MG Motorsports Forum

The following quote from Dave got my attention:

"RE: turn in grip. Keep your rear shock rebound damping as soft as possible to allow the rear to rise under trail brake turn in. This will reduce the amount of roll understeer in the rear suspension when braking. "

I asked Peter Caldwell, as good or better than anyone with race-prepped lever shocks, whether rebound could be made softer but compression kept race-hard.

He said that it did not work that way. If you wanted softer rebound in a lever, you would have to have softer compression. Peter, if you read this please correct me if I am wrong.

Dave, or anyone, should the lever shock be softened in rebound if that will soften compression?

And is a tube shock with separate adjustment for compression and rebound a better shock for the rear?



Edited 1 time(s). Last edit at 2016-05-23 10:46 PM by dcharnet.

Good question for discussion!

I run Peter's race prepped levers in the front (Huffaker recipe) and stock in the rear as per his advice.
I spoke with Dave in regards to lever or tube in the rear, I still run lever.

I have pictures of my car in braking and the back end lifts so I have soft rebound, but that means I also have soft compression. What are the negatives of that?

I have Peter's shocks all around, and I have driven all sort of race prep LBCs, some with shocks that cost more than most whole cars. With my vintage B with Headley suspension pieces and Peter's shocks, I don't need to second guess if I need something better, the car does everything I ask it to do, and it does so better than most cars around me, I seem to be able to put my car where others cannot. I think the key in vintage and with the tires we have, which is our greatest limiting factor when compared to the slicks I grew driving on, is you need to be able to keep your foot in it and let the car move around, yeah it gonna slide and drift a bit, which suits me just fine, as I learned this sort of thing driving a Midget in the SCCA. In SCCA driving schools I used to ask my students, do you feel comfortable out there, if they said yes, then I would tell them, well you need to go faster, this is not about comfortable

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Hap Waldrop
Acme Speed Shop
864-370-3000
Website: www.acmespeedshop.com
hapwaldrop@acmespeedshop.com

Don, if you know what the shock valving you have now is, then easier to make that determination. Many OE type tube shocks have softer rebound than compression.

Dave,
Does having tube shocks with adjustable valving make a difference, or at least enough of a difference to notice?

Don, that may be what I said, but when you re-state it, it's not what I meant.

The rebound and compression valving can be changed independently by altering a few of the internal valve components, like springs and orifices. Our adjustable shocks are not able to adjust rebound and compression separately. The rebound and compression will stay in the same ratio, with the adjustment changing the baseline for both settings. We can make the relative changes of rebound and compression to your wishes. The external adjustment lets you have further control for certain track conditions. Is that better?

Peter

Gives you one more thing to tune. I will have to admit in all my racing I did very little shock tuning.

I'm currently running rear adjustable Spax tube shocks though the plan is to switch back to some of Peter's Lever shocks when cash allows. The biggest problem I've found is that despite modifying the mounting brackets I run out of travel because the car sits so low. Losing all the suspension movement makes for pretty sketchy handling so I think I'm going to make the change.

And like Dave, I've not really spent much time playing with the adjustments. I stuck them on there and have been running them the way they are and they seem to work just fine. I've thought about messing around with them but that means laying on the ground and it's dirty and I have to find a screwdriver and what if I do it wrong....

Jonathan

As with most modifications with incremental gains, it depends on how good of a driver you are.

The adjustability isn't what makes a shock good or bad, it's everything inside of it.

This is vintage legal (no remote reservoirs):
https://www.ohlins.com/product/ttx36-inlinettx36-piggyback/



Just set it up as a non-coilover set-up.

Set up correctly, the above will allow you to do things you could never do on track with a lever shock.



Edited 1 time(s). Last edit at 2016-05-24 05:45 PM by hoffman900.

Peter, and everyone, thanks.

Let's try to move this toward a "lever" solution, since most of us use levers and most of us use Peter.

But first let me introduce another element here: assume removal of one leaf in the rear, to further soften and lower the rear.

Dave, assume that one leaf has been removed. The car will naturally lift more in the rear on trail braking, correct?
With that, would you still suggest having Peter adjust to "as little rebound as possible?" In other words, might there be too much softness in rebound? Peter, any observations about that under racing conditions?



Edited 1 time(s). Last edit at 2016-05-24 06:38 PM by dcharnet.

Staying with a Lever Solution might be wise... the Ohlins are about $1500 a pop!

Peter... when you change the springs and orifices are they all on the screw in valve assembly or are some of the orifices in the shock body?

Don, theoretically, that's correct.

Assuming removal of a leaf on each side in the rear and a race-prepped lever shock, can anyone surmise about the effect of going all the way to minimum on rebound and leaving compression race-hard?

And what happens dynamically with those parameters if rebound is too soft?

All of the valving is done within the valve assembly. There are poppet valves in the pistons that can blow out with heavy oil, leaving no damping, but nothing that is metered. We have springs specially made for the racing shocks, and we strongly recommend using Redline Heavyweight Suspension oil. It doesn't go to foam after 22 minutes of racing.

Peter

Then it might be practical to have a variety of valve assemblies which could be used to tune for different tracks?