Is there some formula to determine stem length to handlebar width when upgrading handlebar?

WorksInTheory
Edited Date/Time 12/21/2019 5:19pm
I thought I'd give my old Trek Fuel 98 a little upgrade. After jumping off my new Trail bike and onto my old Trek, I was shocked how narrow my handlebars are (620mm). So I thought I'd upgrade the handlebars, though not as much as the 780mm that is on my Rocky Mtn Altitude.

I decided on 720mm Rise: 15mm rise, Up Sweep: 5° Back Sweep: 8°. I don't race this bike - just for riding around not on the mountain. Just researching and understanding bar width hurt my head but just as I was about to click buy, I came across articles that said, oh now that you've gone with wider bars, you need to shorten your stem. Aaaaghhhhh!

Anyways so I measured (I hope correctly), and I believe my stem is about 90-100mm. Is there some formula to determine stem length to handlebar width, etc?

Thanks for the help.
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stringbean 10/31/2019 12:04pm
10/31/2019 12:04pm
Thats called marketing

If its an older bike just get the bars, if it feels like crap look at changing the stem.
dirtyberd
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dirtyberd 10/31/2019 12:33pm
10/31/2019 12:33pm
I like my mountain bikes to have the same fit regardless of discipline so I can just jump on and go. This means the same saddle height, saddle set back, handlebar width, handlebar reach (I use nose of saddle to center of stem/handlebar junction AND nose of saddle to center of the end of bars) and handlebar drop. If the bikes are similar in size, I can easily obtain the same fit by switching out handlebars and stem. BUT I will say that it is near impossible to guess which handlebar and stem combo will achieve this - I conveniently have a bunch of extra crap laying around for this reason. In the case you do not have a bunch of extras, local bike shops rule.

i wish there was an easier way. i may be wrong but i feel like all brands measure different which is half the reason why there is no magic formula.
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WorksInTheory 11/1/2019 11:57am
11/1/2019 11:57am
Thanks @stringbean and @dirtyberd for the replies.

I know the best approach is to iterate but I kind of just want to order it and get on with it. That being said, things are making sense to me now - I have had a few issues with riding this bike on a trail as well as going OTB and now I understand it's because 1) the stem puts the weight differently and in this case too much to the front which is good for pedaling and climbing so I would need to ride this differently than another bike. For example, tried to do an endo trick and flew over on this bike as well as when climbing if I don't lean forward on it, the front end pops up and all over the place alot especially when hitting roots etc.

Kind of learning what does what - fascinating.
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bturman
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bturman 11/2/2019 11:39am
11/2/2019 11:39am
Think about the triangle your arms and the bar make. As you drastically widen the bars, you'll likely need to shorten the stem to maintain a similar upper body position while riding. Going way wider without a shorter stem will pull you forward.

Try slamming your seat a few cm further forward or shifting your weight forward to help with the front end popping up on climbs.
2
WorksInTheory 11/5/2019 9:48am
11/5/2019 9:48am
Hahaha just spent hours staring at this pic scarface and interpreting it.. ;-) - just kidding I get it.
WorksInTheory 12/21/2019 12:57pm
12/21/2019 12:57pm
Okay so I ended up buying a 720mm that's 31.8mm with a 70mm rise.
Had to buy a new stem anyways to fit the 31.8mm as the old one was the 25.xmm. So got one that was 7 degrees and 60mm (the old one was 90 or 100mm).

It's raining a lot so haven't had a chance to take it for a proper ride but just a quick spin outside seems like it feels good (also put on new grips with slight wings for support). Don't have a point of view on turning and handling yet - feel like yes it's different than 600mm and 100mm stem but just needs getting used to.

Bought a 45mm stem too just in case but feel like would be too short and not over the wheel properly. But I haven't tried it yet either. It's a pain as one thing I didn't account for was the cabling - it was cut to go over the end of a shorter stem and I had to really stretch it to reach the end of the new handle bars to slide on. This old bike has a combo brake and shifter component and it's the latching aroundn the handle bar doesn't come off in two pieces so you do have to slide on.

Open to thoughts on what to look for and consider as I test this new set up.

I have a Rocky Mountain Altitude L that is my main all trail bike and that is 780 but the geometry is right for that, but thinking cutting down to 760. I am 5'10 1/2 all torso (30 inseam) but short arms (like a 33/34 shirt). I think shoulders are like 19", I wear a 44R suit jacket in this new world of everything slim. Wher eI bought the bike, the guy in the shop said, "you are about my size, I ride 780 so that's about right for you" so that's what we went with.
Heist30
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Heist30 12/21/2019 5:19pm
12/21/2019 5:19pm
I got shorter arms(32 shirt), run 38 rise 780 bar w/35 stem on ‘18 Jeffsy and 80 rise 760 bar w/40 stem on ‘14 Stache. Your 720 w/60 stem should be about right

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