"Tripper" (tripe46)
11/09/2015 at 13:27 • Filed to: None
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"Tripper" (tripe46)
11/09/2015 at 13:27 • Filed to: None | 1
| 9 |
!!!error: Indecipherable SUB-paragraph formatting!!! , but I could not get a solid answer. I ordered a set of winter wheels/tires, then got a call saying that the wheels are not available in the silver with the stock offset (et45) for my S3. Silver is only available with a 35mm offset, which would bring me to a 2cm change overall.
I read a lot about offset, I know what it is, how to measure for it etc...However, I could not find out any solid info on how much change is too much. I also could not find much info on how offset changes the steering feel/handling other than the fact that it does...
So being the conservative enthusiast that I am, I decided to go with the proper fitment in black. I’m also a little extra gun shy when it comes to wheel fitment as my buddy had 4 sets for his BRZ and the car felt drastically different with each set.
Either way, I’m still curious about fitment. How much is too much change in geometry before the car drives differently or parts start to wear abnormally?
Aaron M - MasoFiST
> Tripper
11/09/2015 at 13:37 |
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In terms of wear, it depends on how wide the wheels are already and how stout the wheel bearings are. In general, 7-10mm in either direction is what you should max out at provided the wheels are the same width. Wider wheels need lower offsets to keep the same balance on the hub, since offset is a relative measure (from the centerline) and wheel width is an absolute one.
As far as geometry, you’re altering your scrub radius by altering the tire offset. This will affect things like tracking and torque steer, but the big thing is that it will make the steering feel completely different. How much so is going to differ on every car, based on how positive or negative the scrub radius already is and how the power steering is tuned for it. In general, modern cars have a negative scrub radius (due to ABS and tracking/stability under panic braking), in part because they have high offset wheels. Going to lower offset wheels will bring your scrub radius closer to zero, and while that reduces some of the torque-steer minimizing effects of negative scrub radius, it also shouldn’t affect steering effort too much as long as your new scrub radius is not more positive than your old one was negative. It will make panic braking more squirrelly.
RamblinRover Luxury-Yacht
> Tripper
11/09/2015 at 13:37 |
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If you’re asking for one drop-dead line for too much change, I don’t think there is one. Different cars have different camber change under steering, different caster, different pin position (which affects all that and bump steer), different design amounts of toe, and even different response in their power steering system. What would make for a little bit of grippiness on one car could turn another car into a lurchy, steering-fighty, bump-steering atrocity. Is it probably possible to make a predictive equation? Probably. Would it require more info than you could get unless you ran a tire shop? More than likely.
I wouldn’t recommend much over 2CM just because that will shift the point you pivot on on your tire a fairly large percent compared to the width of your contact patch. That said, it’s probably okay at anything below that.
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Tripper
> RamblinRover Luxury-Yacht
11/09/2015 at 13:45 |
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This is great! If it were just a few mm’s I probably would not have even asked the question. At 2 cm I thought that I might be ok, but I figured that I ought to play it safe as wheels would be a pain to return (if they would even take them back).
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Tripper
> Aaron M - MasoFiST
11/09/2015 at 13:47 |
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Thanks! Yea too many unknowns for me, glad I stuck with the stock offset.
DrScientist
> Tripper
11/09/2015 at 13:52 |
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something, something, scrub radius, something.
that’s all i know. browse rennlist.org in the 928 forum. they’ve reviewed this topic a bunch. the 928 was/is known for its superb handling characteristics at extremely high speeds. however, because of technology in wheel and rubber, the factory wheels/tires look very dated compared to what’s in style today.
the discussions on rennlist cover how changing to a larger diameter wheel, and changing offset, while modernizing the look, may affect handling characteristics.
sorry, i dont even remember which way is good or bad, or no difference. surely its no difference to me as i’m rarely into triple digits, and need to replace some steering rack bushes before i even start commenting on handling characteristics.
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Tripper
> DrScientist
11/09/2015 at 13:59 |
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Haha your response is still helpful! The fact that it’s almost impossible to tell until you get the wheels on the car is enough for me to play it safe.
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DrScientist
> Tripper
11/09/2015 at 14:02 |
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:)
aaron M mentions scrub radius also, and his comment is much more informative than mine. do some research on how scrub radius affects handling, and i’m sure you’ll get closer to the answers youre looking for.
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Tripper
> DrScientist
11/09/2015 at 14:06 |
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Will do I plan on swapping my summer wheels for something lighter/nicer in the future. I will do more homework before then.
Tohru
> Tripper
11/09/2015 at 14:11 |
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Should’ve went Japanese kei-style and went with 17x4 wheels and snow tires.