Interesting feedback on the A. For me it’s my new baseline. It’s soft enough it works up here in low grip. But stiff enough to test wider to see if you’re getting to the threshold of stiffer axle
I’m with you here. The cut Medium worked well at the time, so I went to a cut Hard for Sunday and I think found diminishing returns…track wasn’t quite grippy enough for that axle to work well. Kart felt pretty good for the final on Sunday, just lacked speed.
1 Like
Narrowing the rear increases the weight transfer to the OR, thereby increasing side bite and hopefully lifting the IR the right amount and duration.
Caveat: I’m not all familiar with Sport Karts and actually 80% of my experience is OTK. I may be wrong but these two respond differently to changes that make up lap time.
Yeah same boat. And I wasn’t a mile off, just about 0.6 which was better than the 1.0 I was on Saturday. Just was an absolute thrash to find those 0.4 and still felt like the kart was butt lol.
Intersting…
How do you go about figuring out that you need more pressure?
The tire wouldn’t come in and you’d be sliding everywhere the entire session. Because there’s no friction on the surface, the tire just slides around and never bites, so the core of the tire doesn’t get hot quickly.
My thought is with the increased heat generation from the MXJ wheel, maybe you could get away with a lower pressure that would still generate heat.
1 Like
Interestingly a few weeks back I raced on a track that had very little grip, very old asphalt (killed tires) and basically was dirty all weekend and was never able to get rubber down. I tried a fair number of adjustments only for basically no change, the tires just wouldn’t grip the track. This is in KZ mind you, and we were all looking for drive off, side bite wasn’t there either. I normally always run higher pressures than most my competition because I don’t find confidence in the feeling when the sidewall is folding under too much, but at this race I went lower than I ever had in the final on Sunday at 6psi (Le Cont Whites) and it did seem to help a little. Even as low as I went I didn’t get that sidewall flex feeling I’m used to when going less than 9psi, I think the track just didn’t offer the grip so the tires just didn’t flex enough to give me that feeling. Was a a very odd weekend for tuning.
Maybe a dumb tuning direction, but couldn’t you also try dropping the pressures to get the tire to flex and dig? You were on Reds correct? One cool slippery day at GoPro in KA on reds I kept going up and up with no luck to say 18-20psi hot. Came in and they had that polished sanded look. Said F it, and dropped them to 7-8psi cold and they hooked up. Actually got them nice and hot on the tread near the sidewalls but the center was only warm. Actually had that melted rubber look, only as much as an MG Red can have that is.
Edit: I will say it did have it’s draw back with a nice hop in the double rights, but it more than made up for it everywhere else.
1 Like
This was my thott as well. I just didn’t opine because it’s a sim thing. Requires a different, gentler approach but results in big side bite, slightly delayed by sidewall deformation. Interesting to hear it from IRL karter as idea.
I personally hate driving a kart like that. It messes with my timing cause you turn in. It rotates partially, tire rolls over and feels like it’s rotating but it’s just the tire.
But saying all that something maybe I should work on as it’s a tuning option I pretty much just overlook cause I don’t have the confidence I can drive it fast.
1 Like
Yeah like I said I did kind of want to try going down to like 13 or lower and put the MXJs on to get heat in and let the tire flex. It was on my list of things to try, but that list was very long… We missed two sessions on Friday after it rained Friday morning and skipped the first session and then we lost a chain another session, and then we had a throttle cable issue another session. If we had those two sessions back we might’ve had time to try more things.
I ran between 16-21 psi for the weekend and there was noticeable warm-up issues once I got down to 16, so I was pretty concerned that 13 would be tough. Maybe an extreme drop like to 8 or so would’ve been a worthwhile experiment. By Sunday we had swapped wheels like five times and weren’t super excited to do it again, and I think the MXCs on low pressure would’ve just never come in.
And just to emphasize, this track surface is quite a bit different than GoPro’s. Everything everyone is suggesting here is good stuff, in most normal conditions, and it’s all the stuff I ran through over the course of the weekend too. The kart was just not reacting to these changes as it normally would, because of the track.
Totally understand, apples-oranges. Just one of those things that blew my mind. I had always ran the Reds in the 14-16 psi hot range, but was converted to a 10-12 psi hot kinda guy on Reds after that. Was always on the threshold of binding/hopping binding but got so much dig on entry I just rolled with it.
Edit: Just reread your post. You couldn’t turn them on at 16psi cold?! And we’re going out at 20ish cold?
We were running Yellows at 20psi cold at times…
Correct. Like I said, unusual track surface!
Just a couple years back at RA we were literally running a rain setup with our drivers at the time, and 25+ psi for pressures. Max front width, full narrow rear, Q axle, vertical front bar, max caster… And all our drivers were top 5 in class that weekend.
1 Like
I felt like we were able to get our kart to work pretty well through the slow flat parts of the track throughout most of the weekend, but struggled to get the rear to bite in the faster parts with elevation further up the hill. We actually didn’t deviate much from baseline. We played a little bit with caster and rear track width to control lift and then tried some different axles and moved some weight around to settle the rear down later in the weekend. By the final Sunday we mostly fixed the oversteer on entry but I then started feeling like the rear was over-stuck on exit. We also ran pretty high pressures like everyone else - mostly hung around 13 psi on yellows and even that seemed like it might’ve been just a little on the low side seeing how we came in relative to everyone else.
How weird. I guess my thought process would be going higher and higher isn’t working then perhaps you’ve got too little rubber in contact and can’t work the tire. By dumping the air pressures you may not get the tread up to the same temp, but more rubber in contact = more better? 
Hard to combo that with a wheel change at the same time. Would be difficult to say which one did/didn’t work.
I can’t imagine running reds let alone yellows at that high of a pressure, must have felt like driving around on overinflated basketballs.
What did your tires look like after the race?
Overall they looked good. Will post a photo once I’m back home tonight.
14-20 psi did not look any different - dullish, not shiny or moist looking. At 20 contact patch on RF is noticeably smaller than normal.
1 Like
Same. Tire looked like it was working as intended at 20-ish psi, just smaller contact patch. Agree on the RF. I had put two dots of positive camber in on Sunday to help fatten the contact patch. I wasn’t getting wear on the outside dot. And it almost looked like I was picking up rubber on that tire. I think it has to down with the higher pressure and the camber/drop for some of the corners.
Watching the onboards it looked like the sort of track were wild tire pressure would be needed. Either 20psi or 6psi lol.