The Ackermann effect / tire judder 20" vs 21"

[Speedy Gonzales]

Hi,

Currently I have 20inch Turbo Aero wheels on my Taycan and with this setup I almost never experience the Ackermann effect (tire judder) when full locking the steering wheel in slow corners.

I would really like to upgrade to the RS Spyder 21inch wheels, but with the wider and lower tires I'm worried the Ackermann effect will be present all the time when making sharp turns.. which I do a lot here in tight parking spaces etc.

I could use the current 20inch wheels in the winter (and have no problems with juddering) and the use the 21inch for summer (10 degrees celsius and up) if this means the warmer temperatures do not cause the juddering with 21inch wheels.

What is your experience with 21inch wheels compared to the 20inch and the Ackermann effect/juddering?
It would be a shame if I spent my money on 21inch and regret it if it means I will constantly be irritated with annoying juddering on sharp slow turns.

Hope to hear some experiences.
Thanks in advance

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[WuffvonTrips]

I've no experience to share, never having noticed it in any of my cars, including my Taycan on 20" and Cayenne on 21" summer tyres, but here's another recent thread on the topic...
https://www.taycanforum.com/forum/threads/judder-from-tyres-when-cold.17906

 

[Dabz]

I get it a LOT on my 21s, RS Spyder wheels. Only when it's cold and before the tyres heat up but it's quite disconcerting.

However the wheels look awesome so they're worth it IMO, I wouldn't change them

 

[Trogdors_Peasant]

In Seattle's weather we have no problem with this year round with the Conti All season tires it came with stock on the 21" Mission E's. I think we've experienced it maybe twice in 18 months on slick cement parking lots. We do lots of full lock turns getting in/out of our driveway and our neighborhood with mini traffic circles at intersections.

With summer tires like PS-4's it may be worse in cold weather.

Now our AMG SL63 on the same size wheels/tires but with PS-4 summer tires, you can't even look at it without it doing the most horrible Ackerman judders near full lock till they warm up.

 

[Murph7355]

There's another thread on here on it.

My car does it on full lock/slow manoeuvres. Rear steer seems to prompt it at the back too.

It's a "normal" thing and can be predicted when it will happen. Not worth, IMO, not having the best looking wheels due to it.

 

[hifi239]

I just want to clarify that Ackermann steering geometry was developed to solve the problem created by simple steering linkages that the inner and outer turn radii of the different wheels are different. Modern cars like the Taycan apply variants of this geometry. It doesn't have anything to do with tire width and applies just as well to antique 3-inch tires as it does to 12-inch tires. What you experience with wide tires is differential radius across each tire. That cannot be fixed by steering geometry and it wasn't contemplated by Ackermann. But I suppose you could call it the Ackermann effect. I.e. the 21" are so wide, that in sharp turns the inner and outer edges of each tire are trying to rotate at different speeds, but they cannot, so you will notice on slippery surfaces that the tire will jutter or pop.

I have 21's and 19's for my base RWD, and I much prefer the steering feel of the 19's, even at speed in shallow turns. It kills me because the 21" wheels look so much better.

 

[amelen]

I have it on my 20" wheels - just as much as I had it on my previous Panamara with 21's. As others noted only in cold weather and full lock - typically pulling out of my garage.

 

[Speedy Gonzales]

I get it a LOT on my 21s, RS Spyder wheels. Only when it's cold and before the tyres heat up but it's quite disconcerting.

However the wheels look awesome so they're worth it IMO, I wouldn't change them

Thanks for sharing your experience!

You mention you have it a lot but only when it's cold... does this mean it doesn't occur above like 10 degrees celsius? If that's the case I would just use the 20 inch in the colder months and the 21 inch in the warmer months..

 

[Paint_To_Sample]

Also would agree with the other poster that this has nothing to do with tire/wheel size and is specific to the fundamental geometry of the suspension.

It was very noticable on my 991.2 GT3…I have not experienced it even once on my Taycan GTS (w/ 21” wheels and Michelin PS4S for the sake of the conversation)

 

[Neptune]

At least I now know what its called!

 

[ciaranob]

Get it in Houston (I'm on 21's) even in summer months but only on full lock and esp if 90 deg turning across a lip on base of a ramped entrance (very specific I know , but TBH it really only occurs consistently at that one location!).

Altogether very rare otherwise and not ever on my mind except when I see posts like this

 

[Dabz]

Thanks for sharing your experience!

You mention you have it a lot but only when it's cold... does this mean it doesn't occur above like 10 degrees celsius? If that's the case I would just use the 20 inch in the colder months and the 21 inch in the warmer months..

yeh I’d say only below 10 degrees. Fortunately it’s been a very mild winter here so far. It’s only at very low speeds on quite a heavy turn of the wheel too, so where it originally bothered me a lot, it now doesn’t because I learned on here that it’s normal

 

[Wakesurfer]

Hi,

Currently I have 20inch Turbo Aero wheels on my Taycan and with this setup I almost never experience the Ackermann effect (tire judder) when full locking the steering wheel in slow corners.

I would really like to upgrade to the RS Spyder 21inch wheels, but with the wider and lower tires I'm worried the Ackermann effect will be present all the time when making sharp turns.. which I do a lot here in tight parking spaces etc.

I could use the current 20inch wheels in the winter (and have no problems with juddering) and the use the 21inch for summer (10 degrees celsius and up) if this means the warmer temperatures do not cause the juddering with 21inch wheels.

What is your experience with 21inch wheels compared to the 20inch and the Ackermann effect/juddering?
It would be a shame if I spent my money on 21inch and regret it if it means I will constantly be irritated with annoying juddering on sharp slow turns.

Hope to hear some experiences.
Thanks in advance

This occurs on a number of cars................maybe all of them? I had an H3 Hummer and it was more than prevalent on cold tires, warm tires, cold weather, warm weather, etc. Not sure why, but it was very pronounced on the H3. Otherwise I have noticed it on pretty much any car that we have owned. For me, it is just a physics phenomenon that I have pretty much learned to ignore. I would not let the decision to get 21s be impacted by Mr. Ackermann's shudder if I really like the look of the 21s. That's just me.

 

[Speedy Gonzales]

Thanks all!

I just made the decision to just go for the 21 inch wheels and placed the order.

I will use them for the warmer months of the year and the 20 inch for the colder months.

I’ll update this thread to share my experience when start using the new wheels ?????

 

[Wakesurfer]

Thanks all!

I just made the decision to just go for the 21 inch wheels and placed the order.

I will use them for the warmer months of the year and the 20 inch for the colder months.

I’ll update this thread to share my experience when start using the new wheels ?????

Yeah Baby!!!!!?

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