AASQ #143: Gravel Bike Geo – How dealing with pertains to wheelbase, stem size and fork offset

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We all know, there’s no such factor as a silly query. However there are some questions you won’t wish to ask your native store or driving buddies. AASQ is our weekly collection the place we unravel your questions – critical or in any other case. Hit the hyperlink on the backside of the put up to submit your personal query.

Welcome again to the Bikerumor Ask A Silly Query collection. This week, we’re tacking gravel bike geometry, and the way wheelbase, stem size, and fork offset contribute to dealing with properties like stability and agility. Becoming a member of us this week are the next specialists:

Would a Gravel Bike with a brief wheelbase, low path however lengthy stem behave equally to a motorcycle with an extended wheelbase, excessive path, and quick stem? Does the size of the wheelbase and/or path have the identical affect on stability because the size of the stem? If not, which is extra vital for stability and the way would I really feel this distinction throughout a experience? 

Marin Bikes: In our expertise, an extended wheelbase is at all times going to really feel extra steady than a shorter wheelbase, however head tube angle and stem size will nonetheless very a lot have an effect on the steering really feel. The 2 circumstances given (quick wheelbase, low path, lengthy stem vs. lengthy wheelbase, excessive path, quick stem) are precisely the variations between what we used to see on MTBs all the best way to the 2010s, and what we’re seeing on MTBs now.

2020 Marin gravel and all-road commuter bikes, carbon alloy steel

Marin spec a 60mm stem on the dimensions 56 Headlands Gravel Bike; 420mm stays, a 386.4mm attain, 71.5° HA with a 50mm fork offset offers a 1028.5mm wheelbase

The advantages of the trendy geometry are plain with dealing with, consolation, and security on the bike at most speeds in most circumstances, and this is similar on a gravel bike, albeit with much less “excessive” geometry numbers than what’s being pushed within the Enduro MTB class.

marin headlands

From Dimension 58 upwards, Marin improve bar width to 440mm and improve stem size to 70mm

To summarize the sensation of the bike with an extended wheelbase, extra slack head tube, and shorter stem (ideally with a wider handlebar too!), there’s a much less twitchy, extra planted really feel to the entrance finish. The bike remains to be straightforward to steer, however the feeling that the entrance finish would require a lot effort and focus to maintain pointed within the desired path is pushed apart and permits the rider to focus extra on what’s coming additional down the trail. That predictability means the rider can experience sooner and nonetheless have the sensation of getting extra time to react to obstacles, and likewise really feel extra snug retaining the bike within the desired path after they’re drained.

Ritchey: In reply to your query, “Would a Gravel Bike with a brief wheelbase, low path however lengthy stem behave equally to a motorcycle with an extended wheelbase, excessive path, and quick stem?”, our reply is… These are two issues that don’t actually have something to do with one another. So, no, these two bikes wouldn’t behave the identical. The experience traits of longer chainstays can’t be replicated with an extended stem or perhaps a low path. 

ritchey swiss cross

The Ritchey Swiss Cross has been of their lineup for over 25 years, first raced by multi-time Swiss CX & World MTB champ Thomas Frischknecht in 1994

The primary appears like a cross bike. Most drop bar bikes with shorter wheelbases (just like the Ritchey Highway Logic and Swiss Cross) are designed with an optimum vary of stem size in thoughts, often 90-110mm. These bikes are supposed to be agile and fast dealing with in tight, race-like eventualities, whereas gravel and off-road particular bikes, just like the Ritchey Outback and Ascent are designed for a shorter stem, often 70-90mm, and are meant for lengthy, easy journey over tough surfaces. Stem size and path should do with dealing with greater than the experience high quality of an extended chainstay.

ritchey outback gravel adventure bike steel

The Ritchey Outback Gravel Bike runs a 50mm offset fork at a 71° HA in Dimension Massive; on 700c wheels there may be adequate clearance for 48mm huge tires

In reply to your query, “Does the size of the wheelbase and/or path have the identical affect on stability because the size of the stem?”, once more, the reply is, No. The steadiness that comes with longer chainstays is constructed into the DNA of the body. The best way it feels going into, and popping out of, a flip could be totally different. An extended stem would decelerate the response of the entrance of the bike, sure, however the best way the entire bike stays steady in straight strains and in turns is outlined by its wheelbase and chainstay size.

Which is extra vital for stability and the way would I really feel this distinction throughout a experience? Properly, a motorcycle is extra steady and dependable due to its built-in geometry. An extended or shorter stem will definitely dial in a match, thereby including some stability, however an extended stem isn’t any match for a well-designed body. There are parts of the bike which are individualized, corresponding to stem size, path, chainstay size, seat tube angle, and so forth. which are vital to think about…but it surely’s most vital to think about all of this as an entire.

ritchey swiss cross racing

This all makes the bike full – how and what it was designed for and with what elements that inform the experience high quality. It’s foolish to say solely the chainstay makes a distinction with the dealing with when it’s inherently tied into the path of the entrance finish, the size of the top tube, the size of the highest tube, and even the selection of tires. That is why after we take a look at warranties, we wish to see the entire bike and the way it was used as a result of that informs how one thing failed. Consider a bicycle as a spider net: you can not tug on one string and never shake your entire construction.

Scott: In reply to your query, “Would a Gravel Bike with a brief wheelbase, low path however lengthy stem behave equally to a motorcycle with an extended wheelbase, excessive path, and quick stem?”, my reply is, No. That is as a result of the wheelbase and path affect the agility and steering traits of the bike whereas the stem size (and bar width) affect the interpretation of the rider’s enter to the rotation of the entrance wheel.

2022 Scott Addict Gravel aero integrated carbon gravel bike_Tuned.jpgdescending

The 2022 Scott Addict Carbon Gavel Bike will get a 71° HA in Dimension Massive, spec’d with a 103mm handlebar-integrated stem

In case you translate this to vehicles it’d grow to be extra apparent: An extended wheelbase and a small steering angle of the entrance wheels ends in a really excessive turning radius of the automobile. That is the attribute of the chassis that you could’t compensate for by merely rising the transmission ratio of your steering gearbox.

2022 Scott Addict Gravel aero integrated carbon gravel bike, integrated Syncros X gravel bar

A body geometry with an extended path and an extended wheelbase will lead to a fairly sluggishly dealing with body. Combining this with a shorter stem will solely lead to a harder-to-steer bike. Because the leverage between the rider’s arms and the steering axis decreases, one wants to supply a a lot greater drive to show the bar.

In reply to the query, Does the size of the wheelbase and/or path have the identical affect on stability because the size of the stem?”, once more, my reply is, No. That is as a result of the wheelbase and path affect the agility/stability of the bike’s chassis whereas the size of the stem influences the leverage of the rider’s steering actions and so it acts as a transmission.

Think about driving a motorcycle with no arms simply by leaning your physique weight within the path you wish to go. A too steady body geometry with an extended wheelbase and path can be more durable to steer round corners whereas a geometry with a brief wheelbase and quick path can be nervous and troublesome to experience in a straight line. The stem size has nearly zero affect on the steering traits as soon as you’re taking your arms off the bar.

custom Scott Addict Gravel Tuned Dangerholm edition lightweight carbon prototype gravel bike project, complete

The Dangerholm version of the Scott Addict Gravel Bike weighs 7.13kg, together with pedals, a full 1kg lighter than Scott’s lightest 8700€ full Tuned construct with out pedals

Lastly, in reply to the ultimate query, “Which is extra vital for stability and the way would I really feel this distinction throughout a experience?”, I might counsel the next.

The body geometry is essentially the most essential issue for the soundness of a motorcycle. You’ll really feel this throughout your experience whenever you take your arms off the bar or whenever you experience in squally crosswinds and at greater speeds. On a motorcycle with excessive directional stability, will probably be simpler to carry a straight line.

However, this stability involves the detriment of agility. If a motorcycle is just too steady it’s going to really feel sluggish and onerous to lean into corners. Excessive-speed switchbacks or tight roundabouts could also be difficult in addition to fast directional adjustments. So, selecting the best geometry for a motorcycle is at all times a trade-off between agility and stability.

Acquired a query of your personal? Click on right here to make use of the Ask A Silly Query kind to submit questions on any cycling-related subject of your alternative, and we’ll get the specialists to reply them for you!

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