Caster block degree

Surveyor

Member
I have a 2016 recon. Did a complete tear down and am re-assembling. I was told it was set up good for dirt, but think it was set up for concrete. The RF caster block is marked 15 degrees, but no longer has the second pin so it can be rotated. Is the original setting 15 degrees and so since it is able to be rotated I can set it to whatever I need (thinking 10) using the graduations on top? Or is there other differences in a 15 degree block and the 10 degree I think the Recon originally came with?
 

flattop1

Dawg 89
The pin locate the block at the set degrees.
Once you take the second pin out you can rotate it to what you want. No difference other the pin location that I know of .
 

JPMKarting

Site Supporter
You are confusing KPI (castor block/spindle angle) with Castor.

The lines on the top of the block, and the pin the block rotates on are for castor. Each line should be 2* increments.

KPI is king pin inclination, meaning how much of an angle the kingpin is on.
 

Surveyor

Member
So I thought I was figuring this out, but I see I still don't understand a bunch.

Looked at the L blocks and see the KPI. Looks to me that going straight it would be the same as camber, but I assume it reacts different in action.

In my simpleton mind, caster affects the speed of the changes. Camber affects the weight transfer amount. What does the KPI do. Or do I have this all wrong.

Finally what should the L blocks be on the Recon (2016). Or what was the factory blocks?
 

95 shaw

Site Supporter
So I thought I was figuring this out, but I see I still don't understand a bunch.

Looked at the L blocks and see the KPI. Looks to me that going straight it would be the same as camber, but I assume it reacts different in action.

In my simpleton mind, caster affects the speed of the changes. Camber affects the weight transfer amount. What does the KPI do. Or do I have this all wrong.

Finally what should the L blocks be on the Recon (2016). Or what was the factory blocks?
https://4cycle.com/karting/threads/spindle-angle.110398/

This may be a tough read, but what you need is there.

The drawings are good, except they do not show the actual action at the center of the contact patch.

There are several threads in this same timeframe that cover this. The biggest thing is to look at what happens at the contact patch, which is what the chassis actually sees.
 

ABR #69

Member
On Cars KPI works a little different. In terms of karts it's more of a balancing act and provides some stability, and gives wheel feel. But, it balances Camber gain and scrub radius.

It's a bit complicated to explain the way it works in Karts. But, it has a lot to do with caster, scrub radius, camber gain, and balancing front bite. It's one of the reasons karts balance right on the edge of the RF tire and if things aren't correct will obliterate the inside edge of the tire. This is part of the scrub radius deal, but it's a bit more

Older karts (Late 90's early 2000's) ran a range of 5-8 caster depending on the brand, which was built into the chassis. Then they started going up from there and made it adjustable with L blocks/heim joints. Where today 8-13 degree caster is common in higher HP situations. This helps adjust bite in the front end. Higher caster was needed to help transfer weight on the newer stiffer designs. Which is what you were originally asking about.

Now, couple that with higher cambers, and KPI creeps in. Because, KPI helps offset camber gain from high caster. Imagine it makes the arc produced less dramatic. It's sort of a package deal, stiffer chassis tend to run higher Caster, higher KPI. Camber remains roughly the same as older karts, but again with the higher caster this increased camber gain dramatically. So KPI helps to keep things in check. Since Camber gain is progressive, the different KPI give tuning options.

Shaw beat me to it, but, yeah that thread has everything in it I think. I haven't read it in a while.
 

Surveyor

Member
Thanks. I have read that post, but I just can not wrap my head around it. When I have a night to numb my mind I will work through that thread out in the garage with the kart. Maybe seeing it will help. I do appreciate the input. I will get with PRC and see which L blocks they recommend. I am sure I am not a good enough racer or tech to know better than the designer, but it is fun to try to understand.
 
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