I have been driving this KZ Tony for a bit, and the brakes are so finicky. It always seems like I either have too much front or rear bias, and can’t find the sweet spot. If I try to go really deep on the brakes like a shifter requires for fast laptimes, the front end of the kart will go into a sort of self sustained vibration that dampens out by the apex, but loses me time for sure.
Curious to know if there are any older OTK brake systems that were considered better, which I could retrofit on this kart? Or if any company out there make a better brake system that bolts on? It’s sad that my 22 year old CRG has far superior and more confidence inspiring brakes than my new machine. Any suggestions are welcome. I otherwise love the way the kart drives and handles.
Are your fronts balanced? The only time i’ve really had a vibration on the front end under braking was out of balance wheels/tires. Not on an OTK, just a shifter in general.
Yeah I notice less while at speed than under braking. Some batches of tires are close enough it’s not a big deal, and some bad batches are so far out it’s crazy.
I’ve never driven an OTK shifter but I’ve heard similar complaints about the brakes being a bit finicky and/or oversensitive, which is interesting because I remember the single speed OTK brakes being quite the opposite.
I’ve experienced pretty severe front end vibration or chattering under heavy braking before when I was testing out a more aggressive pad compound for my freeline front brakes, but dialing the bias a bit rearward to compensate for the pad took the vibration away. I know you mentioned that you’ve played with the bias quite a bit, but does the vibration seem to lessen or disappear the more rearward you go with the bias?
Stick on wheel weights on the inside of the rim. I choose a side to use, push the pads back so the hub can spin freely and the heavy part of the tire should settle at the bottom. I’ll usually rotate the tire and let it settle back out and depending on how fast that happens I can gauge how out it is. If it barely meanders towards the heavy spot it’s a little out, if it quickly does so than it needs more weight on the side opposing the heavy side.
Crg shifter here. For me the front end vibration is indication that I am decelerating hard. If the front is neutral Im usually too nice with the braking and wasting time in the braking zone. I have tested several different pad compounds ,makes and for example selecting a harder compound to the front takes away the vibration. But I like to have it - it guides me to brake hard enough. Try different pad manufacturer and compounds, soft rear, hard front
Some of my kart wheel/tyre combos have used 30-40gr weight to balance them. Thats quite a chunk of metal. Tyres also rotate on the rim if one uses lube on the rim edge. I lube the wheel but wipe any excess off from the seat area. I have had rear tyres rotate 15min with lube. Without the lube the rears might rotate 2-5min or so. Obviously the balancing goes out of the window when this happens. My tyres usually need rebalancing after the day
I try to make the kart as non vibrating/shaking as possible. Anything that ads to the vibration blurs my vision/senses
Yes, I am in upper (less sensitive) setting. Everything functions “properly” and is aligned as you’ve asked. The kart has 5 hours on it.
I think I have an idea what is going on now that I’ve thought about it. It is a combination of user error and setup. I developed and honed my driving style when the chassis were super stiff in comparison to today, when the brakes weren’t as powerful, and when the tires were stickier. As such, I could really lay into the brakes and it took a lot of pedal pressure to lock up, giving me a large pressure modulation window.
Looking at the dimensions of the master piston and the caliper pistons, the OTK front brakes are WAY stronger. The front end chatter that occurs is from locking the fronts. I think the torsional natural frequency of the front end of the kart is excited by the sliding tires kind of like a bow on a violin string, causing the effect I experience.
I need to do something to make the brakes overall less sensitive so I can approach the lockup point with more precision, and I should probably try some different bars in the front end to change the stiffness and resultant vibration characteristics.
Master cylinders with bigger pistons would help, but I spent some time trying to decipher what OTK masters to use and it looks like they all have 8mm pistons. It does look like I can machine the brake pedal a tiny bit and get another adjustment hole further from the pedal pivot so I will do that in the meantime.
Not sure, but I just saw that the BS5 front caliper is a dual piston (one for each pad) setup. I wonder if they’ll bolt on my kart? Current setup is 4 piston.
I added a third adjustment hole to the brake pedal. I did some calculations and also sat in the kart and stomped it a bunch of times and I am confident it’s still plenty strong. If I like the feel I may end up making a brake pedal from scratch out of some tubular chromoly.
Update, it is way better with the brake pedal mod. I can drive it naturally and it stays nice and calm. I was able to set my fastest and most consistent practice sessions so far in it yesterday. Starting to like this kart more and more as I get it set to compliment my driving style.
