Hey Guys,
Wondering if anyone has any opinions about 9F AMV wheels. I tried 3fs on my kart recently and the kart felt good, balance was nice but just didn’t have release off of the turn, switched to MXCs and it released off the turn better, but I’m just not a fan of the MXC feel wise.
In short, have you tried 9F rims?
If so, what’s your opinion?
Thanks!
The 9F because of the 6 air vent hole, especially when mated to the 9F hubs, will dissipate heat better particularly on a very hot day. The feel and balance of the 3F and 9F are similar but the 9F will be freer. Here is a quote from Ryan Casner, a top masters driver, on the performance of the 9F.
Quick question regarding the AMV 9Fs. When grip is low or the track is green, if you can run a higher cold pressure and still hit the recommended hot pressure, would you say they’re better than the 3F or MXC?
I’m currently using the 3Fs and looking to move to the 9Fs with the matching hubs. The only issue I have with the 3Fs is that you still need to run lower pressures in hot conditions, and they can take a bit of time to switch on.
What I’m wondering is whether the 9Fs will allow you to run a higher starting pressure so the tyres switch on quicker, while also helping to prevent them from overheating later in the run.
Technically yes, but the 3F still seems to heat up better anyway. I use the 3F as my default wheel for practice and qualifying, and switch to 9Fs for racing usually.
If you are bumping up pressures with the 9F, it will help keep the tire cool, but you also are increasing the stiffness of the tire at the same time, which makes tire surface temps higher and core temps lower. I’d prefer to keep the tire in it’s working range of pressure and use the wheels to compensate for track temperature or session length.
Have you ever measured tire spring rate as a function of pressure? There are some rules of thumb on car stuff, but I’ve never seen any data or testing on it with karts.
I haven’t measured anything, but I would imagine it’s a little different in theory since the kart doesn’t have actual springs, and the tire itself serves as your spring rate.
You can certainly feel when you are too high or too low on tire pressure when viewing it in terms of kart dynamics and leaving temperature control out of it.
I have a range of pressure I like to stay in for the tires I race on, not only for the warm-up properties, but also in terms of ‘spring rate’. There is a low limit pressure that will cause the tire to start folding over on the sidewall too much and induce certain handling problems, and there is a high limit pressure that will stiffen the tire up so much that it poses another set of handling problems.
People will put a tire on a spring rater or on a scale and apply pressure like it’s through a hub and then see how much the tire compresses. It is the rate of the tire, not the car, so it would be the same on a car as a kart.
Intercomp makes them for karts https://www.intercompracing.com/kart-tire-tester-p-115.html
