Cycle Touring in India

I've put this

together quickly as a starting point for my general direction, I'll spend a considerable amount of time adjusting it to find the quietest roads. etc. I'll probably move the starting point a little further south and maybe finish in Kerala to. The plan is to do 50 miles a day, 5 days of the week for three weeks. So about 750 miles all in.

Mostly I'm excited about the hills:

I think if you're willing to adjust it a lot as you go along that's a good starting point, though if you're really into climbing hills I'd think about a route that involves going Madurai>Kodaikanal and then from there over to Munnar on a road that's meant to be 4wd only. I think that cgoab journal I posted up involves that route. Though roads on the plains of Tamil Nadu will be pretty busy and not that fun.

One place I really liked in the hills was Marayoor - it'd be a very pleasant cycle from Munnar (which I didn't like so much).

The further North part of your tour isn't an area I know much about, but Wayanad is nice (and will have some quieter routes). You could maybe think about finishing around Kannur in Northern Kerala, spending a few days relaxing there (I can PM you a suggestion for somewhere very nice), then catching a train back along the coast from there.

I definitely wouldn't set too rigid a schedule for distances. Some days 50 miles + will be fine, other days it won't. At least one of you will get ill at some point and that'll take a few days out of your schedule.

I wouldn't count on much temperature difference between north and south - elevation will be far more significant.

My friend was planning on buying his bike in India, any thoughts or advice on this?

Don't... not if you're doing any hill climbing - you're very unlikely to get gears and it'll weigh tons. In the bigger cities you can get tolerable mountain bikes, but I still wouldn't think about touring on them.

I do know of people that have toured on Indian bikes - in their favour they're sturdy & incredibly easy to get repaired, but it'll be slow and not very comfortable. Particularly if one of you is on a higher quality bike I think it could be pretty frustrating.

One thing I was going to say - however tough/ridiculous your cycle route ends up being, you'll always meet someone (usually German) doing something 10 times as hard. In Sikkim I met a guy who'd just cycled to India via Pakistan and Iran (apparently Pakistan's horrible for cycling, Iran is great). In Darjeeling I met a German woman who was about to cycle solo through Bangladesh in the hot season. I also heard stories of a Japanese guy who'd cycled Sikkim on an Indian bike, though apparently he spent 90% of his time pushing it. Anyway, I was always reassured that nothing I did could be as bad as any of those.

As for reading, I don't know of any specific cycling books about the South, but V.S. Naipaul, Paul Theroux and Alexander Frater are all well worth reading.