wheel travel/damper travel issues with ohlinsTTX25/CCDB

[mscwu]

hey guys, first post here.
i've seen teams running on ohlinsTTX25 dampers and that's where the problem arises. i think the stroke of ohlinsTTX25 is 57mm, and it seems that a motion ratio close to 1 is suggested by most teams. however, suspensions are also designed with usable wheel travel of 3"-4", which means, leaving a reasonable safety margin, the motion ration should be as high as 1.6-2.0.
how is this justified? we are also considering ohlinsTTX25 but we don't want to run high MRs as well.
anybody has any idea about this?

[mscwu]

hey guys, first post here.
i've seen teams running on ohlinsTTX25 dampers and that's where the problem arises. i think the stroke of ohlinsTTX25 is 57mm, and it seems that a motion ratio close to 1 is suggested by most teams. however, suspensions are also designed with usable wheel travel of 3"-4", which means, leaving a reasonable safety margin, the motion ration should be as high as 1.6-2.0.
how is this justified? we are also considering ohlinsTTX25 but we don't want to run high MRs as well.
anybody has any idea about this?

[Rex Chan]

I'm pretty sure the rules state you only need 2" of travel (1" either way). This means you only need about 50mm of travel, which would appear to work.

I'm also pretty sure most teams only design for 2" of travel. Where did you get 3-4" from?

[mscwu]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Rex Chan:
I'm pretty sure the rules state you only need 2" of travel (1" either way). This means you only need about 50mm of travel, which would appear to work.

I'm also pretty sure most teams only design for 2" of travel. Where did you get 3-4" from? </div></BLOCKQUOTE>

Rex,
yeah, i think 3-4" is too much as well. maybe 2" travel is generally accepted so that nobody talks about it, and that's how the 3-4" argument stands out. still, the rule states that 2"travel is available when the driver is seated which means merely 2" is not enough. if we take the bump into consideration the travel should be set somewhere between 2"-3".
does that make sense?

[rmk36]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by mscwu:

the rule states that 2"travel is available when the driver is seated which means merely 2" is not enough. </div></BLOCKQUOTE>

Adding a driver to the equation will not change the allowable travel in your system. You can design for 2" of travel and still be fine with a driver. You just need to set ride height/spring preload with a driver in the car, to have it right in the midpoint of your travel if that's what your getting at.

PS. All of your car design considerations as well as physical suspension set-up should be done with your driver in the car...after all, it won't be racing without him.

[Tom Wettenhall]

I personally like the 1:1 MR because it gives you bump/oscillation control (high speed) and body control (low speed) separately on the standard valving for TTX25 Mk2s. Our car (Uni Melbourne 2011) has 57-58mm of travel only. We can't run springs softer than 130lb/in front because of bottoming but pitch control is more important than travel for us anyway.