[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.

.

[Formulajones]

I ran 275/50/15's many many years ago in a BFG drag radial. Late 80's??

They worked okay from what I remember, but back then I was using them on mild HP applications.

As HP increased over the years I found myself going to the taller 275/60's drag radials as I had much better luck getting them to work at the track, plus it fit quite a few of the radial racing classes they had at the time. The taller side wall allowed some flex, the radials do wrinkle quite a bit, which helped absorb the shock a bit, and traction.

I still do have a couple cars here, with less power, that simply don't like the taller tires. They just don't have enough rear gear in them for starters, and a 28" tire just hurts it at the track. My bird is a prime example. Not enough HP and not enough rear gear. Too long to explain here but I've been round and round with that car.

I'm going to buy some 26 inch tires to run on a couple other cars here simply just to help them out with gearing and they will find their way on the bird for some track time.

Going from your 27" tire down to a 26" at the track, you'll probably see a 200-300 rpm difference through the traps.

[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!

[PAUL K]

I would run whichever tire looks better. Either of those tires can be made to work. I've run both tires into the nines at close to 140mph.The shorter tire should be slightly faster at the track and the taller tire might be slightly faster from a dead stop on the street. I didn't care at all for the looks of the taller tire on my 80 TA so I went with the 255's.

[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.

[68lemans462]

Originally Posted by torqhead

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.

Thanks bro!! I need to stay on top of my game so you dont spank me next time out at the strip with all your new goodies!

Here's a pic of Dave (torqhead) and I racing at Bandimere. The tire sizes are well depicted here. I think Dave runs a 225 front tire and a 275/60 rear so the difference is more obvious. I've had alot of guys tell me they dont think I run enough gear. I think the trap RPM's are 5000'ish. This was another reason I was considering the 275/50's.. I'm not convinced that I "need" them yet, however.... I really wish I could try a set without having to drop a grand to do it.

[PONTIAC LARRY]

Totally do the 275-60 MT not the 50 , you got a 3.42 with a 455 more than enough gear for that tire. I went from 255 60 MT SS DRs to 275 60 MT SS DRs on my 7.4/ 11 sec CAT and it was a more consistent launch with 1.6 60 fts , 10" stall and 3.64 gear 3750# . I was swapping my Cat 5x5 15x8 Chev rallys to our LWB 74 C10 454 to run it at track and if track prep was very good it would hook good but have since went to a permanent 295 55 MT SS DR's combo on the old 15x8.5 slots on the C10 and that Long bed is a real bracket winner these days very consistent, truck runs 8.3's / 13.1's with 1.8 60's and its just a 12" stall and 3.07 gear 4400#. I Love the MT SS radials and I will never buy regular slicks again as far as I care. Runs quicker than slicks and drives 10x better feels safer and is safer. My old 12.6 Cutty wagon Pont 455 4250# 3.08 gear combo went 12.6 on slicks and 12.5 on 235/60 15 OLD MT SS DR's

[leeklm]

Originally Posted by PAUL K

I would run whichever tire looks better. Either of those tires can be made to work. I've run both tires into the nines at close to 140mph.The shorter tire should be slightly faster at the track and the taller tire might be slightly faster from a dead stop on the street. I didn't care at all for the looks of the taller tire on my 80 TA so I went with the 255's.

I do like the lower stance your car shows, and was one of the reasons (along with gearing) I went to a shorter 26" rear on mine. Once I installed lighter drag springs up front to increase available suspension travel, the car stated looking like that model picture posted below with the larger rear tires. Here it is with the 26x10 and a 25/26" drag skinny up front.

Hopefully with better shock adjustments and a smarter driver/mechanic, I can remain consistent with the 26" rear.

For street I throw in a twist style spring spacer to give a little lift to the front, especially when 2 people in the car.

Sent from my SM-G965U using Tapatalk

[torqhead]

Originally Posted by 68lemans462

Thanks bro!! I need to stay on top of my game so you dont spank me next time out at the strip with all your new goodies!

Here's a pic of Dave (torqhead) and I racing at Bandimere. The tire sizes are well depicted here. I think Dave runs a 225 front tire and a 275/60 rear so the difference is more obvious. I've had alot of guys tell me they dont think I run enough gear. I think the trap RPM's are 5000'ish. This was another reason I was considering the 275/50's.. I'm not convinced that I "need" them yet, however.... I really wish I could try a set without having to drop a grand to do it.

Ha, I don't recall seeing that pic! I've got 215 65R15's in front, the only reason is I already had those tires with a shorter rear tire at the time and they're still in good shape. I went to taller tires in back to get better traction a few years ago and although I still can turn them fairly easily the taller street tire made a difference too. I'll be replacing the front tires with something taller but rather spend money in other "areas" for now.

[PAUL K]

Originally Posted by leeklm

I do like the lower stance your car shows, and was one of the reasons (along with gearing) I went to a shorter 26" rear on mine. Once I installed lighter drag springs up front to increase available suspension travel, the car stated looking like that model picture posted below with the larger rear tires. Here it is with the 26x10 and a 25/26" drag skinny up front.

Hopefully with better shock adjustments and a smarter driver/mechanic, I can remain consistent with the 26" rear.

For street I throw in a twist style spring spacer to give a little lift to the front, especially when 2 people in the car.

Sent from my SM-G965U using Tapatalk

Thanks Lee, obviously I agree. Your car looked Bad A$$ when I saw it at the Grove last October. Unfortunately you disappeared before I had a chance to come over and talk. I think you were parked next to me or Darby was between us.

Not sure if it's an option for you, now when I go to the track I throw on some smaller M/T drag radials.... They've handled everything I'm willing to throw at it so far. I'm hoping to stiffen up the chassis a bit in the near future.... Or take some stroke out.

[TCSGTO]

I run 275/60 Hoosier DR’ s on my 68 that is lowered 2”. With 27” tall 215/75/15’s on the front the car has a nice level stance. The 275’s tuck up in the wheel well aren’t really noticed at a glance unless you get down and look. They are just under 27-3/4” tall actual mounted size so not much difference in height from 255 Mickeys but over 1” more tread width.

275/60 Mickeys are over 28” tall in actual size plus the sidewalk width is wider than the Hoosiers with the same tread width. To fit them I’d have to “Joe Dirt” the back of the car, not gonna happen since I think the 68-69 A bodies look much cooler with the tail down.

[Formulajones]

275/60 MT's out back and their 28" front runners

Stock ride height with stock springs from Coil Spring Specialties.

[Formulajones]

Same tires stock wheels

[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.

[4zpeed]

Originally Posted by 78w72

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.

Originally Posted by 68lemans462

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.

The confusion is his question was between 255/60's and 275/50's, someone else mentioned the 275/60's.



Frank

[4zpeed]

Originally Posted by 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.

Nice post Steve, and with respect to that, although initially taking more energy to turn over, steel wheels will take advantage of inertia more so than aluminum wheels, something for the OP to consider if planning to increase from a 7" to 8" factory style rally 2 already contemplating traction issues.

Originally Posted by 68lemans462

I also just put in a new converter that seems to hit HARD so I'm anticipating more traction problems.

If this is the case, the 50's are not going to be your friend. Converter, lower profile tire and added inertia of 15x8 rally 2's will all work against you.

I'm with you on the opinion of appearance and stance, very much in line with mine, all the while looking for an acceptable level of traction.

I think the 26.30" or 26.42" will appear small as far as height goes and will also have issues hooking, I like the profile as is. Uber cool pic!





Frank

[Steve C.]

Also noted within that information I posted for interest is the subject of sidewall deflection, oven overlooked for the road feel not just the traction issue here.


.

[78w72]

Originally Posted by 4zpeed

The confusion is his question was between 255/60's and 275/50's, someone else mentioned the 275/60's.



Frank

im aware of the 2 sizes he was asking about... lots of others mentioned the 275/60 & i just pointed out the very small size difference of the 255/60 vs 275/60 that he called joe dirt & stupid... wasnt trying to argue or anything, just mentioning that 1/2" isnt much of a difference between those 2 sizes.

& looking at FJ's gto pics with 275/60 on the rear im not seeing "joe dirt" at all... looks great IMO. all depends on the suspension & stance of the car & of course personal preference.