Chainstay length, does is effect balance point and saddle setback from one frame to the next?

[gSporco]

As I continue my endless journey into cycling tech-nerdery... geometry has been on my mind a lot as I am build my soon to be dedicated road bike.

My current bike "Aspero" size 51cm is dialed in after many many miles of use. It is setup more agressive than most gravel bikes as this is my only bike with multiple wheelsets.

I recently found that getting my saddle further back puts me in a better, more comfortable position. Less weight on the hands and flatter back, also feel my pedal strokes are smoother.

Ok on to the question:
Given 2 bike frames with identical geometry "except " chainstay length, would the saddle set back be identical on both bikes over the BB if bike 1 has 420mm chainstay and bike 2 has 410mm chainstay?

My Aspero has 420mm Chainstay, tip of saddle is 49mm behind BB center.

If I set this saddle position on the same bike with 410mm chainstay will my balance point be further back from bike 1, because the rear wheel is closer?

Ok WW's lets hear it

[ghostinthemachine]

Balance point is based on your body and it's position around stack and reach (plus bars stem etc). So no.

[Karvalo]

If the setback works for you in pedalling and position then keep it. Being closer to the back wheel might contribute to it handling slightly differently - but it's a different bike so it's going to handle differently anyway.

And even if the 'balance point' matters that much you can't discern it from chainstay length alone. Wanna bet that the bike with shorter chainstays also has a shorter front centre?

[gSporco]

I find it hard to believe that chainstay lenth doesn't effect balance point. Shorter brings the wheel closer to the rider.

If you want to do a wheelie you shift your weight back right? Therefore balance point is closer to the rear wheel.

Given 2 frames with identical stack and reach but the new bike has 10mm shorter chainstay wouldnt my weight be supported by the back wheel more on the shorter chainstay frame?

I ask because frame #2 is the road frame Inwant to build next and would like to know if my saddle tip to BB should be the same on the shorter chainstay bike with all other attributes being equal.

[Mr.Gib]

I find it hard to believe that chainstay lenth doesn't effect balance point. Shorter brings the wheel closer to the rider.

Believe it. Different length chainstays will change the percentage of weight on the rear vs front wheel, but your ass won't know the difference. Assuming you have established the optimum relationship between hip joint and bottom bracket, than that is your position regardless of the bike. Now you could argue that you need to move the saddle fore or aft to compensate for some handling problem caused by extreme odd weight distribution, but 5 or 10mm one way or the other on the chain stay is not going to send you careening off the road if you keep your optimal saddle location.

[TobinHatesYou]

Rear-center and front-center obviously affect where your center of mass will sit between the wheels, but it won’t affect the how much weight you support with your hands if your saddle and bar position hasn’t changed. So no, you shouldn’t change your saddle position to compensate for differences between otherwise similar road bikes.

[gSporco]

Rear-center and front-center obviously affect where your center of mass will sit between the wheels, but it won’t affect the how much weight you support with your hands if your saddle and bar position hasn’t changed. So no, you shouldn’t change your saddle position to compensate for differences between otherwise similar road bikes.

Thank you for that. I was thinking I would need to start my saddle position 10mm forward on the new frame to compensate for the 10mm less chainstay to achieve the same weight on the hoods and 10mm more stem length to maintain the same reach I like.

[Karvalo]

I find it hard to believe that chainstay lenth doesn't effect balance point. Shorter brings the wheel closer to the rider.

If you want to do a wheelie you shift your weight back right? Therefore balance point is closer to the rear wheel.

And if you want to do an endo you shift your weight forward and pull the front brake. So what? Do you want to wheelie or endo? Are you accidentally wheelieing or endoing? If not, what's the relevance?

Given 2 frames with identical stack and reach but the new bike has 10mm shorter chainstay wouldnt my weight be supported by the back wheel more on the shorter chainstay frame?

So, what do you mean by balance point? I was assuming you meant handling because at least that's a thing. If you mean whether it changes your feel on the saddle / bars then no. The chainstays could be 4000mm long and it would make no difference.

[jmfreeman535]

Thank you for that. I was thinking I would need to start my saddle position 10mm forward on the new frame to compensate for the 10mm less chainstay to achieve the same weight on the hoods and 10mm more stem length to maintain the same reach I like.

As Tobin stated, do not change your saddle position (or any of the contact points for that matter) to compensate for differences in geometry. The contact points, and the weight balance amongst them, (i.e pressure on hands/saddle) is controlled by the BB and their relastionship in space too them. Changes to dimensions like chainstay, TT, seat/headtube angle will not effect this.

They do, however, have an effect on the way that the bike handles/reacts, and how stable it feels, due to the shift in the front/rear weight distribution. But, bike designers usally offset these changes in order to keep the bike well balanced...i.e. a bike with longer chainstays usually will have a longer TT and/or slacker HT angle.

Yes, it will still feel differently when compared to an all-out road race bike, but the actual balance of the bike will remain, more or less, the same. I have an R5 and an Aspero and I run the exact same fit on both of them. They feel very different, but both are well balanced.

[gSporco]

I find it hard to believe that chainstay lenth doesn't effect balance point. Shorter brings the wheel closer to the rider.

If you want to do a wheelie you shift your weight back right? Therefore balance point is closer to the rear wheel.

And if you want to do an endo you shift your weight forward and pull the front brake. So what? Do you want to wheelie or endo? Are you accidentally wheelieing or endoing? If not, what's the relevance?

Given 2 frames with identical stack and reach but the new bike has 10mm shorter chainstay wouldnt my weight be supported by the back wheel more on the shorter chainstay frame?

So, what do you mean by balance point? I was assuming you meant handling because at least that's a thing. If you mean whether it changes your feel on the saddle / bars then no. The chainstays could be 4000mm long and it would make no difference.

Must be a language barrier between us, or I am just not being crystal clear with you lol...

I am talking about balance point in relation to my hands on the bars. Wheeling was a reference to explain "my" view on balance point... I was assuming the bikes balance point effects "my" balance point on the bike as it relates to the weight on my hands in my preferred position.

As others, who understood what I was asking, already cleared this point up for me, and thank you to those who contributed..

So now I understand, chainstay, wheelbase etc... doesn't necessarily matter when it comes tonthe rider balancing their weight on the bike. It has more to do with seat position in relation to the bottom bracket.

Again, I dont care about how the bike handles, or if it wheelies etc... that was not my question...

[Alexbn921]

Chain stay length has zero effect on your body position.
I ride a 61 and have gone down the geometry rabbit hole.
It will effect the weight balance of the bike front to rear. This can effect handling and if handling is your primary goal then compromising your position slightly can help.

[wheelsONfire]

As I continue my endless journey into cycling tech-nerdery... geometry has been on my mind a lot as I am build my soon to be dedicated road bike.

My current bike "Aspero" size 51cm is dialed in after many many miles of use. It is setup more agressive than most gravel bikes as this is my only bike with multiple wheelsets.

I recently found that getting my saddle further back puts me in a better, more comfortable position. Less weight on the hands and flatter back, also feel my pedal strokes are smoother.

Ok on to the question:
Given 2 bike frames with identical geometry "except " chainstay length, would the saddle set back be identical on both bikes over the BB if bike 1 has 420mm chainstay and bike 2 has 410mm chainstay?

My Aspero has 420mm Chainstay, tip of saddle is 49mm behind BB center.

If I set this saddle position on the same bike with 410mm chainstay will my balance point be further back from bike 1, because the rear wheel is closer?

Ok WW's lets hear it

No change needed, but that isn't why i write in your thread!
I am curious on what road bike you're going for ?

[gSporco]

No change needed, but that isn't why i write in your thread!
I am curious on what road bike you're going for ?

Lol.. well I didn't want to say anything because Inwas on the fence on building it or not

But its an SWorks Aethos in beautiful Jet Fuel ( you can see all the carbon layup in the light)

Besides the head angle and chainstay length it's nearly identical stack and reach as my Aspero

Im on the fence because I secretly want the new R5 in flat black and white logo (if that will even be an option); or an S5 in that same color. But I am crazy!

[wheelsONfire]

No change needed, but that isn't why i write in your thread!
I am curious on what road bike you're going for ?

Lol.. well I didn't want to say anything because Inwas on the fence on building it or not

But its an SWorks Aethos in beautiful Jet Fuel ( you can see all the carbon layup in the light)

Besides the head angle and chainstay length it's nearly identical stack and reach as my Aspero

Im on the fence because I secretly want the new R5 in flat black and white logo (if that will even be an option); or an S5 in that same color. But I am crazy!

Aethos... you can't really mean it's close to Aspero in geometry?
Specialized IMO went nuts with the geo on this model. It's not aimed at racers, still it's very long in reach.
395mm in size 56!
Well, i guess it might have it's appeal due to it's lightness!?
Personally i don't like the design at all. Are you thinking of the all new R5 with no release date?
S5D is surely a cool bike. Might be the only aero bike i actually would buy if i ever bought any.
Otherwise i would go for Factor Vam 02 over Aethos, but that's just me
It's sure great fun building a new bike, i hope you pick the one you like most

[gSporco]

No change needed, but that isn't why i write in your thread!
I am curious on what road bike you're going for ?

Lol.. well I didn't want to say anything because Inwas on the fence on building it or not

But its an SWorks Aethos in beautiful Jet Fuel ( you can see all the carbon layup in the light)

Besides the head angle and chainstay length it's nearly identical stack and reach as my Aspero

Im on the fence because I secretly want the new R5 in flat black and white logo (if that will even be an option); or an S5 in that same color. But I am crazy!

Aethos... you can't really mean it's close to Aspero in geometry?
Specialized IMO went nuts with the geo on this model. It's not aimed at racers, still it's very long in reach.
395mm in size 56!
Well, i guess it might have it's appeal due to it's lightness!?
Personally i don't like the design at all. Are you thinking of the all new R5 with no release date?
S5D is surely a cool bike. Might be the only aero bike i actually would buy if i ever bought any.
Otherwise i would go for Factor Vam 02 over Aethos, but that's just me
It's sure great fun building a new bike, i hope you pick the one you like most

Its definitely not everyones cup of tea and I am not sure its mine either. Was able to get it for a steel, so I figured what the heck, can always sell and not lose my money.
Size 51 Aspero 530 stack 379 reach
size 52 Aethos 527 stack 380 reach
Head angle is 1 degree steeper and the chain stays are 10mm shorter.

Yes the new unreleased R5, but ill take the current R5 as well in matte black. The S5d is very appealing to me, but I don't race, and mostly climb where I live... so my 16mph average speed rides will be pretty pathetic on an S5D. But who am I kidding, 16mph average is pathetic for me no matter what lol