New to the gravel world and need help

Hello,

Welcome to the gravel world! Once you are able to sort out your bike it will be worth it!

If you have rim brakes you are not going to be able to switch to 650B wheels; the change in rim/braking surface location is too great. It sounds like your best bet is going to squeeze in whatever size tire you can and start from there. If you get hooked, you will most likely find yourself wanting a new frameset/bike..

Feel free to ask questions here, it is a great community and everyone understands that lots of folks are sticking their nose in for the first time..

Twall09 wrote:

From doing lots of reading on doing a conversion, it seems like running 650b wheels with somewhere in the neighborhood of 40mm would possibly work. Does this seem feasible just in a general since for this type of conversion? Additionally, I unfortunately have rim brakes and it seems like I might need to add long reaching brakes to make up the difference in wheel size. 

It is a lot easier to convert a mountain bike to gravel (I've done it several times) than a road bike.  Even a cheap hybrid bike can often clear up to 40mm tires (I stole my daughters hybrid and did this one, as well).  Now, if you are on a budget, then you have a few options.  I had a custom climbing bike made in 2007 that barely clears 28mm in back and 25mm in front.  When I started gravel I went to wider and wider tires and finally bought a new front fork for that bike so it could share a wheel with my gravel/all-surface bike, which is a converted mtb.  Now I run a 650bx47 on the front.  I would call it a very "light gravel" bike.  The front wheel gives you all the float and control you need, but the 25mm in back bogs now pretty fast in sand (of which there is a lot around here). 
I bought a cheap chinese fork for that and have been very pleased with it.  It was about 65 bucks plus a 45 dollar trp brake.  My riding is about a 50/50 split of pavement/dirt most of the time.  You can convert from 700 to 650 as you suggested, but your braking will suffer.  If you don't have crazy hills then it may not be an issue.  The mongrel bike I mentioned has a super solid Trp spyre disc on front and a old regular rim brake caliper on back.  If you can clear a 28mm tire in 700c, then going to 650b might allow you to go as wide as 32-35 and though it sounds small, it will make a big difference.  The problem is, now you have bought:
1. new fork with new brake  
2. new wheels for front and back
3. new tires for front and back
4. new long reach rear brake.  
That is going to set you back $400 and that is if you buy inexpensive wheels.  For that amount you could go to bikesdirect and pick up a beginner's gravel bike that will already have more tire clearance.  
Or you could simply measure your frame and fork and put on the biggest tires that will fit and go ride.  It won't be perfect, but it will be exciting. 

Thanks for all the helpful advice! It’s starting to seem like it might be more money/hassle than it worth to convert my current bike. I’ll check out bikesdirect and see what I can find.