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Track times 1/8 mile
Just got back from the track. Best time is 8.58 @ 85mph. 2.0 60 foot. Nearly imposssible to launch consistantly. Had a great time but I feel that most of the power is not getting to the ground. One wheel peel all the way. 302 just ran great but will really lite the tire.
later Dennis kelley |
Are you running 15inch or 17 inch tires. If you can't hook up I would guess you have 15 inch.
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15 inch
yes its the 15 inch tires. The 60' time was 2.07. could not use the cars power because the tire would break loose in first and second and hit the rev limiter. I'm shopping for a new wheel and tire package and differential. I had a lot of fun with the car but its way off its potential.
later Dennis. |
The biggest problem here is the typical BDR open rear differential. You really need some kind of posi traction.
7.8 sec 1/8th mile, 2.001 sec 60 ft, 11.99 at 118 1/4 (5800 shift point) |
Yeah I know. I'm pricing a diff right now. what was you mph in the 1/8 Excaliber.
later dennis |
Well that may be true of an ERA, but a Backdraft with the BMW open rear and 17inch Nitto Drag radials hooks up very well.
I have a 3.10:1 open rear and I did 12.3 at 111 with only a 351. Pertty close to a 11.99 from a 427ci. And I hope to do better with a 3.91 open rear. |
This is because a BMW "open" rear and a Ford "open" rear are two different things. I find it amusing how often owners of other makes sound off on the BDR forum ;)
The BDR 17" wheel package includes some nice Drag Radials on the rear which help in the dig. JayBar has it right... |
The subject line doesn't specify BDR, it's about 1/8 mile times. My 1/8th mile speed was 94.56 mph.
A one legger rear is a one legger rear, no matter what car it is. Sometimes it runs both tires, sometimes it doesn't. Tires sizes and compounds have little or nothing to do with it. The laws of physics will determine if both tires act together or only one gets traction. Come out of a corner with the weight shifted to the outside tire and the inside tire is going up in smoke. Put one tire in the dirt and the other on pavement and the "dirt" tire will the only one spinning. 17" tires won't help the laws of physics. I'm not saying a one legger is a "bad thing", but Dennis Kelley states one tire is going up in smoke, draw your own conclusion! This coming Friday night the Hawaii Cobra Roadster Club is meeting at the drap strip. A NEW BDR with a Roush 342 will be there (running Goodrich T/A's). He knows the T/A's represent a serious traction problem, and that assumes he can get them BOTH to turn, a valid concern. If I bought a BDR (it's possible) I would opt for the limited slip, no question about it. |
If it were me, I'd stick with 15" wheels/tires.....you can't expect a 17" low profile tire to "give" like it you need it to under a launch. If 17 and 18" tires gave so much more traction, then all the drag racing guys would be running them......
The slicks are called wrinkle wall for a reason.....you can't wrinkle a set of 30 series rubber..... |
yeah I'm going to keep the 15inch wheels. I'll just pick up to new wheels for some new drag radials. The diff is on its way out. An open diff is an open diff. I 've tried everything. Hey Jaybar great time do you know your sixty foot time.
later Dennis |
Dennis,
On getting the second set of wheels. You will find with the BMW bolt pattern 15 inch wheels are not available. Unless you get a second set of Team 3 wheels at about 300.00 each. We are looking into steel wheels for road racing, since we found a cheep source for Goodyear RR tires. But unless you try 4.75X5 which is close to the BMW 120mmX5 you are looking at custom rims. But for only drag racing the 4.75 pattern may work. Anyway I am not a drag racer I only do it as a tuning thing. But my 60 foot time on my best run was 1.89 1/8 mile 7.98 at 90.21. |
The difference between the 15" and 17" wheels is the selection of tires and manufacturers you have in the larger size is larger. With less sidewall "give" AND "bulge" you can run a larger/wider rear tire without concerns for rubbing. This is why the 17s are much wider overall ... they also perform better because they are newer molds then the dusty 15" BFG molds.
As for the rear ... the BMW "open" is not totally "open" and it will in fact act differently than a Ford or other make's open rear. I'll have to find a link to more info ... so many bookmarks, so little time ;) |
Keep in mind this is from a "one set of wheels and tires" perspective. Sure you can pick up some Goodyears and run 'em really low on the track for better results. But I'm talking all around performance.
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Cashburn I would really would like to research just what kind of unit the BMW is. If it's not really open, what does that mean I wonder.
There are all kinds of different style posi units, some just "help" get both wheels traction. Then there are "locker" units, when pressed into service they WILL make both wheels turn, but you don't always want that 100% lockup thing on a road course. The ultimate would be a "spool", both wheels ALL the time, even in corners or while parking, very radical (typical drag race application). Do the BMW units employ some kind of "clutch" mechanism for a "soft lock"? If so, maybe Dennis broke his! |
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