[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]
Re: Tires causing torque-steer
I'm watching. It is possible that there is a tire/vehicle interaction
that may be causing your torque steer. You say that you noticed this
shortly after installing the Hakkas. I would start the diagnosing by
putting the 16" Yokos back on the car and seeing if the torque steer
occurs. If it does, then I would say it's the Torsen system acting
up and transferring torque to one side. If not, then try running the
Hakkas in reverse rotation by putting the rights on the left side and
vice-versa (don't worry about the directional pattern). If the torque
steer changes direction or goes away or even reduces in severity, I
would say it's a characteristic of the tread patter giving you
problems. If it doesn't change direction, then the tires have a
conicity problem. Is anyone else in q-land experiencing this on their
Another test I would suggest while the Hakkas are on the car is to
see if the car pulls the other direction under braking. This will
determine if the tire tread pattern is torque sensitive.
If the vehicle pulls at constant velocity, it can be attributed to
RAT - Residual Aligning Torque. It's defined as the level of aligning
torque at the slip angle where the lateral force of a tire is zero.
What this means is that if a radial tire is allowed to roll at zero
lateral force, the tire is not at zero slip angle which creates a
moment (or aligning torque) which translates to pull. This phenomena
is characteristic of radial tires. There are two components that
relate to the level of RAT, one is conicity and the other is
plysteer. Conicity is the lateral force generated by the tendency of
a tire to roll as if it were cambered to the road surface. The force
will not change directions when rotational direction is reversed.
Plysteer is the lateral force generated by the tendency of a tire to
roll as if it had a slip angle. Plysteer RAT is heavily influenced by
the tread patter design and_will_ change when rotational direction is
reversed. This is a very brief description and I'll understand if it
doesn't make sense.
In summary, swap rights and lefts. If it pulls in the same direction,
it's a conicity problem (tire manufacturing problem like off-center
belts). I would swap fronts and rears. If it pulls in the opposite
direction, it's a plysteer problem (tread pattern design). Nothing
you can do about that except get different tires.
I mentioned above that it may be a tire/vehicle interaction thing.
When going to narrower 15" tires from the wider 16", the footprint
gets longer which increases the pneumatic trail. Pneumatic trail is
the distance between the center of the contact patch and the
"center-of-gravity" of the contact area pressure (or moment arm).
This has an affect on RAT sensitivity.
Let me know the prognosis. HTH!
> Hi Guys: I hope Rudy from Ohio is watching... My car torque-steers with my
> new Hakka 1's. I noticed this shortly after installing them. The car went
> dead straight on the sumer tires (Yoko A-509s on 16" rims). The Hakkas are
> on the 15" OEM rims and when I step on the gas, the car pulls to the left.
> Get off the gas and it settles out pretty straight. My tire shop finally
> got a replacement tire in yesterday. They put it on the left front and no
> improvement. The shop said maybe it is a 'characteristic of these tires'.
> I can't believe that! I don't think it is an alignment problem since the car
> went straight on the other tires. I'm thinking of rotating tires around to
> try to isolate.
> Any opinions?
> Ralph Poplawsky
> '91 200TQ (keeps coming back to the same place)