Axle Hop Help

[Grant808]

I wouldn't use the bottom hole for any handling app, unless the fenders at at , < 26.5" in height, and you have a relocated UCA position. (higher than OEM)

I don't mean to sound argumentative, but where do you think his outside fender is in a turn? Account for roll and part of the suspension loses the anti-squat mid turn and can't put the power down coming out. In Darren's case that's, probably causing or contributing to the hop. Dropping to the bottom hole would help keep some AS for the loaded outside wheel. Increased roll oversteer doesn't hurt either, IMO.

I can usually plot suspension geometry pretty well, just from knowing fender heights. Not 100% precise, but close.

Without the tire height, it can be wildly off. My car only sits about 1/8" higher than Darren's but my tires are only 25.5" tall so our setups are very different even though we both have the same ride height and 3" lowering of the rear LCA connection. Lots of Mustang road racers use tires down to the 645 slick height...others up to 27.7" (like 275/40-19), and that's why I asked.

 

[blacksheep-1]

fwiw grant is pretty active on the boss mustangs online forums and has some history with these cars. My experience is limited to all of the fox body series and as the tire specialist on the boss 302 GS cars. (the guy everyone looks at when the car doesn't handle). His perspective is probably a good one.

 

[darreng505]

Yep. I know grant. He bought one of my factory boss recaro seats.

PS. Still haven't gotten an email reply from Joe. :/

 

[blacksheep-1]

Should have check ur e mail

 

[darreng505]

I got a reply from Joe. Will call him on my way down to VIR tomorrow when I have time. Thank you sir! Appreciate the tip.

 

[darreng505]

The adjustments I made worked well. I think my tune has a stutter in it at lower rpm that I was confusing that for wheel hop, but here's what I did prior to this past weekends event at VIR.

1. Raise wing angle to 6*
2. Adjust compression and rebound 2 clicks to a total of 6 clicks all around. Then added 2 more clicks on rear rebound to 8. (out of 10)
3. Added .5" rear wheel spacers to correct an oversteer condition I felt in the upper esses at VIR. This brings my front/rear traction balance into better harmony (i.e. more square), although most racers don't run them in the rear, it seemed to play a role in the outcome.
4. Installed the 302s spherical end rear LCA's
5. Hot PSI set to 32 front, 31.5 rear

Posted a 2:04.7 best time over the weekend (VIR full). That was on a full tank of gas and spent hoosiers (16 heat cycles). Probably 3700lbs and change on grid.

Nice seeing and meeting folks there.
Happy Memorial Day to all and our service men and women especially.

 

[blacksheep-1]

Here's some handling porn for you....at Lime rock we came from 22nd to 7th, was running 4th but got an "assist" from another car.

 

[darreng505]

Good stuff Rob!

However, keep those front tires on the pavement, where they work better.

I'm setting up my build and drop off with Joe, so thanks for that.

 

[BMR Tech]

I know this was somewhat of an old conversation, but I do not recall seeing the responses - or I would have chimed in.

I don't mean to sound argumentative, but where do you think his outside fender is in a turn? Account for roll and part of the suspension loses the anti-squat mid turn and can't put the power down coming out. In Darren's case that's, probably causing or contributing to the hop. Dropping to the bottom hole would help keep some AS for the loaded outside wheel. Increased roll oversteer doesn't hurt either, IMO.


Without the tire height, it can be wildly off. My car only sits about 1/8" higher than Darren's but my tires are only 25.5" tall so our setups are very different even though we both have the same ride height and 3" lowering of the rear LCA connection. Lots of Mustang road racers use tires down to the 645 slick height...others up to 27.7" (like 275/40-19), and that's why I asked.

You make very valid points. I don't take that as argumentative one bit my friend. That said, I did say <26.5". I realize how it works, I promise. Your scenario for your car, does not apply to what I stated because your car sits higher than 26.5". With your car, and his car - both, I would recommend the lower position at 26.5" arches, or lower, regardless of tire size (you can only run so many different tire sizes - I have set suspensions up with all of them). If you go the opposite direction, then of course, we must start being more analytical.

As for the fender in the corner - correct. As for "that" contributing to his problem, I simply do not see that to be the issue (as he indicated, his results worked)

To touch on that a little more - I agree with you 1000% about the CA angles, mid turn, roll steer, etc etc.. BUT, where do you draw the line? Steep angles can wokr wonders in one instance, and be a disaster in others. Do you want more effective braking, or power coming out? Based on what you want, how do you want to achieve it, and what do you want to give up? I'd rather improve applying power in a corner and coming out harder - but I think I would tune that without going so steep on my IC location. I do not know if you have experienced sever brake/axle hop under heavy braking, but it is no good. Talk about messing up your routine.

So yeah, I agree with you. I also believe that you should approach things systematically, and only resort to using a steep IC, when you have exhausted other options.

Great tech! I enjoy talking suspension.

The adjustments I made worked well. I think my tune has a stutter in it at lower rpm that I was confusing that for wheel hop, but here's what I did prior to this past weekends event at VIR.

1. Raise wing angle to 6*
2. Adjust compression and rebound 2 clicks to a total of 6 clicks all around. Then added 2 more clicks on rear rebound to 8. (out of 10)
3. Added .5" rear wheel spacers to correct an oversteer condition I felt in the upper esses at VIR. This brings my front/rear traction balance into better harmony (i.e. more square), although most racers don't run them in the rear, it seemed to play a role in the outcome.
4. Installed the 302s spherical end rear LCA's
5. Hot PSI set to 32 front, 31.5 rear

Posted a 2:04.7 best time over the weekend (VIR full). That was on a full tank of gas and spent hoosiers (16 heat cycles). Probably 3700lbs and change on grid.

Nice seeing and meeting folks there.
Happy Memorial Day to all and our service men and women especially.

A Little late, but, great results! Good luck in October Darren. :banana: