Mechanics Quick Question Thread [Ask Questions Here]

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Mechanics Quick Question Thread [Ask Questions Here]
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flag paulmtbb
Posted: Mar 27, 2024 at 12:47 Quote
ShawMac wrote:
I would assume 52mm for 29. DH bikes have slacker HTA which increases trail so the larger offset reduces that. Larger trail is slower steering response so the smaller 44mm will have slower steering response.

Single crown 29 forks used to be commonly 52 as well, then 48/44 started getting added. I switched from 52 to 44 on my trail bike and I didn't notice a lot of difference.
But what is more common.
flag freestyIAM
Posted: Mar 27, 2024 at 14:23 Quote
paulmtbb wrote:
ShawMac wrote:
I would assume 52mm for 29. DH bikes have slacker HTA which increases trail so the larger offset reduces that. Larger trail is slower steering response so the smaller 44mm will have slower steering response.

Single crown 29 forks used to be commonly 52 as well, then 48/44 started getting added. I switched from 52 to 44 on my trail bike and I didn't notice a lot of difference.
But what is more common.

52mm is the most common of offset for 29in DH forks
flag paulmtbb
Posted: Mar 27, 2024 at 14:35 Quote
freestyIAM wrote:
paulmtbb wrote:
ShawMac wrote:
I would assume 52mm for 29. DH bikes have slacker HTA which increases trail so the larger offset reduces that. Larger trail is slower steering response so the smaller 44mm will have slower steering response.

Single crown 29 forks used to be commonly 52 as well, then 48/44 started getting added. I switched from 52 to 44 on my trail bike and I didn't notice a lot of difference.
But what is more common.

52mm is the most common of offset for 29in DH forks
Prefect! Thank you! Is there any reason for an older standard is common on DH bikes?
flag ShawMac
O+
Posted: Mar 27, 2024 at 14:51 Quote
paulmtbb wrote:
freestyIAM wrote:
paulmtbb wrote:
But what is more common.

52mm is the most common of offset for 29in DH forks
Prefect! Thank you! Is there any reason for an older standard is common on DH bikes?

Things are slower to change with DH bikes because the geo has been really slack already through time, so there isn't a desire to make them steer any slower.
flag ethanrevitch
Posted: Mar 27, 2024 at 22:24 Quote
ShawMac wrote:
paulmtbb wrote:
freestyIAM wrote:


52mm is the most common of offset for 29in DH forks
Prefect! Thank you! Is there any reason for an older standard is common on DH bikes?

Things are slower to change with DH bikes because the geo has been really slack already through time, so there isn't a desire to make them steer any slower.
True, but wouldn't decreasing the offset make it steer faster?
flag scotteh
O+
Posted: Mar 27, 2024 at 23:06 Quote
ethanrevitch wrote:
True, but wouldn't decreasing the offset make it steer faster?
No - reducing offset increases trail, and more trail = slower steering.
flag aegiz
Posted: Mar 28, 2024 at 12:01 Quote
shorter offsets (yielding a longer trail) can however increase stability. so if you're chasing that characteristic and are comfortable with slower steering, it's something to be mindful of!
flag ethanrevitch
Posted: Mar 28, 2024 at 12:15 Quote
aegiz wrote:
shorter offsets (yielding a longer trail) can however increase stability. so if you're chasing that characteristic and are comfortable with slower steering, it's something to be mindful of!
What do you mean by long trail? Do you mean longer wheelbase bikes?
flag scotteh
O+
Posted: Mar 28, 2024 at 12:17 Quote
Trail is a geometry figure - read this to understand: https://bikeinsights.com/cyclopedia/trail

It's kind of counterintuitive, but increasing trail by reducing offset actually reduces wheelbase as well. So those two things are actually working in opposite. For example, if you reduce offset to increase trail and slow down handling, you're actually getting a slightly shorter wheelbase, which speeds up handling (albeit in a slightly difference way).

In my experience, the increased stability from from reducing offset is more noticeable than the loss in stability from the very slight reduction in wheelbase though.
flag aegiz
Posted: Mar 28, 2024 at 12:20 Quote
ethanrevitch wrote:
aegiz wrote:
shorter offsets (yielding a longer trail) can however increase stability. so if you're chasing that characteristic and are comfortable with slower steering, it's something to be mindful of!
What do you mean by long trail? Do you mean longer wheelbase bikes?

the wheelbase gets reduced with shorter offset, but trail's characteristic (longer in this case) aids in keeping the wheel straight.

which translates to, loosely, "stability".
flag barp
Posted: Mar 28, 2024 at 12:26 Quote
To further spell it out, trail is what gives the front wheel "caster effect", whereby the contact patch being behind the axis of steering allows a turned fork to be pulled straight by tire traction.
flag aegiz
Posted: Mar 28, 2024 at 12:46 Quote
scotteh wrote:
Trail is a geometry figure - read this to understand: https://bikeinsights.com/cyclopedia/trail

It's kind of counterintuitive, but increasing trail by reducing offset actually reduces wheelbase as well. So those two things are actually working in opposite. For example, if you reduce offset to increase trail and slow down handling, you're actually getting a slightly shorter wheelbase, which speeds up handling (albeit in a slightly difference way).

In my experience, the increased stability from from reducing offset is more noticeable than the loss in stability from the very slight reduction in wheelbase though.

agreed!
flag ethanrevitch
Posted: Mar 28, 2024 at 17:09 Quote
scotteh wrote:
Trail is a geometry figure - read this to understand: https://bikeinsights.com/cyclopedia/trail

It's kind of counterintuitive, but increasing trail by reducing offset actually reduces wheelbase as well. So those two things are actually working in opposite. For example, if you reduce offset to increase trail and slow down handling, you're actually getting a slightly shorter wheelbase, which speeds up handling (albeit in a slightly difference way).

In my experience, the increased stability from from reducing offset is more noticeable than the loss in stability from the very slight reduction in wheelbase though.
Haha I think we are thinking the same thing but saying it in different way.

 


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