Front strut brace = increase in understeer?
Discussion
Just a technical question wich has been bothering me for a while know. I know a lot of people fit a strut tower brace on their cars. Supposedly it enhances the handling of the car. Here's the thing, I've also heard that it increases understeer? I'm not a technical guru and this might be a modification I'm considering for my car (seeing that they are relatively cheap). Could anyone enlighten me if this modification enhances the handling or do just the opposite and increase understeer?
(by the way, my car is lowered on Eibach Sport springs and is running 17" wheels with Toyo Proxes T1R)
thnx in advance
Grtz
Erik
(by the way, my car is lowered on Eibach Sport springs and is running 17" wheels with Toyo Proxes T1R)
thnx in advance
Grtz
Erik
Yes, if anything it will give a marginal increase in understeer. If the shell was lacking stiffness in this area, it will also give a marginal increase in responsiveness and predictability.
To be honest,though, you would have to be a very sensitive driver to detect much difference in road use, particularly if you are runnig road (relatively soft) springs. A properly designed strut brace, in conjunction with a full cage, can make a difference on competition cars, but for road cars they are mainly window dressing.
To be honest,though, you would have to be a very sensitive driver to detect much difference in road use, particularly if you are runnig road (relatively soft) springs. A properly designed strut brace, in conjunction with a full cage, can make a difference on competition cars, but for road cars they are mainly window dressing.
I wish I'd had a strut brace on my old sierra xr4i .. the shell flexed and eventually split the transmission tunnel. I'd say if you're a bumpy road hoobner and you think the shell of your car might be a compromising factor I'd fit one just in case there's fatigue already affecting some other part of the shell.
trackcar said:
I wish I'd had a strut brace on my old sierra xr4i .. the shell flexed and eventually split the transmission tunnel. I'd say if you're a bumpy road hoobner and you think the shell of your car might be a compromising factor I'd fit one just in case there's fatigue already affecting some other part of the shell.
I can't actually call my car old, it's a 2001 Punto Sporting with 51.000 KM on the clock. However it does flex a bit when going of ramps and speedbumps slightly sideways, at least that is the only way I can explain the noise coming form the rear windows. They sound like their slightly moving in their frame. I don't think however that a strut brace up front is going to cure this.
hmm... questions, questions. I'm in serious doubt, the effect on the handling will be minimal. But it does look good and it isn't one of the mods that fall in the 'chav' category IMO.
Grtz
Erik
Back again!
Been driving a fair bit this easter weekend. During some of the faster corners where I felt like I was driving on the edge of understeer, my car seemed like it was 'wobbling' (like when a seat has 1 short leg). It felt like the tyres were digging in, and losing a bit of grip (sounds crazy but it's the only way I can explain it). What I felt trough the steering wheel was 'twitching', I held it with both hands and the roads I was driving were flat as a pancake.
My question is, could this be the flex you were talking about? My theory is that because of the extra load that is put on the outer it is pushed more inward. This then causes the inner turret to take some of the load so the outer turret isn't that stressed anymore. Consequently the outer turret digs in again and the whole proces repeats itself, causing the slight wobble.
If this flex is the case, then I am definitely going to fit a strutbrace.
Any ideas or comments on my theory are greatly appreciated!
Grtz
Erik
Been driving a fair bit this easter weekend. During some of the faster corners where I felt like I was driving on the edge of understeer, my car seemed like it was 'wobbling' (like when a seat has 1 short leg). It felt like the tyres were digging in, and losing a bit of grip (sounds crazy but it's the only way I can explain it). What I felt trough the steering wheel was 'twitching', I held it with both hands and the roads I was driving were flat as a pancake.
My question is, could this be the flex you were talking about? My theory is that because of the extra load that is put on the outer it is pushed more inward. This then causes the inner turret to take some of the load so the outer turret isn't that stressed anymore. Consequently the outer turret digs in again and the whole proces repeats itself, causing the slight wobble.
If this flex is the case, then I am definitely going to fit a strutbrace. Any ideas or comments on my theory are greatly appreciated!
Grtz
Erik
It sounds like you were simply approaching the limit of grip at the front end. Tyres are flexible...what you were feeling was probably feedback as they hunted for grip.
To put things in perspective, go out and push hard sideways on the front wing, and see how much the bodyshell of the car moves through tyre distortion...your car sits on four very flexible bits of inflated rubber, which are in turn connected to the bodyshell by a bunch of rubber bushes which are only slightly less flexible. Any flexing due to distortion of the steel bodyshell will be trivial in comparison. It starts to become important on a competition car, fitted with very stiff suspension and low profile tyres, but if you are running road rubber and standard bushes, the amount of flex that would be prevented by a strut brace really would be tiny compared to the amount of compliance in the tyres and bushes.
If you were getting serious enough about handling to be worried about this type of compliance, I'd suggest the following would be the rough order of importance:
1) Low profile tyres, to reduce tyre carcase distortion.
2) Rose joints or poly bushes on the suspension.
3) Stiffer springs and adjustable dampers
4) Seam weld the bodyshell (because by now, the additional loadings cause by the stiffer suspension and bushings will be starting to take their toll).
5) Fit a full cage (this stiffens the bodyshell massively if done correctly).
6) Fit a strutbrace (in practice, admittedly, you'd probably fit a strutbrace as part of the cage).
>> Edited by Sam_68 on Wednesday 19th April 13:44
To put things in perspective, go out and push hard sideways on the front wing, and see how much the bodyshell of the car moves through tyre distortion...your car sits on four very flexible bits of inflated rubber, which are in turn connected to the bodyshell by a bunch of rubber bushes which are only slightly less flexible. Any flexing due to distortion of the steel bodyshell will be trivial in comparison. It starts to become important on a competition car, fitted with very stiff suspension and low profile tyres, but if you are running road rubber and standard bushes, the amount of flex that would be prevented by a strut brace really would be tiny compared to the amount of compliance in the tyres and bushes.
If you were getting serious enough about handling to be worried about this type of compliance, I'd suggest the following would be the rough order of importance:
1) Low profile tyres, to reduce tyre carcase distortion.
2) Rose joints or poly bushes on the suspension.
3) Stiffer springs and adjustable dampers
4) Seam weld the bodyshell (because by now, the additional loadings cause by the stiffer suspension and bushings will be starting to take their toll).
5) Fit a full cage (this stiffens the bodyshell massively if done correctly).
6) Fit a strutbrace (in practice, admittedly, you'd probably fit a strutbrace as part of the cage).
>> Edited by Sam_68 on Wednesday 19th April 13:44
Sam_68 said:
It sounds like you were simply approaching the limit of grip at the front end. Tyres are flexible...what you were feeling was probably feedback as they hunted for grip.
(...)
If you were getting serious enough about handling to be worried about this type of compliance, I'd suggest the following would be the rough order of importance:
1) Low profile tyres, to reduce tyre carcase distortion.
2) Rose joints or poly bushes on the suspension.
3) Stiffer springs and adjustable dampers
4) Seam weld the bodyshell (because by now, the additional loadings cause by the stiffer suspension and bushings will be starting to take their toll).
5) Fit a full cage (this stiffens the bodyshell massively if done correctly).
6) Fit a strutbrace (in practice, admittedly, you'd probably fit a strutbrace as part of the cage).
>> Edited by Sam_68 on Wednesday 19th April 13:44
Thanks for the reply. Point 1 of your list is already taken care of, I've got Toyo Proxes T1-R, 205-30 in 17". (pushing sideways on the car results in it rocking on the suspension). Basically I'm a still a numpty regarding handling, so any advice is welcome! The rest of your steps are indeed far more advanced.
Thnx en grtz,
Erik
It is very difficult to diagnose the sensations someone else is feeling through the steering wheel of a car over the internet, of course, but if you have such low profile tyres fitted already, it may be that the 'twitching' you were feeling through the steering wheel was something else.
A few possibilities come to mind:
1) The additional grip from the non-standard tyres is excessively loading the suspension bushes or subframe mountings, and it is compliant movement of these that you are feeling.
2) You have a damping problem...possibly a combination of tired dampers and the increased unsprung weight of the aftermarket wheels.
3) The offset of the wheels is incorrect, leading to a certain amount of kickback and/or tramlining.
I must admit, I'm not a big fan of wide, ultra-low profile tyres on road cars; they can cause more problems than they solve.
You said you have fitted Eibach sport springs? I assume you have also fitted matching uprated dampers?
A few possibilities come to mind:
1) The additional grip from the non-standard tyres is excessively loading the suspension bushes or subframe mountings, and it is compliant movement of these that you are feeling.
2) You have a damping problem...possibly a combination of tired dampers and the increased unsprung weight of the aftermarket wheels.
3) The offset of the wheels is incorrect, leading to a certain amount of kickback and/or tramlining.
I must admit, I'm not a big fan of wide, ultra-low profile tyres on road cars; they can cause more problems than they solve.
You said you have fitted Eibach sport springs? I assume you have also fitted matching uprated dampers?
Sam_68 said:
A few possibilities come to mind:
1) The additional grip from the non-standard tyres is excessively loading the suspension bushes or subframe mountings, and it is compliant movement of these that you are feeling.
2) You have a damping problem...possibly a combination of tired dampers and the increased unsprung weight of the aftermarket wheels.
3) The offset of the wheels is incorrect, leading to a certain amount of kickback and/or tramlining.
I must admit, I'm not a big fan of wide, ultra-low profile tyres on road cars; they can cause more problems than they solve.
You said you have fitted Eibach sport springs? I assume you have also fitted matching uprated dampers?
Well, I've made a slight error in my last message. My tires are not a 30 profile, but a 40 profile. But I found out last night on the same route that if I attack the corners a bit harder, the twitching doesn't occur. The width of the tyres hasn't increased dramatically, from 185 to 205. Next time around though I'm thinking of changing to a width of 195. This should lower the chances of my car tramlinig.
In regard tot the uprated dampers, this is still on my to do list (I would have been better of by changing them right away, but everybody makes mistakes
). Don't know wich to go for however. I'm thinking about fitting the Eibach shocks or Koni's. Most of the time people do fit Eibach springs but go for other shocks, are the Eibach shocks not up to the job? When fitting the wheels, I compared the weight by lifting both the old and the new wheels (not very scientific). But the new wheels felt a bit lighter, so they shouldn't have increased the unspring wheight very much.
Started with one question, ended up with many
But anyway I'm making progress. Thanks for teh replies!! Grtz
Erik
stew-typeR said:
eibach dont make dampers.
id go for bilstein over koni tbh. better dampers in general.
Uhm, what's this then www.eibach.de/frame.inc.php?SPA=1&C_lang=en&LID1=2&LID2=9&LID3=0 ?
I believe those are dampers by Eibach. Maybe they're from another manufacturer and then rebadged 
. Haven't got any experience with Koni or Billstein for that matter. Just thought that because I have Eibach springs they would be better suited to Eibach dampers/shocks. But I'll have to contact some local specialists to see who can provide what and for wich price (price being a relevant factor, haven't got a permanent job and would like to go on holidays) Grtz
Erik
stew-typeR said:
rebadged mate. like KW who use koni. eibach are a spring manufacturer.
Ok, thanks! Will be looking in to this a bit more. Thankfully there's a tuner not to far from where I live who also prepaires rally cars. Will check with him, he supplies koni as well as billstein.
Thanks for answering al my noob questions!
Grtz
Erik
Gassing Station | Suspension, Brakes & Tyres | Top of Page | What's New | My Stuff