To those who paid attention during maths...

[moorey]

This. There's not enough information in your formula to be able to tell you, it depends how high off the ground your head tube is. The higher off the ground the more the increase in your wheelbase.

If your head tube is 3m off the ground (300 in the picture) the increase is roughly 4cm.

View attachment 338772

So, being under 1m, maybe around a cm?

 

[schred]

What's happening to reach?

 

[The Duckmeister]

I am indeed. I'm trying desperately to convince myself that my bikes aren't too small for me. The reach is too short, but I'm hoping that the extended wheelbase will make up for that a little bit.

How do you figure that? Reach is a result of main frame geometry; tweaking the end attachments will do the grand total of fuck-all to the main frame geometry.

 

[TonyMax]

So, being under 1m, maybe around a cm?

1.3cm at 1m off the ground.

 

[Nautonier]

How do you figure that? Reach is a result of main frame geometry; tweaking the end attachments will do the grand total of fuck-all to the main frame geometry.

I know the reach will remain exactly the same, but increasing the wheelbase might make the bike feel slightly more stable in certain situations. I really don't know if was the increased wheelbase or the increased reach that I liked on the Sanction, but it seemed to fit me better than my current bike.

 

[Nautonier]

1.3cm at 1m off the ground.

13mm seems like more than I would expect for a .6 degree change. I hope this is right - the longer the better.

 

[linkl8r]

Riser bars ≈30mm and a 60mm stem?

Sent from my Moto G Play using Tapatalk

 

[stirk]

Riser bars ≈30mm and a 60mm stem?

Sent from my Moto G Play using Tapatalk

Stop being so logical, it ruins the discussion.

 

[Nautonier]

Riser bars ≈30mm and a 60mm stem?

Sent from my Moto G Play using Tapatalk

I don't want the cockpit higher, I want it longer. Have tried longer stems and really don't like them for the kind of riding I do on this bike. 40mm seems to be the sweet spot for stem length.

 

[Knuckles]

I don't want the cockpit higher, I want it longer. Have tried longer stems and really don't like them for the kind of riding I do on this bike. 40mm seems to be the sweet spot for stem length.

Close thread.

Next....

 

[agentninety3]

Assuming the wheel axles remain the same height off the ground you can draw a right triangle between the axles and the point in the head tube where the head angle is calculated. The wheelbase is the hypotenuse of that triangle. Then the head angle is the same as the angle that the fork makes with the line between the two axles. Regardless off the point in the head tube where the angle is taken, we know the length of the fork to that point doesn't change, so the maths are as follows:

Fork Length = Wheelbase / cos(Head Angle)

WB0 / cos (HA0) = WB1 / cos (HA1)

WB1 = WB0 * cos(HA1) / cos (HA0)

WB1 = 1184 * cos (65) / cos (65.6)

WB1 = 1211.26 mm

 

[No Skid Marks]

Will depend on rear axle path/ suspension design a tad.
you could run a Reece adjust headset to lengthen cockpit/reach.
or Angleset to slacken or combine both if you had 1.5 headtube and straight steerer.
are you running external cupheadset or zero stack.

 

[Nautonier]

Assuming the wheel axles remain the same height off the ground you can draw a right triangle between the axles and the point in the head tube where the head angle is calculated. The wheelbase is the hypotenuse of that triangle. Then the head angle is the same as the angle that the fork makes with the line between the two axles. Regardless off the point in the head tube where the angle is taken, we know the length of the fork to that point doesn't change, so the maths are as follows:

Fork Length = Wheelbase / cos(Head Angle)

WB0 / cos (HA0) = WB1 / cos (HA1)

WB1 = WB0 * cos(HA1) / cos (HA0)

WB1 = 1184 * cos (65) / cos (65.6)

WB1 = 1211.26 mm

Good work, you obviously paid more attention in maths than I did. I'm putting the bike back together soon, so will measure it and confirm your findings.

 

[Nautonier]

Will depend on rear axle path/ suspension design a tad.
you could run a Reece adjust headset to lengthen cockpit/reach.
or Angleset to slacken or combine both if you had 1.5 headtube and straight steerer.
are you running external cupheadset or zero stack.

I've not heard of a reach adjusting headset - I imagine it's offset top and bottom to bring the steerer tube forward or aft by a few mm. Not an option for me I'm afraid with tapered steerer. Do you know what the maximum increase in reach is that could be achieved by this system?

 

[agentninety3]

Good work, you obviously paid more attention in maths than I did. I'm putting the bike back together soon, so will measure it and confirm your findings.

Yeah, I've just realised that was wrong though. Looking at a geo chart you can't assume there is a right angle made between the distance between the rear axle to the top of head tube, and the top of head tube to front axle. The point where you can make a right angle is off in space somewhere, which means to maintain the right angle the length from that point to the front axle will probably change when you change the head angle. This means the adjacent side isn't a constant, thus you can't use the simple trig calculation above.

It'll be in the ball park, but given the angles of a bike there's a lot of unknowns at the moment to make the exact calculation.

 

[Nautonier]

Yeah, I've just realised that was wrong though. Looking at a geo chart you can't assume there is a right angle made between the distance between the rear axle to the top of head tube, and the top of head tube to front axle. The point where you can make a right angle is off in space somewhere, which means to maintain the right angle the length from that point to the front axle will probably change when you change the head angle. This means the adjacent side isn't a constant, thus you can't use the simple trig calculation above.

It'll be in the ball park, but given the angles of a bike there's a lot of unknowns at the moment to make the exact calculation.

I was hoping you were right, but having measured it, which isn't an exact process by any means, it came in at ~1185, which is unexpected. Surely with the offset bushings installed it would gain more than 1mm in wheel base? Maybe it was actually less than 1184 to start with, I'm just going off the geo chart.

 

[The Duckmeister]

Assuming the wheel axles remain the same height off the ground....

They will be unless he changes wheel size - axle height from ground is directly and entirely related to wheel radius and nothing else.

 

[No Skid Marks]

I've not heard of a reach adjusting headset - I imagine it's offset top and bottom to bring the steerer tube forward or aft by a few mm. Not an option for me I'm afraid with tapered steerer. Do you know what the maximum increase in reach is that could be achieved by this system?

Depends on headtube diameter but you'd need straight 1 1/8th steerer. Up to 7mm reach adjust.

 

[stirk]

I think it's time to stop measuring in mm and buy a new bike!!

 

[schred]

They will be unless he changes wheel size - axle height from ground is directly and entirely related to wheel radius and nothing else.

what's a wheel made up of? Are the f & r axles necessarily the same height? Come on d-man!