Big Bore gearing

[The norm]

So l stepped up to a 391 from a 310 last year and need to re-gear. I was running a 42t rear sprocket and a 13t front. I know that is really low gearing, but keep in mind that I am 285lbs and was riding a 310! I feel like I now have enough power to go to different gearing. I only ride this R in the dunes and I will be doing a lot of steep tree shots. So I don't want to be doing a ton of shifting on the hill climbs like I have to do now with 13/42 sprockets.
My builder (Pete) suggested 15/38. I want all you guys with Big Bores to chime in with your go to sprocket set up. Some of you like to hit the same sand as me and do all the same tree shots so your input will be appreciated.
Thanks
Loren

[Michael88R]

I think I’d try 14/38 first but I’ve never ridden a 391.  Could even go down to a 36 or 37.  I run 14/40 on my 330.  Last year in Oregon I was feeling like maybe I should throw the 13 back on.  Oregon dunes are definitely a different challenge.

[havinnoj]

Hey Loren - good question.  I used to run that gearing (well 12-39) on 310 motors and was about perfect. Still do on the spare with bigger rear tires. 

On the 443 I run 14-38.  Pete recommended the same to me initially and the motor could pull it but definitely needed to keep revs up on hills and such.   I could go to 14-37 pretty easily and 14-36 would probably pull just fine for my riding style assuming I was using a 69-71" rollout tire.  Obviously going bigger tires is like taller gearing.  And going to 15 tooth front with UPP case saver requires quite a bit of modification. 

I'd think 13-36 or 14-39 ballpark would be good for you to start Loren. 

Use the gearing & tire calc here (have to manually enter tire diameter and shows rollout which is really what we care about, I should probably update that). 
http://trx250r.org/GearRatioCalculator.html

[Tbone07]

I'm not making as much power as you with my 350, but I weigh a bit less than you as well (255). I run 14/38 for woods/play riding, which I think will work well for you.

[The norm]

I think the 21" haulers I am running have a 69" rollout. I really like the tire so don't want to change. I do know that I may have to go to a 10 paddle from the 9 paddle. I am going to try re-gearing first. I just felt like I was "blowing " the tires off on hillclimbs. I was hitting 3rd gear on climbs where 2nd should be the right gear.
Thanks for the input fellas
Loren

[Michael88R]

When you hit third gear, how did it feel?  I usually try to go down into those tree shots in 2nd and then up shift to 3rd climbing out depending on how it feels.  If it’s a short one, real steep or has curves, I’ll stay in second.

[The norm]

Seems like I needed more.  It definitely wouldn't pull 4th lol. Gene was in 2nd on his puma on the same tree shot. He is geared differently, but I can't remember what he is running