Viewing 6 posts - 1 through 6 (of 6 total)
  • Oh dear, I’m asking a geometry question – rake
  • PJay
    Free Member

    Firstly I guess that I’d better lay out my credentials; I have none! I can’t manual, wheelie, bunny hop or do anything remotely fast and clever on my bike. I pootle about on country roads and bridleways (quite a bit) and am probably also very over biked on a Singular Swift which breaks the 28lb barrier (although in fairness it’s about the same as an off the peg Vagabond); I ride alone and don’t chase people, so I’m fine (and I keep telling myself that I’d like to do some more off-road).

    Geometry’s a bit of a mystery and I’ve tended to buy large frames and tweak the bars, stem and seatpost until it feels about right – it’s kind of worked.

    I’ve been riding a MRP Rock Solid carbon/aluminium fork (465mm a-c) and have just swapped them out to try a set of steel Singular Swift forks (470mm a-c).

    My first ride out (a regular loop) felt a bit of a slog and sluggish. To be fair there are loads of variables, it was windy, I might not of been on form, I’m not in the best place mentally and I was having issues with my brakes which drew my attention; the Swift forks will add 200-300g of weight over the Rock Solids but whether that would be noticable I don’t know (my rucksack contains a D-lock, inner tube, assorted tools, mobile phone, bottle of drink and assorted bobbins and probably weight more on its own than some people’s bikes so it’s not a massive increase overall).

    I decided that I need to drop the bars slightly but something that might be worthy of note is the rake. The Rock Solid has a rake of 44mm whilst the Swifts are 55mm giving them 11mm more rack; I’ve not idea if this is significant but wondered whether it might be (folk tend to talk about a few mm here and a degree of two there as being important).

    As a luddite, would I notice 11mm extra rake and, if so, in what way? If I don’t get on with the Swift forks I can always swap back, but they do look lovely and deserve a good deal more of a try out before I make a decision.

    riklegge
    Full Member

    Increased rake (or offset) reduces the “trail” measurement (this is the horizontal measurement from the tyre contact patch to the centerline of the steering axis). The longer the trail measurement, the slower the steering.

    Will you notice a difference? To be honest, your ride mentioned above contained an awful lot of variables, and I would say that being tired and it being windy probably contributed more than the difference in the fork.

    geex
    Free Member

    TL:DR (skim read)

    It’ll be fine
    you’ll just get used to any change in handling

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    cromolyolly
    Free Member

    Slackening your head angle increases trail and increasing your offset decreases trail

    So your slighlty longer fork offsets (no pun intended) your increased offset, increases stack and reduces reach. You’d need to CAD it or similar (there are online ones specifically for bikes if you want to know your exact numbers. My guesstimate is you’ve actually decreased the trail by half the offset of the forks.
    So much else going on (Tyre pressures, relatively small increase in fork weight, ground conditions, wind, what you had for breakfast, how many pints the night before, whether Jupiter was ascending or descending) that I’d give it a few more rides on different stuff before tinkering

    kerley
    Free Member

    you’ll just get used to any change in handling

    Agree. I changed from a 30 to a 43 on my track bike and the steering was slightly less stable but not enough to worry about and after 20 minutes had forgotten all about it. The extra weight would be more a worry for me as I care too much about bike weight!

    rickon
    Free Member

    44mm to 55mm offset change would be immediately noticeable to me, switching between the 44mm and 51mm 29er forks I have is obvious for me.

    However, the 55s should feel quicker handling, and the 44s slower. So it’s not that making your bike feel more sluggish for sure.

    Likely just an off day on the bike.

Viewing 6 posts - 1 through 6 (of 6 total)

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