Why does my car catch ruts so bad?

So my car drives straight on nice flat blacktop, and have had it up to 100 a couple times with no issues. Front clip is a 67 camaro, rear is 10 bolt on leafs. Issue is when im going down the highway, it catches ruts really bad and throws the car all over the lane. i have to hold onto the damn thing to keep it between the white lines.

What can cause this?

 

what kind of tires are you running? bias-ply tires are known for this...

 

(btw, cold chow mein lyrics Tom Waits Shore Leave)


Catching ruts;

a couple of things can cause rut riding, start with the tires. IMHO, Bias ply tires follow ruts more readily than radials. Inflation pressure can make a big difference.
Worn suspension will also contribute to wandering.

 

Also improper wheel alignment, or worn radials or narrow tires (really skinny) or improper inflation. I would start with the simple and work my way towards the difficult.

 

Also many states are texturing the new concrete with grooves parallel to the traffic, SD does this, certain tires Bias OR radial will wander like a radio flyer at speed. The tires on my daily pickup did this untill I got the tread worn down.

 

Is the car lowered? That will throw the bump steer way off. Having worked with oval track cars for years, you might be shocked if you ever saw how much a wheel steers when you run it through its travel, esp. an older car.

 

I'd double check the toe in with a tape measure.

 

Good man! just picked up Small Change last week

Fronts a 14 inch Radial T/As, not sure the width but they are pretty wide. 40psi fronts

Rear are Hurst Cheater slicks capped on 235-75-R15s at 35 psi

Im thinkin of finding a narrower front tire and see if that helps

 

my vote is tires if they are bias, but IIRC you have radials. check your alignment, all your front end really, cuz youre really down in the front which is putts the majority of the weight on the front tires, so they are gonna go where they wanna go, haha. and yeah, wider is gonna have more contact path, but you dont want to run too narrow, or youll catch more smaller ruts.

 

OLD..........hard like plastic... bias-plys.

new bias-plys ride just fine.

 

As did my old T with skinnies up front and Hursts in back. As well as the radials on my 54. 3 distinctly different cars, weights and tires. Our tire dealer who happens to be a good friend that we spend hundreds of thousands with each year told me the same thing. Had a guy in a new Vette drop some huge coin and retun a few minutes later demanding a refund and different tires. Would not believe it was the new concrete on I90. I had the same issue with my cheap tires in the same spot.

 

Fronts a 14 inch Radial T/As, not sure the width but they are pretty wide. 40psi fronts I would drop the pressure down to 32-34PSI....40 is way tooo much

Rear are Hurst Cheater slicks capped on 235-75-R15s at 35 psi, this mixture of radial and Hurst slicks may be causing and issue also. I know it's never a good situation to mix radials and bias.

Im thinkin of finding a narrower front tire and see if that helps

I wouldn't think a narrow tire would help. I was running narrow bias ply tires on my Dart and it would follow the road like crazy...it was no fun. Rebuilt the front end and put radials on the front and it was night and day difference.<!-- / message --><!-- sig -->

 

What kind of toe are you running? It sounds like it may have a little toe out, try setting to 1/8" toe in, see if that helps. And I've always heard never mix bias-plys and radials. Can't tell you why, but its just what I heard. I had a 98 SVT contour that I drove to college and when I got it it had 3 different tire brands (and 3 different speed ratings) on it, although all the sizes were the same. At speed the car felt real loose, like it was catching ruts, and like the suspension was loose, it was very weird. When it was wet out I felt like I was driving on ice. Put a new set of tires on it and the car felt solid as hell. Maybe tires are the blame?

 

I"d say that the mismatched tires are the big problem. And I agree with TexasDart in that 40 is way too much air pressure in those tires.

Just for a quick reference, drop the front tire pressure to 32 and stick (borrow if you have to) a pair of decent radials (tread depth and shape not necessarily looking) on the back and take it out and drive it and see how it drives.

Either way you go you are going to have to run 4 bias or 4 radial tires. And the first time you hit a Puget Sound area rain storm you had better pull off the road with those cheaters as the only place they will go is in the ditch. The least bit of water on the road will cause those to hydroplane before you can blink. I used to run N-50's on my 48 and won't run wide tires or tires without decent tread on it anymore because I have made too many trips to the bar ditch with it (3= Two in Texas and one here) in quick rain storms.

Still find a set of matching tires that you can bolt on the car and see what it does and then back off and decide what you want to do.

 

40psi in the front is high for tire pressure. Back it down to around 32-34 psi. Were these radials replaced new on your car or were they run on another vehicle ? Radials can act strangely once in a while especially if they are a tire that was run on a car that ran different camber settings than what your running , was run for many miles on an out of alignment suspension or had the rotation of the tire changed ( switched from the rt side to the lt ). Try a good set of radials that you know travel straight and see if the problem goes away.

 

Wide tires will pull a car around on the road, it is magnified by an uneven road. My car drives noticeably worse since I put 1" wider tires on it.

 

I'd second both of the above postings. If that doesn't work, check the alignment. Insufficient castor angle can also make the car follow ruts and other surface imperfections as there's less self-centering action.

 

From what I read here, you have radials front and rear. I think it likely that alignment will fix the problem. Could be a bumpsteer issue, but more likely fixed by a little caster and toe-in. Ply the local alignment guy with a beer or six, and he can probably tell you just what it needs. I also concur with the recommendations to go with nominal (32-35 psi) tire pressures.

 

My '91 Caprice wagon does the same thing. ya know why? The front wheels are off my lowered '98 Chevy truck. Different (read: wrong) offset. Throws the front track off. If I had 1/4 less backspace, it would be fine. But, DAMN it looks cool!

 

40 lbs in the front,too much,32 is fine and in some cases depending on the weight of the front 28lbs. 40 lbs of air in the front,all thats making contact with the road is the center treads of the tire.and running radial and bias mixed just doesn"t handle good on anything.

 

it's the square edge of the slicks in back

reduce pressure front and back,
32 front, 28 back

it will help some

 

Its a fact that if the front tires are wider than the rear tires ,It would cause what your talking about

 

I was going to say that too
try a narrower tire on front
even if the contact patch looks similar the slick will have a much smaller contact area on uneven (rutted) pavement

 

A rear end that's different width than the front end will cause it, too. Happens often with front clip swaps. Changing the offset of front or rear wheels can make a lot of diff.

 

No offense but that is fucking assinine. Chevy had trucks with DRASTICALLY different track widths for years, still do. Offset will not cause this.

 

PLus none of you seemed to read my replies about modern road construction? The tires shops locally report issues with various sizes and tread patterns. Like I said, I have had it happen with My daily, my hotrod and my 54. Carlas Minivan does it on certain sections of newer road.

 

Bad toe in/out will grab the lines in the pavement over a bias ply or width issue any day of the week. Do the toe and let 'er go.

Bob

 

I don't know what your roads are like in PA but I set the front ends on hundreds of Pontiacs during the early and mid 70's in both Texas and Washington and I don't think one will handle the caster you are saying you put in it. I ran matched caster side to side and usually 1/4 more positive camber in the left wheel to compensate for the camber in the roads.
I doubt seriously that his problem is alignment though.

I went to the web site and see that they use radial casings. I'd still throw a different set of tires on it that do drive good on the car that they are on, preferably from a Chevelle, Nova or Camaro. the size doesn't matter too much as you are only going to drive it five or ten miles and pull them back off anyhow. Just enough to decide that it either drives the same or something isn't right with the tire combination that you have now.

If it drives good in all situations with the other tires then swap the cheaters back on and see what it does. If it still drives good swap the fronts back on and go again.

I'd still check all of the steering linkage and suspension to make sure there isn't a worn or loose part but my bets are on the tire combination or some part of it.

 

I had an O/T 89 mustang 5.0 with 255/40/17's on the front and back. It had specific rate springs and all poly bushings. It handled like it was on rails, but after I got the new suspension done, I had it aligned. It followed every little crack in the road. I took it back and had them bring the tow in a bit, and it helped dramatically. A little bit of toe-in is better than a little bit of toe-out.

 

Great tech info located here, or google "tramlining"