Fork rake and trail again..

[tuscanyswe]

So im going over the final bits on a frame before its beeing built.

My tommasini has a low trail number. The tommasini is a bike i have and love to ride. It has a headtube angle of 73.75 which is quite steap and a fork rake of 48 rendering a trail of 49mm on a set of 25ish mm tires.


The new bike fork comes in at 50mm rake (this number seem to be a fixed number from what i have understood). So if i spec my headtube angle slightly shallower at 73.5 i get very similar trail numbers of 49mm with the same tires.

Now i realize these changes are very small and are likely not enough to perhaps even make a noticable difference to even a picky person that knew what he or she was looking for. Either way what would in theory be a difference between the slightly shallower hta and a bit more rake vs the slightly steaper hta with less rake be if any since the same trail.

They both arrive at a trail of around 49mm which would be considered low. I dont ride hills i ride traffic.. So for me i always enjoyed the fast steering. What do you feel about your low trail bike?

[thirdgenbird]

I think your “again” is in reference to my thread praising a higher trail bike. Coincidentally, my other bike is a Tommasini with much faster steering.

While I prefer the longer trail bike with fatter tires for daily riding, I enjoy the contrast of also owning a lower trail bike on narrow tires.

[tuscanyswe]

I think your “again” is in reference to my thread praising a higher trail bike. Coincidentally, my other bike is a Tommasini with much faster steering.

While I prefer the longer trail bike with fatter tires for daily riding, I enjoy the contrast of also owning a lower trail bike on narrow tires.

Hey

No the "again" was more a reference to that i think its beeing discusses every now and again. I think i missed your thread actually, i shall revisit, but i thank you for sharing yr thoughts just the same.

[ColonelJLloyd]

Because there are so many variables at play it makes good sense that how a particular trail value feels depends on the way it is achieved. Meaning that a bike with a 73 degree HTA, 50mm offset fork, and 25mm tires with 49mm trail could feel pretty different from a bike with 71 degree HTA, 62mm offset fork, and 25mm tires with 49mm trail.

But I've never done proper A/B testing or anything.

[tuscanyswe]

Because there are so many variables at play it makes good sense that how a particular trail value feels depends on the way it is achieved. Meaning that a bike with a 73 degree HTA, 50mm offset fork, and 25mm tires with 49mm trail could feel pretty different from a bike with 71 degree HTA, 62mm offset fork, and 25mm tires with 49mm trail.

But I've never done proper A/B testing or anything.

Yes that would make sense and is also why im asking. Tho in my example the difference is so small so any difference would likely only be theoretical.

[ColonelJLloyd]

Yes that would sense and is also why im asking. Tho in my example the difference is so small so any difference would likely only be theoretical.

I meant to say this in my response. It's such a subtle difference that I would not imagine you could discern which is which with all the rest going on in a bike/rider relationship.

[Mark McM]

A change of 0.25 degrees in the head tube is quite small. As you say, this will only cause a small difference in handling (even if the fork offset was the same). But the fork offset has also been lengthened, which compensates slightly for the difference, so the difference in handling will be smaller yet. Which is not to say that the bikes will feel the same - there are likely many other differences between the frames (particularly in tube sizes and stiffness and also BB height) which will probably have a bigger effect on ride feel.

But, if all else is equal, the shallower head angle will lengthen the wheelbase (shiftring the front/rear weight distribution slightly back), and there will be slightly more steering "flop" (the tendency for the fork/front wheel to want to turn in the direction the bike is leaned). The shallower angle and greater fork offset would also slightly increase the vertical flex in the fork. For such a small change in angle, all of these effects will be quite small. You might notice a slight difference if you immediately jumped off one bike and on to the other, but I'm sure the sense of feeling "different" would disappear after only a short distance of riding. And, as noted above, there are likely to be other differences in the bike whose effect on the ride swamps the effect of the slightly shallower head tube.

[Peter P.]

What do you feel about your low trail bike?

It sucked.

Leaning into corners at any speed, it felt like the front wheel was going to wash out on me.

[xnetter]

Around 50mm geometric trail is on the cusp between "low" and "mid". I find low-trail bikes handle best with wider tires to help control and complement the increased steering sensitivity. Personally, I would not want a skinny-tired bike with <55mm trail.

KJ

[tuscanyswe]

I guess the number of opinons thus far is not close enough to make any statistics on but its interesting that so far of those who wanted to share there is not a lot of ppl who seem to think its the casts meow that i do.

Thanks for sharing yr explanations and experiences.

[Mark McM]

I guess the number of opinons thus far is not close enough to make any statistics on but its interesting that so far of those who wanted to share there is not a lot of ppl who seem to think its the casts meow that i do.

I personally prefer the trail to be on the lower side. I'd describe the differences in feel of high and low trail bikes like this: High trail bikes know where they want to go, and will reliably go in that direction - but if I want to go in a different direction, I have to fight the steering geometry to make it go where I want it to go. Low trail bikes don't seem to know where they want to go, and left to their own devices may go in unpredictable directions - but a lighter touch is requred to change direction, and since I know how to direct a bike, it is easier to make them go where I want them to go.

[tuscanyswe]

I personally prefer the trail to be on the lower side. I'd describe the differences in feel of high and low trail bikes like this: High trail bikes know where they want to go, and will reliably go in that direction - but if I want to go in a different direction, I have to fight the steering geometry to make it go where I want it to go. Low trail bikes don't seem to know where they want to go, and left to their own devices may go in unpredictable directions - but a lighter touch is requred to change direction, and since I know how to direct a bike, it is easier to make them go where I want them to go.

Thats a good description of my perception as well. I agree.

[unterhausen]

I have wondered if the handling of a bike with a steep head angle and less rake is the same as a bike with a slack head angle and enough rake to make the trail the same between the two.

It stands to reason that they would be different.

Of course, if you use a rando front bag, the bike with larger rake will handle better, which the main reason I go with low trail. And I hate flop.

[David Tollefson]

So many other variables here:
* Front-center differences.
* Percentage of overall bike+rider weight that rests on the front wheel (also affected by the above).
* Whether you have a front load or not (affecting the above).
* Whether that load is tied to the fork or the frame (affecting "flop" and ease of making steering corrections).

There can be some generalizations made about how a certain characteristic will affect handling, given all other factors being equal, but the truth is that you can't just change one aspect on a bike and keep all the others equal.

[tuscanyswe]

So many other variables here:
* Front-center differences.
* Percentage of overall bike+rider weight that rests on the front wheel (also affected by the above).
* Whether you have a front load or not (affecting the above).
* Whether that load is tied to the fork or the frame (affecting "flop" and ease of making steering corrections).

There can be some generalizations made about how a certain characteristic will affect handling, given all other factors being equal, but the truth is that you can't just change one aspect on a bike and keep all the others equal.

Well these are 2 racebikes that will have all other measurements identical. Other than the difference in hta and fork rake so you can at least come very close to having most other parameters the same.