for those who've adjusted front bumpsteer...
...on a lowered car with standard (non-GT3) wheel carriers, and adjustable bump steer kit.
did you space the tie rod end CLOSER or FARTHER away from the steering knuckle? I have the Rennline adjustable bump steer kit with H&R sport springs (GT3 lower control arms also) on my Boxster, and trying to achieve essentially zero bumpsteer. But no matter if I'm using NO spacers or ALL spacers, I'm getting what appears to be toe out on full suspensions compression. What am I doing wrong? |
Quote:
I haven't yet... but I probably need to. I think I understand the premise of how it works.... but I'm in sponge-mode right now. :dance: |
shimming the outer end of the tie rod will correct the geometry for a limited travel of the suspension but you will still have some toe change at full compression.
|
This is something I need to do as well. Reading up on it they talk about grip and bump steer separately, are they truly separate or does bump steer directly effect grip? I can't seem to find a clear statement. My car is lowered as much as it can without comprising my control arm angles but I haven't felt anything of the negative effects I've read up on.
|
thanks guys; I posted this on the Rennlist 996 forum also since it gets a lot of traffic.
what I'm trying to do is dial out (what I perceive to be) understeer on corner entry and midcorner. It occurred to me that, after installing springs/shocks along with adjustable tie rod ends, I hadn't set my bump steer. It's PROBABLY not necessary, as the bump steer is probably minor, if anything, and the understeer is likely driver-induced rather than setup. ( I need more practice :D) Additionally, I think my alignment was off (per my home measurement of toe, I had 1/8-3/16" of total front toe out. So I've got some other changes to make as well. Running a square setup with 255/40/17 RE71R on 8.5" rims all around. |
Jmitro, do you have adjustable bars? These will allow you to adjust the turn in and rotation to your like :-)
|
Good read here.
Technical Articles |
Quote:
|
Quote:
Even with my 225 front 255 Boxster I didn't have any understeer trouble on corner entry, especially if I had any amount of trailbraking, even like a big toe worth. I did have mid-corner understeer on long sweepers like at Roebling. And then I would have a little understeer on full throttle track out. What sway bars are you running, and if adjustable, what settings do you have them on? What brand of springs/shocks and if adjustable, what settings do you have them on? Since you talk about ride height, I am guessing coilovers? I have seen 2 cars now that had terrible oversteer due to too stiff springs in the rear and also set too low and running out of strut travel. I've never seen one that had that condition in the front but maybe it is possible? |
Quote:
How much track driving experience do you have? Sorry for the questions, I just want to understand what is happening. Straying too far from zero-toe will cause understeer, whether it's too much toe-in or too much toe-out. 3/16" of toe-out is a LOT. Bump steer refers to toe change as the suspension moves through it's travel, either up or down. All suspensions have bump steer. You will get toe change when the suspension reacts to a bump, but you will get the same amount of change if the suspension reacts to body lean caused by hard cornering (lateral loads). |
thanks all for the excellent responses. the longacre article is good information; I looked at that a few days ago.
here's a link to the rennlist thread which was also helpful: https://rennlist.com/forums/996-forum/1186896-for-those-who-ve-adjusted-front-bumpsteer.html#post16503630 my suspension is really a street setup- H&R sport springs with Bilstein B8s; it's not coilovers, so ride height is not adjustable. Similarly, the sway bars are stock non adjustable. The only adjustments are front toe and bump steer, rear toe, and GT3 front control arms for additional camber. I've raced with BMWCCA for about 5 years so I have a lot of track experience, but I think my problem is a tendency to turn in too early and hit the apex early or midpoint which means sometimes breathing the throttle on exit to get the nose to turn. It depends on the turn, but generally higher speed turns. So my sensation of "understeer" might be a combination of poor turn in and suboptimal car setup as well |
Quote:
|
So I inserted three 1/8" spacers between the tie rod end and steering knuckle, then took the car to get a professional alignment today. F/R toe was pretty far out.
Final settings were: Front: 1 degree total toe out, -3.0 camber Rear: 0.1 degree total toe in (was trying to get zero toe), -2.0 camber Pretty excited to try these new settings at my next track day. Thanks all for the suggestions. I'll look into more adjustability including sway bars as I progress in the future :cheers: |
Quote:
|
Quote:
The H&R is bigger than the OEM bar on the CS and does not have adjustment, you balance the bars (and the car) with the rear bar. |
Thanks, Gilles. I think that the other complaint is that they are bigger (and thus heavier) so a lot of owners did not like them.
(Sincere apologies to jmitro for stealing your thread!) |
Quote:
Quote:
If that BMW you mentioned has less power than the Boxster, it may be like you said, (I wouldn't call it poor turn in, just a different style based on a different car :cheers: ) Do you have any track video of your current setup? |
jmitro - As Steve mentioned, most people have oversteer when going square. The camber difference front/rear should reduce understeer as you are increasing front grip vs the rear.
|
Quote:
Play around and see what you like. Similar to running an E36 with no rear bar and a square setup. |
I'm anxious to get back on the track and see how it feels. unfortunately most of the events around here have been canceled or postponed for a month or two so it will be some time before I can get a feel for the car. I think I screwed up the alignment doing it myself, so hopefully with the changes above the car will feel different.
my BMW was a euro-powered E36 M3 with 320hp and about 2500lb so this Boxster is a different experience! |
Quote:
I still have a ST2/3 S54 E36 M3. The Boxster really opened my eyes and improved my driving significantly. Really every car should be driven as a momentum car. Sorry for the thread diversion, I remembered your user name from Bimmerforums. |
Quote:
:cheers: |
jmitro - Thanks for the update! Did you need any new end links and parts when installing the H&R front and rear sway bars? How does the car behave at street speeds and driving conditions?
|
I did purchase new Tarrett sway bar end links, but they aren’t required as the stock end links work also. The sway bars come with new bushings.
At street speeds there is no difference. The car behaves and drives just like usual. And I have not heard any noise from them as alluded to earlier. I agree with steved0x - the challenge now is to tame the oversteer |
Thank you!
At what speeds are you encountering oversteer? |
highest I saw on my dashboard yesterday was 107mph before braking. but oversteer can happen at lower speeds like a 40mph auto-x. just depends on how much one is pushing the car to the limit
|
Quote:
|
Quote:
|
All times are GMT -8. The time now is 03:04 AM. |
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.6.0
Copyright 2024 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website