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Cal-look/High Performance => Technical stuff => Topic started by: Glauco on July 12, 2022, 09:36:24 am



Title: rack and pinion question
Post by: Glauco on July 12, 2022, 09:36:24 am
ok, so hear me out.
I'm in the process of sourcing al the parts for a rack and pinion conversion. I just prefer the predictability of a rack and pinion over the old steering box.
But in my quest to find al the parts it seems that the rack and pinion of a polo 86c is the way to go because the connecting rods are longer and prevent bump steer. witch I understand, BUT:
why do all the big cars have the rack and pinion setup were the rods connect to both the outer ends of the rack? porsche has it, the newer vw's have it. Porsche 924 en 944 that see a lot of trackdays tend to use a golf MK1 R&P because of the shorter steering ratio. Hell, even the mazda guys upgrade the first gen RX7's to golf MK1 R&P//
I understand dat the rods are at an angle on the spindles of a beetle, but this can be overcome with a bump steer kit?
is there an other reason I don't see why aircooled folks prefer the polo rack?

thank you,
glauco


Title: Re: rack and pinion question
Post by: Eddie DVK on July 14, 2022, 06:38:34 am
The only thing I can think of is that the Polo rack fits under the fuel tank, and maybe the golf not.
You have to ask Alex, he sells the brackets on here, maybe he know this.


Title: Re: rack and pinion question
Post by: Glauco on July 14, 2022, 07:13:45 am
The only thing I can think of is that the Polo rack fits under the fuel tank, and maybe the golf not.
You have to Alex, he sells the brackets on here, maybe he know this.

I found a plausible explanation:
the main reason is that in a golf (and in a Porsche and ...) the lower control arms are almost the exact same size as the tie rods, thus it doesn't matter how short they are, the bump steer is almost nothing.
This doesn't go for a beetle/karmann and therefore a R&P with the bracket in the midle of the car and long steering rods compensates the bump steer as much as possible..

Glauco


Title: Re: rack and pinion question
Post by: volkskris on July 14, 2022, 08:31:56 am
That is the reason exactly. Toe change through the suspension travel is far less the longer the steering arms are on a beetle suspension.


Title: Re: rack and pinion question
Post by: -Alex- on July 14, 2022, 21:01:35 pm
Polo rack gives least amount of bumpsteer with long tierods compared to golf or other modern steeringrracks, because beetle suspension arms are longitudal and not transverse like macpherson suspensions or double wishbone. 

With macpherson and double wishbone suspension, the tierods almost move at paraller, so there is little as possible bumpsteering.  For example, mendeola suspension's steering has little or no bumpsteer at all:

(https://www.speedsterowners.com/fileSendAction/fcType/0/fcOid/590866538515641703/filePointer/590866538515682428/fodoid/590866538515682416/imageType/LARGE/inlineImage/true/20151123_101451.jpg)


Title: Re: rack and pinion question
Post by: Eddie DVK on January 03, 2024, 11:44:54 am
I have a question.
Do you have to remove the max steering angel bracket from the beam when placing the polo bracket.
It seems to be in the way.

Regard eddie