do you know how to know when for example the toe is 4mm and how do i change toe on my chassis
By loosening and turning the tie-rods.
Also looks like you are running with no chrome seat stays, which could be why you arenât getting any lift. For X30 Jr. I would have 1 chrome seat stay on either side.
Do you have a shop or mechanic/tuner who could help you?
YouTube has some resources on all this as well:
do you think 1390 cm bask is good and 4mm toe and camber is ok. i will buy a seat stay tmr and get a laser kit to do aligmentâ
Start wherever the Praga guide says to start. 1390mm is the baseline for most karts.
Couple of thoughtsâŚ
For a class like X30 Iâd lean towards running full rear track (140CM) and making adjustments around that to make it work.
Keep in mind that you donât nessacarily always need visually noticeable âliftâ of the inside wheel. But if you feel the kart âbindingâ or understeering then you definitely need to make a change of some sort. The rule of thumb I use
Understanding what kind of turns (Fast, med, slow\tight) and what part (Entry, apex, exit) of those youâre experience issue can help narrow down the changes you make.
Example, if youâre experiencing understeer on entry then you might consider adding some caster or widening the front. This will help the rear unload mechanically.
On exit, caster is not as much of a factor on controlling load on the inside wheel, other than keeping in mind that more caster tends to lift the inside rear more, but also âdumpâ it down sooner and harder. So to control the inside wheel on exit you are looking at things like chassis stiffness (# seat struts, bearing carriers) and also camber.
Hereâs a good video on how camber can work with unloading the rear on exit:
Also recommend you watch Colâs (Kracer) other videos on his channel in addition to TJâs. Thereâs some really great stuff.
All that said, if the kart feels bound\understeery at 136CM, then I tend to agree that your seat may be too far to the rear.
Final thought: It might be time to find a Praga resource that can help you trackside as well. I say that with reservation because this discussion helps lots of people who are reading this too 
OK that was more than a couple of thoughts.
i watched my fotage from the sessions and i tend to oversteer a bit into the corner,
i also cant seem to hit the apex in beacuse i cant seem to steer in and the kart wont let me,
and some of the turn that i do for example a flat out 90 degree corner out to the straight my back wants to slide out and my front stays planted on the ground.
Put a video up on youtube and paste the link so we can take a look. Are the tires decent? That makes a big difference too.
These are contradicting handling issues. If the kart is oversteering, you should have no problem getting down to the apex, the kart has plenty of front response, and the inside rear probably is unloading too much. As James said, just because you canât see it lifting doesnât mean itâs not unloading.
If you are running a soft rear end with no seat stays and real narrow track, whatâs probably happening is you are getting a twitchy front end because the rear is so narrow, so itâs reacting quickly and then it doesnât have any seat stays to plant the outside rear tire so it just skids.
A video would help because then we could see whatâs really happening.
This is why you need to start with the neutral baseline setup according to Praga, because you have a pretty unusual setup on the kart right now and it will be hard to diagnose properly.
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tires are 1 testing day old.
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just posted a 2 min video on my yt here is the link. its not the best but it is the only one i have on hand. when i will come home i will post a better longer video.
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Bit difficult to tell on that video because the angle doesnât allow us to see the track, but like I said, I would set the kart up to Pragaâs baseline for now, and focus on improving your driving. Your braking zones seem really long, like youâre not getting the most out of the brakes, your throttle input is very choppy and on-off, rather than smooth and progressive, which will be upsetting the kart mid-corner. It also sounds like itâs quite late in a lot of the corners. And it sounds like there is a lot of coasting going on, which is almost never good in a kart.
If the driving isnât dialed in, it can be hard to diagnose the kartâs handling issues, because it could be the driving that is causing them. My YouTube channel has some more videos that relate to braking technique and general driving tips too that would be helpful.
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How do i messure front track width
Like over the wheel to other on beacuse i cant run it thrugh the axel
Like I mentioned here, most people arenât measuring the full front track width regularly, or at least I donât. But Praga probably gives you a measurement to start. Center the steering, hold a tape measure across the tops of the tires, and use a straight edge against the outer edge of each tire. Might need two people.
Do your front hubs state their length? Most of the IPK hubs will state their length.
For 70mm front hubs youâll want 3 large (10mm) spacers each side. If I find the steering a bit heavy Iâll drop that to 2 large (10mm) and 1 small (5mm) each side. Run the rear track @ 1385 - 1390.
Start with 2mm toe out on each side and -2mm of camber each side. I canât 100% tell from the photo but it looks like you might have the reduced caster (no dot) inserts in. Almost always you should run the inserts which have 1 dot on them.
Thatâs what I run with my Praga Dragon Evo 2 with Rotax
I run on 70mm front and i run 2big and 1 small spacer.
I have almost close to no camber at 1mm and caster i might get a 1° as you said
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Hi Mike,
So I ran a Praga last year and have been running on an FK this year with a team of all IPK (Praga/FK) We all run between .5 and 1 spacer in the front track depending. I agree with Shawn above, widen the rear and add the 1 dot caster spacer. Definitely want your camber to be between -1 and -2mm, same on the toe out!
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Very interesting and important point James. But it remains a question in my mind in terms of rake. Increasing rake (higher ride height at the back end than the front end) brings more load to the back or the opposite?
Rake moves the CG forward by dx = [CGy * (h_rear - h_front)]/wheelbase where dx is the forward shift of the CG, h_rear-h_front is the difference in front and rear heights, and CGy is the height of the CG prior to changing the rake. So if the rear is 1" higher than the front, your wheelbase is 40", and your CG height it 10", CG will shift forward by a whopping 0.25".
Please, feel free to check that math. I am using the âsmall angle approximationâ, so this math only holds for realistic rake angles. If you start jacking up the rear by a foot or so, youâll need proper trig.
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I know CG is extremely important in vehicles dynamics, but I´ve never calculated the effects of CG changes, so I really donât know if 0.25" is significant or not. Do you consider it a substantial change in the CG taking into account we are in a go-kart environment?
I am very unqualified to answer that, haha. My guess is it is not insignificant, BUT the change in jacking due to raising the rear 1â is probably more dominant. If you change take by dropping the front, you wonât change jacking as much.
For a rear brake only kart, high CG hurts straight line braking, so, depending on how important your braking zones are, raising the rear may hurt braking due to both the higher CG and the forward shift in CG.
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