Custom gravel bike - chainstay length, opinions wanted!

[sparky33]

Originally Posted by dmitrik4

Agreed; 425 vs 430 doesn’t seem worth worrying about, but the 50mm tire clearance vs 45 presents a lot more options.

Get the chain stay length that offers good clearance.

I’ve owned several Firefly’s with varying cs length (420-440). They all had great power transfer and handling. The only regret I ever had was cheating chainstay length a bit short and finding that the largest tire was tight at the seattube.

Their yoke and 1” cstays are all business at any reasonable length.

[KonaSS]

Put me in the camp of get the tire clearance you need, and ask Firefly to do their job in making sure the bike rides how you want.

[John H.]

5mm (in isolation) will not be a negative- But what is the design of the rest of the bike? Head angle, bb drop, front center?
Point being, if the bike is designed to be road bike-ish and snappy- Going all the way to 50mm tires may not handle great.

Some folks try to stuff to many feature and variables into a custom bike. Because you can, doesn't always mean you should.

[solographik]

Originally Posted by John H.

5mm (in isolation) will not be a negative- But what is the design of the rest of the bike? Head angle, bb drop, front center?
Point being, if the bike is designed to be road bike-ish and snappy- Going all the way to 50mm tires may not handle great.

Some folks try to stuff to many feature and variables into a custom bike. Because you can, doesn't always mean you should.

Makes sense. The design is meant to lean more towards riding off than on tarmac.

HT: 70.8
BB Drop: 75mm
Front center: 617mm

Thank you everyone else for chiming in, does seem like i'll appreciate the clearance a bit more!

[nmrt]

This is a great point by John H.
5 mm is not a lot. But how do you want the bike to ride? A 430 mm CS and an accompanying high trail in the mid 60s will make the bike NOT ride like a zippy road bike if road-bike-handling is what you are after.

But if you're after a "traditional" gravel bike a 430 mm CS is okay. For me, anything more than a 430 mm CS, and it turns like a "semi truck.".

Originally Posted by John H.

5mm (in isolation) will not be a negative- But what is the design of the rest of the bike? Head angle, bb drop, front center?
Point being, if the bike is designed to be road bike-ish and snappy- Going all the way to 50mm tires may not handle great.

Some folks try to stuff to many feature and variables into a custom bike. Because you can, doesn't always mean you should.

[.RJ]

Originally Posted by solographik

Will the rear end be noticeably more sluggish with a 5mm longer chainstay? My initial thought was that the increased tire clearance would open up a lot more options for tires (in the 47-48mm range) that would help keeps more plush on longer rides, though I don't expect to run things bigger than a 42-45mm normally.

I guess that depends on what you're gonna do with it. If you plan on doing long rides while loaded, some extra chainstay and tire would really help there. If you're never going to do that, I'd opt for shorter, even shorter than 425 if they can swing it. And, what are you doing with the front of the bike? Long and low (go longer), or short and snappy like a CX bike (go shorter)?

45's are great, so does going to 50mm really open up more options that arent available in 45mm? I dont think things really change until you start getting into 55mm which makes fast rolling XC mtb tires an option.

[mstateglfr]

I have 430mm chainstays on my gravel bike and have yet to come upon a time where I raised my fist in the air and cursed the gods for not giving me 425mm chainstays.

72.5deg hta, 50mm fork offset, 44mm actual width tires = 60mm trail. <--- just other geometry that might allow that 'mutumbo-esque' 430mm chainstay design to still make the bike feel fun.

[vespasianus]

Originally Posted by mstateglfr

I have 430mm chainstays on my gravel bike and have yet to come upon a time where I raised my fist in the air and cursed the gods for not giving me 425mm chainstays.

72.5deg hta, 50mm fork offset, 44mm actual width tires = 60mm trail. <--- just other geometry that might allow that 'mutumbo-esque' 430mm chainstay design to still make the bike feel fun.

Agree 100%. My belief is that the feeling of a lively and agile bike comes from the head angle and overall wheelbase - as opposed to just the CS length.

[wallymann]

IME 42.5 is more allroad/cross biased...43.0 and up is more gravely/adventury.

my gravel riding is more road-biased:
- gravel bike #1 had 42.5 stays, which i loved
- gravel bike #2 has 43.5 stays and its OK
- would rather the shorter #1 stay length for the snappier handling for my riding

+10mm CS there is a difference in handling. +5mm maybe less noticeable.

Originally Posted by solographik

Hey - looking for some collective wisdom from the PL folks.

My turn in the firefly queue is coming up soon, and we're finalizing the geometry. The bike is meant to be a nimble gravel/adventure bike -- something that won't feel out of place at a cross race but still comfortable enough to take on longer multi-day off road adventures.

The default spec is a 425mm chainstay w/ 45mm of measured tire clearance (700c). I have the option of a 430mm chainstay to increase the measured tire clearance to 50mm.

Will the rear end be noticeably more sluggish with a 5mm longer chainstay? My initial thought was that the increased tire clearance would open up a lot more options for tires (in the 47-48mm range) that would help keeps more plush on longer rides, though I don't expect to run things bigger than a 42-45mm normally.

I know that I'm really splitting hairs at this point but just wanted a bit of help putting my mind at ease. Thank you!

[Pinned]

Have you asked Firefly their thoughts on this from a handling perspective? It's not hard to make a bike with 430mm chainstays feel snappy - they'll be able to build what you want.

Personally, I have no interest in bikes with super short rear ends - but there is also someone here looking to do things like offset seat tubes and such to shorten the chainstays. These are all opinions but none of them are truly valuable to your pursuit. Firefly will surely alter things to suit - such as the BB drop, front center length, STA, etc so your weight balance and the bike's handling are aligned for your riding regardless of the CS length you're choosing. 5mm is not a huge difference in CS length considering it is unlikely to be altered without other considerations.

[boomforeal]

I can’t imagine buying a production bike without knowing what geometry I wanted. Going into a custom Ti build with such questions unanswered seems unwise. No amount of hmming or online advice will answer this question effectively. You’re just as likely to get lucky as you are to be unsatisfied with your choice. Or suffer from fomo on the path not taken: “it rides great, but I can’t help but wonder if I’d like it even more with…”. You might consider dropping back in the queue a few spots and demoing some bikes to get a better sense of what you want.

[benisfroms]

The difference of 5mm in chainstay length is subtle and whether it will be “noticeably more sluggish” can depend on several factors, including the type of terrain you’re riding on and your personal riding style. Civil 3D 2023 subscription discount. For most riders, the difference in handling is minimal, but the increased tire clearance could indeed offer more versatility for tire choices and potentially more comfort for long rides.

[kingpin75s]

When it comes to CS length, I only have strong opinions and a limited range of what is acceptable, when it comes to mountain bikes and tight single track. Since that is not generally a consideration for gravel, it comes down to personal preference.

Get what you need to clear the tire you want to run and from there its whether you want more stability/cush or more agility/snap in the rear. There is no right answer, only the right answer for your own preferences.