Lost on-center feel with bigger tires

sd_iconoclast

Registered User
A while back, I replaced the stock 16 inch wheels and tires on my '89 SC with 17" wheels and tires. When I did, most of the on-center feel in the steering went away. Is there somethin I can do about it?
Has anyone else experienced this?
My new wheels and tires are 17x9 rims with 255/50ZR17 tires.
 
If you haven't had an alignment done recently, it couldn't hurt.

No matter what, the wider tires are going to wander a bit more than the stock tire size, as they tend to "grab" grooves/ridges/etc. in the pavement.

-Rod
 
If / when you're getting an alignment done, have them put in as much positive caster as possible. This helps the straight-line tracking. But as Rod said, the wandering is characteristic of most wider and lower profile tires, especially if they have a squarish shoulder.


cheers
Ed N.
 
I took the car to the alignment shop right after I put on the new tires.
I asked them to put in as much positive caster as they could. I read that this would help. They said that they were not able to put in much more positive caster than stock. The car sure did not feel any different after they were done with it.
How much more caster can be added over stock?
Would you expect it to make a difference that I can feel?
Is there something I can buy that will increase the max caster that can be put in?
 
My guess is they either didn't know what they were doing, or didn't want to try it. There should be quite a bit of room for Caster adjustment on our cars.

FRONT CASTER
Caster is adjusted by moving the tension strut relative to the front sub-frame. Loosen nuts securing strut to sub-frame and adjust caster by running the nuts in appropriate direction until desired setting is achieved. The setting should be locked by holding adjusting nut and torquing locknut to 117 ft lb .
 
The amount of available caster adjustment will vary from car to car. Generally speaking, you want to get it maxed out, while keeping it as close to equal as possible from side to side. Do you know what the caster spec was on your car after the alignment was done?

From what I've seen, 5.5 to 6 degrees is usually the most you can get out of an MN-12 without modifying any adjustment points ... I'm not sure if there is something that can be done to gain any additional positive caster adjustment.


cheers
Ed N.
 
fast Ed said:
From what I've seen, 5.5 to 6 degrees is usually the most you can get out of an MN-12 without modifying any adjustment points ...
I just had my alignment done 2 days ago. I gave the shop specific settings for everything, and the tech told me the +5.5 deg castor I asked for was about all he could get (and commented that was pretty typical for MN-12s).

My advice is to give the shop specific targets to hit (the theory being you get a more accurate alignment job done). The OE specs are actually ranges and IMO careless techs use a "good enough - it's in range" approach.

sd_iconoclast said:
A while back, I replaced the stock 16 inch wheels and tires on my '89 SC with 17" wheels and tires. When I did, most of the on-center feel in the steering went away. Is there somethin I can do about it?
Has anyone else experienced this?
Yup, we all do. You might want to try a little more toe-in in the front.
 
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