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Best Kpi/sai Angle And Caster Question?

bradsm87
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bradsm87 Proficient

bradsm87

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I'm trying to make my car's suspension have the least amount of compromises possible. I have camber pins AND adjustable strut tops so I can adjust KPI and camber separately. I was thinking i'll set it up for the least possible amount of KPI angle to have the least amount of camber loss and jacking from the KPI when turning. What are the other pros/cons of changing the KPI angle?

Also how much caster is too much for an S14 200SX? I have adjustable strut tops AND caster rods so i can get a LOT. Would 9.5 degrees be OK?

260DET Experienced

260DET

Posted
Posted

Interesting question so a bump and some comment.

Camber pins attach the strut to the stub axle assembly? I'm not right up on KPI but its angle can affect steering feel and potential kickback I believe. But what I'd do is physically check what the various settings do ie rotate the steering and observe/measure what angles and changes are involved. Providing you know what you want this seems to be a practical way to approach it.

Caster? Tied in with the above a bit isn't it, ~7-8 degrees?

Sydneykid Grand Master

Sydneykid

Posted
Posted
I'm trying to make my car's suspension have the least amount of compromises possible. I have camber pins AND adjustable strut tops so I can adjust KPI and camber separately. I was thinking i'll set it up for the least possible amount of KPI angle to have the least amount of camber loss and jacking from the KPI when turning. What are the other pros/cons of changing the KPI angle?

Also how much caster is too much for an S14 200SX? I have adjustable strut tops AND caster rods so i can get a LOT. Would 9.5 degrees be OK?

Are you substituting KPI for SAI? If so, changing camber at the upright (hub) with camber pins makes no real difference to SAI. SAI doesn't care what you do between the 2 pivot points, moving the pivot points themselves is what is important. For symplicity of tuning you are best thinking of caster and SAI as linked. ie; more caster = more SAI. One of the advantages of caster is the jacking effect, you most certainly don't want to minimise it.

To answer the question regarding how much caster, it is hard to have too much caster. But ultimately it depends on what you are doing with the car and what tyres you are running. So there is no one correct answer for all situations.

Cheers

Gary

bradsm87 Proficient

bradsm87

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Posted (edited)

By SAI, I mean in the outwards direction rather than forwards and backwards. An example of reducing the SAI but keeping the same camber:

Move the camber tops to the full positive camber position then adjust the camber back to where it was using camber pins.

I want to increase my caster to reduce the need for as much static camber to get better grip when braking on the track. I think I can get a LOT by moving the caster rods to the shortest possible length and adjusting the strut tops back as far as they will go.

I have Tein Mono Flex coilovers and Ikeya formula roll centre adjuster LCA's on the front. If I can get 10 degrees of caster, would 2 degrees neg camber on the front be enough for track work?

Edited by bradsm87
Amec Experienced

Amec

Posted
Posted

well, go out to the track, armed with a point and shoot style infra red temp gauge.

come back in to the pits, look at your tyre wear pattern. measure the temps at the inside, middle, and outside of the tyres. try and keep the temps as even as possible by adjusting tyre pressure.

suspension setup really is mostly experimentation to see what works best for YOUR car.

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