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Bump steer issues with lowerd suspension

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daviespaj
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2020/02/16 19:39:30 (permalink)

Bump steer issues with lowerd suspension

Some years ago when I had another 964 I renewed the suspension and set it somewhat lower than standard, despite having a geo set up it never felt truly planted on the road especially on less than perfect roads (many of them around us) and had some influence on me selling it for my 997. However I missed the old school feel of the 964 and purchased my project 964. I have purchased a set of Bilstein B16 coil overs and will carry out a complete bush renewal. 
However I read an advert for RS style steering arms which would correct the suspension geometry if you lower a standard 964. If you leave the standard ones in the geometry is incorrect, especially in terms of bump steer.
Do any of you good people have experience or knowledge around this?
Thanks
Peter

964 C4 Coupe in restoration
997 C2S
BMW 330d Xdrive touring (all rounder)
Mini Cooper S (wife's all rounder)
Saab 93 Convertible (wife's summer toy)

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Gordon Attar
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Re: Bump steer issues with lowerd suspension 2020/02/17 20:00:10 (permalink)
The C4   will feel more planted  as more weight to the front but invest in a good strut brace.  It will always feel light at the front end. I've not heard about the RS arms solution.

Gordon
964 C2 Cab, 996TT
ex cars 944S2, 964 Targa, 944T, 993 Cab, 993 Targa, 993 C4S, 993TT, 996TT, 997TT, Cayenne Turbo
T911UK
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Re: Bump steer issues with lowerd suspension 2020/02/18 08:49:11 (permalink)
If you  are going to lower the car a fair bit you really need to do something to get the track rods back to parallel with the ground. To do this properly you would need the RS hub carriers along with the RS track rods, these parts are over £3K + vat. You cannot just fit the RS track rods onto your standard carriers as the RS ones mount in the opposite way. 
 
I believe Elephant racing have some kind of kit that does go someway to reducing bump steer but have no experience of it, maybe this the kit you talk of?

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daviespaj
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Re: Bump steer issues with lowerd suspension 2020/02/18 21:48:22 (permalink)
Thanks for the information, it was the Elephant Racing arms I was referring too. So many people lower the 964 I wondered if any had similar experience to the one I had with my previous 964?
Cheers
Peter

964 C4 Coupe in restoration
997 C2S
BMW 330d Xdrive touring (all rounder)
Mini Cooper S (wife's all rounder)
Saab 93 Convertible (wife's summer toy)
Dekker
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Re: Bump steer issues with lowerd suspension 2020/02/19 13:55:40 (permalink)
When I renewed the suspension on my 964 C4 Cab if I took it to RS height I had severe bump steer and settled at RS+10.
 
When I did the same on my C2 Coupe I went to RS and even lower without any bump steer. I used B16 (PSS10) with RS style monoball mounts and geo set to RS specs and it sticks like glue, never had a light feeling on either car by the way. Both cars did a few trackdays so were well tested.
 
From what I understand it depends on the car and the only way you can find out is to try and see.

David Bladon
964 C4 Cabriolet Cobalt Blue
964 C2 Coupe Marine Blue
SAAB 900 T16 Ruby 1993 all weather
daviespaj
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Re: Bump steer issues with lowerd suspension 2020/02/19 20:22:38 (permalink)
Thanks David
Interesting you had mixed results.
As mentioned, I have B16 (PSS10) suspension with adjustable top mounts. I will have to try it out and see how it feels? Hopefully try and book it into Centre Gravity for a good set up?
Regards
Peter

964 C4 Coupe in restoration
997 C2S
BMW 330d Xdrive touring (all rounder)
Mini Cooper S (wife's all rounder)
Saab 93 Convertible (wife's summer toy)
Talat
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Re: Bump steer issues with lowerd suspension 2020/02/19 20:53:53 (permalink)
I have the Elephant kit - my advice would be to save your money.  Marginal improvements which are ultimately not worth it given the outlay.
daviespaj
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Re: Bump steer issues with lowerd suspension 2020/02/19 21:30:26 (permalink)
Much appreciated information, I will see how it goes with the standard steering arms and a careful set up.
Regards
Peter

964 C4 Coupe in restoration
997 C2S
BMW 330d Xdrive touring (all rounder)
Mini Cooper S (wife's all rounder)
Saab 93 Convertible (wife's summer toy)
Dekker
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Re: Bump steer issues with lowerd suspension 2020/02/20 14:10:31 (permalink)
daviespaj
 Hopefully try and book it into Centre Gravity for a good set up?
Regards
Peter


 
I used C of G in the past but after asking a Ferrari & Lamborghini outfit they told me they used Chemix in Stourbridge.
There's a guy called Simon there who's really good and I make sure he's working when I go. He uses all the same gear that C of G uses but at a quarter of the price.
I took my C2 there after I'd updated the suspension and he had to get his acetylene torch out to free up one of the track rod ends and all for the fixed price of £85.
 

David Bladon
964 C4 Cabriolet Cobalt Blue
964 C2 Coupe Marine Blue
SAAB 900 T16 Ruby 1993 all weather
Dekker
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Re: Bump steer issues with lowerd suspension 2020/02/22 12:27:59 (permalink)
Talat
I have the Elephant kit - my advice would be to save your money.  Marginal improvements which are ultimately not worth it given the outlay.




Hi Talat,
the Elephant kit is that the one where you can adjust the track rod arm angle by adding or removing various supplied washers?
If so I'm surprised that it didn't help with bump steer as from what I understand, the BS is the result of the track rod arms not being in a horizontal position.

David Bladon
964 C4 Cabriolet Cobalt Blue
964 C2 Coupe Marine Blue
SAAB 900 T16 Ruby 1993 all weather
ras62
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Re: Bump steer issues with lowerd suspension 2020/03/10 16:47:07 (permalink)
set at RS +5mm or higher bump steer will be minimal if at all. Below this introduces the problem getting worse the lower you go. There are kits on the market but I've not tried them personally
daviespaj
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daviespaj PCGB Member
Re: Bump steer issues with lowerd suspension 2020/03/10 20:57:11 (permalink)
Much appreciate the information, I guess RS + 5mm would be fine with a decent alignment set up.
Thanks 
Peter

964 C4 Coupe in restoration
997 C2S
BMW 330d Xdrive touring (all rounder)
Mini Cooper S (wife's all rounder)
Saab 93 Convertible (wife's summer toy)
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