FORK OFFSET

[Vanquisher]

Is the relationship between fork offset and wheelbase direct ??

So that if you put a Fork on that has say, a -5mm less offset than the fork the bike manufacturer puts on the bike, then you just reduce the wheelbase by 5mm from the manufacturers stated Geo chart??

I guess reducing offset steepens head angle as well?? Raises the BB ??

Or have I misunderstood the whole Fork Offset gig ??

 

[RoJo]

It will reduce wheelbase by approx 5 * sin(HA) = 4.5mm (offset is distance from steering axis to axle).
It will have no significanct effect on head angle or BB height.

Essentially reducing offset has two effects:
1) Reduce wheelbase.
2) Increase trail, this is the distance between your tyre contact patch and where the steering axis intersects with the ground. Increasing trail (= reducing offset) has a stabilising effect on your steering (think about the wheels on a supermarket trolley wanting to self centre as you push it forward, if they had no trail they wouldn't do this).

Whether this is good or bad will depend on your baseline balance. From literature searches I think that:
- If your bike is already long, then the improvement in steering stability and ability to weight the front more from shortening the bike might benefit overall balance.
- If your bike is too short, making it shorter might have more of a detrimental effect than any improvements you make to steering stability.

 

[Vanquisher]

It will reduce wheelbase by approx 5 * sin(HA) = 4.5mm (offset is distance from steering axis to axle).
It will have no significanct effect on head angle or BB height.

Essentially reducing offset has two effects:
1) Reduce wheelbase.
2) Increase trail, this is the distance between your tyre contact patch and where the steering axis intersects with the ground. Increasing trail (= reducing offset) has a stabilising effect on your steering (think about the wheels on a supermarket trolley wanting to self centre as you push it forward, if they had no trail they wouldn't do this).

Whether this is good or bad will depend on your baseline balance. From literature searches I think that:
- If your bike is already long, then the improvement in steering stability and ability to weight the front more from shortening the bike might benefit overall balance.
- If your bike is too short, making it shorter might have more of a detrimental effect than any improvements you make to steering stability.

That is absolutely epic thanks. Exactly what I needed to know for my sizing choice and build considerations

 

[TommyC]

I’m building a nukeproof hard tail. The RS version comes with 150mm forks with a 44mm offset. I’m looking to put 160mm on it and some I’m looking at have a 37mm offset. Am I right in thinking this reduced offset will only counteract the effects of the longer fork on the wheelbase?