Drop Bar MTB Geo

Has anyone done this? How do you figure out your reach? Thinking the addition of the drop bar would mean you would need to size down your frame size? Considering slapping some drop bars on a Chisel or something similar. Wonder how something like that with Race King 2.2s front and rear would compare to something like a Revolt X with 45-50c tires.

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what’s your intended purpose for the bike?
there is a wide spectrum out there in terms of geo for drop bar atb/mtb, examples can be seen here - Complete List of 29” Drop-Bar Mountain Bikes - BIKEPACKING.com

Have you ridden a chisel (for example) on the intended terrain with flat bars? how was it set up?
Aside from reach, the other main factor imo would be seat tube length when sizing down on a modern hardtail frame.

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I also didnt do it but regularly checking this

Interesting conversation. I wonder if there’s a “Best” HT frame to start with for a build like this from a Geometry perspective…

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I’ll just leave this here for you…
I call it my Epic G+… I essentially wanted a Crux(I have one of those too) with clearance for 2.4" tires. I didn’t wan’t MTB geometry. With a bunch of number crunching I knew I could get there. The main requirement was a big change in the fork. I briefly tried the Columbus Adventure fork, but it’s 470mm A-C length still left it feeling very much like a mountain bike. I then was able to source a 450mm A-C rigid fork, still with boost spacing, and really sleek lines that match the frame well. This effectively puts the head tube angle at 70.9 degrees, the seat post itself is at 75.1 degrees(as the seat-tube of the Epic has a kink, and thereby the listed STA isn’t exactly actual). The bottom bracket height is about 5 millimeters higher than the Crux on 45mm tires. Obviously the wheelbase is longer, as is the front center, but overall it’s very much inline with “gravel geometry”. My touch points are really similar to the Crux(54cm w/ -17 x 110mm stem). I definitely sized down versus what I would run with flat bars. This is a Medium frame, and I’m on a Large Epic Evo.
The crazy part is the weight(lighter than my Crux w/ Di2 2x)… 17.9lbs as shown, with a power meter, pedals, cages, Garmin mount…


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The chisel conversion came out great.

Do you have a link to the fork?

It would be interesting to do this with a Chinese Epic Hardtail clone, like Spcycles SP-M05.

Edit: just reread and see you did use epic. I thought it was a chisel.

Have seen that before, was surprised to hear on one of the Bonk Bros podcasts (I think) DJ suggest that the Salsa Cut Throat was terrible (not sure why).
Unlike the bikes on that list I would go for a suspension fork, either a gravel suspension fork or XC suspension fork.
Have looked into Beach Racer bikes some as well, which seem to generally be based on HT XC bikes but with a rigid fork swapped in a 60mm slicks for tires.

Not sure if thats what you are referring to in terms of seat tube but if I did size done, on some bikes, that may leave me unable to run 2 bottles.

As far as purpose, I’m not sure if I would end up using it over my gravel bike for racing, do like the idea of riding out to the single track trails, ripping them and riding back on the road, have done this with both my XC bike and my gravel bike. If it was going to replace one it would have to be a better gravel bike than my gravel bike as it wouldn’t be able to replace a FS XC MTB. With the idea of 47c is faster, drop bar MTB is faster kind of convo though maybe it could replace my gravel bike for racing and be a little more versatile for single track.

It’s just a category or type of bike that interests me, probably more so than getting a full on Trail or Enduro MTB or Fatbike, etc.

I do wonder how much of a gain it would have over something like a Grizl or Revolt X with suspension forks and 47-50c tires.

When DJ finds his drop bar MTB faster, the gravel bike he is comparing to is his Factor Ostro gravel, so a pretty rigid bike from what I understand. I wonder if he tested similarly if a suspension fork gravel bike would also be faster.

Just something I’ve found myself thinking of a lot lately. Think Kerry Werner even slapped some drop bars on his MTB for one of the races recently.

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Yeah, he did it for Chequamegon….it is on one of his videos.

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Some rigid drop bar mtb geometry info here, have to translate the page…

https://servicekoers.cc/strandfietsen/

Just match the top tube to your road bike and then do a shorter stem, thats the way my cuttroar is and its great

The reach on the Chisel is going to be 60-90mm longer than a road or gravel bike, so just run the shortest stem possible. If you’re not going to run a suspension fork, this would likely make the effective reach longer. The pre2020(?) Chisels were about 20mm shorter IIRC

On sizing down an XC frame, you’d be losing space inside the triangle. The Revolt can handle two bottles and a half frame bag easily. On my XL chisel, there was room for. a mini bottle on the seat post and regular bottle on the downtube. If you’re bikepacking, you want to size up

If you’re not going to be running a dropper, for rear compliance, try the Ergon/Canyon leaf spring seat post (in 27.2 with an adapter). I put one of those on my Chisel and it was fantastic. I also tried the PNW Coast and 30.9 leaf spring post - the 27.2 road/gravel post of the way to go.

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Not sure if I can find a XC bike with a effective top tube that short, the effective top tube on my 51cm Cervelo R2 is 531, Chisel Top Tube effective in XS is 555.

Maybe this is something that only works for riders that can fit a large size frame, who can then size down to like a small or something and achieve an appropriate reach when they put the drop bars on.

So I’m in a similar boat. Trying out some corner bars (I need to keep MTB controls as I do race XC with this bike) and holy smokes the reach is LONG.

The bike currently has an 80mm stem. I’m going to give a 35mm stem a try.

This is a fantastic looking build and is similar to what I’ve been contemplating for a long time now. How does this handle compared to the Crux, particularly on chunky descents? I have a gravel bike that has geo more in line with a road bike with a HTA is like 73 which is too sketchy for my lack of handling skills going over chunky rock gardens or roots.

That Epic looks amazing!

Just to throw a bit of a left field thought in here: wouldn’t this be good territory for a custom Ti frame? Could spec it all exactly as desired, and depending on the builder it might only be a ~300g weight penalty over carbon which shouldn’t really matter for the kind of use case these are getting built for.

Probably more expensive than a Chinese replica frame but if you’re looking at the small builders rather than high-end Moots/Reilly type brands then it’s almost certainly cheaper than buying the base model of a fully built carbon hardtail in order to harvest little more than the frame.

Yeah there are a few options like that in the 29" drop bar list in the second post, not many with suspension forks, especially not with 100mm of travel.

At this point I’m starting to think something like a Grizl with suspension fork or Revolt X may be the best way to go even if they can’t handle a 2.2. Maybe there will be more of that type of bike in the next few years.

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I converted my 2016 Scott Scale hardtail to a drop bar rigid bike earlier this year. Concerning the reach, I’m using a Ritchey Comp 60mm -30 degree stem, which puts the centre of the bar 525mm from the tip of the saddle. That measurement is a bit shorter than the same measurement for my road bike (545mm) and a bit longer than what I have on my cyclocross bike (510mm). It feels about right. The saddle to bar drop is 44mm, which is a bit less than for my other two bikes, but the -30 degree stem was the best I could do to get the handlebar reasonably low. I find I spend a bit more time on the drops than for my other two bikes, but that’s fine. The rest of the geometry and angles are unchanged compared with the original Scott Scale MTB build (unloaded non-sagged angles). That makes it slacker than typical gravel bikes, higher BB etc, but nevertheless I really enjoy riding it for gravel and light MTB trails and overall I’m really glad I did the conversion.

It was a fairly cheap conversion overall too, costing about £280 in total. I had the Rival shifters and Ritchey stem already. The Planet X carbon fork was £100, the Ribble carbon bar £39, Rival rear mech £34, new SRAM brake hoses £71, then £30-40 for small miscellaneous things. The bike weighs 8.71 kg (19.20 lb).

My motivation for the conversion was because, like somebody else said, I can’t fit tyres wider than about 50mm in the frame of my cyclocross bike. I much prefer my wider 2.35” MTB tyres for gravel riding and dry cyclocross races. It’s also perfect for a beach race that I do every year. The testing I’ve done indicates that the MTB tyres are faster than the gravel tyres I have (see here and here). I was also finding that, having bought a new full suspension XC MTB in 2022, I just wasn’t using my hardtail much anymore.

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Does this make sense? If I look at horizontal top tube my 21 Norco Search in 50.5 is 530 it has a 90mm stem with a 70mm reach bar from seat post to ramps ~690 (crunching numbers not measuring the actual bike), same measurement on a XS Epic HT is 555, add in a 65mm reach bar and a 70mm stem and I’m at ~690 to ramps. I actually can’t ride a S Epic HT cause the standover is > than my inseam (76cm). Do you think such an aggressive HT angle is necessary (the -30) to get a stack that works?

Could you put a gravel suspension fork on one of these bikes or would none of them have enough clearance? I don’t need 100mm of travel but if I’m throwing on 2.2s I might want a bit. It looks like both the Rock Shox and Fox forks say max of 50mm… Any thoughts on that, is there something out there that falls between a XC and gravel fork?

Regarding the numbers, I’m confident I didn’t make a mistake with the measurements because I checked them again yesterday evening. But that measurement (525mm), from the tip of the saddle to the centre of the bar top, is not a measurement that I see used for a bike’s geometry. But for me it was a convenient dimension to measure and I felt it was the most ergonoimcally-relevant dimension, combing reach, ST angle, saddle layback & stem length. I measured it along the centreline of the bike, but not parallel to the ground. Does that make sense now? Sorry if my explanation isn’t particularly clear. One thing I didn’t check was whether the reach of the drop bars on each of my three bikes was similar, so I’m assuming that dimension isn’t too different, which possibly is a big assumption.

Regarding the handlebar stack, it didn’t really need the minus 30 degree stem. For the first few months I had a -17 degree stem and also a 5mm spacer, so the bar was higher. It still felt okay, but personally I prefer a lower bar and a larger saddle to bar drop, and I now spend more time on the hoods, like on my other drop bar bikes, and less time on the drops.

Concerning the suspension fork, I had exactly the same predicament. I decided to go for a rigid fork in the end, especially because it was in a sale and quite cheap, but I still have my old 100mm suspension fork ready to swap out. It will take less than an hour to swap forks I think, and there are one or two races where the extra speed I can carry with a suspension fork on sections of very rough terrain may be more beneficial than any minor penalties due to small weight increase (+1.1 kg) and extra aero drag. I can see myself leaving the suspension fork on the bike if I do swap forks.

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There is a lot more to it than just comparing the numbers that you are, especially if you are changing the fork length… By shortening the Axle-Crown length, you are increasing lowering the front end, and effectively rotating the entire bike around the rear axle pivot point. This lowers the bottom bracket, steepens both the head tube and seat tube, and also increases the reach, as the bottom bracket doesn’t “rotate” as much as the head tube does, as it isn’t as far away on the tangent. This isn’t a huge deal if you’re talking about 10mm of fork length, but if you’re dropping 30mm(to say a rigid 470mm) you’re probably gaining another 7 or 8mm of reach, as well as lowering the stack and steepening the seat tube and head tube(~20mm per 1 degree).
To start with, you’re listing Effective top tube lengths, which aren’t as transferable as Reach measurements, especially when comparing bikes between genres, as the angles can vary a ton.

Secondly, the standover shouldn’t be an issue on a Small Epic…

And regarding gravel suspension forks, see above for the axle to crown effect on the geometry. A 430mm gravel suspension fork would just put the head tube way too steep(72d on a Small Epic) for most people. The MRP is the longest, at 455ish, but only clears a 2.0", which defeats the whole purpose of converting a mountain bike to gravel bike… This doesn’t even then factor all the hassles with running a Boost rear wheel, and non boost 12x100 front wheel…

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