slow steering after upgrade to 215/45/17 tires

vti07 · 10-10-2008, 10:14 PM

Hi all,

I have just upgraded my tires and wheels from 195/65/15 - 15 x 6 to 215/45/17 - 17 x 7.

What I have noticed is that whereas the steering was very sensitive before, it's now very "slow" to respond.

Is this because of the wider contact patch on the road?

Changing tire pressure to compensate hasn't made any noticeable difference.

I'm running kumho kh11's at the moment.

What's the easiest way to restore the steering response (new tires or wheel alignment)?

Thanks.

708CvCSi · 10-10-2008, 11:33 PM

tire width definitely will affect steering response, just have to get used to it...My opinion is that your tires may have a softer sidewall as well. Some tires have softer sidewalls compared to other tires of the same size, manufacturer type etc...

vti07 · 10-11-2008, 03:15 AM

Thanks for that. Would having a tire with a stiffer sidewall help with the steering response or is that just better for cornering?

e60.deluxe · 10-11-2008, 03:34 AM

its possible its just the tires themselves...different tires will have different steering responses.

are you actually feeling a slower turn in from the same steering input or just that the wheel is heavy to turn?

gkit19986 · 10-11-2008, 03:52 AM

with the wider tires, you should have felt that you more grip.. if you take turns a lil faster, your tires wont schreech. but you would encounter a tiny bit of a harsher ride. a 45 ride profile isnt bad, just dont go below that, then you may damage the wheel if you hit bumps or pot holes. hope that helped.. it also depends mainly on the tire itself, the kumo it the lowest tire in its class? what is the speeed rating on the tire?
wheel algiment would only help with steering virbration.. but yes it is def recomended to do the wheel aligment.

vti07 · 10-11-2008, 04:58 AM

Thanks for all your replies. I've just driven the car again and it seems that the steering is heavier, rather than slower to turn in. (Yes, the car is definitely more grippy) I'll just get used to it. Next time, I'll look for a another brand of tire to see if there is any difference.

raybyduhbay · 10-11-2008, 04:17 PM

Ramp up the PSI to about ~45 or whatever the max rated psi is at. that should help you with a lil better steering response

drahgon · 10-11-2008, 06:52 PM

heavier makes sense, takes more effort to turn the wider tires... you'll get used to it.

ray · 10-11-2008, 07:48 PM

The tire/wheel package you've moved to presents a lot different profile to the road. A narrow 65-series tire is much more rounded at the edges and acts that much narrower as the effective contact patch is a lower percentage of its (lesser) total width than your new size. And new tires tend to feel light in the steering for this reason--they still have some profiling left to them at the edges of the tire.

Tire makers profile tires carefully to optimize their steeing feel and noise characteristics. As you wear a tire flat, you lose the benefit of this and the steering feels heavier and noise increases. When a tire maker lays some marketing buzzword on you like 'uni-Q technology' or some crap like that they are often just referring to whatever profiling techniques they employ at the moment--as if other makers don't...

This is usually pretty obvious when you replace a set of tires with a new set of the same design. It's amazing how much more civilized the new set feels. Unfortunately, this sensation is gone all too soon as the road wears the tire ever-flatter across the width of the contact patch (amongst other changes).

e60.deluxe · 10-11-2008, 08:30 PM

the contact patch is gonna be the same for the same PSI. the only way to reduce the size of the contact patch is to lighten the load on the tire or increase the PSI.

i think the grip of the tread design has more to do with it personally. at first i thought maybe that the new tires that are not broken in were not gripping thus needed more steering input. but as you clarified this was not the case..

ray · 10-11-2008, 09:02 PM

Quote:

Originally Posted by e60.deluxe

the contact patch is gonna be the same for the same PSI. the only way to reduce the size of the contact patch is to lighten the load on the tire or increase the PSI.

This is a pretty tired (no pun intended) and overused over-simplification. Yes, it will be the same area. But it will not be the same shape. It's the width of the contact patch I am referring to, not the total area bounded by it. But even more directly, it is as originally stated the profile the tire presents the road. A higher aspect ratio entails a larger radius at the the edge of the contact patch, giving a lighter steering effort by minimizing by weight jacking as you turn the wheel. The more pronounded edge of the lower-profile tire is forced into the ground by the caster of the steering system as you turn the wheel to a greater degree, providing more resistance to the steering.

As far as old vs. new, compare the shoulders of a worn-out tire to a brand-new replacement and the difference is visually obvious. If there is sufficient sidewall stability the edge of the used tire will be sharper, rather than the comparitively rounded shoulder of the new tire. And low profile tires inherently have more sidewall stability, allowing them to more effectively flatten the contact patch and sharpen its edge with wear.

e60.deluxe · 10-11-2008, 09:05 PM

Quote:

Originally Posted by ray

This is a pretty tired (no pun intended) and overused over-simplification. Yes, it will be the same area. But it will not be the same shape. It's the width of the contact patch I am referring to, not the total area bounded by it.

no, just saying that the contact patch gets bigger, its simplifing it, because most people talk about it in relation to handling, it helps with handling. saying that it stays the same area is less simple than that.

in anycase, i know all that, but the point is, i dont see how, when turning the wheel, a wider contact patch would resist more than a narrower one. when we say wider, its really still an elongated shape, but a wider tire makes it less elongated and more square shaped. a wider one would provide more lateral grip, but we are not talking about lateral grip. i dont see how it could HINDER pivoting. i would think that being more square shaped would, if anything, HELP pivoting, and the increase in lateral grip would HELP the car change direction quicker.

ray · 10-11-2008, 09:30 PM

The thing you're missing is the fundamental way a four-wheeled vehicle turns--and the role of caster in it. Just turning the wheels one direction or another will not affect turning of the vehicle. It will 'push like a dump truck', as circle track boys say. You have to tilt the front wheels in order to jack weight, allowing the load to be lifted from the inside rear wheel. The wider the tire, the wider the patch, and the longer the 'arm' formed by the width of the tire outside the pivot axis of the front tire. This magnifies the weight-jacking affect of the castor of the steering, jacking more weight and thus affecting more turning of the vehicle per degree of steering wheel travel, thus feeling heavier as you turn that wheel. Moving the front wheels out towards the fender lips (like a 25mm wheel offset) has the same effect, although to a greater degree.

And such, it's the same case on both points. The area matters not, it's the geometry of the entire system. You can't simplify the geometry of the contact patch down to area, because the area isn't involved in this phenomenon. It's the change in width, translating into a change in weight-jacking, translating into a change in feel and effort at the steering wheel. You further lessen the weight-jacking effect by using a tire with a more rounded edge (higher profile). The edge is not as effectively forced into the ground by the castor of the steering, posing less resistance to the turn of the steering wheel.

HsOffRoad · 10-13-2008, 05:55 PM

More than likely, your slower turn in is caused by a change in wheel offset when you went to the 17's. This changed your scrub radius, which in turn effected your turn in. I know this means nothing to most people who don't have experience with suspension setup on race cars, so rather than try to explain the scrub triangle and its effects, if you are interested, google "ackerman angle, steering axis inclination, and scrub radius" and read up. Otherwise, just know its probably your wheel offset that is effecting your turn in most.

Hans

10-10-2008, 10:14 PM	#1 (permalink)
vti07 Junior Member Join Date: Sep 2008 Location: Australia Posts: 18 iTrader: 0 / 0%	slow steering after upgrade to 215/45/17 tires Hi all, I have just upgraded my tires and wheels from 195/65/15 - 15 x 6 to 215/45/17 - 17 x 7. What I have noticed is that whereas the steering was very sensitive before, it's now very "slow" to respond. Is this because of the wider contact patch on the road? Changing tire pressure to compensate hasn't made any noticeable difference. I'm running kumho kh11's at the moment. What's the easiest way to restore the steering response (new tires or wheel alignment)? Thanks.

10-11-2008, 08:30 PM	#10 (permalink)
e60.deluxe Senior Member Join Date: Apr 2007 Location: Lake Forest, CA Age: 23 Posts: 5,906 iTrader: 3 / 100%	the contact patch is gonna be the same for the same PSI. the only way to reduce the size of the contact patch is to lighten the load on the tire or increase the PSI. i think the grip of the tread design has more to do with it personally. at first i thought maybe that the new tires that are not broken in were not gripping thus needed more steering input. but as you clarified this was not the case.. Last edited by e60.deluxe; 10-11-2008 at 08:32 PM.

10-13-2008, 05:55 PM	#14 (permalink)
HsOffRoad Senior Member Join Date: Feb 2007 Location: Media, PA Posts: 731 Hans Scherer iTrader: 0 / 0%	More than likely, your slower turn in is caused by a change in wheel offset when you went to the 17's. This changed your scrub radius, which in turn effected your turn in. I know this means nothing to most people who don't have experience with suspension setup on race cars, so rather than try to explain the scrub triangle and its effects, if you are interested, google "ackerman angle, steering axis inclination, and scrub radius" and read up. Otherwise, just know its probably your wheel offset that is effecting your turn in most. Hans Last edited by HsOffRoad; 10-13-2008 at 06:20 PM.

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10-10-2008, 11:33 PM	#2 (permalink)
708CvCSi Senior Member Join Date: Jul 2008 Posts: 257 iTrader: 0 / 0%	tire width definitely will affect steering response, just have to get used to it...My opinion is that your tires may have a softer sidewall as well. Some tires have softer sidewalls compared to other tires of the same size, manufacturer type etc...

10-11-2008, 03:15 AM	#3 (permalink)
vti07 Junior Member Join Date: Sep 2008 Location: Australia Posts: 18 iTrader: 0 / 0%	Thanks for that. Would having a tire with a stiffer sidewall help with the steering response or is that just better for cornering?

10-11-2008, 03:34 AM	#4 (permalink)
e60.deluxe Senior Member Join Date: Apr 2007 Location: Lake Forest, CA Age: 23 Posts: 5,906 iTrader: 3 / 100%	its possible its just the tires themselves...different tires will have different steering responses. are you actually feeling a slower turn in from the same steering input or just that the wheel is heavy to turn?

10-11-2008, 03:52 AM	#5 (permalink)
gkit19986 Senior Member Join Date: Sep 2008 Location: Westchester NY Posts: 1,086 mike iTrader: 4 / 100%	with the wider tires, you should have felt that you more grip.. if you take turns a lil faster, your tires wont schreech. but you would encounter a tiny bit of a harsher ride. a 45 ride profile isnt bad, just dont go below that, then you may damage the wheel if you hit bumps or pot holes. hope that helped.. it also depends mainly on the tire itself, the kumo it the lowest tire in its class? what is the speeed rating on the tire? wheel algiment would only help with steering virbration.. but yes it is def recomended to do the wheel aligment.

10-11-2008, 04:58 AM	#6 (permalink)
vti07 Junior Member Join Date: Sep 2008 Location: Australia Posts: 18 iTrader: 0 / 0%	Thanks for all your replies. I've just driven the car again and it seems that the steering is heavier, rather than slower to turn in. (Yes, the car is definitely more grippy) I'll just get used to it. Next time, I'll look for a another brand of tire to see if there is any difference.

10-11-2008, 04:17 PM	#7 (permalink)
raybyduhbay Senior Member Join Date: Mar 2007 Location: Bay Area Posts: 1,086 Ray iTrader: 10 / 100%	Ramp up the PSI to about ~45 or whatever the max rated psi is at. that should help you with a lil better steering response

10-11-2008, 06:52 PM	#8 (permalink)
drahgon Senior Member Join Date: Mar 2007 Location: Winnipeg Posts: 2,341 Daryl iTrader: 3 / 100%	heavier makes sense, takes more effort to turn the wider tires... you'll get used to it.

10-11-2008, 07:48 PM	#9 (permalink)
ray Senior Member Join Date: May 2008 Posts: 1,234 iTrader: 0 / 0%	The tire/wheel package you've moved to presents a lot different profile to the road. A narrow 65-series tire is much more rounded at the edges and acts that much narrower as the effective contact patch is a lower percentage of its (lesser) total width than your new size. And new tires tend to feel light in the steering for this reason--they still have some profiling left to them at the edges of the tire. Tire makers profile tires carefully to optimize their steeing feel and noise characteristics. As you wear a tire flat, you lose the benefit of this and the steering feels heavier and noise increases. When a tire maker lays some marketing buzzword on you like 'uni-Q technology' or some crap like that they are often just referring to whatever profiling techniques they employ at the moment--as if other makers don't... This is usually pretty obvious when you replace a set of tires with a new set of the same design. It's amazing how much more civilized the new set feels. Unfortunately, this sensation is gone all too soon as the road wears the tire ever-flatter across the width of the contact patch (amongst other changes).

10-11-2008, 09:30 PM	#13 (permalink)
ray Senior Member Join Date: May 2008 Posts: 1,234 iTrader: 0 / 0%	The thing you're missing is the fundamental way a four-wheeled vehicle turns--and the role of caster in it. Just turning the wheels one direction or another will not affect turning of the vehicle. It will 'push like a dump truck', as circle track boys say. You have to tilt the front wheels in order to jack weight, allowing the load to be lifted from the inside rear wheel. The wider the tire, the wider the patch, and the longer the 'arm' formed by the width of the tire outside the pivot axis of the front tire. This magnifies the weight-jacking affect of the castor of the steering, jacking more weight and thus affecting more turning of the vehicle per degree of steering wheel travel, thus feeling heavier as you turn that wheel. Moving the front wheels out towards the fender lips (like a 25mm wheel offset) has the same effect, although to a greater degree. And such, it's the same case on both points. The area matters not, it's the geometry of the entire system. You can't simplify the geometry of the contact patch down to area, because the area isn't involved in this phenomenon. It's the change in width, translating into a change in weight-jacking, translating into a change in feel and effort at the steering wheel. You further lessen the weight-jacking effect by using a tire with a more rounded edge (higher profile). The edge is not as effectively forced into the ground by the castor of the steering, posing less resistance to the turn of the steering wheel.