RXV Brakes "Squishy"

[bradpinkston]

I've been working on restoring a 2008 RXV. I've lifted it with a 6" RHOX lift kit and converted to 6 x 8v configuration. After finishing all the work and getting it on the road I'm noticing some issues with the braking. The engine brake has been replaced, but there is almost no braking until the pedal is fully depressed. It feels a lot like what you'd expect if you have air in a hydraulic brake line.

Is this a common problem? Does anyone have advice?

I'm planning my next step to test the rotary position sensor for the brake pedal.

[cgtech]

I'm betting it's because of the large tires. Stick a set of stock size ones on there to test.

[BobBoyce]

I concur with cgtech. Tires larger than 20.5" diameter take the effective gear ratio outside of the valid range for the VCL to be able to calculate motor drive current and regen braking properly. This is due to RXVs only having regen brakes. The motor brake will get ruined fairly quickly if you keep pressing the brake pedal far enough to engage it. It was intended as a parking brake only, not a service brake to slow you down.

[bradpinkston]

I'll stick the stock tires back on there and test. The new tires are 23".

What is the resolution if this is the case? Can the controller be tuned to compensate?

[bradpinkston]

Cant put the original tires back on. The old rims are too small and the new lift kit spindle arm rubs on the tire.

[cgtech]

Ok, try the stock tires on the back only, just for testing. The rear wheels are the ones that affect braking.

[BobBoyce]

Originally Posted by bradpinkston

I'll stick the stock tires back on there and test. The new tires are 23".

What is the resolution if this is the case? Can the controller be tuned to compensate?

A stock Curtis RXV controller can be calibrated to work with the larger tires, at a loss of performance. Essentially, the motor is lugging trying to turn the larger tires, drawing more current than the VCLs motor maps are calibrated for. You have to recalibrate the motors RPM to speed calibration to bring it back into range, and reduce the max current limits across a lower RPM range to prevent the controller from overheating. This requires recalibration of the initial RPM value and reduce all Plus Delta offset values. The motor will still draw a bit more current than it normally would, and it will run hotter because of that, but it's ok. The temperature feedback loop will compensate by cutting back current further until the motor cools. We are more concerned with the controller overheating. The recalibration just allows the controller to properly regulate current once again with that new VCL calibration. Both coast and braking regen rates must be increased as well to compensate for the lower RPM range that the motor will be now running at. If you do nothing, this increased current to the motor will result in repeated controller overheats, controller overtemp shutdowns on longer drives, and eventual controller failure. The E-Z-GO VCL in the Curtis RXV controllers can handle up to a 20.5" tire without recalibration.

Switching to the Curtis 350 Amp upgrade controller will prevent controller overheat and failure, but recalibration will still need to be done because it comes from E-Z-GO programmed with the identical VCL settings as the stock 235 Amp controller. The only difference is the 350 Amp controller will not need to have the current reduced like the stock controller does. The motor will still run hotter on long runs, but the motor temperature sensor tells the controller to cut back on power when the motor heats up too much.

[bradpinkston]

I assume this is a Danaher controller since it is a 2008. Do the options stay the same for reconfiguration?

[BobBoyce]

Originally Posted by bradpinkston

I assume this is a Danaher controller since it is a 2008. Do the options stay the same for reconfiguration?

No, the Danaher is not reconfigurable the same. You'll likely be switching to a Curtis when it fails since they've been obsoleted for 6 years. cgtech can tell you more. I have a Danaher handset but not a test bench for them.

[bradpinkston]

I replaced the rear wheels with the stock wheels and it seems to be very normal compared to the new configuration.

Would doing the controller speed upgrade on the Danaher help this? What about making it worse?

Any references to how to do the Curtis controller swap?