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What is the best way to mount a linear position sensor on a shock?

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#1
DavidNJ

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Does someone sell brackets? Has someone designed brackets? Using the output was discussed in the first AIM video.



#2
Tom Hampton

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where are you mounting it?  


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#3
TrailBrake

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Most times it's easier to mount them to a part of the suspension and the chassis, not to the shock itself. Then, you can do a math channel to get the shock displacement and wheel movement.

 

I believe when Roger did it on a Miata he used a ride height sensor out of an old Lincoln (?) and did a linkage arrangement to get the suspension movement. 


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#4
Steve Scheifler

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Seems like a huge amount of work for a car without adjustable shocks or optional spring rates. Other than knowing how deep you get into the pump stops, what do you hope to learn from this data, and what will you do with that information? I assume you already have steering, throttle and brakes logged?
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#5
DavidNJ

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Seems like a huge amount of work for a car without adjustable shocks or optional spring rates. Other than knowing how deep you get into the pump stops, what do you hope to learn from this data, and what will you do with that information? I assume you already have steering, throttle and brakes logged?

 

Minimally, it would allow modeling the position of the car's suspension around the track (using software like Performance Trend's Suspension Analyzer) which could be useful in conjunction with tire temp monitoring. 



#6
Todd Lamb

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On an SM I haven't ever felt the need for suspension travel data, or even tire temp data (tried it for a season and it wasn't a useful data set). Interesting and fun if you like to nerd out over data, but without adjustable shocks or changeable springs it's only going to give you data that you can't tune with anyway.

Just giving my $.02 before you go spending a bunch of money in the wrong place. IMO work on sensors for driver and engine monitoring.

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#7
OctaneNation

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I have a problem with my rear tires getting really greasy after 15 minutes. I've gone down to 32 psi hot to try to combat this and I don't think I have the problem licked yet. I bought some IR tire temp monitors that I'll try out--hopefully they provide some insight.



#8
Todd Lamb

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Sounds to me like you have a loose car. 32psi is too low, as well.

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#9
Tom Sager

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I have a problem with my rear tires getting really greasy after 15 minutes. I've gone down to 32 psi hot to try to combat this and I don't think I have the problem licked yet. I bought some IR tire temp monitors that I'll try out--hopefully they provide some insight.

What year is your car?  What kind of tires and how old?  What are your rear alignment settings and sway bar position?  How much rear shock travel is there between the bottom of the bump stop (with the bump stop pushed up) and the top of the shock body with your body weight in the car? 


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#10
OctaneNation

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What year is your car?  What kind of tires and how old?  What are your rear alignment settings and sway bar position?  How much rear shock travel is there between the bottom of the bump stop (with the bump stop pushed up) and the top of the shock body with your body weight in the car? 

'90. SM7's with a couple of weekends on them but it's happened before. About 1/16" toe in on the back, bar is full hard in the front and full soft in the back. Current ride height is about 5-1/8" (has run as low as 4.5" last year). Offset bushings up front this year. I had the issue last year and this year with various ride heights. Camber is about 3* in the rear. Car is at minimum (2275). 

It's caught me a few times, most recently on the slowest corner of the track, rear tires started spinning like I was on ice in 2nd gear at around 5500 RPM.



#11
Bench Racer

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Corner speed when wheels spin, < your words?  Wheel spin or diff open and spin. What rear end, open, viscous L/S, MazdaComp L/S or Torsen?

 

Bump stops, OEM or FatCat. Could be bottoming out on the rear outside bump stop (first portion of many bump stops are low rate increase/soft and then the rate goes high in a hurry, example FatCat first 3/4 inch is low rate/soft) and then the rear will snap loose RIGHT NOW.

 

Wish my 1.6 had balls enough to spin wheels, NEVER happens.  :bigsquaregrin:


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#12
Tom Hampton

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'90. SM7's with a couple of weekends on them but it's happened before. About 1/16" toe in on the back, bar is full hard in the front and full soft in the back. Current ride height is about 5-1/8" (has run as low as 4.5" last year). Offset bushings up front this year. I had the issue last year and this year with various ride heights. Camber is about 3* in the rear. Car is at minimum (2275). 

It's caught me a few times, most recently on the slowest corner of the track, rear tires started spinning like I was on ice in 2nd gear at around 5500 RPM.

 

With the right combination and timing of inputs I can break my tires loose, sorta. Generally when rolling from a hard-turn in one direction to a hard turn on the opposite, and a not quite smooth throttle application while the body is rolling. But its nothing like driving on ice wheel spin---Its just a slight elevation in engine RPM until the weight transfer settles out.

 

That doesn't sound like tires/pressures to me---even if it were, I think you are going the wrong way (you should be in the 35-38 PSI range).  This sounds like a setup issue (or driver induced issue).

 

As bench asked, what bumpstops are you running (stock or fatcats)? (Stock can be pretty scarry if you hit them hard, say with rapid wheel input and digital throttle appilcation)

What diff do you have (open, cusco, comp, torsen, etc)?

 

who did your setup?  If you did it, do you have scales?  Did you level them properly? 

Do you have a complete setup sheet for the car (for times when this was happening)?

What are your corner weights (with driver)? 

 

Does this only happen under full-throttle in low gear turns when loaded up? 

Are there any other phases where it happens (turnin, apex, exit)?  Can you list the specific turns where/which phase it happens?

Any difference left/right?

 

If I were trying to figure it out from square one, I'd put my I'd set all 4 tires to a single cold pressure, maybe 30 psi...and then go out for a session and measure hot pressures immediately in the hot pits.  Then see what the growth tells you.  If its truely "spinning the tires/driving on ice" loose that should show up in the pressures, as long as you are getting up to operating temp and are close. 


-tch
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