Go with a 13 in front and leave the back alone you can go back and forth between the stocker and the 13 for your different conditions and not need a new chain. And don't shut your bike off going down a hill that would be dumb.

 

Thanks

I am not a complete nube when it comes to riding downhill, I raced downhill mountain bikes for 10 years. This was the steepest and longest hill Ive ever been on and I just couldn't slow down.

I was riding in the high desert; super rocky, a lot of snow, some sand, some mud.

So, in many places there was no way of using any brakes at all or I would slide all over the place.

I ordered a 13 front and a 47 rear. I am going to try out the 13 and see if that works well enough. If not I can put on the 47.

 

one of the steepest hills i come down regularly is kearny above broadway (30% grade)...shown in many movies...have 15/39 gearing...on a klx250sf....no problems cruising down on 1st gear....



actually come down a short section on romolo that is steeper than kearny..just to get to kearny...romolo is so steep, lot of longer trucks and cars actually get stuck when they reach the bottom...notice all the scrape marks on the road....

 

That's nuts. Almost as steep side to side as down.

Have you tried something that steep UP?

 

there is a reason why all the steep san francisco streets are one-way down only...to get up there..you have to go around the block to get to the top...once, i tried to take a short cut straight up late at night...my clutch shattered into pieces....

 

Brakes react differently on asphalt than offroad if you start going too fast....

Think about going whatever speed your going down Kearny and add rocks, ruts, loose dirt and a little snow.

And the stuff we went down was steeper than Kearny, I lived in SF for about ten years so I do know from experience.

 

If you can't use your front brakes to the point the front locks up a bit prior to you letting off to regroup, changing your rear gearing isn't going to slow you down. I go down stuff in the desert where the rolling rocks, sand, and silt just don't allow much traction. Rear end locked, front wheel alternately locking and unlocking, and still picking up speed. You just have to stay relaxed and make suggestions to the bike as to what line you'd like to take, and then deal with what line the bike and terrain dictate you will take instead. Again, changing teeth on the gearing doesn't change this technique one bit.

 

"You just have to stay relaxed and make suggestions to the bike as to what line you'd like to take, and then deal with what line the bike and terrain dictate you will take instead."

And that is going downhill on loose terrain in a nutshell. Well put Blackheart58.

"make suggestions to the bike" LOL , but too true.