If I change the tire size on my 400 to run bigger tires in back and front what size sprockets am I going to have to get to keep the gearing the same.
22" rear holeshot xct's
holeshots on front bigger than stock.
this is for ground clearance on rocks and stuff.

 

I am running 22" all tracks on my 400EX with stock gearing. It works great, and I do A LOT of hill climbing. I use second instead of third, and I can out climb any other 400EX around here, so far...

 

I just yesterday put 22 inch tires on mine. I think it is just right.

 

I think if you dropped one tooth on your c/s sprocket, you'd be in the ball park. I did it the other way around on my Warrior, going from 22" rears to 20". I tried a 14 instead of a 13 & it was about the same as stock. I now run a 15 for greater top end.
I don't know that I'd alter the front tire size, tho, since most clearance problems are concerned with the rotor or rear sprocket.

 

The 400EX stock is geared kinda low anyway unless your riding a lot of realy tight slow trails or sand dunes. The extra tire diameter will help your top speed and ground clearance and you probably won't feel the difference in acceleration. If you do want to change, I would go two teeth bigger in the rear, one tooth on the countershaft makes a big difference in gearing, two teeth bigger in the rear might not be so dramatic.

 

I also have the 22" XCTs on back and 23" holeshots on front .
I put a 14 tooth front sprocket on mine and it helped out alot.
It seeed like my 400 bogged a little bit in the tight trails in harescrambles with the heavy XCTs on the bike.

Rdogg '99 400EX
#46 MHSCA