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Stem length on custom frame

Posted: Wed Jul 17, 2019 4:51 pm
by steventran
I'm getting a custom frame built and I'm trying to decide on stem length as I develop the geometry.

Assuming I can adjust everything else to get the stack, reach, and trail within an acceptable range, which of the following would look the most aesthetically balanced?

-555mm effective top tube with 100mm stem
-550mm effective top tube with 100mm stem
-545mm effective top tube with 110mm stem
-540mm effective top tube with 110mm stem

Thanks!

Re: Stem length on custom frame

Posted: Wed Jul 17, 2019 5:41 pm
by DJT21
You give your numbers to the bike builder and they determine the correct length stem. There's quite a difference between a 540mm top tube and a 555mm top tube!

Re: Stem length on custom frame

Posted: Wed Jul 17, 2019 5:41 pm
by Weenie

Re: Stem length on custom frame

Posted: Wed Jul 17, 2019 6:58 pm
by pdlpsher1
Besides aesthetics, the TT and stem lengths are based on several factors including toe-overlap and the trail. Assuming you can get trail and toe-overlap to remain constant, I'd pick 540mm TT and 110mm stem. My custom bike has 540mm TT and 120mm stem. Hope this helps.

Re: Stem length on custom frame

Posted: Wed Jul 17, 2019 7:35 pm
by Broady
Yeah I went from 560 / 110 to 545 / 120 on my custom and it feels / looks perfect.

Does your builder not require you to go for a fit?

Re: Stem length on custom frame

Posted: Wed Jul 17, 2019 7:40 pm
by Catagory6
dont forget about handle bar reach
theres a big diff between 70mm and 85mm too

Re: Stem length on custom frame

Posted: Thu Jul 18, 2019 3:40 pm
by steventran
I have been fitted, but building around my handlebar stack and reach still leaves a lot of room for modifying things for handling and aesthetics.

The seat tube angle and the stem are the reasons for the large range in effective top tubes.

It seems the consensus is that a 110mm stem would look better than a 100mm stem on a custom geometry frame with a top tube longer than 540mm, fit and handling being roughly equal.

Thanks everyone!


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Re: Stem length on custom frame

Posted: Thu Jul 18, 2019 4:10 pm
by onemanpeloton
this is an interesting question. I've often wondered, if stem length is generally changed to alter the handling characteristics, why do smaller bikes come with shorter stems? Why isnt, for example, the reach of the frame adjusted in such a way that a 50cm frame and a 60cm both use a 100mm stem (and therefore presumably have the same handling characteristics)

Stem length on custom frame

Posted: Thu Jul 18, 2019 5:21 pm
by pdlpsher1
Smaller frames have a toe-overlap issue. Also there are two current trends not helping with toe-overlap, namely running wide/tall tires and a rearward cleat position. I run 28mm tires, have a rearward clear position, and have a $500 pair of shoes, haha. And yes I have toe-overlap and I have to be extremely careful about it so my shoes won’t get ruined. Often you’ll see smaller bikes come with 90mm stems so that the TT can be lengthened to reduce toe-overlap. Larger frames aren’t limited by toe-overlap so they can use longer stems to keep the wheelbase short.


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Re: Stem length on custom frame

Posted: Thu Jul 18, 2019 5:58 pm
by steventran
Perhaps I should ask the question this way:

Would a 100mm stem look too small on a frame with a 550mm or 555mm effective top tube?

I'm not going for a pro look, just a balanced look. Again, I can keep my handlebar stack and reach constant. The ground trail will be within a range I'm okay with.

Re: Stem length on custom frame

Posted: Thu Jul 18, 2019 6:37 pm
by biwa
steventran wrote:
Thu Jul 18, 2019 5:58 pm
Would a 100mm stem look too small on a frame with a 550mm or 555mm effective top tube?
No if you're riding the bike, nobody will notice. Maybe if the bike stands still, to someone who's used to the pro look.

Re: Stem length on custom frame

Posted: Thu Jul 18, 2019 6:47 pm
by pdlpsher1
The pros are now on 140-150mm stems. Your 100-110mm will look short. Funny that you say you don’t care about the pro look but ask if your stem will look Ok


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Re: Stem length on custom frame

Posted: Thu Jul 18, 2019 7:02 pm
by steventran
To be honest, I do like to look at my bikes when I'm not riding them, and it bothers me when something looks a little out of balance to me. This is why I'm going custom.

FWIW, I think pro bikes look exaggerated. I'm looking to design a frame around my fit that has a nice visual balance once built up as a complete bike, but I don't care about having a lot of seat post showing, a ton of saddle to bar drop, a slammed stem, etc.

Re: Stem length on custom frame

Posted: Thu Jul 18, 2019 7:06 pm
by MoPho
pdlpsher1 wrote:
Thu Jul 18, 2019 5:21 pm
Smaller frames have a toe-overlap issue. Also there are two current trends not helping with toe-overlap, namely running wide/tall tires and a rearward cleat position. I run 28mm tires, have a rearward clear position, and have a $500 pair of shoes, haha. And yes I have toe-overlap and I have to be extremely careful about it so my shoes won’t get ruined. Often you’ll see smaller bikes come with 90mm stems so that the TT can be lengthened to reduce toe-overlap. Larger frames aren’t limited by toe-overlap so they can use longer stems to keep the wheelbase short.

Besides when making a U-turn or doing a trackstand, why is toe overlap an issue? :noidea:



.

Re: Stem length on custom frame

Posted: Thu Jul 18, 2019 7:06 pm
by pdlpsher1
I agree. I’m not into the Pro look either even if I can ride a bike with a 150mm stem. I would go for the 110mm stem if I were you. As you get older you might lose flexibility and revert back to a 100mm stem.


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Re: Stem length on custom frame

Posted: Thu Jul 18, 2019 7:13 pm
by steventran
Pedaling up tight switchbacks has been an issue for me. Going slow and getting your foot/wheel caught is not fun. This obviously won't be an issue for people who don't ride them.
MoPho wrote:
Thu Jul 18, 2019 7:06 pm
pdlpsher1 wrote:
Thu Jul 18, 2019 5:21 pm
Smaller frames have a toe-overlap issue. Also there are two current trends not helping with toe-overlap, namely running wide/tall tires and a rearward cleat position. I run 28mm tires, have a rearward clear position, and have a $500 pair of shoes, haha. And yes I have toe-overlap and I have to be extremely careful about it so my shoes won’t get ruined. Often you’ll see smaller bikes come with 90mm stems so that the TT can be lengthened to reduce toe-overlap. Larger frames aren’t limited by toe-overlap so they can use longer stems to keep the wheelbase short.

Besides when making a U-turn or doing a trackstand, why is toe overlap an issue? :noidea:



.

Re: Stem length on custom frame

Posted: Thu Jul 18, 2019 7:13 pm
by Weenie