My rear tires keep getting diagonal scuffing. I read that it could be the struts so I had them replaced about 60k ago and now its doing it again.

My question is: does anyone know if you can adjust the toe in or out on the rear of these cars? Oh its a 2007 Fit, sport.

Thanks.

 

What is 'diagonal' scuffing?And assuming its scuff marks that 'angle from one side to the other, are the diagonals the same on botgh sides or opposite as angling inward and backward to the rear on both sidces. either /\ or \/ or // or \\ ?

 

Its a wear pattern on the tire that gives the tire a sort of cork screw look. If you were to look straight down on the tire from top, with your head pointing to the front of the car, it is a wear pattern starting from the inside of the tire, going diagonal and back as it goes across the tire. Clear as mud?

There are good examples if you do a search on Diagonal scuffing on google and look at the images.

To be honest I dont know if the diagonals are the same from side to side. I saw the passenger and then verified the driver side had it too. New tires are already on the car as of this morning.

 

I went to the tire diagonal scuffing sites and the motorcycle site had the best pics. In 60 years of tire efforts I've never seen that pattern. They suggested there was a toe problem and I agree to an extent; I beieve there is something loose in the rear suspension that allows the tire to change toe as the Fit is turning. In that case I would expect the tires to show opposite diagonals on each side such as this: \ / indicating possible decreasing toe as the Fit turns, on the outer tire. I don't think the inner tire is changing toe. So the 'diagonal scuffing' occurs only on one wheel at a time depending on the corner direction.
Wild theory, huh? If thats true your new tires are just as much in risk.
Now for another thought: it could be the tire construction.. but I like the changing toe better. As a first thought check the axle flange attached to the 'frame' and any trailing links. That would shift the axle, and toe, depending on where thed maximum load is applied. In this instance thed outer tire. It may not be easy to locate such movement so you may just have to add a fretted washer to the attachment to ensure the flange is tight to the body. You wikll probably need a good competent suspension alignment mechanic to check these. Or others he may see.
The hub may be flexing, the wheel may not be tight to the hub, all of these may be the problem. Then, too, my observation may just just as WAG as any others. Certainly it is an interesting problem though; when you find an answer be sure and lets us posters know, especiaslly those of us who didn't even know such a problem existed.
good luck

 

The problem lies in the very basic suspension design. Because its a torsion beam any time the suspension compresses you gain a large amount of toe in. Unfortunately the toe is 'unadjustable'. You can adjust it with shims, but it would have to be a DIY project and lots of trial and error. Very few alignment shops if any will touch that kind of thing.

 

The Fit rear suspension ear axle is a shallow 'i________l that doesn't change toe very much as it rotates the ends up and down depending on the compression of the springs. There is a little difference in rotation between the two sides due to torsion of the horizontal portion. The only way we see the diagonal scuffing occur is related to the axle not being solidly to thje body by the clips/flanges at the 'corners'. In that case the axle shifts horizontally and that necessarily changes the toe. That wear pattern diagonal is why we suspect the toe is changing repeatredly in the corners. Certainy more than with a Porsche or Corvette rear suspension.
It would not help to realign the toe if it can flex; doing so might make the diagonal scuffing worse.
Its not too difficult to alter static toe - we've done it a couple times when it hads to be done - but it is time-consuming as all get out, shilling, meassuring, shimmimg, measuring, until its right.
Both our motorcycle and car troops think something is loose or distorting in your suspension or the body fixed attachment. Our motorcycle guys have seen the diagonal wear pattern and say it was due to flexing in the rteasr suspension arm to the rear tire.
And fior what its wortth we think its really strange and would be fun to work on.!
still wish you good luck.

 

When raising a rear wheel with a bottle jack I noticed that the wheel appeared to point inward... It seems the flex in the torsion beam is what causes it.

 

Agree to disagree I suppose. If you have -2 degrees of camber in the back with 0 toe. With the swing of the torsion beam it doesn't move straight up and down. It travels along the radius of the bushing to knuckle length. If you were able to move the suspspension 90degrees on the arc of the suspension arm you would then have 2 degrees of toe in.

Why do you think lowered cars have way more toe in then at stock height?

 

^ Yup, the toe changes with rear suspension compression/extension with our rear suspension design.

It looks more like \_______/ than it does like |________|

 

So that's why our tire's look funny.

 

A local freak thought I had changed the camber on my rear wheels the first time she saw my car after I'd installed Swift springs and Enkei RPF1s... It did look like I had done that... It may be caused by the lower offset number (41) and wider wheel rims.. It doesn't look that way with 45 offset and 6 1/2 inch Kosei wheels and Buddy Club coil overs set at the highest position I can safely use.

 

Have you tried the coat hanger modelling? Fronts have more toe when the suspension is compressed but not the rears. The hubs and rear axle are rigid and as long as the axle remains square to the frame there is almost no change in toe. IIf the hub was pinned so a lateral link could change toed then you're right. As long as the axle is firmly fixed and the hub is fixed to the axle and the rotation is fixed just how does the toe change? Camber yes indeed. We still think the problem is a loose axle.
Refer to 18-4 in the shop manual and find the lateral motion. Unless the axle 'bends' there is virtually none.

 

I do all of my own alignments with the string method (same a race teams) and there was a significant amount of toe in when it was lowered. I will have to draw a diagram to explain what I am talking about.

 

I had the same problem with the rear tires cupping. They then of course roar, which makes it extremely noisy in the car. I got shims from the SPC? site. My local alignment shop said their Hunter alignment equipment would work with those shims. My left rear was toed in badly; the right was within spec. After the shim was installed they both showed in spec. The proof will be when I get tires next month. I pray the noisy tires are a thing of the past and will not return. You can really see those diagonal patterns on the tire when you drive into a garage with a dusty floor. The cupped areas will not appear dusty like the rest of the tire, which readily shows them up.

 

AFAIK toe should not change on twist beam rear unless the suspension is under load due to twisting forces in the beam. Toe should remain 0 (or unchanged) at rest regardless of change in ride height.

I understand what SHG_Mike is saying IF there the rear wheels had x degrees of camber and the suspension was lowered, that angle would increase, but isn't camber and toe set close to 0 in an unmodified axle?

 

Tires cupping is not the same as diagonal scuffing. Usually that problem is a result of worn shock absorbers.
How mAny miles on your Fit?

 

Good thinking. Yes if ONE shock is compressed the toe and camber and caster will change; changing the effective length of that shock will twist the axle as you say. If the shock ins't compressed , ie no load, I couldn't easily measure the toe change when we lifed the wheels when the car was off ground.
If you measure toe change not under load suspect the axle locating fixtures.
when both sides are lowered, we see change in camber and caster due to the axle 'arm lift changing the shock length but not enough toe to matter.
For thodse who need to shim to get toe its a tough job in the rear; often re-assembling several times is needed.

 

Camber is set around 1-1.5 negative thus creating a problem. It doesnt even have to be a lowered car, just a car with a bunch of crap in the back that makes the rear of the car sag (we've all seen it) If the camber is 0 then yes there will be no toe change. The problem is the rear wheels dont go straight up and down in its travel it arcs along the path of the rear beam radius. So if there is any camber that will slowly be translated to toe the more the beam travels up.

 

The I beam rotates in an arc and shouldn't have an effect on camber. It was obvious that my wheels were cambering inward at the top with 7"x 15" 41 offset wheels and even more with 16"x 7" 38offset wheels.. It isn't obvious with the 16"x6 1/2" 45 offset wheels that I now have on the car.. That leads me to believe that the swing arms from the I beam to the wheels flex with wider wheels and low offset numbers.

 

Ah well that makes sense then, I did not know the axle had factory camber dialed in. Thanks!