Melchior

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Melchior

My message got erased when I added the gremlin?!?

On my 944S2, I increased the tire width from 205mm to 225mm and now they seem to make the car veer left or right when I drive over mild depressions in the road. Should I increase the front toe-in to fix this and how much?

Mark Parker

Wider tires have a natural tendancy to want to follow irregularities in the road surface. I wouldn't see the need for changing toe, providing it's within specs now.

Melchior

I understand what you are saying. However, it seems like the 944 has a tendency to have a very 'squirley' steering. I believe they did that for race purposes but regular driving, even down the expressway, it becomes a chore to chase the nose of the car while driving. I have replaced all the normal wear components on the car such as: strut mounts, tie rods, ball joints, strut brace, new swaybar bushings. I even checked the steering rack for any wear or play but found nothing. I noticed the same steering tendency in my '87 951 that I owned up till two years ago.
If I doubled the toe-in, it seems like I would reduce the 'hunting' tendency of the front wheels.

C5Driver951

Try increasing your caster. I wouldn't run too much toe-in as it will just cause your tires to wear faster.

Danno

" However, it seems like the 944 has a tendency to have a very 'squirley' steering."

Wider, lower-profile tires will always make this worse. It's like a law of physics. Actually, it is due to physics. Part of it is due to the increased moment-arm the outside/inside edge of the tire has with the steering axis of the strut. The further away the edge of the tire is from the steering-axis, the more twisting force you'll have in the steering from the same size bump hitting the edge of the tire.

The other physical property is the contact time on the ground for any piece of the tire. A wider tire will have a narrow, rectangular shaped contact patch compared to a narrower tire, which will a more square contact patch. Then when any given block on the tire first rolls onto the ground to be part of the contact patch, it will spend less time touching the ground in a wide tire than a narrower tire. How this affects the steering feel and stability is beyond the scope of this post, but it does contribute.

As for alignment, toe should be a little less than stock since wider tires are more sensitive to that adjustment as well. With the same toe as stock, you most likely will be wearing the outer edges faster compared to the stock tire. You can add about 1-degree move caster than stock with the adjusters and this should help stability quite a bit.

Melchior

Thanks, I don't know too much about the affects of changing alignment specs. This explains a lot. I will most likely change the caster.

gleamingred944

I've got 215's all around, but I also got my baby aligned by the best mechanic in town, not just any old alignment shop, and there's nothing squirrelly about it - it's solid as a rock on smoth pavement and rough. I know that people often use different alignment for track than for everyday roads - you definitely ought to check alignment with an expert.

Don't forget tire pressure either - makes a big difference and the best varies greatly with tire construction.