What does changing fork rate alter?

[The Spider]

going from 44 degrees to 45 degrees...alters the handling how?

and is a single degree in fork rake able to be detected? (i think it's going to have some effect...)

Much appreciated.

[dirtdigger88]

smiley corrected me- I dont know what it would do but I am guessing not much

Jason

[TimD]

FWIW, I could definitely tell a difference between 43mm and 45mm rake forks on my 61cm Marcelo. As for a 1mm difference, who knows? YMMV.

TimD

[Smiley]

Digger , if you in theory add to the rake with a fixed head angle , you speed up the front handling . The opposite is true . Keep the fork span in mind cause if your new fork is taller , you raise the front end , changing the head angle slightly ahd yes counter what you just did with the rake . In the end you probably won't notice a thing for this question asked .

[tch]

...mm rake fork. The 43 was really the wrong spec for my geometry and going to a fork with greater rake really helped. I moved my trail from 6.6 to 5.9 (speeding up response), moved the front wheel out further in front of me (getting rid of the "riding on top of the front wheel" feel), eliminated a wierd front wheel "flop" while climbing standing, and generally stretched the wheelbase out.

It was really the right move. That said, I think the change is reasonably subtle and not hugely dramatic for a guy who rides 100-150 miles a week. Change one degree? You'll never notice it.

[Dave]

Fork offset is a linear measurement not an angular one, so it's measured in millimeters not degrees.

Offset (rake) is the perpendicular distance between two parallel lines, one through the center of the hub, and one through the center of the steering tube. Trail is the horizontal distance between the tire contact point and a line through the steering axis. The more trail, the more stable the bike (slower steering). The less trail, the quicker the steering. Both fork offest and head tube angle affect the amount of trail. Steepening the head tube angle or increasing rake will decrease trail, reducing stability and quickening the steering. The formula for trail is as follows, where R is the tire radius, and H is the head tube angle. Trail = (R/ tan H) – (rake/sin H). As an example if R = 33.65cm, H=73, and rake is 4.0cm, trail = 33.65/tan73 – 4.0/sin73. This calculates to 6.1cm.

Changing the rake from 4.0 to 4.5cm yields a trail of 5.58cm.
Changing the head tube angle to 74 degrees, with the 4.0 rake yields a trail of 5.49cm or 2.16 inches. Thus, a .5cm increase in rake will have a similar effect to increasing the head tube angle by slightly less than one degree.

Bottom line, 1mm is a very small amout that won't be noticed, IF the fork is the same length. As others mentioned, all forks are not the same length. Common lengths range from 365 to 374mm. This range can alter the head tube angle by about .5 degree. It's entirely possible to buy a fork that has more offset that is also longer and make no change to the trail at all.

[The Spider]

Thank you all....

I just checked My Columbus fork with 371mm and 45mm which I'd like to swap with a THM Scapula at 371 / 44. So it's not going to change a thing (well not noticable anyway)....this is on my Parlee.

Oh, I'm measuring from crown race to centre of drop out / quick release axle...

Can someone measure a Reynolds Ouzo Pro for me for length (or know where I can get that detail...I've checked website/brochure) that way I can see if I can use my muscle fork on a pegoretti Marcelo (when I get one!).

Thanks again everyone, great stuff, much appreciated.

[Brian Smith]

Thank you all....

I just checked My Columbus fork with 371mm and 45mm which I'd like to swap with a THM Scapula at 371 / 44. So it's not going to change a thing (well not noticable anyway)....this is on my Parlee.

Oh, I'm measuring from crown race to centre of drop out / quick release axle...

Can someone measure a Reynolds Ouzo Pro for me for length (or know where I can get that detail...I've checked website/brochure) that way I can see if I can use my muscle fork on a pegoretti Marcelo (when I get one!).

Thanks again everyone, great stuff, much appreciated.


How did you check the 44mm and 45mm?
I ask because it is usually considered challenging, even at a bike shop level, to take these measurements reliably.
If these measurements are just what are printed on the spec sheets or boxes, I would submit that the errors with respect to their specifications could be much greater than the difference in measurements of their theoretical specifications.
We use 37.0cm as the design specification for an Ouzo Pro.
I agree with the others that 1mm in offset is a negligable difference, and would further opine that 1mm of length is also a negligable difference.

If you are taking these measurements from the crown race seat to the outside surface of the dropout near the skewer, then your measurement may be up to 3mm different from the design specification from the center of the steerer at the crown race seat to the senter of the hub axle between the dropouts. Notice that the measurement error there, too, is greater than the submitted design difference.

You'll probably be fine, and the nice part is that you can simply remove it if it is not to your liking.
have fun!

[The Spider]

the rakes I got off the internet (THM, Columbus and Ouzo - well I know which rake the Marcelo comes with) the measurement for THM was off the site, whilst I measured the Muscle fork myself - therefore flawed!)

I will say how disappointing it is that most sites don't list the dimensions of their forks except one - weight!

That being said THM is German and they list EVERYTHING! Precision engineering and Germany, who would have thought (large amount of sarcasm in that line).