[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.

[ta man]

I think the 255/60/15 M/T is the best choice for the OP needs and wants. The only time a bigger tire may be wanted or needed would be if he raced at a much lower DA..but even then many are running this tire at low ets and 60fts.

[68lemans462]

Originally Posted by ta man

I think the 255/60/15 M/T is the best choice for the OP needs and wants. The only time a bigger tire may be wanted or needed would be if he raced at a much lower DA..but even then many are running this tire at low ets and 60fts.

I believe you are likely correct!

[torqhead]

Originally Posted by 68lemans462

I believe you are likely correct!

Hey Dan, since the tire sits up in the wheel well I don't think it makes it look too big and as we talked about when I looked into this previously I found I got better traction with the taller tire. If you want I'm open to have you try mine on your car before you invest money.

[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.

[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.

[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

[68lemans462]

ACTUAL Tire specs from Summit

[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.

[68lemans462]

Originally Posted by 78w72

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.

Well, lets do some math. I run a 235/60R15 in the front, these are 26.1"" tall. The 275/60's are 28" tall, that is a 2" difference. In my opinion having 26" tires all the way around does not look "stupid". The 255/60's are as tall as I want to go, which is why I asked the question about the 2 tire sizes to begin with!

[Steve C.]

Posted for interest..........

"Wheels: How big is too big?

The general rule is to only use as big a wheel as you need to clear brakes and suspension components. The weight of an average car for road racing usually requires brakes that are too big to fit inside 15-inch wheels, so larger ones are used.
So the question becomes what is the best size wheel to use ? It's natural for us to think that bigger is better, and it's true that the general public prefers the look of larger wheels, but don't let that trick you. Oversized wheels will slow you down. It all comes down to moment of inertia. The excess weight of a larger wheel is an important issue, but the diameter of it is a much more important factor. The effect of a 10-pound weight at the end of a 12-inch string is much less than a 10-pound weight at the end of a 36-inch string. The larger-diameter wheels are not only heavier, but are much harder to control the rate of rotation like the weight at the end of the string.
Now let's look at overall tire diameter and the effects of sidewall flex. Let's say you've decided on a tire diameter and are looking at what combination of wheel diameter and sidewall height to run. The taller the sidewall, the more flex it can have. This is a good and a bad thing, but mostly a bad thing. When the sidewall id tall, it can deflect quite a bit, throwing away any sense of your suspension alignment settings. Too short of a sidewall a sidewall can be oversensitive to surface conditions, and gives you far less warning before traction is lost. The trick is to find the right balance.
The sweet spot for most of our muscle cars and track cars is 17- or 18-inch wheels. this isn't just our opinion, but that of many industry insiders. The 12- or 13-inch rotors usually chosen by the road racing crowd fit in these wheels just fine, and don't need the additional clearance given by a 19-inch or larger wheel. Consistent with that, BFGoodrich doesn't even make their sticky road race R1 tires for any wheel larger than 18 inches in diameter.
So why does NASCAR still use 15-inch wheels ? The rules mandate these 15-inch wheels and have for many years; knowledgeable fans speculate that this rule won't change. It can be argued, however, that oval track cars use this tall sidewall as a part of their tunable suspension. Since their quickness is defined by how they can plant power out of the turns, tire pressure can be used to improve that.
That brings us to ask why new Corvettes and Vipers use such large wheels. The simple answer to that is because they look cool. There is no advantage to these larger wheels except their looks. The laws of physics would suggest that using a smaller wheel while still clearing the brakes would make the car faster.

.

[78w72]

Originally Posted by 68lemans462

Well, lets do some math. I run a 235/60R15 in the front, these are 26.1"" tall. The 275/60's are 28" tall, that is a 2" difference. In my opinion having 26" tires all the way around does not look "stupid". The 255/60's are as tall as I want to go, which is why I asked the question about the 2 tire sizes to begin with!

that math is not related to the 2 tire sizes you were asking about, first time ive seen 235/60 mentioned... my comment was pertaining only to the 255/60 vs 275/60 rear sizes, not comparing fronts to rears.

again, a 275/60 is only .5" taller than the 255/60 & is not that much of a difference to look "stupid" or joe dirt as you said. thats all my comment was about.

if you dont want to run 275/60 thats fine, but the math is still correct & they are not much different in height. & 235/60 front to 255/60 rear is almost 1.5" difference... a half inch doesnt change that off set much at all.

[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.