Hi all,

Quick question…

Currently in the process of converting my BMC alpenchallenge hybrid to a drop bar gravel / commuter type thing

Trying to buy parts as cheap as possible for now to see if it works and then spend a few quid on decent parts if all works out well

Before commiting to buying parts I researched, took measurements, worked things out, had it planned…or so I thought…

Long story short, I THOUGHT going from 100mm stem to 70mm stem would do it, turns out, I’d need to be looking at closer to 50mm

Have bought bars, brakes, cables and tape so largely, I’m ready to go, then lining things up before tearing things apart is when I realised, I’m gonna have to buy a new stem too

Accepting the handling / steering will be affected to a degree, Is this too short for this type of conversion? Wondering if I should go for it or abandon the whole thing

Any thoughts appreciated

When your knees hit the handlebars when riding out the saddle?

When the bar hits the steerer tube? Although I’m sure I’ve seen a bar with a dimple out of it for exactly that reason.

Looking at the top tube length on your bike on the BMC website and the top tube length on one of the BMC website and there is 1mm difference (medium).
So if you fit the same length stem as the appropriate size gravel bike you should be OK.
Please check though.

@Bruce I think I get what you mean, will look into gravel bikes with the same length top tube and see what stem they come with

Many thanks

Accepting the handling / steering will be affected to a degree, Is this too short for this type of conversion? Wondering if I should go for it or abandon the whole thing

I have done this before, it was fine

@shermer75 ha ha oh wow! That’s really something!

Guess I should just crack on them ha ha

Sorry that was not clear
The top tube on the gravel bike and your bike look about the same length so you should be OK with a stem the same length as the gravel bike.

@Bruce I’m REALLY sorry, I’m lacking sleep currently but what gravel bike are you speaking of?

If you look at the geometry of your bike on the BMC website.
The look at the geometry of one of the gravel bikes on the BMC website.
It looks to me that the top tube length is only about 1mm different.
So you should be able to use a stem of a similar length to the stem fitted to the gravel bike on the website.

When you turn the bars, the front wheel tucks under and you end up in the bushes.

Long story short, I THOUGHT going from 100mm stem to 70mm stem would do it, turns out, I’d need to be looking at closer to 50mm

Have bought bars, brakes, cables and tape so largely, I’m ready to go, then lining things up before tearing things apart is when I realised, I’m gonna have to buy a new stem too

Accepting the handling / steering will be affected to a degree, Is this too short for this type of conversion? Wondering if I should go for it or abandon the whole thing

No such thing as a stem that’s too short, only bad weight distribution from grip position? You could fit a 0mm or 30mm if you liked. Drop bars have maybe 100mm of reach from stem clamp to hoods/drops grip area anyway. I’ve seen a bike set up with a short reversed stem, the drop bars were still providing a grip position ahead of the steering axis and bikes with grips behind the steering axis work fine.
If you go very short on the stem, slide the saddle forward a bit to balance it out (weight balance, not fit/reach balance. Get the weight bit right first imo)

@jameso Thankyou, some solid advice I feel, re: saddle it’s about as far forward as it’ll comfortably go currently (varying reasons) but I’m on the look out for an inline seat post as opposed to the existing layback I currently have so that should help a bit so thanks for the input

@Bruce I see what you mean now, apologies for being slow

Currently looking at either a 60 or 50mm stem to get me where I need to be, eyeing up some of the decathlon offerings, but will play around a bit more over the weekend before ordering one

Just try the 70mm stem. As long as it’s got a proper face plate it’s simple to swap over. Might be OK or you’ll know if you need shorter and/or the inline post.