Shocks

[7uptruckracer]

What's the difference in a HSR (high speed rebound), and Tie Down, and a Tie Down Digressive Rebound

[JR. MECHANIC]

There a plenty of different curves out there for shocks. I would consider high speed rebound at around 15"/sec. If you are talking about an AFCO HSR, it does not have a ton of low speed rebound, but has more high speed control then their standard shock. A tie down digressive , should have a lot of low speed control, but then blow off. Example: it might be 500# at 1" but only be 550 at 10"/sec. I would say that a standard tie down would have quite a bit low speed control and moderate gain throughout high speed.

[7uptruckracer]

Thanks that was my thought why are people going to HSR over tie downs more rough track friendly, or more feel?

[JR. MECHANIC]

To get to high shock speeds it has to pass through the lower speeds first. Too much low speed control on a rough track will ratchet down and make for a teeth rattling ride.

[7uptruckracer]

This year from crew chiefing asphalt, we tried a high rebound setup (800#s at 1"/sec) on a digressive it sure did ratchet down, broke a shock mount too thanks for the info it went along with my thinking, I still don't know why someone would run a digressive tie down, I guess its just a really high rebound at low speeds with a blow off at high speeds. THanks for the info I'll look into it more

[let-r-eat]

Good info there. Hi and Low speed is the preferred adjustments if possible. $$$$$$$ as sad as it is.

[JR. MECHANIC]

I am not 100% sure on the digressive tie down either.... I know most asphalt fronts are like this. I also know that you can typically build a shock with more "clamp" force if you build digressive rebound. I suppose that it is possible that there are situations where you might need a lot of low speed on the RF to help the car turn, but don't want to add a lot of high speed damping in fear of the suspension not returning fast enough over bumps. Bit then again, it has to pass through 1"/sec before it sees higher speeds.

[TALON75]

It kinda has to be digressive when you are dealing with higher numbers at slow speeds. If you were to build the shock number mentioned above, 800@ 1"/sec, with a linear curve it would probably be at 3000@ 10"/sec, and that would be bad!!lol I think 1" numbers are useless in dirt racing, hell rolling through the pits your working it more than that!

[JustAddDirt]

I went to a digressive on the RF because the linear shock would build rate with higher piston speeds, and the RF wheel was leaving the track if the surface was not relatively smooth. I had go-pro on bumper watching the RF.
This was on a UMP mod, but same principal should generally apply.

[LateModel B23]

I put a set of AFCO Silver Series bulb - non schrader valved - on a USRA/USMTS type modifed. The guy ran them one night, took them off and put his digressive Bilsteins back on. The AFCO's were the same #'s as the Bilsteins, he said the car felt like it had no suspension what so ever on it, just solid on all four corners.

[JR. MECHANIC]

I put a set of AFCO Silver Series bulb - non schrader valved - on a USRA/USMTS type modifed. The guy ran them one night, took them off and put his digressive Bilsteins back on. The AFCO's were the same #'s as the Bilsteins, he said the car felt like it had no suspension what so ever on it, just solid on all four corners.

Out of curiosity, who built those?

[LateModel B23]

Tried to send you a PM. Says your mailbox is full.