Fast custom gravel bike for flat terrain: geometry, fork and groupset choice

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nulldreiundreissig
Posts: 120
Joined: Tue Oct 02, 2018 11:13 am

by nulldreiundreissig

Folks,

For some while now I have pondered the idea of getting a gravel bike from a Zurich based frame builder before I move to another city in spring.
Unfortunately I have not spent a lot of time on gravel bikes before, so I'm a bit clueless in terms of geometry and what to look for. Given what I like about my SL6 on the road and the little bit of experience on gravel bikes that I have, I'd love to something that is on the fun and nimble side of geometries that is also fun when used on the road.
The terrain will be mostly flat-ish paths through the woods, along the rivers and unpaved gravel roads. No single tracks, rather fast terrain. Based on that, I feel like something in between a 33mm cross tire and 35mm TL-tires should be enough, with a tendency towards big tires that also feel nice on the road. There are no plans for playing around with 650B wheels and no need for more than a 1:1 gear ratio.

In terms of geometry I'm completely clueless, but I have identified three different kinds of geometries that might serve the purpose:
1. Gravel race stuff like the aspero with a lot of BB drop, road-ish positions and optional 650B
2. Classic cross geometries with very high bbs, focus on 33-38mm tires. The canyon inflite's geometry looks quite interesting and quite road-bike-ish with it's 72 degree head tube angle.
3. something like the new spesh crux, that is somewhere in between.
The Crux gets of praise from press and also here at WW, so it seems kind of the logical choice to take some inspiration from it. So does the new Super X from Cannondale. But I'd love to hear your opinions on and suggestions for the right bike for Munich.

The second topic would be the right choice of an aftermarket fork. My frame builder has suggested to choose on of the forks from Columbus, but we are open to suggestions. Enve does have a fork for up to 32mm and one that goes up to 50mm, but I'd be interested in other suggestions.

Groupset-wise I'm thinking about Ekar, but given the reviews are mixed, the scarcity of N3W-compatible wheel set and the lack of power meter options, I'm thinking about a GRX-Udi2-XTR-mix with my trusty old P2M NGeco as seen on the bikes of some gravel pros. Campi Record or Chorus would be lovely other options, but camping PMs again are scarce and expensive.

What do you think?

DrimeOser
Posts: 19
Joined: Wed Sep 01, 2021 1:35 pm

by DrimeOser

For Minga: Hol dir das SuperX!

For convenience of the non-German speaking audience: get the SuperX! I am in Munich and for around here, that bike is perfect. I have build it up as a 1-by gravel bike and the 40 to 42 gearing is good for everything you can find in a day's ride from your doorstep. Bike is super fast and fun to ride. The Save flex points in frame and fork really work for getting you less beat up than other bikes would do.

Yes, you have to hassle a bit with the Ai rear end and you have to run Hollowgram cranks, that are pretty sweet though.

A freind recently built up a Crux with Ekar and that thing is a rocket ship too.

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Marin
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by Marin

Copy the Crux geo

DrimeOser
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by DrimeOser

Sorry, my writeup was more geared towards the bikes rather than the geo. Nevertheless, I feel that the geo of the SuperX is outstanding in being quick handling and providing good stability down hill. Just, to achieve this, Cannondale uses a combo of parameters they call 'out front geo'. That pushes the front whell further out with a head angle of 71 and a longer fork offset. To get that fork offset in an aftermarket fork is not possible, I believe. There are CaadX/SuperX forks floating around on Ebay etc. though. These forks nevertheless have a quite huge crown that might not work out to be well integrated into a steel frame.

The new Crux has a fairly common modern road geo. My friend has a SL6 and a Crux and geo wise they much alike.

CarlosFerreiro
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by CarlosFerreiro

The Cannondale fork is a 1 1/2" to 1 1/8" taper. You could probably go with a suitable 1 1/2" external bottom headset cup for a steel custom build?
Although I love my SuperX, I think in the same circumstances I would maybe chose the Crux as a starting point too.

DrimeOser
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by DrimeOser

From what I could see, the Crux is an outstanding bike in many aspects. But the geometry is not that exceptional. It is good but not what defines that bike. The carbon structure is a work of art, not to speak of the weight. Also, it seems to have a wonderful ability to absorb the forces going into the frame's structure.

If you were to copy the geo of the Open UP, the Aspero, 3T Exploro, you will alsohave a very good gravel ride. The SuperX has a special flavour in the geo department. If you like it, that is great, if not, then better go conventional geo. There are literally a thousand interpretations of gravel geos out there, but most of the bikes marketet under the flag of race gravel are pretty similar. Right now, cockpit integration and aero are the buzzwords in that category right now.

CustomMetal
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by CustomMetal

The Columbus futura tests as pretty aero... happy with mine ok my saffron which I use for the same type of thing as you are talking about
Perdita- Burls Ti 8kg
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nickf
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by nickf

I went full road bike geometry with my latest build. Room to fit 40c tires. If I need more I'll bring the mountain bike. Used an Open u-turn fork, great weight. So far so good the bike rides and handles as expected. The biggest difference in feel was slightly shorter stays and less trail.

Image

nulldreiundreissig
Posts: 120
Joined: Tue Oct 02, 2018 11:13 am

by nulldreiundreissig

Thank you very much for the input, guys! Besised the gravel bike, I will retain riding and racing on my Tarmac, that is set up long, low and with 38cm bars. Compliance however, won't be the main criterium for the new bike. Sitting at 62kg and being used happy with 25mm tires on the road, i hardly ever felt uncomfortable, even when riding for 8 hours and more. What I want is something that as a reactive, fun geometry, that feels very road-bike ish, capeable. That's what I refer to as fast.
DrimeOser wrote:
Sun Nov 28, 2021 2:13 pm
Sorry, my writeup was more geared towards the bikes rather than the geo. Nevertheless, I feel that the geo of the SuperX is outstanding in being quick handling and providing good stability down hill. Just, to achieve this, Cannondale uses a combo of parameters they call 'out front geo'. That pushes the front whell further out with a head angle of 71 and a longer fork offset. To get that fork offset in an aftermarket fork is not possible, I believe. There are CaadX/SuperX forks floating around on Ebay etc. though. These forks nevertheless have a quite huge crown that might not work out to be well integrated into a steel frame.

The new Crux has a fairly common modern road geo. My friend has a SL6 and a Crux and geo wise they much alike.
CarlosFerreiro wrote:
Sun Nov 28, 2021 7:19 pm
The Cannondale fork is a 1 1/2" to 1 1/8" taper. You could probably go with a suitable 1 1/2" external bottom headset cup for a steel custom build?
Although I love my SuperX, I think in the same circumstances I would maybe chose the Crux as a starting point too.
Thank you. That's a very useful remark. I'm riding and racing on an SL6 that I really love. Changing from one bike to the other will always take some time to adapt, but I guess it makes sense to keep this in mind and minimize. Looking at bikes in size 54 or S, the both the crux and superx seem to be a bit slacker in comparison to to the caynon and my SL6
Image
CustomMetal wrote:
Sun Nov 28, 2021 9:24 pm
The Columbus futura tests as pretty aero... happy with mine ok my saffron which I use for the same type of thing as you are talking about
Yes they look great, but 50mm tire clearance seems huge for the gravel / CX Fork. Does it make sense to look for an all-road fork that clears something around 35mm or would you choose a dedicated gravel / CX fork?

CustomMetal
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by CustomMetal

The Columbus has clearance for 40mm not 50mm
Perdita- Burls Ti 8kg
Aurelia- Saffron Stainless 9kg
Bertha- Trek SC
Verity- Sturdy Ti Aero (incoming)
Serenity- Sturdy Ti Gravel (incoming)
Allegra- Sturdy Steel Lugged (incoming)
Jolene- Tifosi Alu 8kg
Alya- Tifosi Mons
Wilda- Spoon Vars Disc (incoming)

nulldreiundreissig
Posts: 120
Joined: Tue Oct 02, 2018 11:13 am

by nulldreiundreissig

nickf wrote:
Mon Nov 29, 2021 2:37 pm
I went full road bike geometry with my latest build. Room to fit 40c tires. If I need more I'll bring the mountain bike. Used an Open u-turn fork, great weight. So far so good the bike rides and handles as expected. The biggest difference in feel was slightly shorter stays and less trail.

Image
Oh that's fascinating. May I ask you for a picture of the bike and more details about the build and what drove you towards the geometry and the Fork from Open?

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nickf
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by nickf

A couple reasons why I went this way for the build. I travel a lot for work and bring the gravel bike with me setup with road tires. Also after participating in more competitive races I wanted something with a little sharper steering. I don't need a bike with a ton of stability and strange geometry to fit 50c tires. Many of our gravel events have a good amount of road sections where we do a lot of fast panceline work and can appreciate the road bike feel. I have worked with Rob English before and explained to him what I was after. What I ended up with was essentially a road bike with room for a 40c tire. The open u-turn was perfect, lightweight at 348g painted, built in crown race, nice shape to go with smaller steel tubes, room for 40c, not as wide as massive looking as other gravel forks.

DHG01
Posts: 484
Joined: Thu Sep 24, 2020 7:14 pm
Location: Madrid

by DHG01

DrimeOser wrote:
Sun Nov 28, 2021 8:03 am
For Minga: Hol dir das SuperX!

For convenience of the non-German speaking audience: get the SuperX! I am in Munich and for around here, that bike is perfect. I have build it up as a 1-by gravel bike and the 40 to 42 gearing is good for everything you can find in a day's ride from your doorstep. Bike is super fast and fun to ride. The Save flex points in frame and fork really work for getting you less beat up than other bikes would do.

Yes, you have to hassle a bit with the Ai rear end and you have to run Hollowgram cranks, that are pretty sweet though.

A freind recently built up a Crux with Ekar and that thing is a rocket ship too.

I really like Cannondale (SuperSix is probably my best ride) and was about to pull the trigger on a SuperX a few years; the only to warn about this bike is the need to re dish rear wheel.

DHG01
Posts: 484
Joined: Thu Sep 24, 2020 7:14 pm
Location: Madrid

by DHG01

From what I am reading, a think a road geo would suit you fine - you want to do fast riding on paths.

One of my gravels is a CX01, which has the same geometry as the SLR. Great ride, fast and responsive. It is not meant to do mountain biking with gravel, but for fast riding on unpaved roads. I typically ride it with 33/36 mm. So that relates to one thing I would tweak on a custom geometry - lowering the ciclo cross bottom bracket (and more so with the larger than road tyres). Challenge then is how short can you get your chain stays that allow required tyre clearance.

I don't think the Aspero geo, with longer top tube and shorter stem, suits much of a purpose for these types of ride.

If I had the certainty of 36 mm clearance, I think the Aetheos would make a pretty cool fast gravel.
I d say have a peek into cyclocross geo but bearing in mind the bb is higher than you need.

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wheelsONfire
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by wheelsONfire

I would pick the Open U-turn fork for a gravel bike. I don't know why you dismiss 650B wheels and tires, it's superb for gravel.
I would go so far and ask for a fork with 10-15mm of supension, i think it would be sufficient. I have a Lauf fork with 30mm of travel, it's good for some trails, but it has it's drawbacks and i know some people don't like it. Anyway, it's better if you have more tire clearance than a lack of.
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Ax Lightness Vial EVO Race (2018.12.21)
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Paduano Racing Fidia (kind of shelved)
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