The Mustang Forum for Track & Racing Enthusiasts

Taking your Mustang to an open track/HPDE event for the first time? Do you race competitively? This forum is for you! Log in to remove most ads.

  • Welcome to the Ford Mustang forum built for owners of the Mustang GT350, BOSS 302, GT500, and all other S550, S197, SN95, Fox Body and older Mustangs set up for open track days, road racing, and/or autocross. Join our forum, interact with others, share your build, and help us strengthen this community!

Suspension changes advice needed

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
Season starting up at the end of the month, jumping form 295/30-30 semi slicks to R7's in the same size..... and these are the changes I want to make.....

1) Replace GT 24mm rear bar with 18mm rear bar
2) Change from Lower hole on BMR lca bracket to middle leaving LCA at approx 3 to 4 degs instead of 6 deg
3) Raise the rear a little to put more weight on it.

I heat cycled my R7's the other day with my old setup in place and with full TC on, a/c at 100% and without pushing at all, got too within a few tenths of my best time going all out with the semis....

Should I leave everything as is till race day and go forward in a orderly adult manner? Or should I do all of the above right away like a kid in a toy store??
 

cobrarob

11 Shelby GT500
555
130
new york
I'm not as advanced on setups as other members on here,but i would say do one thing at at a time.If you do everything at once(as we all wanna do)you might not know which really helped or hindered. I go thru the same so just my opinion
 
Cobrarob said:
I'm not as advanced on setups as other members on here,but i would say do one thing at at a time.If you do everything at once(as we all wanna do)you might not know which really helped or hindered. I go thru the same so just my opinion

+1 Unless you're moving to a known configuration, 1 change at a time. One of the first principles of physics -- hold all variables but 1 constant and measure the changes
 

Grant 302

basic and well known psychic
I wouldn't do #3 without #2.

I generally agree with doing one thing at a time, but in this case...at least you'd only be making changes on one axle. I don't see the problem doing all three if you can get at least some seat time before the next event. None of these mods are really reinventing the wheel.

Are you able to switch it/all/any back at the track if you have the time?
 

Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
Normally I would go slow one by one, its just that the track is 700km away and not sure how much time I will have. Looks like if I leave early Saturday, I can have a half day to practice before the race on Sunday. Most of the changes have been recommended by TMO so they are not so far out .. I think..

Was thinking of doing 2 and 3 now, since they are related, and then taking the 18mm bar with me since that's the quickest to change.
 

Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
Yup left the 18mm bar for later after I see what its like at the track. the LCA in the 2nd of three holes. The lower holes was at 6.6 deg and now its at 3.7 deg. Rear looks fine at a cm higher.
 

Grant 302

basic and well known psychic
I think that's a good approach. Wouldn't be that hard to swap bars if you wanted to do it at the track.

On a slightly separate note, I have been meaning to mention that I think some concerns about roll steer (either way) have been a bit overstated. The LCAs are also splayed out to the rear when looking from above. It's a little more obvious on aftermarket units where the rear connection can be clearly seen to be outboard of the front connection to the body.

Like this:
KB-IMG_5466.jpg
or this:
05%20Mustang%20Rear%20Lower%20Control%20Arm.JPG


This arrangement reduces, if not eliminates some of the effects causing roll steer...over or under. I don't think I've ever mentioned how the splay of the arms do this. Also want to note that some arms are offset more than others in my observation.
 

Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
Yes, I saw the offset of the arms under the car today. But I think a 6.6 deg angle may be a little steep. I'll update next week!

Your car is a lot cleaner then mine!!
 

Fabman

Dances with Racecars
6,518
8,154
Exp. Type
W2W Racing
Exp. Level
20+ Years
Pleasanton: 1/2 way between Sonoma and Laguna Seca
Mad Hatter said:
Yes, I saw the offset of the arms under the car today. But I think a 6.6 deg angle may be a little steep. I'll update next week!

Your car is a lot cleaner then mine!!
Try all the holes for the lower trailing arms. You'll be surprised how significant the change can be.
Start at one extreme, then go directly to the opposite extreme, This will give you the best feel for whats happening.
Then, once you know what both extremes feel like, go find the middle.
Small changes are often misinterpreted or not significant enough to drive the lesson home.
But if you make a change that goes from wildly loose to wildly pushing for example, there is no doubt what you did to cause it, and how to get back to where you were, or where you want to be.
As I've said before, there is no better classroom than the race track if you use the time wisely.
 

Grant 302

basic and well known psychic
Mad Hatter said:
Yes, I saw the offset of the arms under the car today. But I think a 6.6 deg angle may be a little steep. I'll update next week!

Your car is a lot cleaner then mine!!

Not pics of my cars! My Boss is clean...FakeR, not so much. :-[

And yes 6.6º did sound steep. Looking forward to your impressions using 3.7º.
 

Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
Fabman said:
Try all the holes for the lower trailing arms. You'll be surprised how significant the change can be.
Start at one extreme, then go directly to the opposite extreme, This will give you the best feel for whats happening.
Then, once you know what both extremes feel like, go find the middle.
Small changes are often misinterpreted or not significant enough to drive the lesson home.
But if you make a change that goes from wildly loose to wildly pushing for example, there is no doubt what you did to cause it, and how to get back to where you were, or where you want to be.
As I've said before, there is no better classroom than the race track if you use the time wisely.

I have been using the two lower holes off and on for a while, The lowest helped on tight tracks but braking got squirrely. The OEM brackets with the car lowered were horrible, The car would not turn in and felt like a crab scuttling around the corner. Curious to see the affect now with the rear bar, tried before with no rear bar but the understeer was too much for me. The Clock will tell!!
 

Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
Grant 302 said:
Not pics of my cars! My Boss is clean...FakeR, not so much. :-[

And yes 6.6º did sound steep. Looking forward to your impressions using 3.7º.

Fingers crossed! down to the brass studs on my pagid pads. Put some used RS29 pads on with a little more meat on them. Hope the last ok! New RST-3's are on the way but will not make in in time.
 

Fabman

Dances with Racecars
6,518
8,154
Exp. Type
W2W Racing
Exp. Level
20+ Years
Pleasanton: 1/2 way between Sonoma and Laguna Seca
Mad Hatter said:
I have been using the two lower holes off and on for a while, The lowest helped on tight tracks but braking got squirrely. The OEM brackets with the car lowered were horrible, The car would not turn in and felt like a crab scuttling around the corner. Curious to see the affect now with the rear bar, tried before with no rear bar but the understeer was too much for me. The Clock will tell!!
perfect, you've just discribed the effects of excessive anti squat and roll under steer.
I think you'll find the sweet spot somewhere in between. ;)
I also think you're gonna like that 18mm bar.
 

Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
blacksheep-1 said:
FWIW we've run over 5 degrees on our PWC car, we had to hog out the shock mount holes to do it. It wasn't permitted in IMSA, or the SCCA.


Hmm, now I am a little confused... I though you guys did not run with a lower lca bracket??
 
6,361
8,182
We normally don't run LCA relocating brackets in the rear, we butcher the front end all to pieces. The PWC rules lend themselves to this, with that tire, you're probably good with 3 or 4 degrees. 3 degrees is the limit in SCCA T2 right now..it's OK, but the car asks for more usually.
Also a new tire's fastest laps will be the first 4, so if you intend to scuff them in, do exactly what you did, they will last much longer than some that are "burned" in, as in say qualifying. We do run different pressures in qualifying for this reason, but limit them to 4 laps, tops, any more is a waste of time. The driver needs to find a hole and get it done in 4, or he's done, just the way it is, after that, it's all diminishing returns.
 

Mad Hatter

Gotta go Faster
5,237
4,227
Santiago, Chile
Hmm,,. forgot to take into account the slight angle on the Drive way . Measuring again on level ground, the LCA angle went from 6.6 to 3 degrees. Maybe I will raise the rear a tad more at the track to get closer to 4 degrees
 

Fabman

Dances with Racecars
6,518
8,154
Exp. Type
W2W Racing
Exp. Level
20+ Years
Pleasanton: 1/2 way between Sonoma and Laguna Seca
Mad Hatter said:
Hmm,,. forgot to take into account the slight angle on the Drive way . Measuring again on level ground, the LCA angle went from 6.6 to 3 degrees. Maybe I will raise the rear a tad more at the track to get closer to 4 degrees
Car has to be at ride height and on perfectly level ground or its all for nothing.
 
6,361
8,182
Grab a piece of structural aluminum, cut it into 4 equal size squares, put some grease on it, then do the same thing again, lay squares #2 over the greasy square #1s bounce the car a few times and let the grease do it's magic. Keep some extra squares or even some squares of plywood around to level the aluminum. You basically have a setup pad.We have to do something similar to this at most races, we do have a pad that is adjustable, that costs thousands, but the pads are on rollers. You can sort of simulate that by getting a little dirty.
 

TMO Supporting Vendors

Top