXIMUM
Load (lbs.) @ Press. (PSI)
2149 @ 44

Weight 28.82 lbs.


.

[leeklm]

"The M/T hooks way better than the Nitto, but my next set are not going to be the Radial Pro version."

I use the Nitto 555 in a 275/60 as a street tire. For me, that tire was a disaster trying to hook at the track.

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