I have poor arch support, and when I push hard on the pedals my knees often hit the top tube. I’m trying to correct this as an attempt to sort cronic hip pain / lower back

I’ve had some success with using insoles and spec in shoe forefront wedges.

I’ve bought some vectors and have been experimenting on the turbo so see if I can reduce this offset through combinations of inshoe wedges / pedal wedges and insoles.

By using much better insoles with much higher arches I’m at a +11 / +9 offset (it was over +40)

So imagine my feet are natural tilted to the outside of the pedal, amd I want to create a flater interface with the pedal at the foot, (underpower this means the knee motion is vertical)

What is better? To wedge the inside of the foot to try to build up the ‘gap’ or to wedge the outside of the foot to try to mechanically tilt the foot more in the plain it needs to be?

(yes I know go see a professional fitter, at this time I do not a day free to drive somewhere, and spend a few hours getting fitted – but I do have regular 6am turbo sessions to experiement with)

both.
i had the same issue, i now have custom footbeds with one specialised undersole wedge and cleat wedges.
those are for my road shoes.
for spd’s i use just the specialised green insoles with a wedge underneath that.the natural float of the cleat means i dont need the cleat wedge (do they even do them for spd?)

I use G8 Perfomance 2620’s with heel wedges to better affect than cleat wedging but
that’s just my bizarre feeet for you 🙂
to answer the direction question though … i use a heel wedge that is thicker on the
inside edge, nearest the crank to roll the leg outward and straighten the knee track as
mine used to drop in.
I’ve also found that excess arch support made me “over compensate” and the knee tracked
in at the top of the stroke !
Took some late night reading, videos and emails to various sources before the solution
was found.
I also found that wedging the spd cleat created a “rocking” sensation as the shoe was nolonger
in contact with the pedal in the normal resting state (inboard edge was lifted slightly
clear of the pedal body)

actually i re-read your question.

you need to get your knee tracking in a straight line, its not about levelling your foot out, your foot just needs to be at an angle to keep your knee straight.

i would visit a good sports physio with cycling experience and a static bike set-up if you can though. best thing i ever did, i had a muscle imbalance in my thigh due to the mis-tracking, i could see the muscle build up after a few weeks of riding with the shims and straight knees, got rid of of some its pain too.

if your knees are hitting the crossbar, correction at the foot (even if that was a thing – maybe it is, I dunno) would surely involve either tilting the outside edge further down or maybe rotating the cleat so the toes point out more (IANABF)

I have flat feet and tilty-outy feet but just use spesh green insoles these days – used to use those underfoot wedges but like you couldn’t work out whether to correct the “failing” or support it.

I do also have my cleats set to ride a bit “duck” as opposed to “pigeon”

I’d have gone to a physio if the above hadn’t worked

[ETA: I have ded loose joints and so I suppose it may be that I can tolerate imperfect positions better than most people]

Thanks for the comments, I’ve just started using G8 insoles after reading about them on Steve hoggs site, I’ve been increasing the arch support every couple of turbos and up to the biggest arch support so far. I’ve played with cleat wedges but seem to get a little pain at the ankle / Achilles so have reduced numbers. So far I’ve put the thicker bit on the inside with the idea of filling the gap left by a tilting foot.

I’ll order some heel wedges and see how that effects things.

My knees track fine when spinning, and interestingly when standing, but when seated and start putting power down for a time the knees start to mtrack inward which I think is my arch collapsing, I’ve tried high arch support before but they always caused cramp the flex in the g8s seem to help with this

Haven’t tried duck foot setup, maybe that’s the next step after trying the heel wedge