325/50/15 BFG Drag Radial

[Joe 1320]

The correct answer is: It shouldn't when comparing TREADWIDTH of same manufacturer. The section width may be a hair different due to the sidewall height. The shorter sidewall height will have to make a shorter radius curve from tread to rim surface than the taller sidewall height. That means usually, the shorter tire will bulge slightly more on a narrow rim. It all depends at that point, on rim width to treadwith ratio. If you compare from different manufacturers, that is comparing apples to oranges. Not only that, catalogs can have wrong stats quoted.

 

[2slow]

Got The Answers

I built an 87 TR with 325 DR on 10" wheels with 6.5" BS had to cut almost all the frame out left only about .5 to.75 "then braced it on the inside, the tires fit perfect little room on both sides no rubbing was alot of work, also had to move the wheel tub in. Now I have another 87 TR with 275/60s on 8" wheels with 5" BS just had to notch the frame 1" this is a good fit the tires are under the car and I like the tall tire. Hope this helps....

 

[NoSlix]

Actually, Joe 1320, what we found is that in a pure drag race environment the 325's liked a narrower wheel. When you put them on a 10" or wider wheel and bring the bead farther out the tire doesn't wrinkle as easily. The BF Goodrich rep originally clued us into this. We were shaking the tires right at the 60' mark and he told us to try a slightly narrower wheel. I questioned it and he said forget what works better with slicks and regular tires.

 

[2slow]

Fast!

Shane, what kind of cars and set ups do you have running those #s that is impressive!!!

 

[Joe 1320]

Originally posted by NoSlix
Actually, Joe 1320, what we found is that in a pure drag race environment the 325's liked a narrower wheel. When you put them on a 10" or wider wheel and bring the bead farther out the tire doesn't wrinkle as easily. The BF Goodrich rep originally clued us into this. We were shaking the tires right at the 60' mark and he told us to try a slightly narrower wheel. I questioned it and he said forget what works better with slicks and regular tires.

You'll also find guys running the same times with a 10" tire too. The ideal setup is to run the smallest tire that gets the job done. Like I said before, I have run deep into the 9s on street tires and touched the 8s on slicks so I hear what you say, I just don't happen to subscribe. No doubt you are running quick, my bet is that you could run the same ET with a bump in MPH with a smaller tire if your chassis were dialed in for the smaller tire. The way I see it, that setup would work on a soft launch, the tire grows with speed and runs on it's center. The guy that inquired probably isn't in a racing only environment and to put a combo like that on the street is not smart. Yes it can be done, not on a TR without notching the frame and such, and it certainly would suck in the handling depatment of street duty. Been there, done that, got the t-shirt and returned it.

 

[Warp6]

These are the 275/50's on my car. They measure 25 1/2" from the ground to the top center of the tire. I'm looking for a 28" tire (preferably radial) and just a little wider

http://hyperphoto.photoloft.com/view/Image.asp?s=cano&u=1740492&a=1304103&i=9748399

 

[Joe 1320]

I don't know if this will help, but here is a pic of 295/50/15s on the rear......They measure almost 27 inches tall. Not quite the 28 you were looking for.

http://www.psend.com/users/joe1320/Image05.jpg

http://www.psend.com/users/joe1320/Image11.jpg

http://www.psend.com/users/joe1320/Image04.jpg


You will have to cut and paste the link..... so many free sites don't hot link pics anymore.


There are also 305/50/16s available if you have 16" rims.

 

[NoSlix]

2slow: Car # 10046 is the current car with the most potential. It's a 90 Mustang LX long rod 302 setup with a liquid to air intercooler and a dual ball bearing Innovative Turbo R trim T76. It's made 2 passes, one of which was the 9.78 at 146 without the intercooler turned on and at only 15psi. Oh, and that was with a converter so tight that it only made 3psi for 250ft. I could have ran beside it it was so slow! Now that we're starting to tune on it and get the converter correct, I expect that we'll see what it's true potential is on the radials(I built it with the intent on running 8.90s on them). I do drive it to work a couple of days a week, also.

Joe1320: What we gain due to less rolling resistance with the smaller tire we lose about 100ft out when the boost comes up and shakes the tires. We can actually 60ft pretty decently with the 275's, but the consistency suffers. In a heads up race, I'll take consistency.

 

[Joe 1320]

Originally posted by NoSlix
What we gain due to less rolling resistance with the smaller tire we lose about 100ft out when the boost comes up and shakes the tires. We can actually 60ft pretty decently with the 275's, but the consistency suffers. In a heads up race, I'll take consistency.

You mean sprung weight. The difference in rolling resistance would be next to nothing at the point that you mention. The amount of energy required to accelerate the wheel and tire combination would be more far meaningful for the first 220ft than rolling resistance.

 

[NoSlix]

Actually, I meant to put unsprung weight AND rolling resistance. Either way, the smaller footprint tire loses because of inconsistency. On the 325's we're able to come out of the hole with it firewalled. The only way to do that on the 275's is with a converter that's too tight. Then 100 to 200ft downtrack it shakes the tires. It's just much easier on the 325's.

FWIW.......we're looking to see how far we can push a turbo6 into the 9's on drag radials now.

 

[TurboGH]

You cant argue with those results (1.39 60' on DRs). Very impressive. Who gives a $&!@ if the wheel is only 8". Within reasonable limits, finding the correct air pressure will provide the correct footprint. Nice Job!

 

[Joe 1320]

I'll make one last post and then I'll just shut up. I've learned everything I know about drag racing from making mistakes. That means I've had to experience the situation and learned from it in order to comment. To take a tire that is approximately 12.8 inches wide and squeeze it on an 8" rim is not the safest. It causes excessive sidewall flex which generates more heat (sometimes good, sometimes bad) For a trailer queens on slicks(the better choice) or DRs, you can possibly get by with no mishaps if you are lucky. In order to make it work you have to have substantially lower tire pressures to get the tire to have a flat contact patch across the tread width. This also affects overall handling and can really make for a squirrely ride on the big end, especially if you have to get off of the throttle and actually steer it. You will also experience accelerated treadwear in the center of the tread, and you end up getting half the useable life of the tire. I know because I have done it. I learned from it, we learned how to dial the chassis to make a safer combination work. When we did that, we went from low to mid 9s to high 8s with no HP increases or gear changes. No way should it be done on a car that sees a fair amount of street duty. That advice was meant to help out a fellow TR owner and again, it was from learning from mistakes.

Kudos for making a 325 on an 8" tire work. I'm glad it works for you. I don't doubt that it works on your Mustang, I don't dispute it, and in reality don't really care. It's not a TR. I'm done.

 

[NoSlix]

Actually, Joe...... I run that tire on a 9" rim. My point from the beginning was that it's been done on 8s safely before. And we were even told to do it by the BFG rep. Would I run a 28x10.5 slick(yes.........I also tune and drive a low 8 second turbo car running 10.5s on a 12" wheel) on an 8" wheel with a 1000hp turbo car? Hell no! That would be a wild and more than likely unsafe ride. But we haven't been talking about slicks here. You can run a drag radial at 10 psi and do your hair at the same time going down the track on a low 9 second pass. The same car on slicks is all over the place. It's not the same. I was just trying to give a little advice on a subject(drag radials) that I know a good bit about. Maybe I'll keep my experience to myself from now on.

Regards,
Shane

 

[KEVINS]

Originally posted by NoSlix
Maybe I'll keep my experience to myself from now on.

Regards,
Shane

NO WAY! All experiences are welcome! Different ideas may give some of us that extra edge... I like hearing everyones experiences then making my own decision based on the most info gathered! If I listened to everyone who said that my ideas would never worked then my cars would be slow..

Keep all ideas coming!
ks

 

[2slow]

Talks Cheap!

Over the years I've heard alot of talk and seen very little action so when someone like Shane IS running faster on radials than most people can run on slicks I am intrested in his advice because been there and done that is way better than..... I read it,I'm gonna do it, I now this guy that once did it,ect ....Thanks Shane and keep it stright.......

 

[NoSlix]

Thanks Kevin and 2Slow.

Kevin: FWIW......all the new stuff is in and fit perfectly. I got a feeling that with the new converter and FAST to replace that "hunk-o-crap" Gen VII, we'll see a .35 or better right out of the trailer.

 

[J Banning]

Originally posted by REDS HOT AIR
any pictures of a regal with 325/50 's on it?

i was thinking about them myself ...will a frame notch and fender trim get them to fit?

Bump bump... to the top!

Anyone running the 325/50/15 on a BUICK?

 

[10secBu]

Just to throw another combo in the mix.

3600 lb '79 Malibu, iron headed 454 bbc (over 55% on the nose), th400, footbraked at 1800 rpm, 4.10 gear, 275/60-15 M/T D/R on a 9.5" wide rim, best of a 1.41 60', no power adder, no launch retard, nothing...stock suspension with bolt-on upgrades. Et's in the 10.20's @ just shy of 130 mph.

Last season on a 325/50-15 BFG D/R and a smaller 414 ci pump gas bbc, best 60' of 1.43 with ET's in the 10.50's to 10.60's.

Sorry, not a Buick, but I could provide a pic of the Malibu which is frame notched/mini-tubbed with the 325/50-15 D/R.

No doubt about it, Shane knows how to get a D/R car down the track. While what he says about rim width may seem unconventional to some, you have to keep in mind that setting up a fast drag radial car is totally different than a car running on slicks, or even ET Streets/Hoosier QTP cheaper slicks. What works on a bias ply tire car more than likely will not work with a radial tire. You have to be open to new/unconventional ideas if you wan to make a D/R tire work in your favor.