Lean angle in a corner affects two things: how tight you can corner and how much grip you have.
Stand the bike up and you’ll have loads of grip but your turning circle will be large, hence you can’t corner as fast. Lean it on its side and your turning circle will be small, but you may run off the edge of the tread and lose grip.
Lean angle is therefore a balance between grip and corner speed, and is affected by your tyres, chassis, track conditions, confidence, etc.
Typically I’ve found that with yellow inserts and PMT 200’s, my bikes have been able to run around 28 – 30⁰ from horizontal comfortably in the dry, but any more than that and I’ll lose the back end on corner exit or the front end mid-corner. Firmer insert tyres help here, making the bike more predictable up to more like 24-25⁰ when conditions allow. The difference in lap times with only a couple of extra degrees lean can be quite significant, so it’s well worth testing where the limit is during free practice.
One of the early record holders at Aldershot also used to say that depending on the track, you can actually go too far: if you need fast left-right-left-right flick-ability, then excessive lean can slow down your rotation, meaning although you are fast on an open sweeping corner, you’re slower through a tight infield section. Ultimately, it’s finding the balance that suits the whole track, not just one corner.
On a stock bike with a lightly loaded front tyre, you can struggle to get sufficient grip at extreme lean angles for a couple of laps, with a superbike with more power at the back and a brake on the front, you work the tyres harder and can get them up to temperature more quickly.
On the suspension side of things, what’s important is good balance front-to-rear so that the geometry doesn’t change too much in a corner. Lots of fore-aft pitching and head shake can limit how much lean you can successfully get away with. If the chassis is well controlled, then you may find you can run a degree or two extra lean without spinning out.
In the cold and wet, I find that lean angles of 36⁰ or more may be needed, with up to 40 -45⁰ in the extreme, but an RC bike has a massive turning circle at that level of lean and certainly won’t be quick.
In summary, the amount of lean you can use depends on your chassis, tyres, track conditions and how confident you are with the bike on the limit. My personal preference is to go slightly cautious and finish without crashing, rather than lose time waiting for Marshalls – the trick is to be only just cautious enough, otherwise you could be losing several tenths per lap to your more confident (or simply more talented ) rivals!