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  #1  
Old 03-20-2001, 09:51 PM
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70Barracuda 70Barracuda is offline
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Looking for ideas. I have N 50 15 Pro tracs in back. All under the body. Regular shocks Radials up front. When I got the alignment the guy said the diff. in radial/bias did'nt matter. The car would never drive good cuz the fat tires in back would always be pushing the front. I have to think if radials were on back it would drive better. If I put bias in front would it?
All the front suspension pieces are good. I asked about polyurethane, he said it would not help. Help me out guys. How do I make my car drive better. It's fine on a smooth non rutted road. On the highway in ruts it's scary! Plus, I don't want people seeing my ride all over the road. Thanks alot for your imput.
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Old 03-20-2001, 10:08 PM
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NitroMethane NitroMethane is offline
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Throw some radials on the back and save the bias plys for race day.
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Old 03-20-2001, 11:12 PM
turbododge turbododge is offline
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Running radials in the front and bias in the rear will make the car want to swap ends very easily. As was said, get some radials for the rear for daily driving, before you wreck.
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Old 03-21-2001, 12:18 AM
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pishta pishta is offline
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Bias ply's are going to track differently. Your car may wander, it is a well read rule never to mix bias plys and radials for this reason.
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Old 03-21-2001, 12:35 AM
karfixer karfixer is offline
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I have to concur- it's a bad idea. I had a similar setup on my '72 Duster 235/60R-15's fr L-60-15's in back- the thing was insanely tail happy and could never tell when it would break loose. Best to have all 4 the same type- parts are getting hard to find nowadays, as are good old Mopars.
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Old 03-21-2001, 01:03 AM
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Dudes I used to run L-60-15s on the back and 205/75/R15s on the front for years on my 70RR&68 Sattelite,They handled just fine,absolutely nothing squirrely about it,although under throttle thru a corner with the back tires spinning was more predictable and fun than with radials,of course i had absurd amounts of hp,which easily overpowered my traction but even at freeway speeds it was fine the only drawback was in rain or God forbid snow,70 barracuda If your car is following ruts its not because of the rear tires,usually its worn front upper or lower control arm bushings and/or Ball joints but you may also need to check your rear axle endplay,the max is .018,but Ive found that to be too much and will cause the rear to follow ruts,you can run .012 w/o any drawbacks.itll handle better.........PRO......
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Old 03-21-2001, 02:11 AM
DartGT66 DartGT66 is offline
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I know it's not recommended to drive with 'mixed' tires and it's even forbidden here. However, I have driven that way for years, M&H's or M/T ET Streets in rear and 205/60/15 radials in front. The car is way better to drive with the radial/bias combo than with bias tires in all corners.
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Old 03-21-2001, 02:42 AM
Chargerchuck Chargerchuck is offline
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One of the first things I learned in autoshop was never to mix bias and radials. I remember I tried anyway and found the car to be unstable. Check with a reputable tire shop (yes they are in business to sell tires but if you know someone & trust them it's worth a second oppinion.) I'm curious what the NHRA rules are on this..I know on the street its a bad idea. Why take such a risk?
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Old 03-21-2001, 03:20 AM
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Thanks all for the replys. I know the bias radial not supose to do thing. Funny thing, the guy at the alignment shop is a old school rodder, and he is really sticky about having a solid front end before he will work on it.
The car drives fine except on the ruttef highway.

Pro, your endplay comment is really baffling me. I just had it set up with the factory 3.54s I cannot see how that makes a differance. I'm not saying your wrong at all. I just don't understand.

I worried that radials in back will be akin to ice skates when I wanna stand on it. However, if that makes it drive better, there I am. Any ideas on a good radial for a 10x15 wheel?
Again, thanks so much for your replys.
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Old 03-21-2001, 03:36 AM
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70,all bias tires will follow ruts to some degree,if your rear tires are bias then theyll follow ruts too,if your rear axle shaft endplay is significant,itll allow the bias tire to better follow the rut,hope that makes it understandable,just jack your diff up and push and pull on the wheel,does it seem like more than .018?it could be a contibuting factor,againChargerchuck do you believe everything you read? then why can a stock 340 handle 1200cfm of carburation?etc.....PRO......
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Old 03-21-2001, 04:20 AM
72Challenger 72Challenger is offline
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The reason that you're not supposed to mix radials and bias-ply's is because of the difference in slip angle that this combination will induce. So running radial tires on the front and bias-ply's on the rear induces oversteer, a dangerous condition. There are some experts who say it's okay to use radials on the rear and bias-ply's on the front, however.

But there are many other factors at work. In the case of a vehicle with much wider rear tires than fronts, understeer can be a problem. That's the "fat tires in back pushing the front" (never heard it said that way before, but it's a good description). This can be compensated for by reducing the slip angle of the front tires. Common ways to do this are by adjusting tire pressures or sway bar stiffness. Another way is by using radial tires on the front. Pro's experience is different that karfixer's because he used a narrower tire on a heavier car. One was stable, the other not. This is like any other area of car tuning, you need to adjust things until you get it right. The difference between tuning suspension and tuning carburators is that I never heard of anyone killing themselves with a badly tuned carb!

As to the car handling fine on smooth roads but wandering in ruts, I don't believe that's because of the mismatched slip angles. If you really had a problem from the mixed tires, with the radials in front, you would have a tendency for the rear end to slide out under hard cornering. If you have this problem, by all means match up your tires. If not, look elsewhere for this problem. (If the rear breaks loose while cornering under heavy throttle, that's not the same thing, by the way. Test for this at a steady speed, in a place where a spin-out won't hurt you or the car!)
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Old 03-21-2001, 06:45 AM
DartGT66 DartGT66 is offline
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I guess that in my case with the DOT slicks at the rear the handling isn't an issue. Those tires are dangerous with any combo if you can't drive, but definitely better with the radials in front.
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Old 03-21-2001, 01:29 PM
GTS225 GTS225 is offline
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Hey, 70 Barracuda......you also said something about polyurethane. Your suspension guy isn't entirely correct. It might not help with the wandering and rut-following problem you have, but poly bushings do work. The rubber bushings in your car has a rather large amount of "squish", while poly doesn't do it as much. Using poly bushings will translate into a tighter suspension, better road "feel", and overall driveability/handling.
Big hint here, though.....use the silicone grease that normally comes with the bushings or kit. Installing them dry won't hurt them, but you'll probably notice some additional squeaks, and it'll be the bushings making the noise. Poly bushings will last longer, aren't harmed by road salt or chemicals that normally find it's way onto the road, and if you want to be a bit different, they can sometimes be gotten in a few different colors. If you do it "piecemeal", you might not notice the change much, but if you go the whole kit, I suspect you'll like the end results.
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Old 03-21-2001, 02:19 PM
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I have Dunlop 245 50 15 on the front of my charger and 12.50 28 15 M/T ET streets on the back it handles fine. The only thing I notice is the wide tires Front and Back both like to follow ruts, but if you pay attention and keep your mind on your driving I'm sure you'll be alright.
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  #15  
Old 03-21-2001, 06:16 PM
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70Barracuda 70Barracuda is offline
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All the information is really apreciated! Radials will go on soon. The car does just fine in all but the rutted highway driving. I am planing on a complete urethane redo after this summer.
This website is awesome!
Again, thanks so much.
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