A new bump steer question

[AmickRacing]

I was checking my bump last night on the RF.
With the wheels straight ahead, 1" down I've got 0.015 out, 1" up 0.015 in, 2" up 0.025" in, 3" up .035 in, and 4" up .045" in.
I know its supposed to toe out, but it was late and that wasn't nearly as far off as I expected so I moved onto an experiment.
I turned to the right approx 20 deg and went through the same motions, and I've got around 0.400" toe in on the RF.
I've never read anything about checking bump with the wheels turned, and I know it's not standard practice, but I was curious to see what it'd do, I never expected that much change.

Just curious if anyone else has done this before?
The one consistent problem I had last year was feeling like I couldn't turn right far enough, there was more than a few times of being right lock all through the corner, that's not a great feeling. After seeing this issue, it makes sense why it felt like that.

btw, I'm running an '03 GRT.

Any thoughts?

[BIGFREAK101]

Well I watched the video and what I see is going on is when you pick the throttle up the cars spins the rear tires while the right rear is loaded this means that appears not to have enough left rear bite. Might try putting some wedge in the car maybe a spring change maybe a softer left rear and loaded it with the wedge shock change can help get the car back on to the left rear. Take all that lead you got on the right rear and on the rear. Move it left. I DONT THINK YOU HAVE A FRT END ISSUE JUST A BALANCE OR SHOCK ISSUE. Good Luck BOOGIE BOOGIE BOYS. .. just my two cents

[Ltemodel]

When checking bump with the wheels turned the big thing to keep in mind is ackerman or over all toe out. I know some cars that will toe out 2+ inches with ackerman effect. If you car has 2" of ackerman toe and bumps in .400, your over all toe out is still 1.600". In a pefect world we would want 0 bump, but there are too many compromises in the front end to achieve this sometimes. Ackerman really plays a big role in how the car steers and the tires hold traction. Check your ackerman and know how it relates to the rest of the front end. Front end work gets pretty complicated, but the challenge is a lot of fun.

[AmickRacing]

Considering how relatively basic the front ends are in a LM, they are still indeed pretty friggen complicated once you start getting deep into it.

I did spend a bit of time today and was able to get the bump a bit better, now the RF toes out around 0.055-.060 in the 3" of compression. I didn't bother with the turned test since the changes I made were pretty minimal.

I wish I had a few more working video's from last season, course I only ran 6 nights last season. The 1st video from last season was back when I was on straight valved afco's (old school stuff). The last video was the 2nd (I think) night on Integra's. Night and day difference for sure! I've only been able to get around 4 nights on them, so I'm sure the shock tuning leaves a bit to be desired, but even when it's not right, it's better than the old shocks were when they were at their best.

Unfortunately there's no lead on the car, we're just a bit over the min weight with out any and 15 gallons of fuel. The percents and weights aren't terrible though, I'd have to check the notes, but about the only change that'd be nice is a bit more rear % (I think I have around 55.5% with 20 gal of fuel). With the new shock package I did go with some different springs. Not too far off of what I was running, but I think that helped a bit too.

I'm sure there's a lot of speed left in the car to find, but it's getting there. Just doing my best to make sure I don't have too many stupid issues hiding in the car that can effect anything. If there's going to be any stupid issue's, they are generally the guy who's turning the wheel :o

Thanks for the advice!

[dfhotlm33c]

Amick,

Just watched some of your in-car videos..very good stuff, good learning material! May I ask what you have for an engine, and what size tracks you run on? (Sorry to hijack)

[AmickRacing]

No problem!
My home track is Black Hills Speedway in Rapid City, SD. It's a half mile, fairly wide with pretty decent banking. Not sure the angle, but I'd guess 12-15 deg. It used to be a very fast tacky track, but too many years of no new dirt has lead to a harder more dry surface.
Some of the video's are of the 3/8 mile track at Black Hills Speedway, they put a track inside the half mile several years ago, then eventually went back to the half.
The next closest track is Gillette Thunder Speedway in Gillette, WY. It's a 3/8 mile track with a lot of banking. This track is generally pretty smooth, has good bite in the heat races but when it gets slick, it can get pretty slick.