Excessive bump steer

I just had my summer tires put on and I noticed an excessive amount of bump steer while driving, it's practically a fight with it and it's pretty annoying. I had forgotten about it but now I remember it doing this before I put the winter tires on in December. Now I never changed the suspension or any of its components, and the tires are 205/55R16 which is the stock tire size and have been the same tires I've had for it since I've bought the car. I feel like it gets worse over time. What would cause them to do this and how can I correct it? I've had it aligned in September at Subaru, if anyone wants to know the measurements I can tell you. By the way the car is a 2007 Subaru Impreza 2.5i Special Edition.

If it's something relating to suspension geometry, you really can't do anything about it...

Have you checked the tire pressures all around ?
Loose tie rod end ? (inner and outer)
Worn out bushings which could cause toe-out or toe-in under load ?

Your alignment could be off too:

Toe-in on a car will increase stability but it will also make the car ''track'' more, i.e. it will tend to follow lines in the pavement and be very ''tight'' and a little harder to steer
Toe-out will decrease stability but make the car more responsive. It will NOT follow lines in the pavement and be somewhat ''twitchy'' but VERY responsive and easy to steer

did you check the tire psi?

but LOL Bumpsteer on a stock Impreza with balloon tires..

OldschoolZ have a very good point!


in my case it's mostly my power steering delete + larger offset wheels that did it..

Saggy springs are the first thing that comes to mind.

Is your car lowered on coils?

It's going to the dealer tomorrow for an unrelated thing but I'll ask them to check for anything that might be loose/getting tired. Too tired and cold to do it at home lol anyway now that I think about it, it's gotta be a tire issue because it wasn't acting this way on the winters, and I do remember the summers started to do that near the end of last summer

Seeing as that the summers had just been put on I don't see how it could be a tire pressure problem since they weren't mounted beforehand, and the valve stems had been replaced as well. Another possibility, maybe a long shot, is that the rear shocks are very recent and the front shocks haven't been changed yet, so maybe it upset the balance a bit, though the fronts aren't leaking and the front end doesn't feel too soft yet. If I were to push the front end down by hand it's still fairly stiff. And like I said it's the stock coils and springs, nothing has been changed in the suspension. I'll have them check the sway bar bushings, links, ball joints, anything that might be on its way out that can be causing this pain in the ass. I swear the Aveo I drive for work is almost more fun to drive at the moment lol

oldschoolZ said:

Your alignment could be off too

Click to expand...

It had been aligned about 6 months ago, and I haven't hit anything or done anything to make it get out of alignment. Being an AWD, I'm pretty sure after 6 months of driving the AWD light would've turned on and the car would be in limp mode. As for what the measurements are, this is what Subaru had done:

Left front: -0.1 camber, 2.6 caster, 0.00 toe
Right front: -0.2 camber, 3.2 caster, -0.01 toe
Front: -0.01 total toe, 0.00 steer ahead
Left rear: -1.1 camber, 0.02 toe
Right rear: -0.9 camber, 0.05 toe
Rear: 0.06 total toe, -0.02 thrust angle

KRBissonnette said:

It had been aligned about 6 months ago, and I haven't hit anything or done anything to make it get out of alignment. Being an AWD, I'm pretty sure after 6 months of driving the AWD light would've turned on and the car would be in limp mode. As for what the measurements are, this is what Subaru had done:

Left front: -0.1 camber, 2.6 caster, 0.00 toe
Right front: -0.2 camber, 3.2 caster, -0.01 toe
Front: -0.01 total toe, 0.00 steer ahead
Left rear: -1.1 camber, 0.02 toe
Right rear: -0.9 camber, 0.05 toe
Rear: 0.06 total toe, -0.02 thrust angle

Click to expand...

C'est justement... t'a fait l'alignement voila 6 mois... l'hiver c'est tres dure sur la direction d'une voiture... je retournerais faire vérifié l'alignement etre toi.

la forme, grosseur et psi des pneu a rien rien a voir avec le bumpsteer a proprement parler.

Du bumpsteer c'est que le toe change dans le range de mouvement de la suspension dans une géometrie donné........et non pas que le steering "shake" quand tu pogne un trou/bosse.

balljoint et tie-rod end peuvent etre les seul coupable.

les piece defect sont les meme qu'un suspension qui a besoin de remplacé des piece...mais la définition est différente.

Front caster is a bit weird

caster de chaque côté sont rarement les mêmes. si c'est ce que tu trouve weird

Sur mon truck c'est ,5deg de différence le chiffre a atteindre(+ou- 1deg) et peut avoir jusqu'a ,75deg de différence max entre les 2 roue.

2,6 c'est un peu bas ..mais si c'est dans les spec c'est ok.
Avec les powersteering qu'on a de nos jour, le caster pourrais etre plus grand que ca.

maxpat82 said:

la forme, grosseur et psi des pneu a rien rien a voir avec le bumpsteer a proprement parler.

Du bumpsteer c'est que le toe change dans le range de mouvement de la suspension dans une géometrie donné........et non pas que le steering "shake" quand tu pogne un trou/bosse.

balljoint et tie-rod end peuvent etre les seul coupable.

les piece defect sont les meme qu'un suspension qui a besoin de remplacé des piece...mais la définition est différente.

Click to expand...

T'as raison, je savais pas comment l'expliquer d'une autre facon comment la voiture comportait, mais il avait des symptomes similaires quand il roulait sur les bosses. Le volant tournait tout seul et forcait, mes bras etaient fatigues lol en tous cas, le probleme etait reelement parce que c'etait trop froid pour les pneus d'ete pour "travailler" proprement, et les pressions etaient trop eleves

J'ai baisse les pressions par 5 livres et c'est beaucoup ameliore, maintenant le "sidewall" travaille plus et j'ai plus de "contact patch". J'ai demande a des mecaniciens et ils ont tout dit la meme chose, c'est pas assez chaud pour les pneus.